[nwparker]

	Files	Added	Deleted	Net
Test	2	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​26	$\color{#cf222e}{\Huge{\mathbf{−}}}$​24	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​2
Prod	4	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​11	$\color{#cf222e}{\Huge{\mathbf{−}}}$​23	$\color{#cf222e}{\Huge{\mathbf{−}}}$​12

ELI5

On Windows, when Grok, Devin, or Cursor runs Orca's Claude hook (these agents import Claude's hooks), Orca is supposed to skip quietly. Instead of returning, the skip handed stdin to more.com and waited for stdin to close. If the caller kept stdin open, the hook just hung: it held the agent's tool call until the hook timeout and left a child process holding the agent's stdout pipe. These skips now return right away without reading stdin, which is already how Orca handles the "not in an Orca pane" guards on Windows.

Root cause

• .cmd hooks: the Devin skip (src/main/claude/hook-script.ts), the Grok replay guard (grok-replay-guard.ts, used by the Claude and Cursor hooks), and the Cursor replay guard (cursor-replay-guard.ts, added after fix(hooks): exit Windows Devin/Grok skip without draining stdin #24909 was opened) all goto :orca_agent_hook_drain_stdin, which runs "%SystemRoot%\System32\more.com" >nul. That's a read-to-EOF with no bound.
• orca-agent-hook.exe is now the primary Windows Claude hook (perf(claude): run the Windows Claude hook as a signed native claude-hook.exe #27719, exec form fix(claude): run the native Windows hook exe for spaced profile paths #33364). It has the same behavior: drain_vars: ["GROK_HOOK_EVENT", "DEVIN_PROJECT_DIR"] → io::copy(stdin, sink).
• POSIX isn't affected. It captures stdin through the bounded first-byte/idle reader ([Bug]: Codex managed hook leaves persistent cmd.exe windows outside Orca on Windows #11549).

What changed

• Rebased @inforanger's fix(hooks): exit Windows Devin/Grok skip without draining stdin #24909 onto current main (their commit is kept). The Devin and Grok .cmd skips now exit /b 0.
• The Cursor replay guard gets the same treatment.
• native/windows-agent-hook/src/main.rs: Grok/Devin move from drain_vars to exit_vars, and the now-unused drain branch is removed.
• Tests:
  • The Windows live test (managed-hook-stdin-lifecycle.test.ts) now runs the in-pane Devin/Grok/Cursor skips with stdin held open.
  • The structural check now rejects any goto into the drain from managed scripts. It was ORCA_*-only before.
  • The native exe host test now runs the Grok/Devin skip with stdin abandoned.

Verification

Reproduced on current main with a real Windows 11 host (win-lowspec). I generated claude-hook-impl.cmd with this repo's getManagedScript on Windows and ran it through cmd.exe /d /c with Orca pane env plus each vendor's variable. The writer sent a 256 KB payload:

skip	stdin	main	this PR
Devin	held open	still running after 6 s	exit 0 in ~55 ms
Grok	held open	still running after 6 s	exit 0 in ~52 ms
Cursor	held open	still running after 6 s	exit 0 in ~59 ms
any	closed	exit 0, ~80 ms	exit 0, ~55 ms (writer sees EOF)

Native exe logic, from the same Rust source built for the host with the payload written and stdin left open: main was still running after 3 s for both GROK_HOOK_EVENT and DEVIN_PROJECT_DIR, and this PR exits 0 in 2–196 ms. cargo check is clean. The Windows-only exe/host tests run in Windows CI, because the exe build needs a Windows host.

I also ran the Windows-only vitest suites in a clean clone of this branch on win-lowspec. With this PR, managed-hook-stdin-lifecycle.test.ts and grok-replay-guard.test.ts pass, including the new held-open-stdin skip leg. With main's three source files restored, the new leg fails with hook did not finish with stdin abandond: cmd.exe /d /c ...\claude-hook-impl.cmd. The one remaining failure on that host is the orca-agent-hook.exe build, because it has no Rust toolchain. It fails the same way on main.

Also ran pnpm tc, check:code-quality:changed, and the agent-hooks / claude / cursor / grok / devin suites (296 files) on macOS.

Risk

• The writer can see a broken pipe on these skips. A caller that writes a large payload after the hook has exited gets EPIPE/EOF, the same as Orca's missing-context guards today. I checked the callers against upstream:
  • Grok ignores the stdin write result (grok-build crates/codegen/xai-grok-hooks/src/runner/command.rs:259-266, let _ = stdin.write_all(..)) and kills the hook group on timeout.
  • Cursor feeds hooks through a shell heredoc (cursor-agent 2026.06.02 3880.index.js executeCommandScript: ${command} <<'CURSOR_HOOK_EOF').
  • Devin is closed source, so I couldn't confirm how it treats a hook stdin write failure. The hook still prints {} first and exits 0.
• The unreachable :orca_agent_hook_drain_stdin epilogue is left in the Claude script. It's shared with other scripts and with the statusline and missing-script launchers.

