feat(terminal): port page memory model (partial PageList)

First cut of the terminal core memory model from ZIG/src/terminal:
size, point, style, hyperlink, ref_counted_set, page and PageList.

Design (see docs/rewrite/ARCHITECTURE.md decisions 2-4):
- Cell/Row are 8-byte u64 wrappers with Zig's exact bit offsets.
- Page owns row/cell Vecs plus style set, grapheme and hyperlink maps;
  Page::layout reproduces Ghostty's byte-size formula on 64-bit Linux so
  scrollback-limit pruning matches.
- PageList keeps nodes in a generation-checked slab with a free list and
  list-owned tracked pins addressed by handles.

This is explicitly partial (docs/rewrite/notes/ghostty-terminal-
pagelist.md): 151/202 PageList tests ported; reflow rebuilds a snapshot
instead of Zig's incremental ReflowCursor; point<->pin conversion walks
from the list head (no active/viewport caches); RefCountedSet doesn't
reproduce probe-dependent ID reuse. A follow-up pass finishes parity.

Test Plan:
- cargo test -p ghostty-terminal (239 tests)

crates/ghostty-terminal/src/hyperlink.rs

@@ -0,0 +1,43 @@
+//! Owned OSC 8 hyperlinks and per-page identifiers.
+/// Nonzero page-local hyperlink identifier.
+pub type Id = u16;
+/// Mapping from a cell index to its hyperlink.
+pub type Map = std::collections::HashMap<usize, Id>;
+/// An explicit OSC 8 ID or an automatically generated screen-local ID.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum HyperlinkId {
+    /// Application-provided byte string.
+    Explicit(Vec<u8>),
+    /// Screen-generated identifier.
+    Implicit(u32),
+}
+/// A decoded hyperlink owning its ID and URI.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Hyperlink {
+    /// Hyperlink identity.
+    pub id: HyperlinkId,
+    /// URI bytes, which need not be UTF-8.
+    pub uri: Vec<u8>,
+}
+impl Hyperlink {
+    /// Duplicate the owned strings.
+    pub fn dupe(&self) -> Self {
+        self.clone()
+    }
+    /// Compare identity and URI.
+    pub fn eql(&self, other: &Self) -> bool {
+        self == other
+    }
+    /// Logical string allocation including 32-byte chunk rounding.
+    pub fn string_bytes(&self) -> usize {
+        self.uri.len().next_multiple_of(32)
+            + match &self.id {
+                HyperlinkId::Explicit(v) => v.len().next_multiple_of(32),
+                HyperlinkId::Implicit(_) => 0,
+            }
+    }
+}
+/// Owned page entry; unlike Zig it needs no base address for decoding.
+pub type PageEntry = Hyperlink;
+/// Reference-counted set of page entries.
+pub type Set = crate::ref_counted_set::RefCountedSet<PageEntry>;

crates/ghostty-terminal/src/lib.rs

@@ -1 +1,9 @@
-//! ghostty-terminal: see docs/rewrite/ARCHITECTURE.md for the module map.
+//! Safe page-based terminal memory model.
+#![cfg_attr(test, allow(clippy::unwrap_used))]
+pub mod hyperlink;
+pub mod page;
+pub mod page_list;
+pub mod point;
+pub mod ref_counted_set;
+pub mod size;
+pub mod style;

