Knowledge Graph MCP Server

繁體中文 | English

Long-term memory system for AI agents. Enables agents to accumulate domain expertise through mentorship or professional practice, automatically recall relevant knowledge, and grow from apprentice to independent expert.

Works with any domain requiring continuous learning + knowledge evolution: software engineering, music production, design, medical diagnosis, legal analysis, etc. Any scenario with an "expert teaches → student practices → gradual internalization" knowledge transfer pattern.

Why This Exists

Claude starts every conversation from zero. In professional apprenticeship-style teaching:

• Expert lessons are forgotten — context compaction drops critical lessons, same mistakes repeat
• AI fabricates terminology — without ground truth, it over-generalizes from single demonstrations
• Knowledge can't evolve — new teachings can't replace contradicted old knowledge
• Search is path-dependent — rephrasing a question yields no results
• Forever a student — no mechanism for the AI's own discoveries to become durable knowledge

Installation

cd mcp/knowledge-graph
npm install

On first startup, the Qwen3-Embedding-0.6B ONNX model (~560MB) is automatically downloaded (one-time only).

MCP Configuration

In your project's .mcp.json:

{
  "mcpServers": {
    "knowledge-graph": {
      "command": "node",
      "args": ["/absolute/path/to/mcp/knowledge-graph/main.js"]
    }
  }
}

Hook Configuration

Add hooks to ~/.claude/settings.json (see Hooks section for full configuration).

Import Existing Knowledge (Optional)

node scripts/import-skills.js       # Import markdown files as KG nodes
node scripts/backfill-embeddings.js  # Add vector indexes + structural edges
node scripts/backfill-decay.js       # Add stability + memory_level + category

---

Core Design

Why Build From Scratch

After researching 25+ Claude Code memory systems (Claude-Recall, A-MEM, Mnemon, Graphiti, memsearch, etc.), none simultaneously satisfied:

Requirement	Existing Solutions	This System
Domain-specific edge types	Generic edges only	10 semantic edge types (must_precede, aligns_to, etc.)
Trust level distinction	No source differentiation	principle (expert-taught) > pattern (observed) > inference (AI-guessed)
Anti-fabrication	No protection	principle requires expert's exact quote
Fundamentals vs creative space	Treated equally	fundamental never decays, creative is challengeable
Memory decay + growth path	Decay exists but no growth	FSRS desirable difficulty + Benna-Fusi 4-level cascade
Automation	Depends on user action	6 hooks covering full lifecycle

Inspiration Sources

Source	What We Borrowed
Claude-Recall	Hook architecture (search enforcer, correction detector)
A-MEM	Edge data model (relation_type + reasoning + weight)
CortexGraph	Two-component decay (fast + slow exponential, more realistic than single decay)
FSRS (Anki)	Desirable difficulty (fading memories gain MORE stability when recalled)
Benna-Fusi	Memory cascade (4-level durability, independent of knowledge source)
Stanford Generative Agents	Three-signal retrieval (recency + importance + relevance)
Graphiti/Zep	Temporal awareness (valid_from / valid_until)

---

Three-Layer Architecture

┌──────────────────────────────────────────────────┐
│ Layer 1: Persona (CLAUDE.md)                      │
│ Agent identity + behavioral rules                 │
│ → Loaded every turn for consistent behavior       │
├──────────────────────────────────────────────────┤
│ Layer 2: Memory (Knowledge Graph MCP)             │
│ SQLite + sqlite-vec + FTS5                        │
│ 12 MCP tools + hybrid search                      │
│ → On-demand, doesn't consume context              │
├──────────────────────────────────────────────────┤
│ Layer 3: Automation (Hooks)                       │
│ 6 hooks covering full lifecycle                   │
│ → Expert doesn't need to remind, fully automatic  │
└──────────────────────────────────────────────────┘

---

Memory Decay & Growth System

Design Philosophy

Apprentice phase: Expert's words carry highest weight → learn fundamentals
Growth phase:     Own observations get validated → develop judgment
Expert phase:     Own inferences confirmed by practice → form independent views

Trust is a source label (who said it), not a permanent rank. AI's own validated knowledge can become equally durable.

Decay: CortexGraph Two-Component × FSRS Stability

R = W_fast × e^(-λ_fast × t) + W_slow × e^(-λ_slow × t)

• Fast decay (half-life = S days): "newly learned things are easily forgotten"
• Slow decay (half-life = S×10 days): "what survives is remembered for a long time"
• S (stability): initialized by trust + category, grows on access via FSRS

Why not pure exponential or pure power-law: pure exponential forgets too fast, pure power-law retains too much. Two-component blend best fits human forgetting data.

