Module: Hitch::MCP::Endpoint

Extended by:
ActiveSupport::Concern
Includes:
RequestAdmission
Defined in:
app/controllers/concerns/hitch/mcp/endpoint.rb

Overview

Authenticated, stateless MCP 2026-07-28 JSON endpoint for a dedicated host-owned ActionController::API controller.

Constant Summary

Constants included from RequestAdmission

RequestAdmission::MAX_REQUEST_BODY_BYTES

Instance Method Summary collapse

Instance Method Details

#handle ⇒ Object 



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# File 'app/controllers/concerns/hitch/mcp/endpoint.rb', line 23

def handle
  unless Internal::MediaType.json_content_type?(request.get_header("CONTENT_TYPE"))
    hitch_mcp_explain!("Content-Type must be exactly application/json")
    return hitch_mcp_protocol_error!(415, -32600, "Invalid Request")
  end
  unless Internal::MediaType.accepts_required_types?(request.get_header("HTTP_ACCEPT"))
    hitch_mcp_explain!("Accept must admit both application/json and text/event-stream")
    return hitch_mcp_protocol_error!(406, -32600, "Invalid Request")
  end

  max_request_bytes = Hitch.configuration.mcp.max_request_bytes
  raw_body = hitch_read_bounded_request_body(max_request_bytes)
  @hitch_mcp_observation&.request_bytes!(raw_body ? raw_body.bytesize : max_request_bytes + 1)
  unless raw_body
    hitch_mcp_explain!("request body exceeds mcp.max_request_bytes (#{max_request_bytes})")
    return hitch_mcp_protocol_error!(413, -32600, "Invalid Request")
  end

  verified_request = Internal::VerifiedRequest.call(
    raw_body: raw_body,
    headers: {
      protocol_version: request.get_header("HTTP_MCP_PROTOCOL_VERSION"),
      method: request.get_header("HTTP_MCP_METHOD"),
      name: request.get_header("HTTP_MCP_NAME")
    }
  )
  @hitch_mcp_observation&.verified!(verified_request)

  hitch_mcp_dispatch!(verified_request)
rescue Internal::VerifiedRequest::Failure => error
  # The wire deliberately says only "Invalid params" for a dozen
  # different rejections. Locally the first backtrace frame names the
  # exact check that refused, which is the difference between a
  # developer fixing their request and guessing at it.
  Internal::LocalDiagnosis.report(
    "MCP request rejected (#{error.code} #{error.message})", error
  )
  hitch_mcp_protocol_error!(
    error.http_status,
    error.code,
    error.message,
    request_id: error.request_id,
    data: error.data
  )
rescue StandardError => error
  request_id = verified_request && verified_request["id"]
  Internal::EndpointErrorReporter.report(category: :dispatch)
  Internal::LocalDiagnosis.report("MCP request failed during dispatch", error)
  hitch_mcp_protocol_error!(200, -32603, "Internal error", request_id: request_id)
ensure
  request.delete_header("RAW_POST_DATA") if request
end