Memory model
The five-tier memory hierarchy and the composite scoring formula used for recall.
The Project Brain's memory is organized in five tiers. Each tier has a different lifetime, access pattern, and ranking weight. When the agent answers a question, it retrieves from all tiers in parallel and merges results with a composite score.
Five-tier hierarchy
| Tier | Lifetime | Holds |
|---|---|---|
| 1. Working | Per-run | The current prompt, tool calls, and intermediate steps. |
| 2. Session | Hours | Conversation history within a single chat session. |
| 3. Project | Project lifetime | Indexed documents, releases, and structured project facts. |
| 4. Org | Org lifetime | Shared team-wide policies and templates (read-only at the project tier). |
| 5. Archive | Indefinite | Cold storage of older runs, evicted from hot recall but searchable. |
Composite scoring
The retriever ranks each candidate memory with a weighted blend of semantic similarity, recency, and tier priority. The default formula:
score = 0.55 * cosine_sim
+ 0.25 * recency_decay(half_life = 30d)
+ 0.15 * tier_weight
+ 0.05 * pin_boosttier_weightrewards higher tiers (Working > Session > Project), pin_boost applies to memories explicitly pinned by a user, and recency_decay uses a 30-day half-life so old knowledge fades unless it is also semantically relevant.
Tuning
Org admins can adjust the weights from Settings → Agent → Memory. The default values are the result of internal evals on changelog generation and proposal writing — start there and only tune if you have a measured reason.