---
title: "Architecture Overview"
description: "System components and data flow in Claude-Mem"
---

# Architecture Overview

## System Components

Claude-Mem operates as a Claude Code plugin with the following core components:

1. **Plugin Hooks** - Lifecycle events (Setup version-check + 5 lifecycle hooks: SessionStart, UserPromptSubmit, PreToolUse for `Read`, PostToolUse, Stop)
2. **Worker Service** - Express HTTP API on a per-user port; processes observations via the Claude Agent SDK (or Gemini / OpenRouter)
3. **Database Layer** - SQLite + FTS5 (and optional Chroma for semantic search)
4. **Search Tools** - HTTP API + the `mem-search` skill / MCP server for progressive disclosure search
5. **Viewer UI** - React-based real-time memory stream served by the worker

## Technology Stack

| Layer                  | Technology                                |
|------------------------|-------------------------------------------|
| **Language**           | TypeScript (ES2022, ESNext modules)       |
| **Runtime**            | Node.js 20+ and Bun ≥ 1.0                 |
| **Database**           | SQLite 3 with bun:sqlite driver           |
| **Vector Store**       | Chroma (optional, for semantic search)    |
| **HTTP Server**        | Express.js 5                              |
| **Real-time**          | Server-Sent Events (SSE)                  |
| **UI Framework**       | React + TypeScript                        |
| **AI SDK**             | @anthropic-ai/claude-agent-sdk (or Gemini / OpenRouter) |
| **Build Tool**         | esbuild (bundles TypeScript)              |
| **Process Manager**    | Bun                                       |
| **Testing**            | `bun test`                                 |

## Data Flow

### Memory Pipeline
```
Hook (stdin) → Database → Worker Service → SDK Processor → Database → Next Session Hook
```

1. **Input**: Claude Code sends tool execution data via stdin to hooks
2. **Storage**: Hooks write observations to SQLite database
3. **Processing**: Worker service reads observations, processes via SDK
4. **Output**: Processed summaries written back to database
5. **Retrieval**: Next session's context hook reads summaries from database

### Search Pipeline
```
User Query → MCP Tools Invoked → HTTP API → SessionSearch Service → FTS5 Database → Search Results → Claude
```

1. **User Query**: User asks naturally: "What bugs did we fix?"
2. **MCP Tools Invoked**: Claude recognizes intent and invokes MCP search tools
3. **HTTP API**: MCP tools call HTTP endpoint (e.g., `/api/search/observations`)
4. **SessionSearch**: Worker service queries FTS5 virtual tables
5. **Format**: Results formatted and returned via MCP
6. **Return**: Claude presents formatted results to user

Uses 3-layer progressive disclosure: search → timeline → get_observations

## Session Lifecycle

```
┌─────────────────────────────────────────────────────────────────┐
│ 0. Setup Hook Fires (version-check.js)                          │
│    Sub-100ms read of .install-version; on mismatch prints       │
│    "run: npx claude-mem repair" to stderr. Always exits 0.      │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│ 1. Session Starts → Worker-start, then Context Hook             │
│    Starts Bun worker if needed, injects context from previous   │
│    sessions (configurable observation count)                    │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│ 2. User Types Prompt → UserPromptSubmit Hook Fires              │
│    Creates session in database, saves raw user prompt for FTS5  │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│ 3. Claude Uses Tools → PostToolUse Hook Fires (100+ times)      │
│    Captures tool executions, sends to worker for AI compression │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│ 4. Worker Processes → Claude Agent SDK Analyzes                 │
│    Extracts structured learnings via iterative AI processing    │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│ 5. Claude Stops → Summary Hook Fires                            │
│    Generates final summary with request, completions, learnings │
└─────────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│ 6. Session Ends → Cleanup Hook Fires                            │
│    Marks session complete (graceful, not DELETE), ready for     │
│    next session context. Skips on /clear to preserve ongoing    │
└─────────────────────────────────────────────────────────────────┘
```

