{
  "id": "page:docs-development-04-transport-adapter-proxy",
  "_kind": "Page",
  "_file": "wiki/docs/development/04-transport-adapter-proxy.md",
  "_cluster": "wiki",
  "attributes": {
    "nodeKind": "Page",
    "sourcePath": "docs/development/04-transport-adapter-proxy.md",
    "sourceKind": "repo-docs",
    "title": "Transport Adapter & Proxy",
    "displayName": "Transport Adapter & Proxy",
    "slug": "docs/development/04-transport-adapter-proxy",
    "articlePath": "wiki/docs/development/04-transport-adapter-proxy.md",
    "article": "\n# Transport Adapter & Proxy\n\nThe `@a5c-ai/transport-adapter` package bridges API protocol differences between harnesses and upstream providers.\n\n## When Proxy is Needed\n\nA harness needs the proxy when it speaks a different protocol than the upstream provider:\n\n| Harness Protocol | Upstream Protocol | Proxy? |\n|-----------------|-------------------|--------|\n| Anthropic (Claude Code) | Anthropic | No |\n| Anthropic (Claude Code) | OpenAI (Foundry) | **Yes** |\n| Anthropic (Claude Code) | Google (Vertex) | **Yes** |\n| OpenAI (Codex) | OpenAI (Foundry) | No |\n| OpenAI (Pi via models.json) | OpenAI (Foundry) | **Yes** |\n\n## Completion Engines\n\n| Engine | Upstream | Key Features |\n|--------|----------|-------------|\n| OpenAI | Azure Foundry | Tool normalization (`input_schema` → `parameters`), streaming `delta.tool_calls` accumulation |\n| Google | Vertex AI | `functionCall`/`functionResponse` translation, `thoughtSignature` server-side store |\n\n## Message Translation\n\nThe proxy translates between Anthropic and upstream formats bidirectionally:\n\n- **Anthropic → OpenAI**: `tool_use` → `role:\"assistant\" + tool_calls`, `tool_result` → `role:\"tool\"`\n- **Anthropic → Google**: `tool_use` → `functionCall`, `tool_result` → `functionResponse` (with `toolIdToName` mapping)\n- **OpenAI → Anthropic**: `delta.tool_calls` → `content_block_start(tool_use) + input_json_delta`\n- **Google → Anthropic**: `functionCall` → `tool_use`, `thoughtSignature` preserved via server-side store\n\n## Streaming Tool Support\n\nThe proxy handles streaming tool calls end-to-end:\n\n```\nCompletionStreamEvent =\n  | { type: 'text-delta', text: string }\n  | { type: 'tool-call', id, name, arguments, metadata? }\n  | { type: 'done', finishReason?, usage? }\n```\n\nSee [babysitter-plugin-flows](./03-babysitter-plugin-flows.md) for full sequence diagrams.\n",
    "documents": []
  },
  "outgoingEdges": [],
  "incomingEdges": [
    {
      "from": "page:docs-development",
      "to": "page:docs-development-04-transport-adapter-proxy",
      "kind": "contains_page"
    }
  ]
}