diff --git a/package.json b/package.json
index 64b11d4..366fb6e 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,7 @@
     "start": "node index.js",
     "run": "node index.js run",
     "solidify": "node index.js solidify",
+    "test": "node --test test/*.test.js",
     "a2a:export": "node scripts/a2a_export.js",
     "a2a:ingest": "node scripts/a2a_ingest.js",
     "a2a:promote": "node scripts/a2a_promote.js"
diff --git a/test/a2aProtocol.test.js b/test/a2aProtocol.test.js
new file mode 100644
index 0000000..7c43263
--- /dev/null
+++ b/test/a2aProtocol.test.js
@@ -0,0 +1,134 @@
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+const {
+  PROTOCOL_NAME,
+  PROTOCOL_VERSION,
+  VALID_MESSAGE_TYPES,
+  buildMessage,
+  buildHello,
+  buildPublish,
+  buildFetch,
+  buildReport,
+  buildDecision,
+  buildRevoke,
+  isValidProtocolMessage,
+  unwrapAssetFromMessage,
+} = require('../src/gep/a2aProtocol');
+
+describe('protocol constants', () => {
+  it('has expected protocol name', () => {
+    assert.equal(PROTOCOL_NAME, 'gep-a2a');
+  });
+
+  it('has 6 valid message types', () => {
+    assert.equal(VALID_MESSAGE_TYPES.length, 6);
+    for (const t of ['hello', 'publish', 'fetch', 'report', 'decision', 'revoke']) {
+      assert.ok(VALID_MESSAGE_TYPES.includes(t), `missing type: ${t}`);
+    }
+  });
+});
+
+describe('buildMessage', () => {
+  it('builds a valid protocol message', () => {
+    const msg = buildMessage({ messageType: 'hello', payload: { test: true } });
+    assert.equal(msg.protocol, PROTOCOL_NAME);
+    assert.equal(msg.message_type, 'hello');
+    assert.ok(msg.message_id.startsWith('msg_'));
+    assert.ok(msg.timestamp);
+    assert.deepEqual(msg.payload, { test: true });
+  });
+
+  it('rejects invalid message type', () => {
+    assert.throws(() => buildMessage({ messageType: 'invalid' }), /Invalid message type/);
+  });
+});
+
+describe('typed message builders', () => {
+  it('buildHello includes env_fingerprint', () => {
+    const msg = buildHello({});
+    assert.equal(msg.message_type, 'hello');
+    assert.ok(msg.payload.env_fingerprint);
+  });
+
+  it('buildPublish requires asset with type and id', () => {
+    assert.throws(() => buildPublish({}), /asset must have type and id/);
+    assert.throws(() => buildPublish({ asset: { type: 'Gene' } }), /asset must have type and id/);
+
+    const msg = buildPublish({ asset: { type: 'Gene', id: 'g1' } });
+    assert.equal(msg.message_type, 'publish');
+    assert.equal(msg.payload.asset_type, 'Gene');
+    assert.equal(msg.payload.local_id, 'g1');
+    assert.ok(msg.payload.signature);
+  });
+
+  it('buildFetch creates a fetch message', () => {
+    const msg = buildFetch({ assetType: 'Capsule', localId: 'c1' });
+    assert.equal(msg.message_type, 'fetch');
+    assert.equal(msg.payload.asset_type, 'Capsule');
+  });
+
+  it('buildReport creates a report message', () => {
+    const msg = buildReport({ assetId: 'sha256:abc', validationReport: { ok: true } });
+    assert.equal(msg.message_type, 'report');
+    assert.equal(msg.payload.target_asset_id, 'sha256:abc');
+  });
+
+  it('buildDecision validates decision values', () => {
+    assert.throws(() => buildDecision({ decision: 'maybe' }), /decision must be/);
+
+    for (const d of ['accept', 'reject', 'quarantine']) {
+      const msg = buildDecision({ decision: d, assetId: 'test' });
