Persist Cloudflare affinity cookies for MCP HTTP

[stevenlee-oai]

Codex Thread 019ef1f9-36e2-7e91-9337-504f097b9dc1

Why

Hosted plugin-service Streamable HTTP MCP traffic uses https://chatgpt.com/backend-api/ps/mcp and depends on Cloudflare's __cflb cookie for load-balancer affinity. The local and exec-server http/request path built a fresh reqwest client for each request without installing Codex's existing shared ChatGPT Cloudflare cookie store, so affinity could be lost between calls.

This is an affinity-hardening change motivated by an incident investigation. It does not establish the broader connector-cache incident RCA or claim to fix that incident in full.

What changed

• Install the existing process-local, strictly allowlisted ChatGPT Cloudflare cookie store on the reqwest client used by ReqwestHttpClient.
• Fresh clients now share allowed Cloudflare infrastructure cookies within the process that originates the local or exec-server network request.
• Keep the existing HTTPS ChatGPT-host and Cloudflare-cookie-name restrictions. This does not introduce a general cookie jar or send ChatGPT Cloudflare cookies to unrelated hosts.

Test coverage

• codex-client unit coverage verifies that the existing strict store accepts and returns __cflb for HTTPS ChatGPT URLs.
• The exec-server HTTPS integration test sends four independent http/request calls through a local TLS-intercepting proxy and verifies that:
  • Set-Cookie: __cflb=west is sent on the next plugin-service request;
  • a later Set-Cookie: __cflb=central replaces the stored value;
  • non-Cloudflare session cookies are discarded;
  • no stored ChatGPT Cloudflare cookie is sent to a non-ChatGPT host.
• just test -p codex-client — 38 passed.
• just test -p codex-exec-server --test chatgpt_cloudflare_affinity — 1 passed.
• just bazel-lock-check — passed.

Non-goals

• No persistence of ChatGPT auth, account, session, residency, or arbitrary cookies.
• No cookie persistence for third-party MCP servers.
• No special composition of caller-provided Cookie headers.
• No plugin-service, connector-cache, Habitat/habicache, routing, redirect, or API-contract changes.
• No broader incident RCA conclusions.

[stevenlee-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

Reviewed commit: 33f610dc7c

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[mzeng-openai]

Could we take a look at these two edge cases?