Project memory for coding agents. memlab gives Claude Code, Cursor or any MCP client two things a plain vector index gets wrong: the code a change actually touches, and the decisions behind it. It builds a symbol graph of your repository, ranks code with graph-aware retrieval, keeps ADRs and postmortems in their own channel, and draws the whole project as an interactive map.

• Measured, not claimed. On ten evaluation sets from four real repositories memlab finds the right files more often than graphify on every set, and retrieves past decisions where both graphify and AMG return almost nothing (benchmarks). Every hypothesis was committed with its criteria before its run.
• Local. Code and docs never leave your machine: regex-based chunking, BM25, and two small open embedding models (CUDA if you have it, CPU otherwise). No LLM calls at index or query time.
• Two tools, not one blend. Mixing code and decisions into one ranking lost in every experiment; the agent asks for the kind of context it needs.

_{The Hono codebase in memlab's graph.html: 23 subsystems, hubs sized by links.}

Quick start

pip install git+https://github.com/sattva2020/memlab      # Python 3.11+
cd /path/to/repo
memlab explore all --root .        # -> ~/.memlab/out/<repo>/graph.html and REPORT.md

For a GPU, install the CUDA build of PyTorch first (pip otherwise brings the CPU one); memlab uses CUDA when it is there, Apple's GPU (MPS) on a Mac, and the CPU otherwise. The re-ranker runs on CUDA only. On macOS and Linux the interpreter is often python3: use it wherever this page says python.

Connect it to your agent — add to the repository's .mcp.json:

{
  "mcpServers": {
    "memlab": { "type": "stdio", "command": "memlab", "args": ["serve", "--root", "."] }
  }
}

Claude Code plugin

The repository is also a Claude Code plugin: the MCP server, session hooks and three commands in one install.

/plugin marketplace add sattva2020/memlab
/plugin install memlab@memlab

At install it asks for the Python interpreter (required); point it at the one you installed memlab's dependencies into (pip install numpy scipy networkx sentence-transformers). You get:

• /memlab:status — which tree is indexed, errors, decision notes at risk, a live search check
• /memlab:recall <topic> — prior decisions and the relevant code, with path:line sources
• /memlab:note — drafts this session's decisions as docs/notes/, written after you pick
• hooks: the newest decision records at session start (and, in a git worktree, a reminder to pass the worktree as root), a one-line hint on long prompts when memlab has not been used, and at session end logs/usage.jsonl: per search, the shown files the session then edited

Caches and logs go to the plugin's data folder. Do not also keep the .mcp.json entry above, or two servers start.

In git worktree sessions of the Claude desktop app the server indexes the main checkout. The memlab-root mod (Claude Code 2.1.287+) adds the session's worktree as root to every memlab call and shows a status line; it works with the plugin or with the .mcp.json setup:

/plugin install memlab-root@memlab

No config file is needed. memlab reads the Dart package from pubspec.yaml and import aliases from tsconfig.json, skips lockfiles and generated code, and treats docs/adr/, docs/decisions/, docs/postmortems/ and docs/notes/ as decision memory. To change any of that, put the section into .memlab.toml at the repository root (see projects/example.toml).

The two embedding models and the re-ranker (about 2.6 GB of VRAM together) are loaded once per machine, in a small background process on 127.0.0.1 that every session shares and that exits after 30 idle minutes. Without a GPU there is no re-ranking; MEMLAB_RERANK=0 turns it off. Caches and the call journal (logs/calls.jsonl) live in ~/.memlab (set MEMLAB_HOME to move them).

Keep it fresh after every commit (runs in the background, never blocks a commit):

memlab hook-install --root /path/to/repo

Without the plugin, memlab hook-install --claude adds the session hooks to ~/.claude/settings.json and a short block to ~/.claude/CLAUDE.md between <!-- memlab:begin --> and <!-- memlab:end -->: memlab as the first source for project knowledge, where decisions go, worktree root. Re-running replaces only that block.

What you get

	What it does
search_code	Files, classes and functions relevant to a task, with path:line. Code only; on a GPU the top 50 are re-ordered by a multilingual cross-encoder, so a question in Russian finds English code.
search_decisions	ADRs, postmortems and session notes that explain why — one best passage per document.
add_note	Records a decision as a new file in docs/notes/ (never edits one, so worktrees merge cleanly); searchable at once.
explain	A symbol or file: where it is defined, who uses it, what it uses, linked docs and decisions.
find_path	The shortest chain of imports and symbol references between two files or symbols.
graph.html	One self-contained page: subsystems (Louvain), search, click a file for its symbols and neighbours, deep links (graph.html#src/hono.ts).
REPORT.md	Hubs, subsystems, surprising cross-folder links, hubs no document explains.
post-commit hook	Rebuilds the views and warms the index; only changed chunks are re-embedded.