+      assert.equal(msg.payload.decision, d);
+    }
+  });
+
+  it('buildRevoke creates a revoke message', () => {
+    const msg = buildRevoke({ assetId: 'sha256:abc', reason: 'outdated' });
+    assert.equal(msg.message_type, 'revoke');
+    assert.equal(msg.payload.reason, 'outdated');
+  });
+});
+
+describe('isValidProtocolMessage', () => {
+  it('returns true for well-formed messages', () => {
+    const msg = buildHello({});
+    assert.ok(isValidProtocolMessage(msg));
+  });
+
+  it('returns false for null/undefined', () => {
+    assert.ok(!isValidProtocolMessage(null));
+    assert.ok(!isValidProtocolMessage(undefined));
+  });
+
+  it('returns false for wrong protocol', () => {
+    assert.ok(!isValidProtocolMessage({ protocol: 'other', message_type: 'hello', message_id: 'x', timestamp: 'y' }));
+  });
+
+  it('returns false for missing fields', () => {
+    assert.ok(!isValidProtocolMessage({ protocol: PROTOCOL_NAME }));
+  });
+});
+
+describe('unwrapAssetFromMessage', () => {
+  it('extracts asset from publish message', () => {
+    const asset = { type: 'Gene', id: 'g1', strategy: ['test'] };
+    const msg = buildPublish({ asset });
+    const result = unwrapAssetFromMessage(msg);
+    assert.equal(result.type, 'Gene');
+    assert.equal(result.id, 'g1');
+  });
+
+  it('returns plain asset objects as-is', () => {
+    const gene = { type: 'Gene', id: 'g1' };
+    assert.deepEqual(unwrapAssetFromMessage(gene), gene);
+
+    const capsule = { type: 'Capsule', id: 'c1' };
+    assert.deepEqual(unwrapAssetFromMessage(capsule), capsule);
+  });
+
+  it('returns null for unrecognized input', () => {
+    assert.equal(unwrapAssetFromMessage(null), null);
+    assert.equal(unwrapAssetFromMessage({ random: true }), null);
+    assert.equal(unwrapAssetFromMessage('string'), null);
+  });
+});
diff --git a/test/contentHash.test.js b/test/contentHash.test.js
new file mode 100644
index 0000000..b735ff6
--- /dev/null
+++ b/test/contentHash.test.js
@@ -0,0 +1,106 @@
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+const { canonicalize, computeAssetId, verifyAssetId, SCHEMA_VERSION } = require('../src/gep/contentHash');
+
+describe('canonicalize', () => {
+  it('serializes null and undefined as "null"', () => {
+    assert.equal(canonicalize(null), 'null');
+    assert.equal(canonicalize(undefined), 'null');
+  });
+
+  it('serializes primitives', () => {
+    assert.equal(canonicalize(true), 'true');
+    assert.equal(canonicalize(false), 'false');
+    assert.equal(canonicalize(42), '42');
+    assert.equal(canonicalize('hello'), '"hello"');
+  });
+
+  it('serializes non-finite numbers as null', () => {
+    assert.equal(canonicalize(Infinity), 'null');
+    assert.equal(canonicalize(-Infinity), 'null');
+    assert.equal(canonicalize(NaN), 'null');
+  });
+
+  it('serializes arrays preserving order', () => {
+    assert.equal(canonicalize([1, 2, 3]), '[1,2,3]');
+    assert.equal(canonicalize([]), '[]');
+  });
+
+  it('serializes objects with sorted keys', () => {
+    assert.equal(canonicalize({ b: 2, a: 1 }), '{"a":1,"b":2}');
+    assert.equal(canonicalize({ z: 'last', a: 'first' }), '{"a":"first","z":"last"}');
+  });
+
+  it('produces deterministic output regardless of key insertion order', () => {
+    const obj1 = { c: 3, a: 1, b: 2 };
