Midas

Local-first, eval-first memory for long-horizon AI agents — no LLM at ingest.

Midas is a small Python SDK (and an MCP server) that gives AI agents durable memory across long, multi-session work — coding agents, research agents, assistants — without sending every turn through an LLM to "extract" facts. It runs on your machine, costs nothing per message, and every recalled memory is traceable to its source.

• No LLM at ingest or query → $0 API spend, zero data egress, fast local ops (no per-turn network round-trip; ingest is embed-bound, ~tens of ms).
• Auditable provenance → recall returns the source turns, not LLM-rewritten facts.
• Stays current and bounded → belief revision, selective forgetting + tiers, dedup — all no-LLM.
• Embeddable + store-agnostic → a library, not a SaaS. Bring your own embedder/store.
• Eval-first → every claim has a reproducible benchmark (BENCHMARKS.md).

Status: early. The API may change. Built narrow and measured-first.

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How it works (in plain English)

Your AI assistant forgets everything between sessions — every new chat starts from zero. Midas is a memory that lives next to your AI, on your computer. It does four simple things:

1. Notices what matters. As you work, Midas saves the durable stuff — a decision, a fact about you, a preference, a deadline — and ignores small talk. It judges "does this matter?" by reading the words (names, numbers, dates make a turn important) — without calling another AI.
2. Hands the right notes back. Before the AI answers, Midas finds the handful of past notes related to your question — by meaning, not exact keywords — and slips them into the prompt.
3. Keeps the notebook honest and tidy. When something changes ("actually, use Postgres now") it updates the old note instead of keeping both; it merges duplicates; and it forgets old, unimportant trivia so memory never bloats.
4. Stays yours. Everything is a local file — no cloud, no per-message AI bill — and every note links back to the exact moment it came from, so you can always check why the AI "knows" something.

The trick that makes it cheap, private, and local: Midas never sends your conversation to an AI to "process" it. It uses fast local math (embeddings — turning text into vectors and comparing them). The only AI involved is the one you're already talking to.

Why "no LLM at ingest" matters: other memory tools call an LLM to summarize every session — you pay in tokens forever, in latency, and by sending every turn to a provider. Midas trades that for cheap, local, auditable retrieval.

See it remember across sessions — session 1 stores decisions; a fresh session 2 recalls them by meaning:

_{Claude Code-style demo — the recalled lines (in green) are the real output Midas returned across two separate processes sharing one on-disk store.}

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Install

You need Python 3.11+. Check with python --version (or python3 --version). If you don't have it: python.org/downloads, or winget install Python.Python.3.12 (Windows) · brew install python@3.12 (macOS) · your package manager (Linux). The easiest installer for everything below is uv (one line: see its site), but pip/pipx work too.

A) To plug Midas into an AI tool (Claude Code, Cursor, …) — install the midas-mcp command

This puts a midas-mcp program on your PATH that any MCP client can launch — one line, no clone:

uv tool install "midas-memory[mcp,local]"     # recommended (Windows, macOS, Linux)
# …or:  pipx install "midas-memory[mcp,local]"

Where the command lands (you'll need this path for some clients):

OS	midas-mcp location	Find it with
Linux / macOS	~/.local/bin/midas-mcp	which midas-mcp
Windows	%USERPROFILE%\.local\bin\midas-mcp.exe	where midas-mcp

B) To use Midas as a Python library

pip install "midas-memory[all]"     # SDK + local embeddings + MCP + LangGraph
# smaller: `pip install midas-memory` (core, zero deps) · `"…[local]"` (embeddings) · `"…[mcp]"`

(Want the source / to contribute? git clone https://github.com/vornicx/Midas && cd Midas && pip install -e ".[all,dev]".)

First run downloads the embedding model once (~90 MB, bge-base ONNX), then works fully offline. No API key, ever.

