Keep OAuth callback sessions on ephemeral ports

[TheGreatAxios]

Summary

• OAuth callback sessions bind to an OS-assigned loopback port
• Callback bind failures surface an actionable error instead of hanging authorization
• Closing the callback server rejects pending authorization waits during disposal

Verification

• bun run check passes (6,286 tests, 0 failures)
• Callback-server tests pass (7 tests, 0 failures)

Fixes CL-7529

[linear-code]

CL-7529

[TheGreatAxios]

Primary · Comment

Ready for human review. The branch stays within the OAuth callback-server boundary and passes the repository pre-PR gate.

No residual findings.

Checks: bun run check (exit 0; 6,286 pass, 0 fail); reviewer-of-record log/stat/message audits; callback-server tests (exit 0).

[TheGreatAxios]

Critic · Comment

The full origin/main...HEAD behavioral review is clean. Callback sessions use OS-assigned loopback ports, bind failures are actionable, and close rejects pending waits.

No findings.

[TheGreatAxios]

Critic · Comment

close() rejects pending waitForCode; bind failures get a wrapped error. Listen port is still 0, as on main.

Findings

• src/mcp/callback-server.ts:80 — every listen error is rewritten as an unexpected ephemeral-port failure that tells the user to retry. EACCES / EADDRNOTAVAIL are not retryable, and the wrapper drops cause and code. Sibling src/auth/oauth/callback-server.ts:96 special-cases EADDRINUSE and rethrows other errors as-is.
• src/mcp/callback-server.test.ts:76 — the new port test only checks one server's hostname and port > 0. Change listen(0, …) to a fixed free port and it still passes, so it does not lock the cross-session invariant the ticket names.

Notes

• Port 0 was already the listen port on main. The hang this branch actually fixes is waitForCode surviving close().

[TheGreatAxios]

Verdict: approve (cannot GitHub-approve own PR).

CL-7529 holds at 2e47f45a. Callback server listens on port 0 only; bind failures keep the OS message with no retry lie; close() rejects pending and post-close waitForCode so disposal cannot hang interactive auth.

No blocking or should-fix findings. Keep the concurrent-port, close-rejects-waiter, and bind-failure tests.

[TheGreatAxios]

Verdict: approve (GitHub cannot approve own PR).

CL-7529 holds at 2e47f45a. Callback server listens on port 0 only; bind failures keep the OS message with no retry lie; close() rejects pending and post-close waitForCode so disposal cannot hang interactive auth.

No blocking or should-fix findings. Keep the concurrent-port, close-rejects-waiter, and bind-failure tests.

[TheGreatAxios]

Verdict: approve (GitHub cannot approve own PR).

CL-7529 holds at 2e47f45a. Callback server listens on port 0 only; bind failures keep the OS message; close() rejects pending and post-close waitForCode so disposal cannot hang interactive auth.

CI is green (prettier, eslint, typecheck, build-and-test).

[TheGreatAxios]

Verdict: approve (GitHub cannot approve own PR).

CL-7529 holds at 2e47f45. Callback server listens on port 0 only; bind failures keep the OS message; close() rejects pending and post-close waitForCode so disposal cannot hang interactive auth.

CI is green (prettier, eslint, typecheck, build-and-test).