Knowledge Type	Initial S	Fast Half-Life	Slow Half-Life
Fundamental (has right/wrong)	365 days	—	—
Expert's creative choice	30 days	30d	300d
Observed pattern	7 days	7d	70d
AI inference	3 days	3d	30d

Reinforcement: FSRS Desirable Difficulty

stabilityGain = e^(1 - R) × gradeMultiplier

Core insight (from FSRS analysis of millions of Anki reviews): A fading memory that gets recalled gains MORE stability than a fresh one.

• R = 0.9 (just accessed) → 1.11× growth
• R = 0.3 (almost forgotten) → 2.01× growth

Grade sources:

• 4 = Successfully applied (Auto-Capture detects no correction)
• 3 = Normal access
• 1 = Corrected by expert

Growth Path: Benna-Fusi Memory Cascade

Trust (source label) stays unchanged; memory_level (durability) grows independently:

Level	Condition	Auto-expire?
1 New	Default	✅ when R < 0.02
2 Verifying	Accessed across 3+ sessions	✅ when R < 0.02
3 Consolidated	14 days + access ≥ 5	❌ Never
4 Core	Fundamental, or access ≥ 50	❌ Never

An inference node accessed 50 times reaches level 4 — as durable as a fundamental principle.

Fundamentals vs Creative Space

Type	metadata.category	Behavior
Fundamental	"fundamental"	R = 1.0, never decays. Has right/wrong answers
Creative	"creative"	Can decay, can be challenged. No right/wrong, only fit

---

Search System

Hybrid Three-in-One Search

score = 0.4 × vector + 0.2 × keyword + 0.3 × graph + memoryScore

Layer	Mechanism	Strength
Vector	sqlite-vec cosine KNN (Qwen3 1024d)	Same meaning, different words
Keyword	FTS5 BM25 (unicode61)	Exact match, multilingual
Graph	Recursive CTE, 1-hop expansion	Causal relationships
memoryScore	R × 0.1 + levelBonus	More used = more important

Embedding Design

• Model: Qwen3-Embedding-0.6B (ONNX quantized, ~560MB)
• Runs locally: Zero API dependency, works offline
• Why Qwen3: #1 on MTEB multilingual leaderboard, #1 on C-MTEB (Chinese)
• Embeds: name + content (full text) — vector handles semantic matching, keyword handles exact matching, clear separation of concerns

---

Anti-Fabrication

AI tends to treat its own guesses as facts. Protection rules:

Rule	Mechanism
Principle requires quote	No expert's exact words → rejected
Inference can't create causal edges	must_precede / reason_for reject inference nodes
Trust never auto-upgrades	Inference won't become principle (needs expert confirmation + quote)
Level is independent of trust	Inference can consolidate to level 4 but still labeled "AI's idea"

---

Tools (12)

Knowledge Management

Tool	Purpose
store_knowledge	Store a knowledge node. Auto embedding/FTS + suggests edges + initializes decay params
connect_knowledge	Create a causal edge. Includes anti-fabrication validation
update_knowledge	Update node in-place. Preserves ID and all edges, auto-updates indexes
forget_knowledge	Mark as expired. Auto-expires edges + cleans indexes

Search

Tool	Purpose
search_memory	Hybrid search (vector + keyword + graph + memoryScore)
traverse_graph	Walk causal edges (supports direction/depth/edge type filtering)
list_knowledge	List by filters (trust/type/element/source, sort by time/access/strength)

Experience

Tool	Purpose
record_experience	Record workflow trace (steps + decisions + outcomes)
recall_experience	Find similar past experiences by context

Maintenance

Tool	Purpose
maintain_graph	Memory Enzyme — prune / merge / validate / orphan
crystallize_skill	Check KG-to-skill-file sync status
memory_stats	Graph statistics

---

Hooks (Automation)

Lifecycle Coverage

[New Session]
  └─ session-start → auto-repair + memory decay + consolidation detection + edge review

[User Sends Message]
  └─ auto-recall → query KG → inject relevant knowledge
                 → correction detector → detect corrections

[AI About to Act]
  └─ search-enforcer → block operations without prior memory search (in specific modes)

[AI Finishes Response]
  └─ auto-capture → analyze learning signals → block → main Claude stores via MCP

