# Requests are sent to incorrect endpoint when using base URL override

**URL:** <https://forum.cursor.com/t/requests-are-sent-to-incorrect-endpoint-when-using-base-url-override/144894>\
**Category:** Bug Reports\
**Created:** [December 1, 2025, 2:10pm UTC](https://forum.cursor.com/t/requests-are-sent-to-incorrect-endpoint-when-using-base-url-override/144894 "2025-12-01T14:10:59Z")\
**Posts on this page:** 1\
**Showing post:** 36

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**Author:** ![deanrie](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/deanrie/32/1263_2.png) [@deanrie](https://forum.cursor.com/u/deanrie)\
**Post date:** [June 29, 2026, 2:01pm UTC](https://forum.cursor.com/t/requests-are-sent-to-incorrect-endpoint-when-using-base-url-override/144894/36 "2026-06-29T14:01:28Z")

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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:

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

```

but Chat Completions expects the `custom` wrapper:

```json
{ "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.

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