+    const obj2 = { a: 1, b: 2, c: 3 };
+    assert.equal(canonicalize(obj1), canonicalize(obj2));
+  });
+
+  it('handles nested objects and arrays', () => {
+    const nested = { arr: [{ b: 2, a: 1 }], val: null };
+    const result = canonicalize(nested);
+    assert.equal(result, '{"arr":[{"a":1,"b":2}],"val":null}');
+  });
+});
+
+describe('computeAssetId', () => {
+  it('returns a sha256-prefixed hash string', () => {
+    const id = computeAssetId({ type: 'Gene', id: 'test_gene' });
+    assert.ok(id.startsWith('sha256:'));
+    assert.equal(id.length, 7 + 64); // "sha256:" + 64 hex chars
+  });
+
+  it('excludes asset_id field from hash by default', () => {
+    const obj = { type: 'Gene', id: 'g1', data: 'x' };
+    const withoutField = computeAssetId(obj);
+    const withField = computeAssetId({ ...obj, asset_id: 'sha256:something' });
+    assert.equal(withoutField, withField);
+  });
+
+  it('produces identical hashes for identical content', () => {
+    const a = computeAssetId({ type: 'Capsule', id: 'c1', value: 42 });
+    const b = computeAssetId({ type: 'Capsule', id: 'c1', value: 42 });
+    assert.equal(a, b);
+  });
+
+  it('produces different hashes for different content', () => {
+    const a = computeAssetId({ type: 'Gene', id: 'g1' });
+    const b = computeAssetId({ type: 'Gene', id: 'g2' });
+    assert.notEqual(a, b);
+  });
+
+  it('returns null for non-object input', () => {
+    assert.equal(computeAssetId(null), null);
+    assert.equal(computeAssetId('string'), null);
+  });
+});
+
+describe('verifyAssetId', () => {
+  it('returns true for correct asset_id', () => {
+    const obj = { type: 'Gene', id: 'g1', data: 'test' };
+    obj.asset_id = computeAssetId(obj);
+    assert.ok(verifyAssetId(obj));
+  });
+
+  it('returns false for tampered content', () => {
+    const obj = { type: 'Gene', id: 'g1', data: 'test' };
+    obj.asset_id = computeAssetId(obj);
+    obj.data = 'tampered';
+    assert.ok(!verifyAssetId(obj));
+  });
+
+  it('returns false for missing asset_id', () => {
+    assert.ok(!verifyAssetId({ type: 'Gene', id: 'g1' }));
+  });
+
+  it('returns false for null input', () => {
+    assert.ok(!verifyAssetId(null));
+  });
+});
+
+describe('SCHEMA_VERSION', () => {
+  it('is a semver string', () => {
+    assert.match(SCHEMA_VERSION, /^\d+\.\d+\.\d+$/);
+  });
+});
diff --git a/test/mutation.test.js b/test/mutation.test.js
new file mode 100644
index 0000000..f8dc46f
--- /dev/null
+++ b/test/mutation.test.js
@@ -0,0 +1,142 @@
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+const {
+  buildMutation,
+  isValidMutation,
+  normalizeMutation,
+  isHighRiskMutationAllowed,
+  isHighRiskPersonality,
+  clamp01,
+} = require('../src/gep/mutation');
+
+describe('clamp01', () => {
+  it('clamps values to [0, 1]', () => {
+    assert.equal(clamp01(0.5), 0.5);
+    assert.equal(clamp01(0), 0);
+    assert.equal(clamp01(1), 1);
+    assert.equal(clamp01(-0.5), 0);
+    assert.equal(clamp01(1.5), 1);
+  });
+
+  it('returns 0 for non-finite input', () => {
+    assert.equal(clamp01(NaN), 0);
+    assert.equal(clamp01(undefined), 0);
+    // Note: clamp01(Infinity) returns 0 because the implementation checks
+    // Number.isFinite() before clamping. Mathematically clamp(Inf, 0, 1) = 1,
+    // but the current behavior treats all non-finite values uniformly as 0.
