Implementation:Ollama Ollama Anthropic Handler

Knowledge Sources	Ollama
Domains	API Compatibility, Anthropic Protocol
Last Updated	2025-02-15 00:00 GMT

Overview

Implements the Anthropic Messages API compatibility layer, translating Anthropic-format requests into Ollama internal calls and streaming responses back in the Anthropic SSE format.

Description

The anthropic package provides a full HTTP handler that accepts Anthropic Messages API requests, validates them, converts the message format (including text, images, tool calls, and tool results) to Ollama's internal api.ChatRequest, forwards the request to the Ollama chat endpoint, and streams responses back as Anthropic-compatible server-sent events. It handles error mapping between HTTP status codes and Anthropic error types, supports both streaming and non-streaming modes, and generates unique request and message IDs.

Usage

Used when a client sends requests to the /v1/messages endpoint using the Anthropic Messages API format. The handler is registered on the server's router and activated for any Anthropic-compatible client integration.

Code Reference

Source Location

• Repository: Ollama
• File: anthropic/anthropic.go
• Lines: 1-1210

Signature

type Error struct {
    Type    string `json:"type"`
    Message string `json:"message"`
}

type ErrorResponse struct {
    Type      string `json:"type"`
    Error     Error  `json:"error"`
    RequestID string `json:"request_id,omitempty"`
}

func NewError(code int, message string) ErrorResponse
func (s *Server) handleMessages(w http.ResponseWriter, r *http.Request)
func toChatRequest(ar *AnthropicRequest) (*api.ChatRequest, error)
func fromChatResponse(cr *api.ChatResponse, sb *strings.Builder) MessageResponse
func stream(w http.ResponseWriter, ch <-chan any)

Import

import "github.com/ollama/ollama/anthropic"

I/O Contract

Inputs

Name	Type	Required	Description
r	*http.Request	Yes	HTTP request containing Anthropic Messages API JSON body
AnthropicRequest.Model	string	Yes	Model name to use for inference
AnthropicRequest.Messages	[]Message	Yes	Conversation messages in Anthropic format (text, image, tool_use, tool_result)
AnthropicRequest.MaxTokens	int	Yes	Maximum number of tokens to generate
AnthropicRequest.Stream	bool	No	Whether to stream the response via SSE
AnthropicRequest.System	string	No	System prompt text

Outputs

Name	Type	Description
MessageResponse	JSON	Anthropic-format message response with content blocks, usage stats, and stop reason
SSE stream	text/event-stream	Streamed events: message_start, content_block_start, content_block_delta, content_block_stop, message_delta, message_stop
ErrorResponse	JSON	Anthropic-format error with type classification (invalid_request_error, authentication_error, etc.)

Usage Examples

// Register the Anthropic handler on the server
mux.HandleFunc("/v1/messages", s.handleMessages)

// Client sends an Anthropic Messages API request
// POST /v1/messages
// {
//   "model": "llama3",
//   "max_tokens": 1024,
//   "messages": [{"role": "user", "content": "Hello"}],
//   "stream": true
// }

Related Pages

• Principle:Ollama_Ollama_Anthropic_API_Compatibility