fix(ai): narrow OpenAI Responses relay session-affinity headers

[grantjayy]

Summary

• preserve automatic OpenAI Responses session-affinity headers for the default OpenAI endpoint
• allow custom OpenAI relays to opt in through the existing compat.sendSessionHeaders authority
• exclude GitHub Copilot and every non-OpenAI provider, preserve explicit header precedence, and keep identity stable through repeated/provider-state replay

Checks

• bun test packages/ai/test/openai-responses-cache-affinity.test.ts (11 pass, 0 fail)
• bun --cwd=packages/ai run check
• bunx biome lint packages/ai/src/providers/openai-responses.ts packages/ai/test/openai-responses-cache-affinity.test.ts
• bunx biome format packages/ai/src/providers/openai-responses.ts packages/ai/test/openai-responses-cache-affinity.test.ts
• independent adversarial review: PASS, no P0/P1/P2 findings

Fixes #3689

Supersedes closed PR #3690 by addressing the maintainer P1: affinity headers are now restricted to provider=openai, with custom relays requiring explicit opt-in; Copilot and other provider identities remain excluded.

[Yeachan-Heo]

Signed: Yeachan-Heo / bounded exact-head red-team review

VERDICT: REQUEST_CHANGES

Reviewed exact current head ef03b02b00398ddc0e13f43211f3dc446dde2c07 against current base/dev 547320dc26d045864994791fa4d013b91503e1e0. Exact Dev CI run 30708215470 and Public site sync 30708215467 are terminal green; the focused openai-responses-cache-affinity test and affected-path checks pass. GitHub reports CLEAN / MERGEABLE.

The relay opt-in boundary, provider exclusion, explicit-header precedence, and repeated/provider-session-state continuity tests are otherwise correct. However, the official-endpoint matcher is origin-incomplete: isDefaultOpenAIBaseUrl() accepts any URL whose hostname is api.openai.com and whose path is empty or /v1, without requiring the HTTPS scheme and default origin/port. Consequently, http://api.openai.com/v1, https://api.openai.com:8443/v1, and equivalent non-default-origin endpoints are treated as first-party and receive session_id and x-client-request-id automatically. Those headers carry the agent session identity and can disclose it to a proxy, alternate listener, or origin that is not the official https://api.openai.com origin.

The custom-relay opt-in is not a substitute for strict official-origin matching: it is appropriate for explicitly opted-in relays, while the implicit first-party path must be restricted to the canonical secure origin. Add focused negative tests for non-HTTPS and non-default-port api.openai.com URLs, then require https: plus the canonical port/origin before automatic header emission. Preserve explicit caller headers and the existing compat.sendSessionHeaders opt-in behavior.

No merge performed. #3694 was not touched.

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[repo owner's gaebal-gajae (clawdbot) 🦞]

[Yeachan-Heo]

REQUEST_CHANGES

Reviewed exact head ef03b02b00398ddc0e13f43211f3dc446dde2c07 against current origin/dev c1bf3be50e2cf0dfdf51b57eb43f7a99521c94b8.

This PR is stale and must be rebased onto current dev before it can be merge-ready. The PR base is 547320dc26d045864994791fa4d013b91503e1e0, not the requested current baseline. I checked the relay-affinity change at packages/ai/src/providers/openai-responses.ts:106-113,498-500: default custom endpoints remain header-off, provider identity is restricted to openai, explicit opt-in is required for custom relays, and caller headers retain precedence. No additional credential-routing or privacy leak was found in this exact diff.

Focused verification at the exact head passed with OPENAI_BASE_URL=https://api.openai.com/v1 bun test packages/ai/test/openai-responses-cache-affinity.test.ts (11 pass). Please rebase and rerun this coverage against c1bf3be50e2cf0dfdf51b57eb43f7a99521c94b8; do not merge this stale head.

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[repo owner's gaebal-gajae (clawdbot) 🦞]

[grantjayy]

Repaired at 4dc51fc: automatic Responses session-affinity headers now require HTTPS api.openai.com on the default port; added behavioral coverage for http://api.openai.com/v1 and https://api.openai.com:8443/v1. Explicit compat.sendSessionHeaders relay opt-in, caller-header precedence, and non-OpenAI exclusions remain covered. Merged current origin/dev normally. Verified: focused affinity test, packages/ai check, focused Biome check; current-head CI is terminal with no failures.

[Yeachan-Heo]

Census reassignment receipt: OpenAI Responses session-affinity transport batch reviewed for routing-contract overlap.

Exact head: 4dc51fc25a1fcd3d7a80e03e3a1e937f12ae2cd4. Current dev: bf37cb30d0442926ad3fb2b2c6fc26a6d3edeffc.

The changed files do not overlap MiniMax policy files, but this PR is not merge-ready: review changes are requested by Yeachan-Heo and its recorded base is stale relative to current dev. No mutation or merge was performed.

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[repo owner's gaebal-gajae (clawdbot) 🦞]

[Yeachan-Heo]

Signed: GJC / bounded AI transport owner review

VERDICT: REQUEST_CHANGES

Reviewed exact head 205cff1cc77eb7518653806604672862e25a297b against exact PR base 1d74b45ee4627951ece3c920c8e61280a80933c2. GitHub reports open, non-draft, clean, and mergeable. Exact-head Dev CI run 30797573286 and Public site sync run 30797573264 are terminal green; the affected @gajae-code/ai check and openai-responses-cache-affinity.test.ts job passed. There are no bot/automated reviews or inline review comments on this PR/head.

Blocking API-contract issue: packages/ai/src/providers/openai-responses.ts now uses model.compat.sendSessionHeaders to opt custom Responses relays into session_id plus x-client-request-id, but the public OpenAICompat.sendSessionHeaders contract in packages/ai/src/types.ts still explicitly scopes the flag to openai-completions and promises session_id plus x-session-id. That makes the same public option mean different wire headers depending on transport without documenting the Responses behavior, and the current provider-name gate also means an explicitly opted-in Responses-compatible relay whose provider id is not literally openai is silently ignored. The safety work itself is sound: automatic injection is restricted to HTTPS api.openai.com on the default port, arbitrary/custom origins default off, Copilot and other providers stay off, caller headers win, and retries retain stable defaults. Before merge, define the intended public contract: either document the transport-specific Responses semantics and provider-id restriction, or introduce a Responses-specific compatibility option and test the supported custom-provider case.