diff --git a/plugins/llm-security/scanners/attack-simulator.mjs b/plugins/llm-security/scanners/attack-simulator.mjs
index 61b7549..6572796 100644
--- a/plugins/llm-security/scanners/attack-simulator.mjs
+++ b/plugins/llm-security/scanners/attack-simulator.mjs
@@ -629,6 +629,58 @@ function formatAdaptiveJson(fixedResults, adaptiveResults, durationMs) {
   return base;
 }
 
+// ---------------------------------------------------------------------------
+// Benchmark report formatting (v6.0)
+// ---------------------------------------------------------------------------
+
+function formatBenchmarkJson(fixedResults, adaptiveResults, durationMs) {
+  const total = fixedResults.length;
+  const blocked = fixedResults.filter(r => r.passed).length;
+  const bypassed = total - blocked;
+  const blockRate = total > 0 ? blocked / total : 0;
+
+  // Per-category breakdown
+  const categories = {};
+  for (const r of fixedResults) {
+    if (!categories[r.category]) categories[r.category] = { scenarios: 0, blocked: 0, bypassed: 0, block_rate: 0 };
+    categories[r.category].scenarios++;
+    if (r.passed) categories[r.category].blocked++;
+    else categories[r.category].bypassed++;
+  }
+  for (const cat of Object.values(categories)) {
+    cat.block_rate = cat.scenarios > 0 ? cat.blocked / cat.scenarios : 0;
+  }
+
+  // Adaptive stats
+  const adaptiveBypasses = adaptiveResults.filter(r => r.bypassed).length;
+  const adaptiveTotal = blocked * 5; // 5 mutation rounds per blocked scenario
+  const adaptiveBlockRate = adaptiveTotal > 0 ? 1 - (adaptiveBypasses / adaptiveTotal) : 1;
+
+  return {
+    meta: {
+      timestamp: new Date().toISOString(),
+      version: '6.0.0',
+      node_version: process.version,
+      scenarios_total: total,
+      adaptive_rounds: 5,
+      duration_ms: durationMs,
+      mode: 'benchmark',
+    },
+    summary: {
+      block_rate: Math.round(blockRate * 1000) / 1000,
+      adaptive_block_rate: Math.round(adaptiveBlockRate * 1000) / 1000,
+      total_blocked: blocked,
+      total_bypassed: bypassed,
+      adaptive_bypasses: adaptiveBypasses,
+    },
+    categories,
+    methodology: `Data-driven simulation using ${total} scenarios across ${Object.keys(categories).length} categories. ` +
+      'Fixed mode tests each scenario with original payloads. Adaptive mode applies 5 mutation rounds ' +
+      '(homoglyph, encoding, zero-width, case alternation, synonym) to each blocked scenario. ' +
+      'Block rate = blocked / total. Adaptive block rate = 1 - (adaptive_bypasses / (blocked * rounds)).',
+  };
+}
+
 // ---------------------------------------------------------------------------
 // Cleanup & CLI
 // ---------------------------------------------------------------------------
@@ -650,6 +702,7 @@ async function main() {
   const jsonMode = args.includes('--json');
   const verbose = args.includes('--verbose');
   const adaptive = args.includes('--adaptive');
+  const benchmark = args.includes('--benchmark');
 
   const valid = ['secrets', 'destructive', 'supply-chain', 'prompt-injection',
     'pathguard', 'mcp-output', 'session-trifecta', 'hybrid',
@@ -662,6 +715,46 @@ async function main() {
   const scenarios = loadScenarios(category);
   if (!scenarios.length) { process.stderr.write('No scenarios found.\n'); process.exit(1); }
 
+  // Benchmark mode: run all scenarios in fixed + adaptive, produce structured report
+  if (benchmark) {
+    if (!jsonMode) process.stderr.write(`Benchmark: running ${scenarios.length} scenarios (fixed + adaptive)...\n`);
+    const start = Date.now();
+    cleanupSessionState();
+
+    // Fixed run
+    const fixedResults = [];
+    for (const s of scenarios) {
+      const r = await runScenario(s);
+      fixedResults.push(r);
+    }
+
+    // Adaptive run on blocked scenarios
+    const adaptiveResults = [];
+    const blockedScenarios = scenarios.filter((_, i) => fixedResults[i].passed);
+    if (blockedScenarios.length > 0) {
+      const { adaptiveResults: ar } = await runAdaptive(blockedScenarios, false, true);
+      adaptiveResults.push(...ar);
+    }
+
+    cleanupSessionState();
+    const dur = Date.now() - start;
+    const report = formatBenchmarkJson(fixedResults, adaptiveResults, dur);
+
+    if (jsonMode) {
+      process.stdout.write(JSON.stringify(report, null, 2) + '\n');
+    } else {
+      // Human-readable summary to stderr, JSON to stdout
+      const s = report.summary;
+      process.stderr.write(`\nBenchmark Results:\n`);
+      process.stderr.write(`  Block rate (fixed):    ${(s.block_rate * 100).toFixed(1)}% (${s.total_blocked}/${scenarios.length})\n`);
+      process.stderr.write(`  Block rate (adaptive): ${(s.adaptive_block_rate * 100).toFixed(1)}%\n`);
+      process.stderr.write(`  Adaptive bypasses:     ${s.adaptive_bypasses}\n`);
+      process.stderr.write(`  Duration:              ${dur}ms\n`);
+      process.stdout.write(JSON.stringify(report, null, 2) + '\n');
+    }
+    process.exit(0);
+  }
+
   if (adaptive) {
     if (!jsonMode) process.stderr.write(`Running ${scenarios.length} attack scenarios in adaptive mode...\n`);
     const start = Date.now();
@@ -712,6 +805,8 @@ export {
   mutateHomoglyph, mutateEncoding, mutateZeroWidth, mutateCaseAlternation, mutateSynonym,
   MUTATION_FNS, applyMutationDeep, runAdaptiveMutations, loadMutationRules,
   formatAdaptiveReport, formatAdaptiveJson,
+  // Benchmark export (v6.0)
+  formatBenchmarkJson,
 };
 