_{Click a file: its symbols, and every file it imports or shares a symbol with — and through which name.}

How it works

flowchart LR
  Q[query] --> B[BM25<br/>query stopwords removed]
  Q --> D[dense<br/>multilingual-e5-small]
  B --> F[RRF fusion]
  D --> F
  F --> S[seeds<br/>one per symbol + best hit per term]
  S --> P[Personalized PageRank<br/>over symbol references<br/>hubs blocked as transit]
  P --> C[search_code<br/>code chunks to budget]
  Q --> Q3[dense<br/>Qwen3-Embedding-0.6B] --> DEC[search_decisions<br/>ADRs, postmortems, notes]

Loading

• Chunks are cut at top-level declarations (code) and headings (markdown).
• Edges come from the source, no LLM: Dart and TS/JS imports, markdown links and backticked paths, and symbol references — a chunk that mentions a name defined elsewhere. Names defined in more than 3 places or mentioned in more than 200 chunks are dropped (they are noise).
• Hubs don't leak: in PageRank, a node with very high degree keeps the mass it receives but does not pass it on — the fix that made the graph beat flat retrieval (H5 in the research log).

Benchmarks

Share of the right files in the top 5 results (files@5); ten sets, four repositories, the same cases for every system. graphify 0.9.70 with its semantic document pass (gpt-4.1-mini); AMG as deployed, run through its own retriever.

set	memlab	AMG	graphify
natural-language questions, Flutter app (48)	0.57	0.45	0.37
change → files, Flutter app (80)	0.59	0.28	0.29
change → files, NestJS/Next.js CRM (80)	0.57	0.09	0.08
change → files, Node bot (25)	0.30	0.01	0.40
change → files, TS indexer (22)	0.56	0.62	0.41
decisions, 5 sets (192)	0.93–1.00	0.00–0.04	0.00–0.05

memlab is ahead of graphify on all ten sets by the pre-registered rule (not significantly worse anywhere, significantly better somewhere; paired bootstrap, 95% CI) — including the Node bot, where graphify leads at files@5 but memlab leads at files@10 and @20. Full tables, token-budget results, the failed hypotheses and the caveats: docs/RESEARCH.md.

The evaluation sets are mined from private repositories (commit subjects → changed files, and decision questions written blind by separate agents), so they are not published; memlab cases-from-git builds the same kind of set from any repository.

Commands

python -m memlab serve   --config C --root R                 # MCP server (stdio)
python -m memlab explore all|html|report --config C --root R # graph.html + REPORT.md
python -m memlab explore explain NAME    --config C --root R
python -m memlab explore path A B        --config C --root R
python -m memlab hook-install --config C --root R            # post-commit refresh
python -m memlab warm    --config C --root R                 # build the index once
python -m memlab cases-from-git --config C --out cases.json  # evaluation cases from history
python -m memlab eval    --config C --cases cases.json --methods "hybrid,only:code:ppr:refs:transit=1&seeds=gfy"

Platforms

OS	Checked on	What runs	Last result
Windows 11	the author's machine (RTX 2070, CUDA)	tests, live MCP server in daily use	46 passed
Linux	python:3.11-slim container — scripts/ci-linux.sh user@docker-host	tests, claude plugin validate (plugin + mod)	46 passed, 3 valid (2026-10-09)
macOS	Codemagic mac_mini_m2 — codemagic.yaml, workflow macos-check	tests, plugin validation, one embedding asserting Apple GPU (mps)	46 passed, device: mps (2026-10-09)

GPU: CUDA on Windows/Linux, Apple's MPS on a Mac, the CPU otherwise; the re-ranker needs CUDA. The Linux and macOS checks run outside GitHub Actions: the script copies the working tree to any Docker host over ssh; the Codemagic workflow is started from its UI or API (POST /builds, workflow macos-check).

Limits

• Import resolution covers Dart and TypeScript/JavaScript; other languages (Python included) are linked only through symbol references, so their graphs are sparser.
• Tuned and evaluated on English and Russian text.
• The first index build takes about a minute on a mid-size repository (models load, every chunk is embedded once); later builds re-embed only what changed.

Research

memlab started as a replication-minded study of project memory for agents: does any structured memory beat a well-tuned flat hybrid retriever at a matched token budget? The answer is "sometimes, and here is exactly when" — ten stages, more than a dozen pre-registered hypotheses, results as they came out: docs/RESEARCH.md. Related work: docs/related-work.md.

License

Apache License 2.0. See NOTICE.