crates/ghostty-terminal/src/page.rs

@@ -0,0 +1,2216 @@
+//! Compact cells and rows, with bounded owned page storage.
+use crate::{
+    hyperlink::{self, Hyperlink, HyperlinkId},
+    ref_counted_set::{AddError, Layout as SetLayout},
+    style::{self, Style},
+};
+use ghostty_vt::color::Rgb;
+use std::collections::{HashMap, HashSet};
+/// Default grapheme allocation request, in bytes.
+pub const GRAPHEME_BYTES_DEFAULT: u32 = 1024;
+/// Default string allocation request, in bytes.
+pub const STRING_BYTES_DEFAULT: u32 = 2048;
+/// Reference ABI size of a hyperlink set item.
+pub const HYPERLINK_ITEM_SIZE: usize = 48;
+/// Reference ABI size of a style set item.
+pub const STYLE_ITEM_SIZE: usize = 36;
+/// The standard page capacity (smaller grapheme region in tests, as in Zig).
+pub const STD_CAPACITY: Capacity = Capacity {
+    cols: 215,
+    rows: 215,
+    styles: 128,
+    hyperlink_bytes: 192,
+    grapheme_bytes: if cfg!(test) { 512 } else { 8192 },
+    string_bytes: STRING_BYTES_DEFAULT,
+};
+/// ContentTag field of the packed grid representation.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
+#[repr(u8)]
+pub enum ContentTag {
+    /// Single codepoint.
+    #[default]
+    Codepoint = 0,
+    /// First codepoint of a grapheme cluster.
+    CodepointGrapheme = 1,
+    /// Background-only palette color.
+    BgColorPalette = 2,
+    /// Background-only RGB color.
+    BgColorRgb = 3,
+}
+/// Wide field of the packed grid representation.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
+#[repr(u8)]
+pub enum Wide {
+    /// Single grid cell.
+    #[default]
+    Narrow = 0,
+    /// Two-cell character.
+    Wide = 1,
+    /// Trailing half of a wide character.
+    SpacerTail = 2,
+    /// End-of-line spacer before a wrapped wide character.
+    SpacerHead = 3,
+}
+/// SemanticContent field of the packed grid representation.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
+#[repr(u8)]
+pub enum SemanticContent {
+    /// Ordinary command output.
+    #[default]
+    Output = 0,
+    /// User input.
+    Input = 1,
+    /// Application prompt.
+    Prompt = 2,
+}
+/// SemanticPrompt field of the packed grid representation.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
+#[repr(u8)]
+pub enum SemanticPrompt {
+    /// No prompt cells.
+    #[default]
+    None = 0,
+    /// Primary prompt row.
+    Prompt = 1,
+    /// Continuation prompt row.
+    PromptContinuation = 2,
+}
+/// Eight-byte terminal cell; all-zero bits describe an empty cell.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
+#[repr(transparent)]
+pub struct Cell(u64);
+impl Cell {
+    /// Construct an unstyled single-codepoint cell.
+    pub fn init(cp: u32) -> Self {
+        let mut c = Self::default();
+        c.set_codepoint(cp);
+        c
+    }
+    fn bits(self, shift: u32, mask: u64) -> u64 {
+        (self.0 >> shift) & mask
+    }
+    fn set_bits(&mut self, shift: u32, mask: u64, value: u64) {
+        self.0 = (self.0 & !(mask << shift)) | ((value & mask) << shift);
+    }
+    /// Return the bit-packed representation.
+    pub const fn raw(self) -> u64 {
+        self.0
+    }
+    /// True when every bit is zero.
+    pub fn is_zero(self) -> bool {
+        self.0 == 0
+    }
+    /// Return the codepoint, or zero for background-only cells.
+    pub fn codepoint(self) -> u32 {
+        if (self.content_tag() as u8) < 2 {
+            self.bits(2, 0x1fffff) as u32
+        } else {
+            0
+        }
+    }
+    /// Set the codepoint payload without changing the content tag.
+    pub fn set_codepoint(&mut self, cp: u32) {
+        self.set_bits(2, 0xffffff, u64::from(cp & 0x1fffff));
+    }
+    /// Return the palette payload.
+    pub fn color_palette(self) -> u8 {
+        self.bits(2, 255) as u8
+    }
+    /// Set the palette payload without changing the content tag.
+    pub fn set_color_palette(&mut self, v: u8) {
+        self.set_bits(2, 0xffffff, u64::from(v));
+    }
+    /// Return the RGB payload.
+    pub fn color_rgb(self) -> Rgb {
+        Rgb {
+            r: self.bits(2, 255) as u8,
+            g: self.bits(10, 255) as u8,
+            b: self.bits(18, 255) as u8,
+        }
+    }
+    /// Set the RGB payload without changing the content tag.
+    pub fn set_color_rgb(&mut self, v: Rgb) {
+        self.set_bits(
+            2,
+            0xffffff,
+            u64::from(v.r) | (u64::from(v.g) << 8) | (u64::from(v.b) << 16),
+        );
+    }
+    /// True when the cell contains a nonzero text codepoint.
+    pub fn has_text(self) -> bool {
+        self.codepoint() != 0
+    }
+    /// True when the cell refers to extra grapheme codepoints.
+    pub fn has_grapheme(self) -> bool {
+        self.content_tag() == ContentTag::CodepointGrapheme
+    }
+    /// Width in grid cells, including one-cell spacers.
+    pub fn grid_width(self) -> u8 {
+        if self.wide() == Wide::Wide { 2 } else { 1 }
+    }
+    /// True when the cell has a nondefault style ID.
+    pub fn has_styling(self) -> bool {
+        self.style_id() != 0
+    }
+    /// True for a blank narrow textual cell; style does not affect this test.
+    pub fn is_empty(self) -> bool {
+        (self.content_tag() as u8) < 2 && !self.has_text() && self.wide() == Wide::Narrow
+    }
+    /// True if any cell has text.
+    pub fn has_text_any(cells: &[Self]) -> bool {
+        cells.iter().any(|c| c.has_text())
+    }
+    /// Read the content_tag field.
+    pub fn content_tag(self) -> ContentTag {
+        match self.bits(0, 3) {
+            0 => ContentTag::Codepoint,
+            1 => ContentTag::CodepointGrapheme,
+            2 => ContentTag::BgColorPalette,
+            _ => ContentTag::BgColorRgb,
+        }
+    }
+    /// Update the content_tag field.
+    pub fn set_content_tag(&mut self, v: ContentTag) {
+        self.set_bits(0, 3, v as u64);
+    }
+    /// Read the style_id field.
+    pub fn style_id(self) -> u16 {
+        self.bits(26, 65535) as u16
+    }
+    /// Update the style_id field.
+    pub fn set_style_id(&mut self, v: u16) {
+        self.set_bits(26, 65535, v as u64);
+    }
+    /// Read the wide field.
+    pub fn wide(self) -> Wide {
+        match self.bits(42, 3) {
+            0 => Wide::Narrow,
+            1 => Wide::Wide,
+            2 => Wide::SpacerTail,
+            _ => Wide::SpacerHead,
+        }
+    }
+    /// Update the wide field.
+    pub fn set_wide(&mut self, v: Wide) {
+        self.set_bits(42, 3, v as u64);
+    }
+    /// Read the protected field.
+    pub fn protected(self) -> bool {
+        self.bits(44, 1) != 0
+    }
+    /// Update the protected field.
+    pub fn set_protected(&mut self, v: bool) {
+        self.set_bits(44, 1, v as u64);
+    }
+    /// Read the hyperlink field.
+    pub fn hyperlink(self) -> bool {
+        self.bits(45, 1) != 0
+    }
+    /// Update the hyperlink field.
+    pub fn set_hyperlink(&mut self, v: bool) {
+        self.set_bits(45, 1, v as u64);
+    }
+    /// Read the semantic_content field.
+    pub fn semantic_content(self) -> SemanticContent {
+        match self.bits(46, 3) {
+            0 => SemanticContent::Output,
+            1 => SemanticContent::Input,
+            _ => SemanticContent::Prompt,
+        }
+    }
+    /// Update the semantic_content field.
+    pub fn set_semantic_content(&mut self, v: SemanticContent) {
+        self.set_bits(46, 3, v as u64);
+    }
+}
+/// Eight-byte row metadata. The low 32 bits hold its first cell index.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
+#[repr(transparent)]
+pub struct Row(u64);
+impl Row {
+    /// First cell index in the page's row-major storage.
+    pub fn cells(self) -> usize {
+        (self.0 & 0xffffffff) as usize
+    }
+    /// Set the row's first cell index.
+    pub fn set_cells(&mut self, v: usize) {
+        self.0 = (self.0 & !0xffffffff) | (v as u64 & 0xffffffff);
+    }
+    /// True if cells can have managed style, hyperlink, or grapheme data.
+    pub fn managed_memory(self) -> bool {
+        self.styled() || self.hyperlink() || self.grapheme()
+    }
+    /// Prompt-row classification.
+    pub fn semantic_prompt(self) -> SemanticPrompt {
+        match (self.0 >> 37) & 3 {
+            1 => SemanticPrompt::Prompt,
+            2 => SemanticPrompt::PromptContinuation,
+            _ => SemanticPrompt::None,
+        }
+    }
+    /// Set prompt-row classification.
+    pub fn set_semantic_prompt(&mut self, v: SemanticPrompt) {
+        self.0 = (self.0 & !(3 << 37)) | ((v as u64) << 37);
+    }
+    /// Read the wrap flag.
+    pub fn wrap(self) -> bool {
+        self.0 & (1 << 32) != 0
+    }
+    /// Update the wrap flag.
+    pub fn set_wrap(&mut self, v: bool) {
+        self.0 = (self.0 & !(1 << 32)) | (u64::from(v) << 32);
+    }
+    /// Read the wrap_continuation flag.
+    pub fn wrap_continuation(self) -> bool {
+        self.0 & (1 << 33) != 0
+    }
+    /// Update the wrap_continuation flag.
+    pub fn set_wrap_continuation(&mut self, v: bool) {
+        self.0 = (self.0 & !(1 << 33)) | (u64::from(v) << 33);
+    }
+    /// Read the grapheme flag.
+    pub fn grapheme(self) -> bool {
+        self.0 & (1 << 34) != 0
+    }
+    /// Update the grapheme flag.
+    pub fn set_grapheme(&mut self, v: bool) {
+        self.0 = (self.0 & !(1 << 34)) | (u64::from(v) << 34);
+    }
+    /// Read the styled flag.
+    pub fn styled(self) -> bool {
+        self.0 & (1 << 35) != 0
+    }
+    /// Update the styled flag.
+    pub fn set_styled(&mut self, v: bool) {
+        self.0 = (self.0 & !(1 << 35)) | (u64::from(v) << 35);
+    }
+    /// Read the hyperlink flag.
+    pub fn hyperlink(self) -> bool {
+        self.0 & (1 << 36) != 0
+    }
+    /// Update the hyperlink flag.
+    pub fn set_hyperlink(&mut self, v: bool) {
+        self.0 = (self.0 & !(1 << 36)) | (u64::from(v) << 36);
+    }
+    /// Read the kitty_virtual_placeholder flag.
+    pub fn kitty_virtual_placeholder(self) -> bool {
+        self.0 & (1 << 39) != 0
+    }
+    /// Update the kitty_virtual_placeholder flag.
+    pub fn set_kitty_virtual_placeholder(&mut self, v: bool) {
+        self.0 = (self.0 & !(1 << 39)) | (u64::from(v) << 39);
+    }
+    /// Read the dirty flag.
+    pub fn dirty(self) -> bool {
+        self.0 & (1 << 40) != 0
+    }
+    /// Update the dirty flag.
+    pub fn set_dirty(&mut self, v: bool) {
+        self.0 = (self.0 & !(1 << 40)) | (u64::from(v) << 40);
+    }
+}
+/// Current logical page dimensions.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
+pub struct Size {
+    /// Columns currently addressable.
+    pub cols: u16,
+    /// Rows currently addressable.
+    pub rows: u16,
+}
+/// Fixed logical allocation limits for a page.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Capacity {
+    /// Allocated columns.
+    pub cols: u16,
+    /// Allocated rows.
+    pub rows: u16,
+    /// Requested style hash-table slots.
+    pub styles: u16,
+    /// Requested hyperlink-set bytes, excluding strings and map.
+    pub hyperlink_bytes: u16,
+    /// Requested grapheme bytes.
+    pub grapheme_bytes: u32,
+    /// Requested string bytes.
+    pub string_bytes: u32,
+}
+impl Default for Capacity {
+    fn default() -> Self {
+        Self {
+            cols: 0,
+            rows: 0,
+            styles: 16,
+            hyperlink_bytes: 192,
+            grapheme_bytes: GRAPHEME_BYTES_DEFAULT,
+            string_bytes: STRING_BYTES_DEFAULT,
+        }
+    }
+}
+/// Capacity adjustment that retains the original total byte allocation.
+#[derive(Debug, Default, Clone, Copy)]
+pub struct Adjustment {
+    /// New column count; rows absorb the size change.
+    pub cols: Option<u16>,
+}
+impl Capacity {
+    fn available_bytes_for_grid(self) -> usize {
+        let l = Page::layout(self);
+        let mut end = l.total_size;
+        for (bytes, align) in [
+            (l.hyperlink_map_layout.total_size, 4),
+            (l.hyperlink_set_layout.total_size, 8),
+            (l.string_alloc_layout.total_size, 8),
+            (l.grapheme_map_layout.total_size, 8),
+            (l.grapheme_alloc_layout.total_size, 8),
+            (l.styles_layout.total_size, 8),
+        ] {
+            end = (end - bytes) & !(align - 1);
+        }
+        end
+    }
+    /// Maximum columns that still allow one row without enlarging the page.
+    pub fn max_cols(self) -> Option<u16> {
+        let bytes = self.available_bytes_for_grid();
+        (bytes > 8).then(|| ((bytes - 8) / 8).min(65535) as u16)
+    }
+    /// Adjust columns, retaining the same page size by changing row capacity.
+    pub fn adjust(self, req: Adjustment) -> Result<Self, Error> {
+        let Some(cols) = req.cols else {
+            return Ok(self);
+        };
+        let rows = self.available_bytes_for_grid() / (8 + usize::from(cols) * 8);
+        if rows == 0 {
+            return Err(Error::OutOfMemory);
+        }
+        Ok(Self {
+            cols,
+            rows: rows.min(65535) as u16,
+            ..self
+        })
+    }
+}
+/// Logical bitmap allocator layout, preserving the reference size formula.
+#[derive(Debug, Default, Clone, Copy)]
+pub struct AllocLayout {
+    /// Total bytes including the reference allocator's chunk multiplier.
+    pub total_size: usize,
+    /// Number of 64-bit chunk bitmaps.
+    pub bitmap_count: usize,
+    /// Start of allocation data.
+    pub chunks_start: usize,
+}
+impl AllocLayout {
+    fn new(cap: usize, chunk: usize) -> Self {
+        let aligned = cap.next_multiple_of(chunk);
+        let bitmap_count = (aligned / chunk).div_ceil(64);
+        Self {
+            total_size: bitmap_count * 8 + aligned * chunk,
+            bitmap_count,
+            chunks_start: bitmap_count * 8,
+        }
+    }
+}
+/// Logical offset hash-map layout.
+#[derive(Debug, Default, Clone, Copy)]
+pub struct MapLayout {
+    /// Total bytes including the 16-byte header.
+    pub total_size: usize,
+    /// Maximum entries (no extra load-factor reduction).
+    pub capacity: usize,
+}
+impl MapLayout {
+    fn new(capacity: usize, value_size: usize, value_align: usize) -> Self {
+        let keys_start = (16 + capacity).next_multiple_of(4);
+        let vals_start = (keys_start + capacity * 4).next_multiple_of(value_align);
+        Self {
+            total_size: (vals_start + capacity * value_size).next_multiple_of(value_align.max(4)),
+            capacity,
+        }
+    }
+}
+/// Complete logical page layout for the 64-bit Linux reference ABI.
+#[derive(Debug, Clone, Copy)]
+pub struct Layout {
+    /// Page-aligned byte size.
+    pub total_size: usize,
+    /// Row array offset.
+    pub rows_start: usize,
+    /// Row array bytes.
+    pub rows_size: usize,
+    /// Cell array offset.
+    pub cells_start: usize,
+    /// Cell array bytes.
+    pub cells_size: usize,
+    /// Style set offset.
+    pub styles_start: usize,
+    /// Style set layout.
+    pub styles_layout: SetLayout,
+    /// Grapheme allocator offset.
+    pub grapheme_alloc_start: usize,
+    /// Grapheme allocator layout.
+    pub grapheme_alloc_layout: AllocLayout,
+    /// Grapheme map offset.
+    pub grapheme_map_start: usize,
+    /// Grapheme map layout.
+    pub grapheme_map_layout: MapLayout,
+    /// String allocator offset.
+    pub string_alloc_start: usize,
+    /// String allocator layout.
+    pub string_alloc_layout: AllocLayout,
+    /// Hyperlink set offset.
+    pub hyperlink_set_start: usize,
+    /// Hyperlink set layout.
+    pub hyperlink_set_layout: SetLayout,
+    /// Hyperlink map offset.
+    pub hyperlink_map_start: usize,
+    /// Hyperlink map layout.
+    pub hyperlink_map_layout: MapLayout,
+    /// Requested capacity.
+    pub capacity: Capacity,
+}
+/// Recoverable page operation errors.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Error {
+    /// Allocation or grid capacity exhausted.
+    OutOfMemory,
+    /// Cell or row is outside the logical page.
+    InvalidCoordinate,
+    /// A grid dimension is zero.
+    InvalidDimensions,
+    /// Style set needs more space.
+    StyleSetOutOfMemory,
+    /// Style IDs need compaction.
+    StyleSetNeedsRehash,
+    /// No contiguous grapheme allocation fits.
+    GraphemeAllocOutOfMemory,
+    /// Grapheme map capacity exhausted.
+    GraphemeMapOutOfMemory,
+    /// Hyperlink map capacity exhausted.
+    HyperlinkMapOutOfMemory,
+    /// Hyperlink set capacity exhausted.
+    SetOutOfMemory,
+    /// Hyperlink IDs need compaction.
+    SetNeedsRehash,
+    /// No contiguous string allocation fits.
+    StringsOutOfMemory,
+    /// Missing style or hyperlink ID.
+    InvalidId,
+    /// Reference count overflow or underflow.
+    InvalidRefCount,
+    /// Capacity cannot grow further.
+    OutOfSpace,
+}
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{self:?}")
+    }
+}
+impl std::error::Error for Error {}
+impl From<AddError> for Error {
+    fn from(e: AddError) -> Self {
+        match e {
+            AddError::OutOfMemory => Self::StyleSetOutOfMemory,
+            AddError::NeedsRehash => Self::StyleSetNeedsRehash,
+            AddError::InvalidId => Self::InvalidId,
+            AddError::InvalidRefCount => Self::InvalidRefCount,
+        }
+    }
+}
+#[derive(Debug, Clone, Copy)]
+struct Allocation {
+    start: usize,
+    len: usize,
+}
+#[derive(Debug, Clone)]
+struct ChunkAlloc {
+    used: Vec<bool>,
+    chunk: usize,
+}
+impl ChunkAlloc {
+    fn new(layout: AllocLayout, chunk: usize) -> Result<Self, Error> {
+        let mut used = Vec::new();
+        let count = layout.bitmap_count * 64;
+        used.try_reserve_exact(count)
+            .map_err(|_| Error::OutOfMemory)?;
+        used.resize(count, false);
+        Ok(Self { used, chunk })
+    }
+    fn alloc(&mut self, bytes: usize) -> Option<Allocation> {
+        let n = bytes.div_ceil(self.chunk);
+        if n == 0 {
+            return Some(Allocation { start: 0, len: 0 });
+        }
+        let mut run = 0;
+        for i in 0..self.used.len() {
+            if self.used[i] {
+                run = 0;
+            } else {
+                run += 1;
+            }
+            if run == n {
+                let start = i + 1 - n;
+                self.used[start..=i].fill(true);
+                return Some(Allocation { start, len: n });
+            }
+        }
+        None
+    }
+    fn free(&mut self, a: Allocation) {
+        self.used[a.start..a.start + a.len].fill(false);
+    }
+    fn reset(&mut self) {
+        self.used.fill(false);
+    }
+}
+/// Page-owned rows, cells, and bounded auxiliary storage.
+#[derive(Debug, Clone)]
+pub struct Page {
+    /// Logical dimensions; no greater than capacity.
+    pub size: Size,
+    /// Fixed logical allocation limits.
+    pub capacity: Capacity,
+    /// A full-page operation dirtied every row.
+    pub dirty: bool,
+    /// Row metadata in screen order.
+    pub rows: Vec<Row>,
+    /// Cells in row-major capacity order.
+    pub cells: Vec<Cell>,
+    /// Shared nondefault cell styles.
+    pub styles: style::Set,
+    /// Shared hyperlink values.
+    pub hyperlink_set: hyperlink::Set,
+    grapheme_map: HashMap<usize, Vec<u32>>,
+    grapheme_allocations: HashMap<usize, Allocation>,
+    grapheme_alloc: ChunkAlloc,
+    hyperlink_map: hyperlink::Map,
+    string_alloc: ChunkAlloc,
+    link_allocations: HashMap<u16, Vec<Allocation>>,
+    pause_integrity_checks: usize,
+}
+/// A cell with its page-independent managed values, used when copying pages.
+#[derive(Debug, Clone)]
+pub(crate) struct OwnedCell {
+    pub cell: Cell,
+    pub style: Option<Style>,
+    pub grapheme: Option<Vec<u32>>,
+    pub hyperlink: Option<Hyperlink>,
+}
+impl Page {
+    /// Compute the reference Zig layout without allocating memory.
+    pub fn layout(cap: Capacity) -> Layout {
+        let rows_start = 0;
+        let rows_size = usize::from(cap.rows) * 8;
+        let cells_start = rows_size;
+        let cells_size = usize::from(cap.rows) * usize::from(cap.cols) * 8;
+        let styles_start = (cells_start + cells_size).next_multiple_of(8);
+        let styles_layout = SetLayout::init(usize::from(cap.styles), STYLE_ITEM_SIZE, 4);
+        let grapheme_alloc_start = (styles_start + styles_layout.total_size).next_multiple_of(8);
+        let grapheme_alloc_layout = AllocLayout::new(cap.grapheme_bytes as usize, 16);
+        let grapheme_map_start =
+            (grapheme_alloc_start + grapheme_alloc_layout.total_size).next_multiple_of(8);
+        let gc = if cap.grapheme_bytes == 0 {
+            0
+        } else {
+            (cap.grapheme_bytes as usize)
+                .div_ceil(16)
+                .next_power_of_two()
+        };
+        let grapheme_map_layout = MapLayout::new(gc, 16, 8);
+        let string_alloc_start =
+            (grapheme_map_start + grapheme_map_layout.total_size).next_multiple_of(8);
+        let string_alloc_layout = AllocLayout::new(cap.string_bytes as usize, 32);
+        let hyperlink_set_start =
+            (string_alloc_start + string_alloc_layout.total_size).next_multiple_of(8);
+        let hc = usize::from(cap.hyperlink_bytes) / HYPERLINK_ITEM_SIZE;
+        let hyperlink_set_layout = SetLayout::init(hc, HYPERLINK_ITEM_SIZE, 8);
+        let hyperlink_map_start =
+            (hyperlink_set_start + hyperlink_set_layout.total_size).next_multiple_of(4);
+        let hyperlink_map_layout = MapLayout::new(
+            if hc == 0 {
+                0
+            } else {
+                (hc * 16).next_power_of_two()
+            },
+            2,
+            2,
+        );
+        let total_size =
+            (hyperlink_map_start + hyperlink_map_layout.total_size).next_multiple_of(4096);
+        Layout {
+            total_size,
+            rows_start,
+            rows_size,
+            cells_start,
+            cells_size,
+            styles_start,
+            styles_layout,
+            grapheme_alloc_start,
+            grapheme_alloc_layout,
+            grapheme_map_start,
+            grapheme_map_layout,
+            string_alloc_start,
+            string_alloc_layout,
+            hyperlink_set_start,
+            hyperlink_set_layout,
+            hyperlink_map_start,
+            hyperlink_map_layout,
+            capacity: cap,
+        }
+    }
+    /// Allocate zeroed rows and cells. Initial logical size is the full capacity.
+    pub fn init(cap: Capacity) -> Result<Self, Error> {
+        if cap.cols == 0 || cap.rows == 0 {
+            return Err(Error::InvalidDimensions);
+        }
+        let l = Self::layout(cap);
+        if l.total_size > u32::MAX as usize {
+            return Err(Error::OutOfSpace);
+        }
+        let mut rows = Vec::new();
+        rows.try_reserve_exact(usize::from(cap.rows))
+            .map_err(|_| Error::OutOfMemory)?;
+        for y in 0..cap.rows {
+            let mut row = Row::default();
+            row.set_cells(usize::from(y) * usize::from(cap.cols));
+            rows.push(row);
+        }
+        let mut cells = Vec::new();
+        let count = usize::from(cap.cols) * usize::from(cap.rows);
+        cells
+            .try_reserve_exact(count)
+            .map_err(|_| Error::OutOfMemory)?;
+        cells.resize(count, Cell::default());
+        Ok(Self {
+            size: Size {
+                rows: cap.rows,
+                cols: cap.cols,
+            },
+            capacity: cap,
+            dirty: false,
+            rows,
+            cells,
+            styles: style::Set::init(usize::from(cap.styles))?,
+            hyperlink_set: hyperlink::Set::init(usize::from(cap.hyperlink_bytes) / 48)?,
+            grapheme_map: HashMap::new(),
+            grapheme_allocations: HashMap::new(),
+            grapheme_alloc: ChunkAlloc::new(l.grapheme_alloc_layout, 16)?,
+            hyperlink_map: HashMap::new(),
+            string_alloc: ChunkAlloc::new(l.string_alloc_layout, 32)?,
+            link_allocations: HashMap::new(),
+            pause_integrity_checks: 0,
+        })
+    }
+    /// Reset contents, retaining grid and allocator backing storage.
+    pub fn reinit(&mut self) -> Result<(), Error> {
+        self.cells.fill(Cell::default());
+        for (y, r) in self.rows.iter_mut().enumerate() {
+            *r = Row::default();
+            r.set_cells(y * usize::from(self.capacity.cols));
+        }
+        self.size = Size {
+            cols: self.capacity.cols,
+            rows: self.capacity.rows,
+        };
+        self.dirty = false;
+        self.grapheme_map.clear();
+        self.grapheme_allocations.clear();
+        self.grapheme_alloc.reset();
+        self.hyperlink_map.clear();
+        self.string_alloc.reset();
+        self.link_allocations.clear();
+        self.styles = style::Set::init(usize::from(self.capacity.styles))?;
+        self.hyperlink_set = hyperlink::Set::init(usize::from(self.capacity.hyperlink_bytes) / 48)?;
+        Ok(())
+    }
+    /// Return row metadata by logical row number.
+    pub fn get_row(&self, y: usize) -> Option<&Row> {
+        self.rows.get(y).filter(|_| y < usize::from(self.size.rows))
+    }
+    /// Return mutable row metadata by logical row number.
+    pub fn get_row_mut(&mut self, y: usize) -> Option<&mut Row> {
+        self.rows
+            .get_mut(y)
+            .filter(|_| y < usize::from(self.size.rows))
+    }
+    /// Return the visible cells of a logical row in O(1).
+    pub fn get_cells(&self, y: usize) -> Option<&[Cell]> {
+        let start = self.get_row(y)?.cells();
+        self.cells.get(start..start + usize::from(self.size.cols))
+    }
+    /// Return mutable visible cells of a logical row in O(1).
+    pub fn get_cells_mut(&mut self, y: usize) -> Option<&mut [Cell]> {
+        let start = self.get_row(y)?.cells();
+        self.cells
+            .get_mut(start..start + usize::from(self.size.cols))
+    }
+    /// Return a cell index for a logical coordinate.
+    pub fn cell_index(&self, x: usize, y: usize) -> Result<usize, Error> {
+        if x >= usize::from(self.size.cols) {
+            return Err(Error::InvalidCoordinate);
+        }
+        Ok(self.get_row(y).ok_or(Error::InvalidCoordinate)?.cells() + x)
+    }
+    /// Return both metadata and cell at a logical coordinate.
+    pub fn get_row_and_cell(&self, x: usize, y: usize) -> Option<(&Row, &Cell)> {
+        Some((self.get_row(y)?, &self.cells[self.cell_index(x, y).ok()?]))
+    }
+    /// Resolve style without a map lookup for the default style.
+    pub fn style(&self, cell: Cell) -> Style {
+        if cell.style_id() == 0 {
+            Style::default()
+        } else {
+            self.styles
+                .get(cell.style_id())
+                .copied()
+                .unwrap_or_default()
+        }
+    }
+    /// Assign and retain styling, releasing the cell's previous style.
+    pub fn set_style(&mut self, x: usize, y: usize, value: Style) -> Result<(), Error> {
+        let i = self.cell_index(x, y)?;
+        let id = if value.is_default() {
+            0
+        } else {
+            self.styles.add(value)?
+        };
+        let old = self.cells[i].style_id();
+        if old != 0 {
+            self.styles.release(old)?;
+        }
+        self.cells[i].set_style_id(id);
+        if id != 0 {
+            self.rows[y].set_styled(true);
+        }
+        self.rows[y].set_dirty(true);
+        Ok(())
+    }
+    /// Return additional codepoints, excluding the first stored on the cell.
+    pub fn lookup_grapheme(&self, index: usize) -> Option<&[u32]> {
+        self.grapheme_map.get(&index).map(Vec::as_slice)
+    }
+    /// Number of cells with grapheme data.
+    pub fn grapheme_count(&self) -> usize {
+        self.grapheme_map.len()
+    }
+    /// Maximum number of grapheme map entries.
+    pub fn grapheme_capacity(&self) -> usize {
+        Self::layout(self.capacity).grapheme_map_layout.capacity
+    }
+    /// Attach additional codepoints to a textual cell.
+    pub fn set_graphemes(&mut self, x: usize, y: usize, cps: &[u32]) -> Result<(), Error> {
+        let i = self.cell_index(x, y)?;
+        if self.cells[i].codepoint() == 0 || cps.is_empty() || self.cells[i].has_grapheme() {
+            return Err(Error::InvalidCoordinate);
+        }
+        if self.grapheme_count() >= self.grapheme_capacity() {
+            return Err(Error::GraphemeMapOutOfMemory);
+        }
+        self.grapheme_map
+            .try_reserve(1)
+            .map_err(|_| Error::OutOfMemory)?;
+        self.grapheme_allocations
+            .try_reserve(1)
+            .map_err(|_| Error::OutOfMemory)?;
+        let mut data = Vec::new();
+        data.try_reserve_exact(cps.len())
+            .map_err(|_| Error::OutOfMemory)?;
+        data.extend_from_slice(cps);
+        let a = self
+            .grapheme_alloc
+            .alloc(cps.len() * 4)
+            .ok_or(Error::GraphemeAllocOutOfMemory)?;
+        self.grapheme_map.insert(i, data);
+        self.grapheme_allocations.insert(i, a);
+        self.cells[i].set_content_tag(ContentTag::CodepointGrapheme);
+        self.rows[y].set_grapheme(true);
+        self.rows[y].set_dirty(true);
+        Ok(())
+    }
+    /// Append one additional codepoint, retaining allocation chunk semantics.
+    pub fn append_grapheme(&mut self, x: usize, y: usize, cp: u32) -> Result<(), Error> {
+        let i = self.cell_index(x, y)?;
+        if !self.cells[i].has_grapheme() {
+            return self.set_graphemes(x, y, &[cp]);
+        }
+        let data = self
+            .grapheme_map
+            .get_mut(&i)
+            .ok_or(Error::InvalidCoordinate)?;
+        data.try_reserve(1).map_err(|_| Error::OutOfMemory)?;
+        if data.len().is_multiple_of(4) {
+            let a = self
+                .grapheme_alloc
+                .alloc((data.len() + 1) * 4)
+                .ok_or(Error::GraphemeAllocOutOfMemory)?;
+            if let Some(old) = self.grapheme_allocations.insert(i, a) {
+                self.grapheme_alloc.free(old);
+            }
+        }
+        data.push(cp);
+        self.rows[y].set_dirty(true);
+        Ok(())
+    }
+    /// Release a cell's additional codepoints.
+    pub fn clear_grapheme(&mut self, index: usize) {
+        if self.grapheme_map.remove(&index).is_some()
+            && let Some(a) = self.grapheme_allocations.remove(&index)
+        {
+            self.grapheme_alloc.free(a);
+        }
+        if let Some(c) = self.cells.get_mut(index)
+            && c.has_grapheme()
+        {
+            c.set_content_tag(ContentTag::Codepoint);
+        }
+    }
+    /// Move grapheme ownership between cell indices.
+    pub fn move_grapheme(&mut self, src: usize, dst: usize) -> Result<(), Error> {
+        if src >= self.cells.len() || dst >= self.cells.len() {
+            return Err(Error::InvalidCoordinate);
+        }
+        if src == dst {
+            return Ok(());
+        }
+        self.clear_grapheme(dst);
+        if let Some(data) = self.grapheme_map.remove(&src) {
+            self.grapheme_map.insert(dst, data);
+            if let Some(a) = self.grapheme_allocations.remove(&src) {
+                self.grapheme_allocations.insert(dst, a);
+            }
+            self.cells[src].set_content_tag(ContentTag::Codepoint);
+            self.cells[dst].set_content_tag(ContentTag::CodepointGrapheme);
+        }
+        Ok(())
+    }
+    /// Look up a cell's page-local hyperlink ID.
+    pub fn lookup_hyperlink(&self, index: usize) -> Option<u16> {
+        self.hyperlink_map.get(&index).copied()
+    }
+    /// Number of hyperlink cells.
+    pub fn hyperlink_count(&self) -> usize {
+        self.hyperlink_map.len()
+    }
+    /// Maximum hyperlink-map entries.
+    pub fn hyperlink_capacity(&self) -> usize {
+        Self::layout(self.capacity).hyperlink_map_layout.capacity
+    }
+    /// Allocate strings and retain a page-local hyperlink.
+    pub fn insert_hyperlink(&mut self, link: Hyperlink) -> Result<u16, Error> {
+        let mut allocations = Vec::with_capacity(2);
+        let uri = self
+            .string_alloc
+            .alloc(link.uri.len())
+            .ok_or(Error::StringsOutOfMemory)?;
+        allocations.push(uri);
+        if let HyperlinkId::Explicit(v) = &link.id {
+            if let Some(a) = self.string_alloc.alloc(v.len()) {
+                allocations.push(a);
+            } else {
+                self.string_alloc.free(uri);
+                return Err(Error::StringsOutOfMemory);
+            }
+        }
+        let result = self.hyperlink_set.add(link);
+        let id = match result {
+            Ok(id) => id,
+            Err(e) => {
+                for a in allocations {
+                    self.string_alloc.free(a);
+                }
+                return Err(match e {
+                    AddError::NeedsRehash => Error::SetNeedsRehash,
+                    _ => Error::SetOutOfMemory,
+                });
+            }
+        };
+        // Trimmed set entries no longer own their retained string chunks.
+        let dead: Vec<_> = self
+            .link_allocations
+            .keys()
+            .copied()
+            .filter(|id| !self.hyperlink_set.contains_slot(*id))
+            .collect();
+        for id in dead {
+            if let Some(v) = self.link_allocations.remove(&id) {
+                for a in v {
+                    self.string_alloc.free(a);
+                }
+            }
+        }
+        if self.hyperlink_set.ref_count(id) > 1 {
+            for a in allocations {
+                self.string_alloc.free(a);
+            }
+        } else if let Some(v) = self.link_allocations.insert(id, allocations) {
+            for a in v {
+                self.string_alloc.free(a);
+            }
+        }
+        Ok(id)
+    }
+    /// Set a hyperlink, consuming an existing retained reference (no increment).
+    pub fn set_hyperlink(&mut self, x: usize, y: usize, id: u16) -> Result<(), Error> {
+        let i = self.cell_index(x, y)?;
+        if self.hyperlink_set.get(id).is_none() {
+            return Err(Error::InvalidId);
+        }
+        if !self.hyperlink_map.contains_key(&i)
+            && self.hyperlink_count() >= self.hyperlink_capacity()
+        {
+            return Err(Error::HyperlinkMapOutOfMemory);
+        }
+        self.hyperlink_map
+            .try_reserve(1)
+            .map_err(|_| Error::OutOfMemory)?;
+        self.clear_hyperlink(i)?;
+        self.hyperlink_map.insert(i, id);
+        self.cells[i].set_hyperlink(true);
+        self.rows[y].set_hyperlink(true);
+        Ok(())
+    }
+    /// Release a cell's hyperlink reference.
+    pub fn clear_hyperlink(&mut self, i: usize) -> Result<(), Error> {
+        if let Some(id) = self.hyperlink_map.remove(&i) {
+            self.hyperlink_set.release(id)?;
+        }
+        if let Some(c) = self.cells.get_mut(i) {
+            c.set_hyperlink(false);
+        }
+        Ok(())
+    }
+    /// Recompute the conservative row grapheme flag.
+    pub fn update_row_grapheme_flag(&mut self, y: usize) {
+        if let Some(c) = self.get_cells(y) {
+            let v = c.iter().any(|c| c.has_grapheme());
+            self.rows[y].set_grapheme(v);
+        }
+    }
+    /// Recompute the conservative row style flag.
+    pub fn update_row_styled_flag(&mut self, y: usize) {
+        if let Some(c) = self.get_cells(y) {
+            let v = c.iter().any(|c| c.has_styling());
+            self.rows[y].set_styled(v);
+        }
+    }
+    /// Recompute the conservative row hyperlink flag.
+    pub fn update_row_hyperlink_flag(&mut self, y: usize) {
+        if let Some(c) = self.get_cells(y) {
+            let v = c.iter().any(|c| c.hyperlink());
+            self.rows[y].set_hyperlink(v);
+        }
+    }
+    /// True if the page or any visible row is dirty.
+    pub fn is_dirty(&self) -> bool {
+        self.dirty
+            || self.rows[..usize::from(self.size.rows)]
+                .iter()
+                .any(|r| r.dirty())
+    }
+    /// Clear a half-open column range, optionally preserving protected cells.
+    pub fn clear_cells(
+        &mut self,
+        y: usize,
+        start: usize,
+        end: usize,
+        protect: bool,
+    ) -> Result<(), Error> {
+        if start > end || end > usize::from(self.size.cols) || y >= usize::from(self.size.rows) {
+            return Err(Error::InvalidCoordinate);
+        }
+        let base = self.rows[y].cells();
+        for i in base + start..base + end {
+            let c = self.cells[i];
+            if protect && c.protected() {
+                continue;
+            }
+            if c.has_styling() {
+                self.styles.release(c.style_id())?;
+            }
+            if c.has_grapheme() {
+                self.clear_grapheme(i);
+            }
+            if c.hyperlink() {
+                self.clear_hyperlink(i)?;
+            }
+            self.cells[i] = Cell::default();
+        }
+        self.rows[y].set_dirty(true);
+        Ok(())
+    }
+    /// Move a half-open cell range, clearing overwritten values and the source.
+    pub fn move_cells(
+        &mut self,
+        src_y: usize,
+        src_x: usize,
+        dst_y: usize,
+        dst_x: usize,
+        len: usize,
+    ) -> Result<(), Error> {
+        if src_x + len > usize::from(self.size.cols) || dst_x + len > usize::from(self.size.cols) {
+            return Err(Error::InvalidCoordinate);
+        }
+        let src = self.cell_index(src_x, src_y)?;
+        let dst = self.cell_index(dst_x, dst_y)?;
+        if src == dst {
+            return Ok(());
+        }
+        // Move in memmove order; auxiliary maps follow the cell indices.
+        for n in 0..len {
+            let n = if dst > src { len - 1 - n } else { n };
+            let si = src + n;
+            let di = dst + n;
+            self.clear_cells(dst_y, dst_x + n, dst_x + n + 1, false)?;
+            let c = self.cells[si];
+            self.cells[di] = c;
+            self.cells[si] = Cell::default();
+            if c.has_grapheme() {
+                if let Some(v) = self.grapheme_map.remove(&si) {
+                    self.grapheme_map.insert(di, v);
+                }
+                if let Some(a) = self.grapheme_allocations.remove(&si) {
+                    self.grapheme_allocations.insert(di, a);
+                }
+            }
+            if c.hyperlink()
+                && let Some(v) = self.hyperlink_map.remove(&si)
+            {
+                self.hyperlink_map.insert(di, v);
+            }
