---
title: "Select a milestone version's champion model"
method: POST
path: "/v1/projects/{project_id}/versions/{version_id}/champion"
tags: ["project-versions"]
---

# Select a milestone version's champion model

`POST /v1/projects/{project_id}/versions/{version_id}/champion`

## Request

- Base URL: `https://api.pioneer.ai` (the document declares no server; this is the origin it was published from)
- URL: `https://api.pioneer.ai/v1/projects/{project_id}/versions/{version_id}/champion`
- Auth: one of:
  - API key in header `X-API-Key`
  - HTTP bearer
- TypeScript: <https://skmtc.dev/pioneer/apis/brain-api/docs/v1/projects/:project_id/versions/:version_id/champion/post.ts> (a function with typed inputs; its response is checked against the schema)

Record a model as the milestone's champion and route traffic to it.

Args:
    project_id: Project the milestone belongs to.
    version_id: Milestone to record the champion on.
    request: Exactly one champion target, plus an optional reason.
    auth: Authenticated caller.

Returns:
    The updated milestone, the deployment record, and the live pointer.

## Path parameters

- `project_id` string, uuid, required
- `version_id` string, uuid, required

## Request body

- ChampionRequest: Request body for selecting a milestone's champion.
  - `training_job_id` string, nullable: Fine-tune to promote.
  - `base_model` string, nullable: Catalog base model to promote.
  - `reason` string, nullable: Why this model was chosen.

## Response `200`

Successful Response

- ChampionResponse: The milestone and routing state after a champion was confirmed.
  - `version` ProjectVersionResponse, required: A single project milestone.
    - `id` string, required
    - `project_id` string, required
    - `team_id` string, required
    - `version_number` integer, required
    - `status` 'current' | 'frozen' | 'abandoned', required: Lifecycle of a project milestone version (EDD section 9.1).
    - `objective` string, nullable, required
    - `carryover_summary` string, required
    - `champion` ChampionRef, required: What a milestone settled on, as exactly one populated target.
      - `training_job_id` string, nullable: Fine-tune chosen as champion.
      - `base_model` string, nullable: Catalog base model chosen as champion.
    - `created_by` string, required
    - `closed_by` string, nullable, required
    - `closed_at` string, date-time, nullable, required
    - `created_at` string, date-time, required
  - `deployment_id` string, required: Deployment history record written by this promotion.
  - `active_model_id` string, required: Project's live routing pointer after promotion.

## Other responses

- `422`: Validation Error

## Changes

- **2026-09-24** `0e5e86e2bae5`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/pioneer/apis/brain-api/changes/v1/projects/:project_id/versions/:version_id/champion/post.md)

---

[API](https://skmtc.dev/pioneer/apis/brain-api.md) - [All operations](https://skmtc.dev/pioneer/apis/brain-api/llms.txt) - [OpenAPI document](https://skmtc.dev/pioneer/apis/brain-api/revisions/0e5e86e2bae5?raw)