---
title: "Create Benchmark Task Append"
method: POST
path: "/api/v1/benchmarks/{bench_id}/tasks/append"
tags: ["benchmarks"]
---

# Create Benchmark Task Append

`POST /api/v1/benchmarks/{bench_id}/tasks/append`

## Request

- Base URL: `https://api.trajectory.ai` (the document declares no server; this is the origin it was published from)
- URL: `https://api.trajectory.ai/api/v1/benchmarks/{bench_id}/tasks/append`
- Auth: none declared. Required headers: `Idempotency-Key`

Return signed artifact URLs for one append batch, staged under a prefix derived from the Idempotency-Key. Commit the returned batch_id to publish the batch's tasks.

## Path parameters

- `bench_id` string, required

## Headers

- `Idempotency-Key` string, required

## Request body

- UploadFilesRequest: One batch of files to sign PUT urls for; the owning id comes from the path or is minted.
  - `files` BenchmarkUploadFile[], required: Files to sign upload URLs for, one URL returned per declared path.
    - `path` string, required
    - `content_type` string, required
    - `size_bytes` integer, required

## Response `201`

Successful Response

- CreateBenchmarkTaskAppendResponse
  - `bench_id` string, required
  - `batch_id` string, required
  - `urls` BenchmarkUploadUrl[], required
    - `path` string, required
    - `url` string, required
    - `headers` object, required
  - `expires_at` string, date-time, required

## Changes

- **2026-10-07** `db059a2d3fb0`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/trajectory/apis/trajectory-api/changes/api/v1/benchmarks/:bench_id/tasks/append/post.md)

---

[API](https://skmtc.dev/trajectory/apis/trajectory-api.md) - [All operations](https://skmtc.dev/trajectory/apis/trajectory-api/llms.txt) - [OpenAPI document](https://skmtc.dev/trajectory/apis/trajectory-api/revisions/5b5a8ae4b4a4?raw)