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Implementation Summary: Knowledge Graph Bridge

Task: Improvement 2 - Expose Knowledge Graph APIs via Agent Service Bridge Date: 2025-11-12 Status: ✅ Complete Test Coverage: 24/24 passing (100%)

Problem Statement

Handlers needing structured relationship queries had to re-import kg-sqlite.cjs directly because agent-service-bridge.cjs didn't export KG APIs. This caused:

  • Duplicated connection logic across handlers
  • Multiple KG instances (memory waste)
  • Harder to enforce lens validation
  • Inconsistent error handling

Solution Implemented

Added knowledgeGraph export to agent-service-bridge.cjs with 3 core methods:

  1. hybridSearch(query, options) - Vector + FTS + Graph queries
  2. findPaths(startNode, endNode, options) - Multi-hop relationship traversal
  3. logInteraction(interaction) - Event logging for learning

Key Features

✅ Lazy initialization - KG instance created on first use ✅ Shared instance - Single connection across all handlers ✅ Error wrapping - All errors prefixed with KG [method] failed: for context ✅ Backward compatible - No breaking changes to existing exports ✅ Fully tested - 24 integration tests + 16 existing tests all passing

Files Modified

1. backend/services/agent-service-bridge.cjs

Changes:

  • Added KnowledgeGraph import (line 39)
  • Added knowledgeGraphBridge object (lines 386-473)
    • _getKG() - Lazy initialization helper
    • hybridSearch() - Wrapper with error handling
    • findPaths() - Wrapper with error handling
    • logInteraction() - Wrapper with error handling
  • Updated exports to include knowledgeGraph (line 491)
  • Updated isAvailable to include knowledgeGraph: true (line 508)

Lines Added: 91 lines Breaking Changes: None

Files Created

1. backend/tests/agent-service-bridge-kg.test.cjs

Purpose: Integration tests for KG bridge APIs Test Suites: 8 suites, 24 tests Coverage:

  • Export availability (5 tests)
  • KG instance initialization (1 test)
  • hybridSearch method (5 tests)
  • findPaths method (4 tests)
  • logInteraction method (4 tests)
  • Data structure validation (2 tests)
  • Integration with existing services (2 tests)
  • Cleanup (1 test)

Status: ✅ 24/24 passing

2. backend/examples/kg-bridge-usage.cjs

Purpose: Usage examples for handler developers Examples:

  1. Hybrid search for related documents
  2. Graph traversal for entity relationships
  3. Log agent interactions for learning
  4. Complete workflow (query → path analysis → logging)
  5. Error handling pattern

Runnable: Yes (node backend/examples/kg-bridge-usage.cjs)

3. backend/services/KNOWLEDGE-GRAPH-BRIDGE.md

Purpose: Complete documentation for KG bridge Contents:

  • Problem solved (before/after comparison)
  • API reference for all 3 methods
  • Implementation details (lazy init, error handling)
  • Testing instructions
  • Usage patterns
  • Migration guide for existing handlers
  • Future enhancements roadmap

Test Results

New Integration Tests

📊 Test Summary: 24/24 passed
✅ All tests passed

Existing Bridge Tests

📊 Test Summary: 16/16 passed
✅ All tests passed

Full Test Suite

npm test
ok 3 - /home/michael/soulfield/backend/tests/agent-service-bridge-kg.test.cjs
ok 4 - /home/michael/soulfield/backend/tests/agent-service-bridge.test.cjs

Usage Examples

═══════════════════════════════════════════════════════════
✅ All examples completed successfully
═══════════════════════════════════════════════════════════

API Usage

Before (Direct Import)

const KnowledgeGraph = require('../services/knowledge-graph/kg-sqlite.cjs');

async function handler(prompt) {
  const kg = new KnowledgeGraph();
  await kg.initialize();
  const results = await kg.hybridSearch(prompt);
  // ...
}

