ChatGPT Codex requires streamed Responses API requests, including hidden non-chat paths such as title generation. Keep the OAuth adapter streaming upstream while preserving JSON responses for non-streaming Anthropic callers, and route ChatGPT Official titles through the OAuth Codex endpoint.
Constraint: ChatGPT Codex rejects non-streaming requests with HTTP 400
Rejected: Disable AI title generation for ChatGPT OAuth | would leave first-session metadata degraded
Confidence: high
Scope-risk: narrow
Tested: bun test src/services/openaiAuth/fetch.test.ts
Tested: bun test src/server/__tests__/title-service.test.ts
Tested: bun run check:server
Tested: git diff --check
Not-tested: Live ChatGPT OAuth account round trip after remote build
Desktop provider choice must override a separate Claude OAuth login. The OpenAI Codex fetch path is explicitly forced by the ChatGPT Official runtime marker, and the Anthropic SDK client no longer carries Claude authToken when that OpenAI transport is selected.
Constraint: Users can have both Claude OAuth and ChatGPT OAuth saved.
Rejected: Rely on isClaudeAISubscriber to choose transport | it makes Claude login override the selected ChatGPT provider.
Confidence: high
Scope-risk: moderate
Tested: bun test src/services/api/client.test.ts
Tested: bun test src/services/openaiAuth/fetch.test.ts src/server/__tests__/conversation-service.test.ts --test-name-pattern "ChatGPT Official|buildOpenAICodexFetch"
Tested: git diff --check
