michael-denyer/memory-mcp

Give your AI assistant a persistent second brain
**Stop re-explaining your project every session.**
Memory MCP learns what matters and keeps it ready — instant recall for the stuff you use most, semantic search for everything else.
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The Problem
Every new chat starts from scratch. You explain your architecture *again*. You paste the same patterns *again*. Your context window bloats with repetition.
Other memory solutions help, but they still require tool calls for every lookup — adding latency and eating into Claude's thinking budget.
**Memory MCP fixes this with a two-tier architecture:**
1. **Hot cache (0ms)** — Frequently-used knowledge printed into context by the plugin's SessionStart and UserPromptSubmit hooks *before Claude even starts thinking*. Claude Code adds a hook's stdout to the conversation, so no tool call is needed.
2. **Cold storage (~50ms)** — Everything else, searchable by meaning via semantic similarity.
The system learns what you use and promotes it automatically. Your most valuable knowledge becomes instantly available. No manual curation required.
Before & After
| 😤 Without Memory MCP | 🎯 With Memory MCP |
|----------------------|-------------------|
| "Let me explain our architecture again..." | Project facts persist and isolate per repo |
| Copy-paste the same patterns every session | Patterns auto-promoted to instant access |
| 500k+ token context windows | Hot cache keeps it lean (~20 items) |
| Tool call latency on every memory lookup | Hot cache: **0ms** — a hook already put it in context |
| Stale information lingers forever | Trust scoring demotes outdated facts |
| Flat list of disconnected facts | Knowledge graph connects related concepts |
Install
The plugin gives you auto-configured hooks and slash commands. Embeddings run on sentence-transformers on every platform, including Apple Silicon.
Manual config (no plugin)
Add to ~/.claude.json:
See Reference for full configuration options.
Restart Claude Code. Run memory-mcp-cli bootstrap once to seed memories from your project docs; the hooks inject whatever is promoted, but nothing seeds itself.
> **First run**: Embedding model (~90MB) downloads automatically. Takes 30-60 seconds once.
How It Works
The **hot cache** (~10 items) reaches Claude through two plugin hooks. SessionStart runs memory-mcp-cli hot-cache --force and UserPromptSubmit runs memory-mcp-cli hot-cache, and Claude Code adds each command's stdout to the conversation. The command prints only when the text differs from what the session last saw, which is cheap while the set is stable and reprints in full when it shifts. The set combines recent recalls, predicted next memories, and top promoted items. **Promoted memories** (~20 items) is the backing store of frequently-used memories. Memories used 3+ times auto-promote; unused ones demote after 14 days.
What Makes It Different
Most memory systems make you pay a tool-call tax on every lookup. Memory MCP's **hot cache bypasses this entirely** — a hook prints your most-used knowledge into the conversation before Claude starts thinking.