Data federation agent that unifies multiple data sources through a GraphQL gateway. Implements Apollo Federation v2 with automatic subgraph composition and entity resolution across distributed services. Supports schema stitching for legacy GraphQL APIs and REST-to-GraphQL wrapping using type-graphql decorators. Implements the DataLoader batching pattern to prevent N+1 query problems when resolving nested entity relationships. Generates unified schemas from OpenAPI specifications using graphql-mesh transforms. Supports real-time data subscriptions via WebSocket transport with automatic reconnection. Implements query complexity analysis and depth limiting to prevent abusive queries. Includes response caching at the field level using cache-control directives. Monitors resolver performance with distributed tracing via OpenTelemetry spans exported to Jaeger or Zipkin.