rekal 1.4.0

Long-term memory MCP server for LLMs — hybrid search in a single SQLite file

rekal

Long-term memory for LLMs. One SQLite file, no cloud, no API keys.

You tell your LLM you prefer Ruff, that deploys go through tags, that the auth service lives in services/auth. Next conversation, blank slate. You repeat yourself. Again. Forever.

rekal is an MCP server that gives LLMs persistent memory. It stores what matters and retrieves it later using hybrid search (BM25 keywords + vector similarity + recency decay). Embeddings run locally via fastembed. Nothing leaves your machine.

pip install rekal

Requires Python 3.11+.

Setup

1. Install and add the MCP server

pip install rekal

Then add rekal to your MCP client:

claude mcp add rekal -- rekal

For other MCP clients, add to your config JSON:

{
  "mcpServers": {
    "rekal": {
      "command": "rekal"
    }
  }
}

On first run, rekal creates ~/.rekal/memory.db. That single file holds everything. Copy it to back up, drop it to start fresh.

2. (Optional) Claude Code skills

If you use Claude Code, rekal ships as a plugin with two skills for automated memory management. The plugin talks to the MCP server from step 1, so install that first.

/plugin marketplace add janbjorge/rekal
/plugin install rekal-skills@rekal

Skill	Trigger	What it does
rekal-save	Auto on session end, or /rekal-save	Reviews the conversation, deduplicates against existing memories, stores what's worth keeping
rekal-hygiene	/rekal-hygiene	Finds conflicts, duplicates, and stale data. Proposes fixes for your approval, never deletes on its own

How it works

Your LLM stores things worth remembering:

User: "I prefer Ruff over Black for formatting"
LLM:  → memory_store("User prefers Ruff over Black", type="preference")

Weeks later, different conversation:

User: "Set up linting for my new project"
LLM:  → memory_search("formatting linting preferences")
      ← "User prefers Ruff over Black" (score: 0.92)

When facts change, old versions stay linked:

LLM: → memory_supersede(old_id="mem_abc", new_content="API moved from v2 to v3")

When things contradict each other:

LLM: → memory_conflicts(project="backend")
     ← "use PostgreSQL for everything" contradicts "migrate analytics to ClickHouse"

Search

Three signals, blended into one score:

score = 0.4 · BM25(keyword match)
      + 0.4 · cosine(semantic similarity)
      + 0.2 · exp(-t/half_life)

"deploy auth" and "shipping the login system to pre-prod" both find the same memory. Recent stuff ranks higher, but old memories still surface when relevant.

Tools

16 tools over MCP:

Core

Tool	Description
memory_store	Store a memory with type, project, tags, and conversation scope
memory_search	Hybrid search: BM25 + vector + recency in one query
memory_update	Update content, tags, or type (re-embeds automatically)
memory_delete	Delete a memory by ID

Smart write

Tool	Description
memory_supersede	Replace a memory while keeping the old one as history
memory_link	Link memories: supersedes, contradicts, related_to
memory_build_context	Relevant memories + conflicts + timeline for a query, in one call

Introspection

Tool	Description
memory_similar	Find memories similar to a given one
memory_topics	Topic summary grouped by type
memory_timeline	Chronological view with optional date range filters
memory_related	All links to and from a memory
memory_health	Database stats: counts by type, project, date range
memory_conflicts	Find memories that contradict each other

Conversations

Tool	Description
conversation_start	Start a conversation, optionally linked to a previous one
conversation_tree	Get the full conversation DAG
conversation_threads	List recent conversations with memory counts
conversation_stale	Find inactive conversations

Memory types

Type	For	Example
fact	Things that are true	"The API rate limit is 1000 req/min"
preference	How you like things	"Prefers dataclasses over hand-written __init__"
procedure	Steps to do something	"Deploy: git tag vX.Y.Z && git push --tags"
context	Current state	"Currently rewriting the payment service"
episode	Things that happened	"Debugged the OOM, root cause was unbounded cache"

Architecture

One SQLite file, four components:

rekal
  │
  SQLite ──┬── FTS5 index ──── keyword relevance (BM25)
           ├── sqlite-vec ──── semantic similarity (384d vectors)
           ├── recency ─────── exponential decay (30-day half-life)
           └── memory links ── supersedes / contradicts / related_to

Conversations form a DAG (follow-ups, branches, merges), navigable like a git log.

CLI

rekal serve    # Run as MCP server (default)
rekal health   # Database health report
rekal export   # Export all memories as JSON

License

MIT