PrunePolicy behavior, backend support, test coverage, and implementation boundaries.

Memory Pruning And Tests

MemoryStore includes an optional prune method. The default trait implementation is a no-op for compatibility, while shipped stores implement real pruning.

PrunePolicy

use a3s_memory::PrunePolicy;

let policy = PrunePolicy {
    max_age_days: 90,
    min_importance_to_keep: 0.5,
    max_items: 1000,
};

Field	Default	Meaning
`max_age_days`	`90`	Age threshold for stale memory.
`min_importance_to_keep`	`0.5`	Items at or above this importance are protected from age-based deletion.
`max_items`	`0`	Hard cap after age pruning. `0` means unlimited.

Algorithm

Pruning has two phases:

Delete items that are both older than max_age_days and below min_importance_to_keep.
If max_items is greater than zero and the store is still over the cap, delete lower-ranked items until the cap is met.

InMemoryStore and FileMemoryStore use relevance ordering for the cap phase. SqliteMemoryStore keeps higher-importance and newer rows when applying the hard cap.

Store Support

Store	Pruning support
`InMemoryStore`	Removes stale low-importance items and enforces `max_items` in memory.
`FileMemoryStore`	Removes stale item files, updates `index.json`, and enforces `max_items`.
`SqliteMemoryStore`	Deletes stale rows from SQLite and enforces `max_items` with SQL.
Custom store	Gets the no-op default unless it overrides `prune`.

Tests

The repository includes:

Area	Covered behavior
Contract tests	Store, retrieve, missing retrieval, content search, case-insensitive search, search limits, tag search, recent items, important items, delete, clear, count, and relevance ordering across `InMemoryStore` and `FileMemoryStore`.
File store tests	Persistence across instances, index rebuild after `index.json` removal, and path traversal prevention for memory IDs.
Memory item tests	Builder chain, tag replacement, importance clamping, memory type, access recording, metadata, and object-safe `Arc<dyn MemoryStore>` usage.
Relevance tests	Custom weights and old-item decay behavior.
SQLite tests	Store/retrieve, FTS search, tag search, session-log roundtrip, Markdown export for important and episodic items, persistence, delete, clear, count, and pruning.

Tests exercise the public storage contract and feature-gated SQLite backend. They do not validate A3S Code prompt injection, session memory tiering, or external vector embedding quality because those are outside a3s-memory.

Operational Notes

Pruning is explicit; the store does not run a background retention task.
High-importance old memories are protected from age pruning.
max_items is a hard storage cap and can remove otherwise valid memories.
For SqliteMemoryStore, Markdown files are append-only review artifacts and are not pruned when database rows are deleted.

Pruning And Tests