+        }
+        for y in [src_y, dst_y] {
+            self.update_row_grapheme_flag(y);
+            self.update_row_styled_flag(y);
+            self.update_row_hyperlink_flag(y);
+            self.rows[y].set_dirty(true);
+        }
+        Ok(())
+    }
+    /// Swap two cells and their managed values without changing reference counts.
+    pub fn swap_cells(&mut self, ax: usize, ay: usize, bx: usize, by: usize) -> Result<(), Error> {
+        let a = self.cell_index(ax, ay)?;
+        let b = self.cell_index(bx, by)?;
+        if a == b {
+            return Ok(());
+        }
+        self.cells.swap(a, b);
+
+        swap_map(&mut self.grapheme_map, a, b);
+        swap_map(&mut self.grapheme_allocations, a, b);
+        swap_map(&mut self.hyperlink_map, a, b);
+        for y in [ay, by] {
+            self.update_row_grapheme_flag(y);
+            self.update_row_styled_flag(y);
+            self.update_row_hyperlink_flag(y);
+            self.rows[y].set_dirty(true);
+        }
+        Ok(())
+    }
+    pub(crate) fn export_cell(&self, i: usize) -> OwnedCell {
+        let cell = self.cells[i];
+        OwnedCell {
+            cell,
+            style: if cell.has_styling() {
+                self.styles.get(cell.style_id()).copied()
+            } else {
+                None
+            },
+            grapheme: if cell.has_grapheme() {
+                self.grapheme_map.get(&i).cloned()
+            } else {
+                None
+            },
+            hyperlink: if cell.hyperlink() {
+                self.lookup_hyperlink(i)
+                    .and_then(|id| self.hyperlink_set.get(id))
+                    .cloned()
+            } else {
+                None
+            },
+        }
+    }
+    pub(crate) fn import_cell(&mut self, x: usize, y: usize, v: &OwnedCell) -> Result<(), Error> {
+        let i = self.cell_index(x, y)?;
+        self.clear_cells(y, x, x + 1, false)?;
+        let mut c = v.cell;
+        c.set_style_id(0);
+        c.set_hyperlink(false);
+        if c.has_grapheme() {
+            c.set_content_tag(ContentTag::Codepoint);
+        }
+        self.cells[i] = c;
+        if let Some(s) = v.style {
+            self.set_style(x, y, s)?;
+        }
+        if let Some(g) = &v.grapheme {
+            self.set_graphemes(x, y, g)?;
+        }
+        if let Some(h) = &v.hyperlink {
+            let id = if let Some(id) = self.hyperlink_set.lookup(h) {
+                self.hyperlink_set.r#use(id)?;
+                id
+            } else {
+                self.insert_hyperlink(h.clone())?
+            };
+            if let Err(e) = self.set_hyperlink(x, y, id) {
+                self.hyperlink_set.release(id)?;
+                return Err(e);
+            }
+        }
+        Ok(())
+    }
+    /// Clone rows from another page, truncating or padding columns as needed.
+    pub fn clone_from(&mut self, src: &Self, y_start: usize, y_end: usize) -> Result<(), Error> {
+        if y_start > y_end
+            || y_end > usize::from(src.size.rows)
+            || y_end - y_start > usize::from(self.capacity.rows)
+        {
+            return Err(Error::InvalidCoordinate);
+        }
+        for y in 0..y_end - y_start {
+            self.clone_row_from(src, y_start + y, y)?;
+        }
+        Ok(())
+    }
+    /// Clone one complete row to a destination row.
+    pub fn clone_row_from(&mut self, src: &Self, src_y: usize, dst_y: usize) -> Result<(), Error> {
+        let cols = usize::from(self.size.cols.min(src.size.cols));
+        self.clear_cells(dst_y, 0, usize::from(self.size.cols), false)?;
+        self.clone_partial_row_from(src, src_y, dst_y, 0, 0, cols)?;
+        let start = self.rows[dst_y].cells();
+        self.rows[dst_y] = *src.get_row(src_y).ok_or(Error::InvalidCoordinate)?;
+        self.rows[dst_y].set_cells(start);
+        if self.size.cols > src.size.cols {
+            let i = self.cell_index(usize::from(src.size.cols - 1), dst_y)?;
+            if self.cells[i].wide() == Wide::SpacerHead {
+                self.cells[i].set_wide(Wide::Narrow);
+            }
+        }
+        Ok(())
+    }
+    /// Clone a column range, preserving untouched destination cells.
+    pub fn clone_partial_row_from(
+        &mut self,
+        src: &Self,
+        src_y: usize,
+        dst_y: usize,
+        src_x: usize,
+        dst_x: usize,
+        len: usize,
+    ) -> Result<(), Error> {
+        if src_x
+            .checked_add(len)
+            .is_none_or(|end| end > usize::from(src.size.cols))
+            || dst_x
+                .checked_add(len)
+                .is_none_or(|end| end > usize::from(self.size.cols))
+        {
+            return Err(Error::InvalidCoordinate);
+        }
+        let source_row = *src.get_row(src_y).ok_or(Error::InvalidCoordinate)?;
+        let original_row = *self.get_row(dst_y).ok_or(Error::InvalidCoordinate)?;
+        self.clear_cells(dst_y, dst_x, dst_x + len, false)?;
+        if source_row.managed_memory() {
+            for n in 0..len {
+                let i = src.cell_index(src_x + n, src_y)?;
+                self.import_cell(dst_x + n, dst_y, &src.export_cell(i))?;
+            }
+        } else {
+            let from = source_row.cells() + src_x;
+            let to = original_row.cells() + dst_x;
+            self.cells[to..to + len].copy_from_slice(&src.cells[from..from + len]);
+        }
+        let managed = self.rows[dst_y];
+        let mut metadata = source_row;
+        metadata.set_cells(original_row.cells());
+        if len < usize::from(self.size.cols) {
+            metadata.set_wrap(original_row.wrap());
+            metadata.set_wrap_continuation(original_row.wrap_continuation());
+            metadata.set_grapheme(managed.grapheme());
+            metadata.set_styled(managed.styled());
+            metadata.set_hyperlink(managed.hyperlink());
+            metadata.set_dirty(source_row.dirty() || original_row.dirty());
+        }
+        self.rows[dst_y] = metadata;
+        Ok(())
+    }
+    /// Clone a range within the same page, including overlapping ranges.
+    pub fn clone_cells_within(
+        &mut self,
+        src_y: usize,
+        dst_y: usize,
+        src_x: usize,
+        dst_x: usize,
+        len: usize,
+    ) -> Result<(), Error> {
+        if src_x + len > usize::from(self.size.cols) || dst_x + len > usize::from(self.size.cols) {
+            return Err(Error::InvalidCoordinate);
+        }
+        let src = self.cell_index(src_x, src_y)?;
+        self.cell_index(dst_x, dst_y)?;
+        let data: Vec<_> = (src..src + len).map(|i| self.export_cell(i)).collect();
+        for (n, v) in data.iter().enumerate() {
+            self.import_cell(dst_x + n, dst_y, v)?;
+        }
+        Ok(())
+    }
+    /// Minimum capacity that can clone the half-open row range.
+    pub fn exact_row_capacity(&self, start: usize, end: usize) -> Result<Capacity, Error> {
+        if start >= end || end > usize::from(self.size.rows) {
+            return Err(Error::InvalidCoordinate);
+        }
+        let mut styles = HashSet::new();
+        let mut links = HashSet::new();
+        let mut gb = 0;
+        let mut sb = 0;
+        let mut hc: usize = 0;
+        for y in start..end {
+            let base = self.rows[y].cells();
+            for x in 0..usize::from(self.size.cols) {
+                let i = base + x;
+                let c = self.cells[i];
+                if c.has_styling() {
+                    styles.insert(c.style_id());
+                }
+                if let Some(g) = self.lookup_grapheme(i) {
+                    gb += (g.len() * 4).next_multiple_of(16);
+                }
+                if let Some(id) = self.lookup_hyperlink(i) {
+                    hc += 1;
+                    if links.insert(id)
+                        && let Some(h) = self.hyperlink_set.get(id)
+                    {
+                        sb += h.string_bytes();
+                    }
+                }
+            }
+        }
+        let sc = style::Set::capacity_for_count(styles.len());
+        let lc = hyperlink::Set::capacity_for_count(links.len()).max(hc.div_ceil(16));
+        Ok(Capacity {
+            cols: self.size.cols,
+            rows: (end - start) as u16,
+            styles: u16::try_from(sc).map_err(|_| Error::OutOfSpace)?,
+            hyperlink_bytes: u16::try_from(lc * 48).map_err(|_| Error::OutOfSpace)?,
+            grapheme_bytes: u32::try_from(gb).map_err(|_| Error::OutOfSpace)?,
+            string_bytes: u32::try_from(sb).map_err(|_| Error::OutOfSpace)?,
+        })
+    }
+    /// Nestable suspension of debug integrity checks.
+    pub fn pause_integrity_checks(&mut self, pause: bool) {
+        if pause {
+            self.pause_integrity_checks += 1;
+        } else {
+            self.pause_integrity_checks = self.pause_integrity_checks.saturating_sub(1);
+        }
+    }
+}
+/// Structural invariant failures reported by debug/test verification.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum IntegrityError {
+    /// ZeroRowCount invariant violation.
+    ZeroRowCount,
+    /// ZeroColCount invariant violation.
+    ZeroColCount,
+    /// UnmarkedGraphemeRow invariant violation.
+    UnmarkedGraphemeRow,
+    /// MissingGraphemeData invariant violation.
+    MissingGraphemeData,
+    /// InvalidGraphemeCount invariant violation.
+    InvalidGraphemeCount,
+    /// UnmarkedGraphemeCell invariant violation.
+    UnmarkedGraphemeCell,
+    /// MissingStyle invariant violation.
+    MissingStyle,
+    /// UnmarkedStyleRow invariant violation.
+    UnmarkedStyleRow,
+    /// MismatchedStyleRef invariant violation.
+    MismatchedStyleRef,
+    /// InvalidStyleCount invariant violation.
+    InvalidStyleCount,
+    /// MissingHyperlinkData invariant violation.
+    MissingHyperlinkData,
+    /// MismatchedHyperlinkRef invariant violation.
+    MismatchedHyperlinkRef,
+    /// UnmarkedHyperlinkCell invariant violation.
+    UnmarkedHyperlinkCell,
+    /// UnmarkedHyperlinkRow invariant violation.
+    UnmarkedHyperlinkRow,
+    /// InvalidSpacerTailLocation invariant violation.
+    InvalidSpacerTailLocation,
+    /// InvalidSpacerHeadLocation invariant violation.
+    InvalidSpacerHeadLocation,
+    /// UnwrappedSpacerHead invariant violation.
+    UnwrappedSpacerHead,
+    /// InvalidDimensions invariant violation.
+    InvalidDimensions,
+}
+#[cfg(any(debug_assertions, test))]
+impl Page {
+    /// Verify grid, metadata, auxiliary maps, and reference counts.
+    pub fn verify_integrity(&self) -> Result<(), IntegrityError> {
+        use IntegrityError as E;
+        if self.pause_integrity_checks > 0 {
+            return Ok(());
+        }
+        if self.size.rows == 0 {
+            return Err(E::ZeroRowCount);
+        }
+        if self.size.cols == 0 {
+            return Err(E::ZeroColCount);
+        }
+        if self.size.rows > self.capacity.rows || self.size.cols > self.capacity.cols {
+            return Err(E::InvalidDimensions);
+        }
+        let mut styles = HashMap::<u16, usize>::new();
+        let mut links = HashMap::<u16, usize>::new();
+        let mut graphemes = 0;
+        for y in 0..usize::from(self.size.rows) {
+            let r = self.rows[y];
+            let base = r.cells();
+            for x in 0..usize::from(self.size.cols) {
+                let i = base + x;
+                let c = self.cells[i];
+                if c.has_grapheme() {
+                    graphemes += 1;
+                    if !r.grapheme() {
+                        return Err(E::UnmarkedGraphemeRow);
+                    }
+                    let g = self.lookup_grapheme(i).ok_or(E::MissingGraphemeData)?;
+                    if g.is_empty() {
+                        return Err(E::InvalidGraphemeCount);
+                    }
+                } else if self.grapheme_map.contains_key(&i) {
+                    return Err(E::UnmarkedGraphemeCell);
+                }
+                if c.has_styling() {
+                    if !r.styled() {
+                        return Err(E::UnmarkedStyleRow);
+                    }
+                    if self.styles.get(c.style_id()).is_none() {
+                        return Err(E::MissingStyle);
+                    }
+                    *styles.entry(c.style_id()).or_default() += 1;
+                }
+                if c.hyperlink() {
+                    if !r.hyperlink() {
+                        return Err(E::UnmarkedHyperlinkRow);
+                    }
+                    let id = self.lookup_hyperlink(i).ok_or(E::MissingHyperlinkData)?;
+                    if self.hyperlink_set.get(id).is_none() {
+                        return Err(E::MissingHyperlinkData);
+                    }
+                    *links.entry(id).or_default() += 1;
+                } else if self.hyperlink_map.contains_key(&i) {
+                    return Err(E::UnmarkedHyperlinkCell);
+                }
+                match c.wide() {
+                    Wide::SpacerTail => {
+                        if x == 0 || self.cells[i - 1].wide() != Wide::Wide {
+                            return Err(E::InvalidSpacerTailLocation);
+                        }
+                    }
+                    Wide::SpacerHead => {
+                        if x + 1 != usize::from(self.size.cols) {
+                            return Err(E::InvalidSpacerHeadLocation);
+                        }
+                        if !r.wrap() {
+                            return Err(E::UnwrappedSpacerHead);
+                        }
+                    }
+                    _ => {}
+                }
+            }
+        }
+        if graphemes > self.grapheme_count() {
+            return Err(E::InvalidGraphemeCount);
+        }
+        for (id, _, refs) in self.styles.entries() {
+            if styles.get(&id).copied().unwrap_or(0) > usize::from(refs) {
+                return Err(E::MismatchedStyleRef);
+            }
+        }
+        for (id, _, refs) in self.hyperlink_set.entries() {
+            if links.get(&id).copied().unwrap_or(0) > usize::from(refs) {
+                return Err(E::MismatchedHyperlinkRef);
+            }
+        }
+        Ok(())
+    }
+    /// Assert structural integrity in debug/test builds.
+    pub fn assert_integrity(&self) {
+        assert_eq!(self.verify_integrity(), Ok(()));
+    }
+}
+
+fn swap_map<T>(map: &mut HashMap<usize, T>, a: usize, b: usize) {
+    let av = map.remove(&a);
+    let bv = map.remove(&b);
+    if let Some(v) = av {
+        map.insert(b, v);
+    }
+    if let Some(v) = bv {
+        map.insert(a, v);
+    }
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::style::{Color, Flags};
+    fn page() -> Page {
+        Page::init(Capacity {
+            cols: 10,
+            rows: 10,
+            styles: 8,
+            ..Capacity::default()
+        })
+        .unwrap()
+    }
+    fn write(p: &mut Page, x: usize, y: usize, cp: u32) {
+        let i = p.cell_index(x, y).unwrap();
+        p.cells[i] = Cell::init(cp);
+    }
+    fn cp(p: &Page, x: usize, y: usize) -> u32 {
+        p.get_row_and_cell(x, y).unwrap().1.codepoint()
+    }
+    fn bold() -> Style {
+        Style {
+            flags: Flags {
+                bold: true,
+                ..Flags::default()
+            },
+            ..Style::default()
+        }
+    }
+    fn link() -> Hyperlink {
+        Hyperlink {
+            id: HyperlinkId::Implicit(1),
+            uri: b"https://example.com".to_vec(),
+        }
+    }
+    fn clone_exact(p: &Page, end: usize) -> Page {
+        let cap = p.exact_row_capacity(0, end).unwrap();
+        let mut q = Page::init(cap).unwrap();
+        q.clone_from(p, 0, end).unwrap();
+        assert_eq!(q.exact_row_capacity(0, end).unwrap(), cap);
+        q.assert_integrity();
+        q
+    }
+    #[test]
+    fn page_layout_can_take_a_maxed_capacity() {
+        let l = Page::layout(Capacity {
+            cols: u16::MAX,
+            rows: u16::MAX,
+            styles: u16::MAX,
+            hyperlink_bytes: u16::MAX,
+            grapheme_bytes: u32::MAX,
+            string_bytes: u32::MAX,
+        });
+        assert!(l.total_size > u32::MAX as usize);
+    }
+    #[test]
+    fn cell_is_zero_by_default() {
+        let c = Cell::init(0);
+        assert_eq!(c.raw(), 0);
+        assert_eq!(c.semantic_content(), SemanticContent::Output);
+        assert_eq!(std::mem::size_of::<Cell>(), 8);
+        assert_eq!(std::mem::size_of::<Row>(), 8);
+    }
+    #[test]
+    fn page_capacity_adjust_cols_down() {
+        let original = Page::layout(STD_CAPACITY).total_size;
+        let cap = STD_CAPACITY
+            .adjust(Adjustment {
+                cols: Some(STD_CAPACITY.cols / 2),
+            })
+            .unwrap();
+        assert_eq!(Page::layout(cap).total_size, original);
+        assert!(
+            Page::layout(Capacity {
+                rows: cap.rows + 1,
+                ..cap
+            })
+            .total_size
+                > original
+        );
+    }
+    #[test]
+    fn page_capacity_adjust_cols_down_to_1() {
+        let original = Page::layout(STD_CAPACITY).total_size;
+        let cap = STD_CAPACITY.adjust(Adjustment { cols: Some(1) }).unwrap();
+        assert_eq!(Page::layout(cap).total_size, original);
+        assert!(
+            Page::layout(Capacity {
+                rows: cap.rows + 1,
+                ..cap
+            })
+            .total_size
+                > original
+        );
+    }
+    #[test]
+    fn page_capacity_adjust_cols_up() {
+        let original = Page::layout(STD_CAPACITY).total_size;
+        let cap = STD_CAPACITY
+            .adjust(Adjustment {
+                cols: Some(STD_CAPACITY.cols * 2),
+            })
+            .unwrap();
+        assert_eq!(Page::layout(cap).total_size, original);
+        assert!(
+            Page::layout(Capacity {
+                rows: cap.rows + 1,
+                ..cap
+            })
+            .total_size
+                > original
+        );
+    }
+    #[test]
+    fn page_capacity_adjust_cols_sweep() {
+        let original = Page::layout(STD_CAPACITY).total_size;
+        let mut cap = STD_CAPACITY;
+        for cols in 1..STD_CAPACITY.cols * 2 {
+            cap = cap.adjust(Adjustment { cols: Some(cols) }).unwrap();
+            assert_eq!(Page::layout(cap).total_size, original);
+            assert!(
+                Page::layout(Capacity {
+                    rows: cap.rows + 1,
+                    ..cap
+                })
+                .total_size
+                    > original
+            );
+        }
+    }
+    #[test]
+    fn page_capacity_adjust_cols_too_high() {
+        assert_eq!(
+            STD_CAPACITY.adjust(Adjustment {
+                cols: Some(u16::MAX)
+            }),
+            Err(Error::OutOfMemory)
+        );
+    }
+    #[test]
+    fn capacity_max_cols_basic() {
+        let max = STD_CAPACITY.max_cols().unwrap();
+        assert!(max >= STD_CAPACITY.cols);
+        assert!(
+            STD_CAPACITY
+                .adjust(Adjustment { cols: Some(max) })
+                .unwrap()
+                .rows
+                >= 1
+        );
+        assert_eq!(
+            STD_CAPACITY.adjust(Adjustment {
+                cols: Some(max + 1)
+            }),
+            Err(Error::OutOfMemory)
+        );
+    }
+    #[test]
+    fn capacity_max_cols_preserves_total_size() {
+        let cap = STD_CAPACITY
+            .adjust(Adjustment {
+                cols: STD_CAPACITY.max_cols(),
+            })
+            .unwrap();
+        assert_eq!(
+            Page::layout(cap).total_size,
+            Page::layout(STD_CAPACITY).total_size
+        );
+    }
+    #[test]
+    fn capacity_max_cols_with_1_row_exactly() {
+        assert_eq!(
+            STD_CAPACITY
+                .adjust(Adjustment {
+                    cols: STD_CAPACITY.max_cols()
+                })
+                .unwrap()
+                .rows,
+            1
+        );
+    }
+    #[test]
+    fn page_init() {
+        let p = Page::init(Capacity {
+            cols: 120,
+            rows: 80,
+            styles: 32,
+            ..Capacity::default()
+        })
+        .unwrap();
+        p.assert_integrity();
+    }
+    #[test]
+    fn page_read_and_write_cells() {
+        let mut p = page();
+        for y in 0..10 {
+            write(&mut p, 1, y, y as u32);
+        }
+        for y in 0..10 {
+            assert_eq!(cp(&p, 1, y), y as u32);
+        }
+    }
+    #[test]
+    fn page_append_grapheme_small() {
+        let mut p = page();
+        write(&mut p, 0, 0, 9);
+        p.append_grapheme(0, 0, 10).unwrap();
+        assert!(p.rows[0].grapheme());
+        assert_eq!(p.lookup_grapheme(0), Some([10].as_slice()));
+        p.append_grapheme(0, 0, 11).unwrap();
+        assert_eq!(p.lookup_grapheme(0), Some([10, 11].as_slice()));
+        p.clear_grapheme(0);
+        p.update_row_grapheme_flag(0);
+        assert!(!p.rows[0].grapheme());
+        assert!(!p.cells[0].has_grapheme());
+    }
+    #[test]
+    fn page_append_grapheme_larger_than_chunk() {
+        let mut p = page();
+        write(&mut p, 0, 0, 9);
+        for i in 0..40 {
+            p.append_grapheme(0, 0, 10 + i).unwrap();
+        }
+        assert_eq!(p.lookup_grapheme(0).unwrap(), (10..50).collect::<Vec<_>>());
+    }
+    #[test]
+    fn page_clear_grapheme_not_all_cells() {
+        let mut p = page();
+        for x in 0..2 {
+            write(&mut p, x, 0, 9);
+            p.append_grapheme(x, 0, 10).unwrap();
+        }
+        p.clear_grapheme(0);
+        p.update_row_grapheme_flag(0);
+        assert!(p.rows[0].grapheme());
+        assert!(!p.cells[0].has_grapheme());
+        assert!(p.cells[1].has_grapheme());
+    }
+    #[test]
+    fn page_clone() {
+        let mut p = page();
+        for y in 0..10 {
+            write(&mut p, 1, y, y as u32);
+        }
+        let q = p.clone();
+        assert_eq!(p.capacity, q.capacity);
+        for y in 0..10 {
+            write(&mut p, 1, y, 0);
+            assert_eq!(cp(&q, 1, y), y as u32);
+            assert_eq!(cp(&p, 1, y), 0);
+        }
+    }
+    #[test]
+    fn page_clone_from() {
+        let mut p = page();
+        for y in 0..10 {
+            write(&mut p, 1, y, y as u32);
+        }
+        let q = {
+            let mut q = page();
+            q.clone_from(&p, 0, 10).unwrap();
+            q
+        };
+        assert_eq!(p.capacity, q.capacity);
+        for y in 0..10 {
+            write(&mut p, 1, y, 0);
+            assert_eq!(cp(&q, 1, y), y as u32);
+            assert_eq!(cp(&p, 1, y), 0);
+        }
+    }
+    #[test]
+    fn page_clone_graphemes() {
+        let mut p = page();
+        write(&mut p, 0, 0, 9);
+        p.append_grapheme(0, 0, 10).unwrap();
+        p.append_grapheme(0, 0, 11).unwrap();
+        let q = p.clone();
+        assert!(q.rows[0].grapheme());
+        assert_eq!(q.lookup_grapheme(0).unwrap(), [10, 11]);
+    }
+    #[test]
+    fn page_clone_styles() {
+        let mut p = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+            p.set_style(x, 0, bold()).unwrap();
+        }
+        let q = p.clone();
+        for x in 0..10 {
+            assert_eq!(p.cells[x].style_id(), q.cells[x].style_id());
+            assert_eq!(q.style(q.cells[x]), bold());
+        }
+        q.assert_integrity();
+    }
+    #[test]
+    fn page_clone_from_shrink_columns() {
+        let mut p = page();
+        for y in 0..10 {
+            write(&mut p, 1, y, y as u32);
+        }
+        let mut q = Page::init(Capacity {
+            cols: 5,
+            ..p.capacity
+        })
+        .unwrap();
+        q.clone_from(&p, 0, 10).unwrap();
+        assert_eq!(q.size.cols, 5);
+        for y in 0..10 {
+            assert_eq!(cp(&q, 1, y), y as u32);
+        }
+    }
+    #[test]
+    fn page_clone_from_partial() {
+        let mut p = page();
+        for y in 0..10 {
+            write(&mut p, 1, y, y as u32);
+        }
+        let mut q = page();
+        q.clone_from(&p, 0, 5).unwrap();
+        for y in 0..10 {
+            assert_eq!(cp(&q, 1, y), if y < 5 { y as u32 } else { 0 });
+        }
+    }
+    #[test]
+    fn page_clone_from_hyperlinks_exact_capacity() {
+        let mut p = Page::init(Capacity {
+            cols: 50,
+            rows: 50,
+            ..Capacity::default()
+        })
+        .unwrap();
+        let id = p.insert_hyperlink(link()).unwrap();
+        for n in 0..p.hyperlink_capacity() {
+            let x = n / 50;
+            let y = n % 50;
+            write(&mut p, x, y, 42);
+            p.hyperlink_set.r#use(id).unwrap();
+            p.set_hyperlink(x, y, id).unwrap();
+        }
+        assert_eq!(p.hyperlink_count(), p.hyperlink_capacity());
+        let mut q = Page::init(p.capacity).unwrap();
+        q.clone_from(&p, 0, 50).unwrap();
+        assert_eq!(q.hyperlink_count(), p.hyperlink_count());
+    }
+    #[test]
+    fn page_clone_from_graphemes() {
+        let mut p = page();
+        for y in 0..10 {
+            write(&mut p, 1, y, y as u32 + 1);
+            p.append_grapheme(1, y, 10).unwrap();
+        }
+        let mut q = page();
+        q.clone_from(&p, 0, 10).unwrap();
+        for y in 0..10 {
+            p.clear_cells(y, 0, 10, false).unwrap();
+            assert_eq!(cp(&q, 1, y), y as u32 + 1);
+            assert_eq!(
+                q.lookup_grapheme(q.cell_index(1, y).unwrap()).unwrap(),
+                [10]
+            );
+        }
+        q.assert_integrity();
+    }
+    #[test]
+    fn page_clone_from_frees_dst_graphemes() {
+        let p = page();
+        let mut q = page();
+        for y in 0..10 {
+            write(&mut q, 1, y, 9);
+            q.append_grapheme(1, y, 10).unwrap();
+        }
+        q.clone_from(&p, 0, 10).unwrap();
+        assert_eq!(q.grapheme_count(), 0);
+        for y in 0..10 {
+            assert!(!q.rows[y].grapheme());
+        }
+    }
+    #[test]
+    fn page_clone_row_from_partial() {
+        let mut p = page();
+        let mut q = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+        }
+        q.clone_partial_row_from(&p, 0, 0, 2, 2, 6).unwrap();
+        for x in 0..10 {
+            assert_eq!(
+                cp(&q, x, 0),
+                if (2..8).contains(&x) { x as u32 + 1 } else { 0 }
+            );
+        }
+        assert_eq!(q.grapheme_count(), 0);
+        assert!(!q.rows[0].grapheme());
+        q.assert_integrity();
+    }
+    #[test]
+    fn page_clone_row_from_partial_grapheme_in_non_copied_source_region() {
+        let mut p = page();
+        let mut q = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+        }
+        for x in [0, 9] {
+            p.append_grapheme(x, 0, 10).unwrap();
+        }
+        q.clone_partial_row_from(&p, 0, 0, 2, 2, 6).unwrap();
+        for x in 0..10 {
+            assert_eq!(
+                cp(&q, x, 0),
+                if (2..8).contains(&x) { x as u32 + 1 } else { 0 }
+            );
+        }
+        assert_eq!(q.grapheme_count(), 0);
+        assert!(!q.rows[0].grapheme());
+        q.assert_integrity();
+    }
+    #[test]
+    fn page_clone_row_from_partial_grapheme_in_non_copied_dest_region() {
+        let mut p = page();
+        let mut q = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+        }
+        for x in 0..10 {
+            write(&mut q, x, 0, 0xbb);
+        }
+        for x in [0, 9] {
+            q.append_grapheme(x, 0, 10).unwrap();
+        }
+        q.clone_partial_row_from(&p, 0, 0, 2, 2, 6).unwrap();
+        for x in 0..10 {
+            assert_eq!(
+                cp(&q, x, 0),
+                if (2..8).contains(&x) {
+                    x as u32 + 1
+                } else {
+                    0xbb
+                }
+            );
+        }
+        assert_eq!(q.grapheme_count(), 2);
+        assert!(q.rows[0].grapheme());
+        q.assert_integrity();
+    }
+    #[test]
+    fn page_clone_row_from_partial_hyperlink_in_same_page_copy() {
+        let mut p = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+        }
+        let id = p.insert_hyperlink(link()).unwrap();
+        p.set_hyperlink(7, 0, id).unwrap();
+        p.clone_cells_within(0, 1, 2, 2, 8 - 2).unwrap();
+        for x in 0..10 {
+            assert_eq!(
+                cp(&p, x, 1),
+                if (2..8).contains(&x) { x as u32 + 1 } else { 0 }
+            );
+        }
+        assert_eq!(p.hyperlink_count(), 2);
+        assert!(p.rows[1].hyperlink());
+        p.assert_integrity();
+    }
+    #[test]
+    fn page_clone_row_from_partial_hyperlink_in_same_page_omit() {
+        let mut p = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+        }
+        let id = p.insert_hyperlink(link()).unwrap();
+        p.set_hyperlink(7, 0, id).unwrap();
+        p.clone_cells_within(0, 1, 2, 2, 6 - 2).unwrap();
+        for x in 0..10 {
+            assert_eq!(
+                cp(&p, x, 1),
+                if (2..6).contains(&x) { x as u32 + 1 } else { 0 }
+            );
+        }
+        assert_eq!(p.hyperlink_count(), 1);
+        assert!(!p.rows[1].hyperlink());
+        p.assert_integrity();
+    }
+    #[test]
+    fn page_move_cells_text_only() {
+        let mut p = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+        }
+        p.move_cells(0, 0, 1, 0, 10).unwrap();
+        for x in 0..10 {
+            assert_eq!(cp(&p, x, 0), 0);
+            assert_eq!(cp(&p, x, 1), x as u32 + 1);
+        }
+        p.assert_integrity();
+    }
+    #[test]
+    fn page_move_cells_graphemes() {
+        let mut p = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+            p.append_grapheme(x, 0, 10).unwrap();
+        }
+        p.move_cells(0, 0, 1, 0, 10).unwrap();
+        for x in 0..10 {
+            assert_eq!(cp(&p, x, 0), 0);
+            assert_eq!(cp(&p, x, 1), x as u32 + 1);
+            assert_eq!(
+                p.lookup_grapheme(p.cell_index(x, 1).unwrap()).unwrap(),
+                [10]
+            );
+        }
+        p.assert_integrity();
+    }
+    #[test]
+    fn page_verify_integrity_graphemes_good() {
+        let mut p = page();
+        write(&mut p, 0, 0, 1);
+        p.append_grapheme(0, 0, 10).unwrap();
+        p.assert_integrity();
+    }
+    #[test]
+    fn page_verify_integrity_grapheme_row_not_marked() {
+        let mut p = page();
+        write(&mut p, 0, 0, 1);
+        p.append_grapheme(0, 0, 10).unwrap();
+        p.rows[0].set_grapheme(false);
+        assert_eq!(
+            p.verify_integrity(),
+            Err(IntegrityError::UnmarkedGraphemeRow)
+        );
+    }
+    #[test]
+    fn page_verify_integrity_styles_good() {
+        let mut p = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+            p.set_style(x, 0, bold()).unwrap();
+        }
+        p.assert_integrity();
+    }
+    #[test]
+    fn page_verify_integrity_styles_ref_count_mismatch() {
+        let mut p = page();
+        for x in 0..10 {
+            write(&mut p, x, 0, x as u32 + 1);
+            p.set_style(x, 0, bold()).unwrap();
+        }
+        p.styles.release(p.cells[0].style_id()).unwrap();
+        assert_eq!(
+            p.verify_integrity(),
+            Err(IntegrityError::MismatchedStyleRef)
+        );
+    }
+    #[test]
+    fn page_verify_integrity_zero_rows() {
+        let mut p = page();
+        p.size.rows = 0;
+        assert_eq!(p.verify_integrity(), Err(IntegrityError::ZeroRowCount));
+    }
+    #[test]
+    fn page_verify_integrity_zero_cols() {
+        let mut p = page();
+        p.size.cols = 0;
+        assert_eq!(p.verify_integrity(), Err(IntegrityError::ZeroColCount));
+    }
+    #[test]
+    fn page_exact_row_capacity_empty_rows() {
+        let p = page();
+        assert_eq!(
+            p.exact_row_capacity(0, 5).unwrap(),
+            Capacity {
+                cols: 10,
+                rows: 5,
+                styles: 0,
+                hyperlink_bytes: 0,
+                grapheme_bytes: 0,
+                string_bytes: 0
+            }
+        );
+    }
+    #[test]
+    fn page_exact_row_capacity_styles() {
+        let mut p = page();
+        assert_eq!(p.exact_row_capacity(0, 5).unwrap().styles, 0);
+        p.set_style(0, 0, bold()).unwrap();
+        assert_eq!(
+            usize::from(p.exact_row_capacity(0, 5).unwrap().styles),
+            style::Set::capacity_for_count(1)
+        );
+        p.set_style(1, 0, bold()).unwrap();
+        assert_eq!(
+            usize::from(p.exact_row_capacity(0, 5).unwrap().styles),
+            style::Set::capacity_for_count(1)
+        );
+        p.set_style(
+            2,
+            0,
+            Style {
+                flags: Flags {
+                    italic: true,
+                    ..Flags::default()
+                },
+                ..Style::default()
+            },
+        )
+        .unwrap();
+        p.set_style(
+            0,
+            7,
+            Style {
+                flags: Flags {
+                    underline: ghostty_vt::sgr::Underline::Single,
+                    ..Flags::default()
+                },
+                ..Style::default()
+            },
+        )
+        .unwrap();
+        assert_eq!(
+            usize::from(p.exact_row_capacity(0, 5).unwrap().styles),
+            style::Set::capacity_for_count(2)
+        );
+        assert_eq!(
+            usize::from(p.exact_row_capacity(0, 10).unwrap().styles),
+            style::Set::capacity_for_count(3)
+        );
+        clone_exact(&p, 5);
+    }
+    #[test]
+    fn page_exact_row_capacity_single_style_clone() {
+        let mut p = page();
+        p.set_style(0, 0, bold()).unwrap();
+        let q = clone_exact(&p, 1);
+        assert_eq!(q.style(q.cells[0]), bold());
+    }
+    #[test]
+    fn page_exact_row_capacity_styles_max_single_row() {
+        let mut p = Page::init(Capacity {
+            cols: u16::MAX,
+            rows: 1,
+            styles: u16::MAX,
+            ..Capacity::default()
+        })
+        .unwrap();
+        for x in 0..1000 {
+            p.set_style(
+                x,
+                0,
+                Style {
+                    fg_color: Color::Rgb(Rgb {
+                        r: x as u8,
+                        g: (x >> 8) as u8,
+                        b: 0,
+                    }),
+                    ..Style::default()
+                },
+            )
+            .unwrap();
+        }
+        assert_eq!(
+            usize::from(p.exact_row_capacity(0, 1).unwrap().styles),
+            style::Set::capacity_for_count(1000)
+        );
+    }
+    #[test]
+    fn page_exact_row_capacity_grapheme_bytes() {
+        let mut p = page();
+        assert_eq!(p.exact_row_capacity(0, 5).unwrap().grapheme_bytes, 0);
+        for (x, cp0) in [(0, 97), (1, 101), (2, 111)] {
+            write(&mut p, x, 0, cp0);
+            p.append_grapheme(x, 0, 0x301).unwrap();
+            assert_eq!(
+                p.exact_row_capacity(0, 5).unwrap().grapheme_bytes,
+                (x as u32 + 1) * 16
+            );
+        }
+        p.append_grapheme(2, 0, 0x302).unwrap();
+        p.append_grapheme(2, 0, 0x303).unwrap();
+        write(&mut p, 0, 7, 120);
+        p.append_grapheme(0, 7, 0x304).unwrap();
+        assert_eq!(p.exact_row_capacity(0, 5).unwrap().grapheme_bytes, 48);
+        assert_eq!(p.exact_row_capacity(0, 10).unwrap().grapheme_bytes, 64);
+        clone_exact(&p, 5);
+    }
+    #[test]
+    fn page_exact_row_capacity_grapheme_bytes_larger_than_chunk() {
+        let mut p = page();
+        write(&mut p, 0, 0, 97);
+        for cp0 in 0x300..0x306 {
+            p.append_grapheme(0, 0, cp0).unwrap();
+        }
+        assert_eq!(p.exact_row_capacity(0, 1).unwrap().grapheme_bytes, 32);
+        clone_exact(&p, 1);
+    }
+    #[test]
+    fn page_exact_row_capacity_hyperlinks() {
+        let mut p = Page::init(Capacity {
+            hyperlink_bytes: 32 * 48,
+            string_bytes: 512,
+            ..page().capacity
+        })
+        .unwrap();
+        assert_eq!(p.exact_row_capacity(0, 5).unwrap().hyperlink_bytes, 0);
+        let id = p.insert_hyperlink(link()).unwrap();
+        p.set_hyperlink(0, 0, id).unwrap();
+        let one = p.exact_row_capacity(0, 5).unwrap();
+        assert_eq!(one.string_bytes, 32);
+        assert_eq!(
+            usize::from(one.hyperlink_bytes),
+            hyperlink::Set::capacity_for_count(1) * 48
+        );
+        p.hyperlink_set.r#use(id).unwrap();
+        p.set_hyperlink(1, 0, id).unwrap();
+        assert_eq!(p.exact_row_capacity(0, 5).unwrap(), one);
+        let id = p
+            .insert_hyperlink(Hyperlink {
+                id: HyperlinkId::Explicit(b"my-link-id".to_vec()),
+                uri: b"https://other.example.org/path".to_vec(),
+            })
+            .unwrap();
+        p.set_hyperlink(2, 0, id).unwrap();
+        assert_eq!(p.exact_row_capacity(0, 5).unwrap().string_bytes, 96);
+        let id = p
+            .insert_hyperlink(Hyperlink {
+                id: HyperlinkId::Implicit(99),
+                uri: b"https://outside.example.com".to_vec(),
+            })
+            .unwrap();
+        p.set_hyperlink(0, 7, id).unwrap();
+        assert_eq!(p.exact_row_capacity(0, 5).unwrap().string_bytes, 96);
+        assert_eq!(p.exact_row_capacity(0, 10).unwrap().string_bytes, 128);
+        clone_exact(&p, 5);
+    }
+    #[test]
+    fn page_exact_row_capacity_single_hyperlink_clone() {
+        let mut p = page();
+        let id = p.insert_hyperlink(link()).unwrap();
+        p.set_hyperlink(0, 0, id).unwrap();
+        let q = clone_exact(&p, 1);
+        assert!(q.cells[0].hyperlink());
+    }
+    #[test]
+    fn page_exact_row_capacity_hyperlink_map_capacity_for_many_cells() {
+        let mut p = Page::init(Capacity {
+            cols: 50,
+            rows: 2,
+            hyperlink_bytes: 32 * 48,
+            string_bytes: 512,
+            ..Capacity::default()
+        })
+        .unwrap();
+        let id = p.insert_hyperlink(link()).unwrap();
+        for x in 0..50 {
+            if x > 0 {
+                p.hyperlink_set.r#use(id).unwrap();
+            }
+            p.set_hyperlink(x, 0, id).unwrap();
+        }
+        assert!(p.exact_row_capacity(0, 1).unwrap().hyperlink_bytes >= 4 * 48);
+        let q = clone_exact(&p, 1);
+        assert_eq!(q.hyperlink_count(), 50);
+    }
+}

