# PATCH /api/v2/timers/{timer}

Correct a timer

- MCP id: timers.update
- Scope: api:write:hours
- Permission: none, the record's own rules still apply
- Rate cost: 1 unit, write bucket. A write costs the same whatever `view` you ask for.
- Cache-Control: private, no-store

Partially updates a timer: absent keys are untouched, an empty body is rejected.

`started_at` is the only writable key; correcting a mis-started stopwatch is the whole purpose. The `timeable_type` / `timeable_id` pair is never accepted on a PATCH, so retargeting a timer is a DELETE followed by a POST. `user_id` is not accepted either, so a timer cannot be moved to another employee. Send `If-Match` with the `ETag` from your last read to detect a concurrent edit, which answers `412`. Treat it as best-effort only: this resource carries no concurrency token, and `updated_at` is second-precision, so two writes inside the same second are indistinguishable. This operation declares no permission of its own: you may change your own timers, and changing another employee's timer additionally requires `times::update_others`.

## Parameters
- timer (integer, path): The Timer'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
- started_at (timestamp (YYYY-MM-DDThh:mm:ssZ), optional): When the stopwatch was started. Elapsed time is this value against the client's own clock; the API publishes no elapsed counter.

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

## Response 200
- id (integer, required): Unique identifier.
- user_id (integer, required, server-assigned): Employee this timer belongs to. Always the authenticated user; a timer cannot be started for someone else.
- user (Ref or UserSummary, required): The employee this timer belongs to. Expanding it with `?include=user` additionally requires the `users::read` permission and a token scope covering the users prefix.
- timeable_type (string, required): The kind of record `timeable` points at; it says which branch of `timeable` applies.
- timeable_id (integer, required): The id of the record `timeable` points at.
- timeable (Ref or WorkItemSummary or EventSummary, required): The record being timed. Expanding it with `?include=timeable` additionally requires the read permission and token scope of the target's own prefix, per branch: `project_management` for a work item, events for a planning event.
- started_at (timestamp (YYYY-MM-DDThh:mm:ssZ), required): When the stopwatch was started. Elapsed time is this value against the client's own clock; the API publishes no elapsed counter.
- 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.
- links (TimerLinks, required)
  - self (url, required): The canonical URI of this record.

## 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/timers/1' \
  -H 'Authorization: Bearer <token>' \
  -H 'Accept: application/json' \
  -H 'Content-Type: application/json' \
  -H 'If-Match: *' \
  -d '{
    "started_at": "2026-09-01T08:45:00Z"
  }'
```