Connect RPC
Protocol buffer-based RPC framework from Buf that works with HTTP/1.1, HTTP/2, and gRPC natively. Connect RPC solves gRPC's browser incompatibility by supporting the Connect protocol (HTTP/1.1 compatible) alongside standard gRPC and gRPC-Web. Services defined in .proto files generate type-safe server and client code. Available for Go, TypeScript/Node.js, Kotlin/Swift, and more. Developed by the team that built the Buf schema registry.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
TLS via transport layer. mTLS supported for service-to-service auth. Protobuf binary encoding not human-readable (reduces casual interception). Apache 2.0 licensed.
⚡ Reliability
Best When
You need strongly-typed, schema-first APIs that work across browsers, mobile, and services with streaming support, and your team is comfortable with Protocol Buffers.
Avoid When
Your team prefers JSON/REST, you don't need multi-language client generation, or you don't have streaming requirements.
Use Cases
- • Build type-safe RPC APIs using Protocol Buffers that work in browsers, mobile apps, and server-to-server communication without protocol switching
- • Replace REST APIs with schema-first RPC services that get auto-generated client SDKs in TypeScript, Go, Python, and other languages
- • Build streaming APIs (server streaming, client streaming, bidirectional) using Connect's unified protocol across HTTP/1.1 and HTTP/2
- • Migrate from gRPC to Connect to gain browser-native support while maintaining backward compatibility with existing gRPC clients
- • Define agent tool schemas in .proto files to generate strongly-typed clients for multiple languages from a single source of truth
Not For
- • Simple REST APIs — Connect's protobuf-first approach has higher setup overhead than JSON REST for simple use cases
- • Teams without Protocol Buffer familiarity — .proto files and protoc/buf compilation add complexity
- • Existing JSON REST APIs that need gradual migration — Connect requires protocol change; consider gRPC-gateway for REST+gRPC bridge
Interface
Authentication
Auth via interceptors (middleware) on client and server. Bearer tokens, mTLS, and custom auth headers all supported. Interceptor pattern is idiomatic for auth in Connect.
Pricing
Connect RPC is Apache 2.0 open source from Buf. The framework itself is free. Buf Schema Registry for hosting .proto files has free and paid tiers.
Agent Metadata
Known Gotchas
- ⚠ Connect RPC requires running protoc or buf generate to compile .proto files — agents cannot use Connect without the code generation step; generated files must be committed or generated in CI
- ⚠ Three protocols in one: Connect (HTTP/1.1 JSON/Protobuf), gRPC (HTTP/2 Protobuf), gRPC-Web (HTTP/1.1 Protobuf) — client and server must agree on protocol; default is Connect protocol
- ⚠ Browser clients use @connectrpc/connect-web but cannot use native gRPC (HTTP/2 framing not supported in browsers) — web clients always use Connect or gRPC-Web protocol
- ⚠ Field naming in generated TypeScript uses camelCase but .proto files use snake_case — JSON responses from Connect use camelCase; gRPC binary uses the original field numbers
- ⚠ Streaming requires HTTP/2 for bidirectional streams — load balancers must support H2 passthrough; many cloud load balancers terminate H2, breaking bidirectional streaming
- ⚠ Protobuf default values are NOT sent over the wire — zero values, empty strings, and false booleans are omitted; agents must distinguish between 'field not set' and 'field set to zero value'
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Connect RPC.
Scores are editorial opinions as of 2026-03-06.