---
title: "Make the experiment group the new workstream default"
method: POST
path: "/api/v1/experiments/{experiment_id}/apply-winner"
tags: ["experiments"]
---

# Make the experiment group the new workstream default

`POST /api/v1/experiments/{experiment_id}/apply-winner`

## Request

- Base URL: `https://api.outrival.com` (the document declares no server; this is the origin it was published from)
- URL: `https://api.outrival.com/api/v1/experiments/{experiment_id}/apply-winner`
- Auth: HTTP bearer

Fold: the variant becomes what everyone gets. Then the experiment ends.

Writes the winning configuration onto the campaign row (so today's call
path serves it) and concludes with reason ``applied_winner``.

## Path parameters

- `experiment_id` string, required

## Request body

- OptionalReasonRequest: A note stored with apply-winner. Outcome is implied.
  - `reason` string, nullable: Recorded with the conclusion; free text

## Response `200`

Successful Response

- object

## Other responses

- `400`: Invalid experiment ID format
- `403`: User may not edit this experiment's campaign
- `404`: No such experiment
- `409`: The experiment is not running
- `422`: There is no experiment group with pins to apply

## Changes

- **2026-09-03** `219a10b80707`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/outrival/apis/fastapi/changes/api/v1/experiments/:experiment_id/apply-winner/post.md)

---

[API](https://skmtc.dev/outrival/apis/fastapi.md) - [All operations](https://skmtc.dev/outrival/apis/fastapi/llms.txt) - [OpenAPI document](https://skmtc.dev/outrival/apis/fastapi/revisions/f27d90300b5e?raw)