# Update a pull request's branch

> Bring a pull request's branch up to date with its base: update_method merge (the default) makes a merge commit on its branch that takes in the base's new commits; rebase makes each of its commits again on top of the base's head and moves its branch there, rewriting its history.

<div class="g1t-endpoint"><span class="g1t-method" data-method="put">PUT</span><code>/repos/{owner}/{name}/pulls/{number}/update-branch</code></div>

Pushed as you, so you must be able to push to its branch: the Write role for a branch of the repository, its owner for a working copy, and push access to the fork for a branch of a fork. With expected_head_sha, refused (409) if its head is no longer that commit. Edits to the same file merge line by line; a rebase drops merge commits and commits the base already has, keeps authors, dates and messages, and moves its branch only if its head is still where it was. Returns outcome: updated (with commit, its head now, and previous), up_to_date, or needs_agent when both sides changed the same lines (with reason, detail and the paths): nothing was pushed, so merge or rebase in a clone and push.

`outcome` is `updated` (its branch moved from `previous` to `commit`), `up_to_date` (it already holds its base's head; `commit` only) or `needs_agent` (nothing was pushed: `reason` is `overlap`, `conflicting` or `unsupported`, with `detail` and the `paths` concerned). `update_method` `rebase` rewrites its branch, so pull it again before pushing more. A head that moved since `expected_head_sha` answers `409`. See [Keeping a pull request up to date](/guides/pull-requests/#keeping-it-up-to-date).

- **Authentication:** Required. Send an [access token](/reference/api/#authentication) as `Authorization: Bearer`.
- **MCP tool:** [`pull_request`](/reference/mcp/#pull_request) with `action` `update_branch`, and the same inputs
- **Scope:** An access token needs [`pull_requests:write`](/guides/authentication/#scopes).

## Path parameters

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `owner` | string | Yes | The workspace that owns the repository. |
| `name` | string | Yes | The repository's name. |
| `number` | integer | Yes | The number shown after the #. Issues and pull requests share one sequence. |

## Body parameters

Send a JSON object. Names are `snake_case`, as in responses; the `camelCase` spelling is accepted too.

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `expected_head_sha` | string | No | The head commit you saw: refused (409) if the pull request's head has moved since. |
| `update_method` | string | No | merge (the default): a merge commit on its branch takes in the base's new commits. rebase: its commits are made again on the base's head, rewriting its branch. One of `merge`, `rebase`. |

## Example request

```sh
curl -X PUT https://api.g1t.sh/repos/flagon-io/hello/pulls/14/update-branch \
  -H "Authorization: Bearer $G1T_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "expected_head_sha": "9f2c4e1a7b3d5f60812a4c6e8b0d2f4a6c8e0b13",
    "update_method": "merge"
  }'
```

## Example response

A successful request answers `200` with:

```json
{
  "outcome": "updated",
  "commit": "5b8d0f2a4c6e8a0c2e4a6c8e0a2c4e6a8c0e2a4c",
  "previous": "9f2c4e1a7b3d5f60812a4c6e8b0d2f4a6c8e0b13"
}
```

## Errors

A failed request answers with one of these statuses and a body like `{"error": {"code": "not_found", "message": "Repository not found."}}`. See [errors](/reference/api/#errors).

| Status | Code | When |
| --- | --- | --- |
| 401 | `unauthenticated` | A token is required, or the one sent is not valid. |
| 403 | `forbidden` | The token is valid but not allowed to do this, such as a member-only change, or a token without the scope it needs. |
| 404 | `not_found` | It does not exist, or you cannot see it. |
| 409 | `conflict` | The request conflicts with the current state. |
| 422 | `invalid` | The input is not valid. `message` says which field and why. |