Verify:

which midas-mcp || where midas-mcp                       # the server command is installed
python -c "import midas; print('Midas', midas.__version__, 'OK')"
python quickstart.py                                     # tiny end-to-end demo: remember → recall

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Connect it to your coding agent

Midas is a standard MCP server. Every MCP client launches the same command — midas-mcp — and passes a few environment variables. The only thing that differs between tools is where you put the config. Use this block everywhere (swap in your real home path):

{
  "mcpServers": {
    "midas": {
      "command": "midas-mcp",
      "env": {
        "MIDAS_MCP_EMBEDDER": "local",
        "MIDAS_MCP_DB": "/home/you/.midas/memory.sqlite3",
        "MIDAS_MCP_MAX_RECORDS": "50000",
        "MIDAS_MCP_MIN_IMPORTANCE": "2"
      }
    }
  }
}

⚠️ The #1 gotcha: GUI apps don't share your terminal's PATH, so they may not find midas-mcp. If a client says "command not found", replace "command": "midas-mcp" with the absolute path from which midas-mcp (macOS/Linux) or where midas-mcp (Windows, e.g. "C:/Users/you/.local/bin/midas-mcp.exe" — use forward slashes or \\ in JSON). On Windows, write the DB path with forward slashes too: C:/Users/you/.midas/memory.sqlite3.

Claude Code

Use the CLI (no file editing) — this is the exact command, verified:

claude mcp add midas -s user \
  -e MIDAS_MCP_EMBEDDER=local \
  -e MIDAS_MCP_DB="$HOME/.midas/memory.sqlite3" \
  -e MIDAS_MCP_MAX_RECORDS=50000 \
  -e MIDAS_MCP_MIN_IMPORTANCE=2 \
  -- midas-mcp

claude mcp list        # → midas: midas-mcp - ✓ Connected

-s user = available in all your projects · -s project = writes a shareable .mcp.json in the repo · -s local = just you, this project. Remove with claude mcp remove midas -s user.

Cursor

Edit ~/.cursor/mcp.json (all projects) or .cursor/mcp.json (this project) and paste the JSON block above. Then Cursor → Settings → MCP should show midas. Restart Cursor after changing env.

Claude Desktop

Settings → Developer → Edit Config opens the file (or edit it directly):

OS	Path
macOS	~/Library/Application Support/Claude/claude_desktop_config.json
Windows	%APPDATA%\Claude\claude_desktop_config.json

Paste the JSON block, save, and restart Claude Desktop.

Codex CLI

Codex uses TOML, not JSON. Either run codex mcp add midas -- midas-mcp, or add this to ~/.codex/config.toml:

[mcp_servers.midas]
command = "midas-mcp"
args = []
env = { MIDAS_MCP_EMBEDDER = "local", MIDAS_MCP_DB = "/home/you/.midas/memory.sqlite3", MIDAS_MCP_MAX_RECORDS = "50000", MIDAS_MCP_MIN_IMPORTANCE = "2" }

Start a session and run /mcp to confirm it's connected.

Windsurf

Edit the config (Cascade → MCP icon → Configure opens it), paste the JSON block, refresh:

OS	Path
macOS / Linux	~/.codeium/windsurf/mcp_config.json
Windows	%USERPROFILE%\.codeium\windsurf\mcp_config.json

Anything else (VS Code, Cline, Zed, OpenAI Agents SDK…)

Same pattern: point it at command midas-mcp with those env vars (JSON clients reuse the block above).

What happens once it's connected

On connect, Midas injects a short memory policy into the agent (via the MCP instructions): recall relevant memory first, then capture durable facts / decisions / preferences / constraints / corrections as they come up. The agent captures freely; Midas decides what's actually kept — it scores importance (no LLM), drops trivia below MIDAS_MCP_MIN_IMPORTANCE and skips duplicates, and keeps memory bounded via MIDAS_MCP_MAX_RECORDS (forgetting low-value items, protecting durable facts). Restart the client (or run /mcp) after editing config so it picks up the server.

Tools it exposes: remember, capture (policy-gated auto-store), recall (source-traceable), build_context (budgeted prompt block), maintain (dedup + forgetting, returns a deletion audit), stats (counts + short/medium/long tiers), forget / forget_all. Env knobs: MIDAS_MCP_DB (persist to a SQLite file), MIDAS_MCP_EMBEDDER (local or hashing), MIDAS_MCP_MAX_RECORDS, MIDAS_MCP_MIN_IMPORTANCE.

