ghostty-rs/docs/rewrite/notes/review-rv16-codex.md

Codex final verification (RV16, 2026-10-12)

At 9094054, all RV15 findings are resolved: 5 behavior findings, 1 test defect, and 9 register corrections. No regression in those fixes was found.

The fresh sweep found 1 P3 functionality gap and 4 P3 deviation-register omissions; 0 P1/P2 findings. Full parity is therefore not yet established.

Severity	Verified finding	Location
P3	FreeType-only backend cannot be selected. Zig supports -Dfont-backend=freetype, disabling font discovery. Rust unconditionally enables Fontconfig on non-Apple native targets and provides no corresponding feature. Unregistered.	build.rs:52, backend.rs:93
P3 register omission	Benchmark --time extension. Rust accepts it and prints timing information; upstream’s benchmark options do not include it. Rust execution verified.	main.rs:33
P3 register omission	Benchmark --handler=full extension. Rust accepts this alternate terminal handler; upstream only implements the simplified handler. Rust execution verified.	benches.rs:107
P3 register omission	Synthetic +sgr extension. Rust generates output for this action; upstream’s action enum contains only ascii, osc, and utf8. Rust execution verified.	ghostty-synthetic.rs:37
P3 register omission	Maximum-length NOTIFY_SOCKET safety fix. With a 108-byte pathname, Zig passes its length check and writes path[108], outside its 108-byte array. Rust’s socket-address constructor safely handles that length. Register row 13 describes the abstract-address fix, but omits this separate bounds fix. Source-verified.	systemd.rs:128; Zig:116

The extensions and safety fix need documentation, not removal. No additional incorrect register claim was verified.

Verification covered:

• All 461 Zig files at inventory/interface level, with targeted implementation review; 2,801 public function declarations screened. This is a breadth sweep, not exhaustive behavioral-equivalence proof.
• 386 +show-face differential comparisons: zero differences, including CLI and file-diagnostic buffer boundaries.
• 2,587 config comparisons across 200 keys: zero differences.
• 2,000 fresh terminal differential cases: zero differences or aborts. The documented 390k campaign was not rerun.
• 2,668 distinct unit tests passed, four ignored. One fixture-writing test was blocked by read-only access; other identified fixture-writing tests were excluded.
• 138 C-header declarations have source counterparts; native export omissions correspond to Apple/WASM gates.
• Existing visual artifacts: three scenarios and 36 sprite sheets remain pixel-identical. WASM Node smoke test passed.

Inherently unavailable for native verification here: Apple Metal/IOSurface/CoreText, AppKit/UIKit/Carbon, Mach handling and Apple packaging; Windows ConPTY, native process/filesystem/exception behavior; native FreeBSD behavior. Swift was excluded.

Other execution limits: no fresh builds or captures, live portal/D-Bus integration, interactive GTK, real-browser canvas rendering, or native io_uring execution. Existing binaries were used after source-tree comparison with HEAD.

No files were modified; the worktree remains clean.