After (Via Bridge)

const services = require('../services/agent-service-bridge.cjs');

async function handler(prompt) {
  const results = await services.knowledgeGraph.hybridSearch(prompt);
  // ...
}

Benefits:

  • 5 lines → 1 line (80% reduction)
  • No initialization boilerplate
  • Shared KG instance (memory efficient)
  • Consistent error handling

Method Signatures

1. hybridSearch(query, options)

await services.knowledgeGraph.hybridSearch('marketing campaigns', {
  agent: 'marketing',      // Filter by agent (optional)
  limit: 5,                // Max results (default: 10)
  includeGraph: true,      // Include graph scoring (default: true)
  includeEmbeddings: true  // Include vector similarity (default: true)
});

// Returns: Array<{ document_id, title, snippet, finalScore, ... }>

2. findPaths(startNode, endNode, options)

await services.knowledgeGraph.findPaths(entityId1, entityId2, {
  maxDepth: 3  // Max hops (default: 3)
});

// Returns: Array<{ source_id, target_id, path, depth, total_weight }>

3. logInteraction(interaction)

await services.knowledgeGraph.logInteraction({
  sessionId: 'session-123',
  query: 'How does TruthLens work?',
  response: 'TruthLens validates...',
  agent: 'marketing',
  documentsUsed: ['doc_1', 'doc_2']  // Optional
});

// Returns: Promise<void>

Error Handling

All errors wrapped with bridge context:

try {
  const results = await services.knowledgeGraph.hybridSearch(query);
} catch (error) {
  // error.message: "KG hybridSearch failed: <original error>"
  console.error('KG query failed:', error.message);
  // Fallback logic here
}

Pattern: All KG errors prefixed with KG [method] failed: for easy identification in logs

Verification Commands

# Run new integration tests
node backend/tests/agent-service-bridge-kg.test.cjs

# Run existing bridge tests
node backend/tests/agent-service-bridge.test.cjs

# Run all tests
npm test

# Run usage examples
node backend/examples/kg-bridge-usage.cjs

# With debug logging
LENS_DEBUG=true node backend/tests/agent-service-bridge-kg.test.cjs

Acceptance Criteria

✅ agent-service-bridge.cjs exports knowledgeGraph with 3 methods

  • hybridSearch ✓
  • findPaths ✓
  • logInteraction ✓

✅ Integration test created and passing

  • 24 tests created
  • 24/24 passing (100%)

✅ Existing agent-service-bridge tests still pass

  • 16/16 passing (100%)

✅ No breaking changes to existing exports

  • All 6 existing exports verified
  • Backward compatibility confirmed

Next Steps (Future Enhancements)

1. Lens Integration

  • Add TruthLens validation to query results
  • Verify entity confidence scores
  • Structure validation for relationships

2. Handler Migration

  • Find handlers with direct KG imports: grep -r "require.*kg-sqlite" backend/agents/handlers/
  • Replace with bridge imports
  • Remove initialization boilerplate

3. Performance Optimization

  • Add result caching (LRU)
  • Monitor query latency via telemetry
  • Index optimization for FTS5

4. Documentation

  • Update handler development guide
  • Add KG query patterns to best practices
  • Document lens validation requirements

References

  • Implementation: backend/services/agent-service-bridge.cjs:386-473
  • Tests: backend/tests/agent-service-bridge-kg.test.cjs
  • Examples: backend/examples/kg-bridge-usage.cjs
  • Documentation: backend/services/KNOWLEDGE-GRAPH-BRIDGE.md
  • KG Implementation: backend/services/knowledge-graph/kg-sqlite.cjs

Metrics

Metric Value
Test Coverage 24/24 (100%)
Implementation Time ~45 minutes
Files Modified 1
Files Created 3
Lines Added ~550 (code + tests + docs)
Breaking Changes 0
Backward Compatibility ✅ Verified

Implementation Complete: 2025-11-12 Status: ✅ Production Ready Next Task: Handler migration (optional)