Observed

The two layers exist as described. Cross-session persistence requires a durable checkpointer: the default in-memory saver is scoped by the vendor's own docs to experimentation and silently resets across process restarts if PostgresSaver is omitted — state appears functional in local testing, then resets in production. With a durable checkpointer, round-trips are lossy for Pydantic models and enums (rows 4–5), so long-term memory is reliable only for primitive-typed state without defensive post-restore validation.