+    assert.equal(clamp01(Infinity), 0);
+  });
+});
+
+describe('buildMutation', () => {
+  it('returns a valid Mutation object', () => {
+    const m = buildMutation({ signals: ['log_error'], selectedGene: { id: 'gene_repair' } });
+    assert.ok(isValidMutation(m));
+    assert.equal(m.type, 'Mutation');
+    assert.ok(m.id.startsWith('mut_'));
+  });
+
+  it('selects repair category when error signals present', () => {
+    const m = buildMutation({ signals: ['log_error', 'errsig:something'] });
+    assert.equal(m.category, 'repair');
+  });
+
+  it('selects innovate category when drift enabled', () => {
+    const m = buildMutation({ signals: ['stable_success_plateau'], driftEnabled: true });
+    assert.equal(m.category, 'innovate');
+  });
+
+  it('selects innovate for opportunity signals without errors', () => {
+    const m = buildMutation({ signals: ['user_feature_request'] });
+    assert.equal(m.category, 'innovate');
+  });
+
+  it('downgrades innovate to optimize for high-risk personality', () => {
+    const highRiskPersonality = { rigor: 0.3, risk_tolerance: 0.8, creativity: 0.5 };
+    const m = buildMutation({
+      signals: ['user_feature_request'],
+      personalityState: highRiskPersonality,
+    });
+    assert.equal(m.category, 'optimize');
+    assert.ok(m.trigger_signals.some(s => s.includes('safety')));
+  });
+
+  it('caps risk_level to medium when personality disallows high risk', () => {
+    const conservativePersonality = { rigor: 0.5, risk_tolerance: 0.6, creativity: 0.5 };
+    const m = buildMutation({
+      signals: ['stable_success_plateau'],
+      driftEnabled: true,
+      allowHighRisk: true,
+      personalityState: conservativePersonality,
+    });
+    assert.notEqual(m.risk_level, 'high');
+  });
+});
+
+describe('isValidMutation', () => {
+  it('returns true for valid mutation', () => {
+    const m = buildMutation({ signals: ['log_error'] });
+    assert.ok(isValidMutation(m));
+  });
+
+  it('returns false for missing fields', () => {
+    assert.ok(!isValidMutation(null));
+    assert.ok(!isValidMutation({}));
+    assert.ok(!isValidMutation({ type: 'Mutation' }));
+  });
+
+  it('returns false for invalid category', () => {
+    assert.ok(!isValidMutation({
+      type: 'Mutation', id: 'x', category: 'destroy',
+      trigger_signals: [], target: 't', expected_effect: 'e', risk_level: 'low',
+    }));
+  });
+});
+
+describe('normalizeMutation', () => {
+  it('fills defaults for empty object', () => {
+    const m = normalizeMutation({});
+    assert.ok(isValidMutation(m));
+    assert.equal(m.category, 'optimize');
+    assert.equal(m.risk_level, 'low');
+  });
+
+  it('preserves valid fields', () => {
+    const m = normalizeMutation({
+      id: 'mut_custom', category: 'repair',
+      trigger_signals: ['log_error'], target: 'file.js',
+      expected_effect: 'fix bug', risk_level: 'medium',
+    });
+    assert.equal(m.id, 'mut_custom');
+    assert.equal(m.category, 'repair');
+    assert.equal(m.risk_level, 'medium');
+  });
+});
+
+describe('isHighRiskPersonality', () => {
+  it('detects low rigor as high risk', () => {
+    assert.ok(isHighRiskPersonality({ rigor: 0.3 }));
+  });
+
+  it('detects high risk_tolerance as high risk', () => {
+    assert.ok(isHighRiskPersonality({ risk_tolerance: 0.7 }));
+  });
+
+  it('returns false for conservative personality', () => {
+    assert.ok(!isHighRiskPersonality({ rigor: 0.8, risk_tolerance: 0.2 }));
+  });
+});
+
+describe('isHighRiskMutationAllowed', () => {
+  it('allows when rigor >= 0.6 and risk_tolerance <= 0.5', () => {
+    assert.ok(isHighRiskMutationAllowed({ rigor: 0.8, risk_tolerance: 0.3 }));
+  });
+
+  it('disallows when rigor too low', () => {
+    assert.ok(!isHighRiskMutationAllowed({ rigor: 0.4, risk_tolerance: 0.3 }));
