PR #24683 verification, 2026-10-28, Linux x64 Boat VM

Baseline:
$ git worktree add ../main github/main
HEAD: f6d3700ac3c506250260fcb143c5e795cbbaeb9f
$ timeout 600 vp i
exit 0
$ T3CODE_DEV_SEED=0 setsid nohup timeout 6500 vp run dev
[dev-runner] serverPort=16733 webPort=8693 baseDir=/home/user/main/.t3

Playwright from repo dependencies, /usr/bin/google-chrome:
Added /home/user/t3code as a real git project through Add project > Local folder.
Selected Codex gpt-6.1-sol, submitted a no-tools/no-edits message.
Assistant response: provider path verified 24683
Installed genuine Antigravity 1.3.0 through Settings > Providers.
Binary path /home/user/missing-antigravity:
  Not found: The custom Antigravity executable or its localharness_external sibling is missing or not executable.
Cleared Binary path:
  Installed / Sign-in not checked, version 1.3.0.
Stopped captured main dev process group 20374; main listeners exited before PR checks.

Candidate:
$ git switch --detach e1cbde784659ee7fb0f773cb712656b5e47f795f
$ timeout 600 vp i
exit 0
$ T3CODE_DEV_SEED=0 setsid nohup timeout 6500 vp run dev --home-dir /home/user/t3code/.t3
[dev-runner] serverPort=13773 webPort=5733 baseDir=/home/user/t3code/.t3

Same project, same Codex model and same message through web client:
Assistant response: provider path verified 24683
Installed genuine Antigravity 1.3.0 through Settings > Providers.
Set Binary path to actual installed agy_acp_server.par:
  Installed / Sign-in not checked, version 1.3.0.
Attempted Remove downloaded runtime and confirmed:
  This instance uses a custom executable. Clear its binary path to manage installation in T3 Code.
Clicked Sign in with the direct custom executable:
  Finish signing in in your browser. / Open browser / Cancel
$ ps -eo pid,ppid,comm
  47641 38445 agy_acp_server.
No Google account was supplied. No completed Antigravity turn claimed.
After browser disconnect, process 47641 was absent in later ps inspection.
Set missing path again:
  Not found: The custom Antigravity executable or its localharness_external sibling is missing or not executable.
Cleared Binary path:
  Installed / Sign-in not checked, version 1.3.0.
$ git status --short
(empty)
$ git rev-parse HEAD
e1cbde784659ee7fb0f773cb712656b5e47f795f

Scope limit:
The new launcherTarget immediately returns null unless platform === win32.
The original Windows bug and new .cmd/.bat behavior were NOT reproduced/verified on Linux.
No mocks, stand-in executables, fixtures, platform overrides, replay data or code edits used.
Native Windows verification remains required: actual launcher, environment setup,
helper pairing, %~dp0, managed runtime protection, ACP stdio, a real turn and shutdown.