diff --git a/scripts/no-telemetry-growthbook-stub.test.ts b/scripts/no-telemetry-growthbook-stub.test.ts
new file mode 100644
index 00000000..da0d33e1
--- /dev/null
+++ b/scripts/no-telemetry-growthbook-stub.test.ts
@@ -0,0 +1,146 @@
+import { afterAll, beforeEach, describe, expect, test } from 'bun:test'
+import { mkdirSync, readFileSync, rmSync, unlinkSync, writeFileSync } from 'node:fs'
+import { join } from 'node:path'
+import { tmpdir } from 'node:os'
+
+// ---------------------------------------------------------------------------
+// Setup: extract the growthbook stub from no-telemetry-plugin.ts, write it to
+// a temp .mjs file, and dynamically import it so we can test the real code
+// that gets bundled.
+// ---------------------------------------------------------------------------
+
+const pluginSource = readFileSync(join(__dirname, 'no-telemetry-plugin.ts'), 'utf-8')
+const stubMatch = pluginSource.match(/'services\/analytics\/growthbook': `([\s\S]*?)`/)
+if (!stubMatch) throw new Error('Could not extract growthbook stub from no-telemetry-plugin.ts')
+
+const testDir = join(tmpdir(), `growthbook-stub-test-${process.pid}`)
+const stubFile = join(testDir, 'growthbook-stub.mjs')
+const flagsFile = join(testDir, 'test-flags.json')
+
+mkdirSync(testDir, { recursive: true })
+writeFileSync(stubFile, stubMatch[1])
+
+// Point the stub at our test flags file (checked by _loadFlags on first access)
+process.env.CLAUDE_FEATURE_FLAGS_FILE = flagsFile
+
+const stub = await import(stubFile)
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+describe('growthbook stub — local feature flag overrides', () => {
+  beforeEach(() => {
+    stub.resetGrowthBook()
+    try { unlinkSync(flagsFile) } catch { /* may not exist */ }
+  })
+
+  afterAll(() => {
+    rmSync(testDir, { recursive: true, force: true })
+    delete process.env.CLAUDE_FEATURE_FLAGS_FILE
+  })
+
+  // ── File absent ──────────────────────────────────────────────────
+
+  test('returns defaultValue when flags file is absent', () => {
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 42)).toBe(42)
+  })
+
+  test('getAllGrowthBookFeatures returns {} when file is absent', () => {
+    expect(stub.getAllGrowthBookFeatures()).toEqual({})
+  })
+
+  // ── Valid JSON object ────────────────────────────────────────────
+
+  test('loads and returns values from a valid JSON file', () => {
+    writeFileSync(flagsFile, JSON.stringify({ tengu_foo: true, tengu_bar: 'hello' }))
+
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', false)).toBe(true)
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_bar', 'default')).toBe('hello')
+  })
+
+  test('returns defaultValue for keys not present in the file', () => {
+    writeFileSync(flagsFile, JSON.stringify({ tengu_foo: true }))
+
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_missing', 99)).toBe(99)
+  })
+
+  test('getAllGrowthBookFeatures returns the full flags object', () => {
+    const flags = { tengu_a: true, tengu_b: false, tengu_c: 42 }
+    writeFileSync(flagsFile, JSON.stringify(flags))
+
+    expect(stub.getAllGrowthBookFeatures()).toEqual(flags)
+  })
+
+  // ── Malformed / non-object JSON ──────────────────────────────────
+
+  test('falls back to defaults on malformed JSON', () => {
+    writeFileSync(flagsFile, '{not valid json!!!')
+
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'fallback')).toBe('fallback')
+  })
+
+  test('falls back to defaults when JSON is a primitive (true)', () => {
+    writeFileSync(flagsFile, 'true')
+
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'fallback')).toBe('fallback')
+  })
+
+  test('falls back to defaults when JSON is an array', () => {
+    writeFileSync(flagsFile, '["a", "b"]')
+
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'fallback')).toBe('fallback')
+  })
+
+  // ── Cache invalidation ───────────────────────────────────────────
+
+  test('resetGrowthBook clears cache so the file is re-read', () => {
+    writeFileSync(flagsFile, JSON.stringify({ tengu_foo: 'first' }))
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'x')).toBe('first')
+
+    // Update the file — cached value is still 'first'
+    writeFileSync(flagsFile, JSON.stringify({ tengu_foo: 'second' }))
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'x')).toBe('first')
+
+    // After reset, the new value is picked up
+    stub.resetGrowthBook()
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'x')).toBe('second')
+  })
+
+  test('refreshGrowthBookFeatures clears cache', async () => {
+    writeFileSync(flagsFile, JSON.stringify({ tengu_foo: 'v1' }))
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'x')).toBe('v1')
+
+    writeFileSync(flagsFile, JSON.stringify({ tengu_foo: 'v2' }))
+    await stub.refreshGrowthBookFeatures()
+    expect(stub.getFeatureValue_CACHED_MAY_BE_STALE('tengu_foo', 'x')).toBe('v2')
+  })
+
+  // ── Multiple getter variants ─────────────────────────────────────
+
+  test('all getter functions read from local flags', async () => {
