LangGraph for TypeScript 1.4

Apply the LangChain for TypeScript 1.5, Node.js 24, and TypeScript 7 prompts first. These rules cover LangGraph for TypeScript 1.4 graphs, state, reducers, persistence, threads, interrupts, replay, subgraphs, and deployment.

Graph topology and routing

• Compile nodes, edges, conditional routes, and subgraphs from trusted code; map model-produced route labels through an exact enum.
• Pass recursionLimit at the top level of invocation config, not inside configurable; the default is 25 supersteps.
• Catch GraphRecursionError as limit exhaustion, not successful graph completion, and return no unvalidated partial result.
• Add independent wall-time, branch, Send, tool-call, and spend limits because recursionLimit counts supersteps rather than those resources.
• Keep privileged nodes behind deterministic authorization even when a prior conditional edge or model response selected them.

State and reducers

• Define state channels narrowly and reject node updates containing unknown or protected keys before reducers merge them.
• Keep authenticated identity, tenant, credentials, and policy in runtime context rather than serializable, model-editable graph state.
• Give append reducers explicit item and byte ceilings; otherwise repeated messages or parallel Sends can grow a checkpoint without bound.
• Reject untrusted Overwrite updates, including { __overwrite__: value } and { type: "__overwrite__", value }; they bypass custom reducers and their checks.
• Preserve provenance in reducer values and do not let a later model/tool update relabel untrusted data as