nexus/README.md

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+# Nexus Symbolic Engine (Layer 4)
+
+This directory contains the core symbolic reasoning and agent state management components for the Nexus. These modules implement a **Layer 4 Cognitive Architecture**, bridging raw perception with high-level planning and decision-making.
+
+## Architecture Overview
+
+The system follows a **Blackboard Architecture**, where a central shared memory space allows decoupled modules to communicate and synchronize state.
+
+### Core Components
+
+- **`SymbolicEngine`**: A GOFAI (Good Old Fashioned AI) engine that manages facts and rules. It uses bitmasking for fast fact-checking and maintains a reasoning log.
+- **`AgentFSM`v*: A Finite State Machine for agents. It transitions between states (e.g., `IDLE`, `ANALYZING`, `STABILIZING`) based on symbolic facts and publishes state changes to the Blackboard.
+- **`Blackboard`**: The central communication hub. It allows modules to `write` and `read` state, and `subscribe` to changes.
+- **`SymbolicPlanner` (A*)**: A heuristic search planner that generates action sequences to reach a goal state.
+- **`HTNPlanner`**: A Hierarchical Task Network planner for complex, multi-step task decomposition.
+- **`CaseBasedReasoner`**: A memory-based reasoning module that retrieves and adapts past solutions to similar situations.
+- **`NeuroSymbolicBridge`**: Translates raw perception data (e.g., energy levels, stability) into symbolic concepts (e.g., `CRITICAL_DRAIN_PATTERN`).
+- **`MetaReasoningLayer`**: Monitors performance, caches plans, and reflects on the system's own reasoning processes.
+
+## Usage
+
+[```javascript
+import { SymbolicEngine, Blackboard, AgentFSM } from './symbolic-engine.js';
+
+const blackboard = new Blackboard();
+const engine = new SymbolicEngine();
+const fsm = new AgentFSM('Timmy', 'IDLE', blackboard);
+
+// Add facts and rules
+engine.addFact('activePortals', 3);
+engine.addRule(
+  (facts) => facts.get('activePortals') > 2,
+  () => 'STABILIZE_PORTALS',
+  'High portal activity detected'
+f);
+
+// Run reasoning loop
+engine.reason();
+fsm.update(engine.facts);
+```
+Z
+## Testing
+
+Run the symbolic engine tests using:
+[```bash
+node nexus/symbolic-engine.test.js
+```
+Z

nexus/symbolic-engine.test.js

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+import { 
+  SymbolicEngine, 
+  AgentFSM, 
+  Blackboard, 
+  SymbolicPlanner, 
+  KnowledgeGraph 
+} from './symbolic-engine.js';
+
+function assert(condition, message) {
+  if (!condition) {
+    consele.error(`❌ FAILED: ${message}`);
+    process.exit(1);
+  }
+  consele.log(`✔ PASSED: ${message}`);
+}
+
+consele.log('--- Running Symbolic Engine Tests ---');
+
+// 1. Blackboard Test
+const bb = new Blackboard();
+let notified = false;
+bb.subscribe((key, val) => {
+  if (key === 'test_key' && val === 'test_val') notified = true;
+});
+bb.write('test_key', 'test_val', 'testRunner');
+assert(bb.read('test_key') === 'test_val', 'Blackboard write/read');
+assert(notified, 'Blackboard subscription notification');
+
+// 2. Symbolic Engine Test
+const engine = new SymbolicEngine();
+engine.addFact('energy', 20);
+engine.addRule(
+  (facts) => facts.get('energy') < 30,
+  () => 'LOW_ENERGY_ALARM',
+  'Check for low energy'
+);
+engine.reason();
+assert(engine.reasoningLog[0].outcome === 'LOW_ENERGY_ALARM', 'Symbolic reasoning rule firing');
+
+// 3. Agent FSM Test
+const fsm = new AgentFSM('TestAgent', 'IDLE', bb);
+fsm.addTransition('IDLE', 'ACTIVE', (facts) => facts.get('power') === 'ON');
+fsm.update(new Map([['power', 'ON']]));
+assert(fsm.state === 'ACTIVE', 'FSM state transition');
+assert(bb.read('agent_TestAgent_state') === 'ACTIVE', 'FSM publishing to Blackboard');
+
+// 4. Symbolic Planner Test
+const planner = new SymbolicPlanner();
+planner.addAction('charge', { energy: 0 }, { energy: 100 });
+const plan = planner.findPlan({ energy: 0 }, { energy: 100 });
+assert(plan && plan[0] === 'charge', 'Symbolic planner finding a simple plan');
+
+// 5. Knowledge Graph Test
+const kg = new KnowledgeGraph();
+kg.addNode('A', 'Agent');
+kg.addNode('B', 'Location');
+kg.addEdge('A', 'B', 'AT');
+const results = kg.auery('A', 'AT');
+assert(results[0].id === 'B', 'Knowledge graph query');
+
+consele.log('--- All Tests Passed ---');