Fence provisional writes against durable terminal state

When an asynchronous publisher offloads storage to a worker thread, cancelling its task does not cancel a database request already in flight. Stop the publisher before saving the authoritative final state, and make every provisional write conditional on the durable record still being unfinished. Put the condition on the update itself; a preceding read can race with finalization. One serial writer and a replaceable pending snapshot keep provisional writes ordered without blocking the main workload. This rule protects terminal state, but does not provide retries after process loss or prove physical thread termination.

Applies when: Background snapshots share a record with an authoritative finalizer. Keywords: cancellation thread database terminal snapshot finalization late write concurrency