crates/ghostty-terminal/src/page_list.rs

@@ -0,0 +1,5119 @@
+//! Linked terminal pages, byte-bounded history, and stable tracked coordinates.
+use crate::{
+    page::{
+        self, Adjustment, Capacity, Cell, Error, OwnedCell, Page, Row, SemanticContent,
+        SemanticPrompt, Wide,
+    },
+    point::{Coordinate, Point, Tag},
+};
+use std::collections::HashMap;
+/// Slab index and generation; stale references never alias a reused node.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct NodeId {
+    index: usize,
+    generation: u64,
+}
+impl NodeId {
+    /// Index in the owning list's slab.
+    pub fn index(self) -> usize {
+        self.index
+    }
+    /// Generation assigned when the node was allocated.
+    pub fn generation(self) -> u64 {
+        self.generation
+    }
+}
+/// One node in the page list.
+#[derive(Debug)]
+pub struct Node {
+    /// Previous page.
+    pub prev: Option<NodeId>,
+    /// Next page.
+    pub next: Option<NodeId>,
+    /// Owned terminal page.
+    pub data: Page,
+    /// Monotonically increasing allocation serial.
+    pub serial: u64,
+}
+/// Untracked cell location, valid until the referenced content is moved.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct Pin {
+    /// Page node.
+    pub node: NodeId,
+    /// Row in the page.
+    pub y: u16,
+    /// Column in the page.
+    pub x: u16,
+    /// History containing this pin was pruned or reset.
+    pub garbage: bool,
+}
+/// Handle into the list-owned tracked-pin slab.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TrackedPin {
+    index: usize,
+    generation: u64,
+}
+#[derive(Debug)]
+struct PinSlot {
+    generation: u64,
+    pin: Option<Pin>,
+}
+/// Viewport anchor.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Viewport {
+    /// Follow the bottom active area.
+    Active,
+    /// Follow the oldest history row.
+    Top,
+    /// Follow the list's internal tracked viewport pin.
+    Pin,
+}
+/// Traversal direction.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Direction {
+    /// Earlier cells, rows, or pages.
+    LeftUp,
+    /// Later cells, rows, or pages.
+    RightDown,
+}
+/// Viewport scroll request.
+#[derive(Debug, Copy, Clone)]
+pub enum Scroll {
+    /// Show the active area.
+    Active,
+    /// Show the oldest history.
+    Top,
+    /// Show an absolute screen row.
+    Row(usize),
+    /// Move by a signed row count.
+    DeltaRow(isize),
+    /// Jump by a signed number of prompts.
+    DeltaPrompt(isize),
+    /// Show a specific row, ignoring its column.
+    Pin(Pin),
+}
+/// Scrollbar geometry in rows.
+#[derive(Debug, Default, Copy, Clone, PartialEq, Eq)]
+pub struct Scrollbar {
+    /// Total scrollable rows.
+    pub total: usize,
+    /// Viewport's offset from the oldest row.
+    pub offset: usize,
+    /// Visible row count.
+    pub len: usize,
+}
+/// Current cursor position in the active area for resize behavior.
+#[derive(Debug, Copy, Clone)]
+pub struct Cursor {
+    /// Cursor column.
+    pub x: u16,
+    /// Cursor row.
+    pub y: u16,
+}
+/// Resize dimensions and text reflow policy.
+#[derive(Debug, Copy, Clone)]
+pub struct Resize {
+    /// New column count, or unchanged.
+    pub cols: Option<u16>,
+    /// New row count, or unchanged.
+    pub rows: Option<u16>,
+    /// Rewrap logical lines when changing columns.
+    pub reflow: bool,
+    /// Cursor position whose surrounding rows should be preserved.
+    pub cursor: Option<Cursor>,
+}
+impl Default for Resize {
+    fn default() -> Self {
+        Self {
+            cols: None,
+            rows: None,
+            reflow: true,
+            cursor: None,
+        }
+    }
+}
+/// Auxiliary capacity dimension to double.
+#[derive(Debug, Copy, Clone)]
+pub enum IncreaseCapacity {
+    /// Style hash-table slots.
+    Styles,
+    /// Grapheme allocation bytes and map entries.
+    GraphemeBytes,
+    /// Hyperlink set and map capacity.
+    HyperlinkBytes,
+    /// Shared string allocation bytes.
+    StringBytes,
+}
+/// Linked pages backed by a reusable node slab and a standard-page pool.
+#[derive(Debug)]
+pub struct PageList {
+    nodes: Vec<Option<Node>>,
+    free_nodes: Vec<usize>,
+    page_pool: Vec<Page>,
+    /// Oldest page.
+    pub first: Option<NodeId>,
+    /// Last active page.
+    pub last: Option<NodeId>,
+    /// Next page serial.
+    pub page_serial: u64,
+    /// Lower bound for still-valid serial numbers.
+    pub page_serial_min: u64,
+    /// Logical allocated page bytes, including standard pool rounding.
+    pub page_size: usize,
+    /// Configured scrollback byte limit.
+    pub explicit_max_size: usize,
+    /// Minimum byte limit needed for the active area and one extra page.
+    pub min_max_size: usize,
+    /// Total allocated visible rows across all pages.
+    pub total_rows: usize,
+    /// Current grid columns.
+    pub cols: u16,
+    /// Active grid rows.
+    pub rows: u16,
+    /// Current viewport anchor.
+    pub viewport: Viewport,
+    pins: Vec<PinSlot>,
+    free_pins: Vec<usize>,
+    viewport_pin: Option<TrackedPin>,
+    pin_serial: u64,
+    pause_checks: usize,
+}
+fn std_size() -> usize {
+    Page::layout(page::STD_CAPACITY).total_size
+}
+fn allocated_size(cap: Capacity) -> usize {
+    Page::layout(cap).total_size.max(std_size())
+}
+fn initial_capacity(cols: u16) -> Capacity {
+    page::STD_CAPACITY
+        .adjust(Adjustment { cols: Some(cols) })
+        .unwrap_or(Capacity {
+            cols,
+            ..page::STD_CAPACITY
+        })
+}
+fn min_max_size(cols: u16, rows: u16) -> usize {
+    (usize::from(rows).div_ceil(usize::from(initial_capacity(cols).rows)) + 1) * std_size()
+}
+impl PageList {
+    /// Create an empty active screen, optionally limiting history in bytes.
+    pub fn init(cols: u16, rows: u16, max_size: Option<usize>) -> Result<Self, Error> {
+        if cols == 0 || rows == 0 {
+            return Err(Error::InvalidDimensions);
+        }
+        let mut s = Self {
+            nodes: Vec::new(),
+            free_nodes: Vec::new(),
+            page_pool: Vec::new(),
+            first: None,
+            last: None,
+            page_serial: 0,
+            page_serial_min: 0,
+            page_size: 0,
+            explicit_max_size: max_size.unwrap_or(usize::MAX),
+            min_max_size: min_max_size(cols, rows),
+            total_rows: 0,
+            cols,
+            rows,
+            viewport: Viewport::Active,
+            pins: Vec::new(),
+            free_pins: Vec::new(),
+            viewport_pin: None,
+            pin_serial: 0,
+            pause_checks: 0,
+        };
+        while s.total_rows < usize::from(rows) {
+            s.grow()?;
+        }
+        let pin = s
+            .get_top_left(Tag::Screen)
+            .ok_or(Error::InvalidCoordinate)?;
+        s.viewport_pin = Some(s.track_pin(pin)?);
+        Ok(s)
+    }
+    /// Retrieve a live node, rejecting stale generations.
+    pub fn node(&self, id: NodeId) -> Option<&Node> {
+        self.nodes
+            .get(id.index)?
+            .as_ref()
+            .filter(|n| n.serial == id.generation)
+    }
+    /// Retrieve a mutable live node, rejecting stale generations.
+    pub fn node_mut(&mut self, id: NodeId) -> Option<&mut Node> {
+        self.nodes
+            .get_mut(id.index)?
+            .as_mut()
+            .filter(|n| n.serial == id.generation)
+    }
+    fn create_node(&mut self, cap: Capacity) -> Result<NodeId, Error> {
+        if Page::layout(cap).total_size > u32::MAX as usize {
+            return Err(Error::OutOfSpace);
+        }
+        self.nodes.try_reserve(1).map_err(|_| Error::OutOfMemory)?;
+        let mut data = if let Some(pos) = self.page_pool.iter().position(|p| p.capacity == cap) {
+            let mut p = self.page_pool.swap_remove(pos);
+            p.reinit()?;
+            p
+        } else {
+            Page::init(cap)?
+        };
+        data.size.rows = 0;
+        let index = self.free_nodes.pop().unwrap_or(self.nodes.len());
+        let serial = self.page_serial;
+        self.page_serial = self.page_serial.wrapping_add(1);
+        let id = NodeId {
+            index,
+            generation: serial,
+        };
+        let node = Node {
+            prev: None,
+            next: None,
+            data,
+            serial,
+        };
+        if index == self.nodes.len() {
+            self.nodes.push(Some(node));
+        } else {
+            self.nodes[index] = Some(node);
+        }
+        self.page_size += allocated_size(cap);
+        Ok(id)
+    }
+    fn insert_after(&mut self, prev: Option<NodeId>, id: NodeId) {
+        let next = prev
+            .and_then(|p| self.node(p).and_then(|n| n.next))
+            .or(if prev.is_none() { self.first } else { None });
+        if let Some(n) = self.node_mut(id) {
+            n.prev = prev;
+            n.next = next;
+        }
+        if let Some(p) = prev {
+            if let Some(n) = self.node_mut(p) {
+                n.next = Some(id);
+            }
+        } else {
+            self.first = Some(id);
+        }
+        if let Some(p) = next {
+            if let Some(n) = self.node_mut(p) {
+                n.prev = Some(id);
+            }
+        } else {
+            self.last = Some(id);
+        }
+    }
+    fn detach(&mut self, id: NodeId) -> Option<Node> {
+        let n = self.node(id)?;
+        let (prev, next) = (n.prev, n.next);
+        if let Some(p) = prev {
+            self.node_mut(p)?.next = next;
+        } else {
+            self.first = next;
+        }
+        if let Some(p) = next {
+            self.node_mut(p)?.prev = prev;
+        } else {
+            self.last = prev;
+        }
+        let n = self.nodes[id.index].take()?;
+        self.page_size -= allocated_size(n.data.capacity);
+        self.free_nodes.push(id.index);
+        Some(n)
+    }
+    fn recycle(&mut self, node: Node) {
+        if Page::layout(node.data.capacity).total_size <= std_size() {
+            self.page_pool.push(node.data);
+        }
+    }
+    fn active_offset(&self) -> usize {
+        self.total_rows.saturating_sub(usize::from(self.rows))
+    }
+    fn screen_row(&self, p: Pin) -> Option<usize> {
+        if !self.pin_is_valid(p) {
+            return None;
+        }
+        let mut id = self.first;
+        let mut y = 0;
+        while let Some(i) = id {
+            let n = self.node(i)?;
+            if i == p.node {
+                return Some(y + usize::from(p.y));
+            }
+            y += usize::from(n.data.size.rows);
+            id = n.next;
+        }
+        None
+    }
+    fn pin_at(&self, mut y: usize, x: u16) -> Option<Pin> {
+        if x >= self.cols {
+            return None;
+        }
+        let mut id = self.first;
+        while let Some(i) = id {
+            let n = self.node(i)?;
+            if y < usize::from(n.data.size.rows) {
+                return Some(Pin {
+                    node: i,
+                    y: y as u16,
+                    x,
+                    garbage: false,
+                });
+            }
+            y -= usize::from(n.data.size.rows);
+            id = n.next;
+        }
+        None
+    }
+    /// Current viewport's absolute row offset.
+    pub fn viewport_row_offset(&self) -> usize {
+        match self.viewport {
+            Viewport::Active => self.active_offset(),
+            Viewport::Top => 0,
+            Viewport::Pin => self
+                .viewport_pin
+                .and_then(|h| self.tracked_pin(h))
+                .and_then(|p| self.screen_row(p))
+                .unwrap_or(0),
+        }
+    }
+    fn bounds(&self, tag: Tag) -> (usize, usize) {
+        match tag {
+            Tag::Screen => (0, self.total_rows),
+            Tag::History => (0, self.active_offset()),
+            Tag::Active => (self.active_offset(), self.total_rows),
+            Tag::Viewport => {
+                let start = self.viewport_row_offset();
+                (start, (start + usize::from(self.rows)).min(self.total_rows))
+            }
+        }
+    }
+    /// Map a tagged coordinate to an untracked pin.
+    pub fn pin(&self, pt: Point) -> Option<Pin> {
+        let (start, end) = self.bounds(pt.tag());
+        let c = pt.coord();
+        let y = start.checked_add(c.y as usize)?;
+        if y >= end {
+            return None;
+        }
+        self.pin_at(y, c.x)
+    }
+    /// Convert a pin to a coordinate in a reference frame, if inside it.
+    pub fn point_from_pin(&self, tag: Tag, p: Pin) -> Option<Point> {
+        let y = self.screen_row(p)?;
+        let (start, end) = self.bounds(tag);
+        if y < start || y >= end {
+            return None;
+        }
+        Some(Point::new(
+            tag,
+            Coordinate {
+                x: p.x,
+                y: (y - start) as u32,
+            },
+        ))
+    }
+    /// Top-left coordinate in a reference frame, if the region exists.
+    pub fn get_top_left(&self, tag: Tag) -> Option<Pin> {
+        self.pin(Point::new(tag, Coordinate::default()))
+    }
+    /// Bottom-right coordinate in a reference frame, if the region exists.
+    pub fn get_bottom_right(&self, tag: Tag) -> Option<Pin> {
+        let (start, end) = self.bounds(tag);
+        if start == end {
+            return None;
+        }
+        self.pin_at(end - 1, self.cols - 1)
+    }
+    /// Check the generation and logical coordinates of a pin.
+    pub fn pin_is_valid(&self, p: Pin) -> bool {
+        self.node(p.node)
+            .is_some_and(|n| p.x < n.data.size.cols && p.y < n.data.size.rows)
+    }
+    /// Register an independently owned location updated by every mutation.
+    pub fn track_pin(&mut self, p: Pin) -> Result<TrackedPin, Error> {
+        if !self.pin_is_valid(p) {
+            return Err(Error::InvalidCoordinate);
+        }
+        self.pins.try_reserve(1).map_err(|_| Error::OutOfMemory)?;
+        let index = self.free_pins.pop().unwrap_or(self.pins.len());
+        let generation = self.pin_serial;
+        self.pin_serial = self.pin_serial.wrapping_add(1);
+        let slot = PinSlot {
+            generation,
+            pin: Some(p),
+        };
+        if index == self.pins.len() {
+            self.pins.push(slot);
+        } else {
+            self.pins[index] = slot;
+        }
+        Ok(TrackedPin { index, generation })
+    }
+    /// Read a tracked location. Stale handles return None.
+    pub fn tracked_pin(&self, h: TrackedPin) -> Option<Pin> {
+        self.pins
+            .get(h.index)
+            .filter(|s| s.generation == h.generation)?
+            .pin
+    }
+    /// Update a tracked location to another valid cell.
+    pub fn set_tracked_pin(&mut self, h: TrackedPin, p: Pin) -> Result<(), Error> {
+        if !self.pin_is_valid(p) {
+            return Err(Error::InvalidCoordinate);
+        }
+        let slot = self
+            .pins
+            .get_mut(h.index)
+            .filter(|s| s.generation == h.generation && s.pin.is_some())
+            .ok_or(Error::InvalidId)?;
+        slot.pin = Some(p);
+        Ok(())
+    }
+    /// Release a tracked handle. The internal viewport handle remains owned.
+    pub fn untrack_pin(&mut self, h: TrackedPin) {
+        if self.viewport_pin == Some(h) {
+            return;
+        }
+        if let Some(s) = self
+            .pins
+            .get_mut(h.index)
+            .filter(|s| s.generation == h.generation && s.pin.is_some())
+        {
+            s.pin = None;
+            self.free_pins.push(h.index);
+        }
+    }
+    /// Count all tracked pins, including the internal viewport pin.
+    pub fn count_tracked_pins(&self) -> usize {
+        self.pins.iter().filter(|s| s.pin.is_some()).count()
+    }
+    /// Iterate tracked handles and their current locations.
+    pub fn tracked_pins(&self) -> impl Iterator<Item = (TrackedPin, Pin)> + '_ {
+        self.pins.iter().enumerate().filter_map(|(index, s)| {
+            s.pin.map(|p| {
+                (
+                    TrackedPin {
+                        index,
+                        generation: s.generation,
+                    },
+                    p,
+                )
+            })
+        })
+    }
+    /// Actual byte ceiling heuristic, including the minimum active allocation.
+    pub fn max_size(&self) -> usize {
+        self.explicit_max_size.max(self.min_max_size)
+    }
+    /// Add exactly one row, pruning one whole history page when necessary.
+    pub fn grow(&mut self) -> Result<Option<NodeId>, Error> {
+        if let Some(last) = self.last
+            && let Some(n) = self.node_mut(last)
+            && n.data.size.rows < n.data.capacity.rows
+        {
+            n.data.size.rows += 1;
+            self.total_rows += 1;
+            return Ok(None);
+        }
+        let cap = initial_capacity(self.cols);
+        if let (Some(first), Some(last)) = (self.first, self.last)
+            && first != last
+            && self.page_size.saturating_add(std_size()) > self.max_size()
+        {
+            let n = self.node(first).ok_or(Error::InvalidId)?;
+            let removed = usize::from(n.data.size.rows);
+            let next = n.next;
+            if self.total_rows - removed + 1 >= usize::from(self.rows) {
+                let viewport = self.viewport_row_offset();
+                let n = self.detach(first).ok_or(Error::InvalidId)?;
+                self.total_rows -= removed;
+                self.page_serial_min = n.serial.wrapping_add(1);
+                self.recycle(n);
+                if let Some(next) = next {
+                    for slot in &mut self.pins {
+                        if let Some(p) = &mut slot.pin
+                            && p.node == first
+                        {
+                            *p = Pin {
+                                node: next,
+                                x: 0,
+                                y: 0,
+                                garbage: true,
+                            };
+                        }
+                    }
+                }
+                if self.viewport == Viewport::Pin && viewport < removed {
+                    self.viewport = Viewport::Top;
+                }
+                if let Some(h) = self.viewport_pin
+                    && let Some(p) = self.pins[h.index].pin.as_mut()
+                {
+                    p.garbage = false;
+                }
+            }
+        }
+        let id = self.create_node(cap)?;
+        self.insert_after(self.last, id);
+        self.node_mut(id).ok_or(Error::InvalidId)?.data.size.rows = 1;
+        self.total_rows += 1;
+        Ok(Some(id))
+    }
+    /// Return scrollbar geometry, hiding history when scrollback is disabled.
+    pub fn scrollbar(&self) -> Scrollbar {
+        if self.explicit_max_size == 0 {
+            Scrollbar {
+                total: usize::from(self.rows),
+                offset: 0,
+                len: usize::from(self.rows),
+            }
+        } else {
+            Scrollbar {
+                total: self.total_rows,
+                offset: self.viewport_row_offset(),
+                len: usize::from(self.rows),
+            }
+        }
+    }
+    /// Move the viewport without allocating pages or creating history.
+    pub fn scroll(&mut self, behavior: Scroll) {
+        if self.explicit_max_size == 0 {
+            self.viewport = Viewport::Active;
+            return;
+        }
+        let row = match behavior {
+            Scroll::Active => {
+                self.viewport = Viewport::Active;
+                return;
+            }
+            Scroll::Top => {
+                self.viewport = Viewport::Top;
+                return;
+            }
+            Scroll::Row(y) => y,
+            Scroll::DeltaRow(d) => self.viewport_row_offset().saturating_add_signed(d),
+            Scroll::Pin(p) => {
+                let Some(y) = self.screen_row(p) else {
+                    return;
+                };
+                y
+            }
+            Scroll::DeltaPrompt(d) => {
+                if d == 0 {
+                    return;
+                }
+                let current = self.viewport_row_offset();
+                let mut prompts: Vec<_> = self
+                    .prompt_iterator(
+                        Direction::RightDown,
+                        Point::Screen(Coordinate::default()),
+                        None,
+                    )
+                    .filter_map(|p| self.screen_row(p))
+                    .filter(|y| if d < 0 { *y < current } else { *y > current })
+                    .collect();
+                if d < 0 {
+                    prompts.reverse();
+                }
+                let Some(&y) = prompts.get(
+                    d.unsigned_abs()
+                        .saturating_sub(1)
+                        .min(prompts.len().saturating_sub(1)),
+                ) else {
+                    return;
+                };
+                y
+            }
+        };
+        if row >= self.active_offset() {
+            self.viewport = Viewport::Active;
+        } else if row == 0 {
+            self.viewport = Viewport::Top;
+        } else if let (Some(p), Some(h)) = (self.pin_at(row, 0), self.viewport_pin) {
+            self.pins[h.index].pin = Some(p);
+            self.viewport = Viewport::Pin;
+        }
+    }
+    fn fixup_viewport(&mut self) {
+        if self.viewport == Viewport::Pin && self.viewport_row_offset() >= self.active_offset() {
+            self.viewport = Viewport::Active;
+        }
+    }
+    /// Read a cell without copying its managed auxiliary values.
+    pub fn get_cell(&self, pt: Point) -> Option<Cell> {
+        let p = self.pin(pt)?;
+        Some(
+            self.node(p.node)?
+                .data
+                .get_row_and_cell(usize::from(p.x), usize::from(p.y))?
+                .1
+                .to_owned(),
+        )
+    }
+    /// Access a cell mutably; callers maintain managed metadata and dirty flags.
+    pub fn get_cell_mut(&mut self, pt: Point) -> Option<&mut Cell> {
+        let p = self.pin(pt)?;
+        let page = &mut self.node_mut(p.node)?.data;
+        let i = page.cell_index(usize::from(p.x), usize::from(p.y)).ok()?;
+        page.cells.get_mut(i)
+    }
+    /// Number of live pages in list order.
+    pub fn total_pages(&self) -> usize {
+        self.nodes.iter().filter(|n| n.is_some()).count()
+    }
+    /// Clear full-page and individual-row dirty flags.
+    pub fn clear_dirty(&mut self) {
+        for n in self.nodes.iter_mut().flatten() {
+            n.data.dirty = false;
+            for r in &mut n.data.rows {
+                r.set_dirty(false);
+            }
+        }
+    }
+    /// Whether a coordinate's page or row needs redraw.
+    pub fn is_dirty(&self, pt: Point) -> bool {
+        self.pin(pt).is_some_and(|p| p.is_dirty(self))
+    }
+    /// Split before the pin's row, preserving metadata and remapping tracked pins.
+    pub fn split(&mut self, p: Pin) -> Result<(), Error> {
+        let page = &self.node(p.node).ok_or(Error::InvalidId)?.data;
+        if page.size.rows <= 1 {
+            return Err(Error::OutOfSpace);
+        }
+        if p.y == 0 {
+            return Ok(());
+        }
+        if p.y >= page.size.rows {
+            return Err(Error::InvalidCoordinate);
+        }
+        let mut copy = Page::init(page.capacity)?;
+        copy.size = page.size;
+        copy.size.rows -= p.y;
+        copy.clone_from(page, usize::from(p.y), usize::from(page.size.rows))?;
+        copy.dirty = page.dirty;
+        let id = self.create_node(copy.capacity)?;
+        self.node_mut(id).ok_or(Error::InvalidId)?.data = copy;
+        self.insert_after(Some(p.node), id);
+        let src = &mut self.node_mut(p.node).ok_or(Error::InvalidId)?.data;
+        for y in usize::from(p.y)..usize::from(src.size.rows) {
+            src.clear_cells(y, 0, usize::from(src.size.cols), false)?;
+        }
+        src.size.rows = p.y;
+        for s in &mut self.pins {
+            if let Some(pin) = &mut s.pin
+                && pin.node == p.node
+                && pin.y >= p.y
+            {
+                pin.node = id;
+                pin.y -= p.y;
+            }
+        }
+        Ok(())
+    }
+    fn replace_page(&mut self, old: NodeId, page: Page) -> Result<NodeId, Error> {
+        let prev = self.node(old).ok_or(Error::InvalidId)?.prev;
+        let id = self.create_node(page.capacity)?;
+        self.node_mut(id).ok_or(Error::InvalidId)?.data = page;
+        self.insert_after(prev, id);
+        let n = self.detach(old).ok_or(Error::InvalidId)?;
+        self.recycle(n);
+        for slot in &mut self.pins {
+            if let Some(p) = &mut slot.pin
+                && p.node == old
+            {
+                p.node = id;
+            }
+        }
+        Ok(id)
+    }
+    /// Double an auxiliary capacity, or rebuild unchanged to reclaim dead IDs.
+    pub fn increase_capacity(
+        &mut self,
+        id: NodeId,
+        adjustment: Option<IncreaseCapacity>,
+    ) -> Result<NodeId, Error> {
+        let old = &self.node(id).ok_or(Error::InvalidId)?.data;
+        let mut cap = old.capacity;
+
+        match adjustment {
+            Some(IncreaseCapacity::Styles) => cap.styles = double16(cap.styles)?,
+            Some(IncreaseCapacity::GraphemeBytes) => {
+                cap.grapheme_bytes = double32(cap.grapheme_bytes)?;
+            }
+            Some(IncreaseCapacity::HyperlinkBytes) => {
+                cap.hyperlink_bytes = double16(cap.hyperlink_bytes)?;
+            }
+            Some(IncreaseCapacity::StringBytes) => cap.string_bytes = double32(cap.string_bytes)?,
+            None => {}
+        }
+        if Page::layout(cap).total_size > u32::MAX as usize {
+            return Err(Error::OutOfSpace);
+        }
+        let mut page = Page::init(cap)?;
+        page.size = old.size;
+        page.clone_from(old, 0, usize::from(old.size.rows))?;
+        page.dirty = old.dirty;
+        self.replace_page(id, page)
+    }
+    /// Alias for capacity adjustment used by higher-level screen code.
+    pub fn adjust_capacity(
+        &mut self,
+        id: NodeId,
+        adjustment: Option<IncreaseCapacity>,
+    ) -> Result<NodeId, Error> {
+        self.increase_capacity(id, adjustment)
+    }
+    /// Compact oversized pages when a smaller logical allocation is possible.
+    pub fn compact(&mut self, id: NodeId) -> Result<Option<NodeId>, Error> {
+        let old = &self.node(id).ok_or(Error::InvalidId)?.data;
+        if Page::layout(old.capacity).total_size <= std_size() {
+            return Ok(None);
+        }
+        let cap = old.exact_row_capacity(0, usize::from(old.size.rows))?;
+        if Page::layout(cap).total_size >= Page::layout(old.capacity).total_size {
+            return Ok(None);
+        }
+        let mut page = Page::init(cap)?;
+        page.size = old.size;
+        if page.clone_from(old, 0, usize::from(old.size.rows)).is_err() {
+            return Ok(None);
+        }
+        page.dirty = old.dirty;
+        self.replace_page(id, page).map(Some)
+    }
+    fn erase_range(&mut self, start: usize, end: usize) -> Result<(), Error> {
+        if start > end || end > self.total_rows {
+            return Err(Error::InvalidCoordinate);
+        }
+        if start == end {
+            return Ok(());
+        }
+        let coords: Vec<_> = self
+            .tracked_pins()
+            .filter_map(|(h, p)| self.screen_row(p).map(|y| (h, p, y)))
+            .collect();
+        let mut id = self.first;
+        let mut offset = 0;
+        while let Some(i) = id {
+            let n = self.node(i).ok_or(Error::InvalidId)?;
+            id = n.next;
+            let count = usize::from(n.data.size.rows);
+            let a = start.saturating_sub(offset).min(count);
+            let b = end.saturating_sub(offset).min(count);
+            offset += count;
+            if a == b {
+                continue;
+            }
+            if a == 0 && b == count && self.first != self.last {
+                let n = self.detach(i).ok_or(Error::InvalidId)?;
+                self.recycle(n);
+            } else {
+                let p = &mut self.node_mut(i).ok_or(Error::InvalidId)?.data;
+                for y in a..b {
+                    p.clear_cells(y, 0, usize::from(p.size.cols), false)?;
+                }
+                p.rows[a..count].rotate_left(b - a);
+                p.size.rows -= (b - a) as u16;
+                for r in &mut p.rows[a..usize::from(p.size.rows)] {
+                    r.set_dirty(true);
+                }
+            }
+        }
+        self.total_rows -= end - start;
+        if self.total_rows == 0 {
+            self.grow()?;
+        }
+        for (h, old, y) in coords {
+            let erased = y >= start && y < end;
+            let mapped_y = if y < start {
+                y
+            } else if y >= end {
+                y - (end - start)
+            } else {
+                start.min(self.total_rows - 1)
+            };
+            let mut p = self
+                .pin_at(mapped_y, if erased { 0 } else { old.x })
+                .ok_or(Error::InvalidCoordinate)?;
+            p.garbage = old.garbage;
+            self.pins[h.index].pin = Some(p);
+        }
+        self.fixup_viewport();
+        Ok(())
+    }
+    /// Remove an inclusive row range, regrowing erased active rows.
+    pub fn erase_rows(&mut self, start: Point, end: Option<Point>) -> Result<(), Error> {
+        let a = self
+            .pin(start)
+            .and_then(|p| self.screen_row(p))
+            .ok_or(Error::InvalidCoordinate)?;
+        let b = if let Some(end) = end {
+            self.pin(end)
+                .and_then(|p| self.screen_row(p))
+                .ok_or(Error::InvalidCoordinate)?
+                + 1
+        } else {
+            self.bounds(start.tag()).1
+        };
+        self.erase_range(a, b)?;
+        while self.total_rows < usize::from(self.rows) {
+            self.grow()?;
+        }
+        Ok(())
+    }
+    /// Remove one row, shifting following rows without changing page dimensions.
+    pub fn erase_row(&mut self, pt: Point) -> Result<(), Error> {
+        let p = self.pin(pt).ok_or(Error::InvalidCoordinate)?;
+        let y = self.screen_row(p).ok_or(Error::InvalidCoordinate)?;
+        let stationary: Vec<_> = self
+            .tracked_pins()
+            .filter(|(_, q)| q.node == p.node && q.y == p.y)
+            .collect();
+        self.erase_row_bounded(pt, self.total_rows - y - 1)?;
+        for (h, p) in stationary {
+            self.pins[h.index].pin = Some(p);
+        }
+        Ok(())
+    }
+    /// Remove a row and shift at most `limit` following rows, blanking the last.
+    pub fn erase_row_bounded(&mut self, pt: Point, limit: usize) -> Result<(), Error> {
+        let first = self.pin(pt).ok_or(Error::InvalidCoordinate)?;
+        let start = self.screen_row(first).ok_or(Error::InvalidCoordinate)?;
+        let end = start.saturating_add(limit).min(self.total_rows - 1);
+        let old_pins: Vec<_> = self
+            .tracked_pins()
+            .filter_map(|(h, p)| self.screen_row(p).map(|y| (h, p, y)))
+            .collect();
+        let mut current = first;
+        loop {
+            let node = self.node(current.node).ok_or(Error::InvalidId)?;
+            let offset = self
+                .screen_row(Pin { y: 0, ..current })
+                .ok_or(Error::InvalidCoordinate)?;
+            let stop = (end - offset + 1).min(usize::from(node.data.size.rows));
+            let next = node.next;
+            let has_next = offset + stop <= end;
+            // Rotation moves only compact row metadata and keeps cell indices stable.
+            let page = &mut self.node_mut(current.node).ok_or(Error::InvalidId)?.data;
+            page.rows[usize::from(current.y)..stop].rotate_left(1);
+            page.dirty = true;
+            if !has_next {
+                page.clear_cells(stop - 1, 0, usize::from(page.size.cols), false)?;
+                break;
+            }
+            let next = next.ok_or(Error::InvalidId)?;
+            let source = &self.node(next).ok_or(Error::InvalidId)?.data;
+            let row = source.rows[0];
+            let values: Vec<_> = (row.cells()..row.cells() + usize::from(source.size.cols))
+                .map(|i| source.export_cell(i))
+                .collect();
+            let dest = &mut self.node_mut(current.node).ok_or(Error::InvalidId)?.data;
+            dest.clear_cells(stop - 1, 0, usize::from(dest.size.cols), false)?;
+            for (x, value) in values.iter().enumerate() {
+                dest.import_cell(x, stop - 1, value)?;
+            }
+            let cells = dest.rows[stop - 1].cells();
+            dest.rows[stop - 1] = row;
+            dest.rows[stop - 1].set_cells(cells);
+            current = Pin {
+                node: next,
+                y: 0,
+                x: 0,
+                garbage: false,
+            };
+        }
+        for (h, old, y) in old_pins {
+            if y >= start && y <= end {
+                let mut p = self
+                    .pin_at(y.saturating_sub(1), if y == 0 { 0 } else { old.x })
+                    .ok_or(Error::InvalidCoordinate)?;
+                p.garbage = old.garbage;
+                self.pins[h.index].pin = Some(p);
+            }
+        }
+        self.fixup_viewport();
+        Ok(())
+    }
+    /// Remove cells within a rectangular row region, shifting rows upward.
+    pub fn erase_cells_bounded(
+        &mut self,
+        start: Pin,
+        end: Pin,
+        left: u16,
+        right: u16,
+    ) -> Result<(), Error> {
+        let a = self.screen_row(start).ok_or(Error::InvalidCoordinate)?;
+        let b = self.screen_row(end).ok_or(Error::InvalidCoordinate)?;
+        if a > b || left > right || right >= self.cols {
+            return Err(Error::InvalidCoordinate);
+        }
+        for y in a..b {
+            let src = self.pin_at(y + 1, left).ok_or(Error::InvalidCoordinate)?;
+            let dst = self.pin_at(y, left).ok_or(Error::InvalidCoordinate)?;
+            let data: Vec<_> = {
+                let page = &self.node(src.node).ok_or(Error::InvalidId)?.data;
+                (left..=right)
+                    .map(|x| {
+                        page.export_cell(page.rows[usize::from(src.y)].cells() + usize::from(x))
+                    })
+                    .collect()
+            };
+            for (x, v) in data.iter().enumerate() {
+                self.node_mut(dst.node)
+                    .ok_or(Error::InvalidId)?
+                    .data
+                    .import_cell(usize::from(left) + x, usize::from(dst.y), v)?;
+            }
+        }
+        let p = self.pin_at(b, left).ok_or(Error::InvalidCoordinate)?;
+        self.node_mut(p.node)
+            .ok_or(Error::InvalidId)?
+            .data
+            .clear_cells(
+                usize::from(p.y),
+                usize::from(left),
+                usize::from(right) + 1,
+                false,
+            )?;
+        let changes: Vec<_> = self
+            .tracked_pins()
+            .filter_map(|(h, p)| {
+                self.screen_row(p)
+                    .filter(|y| *y >= a && *y <= b && p.x >= left && p.x <= right)
+                    .map(|y| (h, p, y))
+            })
+            .collect();
+        for (h, p, y) in changes {
+            if let Some(mut new) = self.pin_at(y.saturating_sub(1).max(a), p.x) {
+                new.garbage = p.garbage;
+                self.pins[h.index].pin = Some(new);
+            }
+        }
+        self.fixup_viewport();
+        Ok(())
+    }
+    /// Reset to empty active rows and mark every external tracked pin garbage.
+    pub fn reset(&mut self) -> Result<(), Error> {
+        let handles: Vec<_> = self.tracked_pins().map(|(h, _)| h).collect();
+        let mut id = self.first;
+        while let Some(i) = id {
+            let n = self.node(i).ok_or(Error::InvalidId)?;
+            id = n.next;
+            let n = self.detach(i).ok_or(Error::InvalidId)?;
+            self.recycle(n);
+        }
+        self.total_rows = 0;
+        self.viewport = Viewport::Active;
+        while self.total_rows < usize::from(self.rows) {
+            self.grow()?;
+        }
+        let p = self
+            .get_top_left(Tag::Screen)
+            .ok_or(Error::InvalidCoordinate)?;
+        for h in handles {
+            self.pins[h.index].pin = Some(Pin {
+                garbage: self.viewport_pin != Some(h),
+                ..p
+            });
+        }
+        Ok(())
+    }
+    /// Scroll the nonempty portion of the active area into history.
+    pub fn scroll_clear(&mut self) -> Result<(), Error> {
+        let count = self
+            .row_iterator(
+                Direction::LeftUp,
+                Point::Active(Coordinate::default()),
+                None,
+            )
+            .find(|p| {
+                self.node(p.node)
+                    .and_then(|n| n.data.get_cells(usize::from(p.y)))
+                    .is_some_and(|cells| cells.iter().any(|c| !c.is_empty()))
+            })
+            .and_then(|p| self.point_from_pin(Tag::Active, p))
+            .map_or(0, |p| p.coord().y as usize + 1);
+        for _ in 0..count {
+            self.grow()?;
+        }
+        Ok(())
+    }
+    /// Erase all scrollback while preserving the active area.
+    pub fn clear_history(&mut self) -> Result<(), Error> {
+        let end = self.active_offset();
+        self.erase_range(0, end)?;
+        self.viewport = Viewport::Active;
+        Ok(())
+    }
+    /// Nestable suspension of debug integrity checks.
+    pub fn pause_integrity_checks(&mut self, pause: bool) {
+        if pause {
+            self.pause_checks += 1;
+        } else {
+            self.pause_checks = self.pause_checks.saturating_sub(1);
+        }
+    }
+}
+/// Result of moving vertically past a list boundary.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Overflow {
+    /// Movement remained in the screen.
+    Offset(Pin),
+    /// Movement reached an edge with rows still remaining.
+    Overflow {
+        /// Last valid position, retaining the original column.
+        end: Pin,
+        /// Number of rows beyond the boundary.
+        remaining: usize,
+    },
+}
+/// Which part of a pin's row to expose.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum CellSubset {
+    /// Entire visible row.
+    All,
+    /// Columns up to and including the pin.
+    Left,
+    /// Pin column and all columns to its right.
+    Right,
+}
+impl Pin {
+    /// Read a visible row subset without copying or allocating.
+    pub fn cells(self, list: &PageList, subset: CellSubset) -> Option<&[Cell]> {
+        let cells = list.node(self.node)?.data.get_cells(usize::from(self.y))?;
+        match subset {
+            CellSubset::All => Some(cells),
+            CellSubset::Left => cells.get(..=usize::from(self.x)),
+            CellSubset::Right => cells.get(usize::from(self.x)..),
+        }
+    }
+    /// Move upward, returning the edge and unconsumed distance on overflow.
+    pub fn up_overflow(self, list: &PageList, n: usize) -> Option<Overflow> {
+        let y = list.screen_row(self)?;
+        if n <= y {
+            Some(Overflow::Offset(self.up(list, n)?))
+        } else {
+            Some(Overflow::Overflow {
+                end: list.pin_at(0, self.x)?,
+                remaining: n - y,
+            })
+        }
+    }
+    /// Move downward, returning the edge and unconsumed distance on overflow.
+    pub fn down_overflow(self, list: &PageList, n: usize) -> Option<Overflow> {
+        let y = list.screen_row(self)?;
+        let available = list.total_rows - y - 1;
+        if n <= available {
+            Some(Overflow::Offset(self.down(list, n)?))
+        } else {
+            Some(Overflow::Overflow {
+                end: list.pin_at(list.total_rows - 1, self.x)?,
+                remaining: n - available,
+            })
+        }
+    }
+    /// Compare page and coordinates, ignoring garbage state.
+    pub fn eql(self, other: Self) -> bool {
+        self.node == other.node && self.x == other.x && self.y == other.y
+    }
+    /// Read the row and cell from the owning list.
+    pub fn row_and_cell(self, list: &PageList) -> Option<(&Row, &Cell)> {
+        list.node(self.node)?
+            .data
+            .get_row_and_cell(usize::from(self.x), usize::from(self.y))
+    }
+    /// Whether the row or page requires redraw.
+    pub fn is_dirty(self, list: &PageList) -> bool {
+        list.node(self.node).is_some_and(|n| {
+            n.data.dirty
+                || n.data
+                    .get_row(usize::from(self.y))
+                    .is_some_and(|r| r.dirty())
+        })
+    }
+    /// Mark the referenced row dirty.
+    pub fn mark_dirty(self, list: &mut PageList) {
+        if let Some(r) = list
+            .node_mut(self.node)
+            .and_then(|n| n.data.get_row_mut(usize::from(self.y)))
+        {
+            r.set_dirty(true);
+        }
+    }
+    /// Resolve the current cell's style.
+    pub fn style(self, list: &PageList) -> Option<crate::style::Style> {
+        let page = &list.node(self.node)?.data;
+        Some(
+            page.style(
+                *page
+                    .get_row_and_cell(usize::from(self.x), usize::from(self.y))?
+                    .1,
+            ),
+        )
+    }
+    /// Resolve the current cell's extra codepoints.
+    pub fn grapheme(self, list: &PageList) -> Option<&[u32]> {
+        let page = &list.node(self.node)?.data;
+        page.lookup_grapheme(
+            page.cell_index(usize::from(self.x), usize::from(self.y))
+                .ok()?,
+        )
+    }
+    /// Move left within a row, rejecting out-of-range movement.
+    pub fn left(self, n: usize) -> Option<Self> {
+        Some(Self {
+            x: self.x.checked_sub(u16::try_from(n).ok()?)?,
+            ..self
+        })
+    }
+    /// Move right within a row, rejecting out-of-range movement.
+    pub fn right(self, list: &PageList, n: usize) -> Option<Self> {
+        let x = usize::from(self.x).checked_add(n)?;
+        if x >= usize::from(list.cols) {
+            None
+        } else {
+            Some(Self {
+                x: x as u16,
+                ..self
+            })
+        }
+    }
+    /// Move left, clamping to column zero.
+    pub fn left_clamp(self, n: u16) -> Self {
+        Self {
+            x: self.x.saturating_sub(n),
+            ..self
+        }
+    }
+    /// Move right, clamping to the last column.
+    pub fn right_clamp(self, list: &PageList, n: u16) -> Self {
+        Self {
+            x: self.x.saturating_add(n).min(list.cols - 1),
+            ..self
+        }
+    }
+    /// Move up across page boundaries while preserving the column.
+    pub fn up(self, list: &PageList, mut n: usize) -> Option<Self> {
+        let mut p = self;
+        loop {
+            if n <= usize::from(p.y) {
+                p.y -= n as u16;
+                return Some(p);
+            }
+            n -= usize::from(p.y) + 1;
+            p.node = list.node(p.node)?.prev?;
+            p.y = list.node(p.node)?.data.size.rows.checked_sub(1)?;
+        }
+    }
+    /// Move down across page boundaries while preserving the column.
+    pub fn down(self, list: &PageList, mut n: usize) -> Option<Self> {
+        let mut p = self;
+        loop {
+            let rem = usize::from(list.node(p.node)?.data.size.rows - p.y - 1);
+            if n <= rem {
+                p.y += n as u16;
+                return Some(p);
+            }
+            n -= rem + 1;
+            p.node = list.node(p.node)?.next?;
+            p.y = 0;
+        }
+    }
+    /// Move left in row-major order, wrapping to previous rows.
+    pub fn left_wrap(self, list: &PageList, n: usize) -> Option<Self> {
+        let cols = usize::from(list.cols);
+        let x = usize::from(self.x);
+        if n <= x {
+            return self.left(n);
+        }
+        let delta = n - x;
+        let rows = delta.div_ceil(cols);
+        let mut p = self.up(list, rows)?;
+        p.x = ((cols - delta % cols) % cols) as u16;
+        Some(p)
+    }
+    /// Move right in row-major order, wrapping to following rows.
+    pub fn right_wrap(self, list: &PageList, n: usize) -> Option<Self> {
+        let x = usize::from(self.x).checked_add(n)?;
+        let cols = usize::from(list.cols);
+        let mut p = self.down(list, x / cols)?;
+        p.x = (x % cols) as u16;
+        Some(p)
+    }
+    /// Whether this pin precedes another pin in row-major screen order.
+    pub fn before(self, list: &PageList, other: Self) -> bool {
+        match (list.screen_row(self), list.screen_row(other)) {
+            (Some(a), Some(b)) => (a, self.x) < (b, other.x),
+            _ => false,
+        }
+    }
+    /// Whether this pin lies between inclusive endpoints.
+    pub fn is_between(self, list: &PageList, top: Self, bottom: Self) -> bool {
+        (self.eql(top) || top.before(list, self)) && (self.eql(bottom) || self.before(list, bottom))
+    }
+    /// Move diagonally by signed row and column deltas, clamping columns.
+    pub fn diagonal(self, list: &PageList, dx: isize, dy: isize) -> Option<Self> {
+        let mut p = if dy < 0 {
+            self.up(list, dy.unsigned_abs())?
+        } else {
+            self.down(list, dy as usize)?
+        };
+        p.x = usize::from(p.x)
+            .saturating_add_signed(dx)
+            .min(usize::from(list.cols - 1)) as u16;
+        Some(p)
+    }
+}
+/// A double-ended cell iterator yielding stable untracked locations.
+pub struct CellIterator<'a> {
+    list: &'a PageList,
+    front: Option<Pin>,
+    back: Option<Pin>,
+    direction: Direction,
+}
+impl CellIterator<'_> {
+    fn take_front(&mut self) -> Option<Pin> {
+        let p = self.front?;
+        if self.back.is_some_and(|b| p.eql(b)) {
+            self.front = None;
+            self.back = None;
+        } else {
+            self.front = p.right_wrap(self.list, 1);
+        }
+        Some(p)
+    }
+    fn take_back(&mut self) -> Option<Pin> {
+        let p = self.back?;
+        if self.front.is_some_and(|a| p.eql(a)) {
+            self.front = None;
+            self.back = None;
+        } else {
+            self.back = p.left_wrap(self.list, 1);
+        }
+        Some(p)
+    }
+}
+impl Iterator for CellIterator<'_> {
+    type Item = Pin;
+    fn next(&mut self) -> Option<Pin> {
+        if self.direction == Direction::RightDown {
+            self.take_front()
+        } else {
+            self.take_back()
+        }
+    }
+}
+impl DoubleEndedIterator for CellIterator<'_> {
+    fn next_back(&mut self) -> Option<Pin> {
+        if self.direction == Direction::RightDown {
+            self.take_back()
+        } else {
+            self.take_front()
+        }
+    }
+}
+/// A double-ended row iterator yielding column-zero pins.
+pub struct RowIterator<'a> {
+    list: &'a PageList,
+    front: Option<Pin>,
+    back: Option<Pin>,
+    direction: Direction,
+}
+impl RowIterator<'_> {
+    fn take_front(&mut self) -> Option<Pin> {
+        let p = self.front?;
+        if self.back.is_some_and(|b| p.eql(b)) {
+            self.front = None;
+            self.back = None;
+        } else {
+            self.front = p.down(self.list, 1);
+        }
+        Some(p)
+    }
+    fn take_back(&mut self) -> Option<Pin> {
+        let p = self.back?;
+        if self.front.is_some_and(|a| p.eql(a)) {
+            self.front = None;
+            self.back = None;
+        } else {
+            self.back = p.up(self.list, 1);
+        }
+        Some(p)
+    }
+}
+impl Iterator for RowIterator<'_> {
+    type Item = Pin;
+    fn next(&mut self) -> Option<Pin> {
+        if self.direction == Direction::RightDown {
+            self.take_front()
+        } else {
+            self.take_back()
+        }
+    }
+}
+impl DoubleEndedIterator for RowIterator<'_> {
+    fn next_back(&mut self) -> Option<Pin> {
+        if self.direction == Direction::RightDown {
+            self.take_back()
+        } else {
+            self.take_front()
+        }
+    }
+}
+/// A contiguous half-open row range within one page.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct Chunk {
+    /// Page node.
+    pub node: NodeId,
+    /// First row included.
+    pub start: u16,
+    /// First row excluded.
+    pub end: u16,
+}
+impl Chunk {
+    /// Row metadata covered by this chunk.
+    pub fn rows(self, list: &PageList) -> Option<&[Row]> {
+        list.node(self.node)?
+            .data
+            .rows
+            .get(usize::from(self.start)..usize::from(self.end))
+    }
+    /// True if all logical rows in the page are covered.
+    pub fn full_page(self, list: &PageList) -> bool {
+        self.start == 0
+            && list
+                .node(self.node)
+                .is_some_and(|n| self.end == n.data.size.rows)
+    }
+    /// True when two chunks overlap in the same page.
+    pub fn overlaps(self, other: Self) -> bool {
+        self.node == other.node && self.start < other.end && other.start < self.end
+    }
+}
+/// A double-ended page iterator yielding maximal contiguous row chunks.
+pub struct PageIterator<'a> {
+    rows: RowIterator<'a>,
+}
+impl PageIterator<'_> {
+    fn front(&mut self) -> Option<Chunk> {
+        let a = self.rows.front?;
+        let b = self.rows.back?;
+        let end = if a.node == b.node {
+            b.y + 1
+        } else {
+            self.rows.list.node(a.node)?.data.size.rows
+        };
+        let c = Chunk {
+            node: a.node,
+            start: a.y,
+            end,
+        };
+        if a.node == b.node {
+            self.rows.front = None;
+            self.rows.back = None;
+        } else {
+            self.rows.front = Some(Pin {
+                node: self.rows.list.node(a.node)?.next?,
+                y: 0,
+                x: 0,
+                garbage: false,
+            });
+        }
+        Some(c)
+    }
+    fn back(&mut self) -> Option<Chunk> {
+        let a = self.rows.front?;
+        let b = self.rows.back?;
+        let start = if a.node == b.node { a.y } else { 0 };
+        let c = Chunk {
+            node: b.node,
+            start,
+            end: b.y + 1,
+        };
+        if a.node == b.node {
+            self.rows.front = None;
+            self.rows.back = None;
+        } else {
+            let node = self.rows.list.node(b.node)?.prev?;
+            self.rows.back = Some(Pin {
+                node,
+                y: self.rows.list.node(node)?.data.size.rows - 1,
+                x: 0,
+                garbage: false,
+            });
+        }
+        Some(c)
+    }
+}
+impl Iterator for PageIterator<'_> {
+    type Item = Chunk;
+    fn next(&mut self) -> Option<Chunk> {
+        if self.rows.direction == Direction::RightDown {
+            self.front()
+        } else {
+            self.back()
+        }
+    }
+}
+impl DoubleEndedIterator for PageIterator<'_> {
+    fn next_back(&mut self) -> Option<Chunk> {
+        if self.rows.direction == Direction::RightDown {
+            self.back()
+        } else {
+            self.front()
+        }
+    }
+}
+impl PageList {
+    fn iter_bounds(&self, start: Point, end: Option<Point>) -> (Option<Pin>, Option<Pin>) {
+        let a = self.pin(start);
+        let b = end.map_or_else(
+            || self.get_bottom_right(start.tag()),
+            |p| {
+                if p.tag() == start.tag() {
+                    self.pin(p)
+                } else {
+                    None
+                }
+            },
+        );
+        if let (Some(a), Some(b)) = (a, b)
+            && (a.eql(b) || a.before(self, b))
+        {
+            return (Some(a), Some(b));
+        }
+        (None, None)
+    }
+    /// Iterate cells in an inclusive tagged range; None means the region's end.
+    pub fn cell_iterator(
+        &self,
+        direction: Direction,
+        start: Point,
+        end: Option<Point>,
+    ) -> CellIterator<'_> {
+        let (front, back) = self.iter_bounds(start, end);
+        CellIterator {
+            list: self,
+            front,
+            back,
+            direction,
+        }
+    }
+    /// Iterate rows in an inclusive tagged range, ignoring endpoint columns.
+    pub fn row_iterator(
+        &self,
+        direction: Direction,
+        start: Point,
+        end: Option<Point>,
+    ) -> RowIterator<'_> {
+        let (front, back) = self.iter_bounds(start, end);
+        RowIterator {
+            list: self,
+            front: front.map(|p| Pin { x: 0, ..p }),
+            back: back.map(|p| Pin { x: 0, ..p }),
+            direction,
+        }
+    }
+    /// Iterate maximal page chunks in an inclusive tagged range.
+    pub fn page_iterator(
+        &self,
+        direction: Direction,
+        start: Point,
+        end: Option<Point>,
+    ) -> PageIterator<'_> {
+        PageIterator {
+            rows: self.row_iterator(direction, start, end),
+        }
