Messages To Openai

# Anthropic Messages to Chat Completions
#
# Transforms Anthropic Messages API requests and responses for
# Chat Completions-compatible inference backends.
#
# The `anthropic_messages_to_chat_completions` filter name reflects the
# wire formats it bridges. It targets the Chat Completions wire shape,
# so any Chat Completions-compatible backend can use it, not only OpenAI.
#
# Request: system hoisting, content block flattening, tool mapping.
# Response: content blocks, stop_reason, usage mapping back to
# Anthropic format. Streaming responses are converted by
# `anthropic_messages_to_chat_completions_stream`.

listeners:
  - name: anthropic-gateway
    address: "127.0.0.1:8080"
    filter_chains: [anthropic-transform]

filter_chains:
  - name: anthropic-transform
    filters:
      - filter: anthropic_messages_format
        on_invalid: continue

      - filter: anthropic_messages_to_chat_completions
        max_body_bytes: 1048576

      # response_conditions is optional: the filter self-arms via
      # metadata and Content-Type checks internally. Adding it
      # skips filter dispatch entirely for non-SSE responses.
      - filter: anthropic_messages_to_chat_completions_stream
        max_partial_event_bytes: 10485760
        # Cap on distinct streaming tool-call content blocks retained per
        # response. Bounds per-response memory when an upstream streams
        # many unique tool-call indices; exceeding it fails the stream
        # closed.
        max_tool_blocks: 10000
        response_conditions:
          - when:
              headers:
                content-type: "text/event-stream"

      - filter: path_rewrite
        replace:
          pattern: "^/v1/messages$"
          replacement: "/v1/chat/completions"
        conditions:
          - when:
              path_prefix: "/v1/messages"

      - filter: router
        routes:
          - path_prefix: "/"
            cluster: "chat-completions-backend"

      - filter: load_balancer
        clusters:
          - name: "chat-completions-backend"
            endpoints:
              - "127.0.0.1:8000"

insecure_options:
  allow_private_endpoints: true # example proxies to local backends