openapi: 3.1.0
info:
  title: Open WebUI API
  description: |
    REST API exposed by a self-hosted Open WebUI instance. Endpoints include an
    OpenAI-compatible chat completions surface, an Anthropic-compatible messages
    endpoint, and a passthrough proxy for native Ollama endpoints. Authentication
    uses a Bearer token (Open WebUI session token or a per-user API key); each
    API key inherits the permissions of the user who created it.
  version: "1.0.0"
  contact:
    name: Open WebUI Documentation
    url: https://docs.openwebui.com/
servers:
  - url: http://localhost:3000
    description: Default local Open WebUI deployment
  - url: https://{host}
    description: User-deployed Open WebUI instance
    variables:
      host:
        default: openwebui.example.com
security:
  - BearerAuth: []
tags:
  - name: Chat
  - name: Anthropic
  - name: Ollama
paths:
  /api/chat/completions:
    post:
      tags: [Chat]
      summary: Chat completions (OpenAI-compatible)
      description: |
        OpenAI-compatible chat completions endpoint that routes requests to the
        configured backend (Ollama, OpenAI-compatible, or local model).
      requestBody:
        required: true
        content:
          application/json:
            schema: { $ref: '#/components/schemas/ChatCompletionRequest' }
      responses:
        '200':
          description: Chat completion response.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
  /api/v1/messages:
    post:
      tags: [Anthropic]
      summary: Anthropic-compatible messages
      description: Compatible with the Anthropic Messages API surface; usable with the Anthropic SDK and Claude Code.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              additionalProperties: true
              properties:
                model: { type: string }
                max_tokens: { type: integer }
                messages:
                  type: array
                  items: { $ref: '#/components/schemas/Message' }
      responses:
        '200':
          description: Anthropic-compatible messages response.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
  /ollama/api/tags:
    get:
      tags: [Ollama]
      summary: List Ollama models (passthrough)
      responses:
        '200':
          description: List of available Ollama models from the upstream daemon.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
  /ollama/api/generate:
    post:
      tags: [Ollama]
      summary: Generate completion via Ollama (passthrough)
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              additionalProperties: true
              properties:
                model: { type: string }
                prompt: { type: string }
                stream: { type: boolean }
      responses:
        '200':
          description: Ollama generation response.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
  /ollama/api/chat:
    post:
      tags: [Ollama]
      summary: Chat via Ollama (passthrough)
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              additionalProperties: true
              properties:
                model: { type: string }
                messages:
                  type: array
                  items: { $ref: '#/components/schemas/Message' }
      responses:
        '200':
          description: Ollama chat response.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
components:
  securitySchemes:
    BearerAuth:
      type: http
      scheme: bearer
      description: |
        Bearer token: Open WebUI session token or per-user API key. Each API key
        inherits the permissions of the user who created it.
  schemas:
    Message:
      type: object
      properties:
        role:
          type: string
          enum: [system, user, assistant, tool]
        content:
          type: string
      required: [role, content]
    ChatCompletionRequest:
      type: object
      additionalProperties: true
      properties:
        model: { type: string }
        messages:
          type: array
          items: { $ref: '#/components/schemas/Message' }
        stream: { type: boolean }
        temperature: { type: number }
        max_tokens: { type: integer }