2 sessions meaning 2 processes, the knowl.db file uses WAL + 10s busy_timeout. Along with 'BEGIN IMMEDIATE' to avoid read transactions upgrading mid-write. Writes are queued so transactions don't collide with each other.
About the sync about 2 different sessions or even agents/subagents, Knowl notify to the query card what changed since the last query. Eg: 'KNOWL CHANGED: 3 items since you last looked' so they know to re-read and decide.
Open-source version at: https://github.com/dat999zx/knowl
The number is FactConsolidation single-hop at 262K context on MemoryAgentBench. On multi-hop Knowl scored 0.07 against an all-time ceiling of 0.14.
Write-up of the approaches that failed first: https://blog.knowl.cloud/the-story-of-knowl
About the sync about 2 different sessions or even agents/subagents, Knowl notify to the query card what changed since the last query. Eg: 'KNOWL CHANGED: 3 items since you last looked' so they know to re-read and decide.