---
title: "Create Log Entry"
method: POST
path: "/v1/synthesis-log"
tags: ["synthesis-log"]
---

# Create Log Entry

`POST /v1/synthesis-log`

## Request

- Base URL: `https://api.pioneer.ai` (the document declares no server; this is the origin it was published from)
- URL: `https://api.pioneer.ai/v1/synthesis-log`
- Auth: one of:
  - API key in header `X-API-Key`
  - HTTP bearer
- TypeScript: <https://skmtc.dev/pioneer/apis/brain-api/docs/v1/synthesis-log/post.ts> (a function with typed inputs; its response is checked against the schema)

Create a single synthesis log entry.

Args:
    request: Log entry data.
    auth: Authentication result.

Returns:
    The created SynthesisLogEntry.

Raises:
    HTTPException: If the entry could not be created.

## Request body

- SynthesisLogCreate: Request body for creating a single synthesis log entry.
  - `session_id` string, required: UUID grouping all entries for one synthesis session
  - `entry_type` 'prompt' | 'seed_generation' | 'seed_feedback' | 'prompt_update' | 'expansion' | 'finalization', required: Type of log entry
  - `content` object: Flexible payload keyed by entry_type
  - `dataset_id` string, nullable: Dataset ID, set when already linked
  - `project_id` string, nullable: Project ID for the session

## Response `200`

Successful Response

- SynthesisLogEntry: Single synthesis log entry returned from the API.
  - `id` string, required
  - `user_id` string, required
  - `dataset_id` string, nullable
  - `project_id` string, nullable
  - `session_id` string, required
  - `entry_type` 'prompt' | 'seed_generation' | 'seed_feedback' | 'prompt_update' | 'expansion' | 'finalization', required
  - `content` object, required
  - `created_at` string, date-time, required

## Other responses

- `422`: Validation Error

## Changes

- **2026-09-24** `0e5e86e2bae5`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/pioneer/apis/brain-api/changes/v1/synthesis-log/post.md)

---

[API](https://skmtc.dev/pioneer/apis/brain-api.md) - [All operations](https://skmtc.dev/pioneer/apis/brain-api/llms.txt) - [OpenAPI document](https://skmtc.dev/pioneer/apis/brain-api/revisions/0e5e86e2bae5?raw)