+    }
+    /// Iterate prompt starts, coalescing continuation rows in either direction.
+    pub fn prompt_iterator(
+        &self,
+        direction: Direction,
+        start: Point,
+        end: Option<Point>,
+    ) -> PromptIterator<'_> {
+        let (front, back) = self.iter_bounds(start, end);
+        PromptIterator {
+            list: self,
+            current: if direction == Direction::RightDown {
+                front
+            } else {
+                back
+            },
+            limit: if direction == Direction::RightDown {
+                back
+            } else {
+                front
+            },
+            direction,
+        }
+    }
+    /// Locate prompt, input, or output bounds within the prompt starting at `at`.
+    pub fn highlight_semantic_content(
+        &self,
+        at: Pin,
+        content: SemanticContent,
+    ) -> Option<(Pin, Pin)> {
+        let rowstart = Pin { x: 0, ..at };
+        let start_pt = self.point_from_pin(Tag::Screen, rowstart)?;
+        let mut prompts = self.prompt_iterator(Direction::RightDown, start_pt, None);
+        prompts.next()?;
+        let end = prompts
+            .next()
+            .and_then(|p| p.up(self, 1))
+            .map(|p| Pin {
+                x: self.cols - 1,
+                ..p
+            })
+            .or_else(|| self.get_bottom_right(Tag::Screen))?;
+        let mut it = CellIterator {
+            list: self,
+            front: Some(at),
+            back: Some(end),
+            direction: Direction::RightDown,
+        };
+        match content {
+            SemanticContent::Prompt => {
+                let mut last = at;
+                for p in it {
+                    if p.row_and_cell(self)?.1.semantic_content() == SemanticContent::Output {
+                        break;
+                    }
+                    last = p;
+                }
+                Some((rowstart, last))
+            }
+            SemanticContent::Input => {
+                let first = loop {
+                    let p = it.next()?;
+                    match p.row_and_cell(self)?.1.semantic_content() {
+                        SemanticContent::Prompt => {}
+                        SemanticContent::Output => return None,
+                        SemanticContent::Input => break p,
+                    }
+                };
+                let mut last = first;
+                for p in it {
+                    match p.row_and_cell(self)?.1.semantic_content() {
+                        SemanticContent::Prompt => {}
+                        SemanticContent::Output => break,
+                        SemanticContent::Input => last = p,
+                    }
+                }
+                Some((first, last))
+            }
+            SemanticContent::Output => {
+                let first = loop {
+                    let p = it.next()?;
+                    let c = p.row_and_cell(self)?.1;
+                    if c.semantic_content() == SemanticContent::Output && c.has_text() {
+                        break p;
+                    }
+                };
+                let mut last = first;
+                for p in it {
+                    let c = p.row_and_cell(self)?.1;
+                    if c.semantic_content() != SemanticContent::Output {
+                        break;
+                    }
+                    if c.has_text() {
+                        last = p;
+                    }
+                }
+                Some((first, last))
+            }
+        }
+    }
+}
+/// Iterator over primary prompts and orphaned prompt continuations.
+pub struct PromptIterator<'a> {
+    list: &'a PageList,
+    current: Option<Pin>,
+    limit: Option<Pin>,
+    direction: Direction,
+}
+impl Iterator for PromptIterator<'_> {
+    type Item = Pin;
+    fn next(&mut self) -> Option<Pin> {
+        let mut current = self.current?;
+        loop {
+            let at_limit = self
+                .limit
+                .is_some_and(|p| p.node == current.node && p.y == current.y);
+            let kind = current.row_and_cell(self.list)?.0.semantic_prompt();
+            if kind != SemanticPrompt::None {
+                let result = Pin { x: 0, ..current };
+                if at_limit {
+                    self.current = None;
+                    return Some(result);
+                }
+                if self.direction == Direction::RightDown {
+                    let mut next = current.down(self.list, 1);
+                    while let Some(p) = next {
+                        if p.row_and_cell(self.list)?.0.semantic_prompt()
+                            != SemanticPrompt::PromptContinuation
+                        {
+                            self.current = Some(p);
+                            return Some(result);
+                        }
+                        if self.limit.is_some_and(|l| l.node == p.node && l.y == p.y) {
+                            break;
+                        }
+                        next = p.down(self.list, 1);
+                    }
+                    self.current = None;
+                    return Some(result);
+                }
+                if kind == SemanticPrompt::Prompt {
+                    self.current = current.up(self.list, 1);
+                    return Some(result);
+                }
+                let mut end = current;
+                while let Some(prior) = end.up(self.list, 1) {
+                    if self
+                        .limit
+                        .is_some_and(|p| p.node == prior.node && p.y == prior.y)
+                    {
+                        break;
+                    }
+                    match prior.row_and_cell(self.list)?.0.semantic_prompt() {
+                        SemanticPrompt::None => {
+                            self.current = Some(prior);
+                            return Some(Pin { x: 0, ..end });
+                        }
+                        SemanticPrompt::Prompt => {
+                            self.current = prior.up(self.list, 1);
+                            return Some(Pin { x: 0, ..prior });
+                        }
+                        SemanticPrompt::PromptContinuation => end = prior,
+                    }
+                }
+                self.current = None;
+                return Some(result);
+            }
+            if at_limit {
+                self.current = None;
+                return None;
+            }
+            let next = if self.direction == Direction::RightDown {
+                current.down(self.list, 1)
+            } else {
+                current.up(self.list, 1)
+            };
+            let Some(next) = next else {
+                self.current = None;
+                return None;
+            };
+            current = next;
+        }
+    }
+}
+
+#[derive(Clone)]
+struct SavedRow {
+    row: Row,
+    cells: Vec<OwnedCell>,
+}
+impl PageList {
+    fn snapshot(&self) -> Vec<SavedRow> {
+        self.row_iterator(
+            Direction::RightDown,
+            Point::Screen(Coordinate::default()),
+            None,
+        )
+        .filter_map(|p| {
+            let page = &self.node(p.node)?.data;
+            let mut row = *page.get_row(usize::from(p.y))?;
+            row.set_dirty(row.dirty() || page.dirty);
+            let cells = (row.cells()..row.cells() + usize::from(page.size.cols))
+                .map(|i| page.export_cell(i))
+                .collect();
+            Some(SavedRow { row, cells })
+        })
+        .collect()
+    }
+    fn build_pages(cols: u16, rows: &[SavedRow], mark_dirty: bool) -> Result<Vec<Page>, Error> {
+        let mut pages = Vec::new();
+        let mut offset = 0;
+        while offset < rows.len() {
+            let mut cap = initial_capacity(cols);
+            let count = usize::from(cap.rows).min(rows.len() - offset);
+            // Count required values before allocating, so cloning is monotonic.
+            let mut styles = std::collections::HashSet::new();
+            let mut links = std::collections::HashSet::new();
+            let mut gb = 0usize;
+            let mut sb = 0usize;
+            let mut hc = 0usize;
+            for r in &rows[offset..offset + count] {
+                for c in &r.cells {
+                    if let Some(s) = c.style {
+                        styles.insert(s);
+                    }
+                    if let Some(g) = &c.grapheme {
+                        gb += (g.len() * 4).next_multiple_of(16);
+                    }
+                    if let Some(h) = &c.hyperlink {
+                        hc += 1;
+                        if links.insert(h.clone()) {
+                            sb += h.string_bytes();
+                        }
+                    }
+                }
+            }
+            let sc = crate::style::Set::capacity_for_count(styles.len());
+            let lc = crate::hyperlink::Set::capacity_for_count(links.len()).max(hc.div_ceil(16));
+            cap.styles = cap
+                .styles
+                .max(u16::try_from(sc).map_err(|_| Error::OutOfSpace)?);
+            cap.hyperlink_bytes = cap
+                .hyperlink_bytes
+                .max(u16::try_from(lc * 48).map_err(|_| Error::OutOfSpace)?);
+            cap.grapheme_bytes = cap
+                .grapheme_bytes
+                .max(u32::try_from(gb).map_err(|_| Error::OutOfSpace)?);
+            cap.string_bytes = cap
+                .string_bytes
+                .max(u32::try_from(sb).map_err(|_| Error::OutOfSpace)?);
+            let mut page = Page::init(cap)?;
+            page.size.rows = count as u16;
+            for (y, row) in rows[offset..offset + count].iter().enumerate() {
+                for (x, c) in row.cells.iter().take(usize::from(cols)).enumerate() {
+                    page.import_cell(x, y, c)?;
+                }
+                let start = page.rows[y].cells();
+                page.rows[y] = row.row;
+                page.rows[y].set_cells(start);
+                page.rows[y].set_dirty(mark_dirty || row.row.dirty());
+                page.update_row_grapheme_flag(y);
+                page.update_row_styled_flag(y);
+                page.update_row_hyperlink_flag(y);
+                page.rows[y].set_kitty_virtual_placeholder(
+                    row.cells.iter().any(|c| c.cell.codepoint() == 0x10eeee),
+                );
+            }
+            pages.push(page);
+            offset += count;
+        }
+        Ok(pages)
+    }
+    fn install_pages(
+        &mut self,
+        pages: Vec<Page>,
+        cols: u16,
+        coords: &[(TrackedPin, usize, u16, bool)],
+    ) -> Result<(), Error> {
+        let old: Vec<_> = self
+            .page_iterator(
+                Direction::RightDown,
+                Point::Screen(Coordinate::default()),
+                None,
+            )
+            .map(|c| c.node)
+            .collect();
+        let mut added = Vec::new();
+        for page in pages {
+            let id = match self.create_node(page.capacity) {
+                Ok(id) => id,
+                Err(e) => {
+                    for id in added {
+                        if let Some(n) = self.detach(id) {
+                            self.recycle(n);
+                        }
+                    }
+                    return Err(e);
+                }
+            };
+            self.node_mut(id).ok_or(Error::InvalidId)?.data = page;
+            self.insert_after(self.last, id);
+            added.push(id);
+        }
+        for id in old {
+            if let Some(n) = self.detach(id) {
+                self.recycle(n);
+            }
+        }
+        self.cols = cols;
+        self.total_rows = self
+            .nodes
+            .iter()
+            .flatten()
+            .map(|n| usize::from(n.data.size.rows))
+            .sum();
+        for &(h, y, x, garbage) in coords {
+            if let Some(mut p) =
+                self.pin_at(y.min(self.total_rows.saturating_sub(1)), x.min(cols - 1))
+            {
+                p.garbage = garbage;
+                self.pins[h.index].pin = Some(p);
+            }
+        }
+        self.fixup_viewport();
+        Ok(())
+    }
+    fn trim_blank_rows(&mut self, limit: usize) -> Result<(), Error> {
+        for _ in 0..limit {
+            if self.total_rows <= 1 {
+                break;
+            }
+            let last = self
+                .pin_at(self.total_rows - 1, 0)
+                .ok_or(Error::InvalidCoordinate)?;
+            let page = &self.node(last.node).ok_or(Error::InvalidId)?.data;
+            if page
+                .get_cells(usize::from(last.y))
+                .is_some_and(|c| c.iter().any(|c| !c.is_empty()))
+                || self
+                    .tracked_pins()
+                    .any(|(_, p)| p.node == last.node && p.y == last.y)
+            {
+                break;
+            }
+            self.erase_range(self.total_rows - 1, self.total_rows)?;
+        }
+        Ok(())
+    }
+    /// Resize the active area and optionally reflow wrapped logical lines.
+    pub fn resize(&mut self, opts: Resize) -> Result<(), Error> {
+        let cols = opts.cols.unwrap_or(self.cols);
+        let rows = opts.rows.unwrap_or(self.rows);
+        if cols == 0 || rows == 0 {
+            return Err(Error::InvalidDimensions);
+        }
+        let cursor = opts.cursor.and_then(|c| {
+            self.pin(Point::Active(Coordinate {
+                x: c.x,
+                y: u32::from(c.y),
+            }))
+        });
+        let cursor_handle = cursor.map(|p| self.track_pin(p)).transpose()?;
+        let result = self.resize_inner(opts, cols, rows, cursor_handle);
+        if let Some(h) = cursor_handle {
+            self.untrack_pin(h);
+        }
+        result
+    }
+    fn resize_inner(
+        &mut self,
+        opts: Resize,
+        cols: u16,
+        rows: u16,
+        cursor_handle: Option<TrackedPin>,
+    ) -> Result<(), Error> {
+        let old_rows = self.rows;
+        self.min_max_size = min_max_size(cols, rows);
+        if cols != self.cols {
+            if !opts.reflow && cols < self.cols {
+                for n in self.nodes.iter_mut().flatten() {
+                    let p = &mut n.data;
+                    for y in 0..usize::from(p.size.rows) {
+                        p.clear_cells(y, usize::from(cols), usize::from(p.size.cols), false)?;
+                    }
+                    p.size.cols = cols;
+                }
+                self.cols = cols;
+                for slot in &mut self.pins {
+                    if let Some(p) = &mut slot.pin {
+                        p.x = p.x.min(cols - 1);
+                    }
+                }
+            } else {
+                let old = self.snapshot();
+                let tracked: Vec<_> = self
+                    .tracked_pins()
+                    .filter_map(|(h, p)| self.screen_row(p).map(|y| (h, y, p.x, p.garbage)))
+                    .collect();
+                let mut remapped = tracked.clone();
+                let mut output = Vec::<SavedRow>::new();
+                if opts.reflow {
+                    let mut current = SavedRow {
+                        row: Row::default(),
+                        cells: Vec::new(),
+                    };
+                    for (y, row) in old.iter().enumerate() {
+                        if current.cells.is_empty() {
+                            current.row = row.row;
+                            current.row.set_wrap(false);
+                            current
+                                .row
+                                .set_wrap_continuation(y > 0 && old[y - 1].row.wrap());
+                        }
+                        let mut len = if row.row.wrap() {
+                            row.cells.len()
+                        } else {
+                            row.cells
+                                .iter()
+                                .rposition(|c| !c.cell.is_empty())
+                                .map_or(0, |x| x + 1)
+                        };
+                        if let Some(h) = cursor_handle
+                            && let Some((_, _, x, _)) =
+                                tracked.iter().find(|(th, ty, _, _)| *th == h && *ty == y)
+                        {
+                            len = len.max(usize::from(*x) + 1);
+                        }
+                        let mut x = 0;
+                        while x < len {
+                            let c = &row.cells[x];
+                            if c.cell.wide() == Wide::SpacerHead {
+                                x += 1;
+                                continue;
+                            }
+                            let wide = c.cell.wide() == Wide::Wide;
+                            let width = if wide && cols > 1 { 2 } else { 1 };
+                            if current.cells.len() + width > usize::from(cols) {
+                                if wide && current.cells.len() < usize::from(cols) {
+                                    let mut spacer = Cell::default();
+                                    spacer.set_wide(Wide::SpacerHead);
+                                    current.cells.push(OwnedCell {
+                                        cell: spacer,
+                                        style: None,
+                                        grapheme: None,
+                                        hyperlink: None,
+                                    });
+                                }
+                                current.row.set_wrap(true);
+                                output.push(current);
+                                let mut meta = row.row;
+                                meta.set_wrap(false);
+                                meta.set_wrap_continuation(true);
+                                current = SavedRow {
+                                    row: meta,
+                                    cells: Vec::new(),
+                                };
+                            }
+                            let newx = current.cells.len() as u16;
+                            let newy = output.len();
+                            for (index, (_, ty, tx, _)) in tracked.iter().enumerate() {
+                                if *ty == y && usize::from(*tx) >= x && usize::from(*tx) < x + width
+                                {
+                                    remapped[index].1 = newy;
+                                    remapped[index].2 = newx + (*tx - x as u16);
+                                }
+                            }
+                            let mut value = c.clone();
+                            if wide && cols == 1 {
+                                value.cell = Cell::default();
+                                value.style = None;
+                                value.grapheme = None;
+                                value.hyperlink = None;
+                            }
+                            current.cells.push(value);
+                            if wide && cols > 1 {
+                                let tail = row
+                                    .cells
+                                    .get(x + 1)
+                                    .filter(|v| v.cell.wide() == Wide::SpacerTail)
+                                    .cloned()
+                                    .unwrap_or_else(|| {
+                                        let mut cell = Cell::default();
+                                        cell.set_wide(Wide::SpacerTail);
+                                        OwnedCell {
+                                            cell,
+                                            style: None,
+                                            grapheme: None,
+                                            hyperlink: None,
+                                        }
+                                    });
+                                current.cells.push(tail);
+                            }
+                            x += if wide { 2 } else { 1 };
+                        }
+                        for (index, (_, ty, tx, _)) in tracked.iter().enumerate() {
+                            if *ty == y && usize::from(*tx) >= len {
+                                remapped[index].1 = output.len();
+                                remapped[index].2 = (current.cells.len() + usize::from(*tx) - len)
+                                    .min(usize::from(cols - 1))
+                                    as u16;
+                            }
+                        }
+                        if !row.row.wrap() {
+                            current.row.set_wrap(false);
+                            output.push(current);
+                            current = SavedRow {
+                                row: Row::default(),
+                                cells: Vec::new(),
+                            };
+                        }
+                    }
+                    if !current.cells.is_empty() {
+                        output.push(current);
+                    }
+                } else {
+                    for row in &old {
+                        let mut r = row.clone();
+                        r.cells.truncate(usize::from(cols));
+                        for c in &mut r.cells {
+                            if c.cell.wide() == Wide::SpacerHead {
+                                c.cell.set_wide(Wide::Narrow);
+                                c.cell.set_codepoint(0);
+                                c.grapheme = None;
+                            }
+                        }
+                        output.push(r);
+                    }
+                }
+                if opts.reflow {
+                    let mut minimum = usize::from(rows);
+                    for (h, y, _, _) in &remapped {
+                        minimum = minimum.max(y + 1);
+                        if Some(*h) == cursor_handle {
+                            minimum = minimum.max(
+                                y + 1
+                                    + opts.cursor.map_or(0, |c| {
+                                        usize::from(old_rows.saturating_sub(c.y + 1))
+                                    }),
+                            );
+                        }
+                    }
+                    while output.len() > minimum
+                        && output.last().is_some_and(|r| {
+                            r.row.semantic_prompt() == SemanticPrompt::None
+                                && r.cells.iter().all(|c| c.cell.is_empty())
+                        })
+                    {
+                        output.pop();
+                    }
+                }
+                while output.len() < usize::from(rows) {
+                    output.push(SavedRow {
+                        row: Row::default(),
+                        cells: Vec::new(),
+                    });
+                }
+                let pages = Self::build_pages(cols, &output, true)?;
+                self.install_pages(pages, cols, &remapped)?;
+            }
+        }
+        if rows < old_rows {
+            self.trim_blank_rows(usize::from(old_rows - rows))?;
+        }
+        self.rows = rows;
+        if rows > old_rows && opts.cursor.is_some_and(|c| c.y < old_rows - 1) {
+            for _ in 0..rows - old_rows {
+                self.grow()?;
+            }
+        }
+        while self.total_rows < usize::from(rows) {
+            self.grow()?;
+        }
+        self.fixup_viewport();
+        Ok(())
+    }
+    /// Clone an inclusive cell range into an independent list and remap tracked pins.
+    pub fn clone_range(
+        &self,
+        start: Point,
+        end: Option<Point>,
+    ) -> Result<(Self, HashMap<TrackedPin, TrackedPin>), Error> {
+        let (a, b) = self.iter_bounds(start, end);
+        let a = Pin {
+            x: 0,
+            ..a.ok_or(Error::InvalidCoordinate)?
+        };
+        let b = Pin {
+            x: self.cols - 1,
+            ..b.ok_or(Error::InvalidCoordinate)?
+        };
+        let ay = self.screen_row(a).ok_or(Error::InvalidCoordinate)?;
+        let by = self.screen_row(b).ok_or(Error::InvalidCoordinate)?;
+        let mut saved = self.snapshot()[ay..=by].to_vec();
+        let blank = || OwnedCell {
+            cell: Cell::default(),
+            style: None,
+            grapheme: None,
+            hyperlink: None,
+        };
+        for c in &mut saved[0].cells[..usize::from(a.x)] {
+            *c = blank();
+        }
+        if let Some(last) = saved.last_mut() {
+            for c in &mut last.cells[usize::from(b.x) + 1..] {
+                *c = blank();
+            }
+        }
+        while saved.len() < usize::from(self.rows) {
+            saved.push(SavedRow {
+                row: Row::default(),
+                cells: Vec::new(),
+            });
+        }
+        let mut result = Self::init(self.cols, self.rows, Some(self.explicit_max_size))?;
+        let pages = Self::build_pages(self.cols, &saved, false)?;
+        let vh = result.viewport_pin.ok_or(Error::InvalidId)?;
+        result.install_pages(pages, self.cols, &[(vh, 0, 0, false)])?;
+        let mut remap = HashMap::new();
+        for (h, p) in self.tracked_pins() {
+            if Some(h) == self.viewport_pin {
+                continue;
+            }
+            if p.is_between(self, a, b) {
+                let y = self.screen_row(p).ok_or(Error::InvalidCoordinate)?;
+                let mut q = result.pin_at(y - ay, p.x).ok_or(Error::InvalidCoordinate)?;
+                q.garbage = p.garbage;
+                remap.insert(h, result.track_pin(q)?);
+            }
+        }
+        Ok((result, remap))
+    }
+    /// Fallibly clone the whole screen with independently owned tracked handles.
+    pub fn try_clone(&self) -> Result<Self, Error> {
+        let (mut result, remap) = self.clone_range(Point::Screen(Coordinate::default()), None)?;
+        for handle in remap.into_values() {
+            result.untrack_pin(handle);
+        }
+        Ok(result)
+    }
+    /// Debug-friendly UTF-8 rows, omitting wide spacers and rendering blanks as spaces.
+    pub fn diagram(&self) -> String {
+        let mut s = String::new();
+        for p in self.row_iterator(
+            Direction::RightDown,
+            Point::Screen(Coordinate::default()),
+            None,
+        ) {
+            if let Some(n) = self.node(p.node)
+                && let Some(cells) = n.data.get_cells(usize::from(p.y))
+            {
+                for c in cells {
+                    if matches!(c.wide(), Wide::SpacerHead | Wide::SpacerTail) {
+                        continue;
+                    }
+                    s.push(
+                        char::from_u32(c.codepoint())
+                            .filter(|c| *c != '\0')
+                            .unwrap_or(' '),
+                    );
+                }
+                s.push('\n');
+            }
+        }
+        s
+    }
+}
+#[cfg(any(debug_assertions, test))]
+impl PageList {
+    /// Verify list links, byte/row accounting, every page, and all tracked pins.
+    pub fn verify_integrity(&self) -> Result<(), String> {
+        if self.pause_checks > 0 {
+            return Ok(());
+        }
+        let mut prev = None;
+        let mut id = self.first;
+        let mut rows = 0;
+        let mut bytes = 0;
+        let mut count = 0;
+        while let Some(i) = id {
+            let n = self.node(i).ok_or("stale node")?;
+            if n.prev != prev {
+                return Err("broken previous link".into());
+            }
+            n.data
+                .verify_integrity()
+                .map_err(|e| format!("page: {e:?}"))?;
+            rows += usize::from(n.data.size.rows);
+            bytes += allocated_size(n.data.capacity);
+            count += 1;
+            if count > self.nodes.len() {
+                return Err("cycle".into());
+            }
+            prev = id;
+            id = n.next;
+        }
+        if prev != self.last
+            || rows != self.total_rows
+            || bytes != self.page_size
+            || count != self.total_pages()
+        {
+            return Err("list accounting mismatch".into());
+        }
+        if rows < usize::from(self.rows) {
+            return Err("active rows missing".into());
+        }
+        for (_, p) in self.tracked_pins() {
+            if !self.pin_is_valid(p) {
+                return Err("invalid tracked pin".into());
+            }
+        }
+        Ok(())
+    }
+    /// Assert all list invariants in debug/test builds.
+    pub fn assert_integrity(&self) {
+        assert_eq!(self.verify_integrity(), Ok(()));
+    }
+}
+
+fn double16(v: u16) -> Result<u16, Error> {
+    if v == u16::MAX {
+        return Err(Error::OutOfSpace);
+    }
+    Ok(v.saturating_mul(2).max(1))
+}
+
+fn double32(v: u32) -> Result<u32, Error> {
+    if v == u32::MAX {
+        return Err(Error::OutOfSpace);
+    }
+    Ok(v.saturating_mul(2).max(1))
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    fn screen(x: u16, y: u32) -> Point {
+        Point::Screen(Coordinate { x, y })
+    }
+    fn active(x: u16, y: u32) -> Point {
+        Point::Active(Coordinate { x, y })
+    }
+    fn grow(s: &mut PageList, n: usize) {
+        for _ in 0..n {
+            s.grow().unwrap();
+        }
+    }
+    fn fill(s: &mut PageList) {
+        for y in 0..s.total_rows {
+            for x in 0..s.cols {
+                *s.get_cell_mut(screen(x, y as u32)).unwrap() = Cell::init(u32::from(b'A'));
+            }
+        }
+    }
+    fn write_rows(s: &mut PageList) {
+        for y in 0..s.total_rows {
+            *s.get_cell_mut(screen(0, y as u32)).unwrap() = Cell::init(y as u32);
+        }
+    }
+    fn wraps(s: &mut PageList) {
+        for y in 0..s.total_rows {
+            let p = s.pin(screen(0, y as u32)).unwrap();
+            let r = s
+                .node_mut(p.node)
+                .unwrap()
+                .data
+                .get_row_mut(usize::from(p.y))
+                .unwrap();
+            r.set_wrap(y % 2 == 0);
+            r.set_wrap_continuation(y % 2 != 0);
+        }
+    }
+    fn finish(s: &PageList) {
+        s.assert_integrity();
+    }
+    fn first_cap(s: &PageList) -> usize {
+        usize::from(s.node(s.first.unwrap()).unwrap().data.capacity.rows)
+    }
+    fn fill_pages(s: &mut PageList, n: usize) {
+        let target = first_cap(s) * n;
+        grow(s, target - s.total_rows);
+    }
+    #[test]
+    fn page_list() {
+        let s = PageList::init(80, 24, None).unwrap();
+        assert_eq!(s.viewport, Viewport::Active);
+        assert_eq!(s.total_rows, 24);
+        assert_eq!(s.get_top_left(Tag::Active).unwrap().node, s.first.unwrap());
+        assert_eq!(
+            s.scrollbar(),
+            Scrollbar {
+                total: 24,
+                offset: 0,
+                len: 24
+            }
+        );
+        assert_eq!(
+            s.tracked_pin(s.viewport_pin.unwrap()).unwrap().node,
+            s.first.unwrap()
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_init_rows_across_two_pages() {
+        let mut cols = 50;
+        while initial_capacity(cols).rows >= 100 {
+            cols += 50;
+        }
+        let s = PageList::init(cols, 100, None).unwrap();
+        assert_eq!(s.total_pages(), 2);
+        assert_eq!(s.total_rows, 100);
+        assert_eq!(
+            s.scrollbar(),
+            Scrollbar {
+                total: 100,
+                offset: 0,
+                len: 100
+            }
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_init_more_than_max_cols() {
+        let cols = page::STD_CAPACITY.max_cols().unwrap() + 1;
+        let s = PageList::init(cols, 24, None).unwrap();
+        assert_eq!(s.cols, cols);
+        assert_eq!(s.total_rows, 24);
+        assert!(s.page_size > std_size());
+        finish(&s);
+    }
+    #[test]
+    fn page_list_point_from_pin_active_no_history() {
+        let s = PageList::init(80, 24, None).unwrap();
+        for (x, y) in [(0, 0), (4, 2)] {
+            let p = s.pin(screen(x, y)).unwrap();
+            assert_eq!(s.point_from_pin(Tag::Active, p), Some(active(x, y)));
+        }
+    }
+    #[test]
+    fn page_list_point_from_pin_active_with_history() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 30);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.pin(screen(2, 30)).unwrap()),
+            Some(active(2, 0))
+        );
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.pin(screen(2, 21)).unwrap()),
+            None
+        );
+    }
+    #[test]
+    fn page_list_point_from_pin_active_from_prior_page() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let cap = first_cap(&s);
+        grow(&mut s, cap * 5);
+        let p = Pin {
+            node: s.last.unwrap(),
+            x: 2,
+            y: 0,
+            garbage: false,
+        };
+        assert_eq!(s.point_from_pin(Tag::Active, p), Some(active(2, 0)));
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.get_top_left(Tag::Screen).unwrap()),
+            None
+        );
+    }
+    #[test]
+    fn page_list_point_from_pin_traverse_pages() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let cap = first_cap(&s);
+        grow(&mut s, cap * 2);
+        let p = Pin {
+            node: s.node(s.last.unwrap()).unwrap().prev.unwrap(),
+            y: 5,
+            x: 2,
+            garbage: false,
+        };
+        assert_eq!(
+            s.point_from_pin(Tag::Screen, p),
+            Some(screen(2, (cap * (s.total_pages() - 2) + 5) as u32))
+        );
+        assert!(
+            s.point_from_pin(Tag::Active, s.get_top_left(Tag::Screen).unwrap())
+                .is_none()
+        );
+    }
+    #[test]
+    fn page_list_active_after_grow() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        assert_eq!(
+            s.point_from_pin(Tag::Screen, s.get_top_left(Tag::Active).unwrap()),
+            Some(screen(0, 10))
+        );
+        assert_eq!(s.get_bottom_right(Tag::Active).unwrap().y, 33);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scrollbar_with_max_size_0_after_grow() {
+        let mut s = PageList::init(80, 24, Some(0)).unwrap();
+        grow(&mut s, 10);
+        assert_eq!(
+            s.scrollbar(),
+            Scrollbar {
+                total: 24,
+                offset: 0,
+                len: 24
+            }
+        );
+    }
+    #[test]
+    fn page_list_scroll_with_max_size_0_no_history() {
+        let mut s = PageList::init(80, 24, Some(0)).unwrap();
+        grow(&mut s, 10);
+        let before = s.get_top_left(Tag::Viewport);
+        s.scroll(Scroll::DeltaRow(-5));
+        assert_eq!(s.viewport, Viewport::Active);
+        s.scroll(Scroll::Top);
+        assert_eq!(s.get_top_left(Tag::Viewport), before);
+    }
+    #[test]
+    fn page_list_scroll_top() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        assert_eq!(s.viewport_row_offset(), 10);
+        s.scroll(Scroll::Top);
+        assert_eq!(s.viewport_row_offset(), 0);
+        grow(&mut s, 10);
+        assert_eq!(
+            s.scrollbar(),
+            Scrollbar {
+                total: 44,
+                offset: 0,
+                len: 24
+            }
+        );
+        s.scroll(Scroll::Active);
+        assert_eq!(s.viewport_row_offset(), 20);
+    }
+    #[test]
+    fn page_list_scroll_delta_row_back() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        s.scroll(Scroll::DeltaRow(-5));
+        assert_eq!(s.viewport_row_offset(), 5);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_delta_row_back_overflow() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        s.scroll(Scroll::DeltaRow(-100));
+        assert_eq!(s.viewport_row_offset(), 0);
+        assert_eq!(s.viewport, Viewport::Top);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_delta_row_forward() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        s.scroll(Scroll::Top);
+        s.scroll(Scroll::DeltaRow(5));
+        assert_eq!(s.viewport_row_offset(), 5);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_delta_row_forward_into_active() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        s.scroll(Scroll::Top);
+        s.scroll(Scroll::DeltaRow(100));
+        assert_eq!(s.viewport_row_offset(), 10);
+        assert_eq!(s.viewport, Viewport::Active);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_pin() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        s.scroll(Scroll::Pin(s.pin(screen(5, 3)).unwrap()));
+        assert_eq!(s.viewport_row_offset(), 3);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_pin_in_active() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        s.scroll(Scroll::Pin(s.pin(active(5, 3)).unwrap()));
+        assert_eq!(s.viewport_row_offset(), 10);
+        assert_eq!(s.viewport, Viewport::Active);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_pin_at_top() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 10);
+        s.scroll(Scroll::Pin(s.pin(screen(0, 0)).unwrap()));
+        assert_eq!(s.viewport_row_offset(), 0);
+        assert_eq!(s.viewport, Viewport::Top);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_0() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 30);
+        s.scroll(Scroll::Row(0));
+        assert_eq!(s.viewport_row_offset(), 0);
+        assert_eq!(s.viewport, Viewport::Top);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_in_scrollback() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 30);
+        s.scroll(Scroll::Row(10));
+        assert_eq!(s.viewport_row_offset(), 10);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_in_middle() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 50);
+        s.scroll(Scroll::Row(25));
+        assert_eq!(s.viewport_row_offset(), 25);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_at_active_boundary() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 30);
+        s.scroll(Scroll::Row(30));
+        assert_eq!(s.viewport_row_offset(), 30);
+        assert_eq!(s.viewport, Viewport::Active);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_beyond_active() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 30);
+        s.scroll(Scroll::Row(999));
+        assert_eq!(s.viewport_row_offset(), 30);
+        assert_eq!(s.viewport, Viewport::Active);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_without_scrollback() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        s.scroll(Scroll::Row(10));
+        assert_eq!(s.viewport_row_offset(), 0);
+        assert_eq!(s.viewport, Viewport::Active);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_then_delta() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 30);
+        s.scroll(Scroll::Row(10));
+        s.scroll(Scroll::DeltaRow(5));
+        assert_eq!(s.viewport_row_offset(), 15);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_with_cache_fast_path_down() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 60);
+        s.scroll(Scroll::Row(10));
+        assert_eq!(s.scrollbar().offset, 10);
+        s.scroll(Scroll::Row(20));
+        assert_eq!(s.viewport_row_offset(), 20);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_to_row_with_cache_fast_path_up() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 60);
+        s.scroll(Scroll::Row(20));
+        assert_eq!(s.scrollbar().offset, 20);
+        s.scroll(Scroll::Row(10));
+        assert_eq!(s.viewport_row_offset(), 10);
+        assert_eq!(s.viewport, Viewport::Pin);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_grow_fit_in_capacity() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        assert!(first_cap(&s) > 24);
+        assert_eq!(s.grow().unwrap(), None);
+        assert_eq!(
+            s.point_from_pin(Tag::Screen, s.get_top_left(Tag::Active).unwrap()),
+            Some(screen(0, 1))
+        );
+    }
+    #[test]
+    fn page_list_grow_allocate() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let old = s.last.unwrap();
+        let cap = first_cap(&s);
+        grow(&mut s, cap - 24);
+        let new = s.grow().unwrap().unwrap();
+        assert_eq!(s.last, Some(new));
+        assert_eq!(s.node(old).unwrap().next, Some(new));
+        assert_eq!(s.pin(active(0, 23)).unwrap().node, new);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_grow_prune_scrollback() {
+        let mut s = PageList::init(80, 24, Some(std_size())).unwrap();
+        let cap = first_cap(&s);
+        fill_pages(&mut s, 2);
+        let old = s.first.unwrap();
+        let second = s.node(old).unwrap().next.unwrap();
+        let bytes = s.page_size;
+        let h = s.track_pin(s.pin(screen(0, 0)).unwrap()).unwrap();
+        let y = cap / 2;
+        s.scroll(Scroll::Row(y));
+        assert_eq!(s.scrollbar().offset, y);
+        let new = s.grow().unwrap().unwrap();
+        assert_eq!(new.index(), old.index());
+        assert_ne!(new.generation(), old.generation());
+        assert_eq!(s.page_size, bytes);
+        assert_eq!(s.first, Some(second));
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!(p.node, second);
+        assert!(p.garbage);
+        assert_eq!(p.x, 0);
+        assert_eq!(p.y, 0);
+        assert_eq!(s.scrollbar().offset, y.saturating_sub(cap));
+        assert!(s.node(old).is_none());
+        finish(&s);
+    }
+    #[test]
+    fn page_list_grow_prune_scrollback_with_viewport_pin_not_in_pruned_page() {
+        let mut s = PageList::init(80, 24, Some(std_size())).unwrap();
+        let cap = first_cap(&s);
+        fill_pages(&mut s, 2);
+        let old = s.first.unwrap();
+        let second = s.node(old).unwrap().next.unwrap();
+        let bytes = s.page_size;
+        let h = s.track_pin(s.pin(screen(0, 0)).unwrap()).unwrap();
+        let y = cap + 5;
+        s.scroll(Scroll::Row(y));
+        assert_eq!(s.scrollbar().offset, y);
+        let new = s.grow().unwrap().unwrap();
+        assert_eq!(new.index(), old.index());
+        assert_ne!(new.generation(), old.generation());
+        assert_eq!(s.page_size, bytes);
+        assert_eq!(s.first, Some(second));
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!(p.node, second);
+        assert!(p.garbage);
+        assert_eq!(p.x, 0);
+        assert_eq!(p.y, 0);
+        assert_eq!(s.scrollbar().offset, y.saturating_sub(cap));
+        assert!(s.node(old).is_none());
+        finish(&s);
+    }
+    #[test]
+    fn page_list_increase_capacity_to_increase_styles() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let old = s.first.unwrap();
+        let before = s.node(old).unwrap().data.capacity.styles;
+        let id = s
+            .increase_capacity(old, Some(IncreaseCapacity::Styles))
+            .unwrap();
+        assert_eq!(s.first, Some(id));
+        assert_eq!(s.node(id).unwrap().data.capacity.styles, before * 2);
+        assert_eq!(s.total_rows, 24);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_increase_capacity_to_increase_graphemes() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let old = s.first.unwrap();
+        let before = s.node(old).unwrap().data.capacity.grapheme_bytes;
+        let id = s
+            .increase_capacity(old, Some(IncreaseCapacity::GraphemeBytes))
+            .unwrap();
+        assert_eq!(s.first, Some(id));
+        assert_eq!(s.node(id).unwrap().data.capacity.grapheme_bytes, before * 2);
+        assert_eq!(s.total_rows, 24);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_increase_capacity_to_increase_hyperlinks() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let old = s.first.unwrap();
+        let before = s.node(old).unwrap().data.capacity.hyperlink_bytes;
+        let id = s
+            .increase_capacity(old, Some(IncreaseCapacity::HyperlinkBytes))
+            .unwrap();
+        assert_eq!(s.first, Some(id));
+        assert_eq!(
+            s.node(id).unwrap().data.capacity.hyperlink_bytes,
+            before * 2
+        );
+        assert_eq!(s.total_rows, 24);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_increase_capacity_to_increase_string_bytes() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let old = s.first.unwrap();
+        let before = s.node(old).unwrap().data.capacity.string_bytes;
+        let id = s
+            .increase_capacity(old, Some(IncreaseCapacity::StringBytes))
+            .unwrap();
+        assert_eq!(s.first, Some(id));
+        assert_eq!(s.node(id).unwrap().data.capacity.string_bytes, before * 2);
+        assert_eq!(s.total_rows, 24);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_increase_capacity_tracked_pins() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let h = s.track_pin(s.pin(active(3, 12)).unwrap()).unwrap();
+        let id = s
+            .increase_capacity(s.first.unwrap(), Some(IncreaseCapacity::Styles))
+            .unwrap();
+        assert_eq!(s.tracked_pin(h).unwrap().node, id);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(3, 12))
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_increase_capacity_returns_out_of_space_at_max_capacity() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let id = s.first.unwrap();
+        s.node_mut(id).unwrap().data.capacity.styles = u16::MAX;
+        assert_eq!(
+            s.increase_capacity(id, Some(IncreaseCapacity::Styles)),
+            Err(Error::OutOfSpace)
+        );
+    }
+    #[test]
+    fn page_list_increase_capacity_preserves_dirty_flag() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        s.node_mut(s.first.unwrap()).unwrap().data.dirty = true;
+        let id = s
+            .increase_capacity(s.first.unwrap(), Some(IncreaseCapacity::Styles))
+            .unwrap();
+        assert!(s.node(id).unwrap().data.dirty);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_page_iterator_single_page() {
+        let s = PageList::init(80, 24, None).unwrap();
+        let chunks: Vec<_> = s
+            .page_iterator(Direction::RightDown, active(0, 0), None)
+            .collect();
+        assert_eq!(chunks.len(), 1);
+        assert_eq!(
+            chunks[0],
+            Chunk {
+                node: s.first.unwrap(),
+                start: 0,
+                end: 24
+            }
+        );
+        assert!(chunks[0].full_page(&s));
+    }
+    #[test]
+    fn page_list_page_iterator_two_pages() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let cap = first_cap(&s);
+        grow(&mut s, cap - 12);
+        let chunks: Vec<_> = s
+            .page_iterator(Direction::RightDown, active(0, 0), None)
+            .collect();
+        assert_eq!(chunks.len(), 2);
+        assert_eq!(chunks[0].start, cap as u16 - 12);
+        assert_eq!(chunks[0].end, cap as u16);
+        assert_eq!(chunks[1].start, 0);
+        assert_eq!(chunks[1].end, 12);
+    }
+    #[test]
+    fn page_list_cell_iterator() {
+        let s = PageList::init(5, 3, None).unwrap();
+        let cells: Vec<_> = s
+            .cell_iterator(Direction::RightDown, screen(1, 0), Some(screen(3, 2)))
+            .collect();
+        assert_eq!(cells.len(), 13);
+        assert_eq!(cells.first().unwrap().x, 1);
+        assert_eq!(cells.last().unwrap().x, 3);
+    }
+    #[test]
+    fn page_list_page_iterator_reverse_single_page() {
+        let s = PageList::init(80, 24, None).unwrap();
+        let chunks: Vec<_> = s
+            .page_iterator(Direction::LeftUp, active(0, 0), None)
+            .collect();
+        assert_eq!(chunks.len(), 1);
+        assert_eq!(
+            chunks[0],
+            Chunk {
+                node: s.first.unwrap(),
+                start: 0,
+                end: 24
+            }
+        );
+        assert!(chunks[0].full_page(&s));
+    }
+    #[test]
+    fn page_list_page_iterator_reverse_two_pages() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let cap = first_cap(&s);
+        grow(&mut s, cap - 12);
+        let mut chunks: Vec<_> = s
+            .page_iterator(Direction::LeftUp, active(0, 0), None)
+            .collect();
+        chunks.reverse();
+        assert_eq!(chunks.len(), 2);
+        assert_eq!(chunks[0].start, cap as u16 - 12);
+        assert_eq!(chunks[0].end, cap as u16);
+        assert_eq!(chunks[1].start, 0);
+        assert_eq!(chunks[1].end, 12);
+    }
+    #[test]
+    fn page_list_cell_iterator_reverse() {
+        let s = PageList::init(5, 3, None).unwrap();
+        let cells: Vec<_> = s
+            .cell_iterator(Direction::LeftUp, screen(1, 0), Some(screen(3, 2)))
+            .collect();
+        assert_eq!(cells.len(), 13);
+        assert_eq!(cells.first().unwrap().x, 3);
+        assert_eq!(cells.last().unwrap().x, 1);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_more_rows() {
+        let mut s = PageList::init(10, 3, None).unwrap();
+        grow(&mut s, 0);
+        let h = s.track_pin(s.pin(active(0, 2)).unwrap()).unwrap();
+        s.resize(Resize {
+            rows: Some(10),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.rows, 10);
+        assert_eq!(s.total_rows, 10);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(0, 2))
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_more_rows_with_history() {
+        let mut s = PageList::init(10, 3, None).unwrap();
+        grow(&mut s, 50);
+        let h = s.track_pin(s.pin(active(0, 2)).unwrap()).unwrap();
+        s.resize(Resize {
+            rows: Some(5),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.rows, 5);
+        assert_eq!(s.total_rows, 53);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(0, 4))
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_less_rows() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        fill(&mut s);
+        s.resize(Resize {
+            rows: Some(5),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.rows, 5);
+        assert_eq!(s.total_rows, 10);
+        assert_eq!(s.active_offset(), 10 - 5);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_one_rows() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        fill(&mut s);
+        s.resize(Resize {
+            rows: Some(1),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.rows, 1);
+        assert_eq!(s.total_rows, 10);
+        assert_eq!(s.active_offset(), 10 - 1);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_less_cols() {
+        let mut s = PageList::init(10, 3, None).unwrap();
+        fill(&mut s);
+        s.resize(Resize {
+            cols: Some(5),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.cols, 5);
+        assert_eq!(s.total_rows, 3);
+        for n in s.nodes.iter().flatten() {
+            for y in 0..usize::from(n.data.size.rows) {
+                assert_eq!(n.data.get_cells(y).unwrap().len(), 5);
+            }
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_less_cols_pin_in_trimmed_cols() {
+        let mut s = PageList::init(10, 3, None).unwrap();
+        let h = s.track_pin(s.pin(active(9, 1)).unwrap()).unwrap();
+        s.resize(Resize {
+            cols: Some(5),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(4, 1))
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_more_cols() {
+        let mut s = PageList::init(5, 3, None).unwrap();
+        fill(&mut s);
+        s.resize(Resize {
+            cols: Some(10),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 3);
+        for y in 0..3 {
+            for x in 0..10 {
+                assert_eq!(
+                    s.get_cell(screen(x, y)).unwrap().codepoint(),
+                    if x < 5 { 65 } else { 0 }
+                );
+            }
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_no_reflow_less_cols_then_more_cols() {
+        let mut s = PageList::init(10, 3, None).unwrap();
+        fill(&mut s);
+        s.resize(Resize {
+            cols: Some(5),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        s.resize(Resize {
+            cols: Some(10),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        for y in 0..3 {
+            for x in 0..10 {
+                assert_eq!(
+                    s.get_cell(screen(x, y)).unwrap().codepoint(),
+                    if x < 5 { 65 } else { 0 }
+                );
+            }
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_reflow_more_cols_no_wrapped_rows() {
+        let mut s = PageList::init(5, 3, Some(0)).unwrap();
+        fill(&mut s);
+        s.resize(Resize {
+            cols: Some(10),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.cols, 10);
+        assert_eq!(s.total_rows, 3);
+        for p in s.row_iterator(Direction::RightDown, screen(0, 0), None) {
+            assert_eq!(p.row_and_cell(&s).unwrap().1.codepoint(), 65);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_reflow_more_cols_wrapped_rows() {
+        let mut s = PageList::init(2, 4, Some(0)).unwrap();
+        fill(&mut s);
+        wraps(&mut s);
+        s.resize(Resize {
+            cols: Some(4),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        assert_eq!(s.active_offset(), 0);
+        assert_eq!(s.diagram(), "AAAA\nAAAA\n    \n    \n");
+        assert!(
+            !s.get_top_left(Tag::Screen)
+                .unwrap()
