# PATCH /api/v2/budget-groups/{budget_group}

Update a budget group

- MCP id: budget-groups.update
- Scope: api:write:budget_groups
- Permission: budget_groups::update
- Rate cost: 1 unit, write bucket. A write costs the same whatever `view` you ask for.
- Cache-Control: private, no-store

Partially updates a budget group: absent keys are untouched and an empty body is rejected.

Send `If-Match` with the `ETag` from your last read to detect a concurrent edit, which answers `412`.

## Parameters
- budget_group (integer, path): The BudgetGroup's numeric id.
- view (string, optional): Which field set to render.
- X-Request-Id (header, optional): A correlation id of your own. It is recorded in our logs next to the server's request id but never returned: the response header always carries the server's id. A value that does not match the pattern is discarded silently, never rejected.
- If-Match (header, optional): The ETag a write is conditional on. A stale validator is 412 precondition-failed.

## Request body
- name (string ≤ 255, optional): Budget group name as shown in the UI. This is the default sort key.
- icon (string ≤ 255, optional): Icon identifier rendered beside the group, e.g. `heroicon-o-rectangle-stack`.

Unknown keys are refused with `422` validation-failed, naming the key.

## Response 200
- id (integer, required): Unique identifier.
- name (string ≤ 255, required): Budget group name as shown in the UI. This is the default sort key.
- icon (string ≤ 255, required): Icon identifier rendered beside the group, e.g. `heroicon-o-rectangle-stack`.
- created_at (timestamp (YYYY-MM-DDThh:mm:ssZ), required): Creation timestamp.
- updated_at (timestamp (YYYY-MM-DDThh:mm:ssZ), required): Last-write timestamp; use for incremental sync.
- budgets_count (integer ≥ 0, required): Number of budgets filed under this group.
- links (BudgetGroupLinks, required)
  - self (url, required): The canonical URI of this record.
  - budgets (url, required): Budgets filed under this group.

## Errors
- 403 forbidden-by-policy | insufficient-permission | insufficient-token-scope: Forbidden.
- 412 precondition-failed: Precondition failed.
- 415 unsupported-media-type: Unsupported media type.
- 422 unprocessable-relationship | validation-failed: Unprocessable content.
- 400 idempotency-key-required | invalid-cursor | invalid-query-parameter | malformed-request | unsupported-parameter: Bad request.
- 401 token-expired | unauthenticated: Unauthenticated.
- 404 endpoint-not-found | resource-not-found: Not found.
- 406 not-acceptable: Not acceptable.
- 429 rate-limit-exceeded: Too many requests.
- 500 internal-error: Server error.
- 503 tenant-unavailable: Service unavailable.

## Example
```bash
curl -X PATCH \
  'https://<your-url>/api/v2/budget-groups/1' \
  -H 'Authorization: Bearer <token>' \
  -H 'Accept: application/json' \
  -H 'Content-Type: application/json' \
  -H 'If-Match: *' \
  -d '{
    "name": "Development and QA"
  }'
```