Auto-route /chat/completions to /responses for unsupported chat completion features#233
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Erin McNulty (erin2722) merged 3 commits intoMay 11, 2026
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Erin McNulty (erin2722)
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Alex Z (CLowbrow) and
Ken Jiang (knjiang)
| Some(openai::OutputItemType::Message) => { | ||
| // Extract text content from message output items | ||
| // Extract text content from message output items. | ||
| // `phase` is a message-level field (not content-level); it is stored in |
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This was a bit of a seperate change that I found because of the additional payload tests. We were stripping the phase parameter from messages when going through the universal format, and while this doesn't cause an error, it can negatively impact the chat responses-- https://developers.openai.com/api/docs/guides/reasoning#phase-parameter
These changes stick it in provider_options for the universal round trip
Ken Jiang (knjiang)
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May 11, 2026
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This fix addresses an issue where the
/chat/completionsendpoint doesn't support reasoning with tool calls, as part of OpenAI's push to get every to migrate to the/responsesendpoint. Lingua was passing these requests straight through to the configured/chat/completionsendpoint and we were encountering a failure because of this.Like we were chatting about in standup last week, there are 2 potential resolutions to this:
/responsesbased on additional specific format detection logic in the router.I've gone with the second option here-- from my reading, I'd expect us to run into this flavor of problem again as openai pushes everyone to responses. Its not too janky :), and I think will come in handy in the future too.