A2A in Rust: An independent SDK ships against the v1.0.1 spec, with multi-transport support and real conformance gaps

The A2A protocol is the most visible open effort to make AI agents talk to each other across vendors, and as that standard matures, teams running Rust backends increasingly face a choice: adopt Google’s official Go SDK or wait for parity. An independent Rust implementation closes that gap — type-safe, async, and wired to the v1.0.1 wire spec (released 2026-05-28) across four transports: JSON-RPC 2.0, REST, WebSocket, and gRPC, both client and server. For builders whose stacks already lean on Rust, this means agent orchestration doesn’t have to mean adopting a foreign runtime just to interoperate. What the source says concretely: the SDK is Apache-2.0 licensed, targets Rust 1.94+, and ships real server infrastructure — pluggable TaskStore and PushConfigStore traits with in-memory, SQLite, and PostgreSQL backends, plus tenant-aware isolation that refuses shared-store requests naming a tenant. It also offers SSE streaming, push notifications via a PushSender trait, agent-card discovery with hot-reload, JWS signing, and HTTP caching. On the client side, the same quad-transport surface covers JSON-RPC, REST, WebSocket, and gRPC. A community-contributed SLIMRPC binding extends A2A over the AGNTCY SLIM fabric — outside the ratified v1.0 spec, so treat it as experimental. Where it falls short