Response Interceptor Capability

The response interceptor capability rewrites response headers or bodies before a successful non-streaming HTTP execution response is returned to the client.

Capability Field

{
  "capabilities": {
    "response_interceptor": true
  }
}

Source references:

• sdk/pluginapi/types.go: ResponseInterceptor, ResponseInterceptRequest, ResponseInterceptResponse
• sdk/pluginabi/types.go: response.intercept_after
• internal/pluginhost/adapters.go: InterceptResponse

Example references:

• internal/pluginhost/adapters_test.go: tests for response interceptor chains, header clearing, and error handling
• examples/plugin/antigravity-web-search/go/main.go: real migration example based on response interception

Methods

Method	Purpose
response.intercept_after	Rewrites successful non-streaming responses.

Request

{
  "SourceFormat": "chat-completions",
  "Model": "gpt-5.5",
  "RequestedModel": "gpt-5.5",
  "Stream": false,
  "RequestHeaders": {},
  "ResponseHeaders": {},
  "OriginalRequest": "base64-client-body",
  "RequestBody": "base64-upstream-request",
  "Body": "base64-response-body",
  "StatusCode": 200,
  "Metadata": {}
}

Response

{
  "Headers": {
    "X-Plugin": ["example"]
  },
  "Body": "base64-new-response-body",
  "ClearHeaders": ["X-Old-Header"]
}

Development Notes

• This only handles successful non-streaming responses. Use the streaming response interceptor capability for streaming responses.
• Headers overrides response headers with the same name while preserving headers that are not mentioned.
• A non-empty Body replaces the response body.
• Host model callbacks started with host_callback_id skip the originating plugin's own response interceptors.