+  });
+
+  it('disallows when risk_tolerance too high', () => {
+    assert.ok(!isHighRiskMutationAllowed({ rigor: 0.8, risk_tolerance: 0.6 }));
+  });
+});
diff --git a/test/selector.test.js b/test/selector.test.js
new file mode 100644
index 0000000..dbd8269
--- /dev/null
+++ b/test/selector.test.js
@@ -0,0 +1,112 @@
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+const { selectGene, selectCapsule, selectGeneAndCapsule } = require('../src/gep/selector');
+
+const GENES = [
+  {
+    type: 'Gene',
+    id: 'gene_repair',
+    category: 'repair',
+    signals_match: ['error', 'exception', 'failed'],
+    strategy: ['fix it'],
+    validation: ['node -e "true"'],
+  },
+  {
+    type: 'Gene',
+    id: 'gene_optimize',
+    category: 'optimize',
+    signals_match: ['protocol', 'prompt', 'audit'],
+    strategy: ['optimize it'],
+    validation: ['node -e "true"'],
+  },
+  {
+    type: 'Gene',
+    id: 'gene_innovate',
+    category: 'innovate',
+    signals_match: ['user_feature_request', 'capability_gap', 'stable_success_plateau'],
+    strategy: ['build it'],
+    validation: ['node -e "true"'],
+  },
+];
+
+const CAPSULES = [
+  {
+    type: 'Capsule',
+    id: 'capsule_1',
+    trigger: ['log_error', 'exception'],
+    gene: 'gene_repair',
+    summary: 'Fixed an error',
+    confidence: 0.9,
+  },
+  {
+    type: 'Capsule',
+    id: 'capsule_2',
+    trigger: ['protocol', 'gep'],
+    gene: 'gene_optimize',
+    summary: 'Optimized prompt',
+    confidence: 0.85,
+  },
+];
+
+describe('selectGene', () => {
+  it('selects the gene with highest signal match', () => {
+    const result = selectGene(GENES, ['error', 'exception', 'failed'], {});
+    assert.equal(result.selected.id, 'gene_repair');
+  });
+
+  it('returns null when no signals match', () => {
+    const result = selectGene(GENES, ['completely_unrelated_signal'], {});
+    assert.equal(result.selected, null);
+  });
+
+  it('returns alternatives when multiple genes match', () => {
+    const result = selectGene(GENES, ['error', 'protocol'], {});
+    assert.ok(result.selected);
+    assert.ok(Array.isArray(result.alternatives));
+  });
+
+  it('includes drift intensity in result', () => {
+    // Drift intensity is population-size-dependent; verify it is returned.
+    const result = selectGene(GENES, ['error', 'exception'], {});
+    assert.ok('driftIntensity' in result);
+    assert.equal(typeof result.driftIntensity, 'number');
+    assert.ok(result.driftIntensity >= 0 && result.driftIntensity <= 1);
+  });
+
+  it('respects preferred gene id from memory graph', () => {
+    const result = selectGene(GENES, ['error', 'protocol'], {
+      preferredGeneId: 'gene_optimize',
+    });
+    // gene_optimize matches 'protocol' so it qualifies as a candidate
+    // With preference, it should be selected even if gene_repair scores higher
+    assert.equal(result.selected.id, 'gene_optimize');
+  });
+});
+
+describe('selectCapsule', () => {
+  it('selects capsule matching signals', () => {
+    const result = selectCapsule(CAPSULES, ['log_error', 'exception']);
+    assert.equal(result.id, 'capsule_1');
+  });
+
+  it('returns null when no triggers match', () => {
+    const result = selectCapsule(CAPSULES, ['unrelated']);
+    assert.equal(result, null);
+  });
+});
+
+describe('selectGeneAndCapsule', () => {
+  it('returns selected gene, capsule candidates, and selector decision', () => {
+    const result = selectGeneAndCapsule({
+      genes: GENES,
+      capsules: CAPSULES,
+      signals: ['error', 'log_error'],
+      memoryAdvice: null,
+      driftEnabled: false,
+    });
+    assert.ok(result.selectedGene);
+    assert.ok(result.selector);
+    assert.ok(result.selector.selected);
+    assert.ok(Array.isArray(result.selector.reason));
+  });
+});