Ebb — an agent-first knowledge graph

Long-term memory for AI agents, built as a graph. Relevance is recency-weighted connection strength: reusing knowledge keeps it alive, unused knowledge decays and is archived, and nothing is deleted until a human signs off. Runs embedded (zero infra) or on Neo4j (production).

The two mechanisms it's built around — connection-weighted relevance and time-decay — are native graph operations, and both have deep prior art (PageRank/centrality; ACT-R base-level activation and spreading activation from cognitive science; spaced-repetition forgetting curves). This is a small, honest implementation of that lineage aimed specifically at agent memory.

Why it's built this way

1. The engine and the interface are separate. The graph store sits behind a small interface (GraphStore). Agents and the scoring logic never touch a specific database, so you can run the exact same graph on an embedded engine today and swap to Neo4j later with one env var.

2. Relevance is recency-weighted, not raw connection count. "More connections = more relevant" rewards old, heavily-referenced data forever — the exact stale-data problem the system is meant to kill. Here, every edge's contribution to relevance is multiplied by a time-decay factor keyed to when the connection was last reinforced. An edge reinforced yesterday counts near-full; one last touched six months ago counts for almost nothing. Reusing a connection (recall/reinforce) resets its clock — so relevance tracks what's actually live, and stale knowledge sinks on its own.

Proof, from the demo seed graph (python -m ebb.demo):

node                             raw#   activation
decision:outcome-pricing            3        6.116   <- fresh, few links, ranks #1
decision:seat-pricing              11        3.077   <- MOST links, ranks #3
...
note:analysis-* (x10)               1        0.051   <- decayed -> archived (tier 4)

The superseded per-seat decision has the highest raw connection count in the graph and still ranks third, behind a fresh decision with a third as many links. Raw count lost; recency won.

Related MCP server: Memory Engine MCP

What's in it

• Graph model — every note, decision, meeting, person, client, fact is a node; every reference is a timestamped, typed, weighted edge.

• Scoring engine (scoring.py) — recency-weighted activation, exponential decay (configurable half-life), one hop of spreading activation (a portable stand-in for PageRank), and tier assignment. Pure functions, fully unit-tested.

• Four archive tiers — 1 hot (default recall) · 2 warm (deeper recall) · 3 cold (archived, on-demand only) · 4 frozen (pending human sign-off before deletion). Pinned nodes never auto-archive.

• MCP server (mcp_server.py) — the agent interface: remember, recall, connect, reinforce, forget, neighbors, pin, maintain, review_queue, stats.

• Two backends — KuzuStore (embedded, default) and Neo4jStore (production), same interface, same Cypher shapes.

Quickstart (embedded — zero infra)

python -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt

python -m ebb.demo      # narrated end-to-end walkthrough
pytest -q                 # 11 tests, all green

No Docker, no server, no ports. Kùzu is an in-process graph database, so the Ebb is just a folder (./ebb_db).

Plug it into an MCP client (e.g. Claude Desktop)

1. Copy the ebb block from claude_desktop_config.example.json into your client's MCP config, fixing the absolute paths.

2. Restart the client. The ebb tools appear in the tools menu.

3. The agent can now remember things across sessions, recall what's relevant, and reinforce what it keeps using — with decay and archival handled for it.

Production mode (Neo4j)

docker compose up -d      # Neo4j + Graph Data Science + APOC
EBB_BACKEND=neo4j NEO4J_PASSWORD=brainbrain python -m ebb.demo

Same code, same behavior. On Neo4j you additionally get the GDS library, so the spreading-activation pass in scoring.py can graduate to real PageRank / centrality / community detection when scale demands it. (The Neo4j backend's Cypher mirrors the fully-tested Kùzu backend; run pytest against a live instance before trusting it in prod.)

The model, briefly

Activation of a node = Σ (edge.weight × decay(age_since_last_reinforced)) + read-recency-bonus, plus one damped hop of the same from its neighbours. Decay is a half-life (default 30 days, tunable). Tiers are cut on the activation normalised against the most-active non-pinned node. recall blends this activation with query text-match and returns why each result surfaced. Everything is tunable in one place — ebb/scoring.py::Config.

Writing an ingestion adapter

Ebb is source-agnostic: anything that calls remember/connect can feed it. A source (a notes folder, a wiki, an issue tracker) becomes a graph by mapping documents to nodes, links/mentions to edges, and an edit timestamp to the recency clock. Keep adapters and their data out of the repo.

Layout

src/ebb/
  model.py        # Node, Edge, tiers
  scoring.py      # decay, activation, spreading, tiering  <- the core
  store.py        # GraphStore interface
  kuzu_store.py   # embedded backend (default)
  neo4j_store.py  # production backend
  engine.py       # Brain: remember/recall/connect/reinforce/maintain/...
  mcp_server.py   # agent-facing MCP tools
  seed.py         # fictional demo graph
  demo.py         # narrated walkthrough
tests/            # 11 tests: scoring + end-to-end
docker-compose.yml

License

MIT — see LICENSE.