diff --git a/README.md b/README.md
index 48d2deb..d03306f 100644
--- a/README.md
+++ b/README.md
@@ -207,14 +207,17 @@ cargo run -p lanparty-client-win -- \
 
 The Windows client binary currently connects to the relay as `role = client`
 with a generated locally administered virtual MAC persisted in
-`lanparty-client-identity.json`, resolves the relay DNS name before TAP
-activation, completes the control-stream hello/welcome handshake, pins a host
-route for the resolved relay IP on the current pre-TAP interface, verifies that
-the relay route still uses that pinned host route after TAP activation, and then
-bridges Ethernet frames between the relay and the first TAP-Windows6 adapter
-until shutdown. `--relay` accepts a DNS name or socket address; bare hosts
-default to UDP/443. Before opening the adapter, it writes the
-generated tunnel MAC to the TAP driver's `NetworkAddress` registry setting.
+`lanparty-client-identity.json`. Before resolving or connecting to the relay,
+it selects the TAP-Windows6 adapter and marks TAP media disconnected to clear
+stale connected state from a previous crashed run. It then resolves the relay
+DNS name before TAP activation, completes the control-stream hello/welcome
+handshake, pins a host route for the resolved relay IP on the current pre-TAP
+interface, verifies that the relay route still uses that pinned host route
+after TAP activation, and then bridges Ethernet frames between the relay and
+the first TAP-Windows6 adapter until shutdown. `--relay` accepts a DNS name or
+socket address; bare hosts default to UDP/443. Before opening the adapter for
+bridging, it writes the generated tunnel MAC to the TAP driver's
+`NetworkAddress` registry setting.
 If the exact relay host route already exists, the client uses it and leaves it
 alone on exit. The startup status reports whether the relay already has a LAN
 gateway for the room.
diff --git a/TESTING.md b/TESTING.md
index b4bc4bc..b8421a3 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -118,6 +118,7 @@ one explicitly:
 Expected client output:
 
 ```text
+prepared TAP adapter ... media disconnected before relay connect
 lanparty-client-win connected as peer ...
 relay route pinned before TAP ...
 relay route verified after TAP activation ...
@@ -218,6 +219,11 @@ drop_reason=ControlPlaneEtherType
 If the client says `Waiting for LAN gateway`, check that the gateway uses the
 same room code and is connected to the same relay.
 
+If startup fails before the relay connection while preparing the TAP adapter,
+check that the terminal is elevated, TAP-Windows6 is installed, and
+`--tap-instance-id` selects the intended adapter when more than one TAP adapter
+exists.
+
 If the client says `Waiting for TAP IP`, DHCP is not making the full round trip.
 Check relay/gateway frame logs for broadcast traffic and check that the gateway
 is on wired Ethernet.
diff --git a/crates/lanparty-client-win/src/main.rs b/crates/lanparty-client-win/src/main.rs
index a89ea13..8753287 100644
--- a/crates/lanparty-client-win/src/main.rs
+++ b/crates/lanparty-client-win/src/main.rs
@@ -145,6 +145,9 @@ async fn main() -> Result<()> {
         return Ok(());
     }
 
+    #[cfg(windows)]
+    prepare_tap_before_relay_connect(args.tap_instance_id.as_deref())?;
+
     let config = args.into_config()?;
     println!(
         "lanparty-client-win connecting virtual MAC {} to relay {} room {}",
@@ -197,6 +200,21 @@ fn print_available_tap_adapters() -> Result<()> {
     Ok(())
 }
 
+#[cfg(windows)]
+fn prepare_tap_before_relay_connect(tap_instance_id: Option<&str>) -> Result<()> {
+    let adapters = lanparty_client_tap::available_adapters()
+        .context("failed to list TAP-Windows6 adapters before relay connect")?;
+    let info = select_tap_adapter(adapters, tap_instance_id)?;
+    let device_path = info.device_path();
+    let tap = TapAdapter::open(info)?;
+    tap.set_media_connected(false)
+        .with_context(|| format!("failed to mark TAP media disconnected for {device_path}"))?;
+
+    println!("prepared TAP adapter {device_path}: media disconnected before relay connect");
+
+    Ok(())
+}
+
 #[cfg(windows)]
 async fn run_client(
     session: &ClientSession,