Implementation:Langfuse Langfuse API Comments Schema

Knowledge Sources	Langfuse Langfuse API Reference
Domains	API, Comments
Last Updated	2026-02-14 00:00 GMT

Overview

Fern API definition for the comments API, enabling collaborative discussion on traces, observations, sessions, and prompts within Langfuse projects.

Description

This file defines the public API contract for managing comments under /api/public. Comments support markdown content (up to 5000 characters) and can be attached to different object types. The file contains three endpoints:

• POST /api/public/comments -- Create a new comment attached to a trace, observation, session, or prompt
• GET /api/public/comments -- List all comments with pagination and filtering by object type, object ID, or author
• GET /api/public/comments/{commentId} -- Get a single comment by its ID

The response types reference commons.Comment for the comment data model.

Usage

Developers reference this definition when:

• Building comment functionality into integrations or automation
• Generating SDK types for the comments API
• Adding new filterable fields or comment object types
• Understanding the comment attachment model across different Langfuse entities

Code Reference

Source Location

• Repository: Langfuse
• File: fern/apis/server/definition/comments.yml
• Lines: 1-73

Signature

service:
  auth: true
  base-path: /api/public
  endpoints:
    create:
      docs: Create a comment. Comments may be attached to different object types
            (trace, observation, session, prompt).
      method: POST
      path: /comments
      request: CreateCommentRequest
      response: CreateCommentResponse

    get:
      docs: Get all comments
      method: GET
      path: /comments
      request:
        name: GetCommentsRequest
        query-parameters:
          page: optional<integer>
          limit: optional<integer>
          objectType: optional<string>
          objectId: optional<string>
          authorUserId: optional<string>
      response: GetCommentsResponse

    get-by-id:
      docs: Get a comment by id
      method: GET
      path: /comments/{commentId}
      response: commons.Comment

I/O Contract

Endpoints

Method	Path	Description
POST	/api/public/comments	Create a comment attached to a trace, observation, session, or prompt
GET	/api/public/comments	List comments with optional filters (objectType, objectId, authorUserId) and pagination
GET	/api/public/comments/{commentId}	Get a specific comment by its unique ID

Key Types

Type Name	Description
CreateCommentRequest	Request body with projectId, objectType, objectId, content (markdown, max 5000 chars), and optional authorUserId
CreateCommentResponse	Response containing the created comment's id
GetCommentsResponse	Paginated list of commons.Comment objects with MetaResponse

Usage Examples

# Create a comment on a trace
curl -X POST "https://cloud.langfuse.com/api/public/comments" \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "projectId": "project-123",
    "objectType": "trace",
    "objectId": "trace-456",
    "content": "This trace shows unexpected latency in the second generation step."
  }'

# List comments for a specific trace
curl -X GET "https://cloud.langfuse.com/api/public/comments?objectType=trace&objectId=trace-456&page=1&limit=20" \
  -H "Authorization: Bearer $API_KEY"

# Get a comment by ID
curl -X GET "https://cloud.langfuse.com/api/public/comments/comment-789" \
  -H "Authorization: Bearer $API_KEY"

Related Pages

• Environment:Langfuse_Langfuse_Node_24_Runtime