fix: stop Codex app-server EOF handler spin

[TangHuaiZhe]

Summary

• Unregister Codex app-server stdout and stderr readability handlers when their pipes reach EOF.
• Clear both output handlers before terminating the subprocess during an explicit stop.
• Add lifecycle regression tests for EOF and explicit shutdown.

Root cause

CodexAppServerClient left each FileHandle.readabilityHandler installed after availableData returned empty data at EOF. On macOS, an EOF descriptor remains readable, so Foundation repeatedly invoked both the stdout and stderr handlers after the app-server process exited or its pipes closed. Those two hot dispatch sources could keep roughly two CPU cores busy. The existing stop() path also terminated the process without unregistering the handlers, allowing the same spin during normal disconnects.

Verification

• swift test --disable-sandbox --scratch-path /Users/tanghuaizhe/Dev/open-vibe-island/.build --filter CodexAppServer — 7 tests passed.
• swift test --disable-sandbox --scratch-path /Users/tanghuaizhe/Dev/open-vibe-island/.build — 370 tests passed.
• git diff --check — passed.

Summary by CodeRabbit

• Bug Fixes

  • Improved cleanup of application output streams when the connection ends or the client stops.
  • Prevented lingering output handlers after end-of-file, supporting more reliable shutdown behavior.

• Tests

  • Added coverage for output-handler cleanup during normal stream closure and client shutdown.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 2b343f32-864e-40a7-b2f8-7ba1a7159632

📥 Commits

Reviewing files that changed from the base of the PR and between 38972f1 and c2e9e2d.

📒 Files selected for processing (2)

• Sources/OpenIslandCore/CodexAppServer.swift
• Tests/OpenIslandCoreTests/CodexAppServerLifecycleTests.swift

Included review availability: Your plan provides up to 4 included reviews per hour; 3 remain after this review.

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📝 Walkthrough

Walkthrough

CodexAppServerClient now tracks stdout and stderr read handles, removes readability handlers at EOF, and clears handlers during stop(). Lifecycle tests cover asynchronous EOF cleanup and immediate stop cleanup.

Changes

Codex output handler lifecycle

Layer / File(s)	Summary
Output handler setup and lifecycle cleanup Sources/OpenIslandCore/CodexAppServer.swift, Tests/OpenIslandCoreTests/CodexAppServerLifecycleTests.swift	The client stores stdout and stderr read handles. start() configures both handlers through configureOutputHandlers(stdout:stderr:). Each handler clears itself at EOF. stop() clears both handlers and read handles. Tests validate EOF and stop cleanup.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to c2e9e

This localized change unregisters app-server output handlers at EOF and during shutdown, with lifecycle tests added; no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing CPU spin from the Codex app-server EOF handler.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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