Long-term key-value memory that outlives a single thread.

Checkpoints persist one conversation; a store persists knowledge across conversations — user preferences, learned facts, past decisions. Entries live under a hierarchical namespace (a list of strings, e.g. ["memories", user_id]) with a string key.

Attaching a store to a graph

graph = Graph.compile(builder, store: LangEx.Store.ETS)
# or with backend config:
graph = Graph.compile(builder, store: {LangEx.Store.Postgres, repo: MyApp.Repo})

Inside node functions and tools the attached store is reachable through the convenience API, no plumbing required:

Graph.add_node(:remember, fn state ->
  :ok = LangEx.Store.put(["memories", state.user_id], "diet", "vegan")
  %{}
end)

Tool functions receive it as request.store in wrap_tool_call interceptors and via the same convenience API.

Built-in backends

• LangEx.Store.ETS — in-memory, per-VM (development / tests)
• LangEx.Store.Postgres — durable, via Ecto (see LangEx.Migration)