Requests are sent to incorrect endpoint when using base URL override

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Hey, thanks for the detailed breakdown, this is fully enough. You don’t need to send the Request ID separately.

Confirming your takeaway from post #32. The main issue with the payload shape input to messages is fixed on our side. Your request now correctly goes to /v1/chat/completions with the messages field.

There’s still a separate bug with custom tool serialization. ApplyPatch is being sent in the Responses API shape:

{ "type": "custom", "name": "ApplyPatch", "description": "...", "format": {...} }

but Chat Completions expects the custom wrapper:

{ "type": "custom", "custom": { "name": "...", "description": "...", "format": { "type": "grammar", "grammar": {...} } } }

That’s why OpenAI responds with missing_required_parameter: 'tools[7].custom'.

It’s the same family as function-tools serialization with BYOK + Override OpenAI Base URL, where you see tools[i]: missing field 'function'. The tools array isn’t being converted into the Chat Completions shape.

If I get anything concrete on this, I’ll reply in the thread.