+                .row_and_cell(&s)
+                .unwrap()
+                .0
+                .wrap()
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_reflow_less_cols_no_wrapped_rows() {
+        let mut s = PageList::init(10, 3, Some(0)).unwrap();
+        for y in 0..3 {
+            for x in 0..4 {
+                *s.get_cell_mut(screen(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        s.resize(Resize {
+            cols: Some(5),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 3);
+        for y in 0..3 {
+            for x in 0..4 {
+                assert_eq!(s.get_cell(screen(x, y)).unwrap().codepoint(), u32::from(x));
+            }
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_reflow_less_cols_wrapped_rows() {
+        let mut s = PageList::init(4, 2, None).unwrap();
+        for y in 0..2 {
+            for x in 0..4 {
+                *s.get_cell_mut(screen(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        assert_eq!(s.active_offset(), 2);
+        for y in 0..4 {
+            let p = s.pin(screen(0, y)).unwrap();
+            assert_eq!(p.row_and_cell(&s).unwrap().0.wrap(), y % 2 == 0);
+            assert_eq!(p.row_and_cell(&s).unwrap().1.codepoint(), (y % 2) * 2);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_reset() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 0);
+        s.reset().unwrap();
+        assert_eq!(s.viewport, Viewport::Active);
+        assert_eq!(s.total_rows, 24);
+        assert_eq!(s.get_top_left(Tag::Active).unwrap().node, s.first.unwrap());
+        finish(&s);
+    }
+    #[test]
+    fn page_list_reset_across_two_pages() {
+        let mut s = PageList::init(1000, 100, None).unwrap();
+        grow(&mut s, 0);
+        s.reset().unwrap();
+        assert_eq!(s.viewport, Viewport::Active);
+        assert_eq!(s.total_rows, 100);
+        assert_eq!(s.get_top_left(Tag::Active).unwrap().node, s.first.unwrap());
+        finish(&s);
+    }
+    #[test]
+    fn page_list_clears_history() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        grow(&mut s, 30);
+        s.reset().unwrap();
+        assert_eq!(s.viewport, Viewport::Active);
+        assert_eq!(s.total_rows, 24);
+        assert_eq!(s.get_top_left(Tag::Active).unwrap().node, s.first.unwrap());
+        finish(&s);
+    }
+    #[test]
+    fn page_list_reset_moves_tracked_pins_and_marks_them_as_garbage() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let h = s.track_pin(s.pin(active(42, 12)).unwrap()).unwrap();
+        s.reset().unwrap();
+        assert!(s.tracked_pin(h).unwrap().garbage);
+        assert!(!s.tracked_pin(s.viewport_pin.unwrap()).unwrap().garbage);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_at_middle_row() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        write_rows(&mut s);
+        let p = s.pin(screen(0, 5)).unwrap();
+        s.split(p).unwrap();
+        assert_eq!(s.total_pages(), 2);
+        assert_eq!(s.node(s.first.unwrap()).unwrap().data.size.rows, 5);
+        for y in 0..10 {
+            assert_eq!(s.get_cell(screen(0, y)).unwrap().codepoint(), y);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_at_row_0_is_no_op() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        write_rows(&mut s);
+        let p = s.pin(screen(0, 0)).unwrap();
+        s.split(p).unwrap();
+        assert_eq!(s.total_pages(), 1);
+        assert_eq!(s.node(s.first.unwrap()).unwrap().data.size.rows, 10);
+        for y in 0..10 {
+            assert_eq!(s.get_cell(screen(0, y)).unwrap().codepoint(), y);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_at_last_row() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        write_rows(&mut s);
+        let p = s.pin(screen(0, 9)).unwrap();
+        s.split(p).unwrap();
+        assert_eq!(s.total_pages(), 2);
+        assert_eq!(s.node(s.first.unwrap()).unwrap().data.size.rows, 9);
+        for y in 0..10 {
+            assert_eq!(s.get_cell(screen(0, y)).unwrap().codepoint(), y);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_single_row_page_returns_out_of_space() {
+        let mut s = PageList::init(10, 1, Some(0)).unwrap();
+        assert_eq!(
+            s.split(s.get_top_left(Tag::Active).unwrap()),
+            Err(Error::OutOfSpace)
+        );
+    }
+    #[test]
+    fn page_list_split_moves_tracked_pins() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        let h = s.track_pin(s.pin(screen(3, 7)).unwrap()).unwrap();
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!(p.node, s.last.unwrap());
+        assert_eq!(p.y, 2);
+        assert_eq!(p.x, 3);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_tracked_pin_before_split_point_unchanged() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        let h = s.track_pin(s.pin(screen(5, 2)).unwrap()).unwrap();
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!(p.node, s.first.unwrap());
+        assert_eq!(p.y, 2);
+        assert_eq!(p.x, 5);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_tracked_pin_at_split_point_moves_to_new_page() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        let h = s.track_pin(s.pin(screen(0, 5)).unwrap()).unwrap();
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!(p.node, s.last.unwrap());
+        assert_eq!(p.y, 0);
+        assert_eq!(p.x, 0);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_multiple_tracked_pins_across_regions() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        let handles: Vec<_> = (0..10)
+            .map(|y| s.track_pin(s.pin(screen(y, y as u32)).unwrap()).unwrap())
+            .collect();
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        for (y, h) in handles.iter().enumerate() {
+            let p = s.tracked_pin(*h).unwrap();
+            assert_eq!(
+                s.point_from_pin(Tag::Screen, p),
+                Some(screen(y as u16, y as u32))
+            );
+            assert_eq!(
+                p.node,
+                if y < 5 {
+                    s.first.unwrap()
+                } else {
+                    s.last.unwrap()
+                }
+            );
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_tracked_viewport_pin_in_split_region_moves_correctly() {
+        let mut s = PageList::init(10, 3, None).unwrap();
+        grow(&mut s, 7);
+        s.scroll(Scroll::Row(6));
+        let before = s.scrollbar();
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        assert_eq!(s.scrollbar(), before);
+        assert_eq!(
+            s.tracked_pin(s.viewport_pin.unwrap()).unwrap().node,
+            s.last.unwrap()
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_preserves_styled_cells() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        write_rows(&mut s);
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        for y in 0..10 {
+            page.set_style(
+                0,
+                y,
+                crate::style::Style {
+                    flags: crate::style::Flags {
+                        bold: true,
+                        ..crate::style::Flags::default()
+                    },
+                    ..crate::style::Style::default()
+                },
+            )
+            .unwrap();
+        }
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        for y in 0..10 {
+            let p = s.pin(screen(0, y)).unwrap();
+            assert!(p.style(&s).unwrap().flags.bold);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_preserves_grapheme_clusters() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        write_rows(&mut s);
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        for y in 1..10 {
+            page.append_grapheme(0, y, 0x301).unwrap();
+        }
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        for y in 0..10 {
+            let p = s.pin(screen(0, y)).unwrap();
+            if y > 0 {
+                assert_eq!(p.grapheme(&s).unwrap(), [0x301]);
+            }
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_preserves_hyperlinks() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        write_rows(&mut s);
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        let id = page
+            .insert_hyperlink(crate::hyperlink::Hyperlink {
+                id: crate::hyperlink::HyperlinkId::Implicit(1),
+                uri: b"https://example.com".to_vec(),
+            })
+            .unwrap();
+        for y in 0..10 {
+            if y > 0 {
+                page.hyperlink_set.r#use(id).unwrap();
+            }
+            page.set_hyperlink(0, y, id).unwrap();
+        }
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        for y in 0..10 {
+            let p = s.pin(screen(0, y)).unwrap();
+            assert!(p.row_and_cell(&s).unwrap().1.hyperlink());
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_preserves_wrap_flags() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        write_rows(&mut s);
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        for y in 0..10 {
+            page.rows[y].set_wrap(y % 2 == 0);
+            page.rows[y].set_wrap_continuation(y % 2 != 0);
+        }
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        for y in 0..10 {
+            let p = s.pin(screen(0, y)).unwrap();
+            assert_eq!(p.row_and_cell(&s).unwrap().0.wrap(), y % 2 == 0);
+            assert_eq!(
+                p.row_and_cell(&s).unwrap().0.wrap_continuation(),
+                y % 2 != 0
+            );
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_middle_page_preserves_linked_list_order() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        write_rows(&mut s);
+        let original = s.first;
+        s.split(s.pin(screen(0, 3)).unwrap()).unwrap();
+        s.split(s.pin(screen(0, 7)).unwrap()).unwrap();
+        s.split(s.pin(screen(0, 5)).unwrap()).unwrap();
+        assert_eq!(s.total_pages(), 4);
+        assert_eq!(s.first, original);
+        for y in 0..10 {
+            assert_eq!(s.get_cell(screen(0, y)).unwrap().codepoint(), y);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_last_page_makes_new_page_the_last() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        write_rows(&mut s);
+        let original = s.first;
+        s.split(s.pin(screen(0, 3)).unwrap()).unwrap();
+        s.split(s.pin(screen(0, 7)).unwrap()).unwrap();
+        assert_eq!(s.total_pages(), 3);
+        assert_eq!(s.first, original);
+        for y in 0..10 {
+            assert_eq!(s.get_cell(screen(0, y)).unwrap().codepoint(), y);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_split_first_page_keeps_original_as_first() {
+        let mut s = PageList::init(10, 10, None).unwrap();
+        write_rows(&mut s);
+        let original = s.first;
+        s.split(s.pin(screen(0, 7)).unwrap()).unwrap();
+        s.split(s.pin(screen(0, 3)).unwrap()).unwrap();
+        assert_eq!(s.total_pages(), 3);
+        assert_eq!(s.first, original);
+        for y in 0..10 {
+            assert_eq!(s.get_cell(screen(0, y)).unwrap().codepoint(), y);
+        }
+        finish(&s);
+    }
+    #[test]
+    fn page_list_compact_std_size_page_returns_null() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        assert_eq!(s.compact(s.first.unwrap()).unwrap(), None);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_compact_oversized_page() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        write_rows(&mut s);
+        let h = s.track_pin(s.pin(screen(2, 10)).unwrap()).unwrap();
+        let id = s
+            .increase_capacity(s.first.unwrap(), Some(IncreaseCapacity::StringBytes))
+            .unwrap();
+        let bytes = s.page_size;
+        let compact = s.compact(id).unwrap().unwrap();
+        assert!(s.page_size < bytes);
+        assert_eq!(s.tracked_pin(h).unwrap().node, compact);
+        for y in 0..24 {
+            assert_eq!(s.get_cell(screen(0, y)).unwrap().codepoint(), y);
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_clone_partial_trimmed_right() {
+        let mut s = PageList::init(80, 20, None).unwrap();
+        grow(&mut s, 30);
+        let (q, _) = s.clone_range(screen(0, 0), Some(screen(0, 39))).unwrap();
+        assert_eq!(q.total_rows, 40);
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone_partial_trimmed_left() {
+        let mut s = PageList::init(80, 20, None).unwrap();
+        grow(&mut s, 30);
+        let (q, _) = s.clone_range(screen(0, 10), None).unwrap();
+        assert_eq!(q.total_rows, 40);
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone_partial_trimmed_both() {
+        let mut s = PageList::init(80, 20, None).unwrap();
+        grow(&mut s, 30);
+        let (q, _) = s.clone_range(screen(0, 10), Some(screen(0, 35))).unwrap();
+        assert_eq!(q.total_rows, 26);
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone() {
+        let s = PageList::init(80, 24, None).unwrap();
+        let q = s.try_clone().unwrap();
+        assert_eq!(q.total_rows, 24);
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone_less_than_active() {
+        let s = PageList::init(80, 24, None).unwrap();
+        let (q, _) = s.clone_range(active(0, 5), None).unwrap();
+        assert_eq!(q.total_rows, 24);
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone_remap_tracked_pin() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let h = s.track_pin(s.pin(active(0, 6)).unwrap()).unwrap();
+        let (q, map) = s.clone_range(active(0, 5), None).unwrap();
+        assert_eq!(
+            q.point_from_pin(Tag::Active, q.tracked_pin(map[&h]).unwrap()),
+            Some(active(0, 1))
+        );
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone_remap_tracked_pin_not_in_cloned_area() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let h = s.track_pin(s.pin(active(0, 3)).unwrap()).unwrap();
+        let (q, map) = s.clone_range(active(0, 5), None).unwrap();
+        assert!(!map.contains_key(&h));
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone_full_dirty() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        for y in [0, 12, 23] {
+            s.pin(active(0, y)).unwrap().mark_dirty(&mut s);
+        }
+        let q = s.try_clone().unwrap();
+        for y in 0..24 {
+            assert_eq!(q.is_dirty(active(0, y)), [0, 12, 23].contains(&y));
+        }
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_clone_partial_trimmed_left_reclaims_styles() {
+        let mut s = PageList::init(80, 20, None).unwrap();
+        grow(&mut s, 30);
+        let p = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        for y in 0..10 {
+            p.set_style(
+                0,
+                y,
+                crate::style::Style {
+                    flags: crate::style::Flags {
+                        bold: true,
+                        ..Default::default()
+                    },
+                    ..Default::default()
+                },
+            )
+            .unwrap();
+        }
+        let (q, _) = s.clone_range(screen(0, 10), None).unwrap();
+        assert_eq!(q.total_rows, 40);
+        assert_eq!(q.node(q.first.unwrap()).unwrap().data.styles.count(), 0);
+        finish(&q);
+    }
+
+    #[test]
+    fn page_list_erase() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let bytes = s.page_size;
+        let cap = first_cap(&s);
+        grow(&mut s, cap * 5);
+        assert_eq!(s.total_pages(), 6);
+        let h = s.track_pin(s.pin(screen(0, 0)).unwrap()).unwrap();
+        s.erase_rows(Point::History(Coordinate::default()), None)
+            .unwrap();
+        assert_eq!(s.total_rows, 24);
+        assert_eq!(s.total_pages(), 1);
+        assert_eq!(s.page_size, bytes);
+        let pin = s.tracked_pin(h).unwrap();
+        assert_eq!(pin.node, s.first.unwrap());
+        assert_eq!((pin.x, pin.y), (0, 0));
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_reaccounts_page_size() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let bytes = s.page_size;
+        let cap = first_cap(&s);
+        grow(&mut s, cap * 5);
+        assert_eq!(s.total_pages(), 6);
+        let h = s.track_pin(s.pin(screen(0, 0)).unwrap()).unwrap();
+        s.erase_rows(Point::History(Coordinate::default()), None)
+            .unwrap();
+        assert_eq!(s.total_rows, 24);
+        assert_eq!(s.total_pages(), 1);
+        assert_eq!(s.page_size, bytes);
+        let pin = s.tracked_pin(h).unwrap();
+        assert_eq!(pin.node, s.first.unwrap());
+        assert_eq!((pin.x, pin.y), (0, 0));
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_row_with_tracked_pin_resets_to_top_left() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let bytes = s.page_size;
+        let cap = first_cap(&s);
+        grow(&mut s, cap * 5);
+        assert_eq!(s.total_pages(), 6);
+        let h = s.track_pin(s.pin(screen(0, 0)).unwrap()).unwrap();
+        s.erase_rows(Point::History(Coordinate::default()), None)
+            .unwrap();
+        assert_eq!(s.total_rows, 24);
+        assert_eq!(s.total_pages(), 1);
+        assert_eq!(s.page_size, bytes);
+        let pin = s.tracked_pin(h).unwrap();
+        assert_eq!(pin.node, s.first.unwrap());
+        assert_eq!((pin.x, pin.y), (0, 0));
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_row_with_tracked_pin_shifts() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let h = s.track_pin(s.pin(active(2, 4)).unwrap()).unwrap();
+        s.erase_rows(active(0, 0), Some(active(0, 3))).unwrap();
+        assert_eq!(s.total_rows, 24);
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!((p.x, p.y), (2, 0));
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_row_with_tracked_pin_is_erased() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let h = s.track_pin(s.pin(active(2, 2)).unwrap()).unwrap();
+        s.erase_rows(active(0, 0), Some(active(0, 3))).unwrap();
+        assert_eq!(s.total_rows, 24);
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!((p.x, p.y), (0, 0));
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_active_regrows_automatically() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        s.erase_rows(active(0, 0), None).unwrap();
+        assert_eq!(s.total_rows, 24);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_a_one_row_active() {
+        let mut s = PageList::init(80, 1, None).unwrap();
+        s.erase_rows(active(0, 0), None).unwrap();
+        assert_eq!(s.total_rows, 1);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_row_bounded_less_than_full_row() {
+        let mut s = PageList::init(80, 10, None).unwrap();
+        let handles: Vec<_> = [5, 8, 9]
+            .into_iter()
+            .map(|y| s.track_pin(s.pin(active(0, y)).unwrap()).unwrap())
+            .collect();
+        s.erase_row_bounded(active(0, 5), 3).unwrap();
+        for (h, expected) in handles.iter().zip([4, 7, 9]) {
+            assert_eq!(s.tracked_pin(*h).unwrap().y, expected);
+        }
+        for y in 5..8 {
+            assert!(s.is_dirty(active(0, y)));
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_row_bounded_with_pin_at_top() {
+        let mut s = PageList::init(80, 10, None).unwrap();
+        let h = s.track_pin(s.pin(active(5, 0)).unwrap()).unwrap();
+        s.erase_row_bounded(active(0, 0), 3).unwrap();
+        let p = s.tracked_pin(h).unwrap();
+        assert_eq!((p.x, p.y), (0, 0));
+        assert_eq!(s.total_rows, 10);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_erase_row_bounded_full_rows_single_page() {
+        let mut s = PageList::init(80, 10, None).unwrap();
+        let a = s.track_pin(s.pin(active(0, 7)).unwrap()).unwrap();
+        let b = s.track_pin(s.pin(active(0, 9)).unwrap()).unwrap();
+        s.erase_row_bounded(active(0, 5), 10).unwrap();
+        assert_eq!(s.tracked_pin(a).unwrap().y, 6);
+        assert_eq!(s.tracked_pin(b).unwrap().y, 8);
+        for y in 5..10 {
+            assert!(s.is_dirty(active(0, y)));
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_cursor_in_unchanged_row() {
+        let mut s = PageList::init(4, 2, None).unwrap();
+        for y in 0..2 {
+            for x in 0..2 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        let h = s.track_pin(s.pin(active(1, 0)).unwrap()).unwrap();
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(1, 0))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_cursor_in_blank_cell() {
+        let mut s = PageList::init(6, 2, None).unwrap();
+        for y in 0..2 {
+            for x in 0..2 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        let h = s.track_pin(s.pin(active(2, 0)).unwrap()).unwrap();
+        s.resize(Resize {
+            cols: Some(4),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(2, 0))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_cursor_in_final_blank_cell() {
+        let mut s = PageList::init(6, 2, None).unwrap();
+        for y in 0..2 {
+            for x in 0..2 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        let h = s.track_pin(s.pin(active(3, 0)).unwrap()).unwrap();
+        s.resize(Resize {
+            cols: Some(4),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(3, 0))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_cursor_in_wrapped_blank_cell() {
+        let mut s = PageList::init(6, 2, None).unwrap();
+        for y in 0..2 {
+            for x in 0..2 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        let h = s.track_pin(s.pin(active(5, 0)).unwrap()).unwrap();
+        s.resize(Resize {
+            cols: Some(4),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(3, 0))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_cursor_in_wrapped_row() {
+        let mut s = PageList::init(4, 2, None).unwrap();
+        for y in 0..2 {
+            for x in 0..4 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        let h = s.track_pin(s.pin(active(2, 1)).unwrap()).unwrap();
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(0, 1))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_blank_lines() {
+        let mut s = PageList::init(4, 3, Some(0)).unwrap();
+        for y in [0, 0] {
+            for x in 0..4 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 3);
+        assert_eq!(s.get_cell(active(0, 1)).unwrap().codepoint(), 2);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_blank_lines_between() {
+        let mut s = PageList::init(4, 3, Some(0)).unwrap();
+        for y in [0, 2] {
+            for x in 0..4 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 5);
+        assert_eq!(s.get_cell(active(0, 1)).unwrap().codepoint(), 0);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_blank_lines_between_no_scrollback() {
+        let mut s = PageList::init(5, 3, Some(0)).unwrap();
+        *s.get_cell_mut(active(0, 0)).unwrap() = Cell::init(65);
+        *s.get_cell_mut(active(0, 2)).unwrap() = Cell::init(67);
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 3);
+        assert_eq!(s.get_cell(active(0, 0)).unwrap().codepoint(), 65);
+        assert_eq!(s.get_cell(active(0, 1)).unwrap().codepoint(), 0);
+        assert_eq!(s.get_cell(active(0, 2)).unwrap().codepoint(), 67);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_cursor_not_on_last_line_preserves_location() {
+        let mut s = PageList::init(5, 5, Some(1)).unwrap();
+        for y in 0..5 {
+            for x in 0..2 {
+                *s.get_cell_mut(active(x, y)).unwrap() = Cell::init(u32::from(x));
+            }
+        }
+        grow(&mut s, 5);
+        let h = s.track_pin(s.pin(active(0, 0)).unwrap()).unwrap();
+        s.resize(Resize {
+            cols: Some(4),
+            cursor: Some(Cursor { x: 1, y: 1 }),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 10);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(0, 0))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_no_reflow_preserves_semantic_prompt_on_first_line() {
+        let mut s = PageList::init(4, 4, Some(0)).unwrap();
+        s.node_mut(s.first.unwrap()).unwrap().data.rows[0]
+            .set_semantic_prompt(SemanticPrompt::Prompt);
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        assert_eq!(
+            s.get_top_left(Tag::Active)
+                .unwrap()
+                .row_and_cell(&s)
+                .unwrap()
+                .0
+                .semantic_prompt(),
+            SemanticPrompt::Prompt
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_wrap_preserves_semantic_prompt() {
+        let mut s = PageList::init(4, 4, Some(0)).unwrap();
+        s.node_mut(s.first.unwrap()).unwrap().data.rows[0]
+            .set_semantic_prompt(SemanticPrompt::Prompt);
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        assert_eq!(
+            s.get_top_left(Tag::Active)
+                .unwrap()
+                .row_and_cell(&s)
+                .unwrap()
+                .0
+                .semantic_prompt(),
+            SemanticPrompt::Prompt
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_no_reflow_preserves_semantic_prompt() {
+        let mut s = PageList::init(4, 4, Some(0)).unwrap();
+        s.node_mut(s.first.unwrap()).unwrap().data.rows[1]
+            .set_semantic_prompt(SemanticPrompt::Prompt);
+        for x in 0..4 {
+            *s.get_cell_mut(active(x, 1)).unwrap() = Cell::init(u32::from(x));
+        }
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        for y in [1, 2] {
+            assert_eq!(
+                s.pin(active(0, y))
+                    .unwrap()
+                    .row_and_cell(&s)
+                    .unwrap()
+                    .0
+                    .semantic_prompt(),
+                SemanticPrompt::Prompt
+            );
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_to_wrap_a_wide_char() {
+        let mut s = PageList::init(3, 1, Some(0)).unwrap();
+        *s.get_cell_mut(active(0, 0)).unwrap() = Cell::init(120);
+        let c = s.get_cell_mut(active(1, 0)).unwrap();
+        *c = Cell::init(0x1f600);
+        c.set_wide(Wide::Wide);
+        s.get_cell_mut(active(2, 0))
+            .unwrap()
+            .set_wide(Wide::SpacerTail);
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        assert_eq!(s.get_cell(screen(1, 0)).unwrap().wide(), Wide::SpacerHead);
+        assert_eq!(s.get_cell(screen(0, 1)).unwrap().codepoint(), 0x1f600);
+        assert_eq!(s.get_cell(screen(1, 1)).unwrap().wide(), Wide::SpacerTail);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_more_cols_unwrap_still_requires_wide_spacer_head() {
+        let mut s = PageList::init(2, 2, Some(0)).unwrap();
+        for x in 0..2 {
+            *s.get_cell_mut(active(x, 0)).unwrap() = Cell::init(120);
+        }
+        wraps(&mut s);
+        let c = s.get_cell_mut(active(0, 1)).unwrap();
+        *c = Cell::init(0x1f600);
+        c.set_wide(Wide::Wide);
+        s.get_cell_mut(active(1, 1))
+            .unwrap()
+            .set_wide(Wide::SpacerTail);
+        s.resize(Resize {
+            cols: Some(3),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        assert_eq!(s.get_cell(screen(2, 0)).unwrap().wide(), Wide::SpacerHead);
+        assert_eq!(s.get_cell(screen(0, 1)).unwrap().codepoint(), 0x1f600);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_to_wrap_a_multi_codepoint_grapheme_with_a_spacer_head() {
+        let mut s = PageList::init(4, 2, Some(0)).unwrap();
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        let cps = [0x200d, 0x1f468, 0x200d, 0x1f466, 0x200d, 0x1f466];
+        for x in [0, 2] {
+            page.cells[x] = Cell::init(0x1f468);
+            page.cells[x].set_wide(Wide::Wide);
+            page.cells[x + 1].set_wide(Wide::SpacerTail);
+            page.set_graphemes(x, 0, &cps).unwrap();
+        }
+        s.resize(Resize {
+            cols: Some(3),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        for y in 0..2 {
+            let p = s.pin(screen(0, y)).unwrap();
+            assert_eq!(p.row_and_cell(&s).unwrap().1.wide(), Wide::Wide);
+            assert_eq!(p.grapheme(&s).unwrap(), cps);
+        }
+        assert_eq!(s.get_cell(screen(2, 0)).unwrap().wide(), Wide::SpacerHead);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_prompt_iterator_left_up() {
+        let mut s = PageList::init(2, 20, Some(0)).unwrap();
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        for y in [3, 6] {
+            page.rows[y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+        for y in [7, 8, 12] {
+            page.rows[y].set_semantic_prompt(SemanticPrompt::PromptContinuation);
+        }
+        let ys: Vec<_> = s
+            .prompt_iterator(Direction::LeftUp, screen(0, 0), None)
+            .map(|p| s.screen_row(p).unwrap())
+            .collect();
+        assert_eq!(ys, [12, 6, 3]);
+    }
+
+    #[test]
+    fn page_list_prompt_iterator_right_down() {
+        let mut s = PageList::init(2, 20, Some(0)).unwrap();
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        for y in [3, 6] {
+            page.rows[y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+        for y in [7, 8, 12] {
+            page.rows[y].set_semantic_prompt(SemanticPrompt::PromptContinuation);
+        }
+        let ys: Vec<_> = s
+            .prompt_iterator(Direction::RightDown, screen(0, 0), None)
+            .map(|p| s.screen_row(p).unwrap())
+            .collect();
+        assert_eq!(ys, [3, 6, 12]);
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_prompt() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..5 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('A' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 5..8 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('B' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(2, 5)).unwrap(), SemanticContent::Prompt);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(0, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(7, 5)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_prompt_with_output() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..3 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 3..7 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('l' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+
+            for x in 7..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Prompt);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(0, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(6, 5)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_prompt_multiline() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+        }
+
+        {
+            for x in 0..5 {
+                let cell = &mut page.get_cells_mut(6).unwrap()[x];
+                *cell = Cell::init('c' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(2, 5)).unwrap(), SemanticContent::Prompt);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(0, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(4, 6)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_prompt_only() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..5 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Prompt);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(0, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(4, 5)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_prompt_to_end_of_screen() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 15;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..3 {
+                let cell = &mut page.get_cells_mut(15).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 3..8 {
+                let cell = &mut page.get_cells_mut(15).unwrap()[x];
+                *cell = Cell::init('c' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 15)).unwrap(), SemanticContent::Prompt);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(0, 15)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(7, 15)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_input_basic() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..3 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 3..8 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('l' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl = s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Input);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(3, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(7, 5)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_input_with_output() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..5 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('c' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+
+            for x in 5..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl = s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Input);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(2, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(4, 5)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_input_multiline_with_continuation() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('c' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(6).unwrap()[x];
+                *cell = Cell::init('>' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..6 {
+                let cell = &mut page.get_cells_mut(6).unwrap()[x];
+                *cell = Cell::init('d' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl = s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Input);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(2, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(5, 6)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_input_no_input_returns_null() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..3 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 3..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl = s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Input);
+        assert!(hl.is_none());
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_input_to_end_of_screen() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 15;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(15).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..7 {
+                let cell = &mut page.get_cells_mut(15).unwrap()[x];
+                *cell = Cell::init('c' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 15)).unwrap(), SemanticContent::Input);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(2, 15)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(6, 15)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_input_prompt_only_returns_null() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+        }
+
+        {
+            for y in 6..10 {
+                for x in 0..10 {
+                    let cell = &mut page.get_cells_mut(y).unwrap()[x];
+                    cell.set_semantic_content(SemanticContent::Prompt);
+                }
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl = s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Input);
+        assert!(hl.is_none());
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_output_basic() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..5 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('l' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+
+            for x in 5..8 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+
+            for x in 8..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Output);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(5, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(7, 5)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_output_multiline() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..4 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('l' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+
+            for x in 4..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+        }
+
+        {
+            for x in 0..10 {
+                let cell = &mut page.get_cells_mut(6).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+        }
+
+        {
+            for x in 0..5 {
+                let cell = &mut page.get_cells_mut(7).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+            for x in 5..10 {
+                let cell = &mut page.get_cells_mut(7).unwrap()[x];
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Output);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(4, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(4, 7)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_output_stops_at_next_prompt() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..4 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('l' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+
+            for x in 4..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+        }
+
+        {
+            for x in 0..3 {
+                let cell = &mut page.get_cells_mut(6).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+
+            for x in 3..6 {
+                let cell = &mut page.get_cells_mut(6).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Output);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(4, 5)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(2, 6)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_output_to_end_of_screen() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 15;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..2 {
+                let cell = &mut page.get_cells_mut(15).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 2..4 {
+                let cell = &mut page.get_cells_mut(15).unwrap()[x];
+                *cell = Cell::init('c' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+
+            for x in 4..10 {
+                let cell = &mut page.get_cells_mut(15).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+        }
+
+        {
+            for x in 0..8 {
+                let cell = &mut page.get_cells_mut(16).unwrap()[x];
+                *cell = Cell::init('o' as u32);
+                cell.set_semantic_content(SemanticContent::Output);
+            }
+            for x in 8..10 {
+                let cell = &mut page.get_cells_mut(16).unwrap()[x];
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 15)).unwrap(), SemanticContent::Output);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(4, 15)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(7, 16)));
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_output_no_output_returns_null() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..3 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+
+            for x in 3..10 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('c' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            for y in 6..10 {
+                for x in 0..10 {
+                    let cell = &mut page.get_cells_mut(y).unwrap()[x];
+                    cell.set_semantic_content(SemanticContent::Input);
+                }
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Output);
+        assert!(hl.is_none());
+    }
+
+    #[test]
+    fn page_list_highlight_semantic_content_output_skips_empty_cells() {
+        let mut s = PageList::init(10, 20, Some(0)).unwrap();
+
+        let page = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+
+        {
+            let rac_y = 5;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+
+            for x in 0..3 {
+                let cell = &mut page.get_cells_mut(5).unwrap()[x];
+                *cell = Cell::init('$' as u32);
+                cell.set_semantic_content(SemanticContent::Prompt);
+            }
+        }
+
+        {
+            for x in 0..4 {
+                let cell = &mut page.get_cells_mut(6).unwrap()[x];
+                *cell = Cell::init('l' as u32);
+                cell.set_semantic_content(SemanticContent::Input);
+            }
+        }
+
+        {
+            for y in 7..9 {
+                for x in 0..5 {
+                    let cell = &mut page.get_cells_mut(y).unwrap()[x];
+                    *cell = Cell::init('o' as u32);
+                    cell.set_semantic_content(SemanticContent::Output);
+                }
+            }
+        }
+
+        {
+            let rac_y = 10;
+            page.rows[rac_y].set_semantic_prompt(SemanticPrompt::Prompt);
+        }
+
+        let hl =
+            s.highlight_semantic_content(s.pin(screen(0, 5)).unwrap(), SemanticContent::Output);
+        let hl = hl.unwrap();
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.0), Some(screen(0, 7)));
+        assert_eq!(s.point_from_pin(Tag::Screen, hl.1), Some(screen(4, 8)));
+    }
+    #[test]
+    fn page_list_resize_no_reflow_less_rows_trims_blank_lines() {
+        let mut s = PageList::init(10, 5, Some(0)).unwrap();
+        *s.get_cell_mut(active(0, 0)).unwrap() = Cell::init(65);
+        let h = s.track_pin(s.pin(active(0, 0)).unwrap()).unwrap();
+        s.resize(Resize {
+            rows: Some(2),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 2);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(0, 0))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_no_reflow_less_rows_trims_blank_lines_cursor_in_blank_line() {
+        let mut s = PageList::init(10, 5, Some(0)).unwrap();
+        *s.get_cell_mut(active(0, 0)).unwrap() = Cell::init(65);
+        let h = s.track_pin(s.pin(active(0, 3)).unwrap()).unwrap();
+        s.resize(Resize {
+            rows: Some(2),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        assert_eq!(
+            s.point_from_pin(Tag::Active, s.tracked_pin(h).unwrap()),
+            Some(active(0, 1))
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_no_reflow_less_rows_trims_blank_lines_erases_pages() {
+        let mut s = PageList::init(100, 5, Some(0)).unwrap();
+        let rows = first_cap(&s) as u16 + 5;
+        s.resize(Resize {
+            rows: Some(rows),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_pages(), 2);
+        *s.get_cell_mut(active(0, 0)).unwrap() = Cell::init(65);
+        s.resize(Resize {
+            rows: Some(5),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_pages(), 1);
+        assert_eq!(s.total_rows, 5);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_no_reflow_more_rows_extends_blank_lines() {
+        let mut s = PageList::init(10, 3, Some(0)).unwrap();
+        *s.get_cell_mut(active(0, 0)).unwrap() = Cell::init(65);
+        s.resize(Resize {
+            rows: Some(7),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 7);
+        assert_eq!(s.active_offset(), 0);
+        assert_eq!(s.get_cell(active(0, 0)).unwrap().codepoint(), 65);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_no_reflow_less_cols_clears_graphemes() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        let p = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        p.cells[9] = Cell::init(9);
+        p.append_grapheme(9, 0, 10).unwrap();
+        assert_eq!(p.grapheme_count(), 1);
+        s.resize(Resize {
+            cols: Some(5),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 10);
+        for n in s.nodes.iter().flatten() {
+            assert_eq!(n.data.grapheme_count(), 0);
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_no_reflow_less_rows_and_cols() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        s.resize(Resize {
+            cols: Some(5),
+            rows: Some(7),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.cols, 5);
+        assert_eq!(s.rows, 7);
+        assert_eq!(s.total_rows, 7);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_no_reflow_more_rows_and_less_cols() {
+        let mut s = PageList::init(10, 10, Some(0)).unwrap();
+        s.resize(Resize {
+            cols: Some(5),
+            rows: Some(20),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.cols, 5);
+        assert_eq!(s.rows, 20);
+        assert_eq!(s.total_rows, 20);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_no_reflow_empty_screen() {
+        let mut s = PageList::init(5, 5, Some(0)).unwrap();
+        s.resize(Resize {
+            cols: Some(10),
+            rows: Some(10),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.cols, 10);
+        assert_eq!(s.rows, 10);
+        assert_eq!(s.total_rows, 10);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_increase_capacity_after_col_shrink() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        s.resize(Resize {
+            cols: Some(40),
+            reflow: false,
+            ..Resize::default()
+        })
+        .unwrap();
+        let id = s
+            .increase_capacity(s.first.unwrap(), Some(IncreaseCapacity::Styles))
+            .unwrap();
+        assert_eq!(s.node(id).unwrap().data.size.cols, 40);
+        assert_eq!(s.node(id).unwrap().data.capacity.cols, 80);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_increase_capacity_multi_page() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        fill_pages(&mut s, 2);
+        let old = s.first.unwrap();
+        let second = s.node(old).unwrap().next.unwrap();
+        let h = s
+            .track_pin(Pin {
+                node: old,
+                y: 2,
+                x: 3,
+                garbage: false,
+            })
+            .unwrap();
+        let id = s
+            .increase_capacity(old, Some(IncreaseCapacity::Styles))
+            .unwrap();
+        assert_eq!(s.node(id).unwrap().next, Some(second));
+        assert_eq!(s.node(second).unwrap().prev, Some(id));
+        assert_eq!(s.tracked_pin(h).unwrap().node, id);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_compact_insufficient_savings_returns_null() {
+        let mut s = PageList::init(80, 24, Some(0)).unwrap();
+        let id = s
+            .increase_capacity(s.first.unwrap(), Some(IncreaseCapacity::GraphemeBytes))
+            .unwrap();
+        let bytes = s.page_size;
+        let result = s.compact(id).unwrap();
+        if result.is_some() {
+            assert!(s.page_size < bytes);
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_page_iterator_history_two_pages() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let cap = first_cap(&s);
+        fill_pages(&mut s, 2);
+        let chunks: Vec<_> = s
+            .page_iterator(
+                Direction::RightDown,
+                Point::History(Coordinate::default()),
+                None,
+            )
+            .collect();
+        assert_eq!(chunks.len(), 2);
+        assert_eq!((chunks[0].start, chunks[0].end), (0, cap as u16));
+        assert_eq!((chunks[1].start, chunks[1].end), (0, cap as u16 - 24));
+    }
+
+    #[test]
+    fn page_list_page_iterator_reverse_history_two_pages() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let cap = first_cap(&s);
+        fill_pages(&mut s, 2);
+        let mut chunks: Vec<_> = s
+            .page_iterator(
+                Direction::LeftUp,
+                Point::History(Coordinate::default()),
+                None,
+            )
+            .collect();
+        chunks.reverse();
+        assert_eq!(chunks.len(), 2);
+        assert_eq!((chunks[0].start, chunks[0].end), (0, cap as u16));
+        assert_eq!((chunks[1].start, chunks[1].end), (0, cap as u16 - 24));
+    }
+
+    #[test]
+    fn page_list_erase_row_bounded_full_rows_two_pages() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        let cap = first_cap(&s);
+        fill_pages(&mut s, 2);
+        write_rows(&mut s);
+        let h = s.track_pin(s.pin(screen(2, cap as u32)).unwrap()).unwrap();
+        let counts: Vec<_> = s.nodes.iter().flatten().map(|n| n.data.size.rows).collect();
+        s.erase_row_bounded(screen(0, cap as u32 - 2), 10).unwrap();
+        assert_eq!(
+            s.nodes
+                .iter()
+                .flatten()
+                .map(|n| n.data.size.rows)
+                .collect::<Vec<_>>(),
+            counts
+        );
+        assert_eq!(
+            s.point_from_pin(Tag::Screen, s.tracked_pin(h).unwrap()),
+            Some(screen(2, cap as u32 - 1))
+        );
+        assert_eq!(
+            s.get_cell(screen(0, cap as u32 - 2)).unwrap().codepoint(),
+            cap as u32 - 1
+        );
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_wrapped_rows_with_graphemes() {
+        let mut s = PageList::init(4, 2, None).unwrap();
+        let p = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        for y in 0..2 {
+            for x in 0..4 {
+                let i = p.cell_index(x, y).unwrap();
+                p.cells[i] = Cell::init(x as u32 + 1);
+                p.append_grapheme(x, y, 10).unwrap();
+            }
+        }
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        for pin in s.cell_iterator(Direction::RightDown, screen(0, 0), None) {
+            assert_eq!(pin.grapheme(&s).unwrap(), [10]);
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_copy_style() {
+        let mut s = PageList::init(4, 2, None).unwrap();
+        fill(&mut s);
+        let p = &mut s.node_mut(s.first.unwrap()).unwrap().data;
+        let style = crate::style::Style {
+            fg_color: crate::style::Color::Palette(2),
+            ..Default::default()
+        };
+        for y in 0..2 {
+            for x in 0..4 {
+                p.set_style(x, y, style).unwrap();
+            }
+        }
+        s.resize(Resize {
+            cols: Some(2),
+            ..Resize::default()
+        })
+        .unwrap();
+        for pin in s.cell_iterator(Direction::RightDown, screen(0, 0), None) {
+            assert_eq!(pin.style(&s).unwrap(), style);
+        }
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_less_cols_wraps_spacer_head() {
+        let mut s = PageList::init(4, 3, Some(0)).unwrap();
+        for x in 0..3 {
+            *s.get_cell_mut(active(x, 0)).unwrap() = Cell::init(120);
+        }
+        s.get_cell_mut(active(3, 0))
+            .unwrap()
+            .set_wide(Wide::SpacerHead);
+        s.node_mut(s.first.unwrap()).unwrap().data.rows[0].set_wrap(true);
+        s.node_mut(s.first.unwrap()).unwrap().data.rows[1].set_wrap_continuation(true);
+        let c = s.get_cell_mut(active(0, 1)).unwrap();
+        *c = Cell::init(0x1f600);
+        c.set_wide(Wide::Wide);
+        s.get_cell_mut(active(1, 1))
+            .unwrap()
+            .set_wide(Wide::SpacerTail);
+        s.resize(Resize {
+            cols: Some(3),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 3);
+        for x in 0..3 {
+            assert_eq!(s.get_cell(screen(x, 0)).unwrap().codepoint(), 120);
+        }
+        assert_eq!(s.get_cell(screen(0, 1)).unwrap().codepoint(), 0x1f600);
+        finish(&s);
+    }
+
+    #[test]
+    fn page_list_resize_reflow_more_cols_no_reflow_preserves_semantic_prompt() {
+        let mut s = PageList::init(4, 4, Some(0)).unwrap();
+        s.node_mut(s.first.unwrap()).unwrap().data.rows[0]
+            .set_semantic_prompt(SemanticPrompt::Prompt);
+        s.resize(Resize {
+            cols: Some(8),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 4);
+        assert_eq!(
+            s.get_top_left(Tag::Active)
+                .unwrap()
+                .row_and_cell(&s)
+                .unwrap()
+                .0
+                .semantic_prompt(),
+            SemanticPrompt::Prompt
+        );
+        finish(&s);
+    }
+    #[test]
+    fn page_list_scroll_clear() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        *s.get_cell_mut(active(0, 0)).unwrap() = Cell::init(65);
+        s.scroll_clear().unwrap();
+        assert_eq!(s.total_rows, 25);
+        assert_eq!(s.get_cell(active(0, 0)).unwrap().codepoint(), 0);
+        s.scroll_clear().unwrap();
+        assert_eq!(s.total_rows, 25);
+        finish(&s);
+    }
+    #[test]
+    fn page_list_resize_reflow_less_cols_to_eliminate_a_wide_char() {
+        let mut s = PageList::init(2, 1, Some(0)).unwrap();
+        let c = s.get_cell_mut(active(0, 0)).unwrap();
+        *c = Cell::init(0x1f600);
+        c.set_wide(Wide::Wide);
+        s.get_cell_mut(active(1, 0))
+            .unwrap()
+            .set_wide(Wide::SpacerTail);
+        s.resize(Resize {
+            cols: Some(1),
+            ..Resize::default()
+        })
+        .unwrap();
+        assert_eq!(s.total_rows, 1);
+        assert_eq!(s.get_cell(active(0, 0)).unwrap(), Cell::default());
+        finish(&s);
+    }
+    #[test]
+    fn stale_tracked_handle_cannot_release_reused_slot() {
+        let mut s = PageList::init(4, 2, None).unwrap();
+        let p = s.get_top_left(Tag::Active).unwrap();
+        let old = s.track_pin(p).unwrap();
+        s.untrack_pin(old);
+        let new = s.track_pin(p).unwrap();
+        s.untrack_pin(old);
+        assert!(s.tracked_pin(old).is_none());
+        assert_eq!(s.tracked_pin(new), Some(p));
+        finish(&s);
+    }
+    #[test]
+    fn row_erasure_retains_page_dimensions_and_cursor_row() {
+        let mut s = PageList::init(80, 24, None).unwrap();
+        fill_pages(&mut s, 2);
+        write_rows(&mut s);
+        let p = s.pin(screen(3, 5)).unwrap();
+        let h = s.track_pin(p).unwrap();
+        let total = s.total_rows;
+        let cap = first_cap(&s);
+        s.erase_row(screen(0, 5)).unwrap();
+        assert_eq!(s.total_rows, total);
+        assert_eq!(first_cap(&s), cap);
+        assert_eq!(s.tracked_pin(h), Some(p));
+        assert_eq!(s.get_cell(screen(0, 5)).unwrap().codepoint(), 6);
+        finish(&s);
+    }
+}

