fix(omo-codex): fail on unreadable config.toml instead of overwriting it (fixes #5751)

[MoerAI]

Summary

The omo-codex installer could overwrite an existing config.toml when the file exists but cannot be read. updateCodexConfig() now reads the config directly and only treats a genuinely-absent file (ENOENT) as empty; any other read error is re-thrown before a single byte is written.

Fixes #5751.

Root Cause

updateCodexConfig() probed for an existing config with a local exists() helper:

let config = ""
if (await exists(input.configPath)) config = await readFile(input.configPath, "utf8")
// ...
async function exists(path: string): Promise<boolean> {
  try { await readFile(path, "utf8"); return true }
  catch (error) { if (error instanceof Error) return false; return false }
}

exists() swallowed every readFile() error and returned false. A present-but-unreadable config.toml (EACCES/EPERM, or any non-ENOENT read failure) was therefore treated as absent, so the function started from an empty config and writeFileAtomic() replaced the user's file, dropping its contents.

Changes

File	Change
packages/omo-codex/src/install/codex-config-toml.ts	Read the config directly; catch only ENOENT (use empty config), re-throw all other read errors before any write. Remove the now-unused exists() helper. Reuses the existing isNodeErrorWithCode guard from codex-cache-fs.
packages/omo-codex/src/install/codex-config-toml.test.ts	Two regression tests: a cross-platform case (an unreadable path surfaces the read error instead of overwriting) and a POSIX chmod 0o200 case asserting the original file is preserved.

Net source change: +6 / -9 (one import, the read guard, minus the dead helper).

Reproduction (before fix)

The new test against the unmodified code shows the installer reaches writeFileAtomic and attempts to overwrite the existing path:

).rejects.toThrow("EISDIR")
error: expect(received).toThrow(expected)
Expected substring: "EISDIR"
Received message: "EPERM: operation not permitted, rename
'...\.tmp-config.toml-7968-...' -> '...\config.toml'"
(fail) codex-config-toml > ...surfaces the read error instead of overwriting from an empty config

chmod cannot make a file unreadable on Windows, so the unreadable case is exercised cross-platform via a directory config.toml (so readFile throws EISDIR), plus a POSIX chmod 0o200 test that is skipped on Windows.

Verification (after fix)

(pass) codex-config-toml > ...surfaces the read error instead of overwriting from an empty config
(skip) codex-config-toml > ...rejects and preserves the original file   # POSIX-only chmod case
 22 pass
 1 skip
 0 fail
Ran 23 tests across 1 file.

Test

• Regression: packages/omo-codex/src/install/codex-config-toml.test.ts (2 new cases) - 22 pass / 1 skip (POSIX-only chmod case) / 0 fail
• Typecheck: tsgo --noEmit -p packages/omo-codex/tsconfig.json - clean (exit 0)

Fixes #5751

---

Summary by cubic

Prevents the omo-codex installer from overwriting an existing config.toml when the file exists but can’t be read. updateCodexConfig() now treats only ENOENT as “missing” and fails fast on other read errors. Fixes #5751.

• Bug Fixes
  • Read the config directly; catch only ENOENT, re-throw all other read errors before any write.
  • Removed the exists() probe that swallowed read errors and caused unintended overwrites.
  • Added regression tests for unreadable paths (cross‑platform) and POSIX chmod to ensure the original file is preserved.

^{Written for commit e4b783c. Summary will update on new commits.}

[MoerAI]

I have read the CLA Document and I hereby sign the CLA

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Regenerate the Codex installer bundle

This source-only fix is bypassed by the stable installer entrypoint in a fresh checkout: packages/omo-codex/scripts/install-local.mjs imports scripts/install-dist/install-local.mjs whenever that checked-in bundle exists, and the bundle still contains the removed if (await exists(input.configPath)) config = await readFile(...) path around its updateCodexConfig(). As a result, node packages/omo-codex/scripts/install-local.mjs install can still treat non-ENOENT read failures as an absent config and overwrite user data; run bun run build:codex-install and commit the regenerated bundle so the fix reaches the script consumers.

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