---
title: "Write Run Blob"
method: POST
path: "/api/v1/runs/{id}/blobs"
tags: ["Run Internals"]
---

# Write Run Blob

`POST /api/v1/runs/{id}/blobs`

Writes an opaque binary blob and returns its content-addressed blob hash.

## Path parameters

- `id` string, required

## Response `200`

Blob written

- WriteBlobResponse — Content-addressed hash of a stored blob.
  - `hash` string, required — Content-addressed SHA-256 hash of a stored blob. Hex input is case-insensitive; Fabro emits the canonical lowercase form.

## Other responses

- `404` — Run not found

## Changes

- **2026-08-17** `64a24779d395` — 1 info
  - the `hash` response's property pattern was changed from `^[0-9a-f]{64}$` to `^[0-9A-Fa-f]{64}$` for the status `200`
- **2026-08-16** `0877d3997512` — 1 info
  - the `hash` response's property pattern `^[0-9a-f]{64}$` was added for the status `200`
- **2026-08-14** `6d9c2ee8b495` — 1 info
  - the `hash` response's property pattern `^[0-9A-Fa-f]{64}$` was added for the status `200`
- **2026-08-14** `36bcb57239f6` — 1 breaking, 1 info
  - removed the required property `id` from the response with the `200` status
  - added the required property `hash` to the response with the `200` status

[Change history](https://skmtc.dev/fabro-sh/apis/fabro-run-api/changes/api/v1/runs/:id/blobs/post.md)

---

[API](https://skmtc.dev/fabro-sh/apis/fabro-run-api.md) · [All operations](https://skmtc.dev/fabro-sh/apis/fabro-run-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/fabro-sh/fabro-run-api/revisions/7bdeefd151cd/schema)