6. Cache strategy for collectors

Date: 2026-04-22

Status

Accepted

Context

Collectors (git, opencode, todos) can be expensive. We need to avoid re-running them on every build.

Decision

We will use file-based caching:

• Cache stored in cache.json in system cache directory
• Each entry tracks: opencode_last_query, git_last_scan, todo_last_scan
• --fresh flag bypasses cache entirely
• --project <name> limits to specific project

Cache Invalidation

Cache is invalidated by:

1. --fresh flag (user override)
2. cache_ttl_hours setting in config.toml
3. Manual cerebro status shows cache status

Consequences

Pros

• Fast subsequent builds
• Respects user intent

Cons

• Stale data if TTL too long
• System cache dependency

Notes

See cache.rs for implementation.