+    writeFileSync(flagsFile, JSON.stringify({ tengu_gate: true, tengu_config: { a: 1 } }))
+
+    expect(await stub.getFeatureValue_DEPRECATED('tengu_gate', false)).toBe(true)
+    stub.resetGrowthBook()
+    expect(stub.getFeatureValue_CACHED_WITH_REFRESH('tengu_gate', false)).toBe(true)
+    stub.resetGrowthBook()
+    expect(stub.checkStatsigFeatureGate_CACHED_MAY_BE_STALE('tengu_gate')).toBe(true)
+    stub.resetGrowthBook()
+    expect(await stub.checkGate_CACHED_OR_BLOCKING('tengu_gate')).toBe(true)
+    stub.resetGrowthBook()
+    expect(await stub.getDynamicConfig_BLOCKS_ON_INIT('tengu_config', {})).toEqual({ a: 1 })
+    stub.resetGrowthBook()
+    expect(stub.getDynamicConfig_CACHED_MAY_BE_STALE('tengu_config', {})).toEqual({ a: 1 })
+  })
+
+  // ── Security gate ────────────────────────────────────────────────
+
+  test('checkSecurityRestrictionGate always returns false regardless of flags', async () => {
+    writeFileSync(flagsFile, JSON.stringify({
+      tengu_disable_bypass_permissions_mode: true,
+    }))
+
+    expect(await stub.checkSecurityRestrictionGate()).toBe(false)
+  })
+})
diff --git a/scripts/no-telemetry-plugin.ts b/scripts/no-telemetry-plugin.ts
index c0ad74d8..97fb54a3 100644
--- a/scripts/no-telemetry-plugin.ts
+++ b/scripts/no-telemetry-plugin.ts
@@ -34,28 +34,55 @@ export function _resetForTesting() {}
 `,
 
 	'services/analytics/growthbook': `
+import _fs from 'node:fs';
+import _path from 'node:path';
+import _os from 'node:os';
+
+let _flags = undefined;
+
+function _loadFlags() {
+  if (_flags !== undefined) return;
+  try {
+    const flagsPath = process.env.CLAUDE_FEATURE_FLAGS_FILE
+      || _path.join(_os.homedir(), '.claude', 'feature-flags.json');
+    const parsed = JSON.parse(_fs.readFileSync(flagsPath, 'utf-8'));
+    _flags = (parsed && typeof parsed === 'object' && !Array.isArray(parsed)) ? parsed : null;
+  } catch {
+    _flags = null;
+  }
+}
+
+function _getFlagValue(key, defaultValue) {
+  _loadFlags();
+  if (_flags != null && Object.hasOwn(_flags, key)) return _flags[key];
+  return defaultValue;
+}
+
 const noop = () => {};
 export function onGrowthBookRefresh() { return noop; }
 export function hasGrowthBookEnvOverride() { return false; }
-export function getAllGrowthBookFeatures() { return {}; }
+export function getAllGrowthBookFeatures() { _loadFlags(); return _flags || {}; }
 export function getGrowthBookConfigOverrides() { return {}; }
 export function setGrowthBookConfigOverride() {}
 export function clearGrowthBookConfigOverrides() {}
 export function getApiBaseUrlHost() { return undefined; }
 export const initializeGrowthBook = async () => null;
-export async function getFeatureValue_DEPRECATED(feature, defaultValue) { return defaultValue; }
-export function getFeatureValue_CACHED_MAY_BE_STALE(feature, defaultValue) { return defaultValue; }
-export function getFeatureValue_CACHED_WITH_REFRESH(feature, defaultValue) { return defaultValue; }
-export function checkStatsigFeatureGate_CACHED_MAY_BE_STALE() { return false; }
-export async function checkSecurityRestrictionGate() { return false; }
-export async function checkGate_CACHED_OR_BLOCKING() { return false; }
+export async function getFeatureValue_DEPRECATED(feature, defaultValue) { return _getFlagValue(feature, defaultValue); }
+export function getFeatureValue_CACHED_MAY_BE_STALE(feature, defaultValue) { return _getFlagValue(feature, defaultValue); }
+export function getFeatureValue_CACHED_WITH_REFRESH(feature, defaultValue) { return _getFlagValue(feature, defaultValue); }
+export function checkStatsigFeatureGate_CACHED_MAY_BE_STALE(gate) { return Boolean(_getFlagValue(gate, false)); }
+// Security killswitch — always false in the open build. Anthropic uses this
+// gate to remotely disable bypassPermissions mode; exposing it via local flags
+// would let users accidentally lock themselves out of --dangerously-skip-permissions.
+export async function checkSecurityRestrictionGate(gate) { return false; }
+export async function checkGate_CACHED_OR_BLOCKING(gate) { return Boolean(_getFlagValue(gate, false)); }
 export function refreshGrowthBookAfterAuthChange() {}
-export function resetGrowthBook() {}
-export async function refreshGrowthBookFeatures() {}
+export function resetGrowthBook() { _flags = undefined; }
+export async function refreshGrowthBookFeatures() { _flags = undefined; }
 export function setupPeriodicGrowthBookRefresh() {}
 export function stopPeriodicGrowthBookRefresh() {}
-export async function getDynamicConfig_BLOCKS_ON_INIT(configName, defaultValue) { return defaultValue; }
-export function getDynamicConfig_CACHED_MAY_BE_STALE(configName, defaultValue) { return defaultValue; }
+export async function getDynamicConfig_BLOCKS_ON_INIT(configName, defaultValue) { return _getFlagValue(configName, defaultValue); }
+export function getDynamicConfig_CACHED_MAY_BE_STALE(configName, defaultValue) { return _getFlagValue(configName, defaultValue); }
 `,
 
 	'services/analytics/sink': `