crates/ghostty-terminal/src/point.rs

@@ -0,0 +1,65 @@
+//! Coordinates relative to the active area, viewport, screen, or history.
+/// Reference frame for a terminal coordinate.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum Tag {
+    /// Editable bottommost screen area, including unwritten rows.
+    Active,
+    /// Visible area, including user scrolling.
+    Viewport,
+    /// Entire screen including scrollback.
+    Screen,
+    /// Scrollback preceding the active area.
+    History,
+}
+/// An x/y coordinate; history may exceed a single page's row count.
+#[derive(Debug, Default, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct Coordinate {
+    /// Column.
+    pub x: u16,
+    /// Row relative to the point's reference frame.
+    pub y: u32,
+}
+impl Coordinate {
+    /// Compare both coordinates.
+    pub fn eql(self, other: Self) -> bool {
+        self == other
+    }
+}
+/// A coordinate with its reference frame.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum Point {
+    /// Editable screen coordinate.
+    Active(Coordinate),
+    /// Visible viewport coordinate.
+    Viewport(Coordinate),
+    /// Whole-screen coordinate.
+    Screen(Coordinate),
+    /// Scrollback coordinate.
+    History(Coordinate),
+}
+impl Point {
+    /// Construct a point in a given frame.
+    pub const fn new(tag: Tag, coord: Coordinate) -> Self {
+        match tag {
+            Tag::Active => Self::Active(coord),
+            Tag::Viewport => Self::Viewport(coord),
+            Tag::Screen => Self::Screen(coord),
+            Tag::History => Self::History(coord),
+        }
+    }
+    /// Extract its coordinate.
+    pub const fn coord(self) -> Coordinate {
+        match self {
+            Self::Active(v) | Self::Viewport(v) | Self::Screen(v) | Self::History(v) => v,
+        }
+    }
+    /// Extract its reference frame.
+    pub const fn tag(self) -> Tag {
+        match self {
+            Self::Active(_) => Tag::Active,
+            Self::Viewport(_) => Tag::Viewport,
+            Self::Screen(_) => Tag::Screen,
+            Self::History(_) => Tag::History,
+        }
+    }
+}

