---
title: "Changes to Chat Completions"
method: POST
path: "/v1/chat/completions"
---

# Changes to Chat Completions

`POST /v1/chat/completions`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 3 of 24 revisions.

- **2026-10-12** `43d7e06a824b`: 6 info
- **2026-09-28** `54da122a2879`: 4 warning, 2 info
- **2026-09-23** `620970c6f5f2`: 13 breaking, 11 warning, 51 info

## Changes

- **2026-10-12** `43d7e06a824b`: 6 info
  - added the new optional request property `truncate_overflow_text`
  - added the non-success response with the status `425`
  - added the optional property `x_fastino/anyOf[subschema #1: FastinoExtension]/default_schema_applied` to the response with the `200` status (media type: application/json)
  - added the optional property `x_fastino/anyOf[subschema #1: FastinoExtension]/default_schema_applied` to the response with the `200` status (media type: text/event-stream)
  - added the optional property `x_fastino/anyOf[subschema #1: FastinoExtension]/truncated` to the response with the `200` status (media type: application/json)
  - added the optional property `x_fastino/anyOf[subschema #1: FastinoExtension]/truncated` to the response with the `200` status (media type: text/event-stream)
- **2026-09-28** `54da122a2879`: 4 warning, 2 info
  - removed the request property `effort`
  - removed the request property `models`
  - removed the optional property `x_pioneer` from the response with the `200` status (media type: application/json)
  - removed the optional property `x_pioneer` from the response with the `200` status (media type: text/event-stream)
  - added the optional property `x_fastino` to the response with the `200` status (media type: application/json)
  - added the optional property `x_fastino` to the response with the `200` status (media type: text/event-stream)
- **2026-09-23** `620970c6f5f2`: 13 breaking, 11 warning, 51 info
  - the request property `messages/items/role` became required
  - the response property `created` became optional for the status `200` (media type: application/json)
  - the response property `id` became optional for the status `200` (media type: application/json)
  - the response property `object` became optional for the status `200` (media type: application/json)
  - response property `choices/items/delta/content` list-of-types was widened by adding types `null` to media type `text/event-stream` of response `200`
  - response property `choices/items/delta/reasoning_content` list-of-types was widened by adding types `null` to media type `text/event-stream` of response `200`
  - response property `choices/items/delta/tool_calls` list-of-types was widened by adding types `null` to media type `text/event-stream` of response `200`
  - response property `choices/items/finish_reason` list-of-types was widened by adding types `null` to media type `application/json` of response `200`
  - response property `choices/items/finish_reason` list-of-types was widened by adding types `null` to media type `text/event-stream` of response `200`
  - the `usage` response's property type changed from `object` to no type for status `200` (media type: text/event-stream)
  - the `usage/prompt_tokens_details` response's property type changed from `object` to no type for status `200` (media type: application/json)
  - the `x_pioneer` response's property type changed from `object` to no type for status `200` (media type: application/json)
  - the `x_pioneer` response's property type changed from `object` to no type for status `200` (media type: text/event-stream)
  - removed the optional property `detail` from the response with the `422` status
  - removed the optional property `usage/completion_tokens` from the response with the `200` status (media type: text/event-stream)
  - removed the optional property `usage/prompt_tokens` from the response with the `200` status (media type: text/event-stream)
  - removed the optional property `usage/prompt_tokens_details` from the response with the `200` status (media type: text/event-stream)
  - removed the optional property `usage/prompt_tokens_details/cache_write_tokens` from the response with the `200` status (media type: application/json)
  - removed the optional property `usage/prompt_tokens_details/cached_tokens` from the response with the `200` status (media type: application/json)
  - removed the optional property `usage/total_tokens` from the response with the `200` status (media type: text/event-stream)
  - removed the optional property `x_pioneer/inference_id` from the response with the `200` status (media type: application/json)
  - removed the optional property `x_pioneer/inference_id` from the response with the `200` status (media type: text/event-stream)
  - removed the optional property `x_pioneer/routed_model` from the response with the `200` status (media type: application/json)
  - removed the optional property `x_pioneer/routed_model` from the response with the `200` status (media type: text/event-stream)
  - api operation id `create_chat_completion` removed and replaced with `chat_completions_v1_chat_completions_post`
  - added the new optional request property `effort`
  - added the new optional request property `extra_body`
  - added the new optional request property `extra_headers`
  - added the new optional request property `include_confidence`
  - added the new optional request property `include_spans`
  - added the new optional request property `logit_bias`
  - added the new optional request property `messages/items/name`
  - added the new optional request property `messages/items/reasoning_content`
  - added the new optional request property `models`
  - added the new optional request property `system`
  - added the new optional request property `task_type`
  - added the new optional request property `threshold`
  - request property `frequency_penalty` list-of-types was widened by adding types `null` to media type `application/json`
  - request property `max_tokens` list-of-types was widened by adding types `null` to media type `application/json`
  - request property `messages/items/content` list-of-types was widened by adding types `null` to media type `application/json`
  - …35 more

---

[Operation](https://skmtc.dev/fastino-ai/apis/pioneer-inference-api/docs/v1/chat/completions/post.md) - [API](https://skmtc.dev/fastino-ai/apis/pioneer-inference-api.md) - [Page](https://skmtc.dev/fastino-ai/apis/pioneer-inference-api/changes/v1/chat/completions/post)