## Directory Structure

```
claude-mem/
├── src/
│   ├── hooks/                  # TypeScript hook implementations (built via esbuild)
│   ├── sdk/                    # Claude Agent SDK integration
│   ├── services/
│   │   ├── worker-service.ts   # Express HTTP + SSE service (worker entry point)
│   │   ├── sync/ChromaSync.ts  # Optional Chroma vector index
│   │   └── sqlite/             # SQLite + FTS5 storage layer
│   ├── ui/viewer/              # React + TypeScript web viewer
│   ├── shared/                 # Shared utilities (paths, settings defaults)
│   └── utils/                  # Logging, platform, tag-stripping helpers
│
├── scripts/                    # Build + utility scripts
│
├── plugin/                     # Plugin distribution (synced to marketplace)
│   ├── .claude-plugin/plugin.json
│   ├── hooks/hooks.json        # Hook registration (Setup + 5 lifecycle hooks)
│   ├── scripts/                # Built executables
│   │   ├── version-check.js    # Setup-phase marker check (sub-100ms)
│   │   ├── bun-runner.js       # Resolves Bun and runs worker-service.cjs
│   │   ├── worker-service.cjs  # Worker daemon + lifecycle hook dispatcher
│   │   ├── worker-cli.js       # CLI shim
│   │   ├── worker-wrapper.cjs  # Process wrapper
│   │   ├── mcp-server.cjs      # MCP search server
│   │   ├── statusline-counts.js
│   │   └── context-generator.cjs
│   ├── skills/                 # Agent skills (mem-search, make-plan, do, etc.)
│   └── ui/viewer.html          # Self-contained React bundle
│
├── tests/                      # Test suite (`bun test`)
├── docs/                       # Mintlify documentation
└── openclaw/                   # OpenClaw integration plugin
```

## Component Details

### 1. Plugin Hooks

The plugin registers a Setup-phase `version-check.js` plus five lifecycle hooks. Each lifecycle event invokes `bun-runner.js` to spawn `worker-service.cjs` with a `hook claude-code <event>` argument; the worker process is the single dispatcher for all hook logic. Events:

- **Setup** → `version-check.js` (sub-100ms marker check; never installs anything)
- **SessionStart** → start worker, then `hook claude-code context` (context injection)
- **UserPromptSubmit** → `hook claude-code session-init`
- **PreToolUse** (matcher `Read`) → `hook claude-code file-context`
- **PostToolUse** (matcher `*`) → `hook claude-code observation`
- **Stop** → `hook claude-code summarize` (summary generation)

The actual runtime install (Bun, uv, `bun install`) is performed by `npx claude-mem install` / `npx claude-mem repair` with a visible installer spinner; the Setup hook itself only reads the `.install-version` marker.

See [Plugin Hooks](/architecture/hooks) for detailed hook documentation.

### 2. Worker Service
Express.js HTTP server on a per-user port (default `37700 + (uid % 100)`, override via `CLAUDE_MEM_WORKER_PORT`) with:
- Search HTTP API endpoints
- Viewer UI HTTP/SSE endpoints
- Async observation processing via the Claude Agent SDK (or Gemini / OpenRouter)
- Real-time updates via Server-Sent Events
- Auto-managed by Bun

See [Worker Service](/architecture/worker-service) for HTTP API and endpoints.

### 3. Database Layer
SQLite3 with bun:sqlite driver featuring:
- FTS5 virtual tables for full-text search
- SessionStore for CRUD operations
- SessionSearch for FTS5 queries
- Location: `~/.claude-mem/claude-mem.db`

See [Database Architecture](/architecture/database) for schema and FTS5 search.

### 4. mem-search Skill (v5.4.0+)
Skill-based search with progressive disclosure providing 10 search operations:
- Search observations, sessions, prompts (full-text FTS5)
- Filter by type, concept, file
- Get recent context, timeline, timeline by query
- API help documentation

**Token Savings**: ~2,250 tokens per session vs MCP approach
- Skill frontmatter: ~250 tokens (loaded at session start)
- Full instructions: ~2,500 tokens (loaded on-demand when invoked)
- HTTP API endpoints instead of MCP tools

**Skill Enhancement (v5.5.0)**: Renamed from "search" to "mem-search" for better scope differentiation. Effectiveness increased from 67% to 100% with enhanced triggers and comprehensive documentation.

See [Search Architecture](/architecture/search-architecture) for technical details and examples.

### 5. Viewer UI
React + TypeScript web interface served by the worker on its configured port (default `http://127.0.0.1:<worker-port>`) featuring:
- Real-time memory stream via Server-Sent Events
- Infinite scroll pagination with automatic deduplication
- Project filtering and settings persistence
- GPU-accelerated animations
- Self-contained HTML bundle (viewer.html)

Built with esbuild into a single file deployment.