Written for AI coding agents, and equally readable by a human contributor. Short on purpose.
The extracted memory layer of a personal second-brain agent setup: vector retrieval for entry
points, hand-curated [[wikilinks]] for association, a cross-encoder rerank, and SQLite for the
only two things worth persisting — a per-turn ledger and A/B telemetry.
Status: pilot. It runs daily in one real setup and it is deliberately minimal. It is not a framework and should not grow into one. The interesting claim here is what it does not need: no graph database, no ETL, no entity-extraction pass.
- Python + SQLite (stdlib driver).
requirements.txtcovers the embedding/rerank models only. index_notes.py— chunk + embed a markdown folder (e5-base) into a.npy/.pklindex.brain_ask.py— the recall pipeline: dense retrieve → optional--graph1-hop wikilink expansion → cross-encoder rerank → top-12.--abruns vector-only and vector+graph, diffs them, and logs the delta to SQLite.turnstate_hook.py— agent Stop-hook; appends one row per assistant turn. Zero tokens, pure stdlib.turnstate_show.pyis the read-only viewer.eval/build_gold.py+eval/run_eval.py— the retrieval ruler: a gold set built from the vault's own[[wikilinks]](four question classes), scored in both modes as Recall@12 / MRR / nDCG@12.run_eval.pyimportsbrain_ask.pyrather than re-implementing it, so the eval and the agent cannot drift apart.schema.sql— documents both tables (turns,ab_recall);run_eval.py --sqliteadds a third,gold_eval, one row per class and mode per run.examples/claude-code-stop-hook.json— how the hook gets wired.
Start with pytest -q — the suite needs no model download and no network. Then run the thing
you changed and paste the output:
pytest -q # file rules, entity gate, link parsing, eval metrics
python index_notes.py <folder-of-markdown> # build an index over a small sample
python brain_ask.py "<question>" --graph # recall, with graph expansion
python brain_ask.py "<question>" --ab # both arms + the logged delta
python turnstate_show.py # what the ledger capturedIf you touch retrieval, numbers are not optional. Build a gold set once, keep the file, and show the table before and after your change:
python eval/build_gold.py <folder-of-markdown> --n-per-class 60
python eval/run_eval.py --gold eval/gold-<date>.jsonl # before
python eval/run_eval.py --gold eval/gold-<date>.jsonl # afterSame gold file both times: rebuilding it between runs makes the two tables incomparable. A
regression worse than 0.01 nDCG@12 on any class is a reason to revert, not to explain. And if you
touch eval/ itself, prove the ruler still bites: EVAL_MUTANT=1 pytest tests/test_eval.py must
FAIL.
Use a synthetic notes folder — five or six files with a couple of [[wikilinks]] between them
is enough to show a behaviour change. Never paste real notes into an issue or PR.
If you touch retrieval, --ab is the honest way to show your change helps: it produces a measured
delta, not an opinion.
- The graph is not materialized in SQL. Edges are parsed from the notes at query time, bounded to 1 hop and 40 neighbours. That keeps the graph in sync with the notes at zero maintenance cost. Materializing an edge table is a real option — but only when hop depth or corpus size demands it, and with the measurement that shows it.
- The turn ledger costs zero tokens. Anything that puts a model call in the hook path is rejected on principle: it runs after every turn.
- Stdlib and boring SQL. One file, no ORM, no migrations framework.
- The indexer must ignore what is not a note: editor state, sync-conflict copies, versioned backups. Silently indexing five copies of one file is a bug we have already had.
- Turning the pilot into a framework — plugin systems, abstraction layers, a config format. Open an issue; the answer is usually "not yet, and here is why".
- Changing the embedding or reranker model. It invalidates every existing index; needs a measured before/after and a note in the README.
- Schema changes to
turnsorab_recall— existing data lives in those tables.
Your copyright stays yours, there is no CLA, and issues labelled accepted are free to take —
comment "claiming this". Full terms:
CONTRIBUTING.md.
If an AI wrote your change, say so in the PR and confirm you ran it. Welcome here — we do it daily. Unread generated code is the one thing that gets closed on sight.