diff --git a/src/protect/defaults.js b/src/protect/defaults.js
index 9c542f2..8ea627d 100644
--- a/src/protect/defaults.js
+++ b/src/protect/defaults.js
@@ -3,6 +3,12 @@
 // override per app via createProtection({ responseRules, egressRules }) or extend by
 // adding phase-tagged rules to the delivered bundle. Patterns are high-precision
 // (low false positive): structural markers a real secret has and normal content doesn't.
+//
+// Each rule carries a `prefilter`: cheap literal anchor(s) that MUST appear in the body for the
+// regex to have any chance of matching. The response screener runs the (expensive) regex only when
+// an anchor is present (case-insensitive), so a body with no candidate — the common case — skips
+// the scan entirely. This cuts CPU/latency and shrinks the regex/ReDoS surface. (Honored by the
+// response phase once the prefilter mechanism lands; a no-op before that.)
 
 // Response phase — secret / info exposure. Default action `redact` masks only the
 // offending span and still serves the page (a legit response that leaks one key gets
@@ -14,6 +20,7 @@ export const DEFAULT_RESPONSE_RULES = [
     phase: 'response',
     category: 'secret-exposure',
     action: 'redact',
+    prefilter: ['PRIVATE KEY'],
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/-----BEGIN (?:RSA |EC |OPENSSH |DSA |PGP )?PRIVATE KEY-----/' } }]
   },
   {
@@ -22,6 +29,7 @@ export const DEFAULT_RESPONSE_RULES = [
     phase: 'response',
     category: 'secret-exposure',
     action: 'redact',
+    prefilter: ['AKIA', 'ASIA'],
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/\\b(?:AKIA|ASIA)[0-9A-Z]{16}\\b/' } }]
   },
   {
@@ -30,14 +38,29 @@ export const DEFAULT_RESPONSE_RULES = [
     phase: 'response',
     category: 'secret-exposure',
     action: 'redact',
+    prefilter: ['AIza'],
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/\\bAIza[0-9A-Za-z_-]{35}\\b/' } }]
   },
+  {
+    id: 'resp-vendor-api-key',
+    title: 'Vendor API key / token in response body',
+    phase: 'response',
+    category: 'secret-exposure',
+    action: 'redact',
+    // High-signal, prefix-anchored provider tokens that never legitimately appear in a response
+    // body: Stripe (sk_live_/rk_live_), GitHub (gh[opsu]_ / github_pat_), GitLab (glpat-),
+    // Slack (xox[baprs]-), Anthropic (sk-ant-), Google OAuth (ya29.), npm (npm_). Trailing
+    // (?![0-9A-Za-z]) instead of \\b since some tokens end in - / _ .
+    prefilter: ['sk_live_', 'rk_live_', 'ghp_', 'gho_', 'ghs_', 'ghu_', 'github_pat_', 'glpat-', 'xox', 'sk-ant-', 'ya29.', 'npm_'],
+    rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/\\b(?:sk_live_[0-9A-Za-z]{16,}|rk_live_[0-9A-Za-z]{16,}|gh[opsu]_[0-9A-Za-z]{36}|github_pat_[0-9A-Za-z_]{60,}|glpat-[0-9A-Za-z_-]{20,}|xox[baprs]-[0-9A-Za-z-]{10,}|sk-ant-[0-9A-Za-z_-]{20,}|ya29\\.[0-9A-Za-z_-]{20,}|npm_[0-9A-Za-z]{36})(?![0-9A-Za-z])/' } }]
+  },
   {
     id: 'resp-jwt',
     title: 'JWT in response body',
     phase: 'response',
     category: 'secret-exposure',
     action: 'redact',
+    prefilter: ['eyJ'],
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/\\beyJ[A-Za-z0-9_-]{8,}\\.eyJ[A-Za-z0-9_-]{8,}\\.[A-Za-z0-9_-]{8,}\\b/' } }]
   },
   {
@@ -46,6 +69,7 @@ export const DEFAULT_RESPONSE_RULES = [
     phase: 'response',
     category: 'secret-exposure',
     action: 'redact',
+    prefilter: ['mongodb', 'postgres', 'mysql', 'redis', 'amqp'],
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/\\b(?:mongodb(?:\\+srv)?|postgres(?:ql)?|mysql|redis|amqps?):\\/\\/[^\\s:@\\/]+:[^\\s:@\\/]+@/i' } }]
   },
   {
@@ -54,6 +78,8 @@ export const DEFAULT_RESPONSE_RULES = [
     phase: 'response',
     category: 'info-exposure',
     action: 'redact',
+    // No prefilter: a Node stack frame has no single distinctive literal (` at ` is too common to
+    // gate on). The pattern is linearly bounded per line, so it runs on every screened body.
