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Parameter Mappings & Transformations

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Basic Parameter Mappings

  • model → direct mapping (default: ‘claude-2.1’)
  • max_tokens → direct mapping to max_tokens
  • temperature → direct mapping (constrained: 0-1)
  • top_p → direct mapping (default: -1)
  • stream → direct mapping (default: false)
  • user → mapped to metadata.user_id
  • stop → mapped to stop_sequences
  • max_completion_tokens → mapped to max_tokens

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Complex Transformations

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Messages Transformation

  1. System Messages:
    • Extracted from messages array where role === 'system'
    • Transformed into AnthropicMessageContentItem[]
    • Handles both string content and object content with text
    • Preserves cache control metadata if present
  2. Assistant Messages (transformAssistantMessage):
    • Transforms content into Anthropic’s content array format
    • Handles tool calls by converting them into Anthropic’s tool_use format
    • Text content is wrapped in {type: 'text', text: content}
    • Tool calls are transformed into {type: 'tool_use', name: function.name, id: toolCall.id, input: parsed_arguments}
  3. Tool Messages (transformToolMessage):
    • Converted to user role with tool_result type
    • Preserves tool_call_id as tool_use_id
    • Content wrapped in specific format: {type: 'tool_result', tool_use_id: id, content: string}
  4. User Messages with Images:
    • Handles base64 encoded images in content
    • Transforms them into Anthropic’s image format with proper media type
    • Preserves cache control metadata

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Tools Transformation

  • Converts OpenAI-style function definitions to Anthropic tool format
  • Maps function parameters to input_schema
  • Preserves cache control metadata
  • Structure transformation: 
    OpenAI: {function: {name, description, parameters}}
↓
Anthropic: {name, description, input_schema: {type, properties, required}}

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Tool Choice Transformation

  • ‘required’ → {type: 'any'}
  • ‘auto’ → {type: 'auto'}
  • Function specification → {type: 'tool', name: function.name}

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Response Transformations

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Regular Response

  1. Content Processing:
    • Extracts text content from first content item if type is ‘text’
    • Processes tool_use items into OpenAI tool_calls format
    • Preserves tool IDs and function names
  2. Usage Statistics:
    • Maps input_tokens → prompt_tokens
    • Maps output_tokens → completion_tokens
    • Calculates total_tokens
    • Preserves cache-related tokens if present

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Streaming Response

  1. Event Handling:
    • Filters out ‘ping’ and ‘content_block_stop’ events
    • Converts ‘message_stop’ to ‘[DONE]’
    • Handles multiple event types: content_block_delta, content_block_start, message_delta, message_start
  2. Special States:
    • Tracks chain of thought messages
    • Maintains usage statistics across stream
    • Handles tool streaming differently based on message context

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Edge Cases & Special Handling

  1. Image Content:
    • Special handling for base64 encoded images
    • Parses media type from data URL
    • Validates image URL format
  2. Tool Streaming:
    • Handles partial JSON in tool arguments
    • Manages tool indices differently when chain-of-thought messages are present
    • Separates tool name and arguments into different stream chunks
  3. Cache Control:
    • Preserves ephemeral cache control metadata throughout transformations
    • Handles cache usage statistics in both regular and streaming responses
  4. Error Handling:
    • Transforms Anthropic-specific error format to universal format
    • Preserves error types and messages
    • Handles non-200 response status codes
  5. Empty/Null Handling:
    • Safely handles missing usage statistics
    • Manages undefined tool calls
    • Handles empty content arrays