 const isDirectRun = process.argv[1] && resolve(process.argv[1]) === __filename;
diff --git a/plugins/llm-security/tests/scanners/benchmark.test.mjs b/plugins/llm-security/tests/scanners/benchmark.test.mjs
new file mode 100644
index 0000000..ed53b0f
--- /dev/null
+++ b/plugins/llm-security/tests/scanners/benchmark.test.mjs
@@ -0,0 +1,69 @@
+// benchmark.test.mjs — Tests for --benchmark mode in attack-simulator.mjs
+// Verifies: flag parsing, report schema, block rates are valid numbers
+
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { resolve } from 'node:path';
+import { execFile } from 'node:child_process';
+import { fileURLToPath } from 'node:url';
+import { formatBenchmarkJson } from '../../scanners/attack-simulator.mjs';
+
+const __dirname = fileURLToPath(new URL('.', import.meta.url));
+const SIMULATOR = resolve(__dirname, '../../scanners/attack-simulator.mjs');
+
+function run(args) {
+  return new Promise((resolve, reject) => {
+    execFile('node', [SIMULATOR, ...args], { timeout: 120_000 }, (err, stdout, stderr) => {
+      resolve({ err, stdout, stderr, code: err?.code ?? 0 });
+    });
+  });
+}
+
+describe('attack-simulator --benchmark', () => {
+  it('--benchmark --json produces valid JSON with required fields', async () => {
+    const { stdout } = await run(['--benchmark', '--json']);
+    const d = JSON.parse(stdout);
+
+    // Meta fields
+    assert.ok(d.meta, 'Should have meta');
+    assert.ok(d.meta.timestamp, 'Should have timestamp');
+    assert.ok(d.meta.version, 'Should have version');
+    assert.ok(d.meta.node_version, 'Should have node_version');
+    assert.equal(typeof d.meta.scenarios_total, 'number');
+
+    // Summary fields
+    assert.ok(d.summary, 'Should have summary');
+    assert.equal(typeof d.summary.block_rate, 'number');
+    assert.ok(d.summary.block_rate >= 0 && d.summary.block_rate <= 1, 'block_rate should be 0-1');
+    assert.equal(typeof d.summary.adaptive_block_rate, 'number');
+    assert.ok(d.summary.adaptive_block_rate >= 0 && d.summary.adaptive_block_rate <= 1);
+    assert.equal(typeof d.summary.total_blocked, 'number');
+    assert.equal(typeof d.summary.total_bypassed, 'number');
+
+    // Categories
+    assert.ok(d.categories, 'Should have categories');
+    assert.equal(typeof d.categories, 'object');
+
+    // Methodology
+    assert.ok(d.methodology, 'Should have methodology string');
+    assert.equal(typeof d.methodology, 'string');
+  });
+
+  it('formatBenchmarkJson returns valid structure from mock data', () => {
+    const mockFixed = [
+      { id: 'S01', name: 'test', category: 'secrets', passed: true, detail: '' },
+      { id: 'S02', name: 'test2', category: 'secrets', passed: false, detail: 'gap' },
+    ];
+    const mockAdaptive = [
+      { scenarioId: 'S01', mutation: 'homoglyph', round: 2, bypassed: true },
+    ];
+    const result = formatBenchmarkJson(mockFixed, mockAdaptive, 1000);
+
+    assert.equal(result.meta.mode, 'benchmark');
+    assert.equal(result.summary.block_rate, 0.5);
+    assert.equal(typeof result.summary.adaptive_block_rate, 'number');
+    assert.ok(result.categories.secrets);
+    assert.equal(result.categories.secrets.scenarios, 2);
+    assert.equal(result.categories.secrets.blocked, 1);
+  });
+});