[rmcp-client] Serialize MCP OAuth login and logout

[stevenlee-oai]

Codex Thread 019edd6d-6f14-74e2-853c-345d1803d4a6

Important

This PR belongs to the superseded MCP OAuth stack. Please review and merge the replacement stack beginning with openai/codex#30292. This PR remains available only as historical/reference context.

Replacement review order:

1. openai/codex#30292 — shared File/Secrets store locking
2. openai/codex#30293 — authoritative serialized refresh
3. openai/codex#30294 — Codex-owned transport refresh and one-shot 401 recovery
4. openai/codex#30295 — login/logout transaction serialization
5. openai/codex#30296 — diagnostic-only Auto store drift reporting

This is part 2 of a five-PR stack that prevents concurrent MCP OAuth refreshes from replaying a rotating refresh token or overwriting newer credentials.

Review and merge as one stack. The five PRs are an atomic merge unit split only for reviewability. Each tip compiles and is testable, but implementation and regression tests are intentionally not duplicated across intermediate layers.

Review order

1. openai/codex#29017 — refresh ownership, authoritative reread, and lifecycle-local store pinning
2. openai/codex#29019 — serialize login and logout with refresh (this PR)
3. openai/codex#29021 — lock aggregate stores and observe Auto resolution drift
4. openai/codex#29018 — route all OAuth recovery through Codex
5. openai/codex#30089 — consolidated concurrency and transport regression tests

Why

Login, logout, and refresh all mutate the same credential identity. If login or logout bypasses the refresh transaction lock, an older in-flight refresh can overwrite a completed login or recreate credentials after logout.

What changes

• Make OAuth callback persistence acquire the same per-credential transaction lock as refresh.
• Make CLI logout acquire that lock before deleting credentials.
• Preserve the lock order: per-credential transaction lock before any aggregate store lock.

Decisions encoded by this stack

• Login, logout, and refresh serialize on the same compute_store_key(server_name, url) identity.
• A completed login or logout is authoritative over stale in-memory refresh state.
• Lock acquisition remains bounded.
• Auto remains lifecycle-local; part 3 records only non-authoritative diagnostic history and does not add selector metadata or migration.
• openai/codex#28647 and its branch remain untouched.

Review focus

Review credential identity consistency and lock ordering across callback persistence, refresh, and CLI logout. Part 3 separately protects aggregate File/Secrets maps after a transaction reaches a store.

Non-goals

• Changing the OAuth callback or CLI contract.
• Deleting residue from the non-selected Auto store.

Validation

• just test -p codex-rmcp-client: 90 passed, 2 skipped.
• just test -p codex-cli: 292 passed.
• The refresh-vs-login and refresh-vs-logout race cases are consolidated in part 5.

[chatgpt-codex-connector]

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