GitLab

Closes #1957

The OAuth path forwards client requests to chatgpt.com/backend-api/codex/responses,
where applyCodexOAuthTransform forces store=false (chatgpt.com's codex backend
rejects store=true). Reasoning items emitted under store=false are NEVER
persisted upstream, so any rs_* reference that a client carries forward in a
subsequent input[] array triggers a guaranteed upstream 404:

    Item with id 'rs_...' not found. Items are not persisted when `store` is
    set to false. Try again with `store` set to true, or remove this item
    from your input.

sub2api wraps this as 502 "Upstream request failed" and the conversation
breaks on every multi-turn /v1/responses request that uses reasoning + tools
(reproducible with gpt-5.5; gpt-5.4 happens to dodge it because the upstream
does not emit reasoning items for that model).

Affected clients include any that follow the OpenAI Responses API spec and
replay prior assistant items verbatim — in practice this hit OpenClaw and
similar agent harnesses on every turn ≥2 with tool use.

The fix: in filterCodexInput, drop input items with type == "reasoning"
entirely. The model never reads reasoning summary text from input (only
encrypted_content can carry reasoning context across turns, and chatgpt.com
under store=false does not emit it), so this is a no-op for the model itself
and a clean removal of unreachable upstream lookups.

Scope is intentionally narrow:
  * Only OAuth account requests (account.Type == AccountTypeOAuth) reach
    applyCodexOAuthTransform / filterCodexInput.
  * API-key accounts going to api.openai.com/v1/responses are unaffected
    (store=true works there, rs_* persists, multi-turn already works).
  * Anthropic / Gemini platform groups go through different transforms and
    are unaffected.
  * /v1/chat/completions is unaffected (no reasoning items).
  * item_reference items (different type) are unaffected — only type ==
    "reasoning" is dropped.

Verification:
  * Existing tests pass: go test ./internal/service/ -run Codex|Tool|OAuth
  * New regression test asserts reasoning items are dropped under both
    preserveReferences=true and preserveReferences=false.
  * End-to-end repro on gpt-5.5 multi-turn + tools: pre-patch 502, post-patch
    200. Repro on gpt-5.4 unchanged. Three-turn deep loop on gpt-5.5 passes.