🤖 fix: strip unsupported truncation from Codex OAuth requests#3153
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🤖 fix: strip unsupported truncation from Codex OAuth requests#3153ammar-agent wants to merge 1 commit intomainfrom
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The ChatGPT Codex Responses endpoint rejects the OpenAI `truncation` parameter, so Codex OAuth requests must strip it even when the public Responses API would accept it. Restore that behavior in the request normalizer and lock it in with regression coverage. --- _Generated with `mux` • Model: `openai:gpt-5.4` • Thinking: `xhigh` • Cost: `$1.79`_ <!-- mux-attribution: model=openai:gpt-5.4 thinking=xhigh costs=1.79 -->
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Apr 9, 2026
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Summary
Strip the unsupported
truncationfield from Codex OAuth Responses requests before rerouting them to ChatGPT's Codex backend.Background
A recent regression in Mike's
2662aedd8change (🤖 fix: align GitHub Copilot model routing (#3104)) started preserving OpenAI'struncationfield insidenormalizeCodexResponsesBody(). A user then hit the backend error:{ "detail": "Unsupported parameter: truncation" }The public OpenAI Responses API accepts
truncation, but the ChatGPT Codex endpoint used by OAuth (https://chatgpt.com/backend-api/codex/responses) does not.Implementation
truncationfrom the Codex-compatible allowlistjson.truncationduring Codex request normalizationtruncationValidation
bun test src/node/services/providerModelFactory.test.tsbun test src/node/services/codexOauthService.test.tsmake static-checkRisks
Low. The change only affects the Codex OAuth request-normalization path and restores the pre-regression behavior for a field that the target endpoint rejects.
Generated with
mux• Model:openai:gpt-5.4• Thinking:xhigh• Cost:$1.79