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Use it from Python (the SDK)

from midas import Memory, LocalEmbedder, ContentImportance

# Real semantic memory, fully local. (Or just `Memory()` for a zero-setup offline hashing embedder.)
mem = Memory(embedder=LocalEmbedder(), importance_scorer=ContentImportance())

mem.remember("Decision: the primary database is PostgreSQL.", kind="constraint", importance=5)
mem.remember("The launch date moved to September 14.", kind="fact", importance=5)
mem.remember("haha yeah sounds good")  # filler — auto-scored low-importance, first to be forgotten

# Budgeted, prompt-ready context — highest-value first, dated, source-traceable:
print(mem.assemble("When do we launch?", token_budget=128))

# Or structured, ranked hits, each traceable to its source:
for hit in mem.recall("which database did we pick?", limit=3):
    print(f"{hit.score:.2f}  {hit.record.content}")

# Auto-capture: forward a turn; Midas keeps it only if it clears the relevance policy (no LLM).
mem.capture("My deploy key expires on 2027-03-01.", kind="fact")   # -> stored
mem.capture("lol ok cool")                                          # -> skipped (below the floor)

Staying current and bounded — the long-horizon core

A multi-day agent's memory must stay current (no stale beliefs) and bounded (can't grow forever):

from midas.nli import LocalNLI

# Belief revision — a turn that CONTRADICTS an old belief supersedes it (local NLI, not keywords):
mem = Memory(embedder=LocalEmbedder(), supersede=True, supersede_conversational=True, nli=LocalNLI())

mem.forget_decayed(max_records=50_000)      # evict lowest value (importance × recency); protects facts
mem.consolidate(similarity_threshold=0.95)  # collapse near-duplicate restatements (keeps provenance)
mem.tier(record)                            # 'short' (≤1d) | 'medium' (≤1w) | 'long'

Forgetting returns the removed ids as a deletion audit trail and never drops the durable tier (facts/preferences/constraints, high importance). Durable storage: Memory(store=SQLiteStore( "memory.db"), embedder=LocalEmbedder()) — a local file, no native extension.

Use with LangGraph

Back LangGraph's long-term memory with Midas (pip install ".[langgraph]"):

from midas.integrations.langgraph_store import MidasStore

store = MidasStore()  # offline by default; pass Memory(embedder=LocalEmbedder(), ...) for semantic
store.put(("user", "123"), "pref", {"text": "prefers dark mode and concise answers"})
hits = store.search(("user", "123"), query="ui preferences")

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Benchmarks

Midas leads on the reader-independent axes that isolate a memory layer's quality (full methodology + reproduce commands in BENCHMARKS.md):

	baseline (recency window)	Midas
Retrieval — LongMemEval-s recall@k (evidence buried among distractors, n=40)	0.03	0.95
Retrieval — LoCoMo recall@k (5 conversations, n=50)	0.02	0.85
Answer — LongMemEval-s correctness (reader = gpt-4.1-mini, n=40)	0.05	0.82
Ingest cost	—	0 LLM calls · $0 API · 0 data egress

We lead with retrieval and cost (deterministic, reader-independent) because end-to-end correctness on these benchmarks is dominated by the reader LLM, not the memory layer. Head-to-head, same reader: with gpt-4o, Midas scores 0.84 on LongMemEval-s — matching the LLM-ingest SOTA (Observational Memory) while doing no LLM at ingest — and on a ~500-session haystack (~4,944 turns) it assembles a bounded ~480-token context (recall@k 0.78), where keep-every-observation-in-context designs do not fit by construction. (Same-reader, within-harness comparison — not a leaderboard rank; see BENCHMARKS.md.)

The eval harness

eval/ (dev-only) runs Midas and competitors through LoCoMo / LongMemEval with deterministic recall@k, cost/latency instrumentation, an optional local-or-hosted LLM judge, and a retention/forgetting measure:

python -m eval.runner --dataset longmemeval --variant s --local --midas-no-rerank --max-questions 15
python -m eval.retention --dataset locomo --max-convs 1 --local --derive-importance

Design concept

docs/long-horizon-memory.md — the north-star: the 4 C's (Complete · Clean · Current · Calibrated), why multi-day accuracy is a belief-management problem, and the honest, measured state of each piece (including the open frontiers).

Layout

midas/      # the SDK (importable; zero core dependencies)
  memory.py       # Memory: remember / capture / recall / build_context · forget_decayed · consolidate · tier
  importance.py   # ContentImportance — no-LLM per-turn salience   ·   policy.py — MemoryPolicy + auto-memory prompt
  nli.py          # LocalNLI — local entailment/contradiction (belief revision + abstention)
  embeddings.py   # Hashing / Local (bge) / OpenAI · DiskCachedEmbedder · LocalReranker
  store.py · sqlite_store.py · ann.py   # in-memory cosine · persistent SQLite · IVF index
  mcp_server.py   # the MCP server
eval/       # dev-only benchmark harness (datasets · adapters · metrics · runner · retention)

License

MIT.