rust-langgraph

Rust redesign of LangGraph — not a direct port. Leverages Rust's ownership, async traits, and type system rather than mimicking JS/TS patterns.

Build & Test

cargo build
cargo test
cargo test -p langgraph-core
cargo run --example basic_agent
cargo clippy -- -D warnings

Crate	Purpose
`langgraph-core`	Graph builder, Pregel engine, channels, types, errors
`langgraph-checkpoint`	`Checkpointer` trait + memory/sqlite/postgres/redis backends
`langgraph-prebuilt`	`ReactAgent`, `ToolNode`, prompt utilities
`langgraph-runtime`	High-level runtime wrapping core + checkpoint
`langgraph-observability`	Metrics, tracing, dashboard

State = GraphState trait bound: any Clone + Serialize + Deserialize + Send + Sync. No reflection needed.
Node = NodeFunction<S> trait: blanket-impl for async fn(S, ExecutionContext) -> GraphResult<NodeOutput<S>>. Node returns StateUpdate (a JsonMap) merged via channels.
Pregel / BSP execution: nodes run in parallel supersteps; state is immutable during a step; updates applied atomically after barrier.
Channels type-dispatch state merging per key: LastValue, Accumulator, BinaryOp, Ephemeral. Configured via StateGraph::set_channel_type.
Command<S> enables routing: Goto, Send (fan-out to specific nodes with state), Interrupt.
Checkpointer is generic over S — thread-scoped, supports get_latest, list, put, delete.

Applies my-rust-standards skill (see .claude/skills/my-rust-standards/SKILL.md)
No unwrap/expect in non-test code
Errors via thiserror — LangGraphError / GraphResult<T>
No multi-paragraph doc comments; terse /// only where non-obvious
Test names: test_<subject>_<condition> — max 3 words after test_

See docs/missing-features.md for planned work.