The persistence stack
Five layers, each serving a different persistence need. Layer 1: Brain docs (per-project, deep architecture and conventions). Layer 2: project-timeline.md files (curated chronological narrative for cold-start in 30 seconds). Layer 3: per-project changelogs (rigorous append-only firehose). Layer 4: Memory (cross-conversation routing, pointer-only). Layer 5: SynthesisOS (operational state, live data, cross-project view).
The layers interact through a routing protocol: memory points to brain docs, brain docs contain architecture and conventions, project timelines hand any cold-starting session a 30-second narrative primer, the global changelog tracks what was done across all projects, and cadence cards show where each project is in its lifecycle.