[Context Compaction]
  └─ post-compact → re-inject core knowledge

settings.json Example

{
  "hooks": {
    "SessionStart": [
      {
        "matcher": "startup",
        "hooks": [{
          "type": "command",
          "command": "node /path/to/hooks/session-start.js",
          "timeout": 10
        }]
      },
      {
        "matcher": "compact",
        "hooks": [{
          "type": "command",
          "command": "node /path/to/hooks/post-compact.js",
          "timeout": 10
        }]
      }
    ],
    "UserPromptSubmit": [{
      "hooks": [{
        "type": "command",
        "command": "node /path/to/hooks/auto-recall.js",
        "timeout": 10
      }]
    }],
    "Stop": [{
      "hooks": [{
        "type": "agent",
        "model": "claude-opus-4-6",
        "prompt": "See auto-capture prompt in settings.json",
        "timeout": 60
      }]
    }],
    "PreToolUse": [{
      "hooks": [{
        "type": "command",
        "command": "node /path/to/hooks/search-enforcer.js",
        "timeout": 5
      }]
    }]
  }
}

Auto-Capture Design

Agent hooks cannot call MCP tools. Solution: the agent analyzes the conversation → outputs <auto-capture> instructions → blocks the main Claude → main Claude uses MCP tools to store knowledge → Stop fires again → stop_hook_active=true → allows stop.

User experience: the main AI naturally "remembers" to save knowledge, seamlessly using MCP tools.

---

Session-Start Auto-Maintenance

Automatically runs on every new session:

1. Repair dangling edges — edges pointing to expired nodes
2. Clean residual indexes — FTS5/vec entries for expired nodes
3. Report orphan nodes — nodes with no edges (>5 triggers warning)
4. Memory decay — R < 0.02 and level < 3 → expire
5. Decay report — show nodes with R < 0.3 (actively decaying)
6. Consolidation detection — vector similarity < 0.25 node pairs
7. Weak edge cleanup — weight < 0.3 → expire
8. Recent edge review — edges created in last 24 hours

---

Data Model

Nodes

Field	Description
type	rule / procedure / observation / insight / core / preference
trust	principle (expert-taught) / pattern (observed) / inference (AI-guessed)
stability	FSRS S (days), controls decay speed
memory_level	Benna-Fusi level 1-4, controls durability
metadata.category	fundamental (has right/wrong) / creative (no right/wrong)
source	session ID / "teacher" / "auto-capture"
quote	Expert's exact words (required for principle)

Edges

Edge	Meaning
must_precede	A must come before B
requires_reading	Must read B before operating on A
refines	A refines/extends B
contradicts	A contradicts B
reason_for	A is the reason for B
causes / implies / aligns_to / tends_to / observed_in	Other semantic relations

---

Security

Risk	Protection
SQL injection	Parameterized queries + whitelist validation
FTS5 special characters	Sanitize + double-quote wrapping
Non-atomic store	Node + FTS wrapped in transaction
Invalid ID timeout	try/except returns clear error
Stability overflow	Capped at 365 days
Single-session level inflation	metadata.sessions tracks cross-session usage

---

Integration

Recommended Skill Structure

Knowledge Graph stores "knowledge"; Skill files define "behavior". They complement each other:

• KG: What the expert taught, what was observed, what the AI inferred (storage & retrieval)
• Skill: What to do with that knowledge (executable workflows & checklists)

Recommended skill directory structure:

skills/
├── <domain>/                    # Domain knowledge (e.g., coding/, design/, medical/)
│   ├── principles.md            # Core principles
│   ├── elements/                # Operation workflows per element/module
│   │   ├── <element>/
│   │   │   └── workflow.md      # Executable tool operation steps
│   │   └── checklist.md         # Element list + dependency graph + standard flow
│   └── evaluation/              # Quality evaluation criteria
├── specialty/                   # Specialty overrides (if applicable)
│   └── <specialty>/
│       └── <domain>/            # Specialty-specific knowledge overrides
├── tools/                       # Tool usage knowledge
│   ├── gotchas/                 # Dangerous operations / pitfalls
│   └── batch/                   # Batch tool reference
└── preflight.md                 # Pre-work required reading checklist

Skill File Writing Principles

# Element Name — Tool Operation Workflow

## Related Elements

| Dependency | Reason | Must Read |
|------------|--------|-----------|
| X | Why X is needed | `path/to/x.md` |

## Operation Steps

1. Specific enough to execute directly
2. Include tool call examples (tool_name + parameters)
3. No abstract descriptions ("do it well" → "use tool X to set param Y to Z")

## Quality Criteria

Concrete values or qualitative descriptions the agent can use to judge.

Key: Skill files must be "executable" — an agent (or subagent) should be able to operate directly after reading, without guessing.

KG-Skill Synchronization

Use crystallize_skill to check if KG contains knowledge not yet reflected in skill files:

crystallize_skill(topic="authentication", skill_paths=["skills/coding/elements/auth/workflow.md"])

Returns unsynced knowledge list → manually update skill files.

