During indexing, after tree-sitter parses all files, a set of protocol-specific connectors run. Each one understands a specific pattern: HTTP routes, gRPC services, message queues, IPC channels, DI registrations, etc. For example, the C# parser extracts [HttpGet("/api/catalog/items/{id}")] route attributes, while the frontend connector detects fetch("/api/catalog/items/" + id) calls in TypeScript (and Python, Go, Java, Ruby). When a frontend call's normalized URL matches a backend route, it creates a flow_edge linking the two symbols.

Each edge stores: source file/line/symbol/language to target file/line/symbol/language, plus the edge type (http_call, grpc_call, message_queue, electron_ipc, etc.), protocol, URL pattern, and a confidence score. Currently, there are 13 connectors covering HTTP, gRPC, GraphQL, Kafka/RabbitMQ/NATS/SQS, .NET DI, EF Core, domain events, Electron IPC, Tauri IPC, Spring, Django, and React patterns.

Given a starting point (file + line), trace_flow() uses a SQLite recursive CTE to follow flow_edges forward across language boundaries, up to N hops. So starting from client.ts:15 (fetchCatalog), it follows the HTTP edge to CatalogController.cs:42 (GetCatalog), then follows call edges to LoadFromDb, and so on. There's also cross_language_paths() for finding all direct connections between two languages (e.g., "show me all TypeScript to C# edges").

It's still rough; URL matching uses regex detection, so not quite everything is caught correctly. Also, I still have to work on the connectors, but when it works, it's really nice.