LangDB Threads API

openapi: 3.0.1
info:
  title: LangDB AI Gateway Analytics Threads API
  description: OpenAI-compatible REST API for the LangDB AI Gateway. A single, project-scoped endpoint routes chat completions, embeddings, and image generation across 250+ models from providers such as OpenAI, Anthropic, Google, Meta, Mistral, and DeepSeek, while adding routing, guardrails, tracing, cost control, and an MCP (Model Context Protocol) gateway. Requests are authenticated with a Bearer API key and scoped to a project either by embedding the project id in the path (`/{project_id}/v1/...`) or by sending an `X-Project-Id` header. Tracing and session headers (`X-Thread-Id`, `X-Run-Id`, `X-Label`) attach observability metadata to each call.
  termsOfService: https://langdb.ai/terms
  contact:
    name: LangDB Support
    url: https://langdb.ai
    email: support@langdb.ai
  version: '1.0'
servers:
- url: https://api.us-east-1.langdb.ai/{project_id}/v1
  description: Project-scoped OpenAI-compatible base (US East 1).
  variables:
    project_id:
      default: your-langdb-project-id
      description: LangDB project id. May instead be supplied via the X-Project-Id header.
- url: https://api.us-east-1.langdb.ai
  description: Root base URL for analytics, usage, and thread management endpoints (US East 1).
security:
- bearerAuth: []
tags:
- name: Threads
  description: Conversation threads, their messages, and per-thread cost.
paths:
  /threads/{thread_id}/messages:
    get:
      operationId: getThreadMessages
      tags:
      - Threads
      summary: Get messages for a thread
      description: Retrieves the ordered messages belonging to a conversation thread.
      parameters:
      - $ref: '#/components/parameters/ProjectIdHeader'
      - name: thread_id
        in: path
        required: true
        description: The thread identifier.
        schema:
          type: string
      responses:
        '200':
          description: The thread's messages.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ThreadMessageList'
        '401':
          $ref: '#/components/responses/Unauthorized'
  /threads/{thread_id}/cost:
    get:
      operationId: getThreadCost
      tags:
      - Threads
      summary: Get the cost of a thread
      description: Returns the aggregated cost and token usage for a conversation thread.
      parameters:
      - $ref: '#/components/parameters/ProjectIdHeader'
      - name: thread_id
        in: path
        required: true
        description: The thread identifier.
        schema:
          type: string
      responses:
        '200':
          description: The thread's cost summary.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ThreadCost'
        '401':
          $ref: '#/components/responses/Unauthorized'
components:
  responses:
    Unauthorized:
      description: Missing or invalid API key.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  schemas:
    ThreadMessageList:
      type: object
      properties:
        thread_id:
          type: string
        messages:
          type: array
          items:
            $ref: '#/components/schemas/ChatMessage'
    ChatMessage:
      type: object
      required:
      - role
      - content
      properties:
        role:
          type: string
          enum:
          - system
          - user
          - assistant
          - tool
        content:
          oneOf:
          - type: string
          - type: array
            items:
              type: object
        name:
          type: string
        tool_call_id:
          type: string
    ThreadCost:
      type: object
      properties:
        thread_id:
          type: string
        total_cost:
          type: number
        input_tokens:
          type: integer
        output_tokens:
          type: integer
    Error:
      type: object
      properties:
        error:
          type: object
          properties:
            message:
              type: string
            type:
              type: string
            code:
              type: string
  parameters:
    ProjectIdHeader:
      name: X-Project-Id
      in: header
      required: false
      description: LangDB project id. Optional when the project id is embedded in the request path.
      schema:
        type: string
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT
      description: 'LangDB API key (project access token) sent as `Authorization: Bearer <token>`.'