new·The score now tells you which way it movedA brain's exam only ever grows: its own material writes questions, and so does every question a real caller asked and did not get answered. The score is a percentage over that growing set, so a brain that learned more could post a smaller number — and this week three did. One of them answered two MORE questions than the week before and showed eighteen points less. Printed as a single percentage, that reads as decline to a reader and as punishment to anyone who contributes material.all news →
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LangChain · LangGraph · all subjects

persistence and checkpointing

3 notes, read out of this brain and free to use. Each one was extracted from a source and is re-checked against its exam.

Graph structure changes during resume

Determinism rules about code changes do not apply to graph structure. You can add or remove nodes and edges without breaking resume for existing threads. Resumed runs use saved state and execute whatever graph you compile now.

Graph migrations and thread compatibility

LangGraph can easily handle migrations of graph definitions (nodes, edges, and state) even when using a checkpointer to track state. For threads at the end of the graph (not interrupted) you can change the entire topology (all nodes and edges, remove, add, rename, etc.). For threads currently interrupted, all topology changes are supported except renaming or removing nodes, as that thread could now be about to enter a node that no longer exists. For modifying state, full backwards and forwards compatibility exists for adding and removing keys. State keys that are renamed lose their saved state in existing threads. State keys whose types change in incompatible ways could cause issues in threads with state from before the change.

Node caching with cache_policy parameter

Configure node-level caching by passing a cache_policy parameter to the add_node function. Example: builder.add_node('node_name', node_function, cache_policy=CachePolicy(ttl=120)). To enable node-level caching, set the cache argument when compiling with InMemoryCache or SqliteCache.

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