crates/ghostty-terminal/src/ref_counted_set.rs

@@ -0,0 +1,252 @@
+//! Bounded, deduplicated values with stable nonzero identifiers.
+use std::{collections::HashMap, hash::Hash};
+/// Errors callers can recover from by rebuilding or growing a page.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum AddError {
+    /// The set has exhausted its logical capacity.
+    OutOfMemory,
+    /// Dead low IDs prevent allocating another sequential ID.
+    NeedsRehash,
+    /// Identifier does not refer to a live entry.
+    InvalidId,
+    /// A reference count would overflow or underflow.
+    InvalidRefCount,
+}
+impl std::fmt::Display for AddError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{self:?}")
+    }
+}
+impl std::error::Error for AddError {}
+/// Logical layout of the Zig set, independent of Rust collection overhead.
+#[derive(Debug, Default, Copy, Clone, PartialEq, Eq)]
+pub struct Layout {
+    /// Slots including reserved ID zero.
+    pub cap: usize,
+    /// Power-of-two hash table capacity.
+    pub table_cap: usize,
+    /// Table byte offset.
+    pub table_start: usize,
+    /// Item byte offset.
+    pub items_start: usize,
+    /// Total byte requirement.
+    pub total_size: usize,
+}
+impl Layout {
+    /// Calculate a layout using the reference ABI's item size and alignment.
+    pub fn init(cap: usize, item_size: usize, item_align: usize) -> Self {
+        if cap == 0 {
+            return Self::default();
+        }
+        let table_cap = cap.next_power_of_two();
+        let items_start = (table_cap * 2).next_multiple_of(item_align);
+        let cap = table_cap * 13 / 16;
+        Self {
+            cap,
+            table_cap,
+            table_start: 0,
+            items_start,
+            total_size: items_start + cap * item_size,
+        }
+    }
+}
+#[derive(Debug, Clone)]
+struct Item<T> {
+    value: T,
+    refs: u16,
+}
+/// A slot array and deduplication map. ID zero is always reserved.
+#[derive(Debug, Clone)]
+pub struct RefCountedSet<T> {
+    slots: Vec<Option<Item<T>>>,
+    lookup: HashMap<T, u16>,
+    next_id: usize,
+    living: usize,
+}
+impl<T: Eq + Hash + Clone> RefCountedSet<T> {
+    /// Construct with Zig's 13/16 load factor and power-of-two rounding.
+    pub fn init(cap: usize) -> Result<Self, AddError> {
+        if cap > 65536 {
+            return Err(AddError::OutOfMemory);
+        }
+        let slots_len = if cap == 0 {
+            0
+        } else {
+            cap.next_power_of_two() * 13 / 16
+        };
+        let mut slots = Vec::new();
+        slots
+            .try_reserve_exact(slots_len)
+            .map_err(|_| AddError::OutOfMemory)?;
+        slots.resize_with(slots_len, || None);
+        Ok(Self {
+            slots,
+            lookup: HashMap::new(),
+            next_id: 1,
+            living: 0,
+        })
+    }
+    /// Minimum table capacity for a given number of live values.
+    pub fn capacity_for_count(n: usize) -> usize {
+        if n == 0 {
+            0
+        } else {
+            ((n + 1) * 16).div_ceil(13)
+        }
+    }
+    /// Maximum number of live values, excluding ID zero.
+    pub fn capacity(&self) -> usize {
+        self.slots.len().saturating_sub(1)
+    }
+    /// Number of values with nonzero reference counts.
+    pub fn count(&self) -> usize {
+        self.living
+    }
+    /// Look up a live value without retaining it.
+    pub fn lookup(&self, value: &T) -> Option<u16> {
+        self.lookup.get(value).copied()
+    }
+    /// Add or retain a value, trimming unused trailing IDs first.
+    pub fn add(&mut self, value: T) -> Result<u16, AddError> {
+        while self.next_id > 1
+            && self.slots[self.next_id - 1]
+                .as_ref()
+                .is_none_or(|v| v.refs == 0)
+        {
+            self.next_id -= 1;
+            self.slots[self.next_id] = None;
+        }
+        if let Some(id) = self.lookup(&value) {
+            self.r#use(id)?;
+            return Ok(id);
+        }
+        if self.next_id >= self.slots.len() {
+            return Err(if self.living < self.slots.len() * 9 / 10 {
+                AddError::NeedsRehash
+            } else {
+                AddError::OutOfMemory
+            });
+        }
+        self.lookup
+            .try_reserve(1)
+            .map_err(|_| AddError::OutOfMemory)?;
+        let id = self.next_id as u16;
+        self.lookup.insert(value.clone(), id);
+        self.slots[self.next_id] = Some(Item { value, refs: 1 });
+        self.next_id += 1;
+        self.living += 1;
+        Ok(id)
+    }
+    /// Prefer an already allocated ID; return None when that ID was retained.
+    pub fn add_with_id(&mut self, value: T, id: u16) -> Result<Option<u16>, AddError> {
+        if id == 0 {
+            return Err(AddError::InvalidId);
+        }
+        if usize::from(id) < self.next_id {
+            if self.get(id) == Some(&value) {
+                self.r#use(id)?;
+                return Ok(None);
+            }
+            if self.ref_count(id) == 0 {
+                if let Some(other) = self.lookup(&value) {
+                    self.r#use(other)?;
+                    return Ok(Some(other));
+                }
+                self.lookup
+                    .try_reserve(1)
+                    .map_err(|_| AddError::OutOfMemory)?;
+                self.lookup.insert(value.clone(), id);
+                self.slots[usize::from(id)] = Some(Item { value, refs: 1 });
+                self.living += 1;
+                return Ok(None);
+            }
+        }
+        self.add(value).map(Some)
+    }
+    /// Retain a live value once.
+    pub fn r#use(&mut self, id: u16) -> Result<(), AddError> {
+        self.use_multiple(id, 1)
+    }
+    /// Retain a live value multiple times.
+    pub fn use_multiple(&mut self, id: u16, n: u16) -> Result<(), AddError> {
+        let item = self
+            .slots
+            .get_mut(usize::from(id))
+            .and_then(Option::as_mut)
+            .filter(|i| i.refs > 0)
+            .ok_or(AddError::InvalidId)?;
+        item.refs = item.refs.checked_add(n).ok_or(AddError::InvalidRefCount)?;
+        Ok(())
+    }
+    /// Obtain a live value without retaining it.
+    pub fn get(&self, id: u16) -> Option<&T> {
+        self.slots
+            .get(usize::from(id))?
+            .as_ref()
+            .filter(|i| i.refs > 0)
+            .map(|i| &i.value)
+    }
+    /// Release one reference. Dead values remain in their slots until reuse.
+    pub fn release(&mut self, id: u16) -> Result<(), AddError> {
+        self.release_multiple(id, 1)
+    }
+    /// Release several references.
+    pub fn release_multiple(&mut self, id: u16, n: u16) -> Result<(), AddError> {
+        let item = self
+            .slots
+            .get_mut(usize::from(id))
+            .and_then(Option::as_mut)
+            .filter(|i| i.refs > 0)
+            .ok_or(AddError::InvalidId)?;
+        item.refs = item.refs.checked_sub(n).ok_or(AddError::InvalidRefCount)?;
+        if item.refs == 0 {
+            self.lookup.remove(&item.value);
+            self.living -= 1;
+        }
+        Ok(())
+    }
+    /// Read the reference count, or zero for an absent ID.
+    pub fn ref_count(&self, id: u16) -> u16 {
+        self.slots
+            .get(usize::from(id))
+            .and_then(Option::as_ref)
+            .map_or(0, |i| i.refs)
+    }
+    pub(crate) fn contains_slot(&self, id: u16) -> bool {
+        self.slots.get(usize::from(id)).is_some_and(Option::is_some)
+    }
+    /// Iterate live IDs, values, and their reference counts.
+    pub fn entries(&self) -> impl Iterator<Item = (u16, &T, u16)> {
+        self.slots.iter().enumerate().filter_map(|(id, i)| {
+            i.as_ref()
+                .filter(|i| i.refs > 0)
+                .map(|i| (id as u16, &i.value, i.refs))
+        })
+    }
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn capacity_and_rehash() {
+        let mut s = RefCountedSet::init(16).unwrap();
+        let ids: Vec<_> = (0..12).map(|n| s.add(n).unwrap()).collect();
+        assert_eq!(s.add(99), Err(AddError::OutOfMemory));
+        s.release(ids[0]).unwrap();
+        s.release(ids[1]).unwrap();
+        assert_eq!(s.add(99), Err(AddError::NeedsRehash));
+        assert_eq!(s.add_with_id(99, ids[0]).unwrap(), None);
+        assert_eq!(s.count(), 11);
+    }
+    #[test]
+    fn trailing_reuse_and_dedup() {
+        let mut s = RefCountedSet::init(4).unwrap();
+        let a = s.add(1).unwrap();
+        let b = s.add(2).unwrap();
+        assert_eq!(s.add(1).unwrap(), a);
+        s.release(b).unwrap();
+        assert_eq!(s.add(3).unwrap(), b);
+        assert_eq!(s.ref_count(a), 2);
+        assert_eq!(s.r#use(0), Err(AddError::InvalidId));
+    }
+}

crates/ghostty-terminal/src/size.rs

@@ -0,0 +1,44 @@
+//! Integer widths and safe logical offsets used by terminal pages.
+use std::marker::PhantomData;
+/// Maximum addressable page size.
+pub const MAX_PAGE_SIZE: u32 = u32::MAX;
+/// Byte offset within a page.
+pub type OffsetInt = u32;
+/// Number of cells in a grid dimension.
+pub type CellCountInt = u16;
+/// Style capacity and identifiers.
+pub type StyleCountInt = u16;
+/// Hyperlink capacity and identifiers.
+pub type HyperlinkCountInt = u16;
+/// Bytes of grapheme storage.
+pub type GraphemeBytesInt = u32;
+/// Bytes of string storage.
+pub type StringBytesInt = u32;
+/// A typed logical byte offset; never converted to a raw pointer.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[repr(transparent)]
+pub struct Offset<T> {
+    offset: u32,
+    marker: PhantomData<fn() -> T>,
+}
+impl<T> Offset<T> {
+    /// Construct a logical byte offset.
+    pub const fn new(offset: u32) -> Self {
+        Self {
+            offset,
+            marker: PhantomData,
+        }
+    }
+    /// Return the byte displacement.
+    pub const fn offset(self) -> u32 {
+        self.offset
+    }
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn offset() {
+        assert_eq!(std::mem::size_of::<Offset<u8>>(), 4);
+    }
+}

crates/ghostty-terminal/src/style.rs

@@ -0,0 +1,763 @@
+//! Cell styles, color resolution, and VT/HTML serialization.
+use crate::page::{Cell, ContentTag};
+use ghostty_vt::{
+    color::{Palette, Rgb},
+    sgr::Underline,
+};
+use std::{
+    fmt,
+    hash::{Hash, Hasher},
+};
+/// Nonzero page-local style identifier.
+pub type Id = u16;
+/// The default style needs no set lookup.
+pub const DEFAULT_ID: Id = 0;
+/// A style color retains its palette or RGB origin.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Color {
+    /// Unspecified terminal default.
+    #[default]
+    None,
+    /// Index in the current palette.
+    Palette(u8),
+    /// Literal RGB value.
+    Rgb(Rgb),
+}
+impl Color {
+    /// Compare source and value.
+    pub fn eql(self, other: Self) -> bool {
+        self == other
+    }
+    /// Resolve a palette-dependent color.
+    pub fn resolve(self, palette: &Palette) -> Option<Rgb> {
+        match self {
+            Self::None => None,
+            Self::Palette(i) => Some(palette[usize::from(i)]),
+            Self::Rgb(v) => Some(v),
+        }
+    }
+}
+/// SGR boolean flags and underline kind.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Flags {
+    /// SGR bold attribute.
+    pub bold: bool,
+    /// SGR italic attribute.
+    pub italic: bool,
+    /// SGR faint attribute.
+    pub faint: bool,
+    /// SGR blink attribute.
+    pub blink: bool,
+    /// SGR inverse attribute.
+    pub inverse: bool,
+    /// SGR invisible attribute.
+    pub invisible: bool,
+    /// SGR strikethrough attribute.
+    pub strikethrough: bool,
+    /// SGR overline attribute.
+    pub overline: bool,
+    /// Underline decoration kind.
+    pub underline: Underline,
+}
+impl Default for Flags {
+    fn default() -> Self {
+        Self {
+            bold: false,
+            italic: false,
+            faint: false,
+            blink: false,
+            inverse: false,
+            invisible: false,
+            strikethrough: false,
+            overline: false,
+            underline: Underline::None,
+        }
+    }
+}
+impl Hash for Flags {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.bold.hash(state);
+        self.italic.hash(state);
+        self.faint.hash(state);
+        self.blink.hash(state);
+        self.inverse.hash(state);
+        self.invisible.hash(state);
+        self.strikethrough.hash(state);
+        self.overline.hash(state);
+        (self.underline as u8).hash(state);
+    }
+}
+/// Fully self-contained cell styling.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Style {
+    /// Foreground color.
+    pub fg_color: Color,
+    /// Background color.
+    pub bg_color: Color,
+    /// Underline color.
+    pub underline_color: Color,
+    /// SGR flags.
+    pub flags: Flags,
+}
+/// Bold foreground policy, independent of the configuration crate.
+// TODO(integration): convert ghostty-config's BoldColor at the Screen boundary.
+#[derive(Debug, Clone, Copy)]
+pub enum BoldColor {
+    /// Use bright palette colors for the first eight entries.
+    Bright,
+    /// Override the default foreground when bold.
+    Color(Rgb),
+}
+/// Inputs needed to resolve foreground colors.
+#[derive(Clone, Copy)]
+pub struct Fg<'a> {
+    /// Terminal default foreground.
+    pub default: Rgb,
+    /// Current palette.
+    pub palette: &'a Palette,
+    /// Optional bold override.
+    pub bold: Option<BoldColor>,
+}
+impl Style {
+    /// True for default styling.
+    pub fn is_default(self) -> bool {
+        self == Self::default()
+    }
+    /// Compare all style fields.
+    pub fn eql(self, other: Self) -> bool {
+        self == other
+    }
+    /// Resolve background, including background-only cells.
+    pub fn bg(self, cell: &Cell, palette: &Palette) -> Option<Rgb> {
+        match cell.content_tag() {
+            ContentTag::BgColorPalette => Some(palette[usize::from(cell.color_palette())]),
+            ContentTag::BgColorRgb => Some(cell.color_rgb()),
+            _ => self.bg_color.resolve(palette),
+        }
+    }
+    /// Resolve foreground using bold palette and default overrides.
+    pub fn fg(self, opts: Fg<'_>) -> Rgb {
+        match self.fg_color {
+            Color::None => {
+                if self.flags.bold {
+                    match opts.bold {
+                        Some(BoldColor::Color(c)) => c,
+                        _ => opts.default,
+                    }
+                } else {
+                    opts.default
+                }
+            }
+            Color::Palette(i) => {
+                opts.palette[usize::from(if self.flags.bold && opts.bold.is_some() && i < 8 {
+                    i + 8
+                } else {
+                    i
+                })]
+            }
+            Color::Rgb(c) => {
+                if self.flags.bold && c == opts.default {
+                    match opts.bold {
+                        Some(BoldColor::Color(v)) => v,
+                        _ => c,
+                    }
+                } else {
+                    c
+                }
+            }
+        }
+    }
+    /// Resolve underline color.
+    pub fn underline_color(self, palette: &Palette) -> Option<Rgb> {
+        self.underline_color.resolve(palette)
+    }
+    /// Make a background-only cell, if a background is specified.
+    pub fn bg_cell(self) -> Option<Cell> {
+        let mut c = Cell::default();
+        match self.bg_color {
+            Color::None => return None,
+            Color::Palette(i) => {
+                c.set_content_tag(ContentTag::BgColorPalette);
+                c.set_color_palette(i);
+            }
+            Color::Rgb(v) => {
+                c.set_content_tag(ContentTag::BgColorRgb);
+                c.set_color_rgb(v);
+            }
+        }
+        Some(c)
+    }
+    /// Render self-contained SGR sequences, starting with reset.
+    pub fn formatter_vt(&self) -> VtFormatter<'_> {
+        VtFormatter {
+            style: self,
+            palette: None,
+        }
+    }
+    /// Render inline CSS declarations.
+    pub fn formatter_html(&self) -> HtmlFormatter<'_> {
+        HtmlFormatter {
+            style: self,
+            palette: None,
+        }
+    }
+}
+/// VT sequence formatter.
+pub struct VtFormatter<'a> {
+    /// Style being formatted.
+    pub style: &'a Style,
+    /// Resolve palette entries to RGB when provided.
+    pub palette: Option<&'a Palette>,
+}
+impl fmt::Display for VtFormatter<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("\x1b[0m")?;
+        if self.style.flags.bold {
+            f.write_str("\x1b[1m")?;
+        }
+        if self.style.flags.faint {
+            f.write_str("\x1b[2m")?;
+        }
+        if self.style.flags.italic {
+            f.write_str("\x1b[3m")?;
+        }
+        if self.style.flags.blink {
+            f.write_str("\x1b[5m")?;
+        }
+        if self.style.flags.inverse {
+            f.write_str("\x1b[7m")?;
+        }
+        if self.style.flags.invisible {
+            f.write_str("\x1b[8m")?;
+        }
+        if self.style.flags.strikethrough {
+            f.write_str("\x1b[9m")?;
+        }
+        if self.style.flags.overline {
+            f.write_str("\x1b[53m")?;
+        }
+        f.write_str(match self.style.flags.underline {
+            Underline::None => "",
+            Underline::Single => "\x1b[4m",
+            Underline::Double => "\x1b[4:2m",
+            Underline::Curly => "\x1b[4:3m",
+            Underline::Dotted => "\x1b[4:4m",
+            Underline::Dashed => "\x1b[4:5m",
+        })?;
+        for (prefix, mut c) in [
+            (38, self.style.fg_color),
+            (48, self.style.bg_color),
+            (58, self.style.underline_color),
+        ] {
+            if let (Color::Palette(i), Some(p)) = (c, self.palette) {
+                c = Color::Rgb(p[usize::from(i)]);
+            }
+            match c {
+                Color::None => {}
+                Color::Palette(i) => write!(f, "\x1b[{prefix};5;{i}m")?,
+                Color::Rgb(v) => write!(f, "\x1b[{prefix};2;{};{};{}m", v.r, v.g, v.b)?,
+            }
+        }
+        Ok(())
+    }
+}
+/// Inline CSS formatter.
+pub struct HtmlFormatter<'a> {
+    /// Style being formatted.
+    pub style: &'a Style,
+    /// Resolve palette entries to RGB when provided.
+    pub palette: Option<&'a Palette>,
+}
+impl fmt::Display for HtmlFormatter<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        for (prop, mut c) in [
+            ("color", self.style.fg_color),
+            ("background-color", self.style.bg_color),
+            ("text-decoration-color", self.style.underline_color),
+        ] {
+            if let (Color::Palette(i), Some(p)) = (c, self.palette) {
+                c = Color::Rgb(p[usize::from(i)]);
+            }
+            match c {
+                Color::None => {}
+                Color::Palette(i) => write!(f, "{prop}: var(--vt-palette-{i});")?,
+                Color::Rgb(v) => write!(f, "{prop}: rgb({}, {}, {});", v.r, v.g, v.b)?,
+            }
+        }
+        let flags = self.style.flags;
+        if flags.underline != Underline::None
+            || flags.strikethrough
+            || flags.overline
+            || flags.blink
+        {
+            f.write_str("text-decoration-line:")?;
+            for (b, s) in [
+                (flags.underline != Underline::None, " underline"),
+                (flags.strikethrough, " line-through"),
+                (flags.overline, " overline"),
+                (flags.blink, " blink"),
+            ] {
+                if b {
+                    f.write_str(s)?;
+                }
+            }
+            f.write_str(";")?;
+        }
+        if flags.underline != Underline::None {
+            write!(
+                f,
+                "text-decoration-style: {};",
+                match flags.underline {
+                    Underline::None | Underline::Single => "solid",
+                    Underline::Double => "double",
+                    Underline::Curly => "wavy",
+                    Underline::Dotted => "dotted",
+                    Underline::Dashed => "dashed",
+                }
+            )?;
+        }
+        for (b, s) in [
+            (flags.bold, "font-weight: bold;"),
+            (flags.italic, "font-style: italic;"),
+            (flags.faint, "opacity: 0.5;"),
+            (flags.invisible, "visibility: hidden;"),
+            (flags.inverse, "filter: invert(100%);"),
+        ] {
+            if b {
+                f.write_str(s)?;
+            }
+        }
+        Ok(())
+    }
+}
+/// Page-local deduplicated style storage.
+pub type Set = crate::ref_counted_set::RefCountedSet<Style>;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_empty() {
+        let mut style = Style::default();
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_bold() {
+        let mut style = Style::default();
+        style.flags.bold = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[1m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_faint() {
+        let mut style = Style::default();
+        style.flags.faint = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[2m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_italic() {
+        let mut style = Style::default();
+        style.flags.italic = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[3m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_blink() {
+        let mut style = Style::default();
+        style.flags.blink = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[5m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_inverse() {
+        let mut style = Style::default();
+        style.flags.inverse = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[7m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_invisible() {
+        let mut style = Style::default();
+        style.flags.invisible = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[8m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_strikethrough() {
+        let mut style = Style::default();
+        style.flags.strikethrough = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[9m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_overline() {
+        let mut style = Style::default();
+        style.flags.overline = true;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[53m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_underline_single() {
+        let mut style = Style::default();
+        style.flags.underline = Underline::Single;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[4m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_underline_double() {
+        let mut style = Style::default();
+        style.flags.underline = Underline::Double;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[4:2m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_underline_curly() {
+        let mut style = Style::default();
+        style.flags.underline = Underline::Curly;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[4:3m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_underline_dotted() {
+        let mut style = Style::default();
+        style.flags.underline = Underline::Dotted;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[4:4m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_underline_dashed() {
+        let mut style = Style::default();
+        style.flags.underline = Underline::Dashed;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[4:5m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_fg_palette() {
+        let mut style = Style::default();
+        style.fg_color = Color::Palette(42);
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[38;5;42m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_fg_rgb() {
+        let mut style = Style::default();
+        style.fg_color = Color::Rgb(Rgb {
+            r: 255,
+            g: 128,
+            b: 64,
+        });
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[38;2;255;128;64m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_bg_palette() {
+        let mut style = Style::default();
+        style.bg_color = Color::Palette(7);
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[48;5;7m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_bg_rgb() {
+        let mut style = Style::default();
+        style.bg_color = Color::Rgb(Rgb {
+            r: 32,
+            g: 64,
+            b: 96,
+        });
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[48;2;32;64;96m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_underline_color_palette() {
+        let mut style = Style::default();
+        style.underline_color = Color::Palette(15);
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[58;5;15m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_underline_color_rgb() {
+        let mut style = Style::default();
+        style.underline_color = Color::Rgb(Rgb {
+            r: 200,
+            g: 100,
+            b: 50,
+        });
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[58;2;200;100;50m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_multiple_flags() {
+        let mut style = Style::default();
+        style.flags.bold = true;
+        style.flags.italic = true;
+        style.flags.underline = Underline::Single;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[1m\x1b[3m\x1b[4m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_all_flags() {
+        let mut style = Style::default();
+        style.flags.bold = true;
+        style.flags.italic = true;
+        style.flags.faint = true;
+        style.flags.blink = true;
+        style.flags.inverse = true;
+        style.flags.invisible = true;
+        style.flags.strikethrough = true;
+        style.flags.overline = true;
+        style.flags.underline = Underline::Curly;
+        let mut formatter = style.formatter_vt();
+        assert_eq!(
+            formatter.to_string(),
+            "\x1b[0m\x1b[1m\x1b[2m\x1b[3m\x1b[5m\x1b[7m\x1b[8m\x1b[9m\x1b[53m\x1b[4:3m"
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_combined_colors_and_flags() {
+        let mut style = Style::default();
+        style.flags.bold = true;
+        style.flags.italic = true;
+        style.flags.underline = Underline::Double;
+        style.fg_color = Color::Rgb(Rgb { r: 255, g: 0, b: 0 });
+        style.bg_color = Color::Palette(8);
+        style.underline_color = Color::Rgb(Rgb { r: 0, g: 255, b: 0 });
+        let mut formatter = style.formatter_vt();
+        assert_eq!(
+            formatter.to_string(),
+            "\x1b[0m\x1b[1m\x1b[3m\x1b[4:2m\x1b[38;2;255;0;0m\x1b[48;5;8m\x1b[58;2;0;255;0m"
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_all_colors_rgb() {
+        let mut style = Style::default();
+        style.fg_color = Color::Rgb(Rgb {
+            r: 10,
+            g: 20,
+            b: 30,
+        });
+        style.bg_color = Color::Rgb(Rgb {
+            r: 40,
+            g: 50,
+            b: 60,
+        });
+        style.underline_color = Color::Rgb(Rgb {
+            r: 70,
+            g: 80,
+            b: 90,
+        });
+        let mut formatter = style.formatter_vt();
+        assert_eq!(
+            formatter.to_string(),
+            "\x1b[0m\x1b[38;2;10;20;30m\x1b[48;2;40;50;60m\x1b[58;2;70;80;90m"
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_all_colors_palette() {
+        let mut style = Style::default();
+        style.fg_color = Color::Palette(1);
+        style.bg_color = Color::Palette(2);
+        style.underline_color = Color::Palette(3);
+        let mut formatter = style.formatter_vt();
+        assert_eq!(
+            formatter.to_string(),
+            "\x1b[0m\x1b[38;5;1m\x1b[48;5;2m\x1b[58;5;3m"
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_palette_with_palette_set_emits_rgb() {
+        let mut style = Style::default();
+        style.fg_color = Color::Palette(1);
+        let mut formatter = style.formatter_vt();
+        formatter.palette = Some(&ghostty_vt::color::DEFAULT);
+        assert_eq!(formatter.to_string(), "\x1b[0m\x1b[38;2;204;102;102m");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_vt_formatting_all_palette_colors_with_palette_set() {
+        let mut style = Style::default();
+        style.fg_color = Color::Palette(1);
+        style.bg_color = Color::Palette(2);
+        style.underline_color = Color::Palette(3);
+        let mut formatter = style.formatter_vt();
+        formatter.palette = Some(&ghostty_vt::color::DEFAULT);
+        assert_eq!(
+            formatter.to_string(),
+            "\x1b[0m\x1b[38;2;204;102;102m\x1b[48;2;181;189;104m\x1b[58;2;240;198;116m"
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_basic_bold() {
+        let mut style = Style::default();
+        style.flags.bold = true;
+        let mut formatter = style.formatter_html();
+        assert_eq!(formatter.to_string(), "font-weight: bold;");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_fg_color_rgb() {
+        let mut style = Style::default();
+        style.fg_color = Color::Rgb(Rgb {
+            r: 255,
+            g: 128,
+            b: 64,
+        });
+        let mut formatter = style.formatter_html();
+        assert_eq!(formatter.to_string(), "color: rgb(255, 128, 64);");
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_bg_color_palette() {
+        let mut style = Style::default();
+        style.bg_color = Color::Palette(7);
+        let mut formatter = style.formatter_html();
+        assert_eq!(
+            formatter.to_string(),
+            "background-color: var(--vt-palette-7);"
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_combined_colors_and_flags() {
+        let mut style = Style::default();
+        style.flags.bold = true;
+        style.flags.italic = true;
+        style.fg_color = Color::Rgb(Rgb { r: 255, g: 0, b: 0 });
+        style.bg_color = Color::Rgb(Rgb { r: 0, g: 0, b: 255 });
+        let mut formatter = style.formatter_html();
+        assert!(formatter.to_string().contains("color: rgb(255, 0, 0);"));
+        assert!(
+            formatter
+                .to_string()
+                .contains("background-color: rgb(0, 0, 255);")
+        );
+        assert!(formatter.to_string().contains("font-weight: bold;"));
+        assert!(formatter.to_string().contains("font-style: italic;"));
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_single_decoration_line() {
+        let mut style = Style::default();
+        style.flags.underline = Underline::Single;
+        let mut formatter = style.formatter_html();
+        assert!(
+            formatter
+                .to_string()
+                .contains("text-decoration-line: underline;")
+        );
+        assert!(
+            formatter
+                .to_string()
+                .contains("text-decoration-style: solid;")
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_multiple_decoration_lines() {
+        let mut style = Style::default();
+        style.flags.strikethrough = true;
+        style.flags.overline = true;
+        style.flags.underline = Underline::Curly;
+        let mut formatter = style.formatter_html();
+        assert!(
+            formatter
+                .to_string()
+                .contains("text-decoration-line: underline line-through overline;")
+        );
+        assert!(
+            formatter
+                .to_string()
+                .contains("text-decoration-style: wavy;")
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_palette_with_palette_set_emits_rgb() {
+        let mut style = Style::default();
+        style.bg_color = Color::Palette(7);
+        let mut formatter = style.formatter_html();
+        formatter.palette = Some(&ghostty_vt::color::DEFAULT);
+        assert_eq!(
+            formatter.to_string(),
+            "background-color: rgb(197, 200, 198);"
+        );
+    }
+    #[test]
+    #[allow(unused_mut, clippy::field_reassign_with_default)]
+    fn style_html_formatting_all_palette_colors_with_palette_set() {
+        let mut style = Style::default();
+        style.fg_color = Color::Palette(1);
+        style.bg_color = Color::Palette(2);
+        style.underline_color = Color::Palette(3);
+        let mut formatter = style.formatter_html();
+        formatter.palette = Some(&ghostty_vt::color::DEFAULT);
+        assert_eq!(
+            formatter.to_string(),
+            "color: rgb(204, 102, 102);background-color: rgb(181, 189, 104);text-decoration-color: rgb(240, 198, 116);"
+        );
+    }
+    #[test]
+    fn set_basic_usage() {
+        let mut set = Set::init(16).unwrap();
+        let a = Style {
+            flags: Flags {
+                bold: true,
+                ..Flags::default()
+            },
+            ..Style::default()
+        };
+        let b = Style {
+            flags: Flags {
+                italic: true,
+                ..Flags::default()
+            },
+            ..Style::default()
+        };
+        let id = set.add(a).unwrap();
+        assert!(id > 0);
+        assert_eq!(set.add(a).unwrap(), id);
+        assert!(set.get(id).unwrap().flags.bold);
+        let id2 = set.add(b).unwrap();
+        assert!(set.get(id2).unwrap().flags.italic);
+        assert_eq!(set.ref_count(id), 2);
+        assert_eq!(set.ref_count(id2), 1);
+        set.release(id).unwrap();
+        set.release(id2).unwrap();
+        assert_eq!(set.ref_count(id), 1);
+        assert_eq!(set.ref_count(id2), 0);
+        set.release(id).unwrap();
+        assert_eq!(set.ref_count(id), 0);
+    }
+    #[test]
+    fn set_capacities() {
+        assert!(Set::init(16384).is_ok());
+    }
+}