​

Overview

• System message extraction - Removed from messages array, placed in separate system field
• Tool message grouping - Consecutive tool messages merged into single user message
• Thinking block transformation - reasoning parameters mapped to Anthropic’s thinking structure
• Parameter renaming - e.g., max_completion_tokens → max_tokens, stop → stop_sequences
• Content format conversion - Images, files, and other content types adapted to Anthropic’s schema

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Supported Operations

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Beta Headers

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1. Chat Completions

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Request Parameters

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Parameter Mapping

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Dropped Parameters

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Extra Parameters

curl -X POST http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-3-5-sonnet",
    "messages": [{"role": "user", "content": "Hello"}],
    "top_k": 40
  }'

resp, err := client.ChatCompletionRequest(schemas.NewBifrostContext(ctx, schemas.NoDeadline), &schemas.BifrostChatRequest{
    Provider: schemas.Anthropic,
    Model:    "claude-3-5-sonnet",
    Input:    messages,
    Params: &schemas.ChatParameters{
        ExtraParams: map[string]interface{}{
            "top_k": 40,
        },
    },
})

​

Cache Control

curl -X POST http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-3-5-sonnet",
    "messages": [
      {
        "role": "user",
        "content": [
          {
            "type": "text",
            "text": "This is cached context",
            "cache_control": {"type": "ephemeral"}
          }
        ]
      }
    ],
    "system": [
      {
        "type": "text",
        "text": "You are a helpful assistant",
        "cache_control": {"type": "ephemeral"}
      }
    ]
  }'

resp, err := client.ChatCompletionRequest(schemas.NewBifrostContext(ctx, schemas.NoDeadline), &schemas.BifrostChatRequest{
    Provider: schemas.Anthropic,
    Model:    "claude-3-5-sonnet",
    Input: []schemas.ChatMessage{
        {
            Role: schemas.ChatMessageRoleUser,
            Content: &schemas.ChatMessageContent{
                ContentBlocks: []schemas.ChatContentBlock{
                    {
                        Text: schemas.Ptr("This is cached context"),
                        CacheControl: &schemas.CacheControl{
                            Type: schemas.Ptr("ephemeral"),
                        },
                    },
                },
            },
        },
    },
    SystemMessages: []schemas.ChatMessage{
        {
            Role: schemas.ChatMessageRoleSystem,
            Content: &schemas.ChatMessageContent{
                ContentBlocks: []schemas.ChatContentBlock{
                    {
                        Text: schemas.Ptr("You are a helpful assistant"),
                        CacheControl: &schemas.CacheControl{
                            Type: schemas.Ptr("ephemeral"),
                        },
                    },
                },
            },
        },
    },
})

​

Reasoning / Thinking

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Parameter Mapping

• reasoning.effort → thinking.type (always mapped to "enabled")
• reasoning.max_tokens → thinking.budget_tokens (token budget for thinking)

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Critical Constraints

• Minimum budget: 1024 tokens required; requests below this fail with error
• Dynamic budget: -1 is converted to 1024 automatically

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Example

// Request
{"reasoning": {"effort": "high", "max_tokens": 2048}}

// Anthropic conversion
{"thinking": {"type": "enabled", "budget_tokens": 2048}}

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Message Conversion

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Critical Caveats

• System message extraction: System messages are removed from messages array and placed in separate system field. Multiple system messages become separate text blocks in the system array.
• Tool message grouping: Consecutive tool messages are merged into single user message with tool_result content blocks.

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Image Conversion

• URL images: {"type": "image_url", "image_url": {}} → {"type": "image", "source": {"type": "url", ...}}
• Base64 images: Data URL → {"type": "image", "source": {"type": "base64", "media_type": "image/png", ...}}

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Cache Control Locations

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Tool Conversion

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Response Conversion

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Field Mapping

• stop_reason → finish_reason: end_turn/stop_sequence → stop, max_tokens → length, tool_use → tool_calls
• input_tokens + cache_read_input_tokens + cache_creation_input_tokens → prompt_tokens (all cache counts rolled into the total)
• Cache token breakdown surfaced in prompt_tokens_details:
  • cache_read_input_tokens → prompt_tokens_details.cached_read_tokens
  • cache_creation_input_tokens → prompt_tokens_details.cached_write_tokens
• output_tokens → completion_tokens
• thinking blocks → reasoning_details with index, type, text, and signature fields
• Tool call arguments converted from JSON object → JSON string

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Streaming

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Caveats

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2. Responses API

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Request Parameters

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Parameter Mapping

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Extra Parameters

curl -X POST http://localhost:8080/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-3-5-sonnet",
    "input": "Hello, how are you?",
    "top_k": 40
  }'

resp, err := client.ResponsesRequest(schemas.NewBifrostContext(ctx, schemas.NoDeadline), &schemas.BifrostResponsesRequest{
    Provider: schemas.Anthropic,
    Model:    "claude-3-5-sonnet",
    Input:    messages,
    Params: &schemas.ResponsesParameters{
        ExtraParams: map[string]interface{}{
            "top_k": 40,
        },
    },
})

​

Cache Control

curl -X POST http://localhost:8080/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-3-5-sonnet",
    "instructions": "You are a helpful assistant. This instruction is cached.",
    "instructions_cache_control": {"type": "ephemeral"},
    "input": [
      {
        "type": "text",
        "text": "Answer this question",
        "cache_control": {"type": "ephemeral"}
      }
    ]
  }'

resp, err := client.ResponsesRequest(schemas.NewBifrostContext(ctx, schemas.NoDeadline), &schemas.BifrostResponsesRequest{
    Provider: schemas.Anthropic,
    Model:    "claude-3-5-sonnet",
    Input: []schemas.ChatMessage{
        {
            Role: schemas.ChatMessageRoleUser,
            Content: &schemas.ChatMessageContent{
                ContentBlocks: []schemas.ChatContentBlock{
                    {
                        Text: schemas.Ptr("Answer this question"),
                        CacheControl: &schemas.CacheControl{
                            Type: schemas.Ptr("ephemeral"),
                        },
                    },
                },
            },
        },
    },
    Params: &schemas.ResponsesParameters{
        Instructions: schemas.Ptr("You are a helpful assistant. This instruction is cached."),
        InstructionsCacheControl: &schemas.CacheControl{
            Type: schemas.Ptr("ephemeral"),
        },
    },
})

​

Input & Instructions

• Input: String wrapped as user message or array converted to messages
• Instructions: Becomes system message (same extraction as Chat Completions)

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Tool Support

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Response Conversion

• stop_reason → status: end_turn/stop_sequence → completed, max_tokens → incomplete
• Top-level input_tokens and output_tokens are rollups that include cache-related usage; they map as input_tokens → input_tokens | output_tokens → output_tokens.
• Cache-specific counts are exposed in details: cache_read_input_tokens → input_tokens_details.cached_read_tokens | cache_creation_input_tokens → input_tokens_details.cached_write_tokens
• Output items: text → message | tool_use → function_call | thinking → reasoning

​

Streaming

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3. Text Completions (Legacy)

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4. Batch API

• POST /v1/messages/batches - Create
• GET /v1/messages/batches - List
• GET /v1/messages/batches/{batch_id} - Retrieve
• POST /v1/messages/batches/{batch_id}/cancel - Cancel

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5. Files API

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6. List Models