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Context Retrieval

rust/patcha/src/db/retrieval/

The retrieval layer is the primary read interface over the local store. It turns sqlite-vec records and the activity graph into human-readable text blocks for CLI output and MCP consumers. It never writes.

Vector-based retrieval (context.rs)

get_working_memory(store, minutes)

A compact, deduplicated summary of the last N minutes — the "what is the user doing right now" view.

  • Fetches recent events (with their vectors) since the cutoff
  • Runs cosine-similarity dedup to collapse near-identical consecutive events of the same type (e.g. repeated window-focus events)
  • Formats each event to one line: [HH:MM] type: detail
# Working memory (last 15m)
[14:32] terminal: git status
[14:33] browser: patcha docs | github.com
[14:35] git_commit: fix: collector dedup | collectors/accessibility.rs

get_recent_activity(store, hours)

Same pipeline as get_working_memory over a longer window (hours). Uses the same dedup threshold (working_memory_dedup_threshold).

search_activity(store, embedder, query, limit)

Semantic search over the full history:

  1. Embeds the query locally with the Embedder (BGE query prefix applied)
  2. Runs sqlite-vec nearest-neighbor search for the top results
  3. Optionally reranks candidates with the cross-encoder reranker
  4. Returns each result with its score and a formatted line
# Search results for "sqlite-vec setup"
[score=0.912 | 2026-08-01 11:04] terminal: cargo add sqlite-vec
[score=0.874 | 2026-08-01 11:07] browser: sqlite-vec docs | github.com

The underlying ranked search lives in search.rs (SemanticSearch), which also supports search_by_date_range.

Graph-based retrieval (graph_context.rs)

These functions answer structural and temporal questions using the activity knowledge graph rather than pure vector similarity:

  • get_activity_context(graph, app, time, direction, count) — what the user was doing right before/after a moment, anchored by app and/or time.
  • get_session(graph, app, time) — the full work session around a moment: every app and event between two idle gaps.
  • find_connected(...) — every event structurally connected to a specific file, project, url, or app.

Deduplication

Dedup operates per event type: for each incoming row, cosine similarity is computed against the last kept vector of that type; if it exceeds working_memory_dedup_threshold, the incoming row replaces the previous one. This keeps a burst of identical window/screen events from flooding the output.

Event line format

Each event type renders differently, for example:

Type Format
terminal the command (truncated)
browser title | domain
git_commit / git_stash commit message + a few changed files
screen / window app — window title
other raw content (truncated)

All of the above are surfaced to AI clients through the MCP server; the RAG layer that builds richer analysis on top is documented in rag.md.