---
title: "POST /projects/{projectId}/quality-monitors/{monitorId}/backfill"
method: POST
path: "/projects/{projectId}/quality-monitors/{monitorId}/backfill"
---

# POST /projects/{projectId}/quality-monitors/{monitorId}/backfill

`POST /projects/{projectId}/quality-monitors/{monitorId}/backfill`

## Request

- Base URL: `https://api.caveman.so/api/v1`
- URL: `https://api.caveman.so/api/v1/projects/{projectId}/quality-monitors/{monitorId}/backfill`
- Auth: one of:
  - OAuth 2
    - Authorization code: `/api/v1/oauth/authorize`
    - Token URL: `/api/v1/oauth/token` scopes: `eval:write`
  - HTTP bearer
  - API key in cookie `cave_access`
  - API key in cookie `__Secure-cave_identity.session_token`

POST /api/v1/projects/{projectId}/quality-monitors/{monitorId}/backfill on the Caveman Cloud control plane. Requires the eval:write scope. Exposed to autonomous agents as the backfill action of the caveman_monitors_write tool (write access). Pause or resume existing quality monitors, and run a monitor of criteria over traces already recorded, inside its daily judge budget. Creating, replacing, and archiving monitors stays human-only because grader endpoints receive captured payloads.

## Request body

- object
  - `from` string, required
  - `to` string, required
  - `max_units` integer
  - `filter` union[]
    - union
      - object
        - `field` string, required
        - `op` 'is' | 'is_not' | 'in' | 'not_in' | 'contains' | 'not_contains' | 'starts_with' | 'regex' | 'gt' | 'gte' | 'lt' | 'lte' | 'exists' | 'not_exists'
        - `rule` string: Older name of op; matches_regex means regex. Send op or rule, never both.
        - `value` union
          - string
          - number
          - string[]
      - object
        - `all` union[], required
          - union
            - object
              - …
            - object
              - …
            - object
              - …
      - object
        - `any` union[], required
          - union
            - object
              - …
            - object
              - …
            - object
              - …
  - `criterion_id` string, uuid
  - `budget_usd` number

## Response `2XX`

Successful response. Exact status depends on synchronous or durable delivery outcome.

## Other responses

- `4XX`: Structured failure. `error.code` is stable; `error.request_id` is echoed in the x-cave-request-id header.
- `5XX`: Structured failure. `error.code` is stable; `error.request_id` is echoed in the x-cave-request-id header.

---

[API](https://skmtc.dev/caveman/apis/caveman-cloud-api.md) - [All operations](https://skmtc.dev/caveman/apis/caveman-cloud-api/llms.txt) - [OpenAPI document](https://skmtc.dev/caveman/apis/caveman-cloud-api/revisions/508312d01cfc?raw)