Pairing With Other MCP Servers

Knowledge Graph is the memory layer. It typically pairs with a domain-specific MCP for actual operations:

Combination	Knowledge Graph Handles	Domain MCP Handles
Software Development	Architecture decisions, code review lessons, bug patterns	IDE / Git / CI operations
Design	Design principles, brand guidelines, user feedback	Figma / design tool operations
Data Analysis	Analysis methodology, domain knowledge, past analyses	DB / BI tool operations
Any Professional Domain	Domain knowledge, workflow experience, expert teaching	Corresponding operation tools

Knowledge Graph doesn't perform domain operations — it only remembers "how to do it" and "why it's done this way", then automatically recalls relevant knowledge when needed.

Pairing With Session Readers

Knowledge extraction requires reading historical conversations. Recommended to pair with MCP servers that can read Claude Code CLI or other session transcripts, enabling review of teaching processes and knowledge extraction.

---

References

Academic Papers

Paper	Contribution
FSRS Algorithm	Power-law forgetting curve + desirable difficulty. 19 ML parameters trained on millions of Anki reviews
MemoryBank (AAAI 2024)	LLM long-term memory + Ebbinghaus forgetting curve implementation
Benna & Fusi (Nature Neuroscience 2016)	Synaptic cascade model. Multi-timescale storage, memory lifetime scales linearly with synapse count
Generative Agents (Stanford, UIST 2023)	Recency + importance + relevance three-signal retrieval. Reflection mechanism compresses observations into higher-order insights
Zep: Temporal KG Architecture	Bi-temporal model (event time + ingestion time). Edge temporal validity intervals
Theories of Synaptic Memory Consolidation	Elastic Weight Consolidation + Synaptic Intelligence. Critical parameter protection
Mem0: AI Agent Memory	Production-ready agent memory architecture. Graph + vector hybrid

Open Source Implementations

Project	What We Borrowed
CortexGraph	Two-component decay (power-law + exponential blend), consolidation threshold, sub-linear frequency n^0.6
Claude-Recall	Search enforcer hook, correction detector, skill crystallization
A-MEM	Typed edges (relation_type + reasoning + weight), memory enzyme maintenance
Mnemon	4-graph architecture, intent-aware traversal, importance decay + access-count boosting
memsearch (Zilliz)	Standalone memory library extracted from OpenClaw. Hybrid dense+BM25+RRF, SHA-256 dedup
second-brain (jugaad-lab)	Category-weighted decay, auto-consolidation (7-day window), entity graph weekly rebuild
Graphiti (Zep)	Temporal knowledge graph, bi-temporal model, edge invalidation
Hippocampus Memory Skill	Salience formula (0.5×semantic + 0.2×reinforcement + 0.2×recency + 0.1×frequency), 4-tier memory
YourMemory	Simplest implementation: strength = importance × e^(-λ × days) × (1 + recall_count × 0.2)

Cognitive Science

Concept	Application
Ebbinghaus Forgetting Curve	Foundation model for memory strength decaying over time
SM-2 Algorithm (SuperMemo)	Classic spaced repetition algorithm. EF (easiness factor) + interval growth
Desirable Difficulty	Robert Bjork: appropriate difficulty enhances long-term memory. Core theoretical basis of FSRS
Synaptic Tagging and Capture	Synaptic tag + protein synthesis = memory consolidation. Maps to our level promotion mechanism

---

Acknowledgments

This system's design integrates wisdom from multiple open-source communities and academic research. Special thanks to:

• open-spaced-repetition for the FSRS algorithm, providing a desirable difficulty model validated on millions of data points
• prefrontal-systems for CortexGraph, whose two-component decay model forms the core of our memory decay engine
• Anthropic for Claude-Recall, whose hook architecture and search enforcer patterns directly inspired our automation layer
• Stanford HCI Group for the Generative Agents paper (Park et al., 2023), whose three-signal retrieval and reflection mechanisms influenced our search scoring and consolidation design
• Benna & Fusi for their synaptic cascade model published in Nature Neuroscience, providing the neuroscience foundation for our memory level growth path
• Zilliz (memsearch), jugaad-lab (second-brain), Zep (Graphiti), and other open-source projects that each contributed valuable implementation experience

---

Deployment

Included in the Repository

• All lib/, tools/, hooks/, scripts/ source code
• Hook configuration examples

Generated by User

• knowledge.db — automatically created on first startup
• Qwen3 ONNX model — automatically downloaded on first embed
• node_modules/ — npm install

First-Time Setup

1. npm install
2. Configure .mcp.json + ~/.claude/settings.json hooks
3. Start Claude Code → MCP auto-starts → model auto-downloads
4. Begin conversation → hooks auto-run → knowledge auto-accumulates

License

MIT