langgraph

LangGraph Workflow Patterns

Comprehensive patterns for building production LangGraph workflows. LangGraph 1.x is LTS (Long Term Support) — the first stable major release, powering agents at Uber, LinkedIn, and Klarna. Each category has individual rule files in rules/ loaded on-demand.

LangGraph 1.2 (shipped 2026-05-12) — the fault-tolerance release. Everything below is on StateGraph.add_node(...) unless noted:

• Per-node timeouts — timeout= accepts float | timedelta | TimeoutPolicy. TimeoutPolicy(run_timeout=, idle_timeout=, refresh_on="auto"|"heartbeat") separates a hard wall-clock cap from an idle cap that progress refreshes. On expiry LangGraph raises NodeTimeoutError (carrying kind="idle"|"run" and elapsed), drops that attempt's writes, and defers to the retry policy. Cooperative: it rides asyncio cancellation, so a node blocking the GIL is not interrupted. See rules/resilience-node-timeouts.md.
• Node error handlers — error_handler= registers a recovery node that runs once the retry budget is exhausted. It receives failure context by declaring a parameter typed NodeError (fields node, error) and returns a Command to update state and reroute. See rules/resilience-error-handlers.md.
• RunControl (langgraph.runtime) — cooperative graceful shutdown. request_drain(reason) from any thread; nodes poll runtime.drain_requested and stop at a checkpoint boundary, leaving a resumable thread instead of a half-applied superstep. See rules/resilience-graceful-drain.md.
• DeltaChannel (langgraph.channels.delta, beta) — checkpoints store only incremental writes and replay them through a batch reducer, with a snapshot every snapshot_frequency updates. Fixes checkpoint cost growing with thread length. Its reducer takes a batch and must be batching-invariant. See rules/state-delta-channel.md.
• runtime.heartbeat() — explicit progress signal, the only one that refreshes an idle timeout under refresh_on="heartbeat".

Landed earlier, in 1.1 — not 1.2 (they are current and supported; only their release attribution was wrong in prior versions of this skill): deferred nodes (defer=True), node-level caching (CachePolicy + graph.compile(cache=...)), and model middleware (before_model / after_model) on create_agent.