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/\\n\\s+at\\s+.+\\(.+:\\d+:\\d+\\)/' } }]
   },
   {
@@ -62,6 +88,7 @@ export const DEFAULT_RESPONSE_RULES = [
     phase: 'response',
     category: 'info-exposure',
     action: 'redact',
+    prefilter: ['SQLSTATE', 'Sequelize', 'ER_', 'ORA-', 'PG::', 'SQLITE_ERROR', 'SQL syntax'],
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/(SQLSTATE\\[[0-9A-Z]+\\]|SequelizeDatabaseError|ER_[A-Z_]+|ORA-\\d{5}|PG::[A-Za-z]+Error|SQLITE_ERROR|You have an error in your SQL syntax)/i' } }]
   },
   {
@@ -73,6 +100,7 @@ export const DEFAULT_RESPONSE_RULES = [
     // Multi-language exception/traceback signatures a normal API response never carries:
     // Python traceback, Java "Exception in thread", .NET System.*Exception, JVM stack frames,
     // Go goroutine dumps. (Node `at fn (file:line:col)` frames are handled by resp-stack-trace.)
+    prefilter: ['Traceback', 'Exception in thread', 'System.', 'goroutine ', '.java:', '.kt:', '.scala:', '.rb:', '.py:', '.cs:'],
     rule_v2: [{ parameter: 'response.body', match: { type: 'regex', value: '/(Traceback \\(most recent call last\\)|Exception in thread "|System\\.[A-Za-z.]+Exception|\\bat [\\w.$]+\\([\\w]+\\.(?:java|kt|scala|rb|py|cs):\\d+\\)|goroutine \\d+ \\[)/' } }]
   }
 ];
diff --git a/tests/protect/default-secret-rules.test.ts b/tests/protect/default-secret-rules.test.ts
new file mode 100644
index 0000000..6012e75
--- /dev/null
+++ b/tests/protect/default-secret-rules.test.ts
@@ -0,0 +1,61 @@
+import { describe, expect, it } from 'vitest';
+import { createProtection } from '../../src/protect/runtime.js';
+
+// The default response ruleset ships vendor API-key redaction, so a leaked provider token is masked
+// out of the box (no per-app rule authoring). Prefix-anchored + high-signal → low false-positive.
+//
+// NOTE: sample tokens are assembled from split fragments at runtime so no contiguous secret-shaped
+// literal appears in this source file (which would trip secret-scanning push protection). The
+// assembled string still matches the default rule's regex.
+
+const textResp = (body: string) =>
+  new Response(body, { status: 200, headers: { 'content-type': 'application/json' } });
+
+const body = (len: number) => 'x'.repeat(len);
+const SAMPLES: Record<string, string> = {
+  stripe: 'sk_' + 'live_' + body(24),
+  github: 'gh' + 'p_' + body(36),
+  githubPat: 'github' + '_pat_' + body(62),
+  gitlab: 'gl' + 'pat-' + body(24),
+  slack: 'xox' + 'b-' + '123456789012-' + body(12),
+  anthropic: 'sk-' + 'ant-' + body(30),
+  googleOAuth: 'ya' + '29.' + body(40),
+  npm: 'np' + 'm_' + body(36),
+};
+
+describe('default response rules — vendor API-key redaction', () => {
+  for (const [name, token] of Object.entries(SAMPLES)) {
+    it(`masks a leaked ${name} token by default`, async () => {
+      const p: any = await createProtection({ mode: 'block' }); // default response rules
+      const out = await p.screenResponse(textResp(JSON.stringify({ config: token })));
+      const masked = await out.text();
+      expect(masked.includes(token)).toBe(false);
+      expect(masked.includes('[REDACTED]')).toBe(true);
+    });
+  }
+
+  it('leaves an ordinary response untouched (no false positive)', async () => {
+    const p: any = await createProtection({ mode: 'block' });
+    const clean = JSON.stringify({ user: 'ada@example.com', note: 'the quick brown fox', id: 42 });
+    const out = await p.screenResponse(textResp(clean));
+    expect(await out.text()).toBe(clean);
+  });
+});
+
+describe('default response rules — performance / ReDoS safety', () => {
+  it('screens a large adversarial body in linear time (no catastrophic backtracking)', async () => {
+    const p: any = await createProtection({ mode: 'block' });
+    // ~280 KB (< the 512 KiB screen cap, so it IS screened) of near-miss inputs that stress the
+    // default regexes: repeated token prefixes, a long alnum run, and JWT- / stack-frame-ish noise.
+    const adversarial =
+      ('sk_' + 'live_').repeat(10000) +
+      'A'.repeat(100000) +
+      ('eyJ' + '_').repeat(10000) +
+      ('at x(y.js:1:').repeat(5000);
+    const start = performance.now();
+    const out = await p.screenResponse(textResp(adversarial));
+    await out.text();
+    const ms = performance.now() - start;
+    expect(ms).toBeLessThan(1000); // linear-time; a ReDoS pattern would blow far past this
+  });
+});