The concurrency model

One open handle per store per process. This is a real constraint of redb (ADR-0008), confirmed directly, not a design choice this project could lift without changing the storage engine: opening a second Store (or an adapter wrapping one - MnemosyneStore, MnemosyneStorageBackend, a Session, a Memory) on a path a first one in the same process already holds raises

StoreIoError: Database already open. Cannot acquire lock.

What this rules out

Two handles open in the same process, at the same instant, on the same store path. A long-running process that opens a store once and holds it for the process's lifetime is fine; a process that opens, finishes, and lets the handle drop before a second one opens is fine. What doesn't work is holding two live handles side by side - the classic way to hit this by accident is constructing two adapter instances against the same path in one script without ever letting the first go out of scope.

What this does not rule out

Multiple agents, even across different frameworks, sharing one store

• just not at the exact same instant from the same process. The normal git-like pattern already works today: each agent's process opens the store, does its work, and either closes (handle dropped) or holds for its own run's lifetime; merging two agents' divergent work happens the same way any two branches merge, with no special-casing for which adapter or framework wrote which side (see examples/cross_framework_merge.py). Sequential access across processes - one agent's run finishes before another's starts, or they're simply never open on the same path concurrently - is the real, supported pattern.

What would need a daemon

True concurrent access - two processes with the store open on the same path at the same instant, each reading and writing without stepping on the other - needs a server process mediating access, already noted as a backlog item in ROADMAP.md. Nothing in the current substrate provides this, and this document should not be read as implying it does.

Related: each adapter's own README documents a "Sharing a store with other adapters" section stating what id shape it owns (mnem-crewai, mnem-langgraph, mnem-openai-agents, mnem-autogen); this document covers when a store can safely be opened at all. See shared memory across frameworks for the practical how-to this feeds: branches vs a shared one, and how a real conflict surfaces and resolves.