Credit

This builds on #24909 by @inforanger: their commit is preserved, and the follow-up commit credits them as co-author. It supersedes #24909, which conflicts with current main and misses the Cursor guard and the native exe.

Fixes #24907

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Commits

Reviewing files that changed from the base of the PR and between 1e221ce and 4a69485.

Files selected for processing: 6

• native/windows-agent-hook/src/main.rs
• src/main/agent-hooks/cursor-replay-guard.ts
• src/main/agent-hooks/grok-replay-guard.ts
• src/main/agent-hooks/managed-hook-stdin-lifecycle.test.ts
• src/main/agent-hooks/windows-native-hook-exe-hosts.test.ts
• src/main/claude/hook-script.ts

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Walkthrough

Windows native and managed hook skip paths now exit without draining stdin. The native hook reads stdin only after its exit checks pass. Tests cover skip paths with stdin left unwritten and verify successful exits.

Priority: Normal

Severity of issue fixed: Medium

Merge Risk: Minimal · up to 4a694

The Windows replay-hook skips can exit without waiting for abandoned stdin. No merge-blocking issue was identified.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 14.29% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 6 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title "fix(hooks): exit Windows vendor-replay hook skips without draining stdin" matches the main change. The PR makes Windows Devin, Grok, and Cursor replay-hook skips (and the native orca-agent-…
Description check		The description follows the repository template. It has ELI5, What Changed (with root cause and mechanism), Why (explains the drain behavior and the chosen approach over alternatives), Linked Issue (F…
Linked Issues check		Issue #24907 requires Windows skip paths to avoid an EOF-dependent stdin drain or to use a bounded reader. The PR changes the Devin and Grok managed-script skips, the Cursor replay skip, and the nativ…
Out of Scope Changes check		The changes stay within issue #24907. Production changes remove stdin ownership from vendor-replay skip paths. Test changes verify the no-drain structure and the required early exit behavior. The Curs…

Full details: Title check

Explanation

The title "fix(hooks): exit Windows vendor-replay hook skips without draining stdin" matches the main change. The PR makes Windows Devin, Grok, and Cursor replay-hook skips (and the native orca-agent-hook.exe Grok/Devin path) exit without reading stdin. It uses a conventional commit prefix and is specific. It does not name every file, which is expected.

Full details: Description check

Explanation

The description follows the repository template. It has ELI5, What Changed (with root cause and mechanism), Why (explains the drain behavior and the chosen approach over alternatives), Linked Issue (Fixes #24907), Visual Proof (behavior change with a detailed before/after table of measured timings instead of screenshots), Testing (Windows 11 and macOS runs listed with specifics), a Risk section, Credit, and a checklist. Gaps: the AI Disclosure section is blank, the Review and Agent skill upstream boundary checkboxes are not ticked or addressed, the Notes cross-platform/SSH/backwards-compatibility sweep is not explicitly confirmed, and the template's checklist items are not marked. The 'Visual Proof' section is a timing table rather than the requested BEFORE/AFTER attachments, which is acceptable for a non-UI hook change but should be stated as N/A with reason or supported with the table as is.

Resolution

Optionally fill in the AI Disclosure section (or mark it as not applicable for internal contributors), tick or address the Agent skill upstream boundary checkbox, and confirm the Notes checks for Security, cross-platform, SSH, and backwards compatibility. Mark the Visual Proof section as N/A with the reason, or keep the timing table and label it as the behavior evidence.

Full details: Linked Issues check

Explanation

Issue #24907 requires Windows skip paths to avoid an EOF-dependent stdin drain or to use a bounded reader. The PR changes the Devin and Grok managed-script skips, the Cursor replay skip, and the native Claude hook executable to exit before reading stdin. The tests cover held-open or abandoned stdin for the managed scripts and native executable. The shared drain remains only for other callers, which does not conflict with the issue requirement.

Full details: Out of Scope Changes check

Explanation

The changes stay within issue #24907. Production changes remove stdin ownership from vendor-replay skip paths. Test changes verify the no-drain structure and the required early exit behavior. The Cursor and native executable changes directly address the same Windows hang mechanism. No unrelated production behavior is introduced.

Finishing Touches: 💡 1

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