Share MCP OAuth locks across Codex shadow homes

[juliusmarminge]

Summary

• Add mcp-oauth-locks to the shared Codex home directories.
• Replace Codex-created local MCP OAuth lock directories with symlinks to the shared directory.
• Add coverage for shared lock linking and replacement behavior.

Testing

• Added CodexHomeLayout tests for MCP OAuth lock directory sharing and replacement.
• Not run: full lint and test suite.

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Note

Medium Risk
Touches MCP OAuth lock paths on disk during shadow-home materialization; scope is limited to Codex layout and one replaceable directory, but incorrect removal/linking could affect concurrent OAuth lock behavior.

Overview
Codex auth-overlay shadow homes now treat mcp-oauth-locks like other shared state: the directory is created under the shared home and linked from the shadow home so MCP OAuth file locks stay consistent across instances.

ensureSymlink no longer fails when Codex has already created a real mcp-oauth-locks folder in the shadow home. For that entry only, materialization recursively removes the local directory and replaces it with a symlink to the shared lock path; other non-symlink conflicts still raise CodexShadowHomeEntryConflictError.

Tests assert the symlink in the main materialization case and add a dedicated case for replacing a Codex-created local lock directory.

^{Reviewed by Cursor Bugbot for commit 11eca59. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Share MCP OAuth locks across Codex shadow homes via symlink

• Adds mcp-oauth-locks to KNOWN_SHARED_DIRECTORIES in CodexHomeLayout.ts so it is symlinked to the shared home when materializing a shadow home.
• Introduces REPLACEABLE_SHARED_RUNTIME_DIRECTORIES to handle the case where a shadow home already has a local mcp-oauth-locks directory: instead of raising a conflict error, the existing directory is removed and replaced with a symlink to the shared path.
• Behavioral Change: a pre-existing non-symlink mcp-oauth-locks in a shadow home is now silently deleted and replaced; previously this would have thrown a CodexShadowHomeEntryConflictError.

^{Macroscope summarized 11eca59.}

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✨ Finishing Touches

🧪 Generate unit tests (beta)

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR changes runtime behavior by automatically removing local 'mcp-oauth-locks' directories and replacing them with symlinks to shared directories. The deletion behavior warrants human review to verify the intended edge cases are handled correctly.

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