diff --git a/lib/helpers/config.js b/lib/helpers/config.js
index 4af8ebed1..8d4def32b 100644
--- a/lib/helpers/config.js
+++ b/lib/helpers/config.js
@@ -55,14 +55,50 @@ const validateDomainIsSet = (config) => {
 };
 
 /**
- * @desc Warn if JWT secret is still set to the default placeholder value.
+ * Known default / placeholder JWT secret values that must never be used in
+ * non-dev environments.  Extend this list when a new downstream project is
+ * bootstrapped with its own placeholder.
+ */
+const JWT_DEFAULT_SECRETS = new Set([
+  'WaosSecretKeyExampleToChnageAbsolutely', // devkit upstream placeholder
+  'TrawlNodeDevSecret', // trawl downstream placeholder
+  'ComesNodeDevSecret', // comes downstream placeholder
+  'MontaineNodeDevSecret', // montaine downstream placeholder
+  'PierrebNodeDevSecret', // pierreb downstream placeholder
+  'IsmNodeDevSecret', // ism downstream placeholder
+]);
+
+/**
+ * Safe envs where a weak / default secret is tolerated (warn only).
+ */
+const DEV_ENVS = new Set(['development', 'test', 'local']);
+
+/**
+ * @desc Validate JWT secret strength.
+ *  - In non-dev/non-test environments: throw (fail-closed) when the secret is
+ *    empty, shorter than 32 chars, or matches a known default placeholder.
+ *  - In dev/test/local: keep the existing console.log warn so local and CI
+ *    boots still succeed.
  * @param {object} config - application configuration object
  * @returns {void}
  */
 const validateJwtSecret = (config) => {
-  if (config.jwt && config.jwt.secret === 'WaosSecretKeyExampleToChnageAbsolutely') {
-    console.log(chalk.red('+ Important warning: JWT secret is set to the default value. It should be changed in production via DEVKIT_NODE_jwt_secret.'));
+  const secret = config.jwt?.secret;
+  const env = process.env.NODE_ENV ?? 'development';
+
+  const isWeak = !secret || secret.trim() === '' || secret.length < 32 || JWT_DEFAULT_SECRETS.has(secret);
+
+  if (!isWeak) return; // strong secret — nothing to do
+
+  const message = '+ Important warning: JWT secret is empty, too short (< 32 chars), or set to a known default placeholder. Set a strong secret via DEVKIT_NODE_jwt_secret.';
+
+  if (DEV_ENVS.has(env)) {
+    console.log(chalk.red(message));
+    return;
   }
+
+  // Non-dev environments: fail closed — crash loud rather than run insecurely.
+  throw new Error(`[security] validateJwtSecret: ${message}`);
 };
 
 /**
diff --git a/lib/helpers/tests/config.validateJwtSecret.unit.tests.js b/lib/helpers/tests/config.validateJwtSecret.unit.tests.js
new file mode 100644
index 000000000..4fa558420
--- /dev/null
+++ b/lib/helpers/tests/config.validateJwtSecret.unit.tests.js
@@ -0,0 +1,126 @@
+/**
+ * Unit tests for validateJwtSecret in config helper.
+ *
+ * Behaviour matrix:
+ *  - prod env  + empty secret          → throws
+ *  - prod env  + short secret (<32)    → throws
+ *  - prod env  + devkit placeholder    → throws
+ *  - prod env  + downstream default    → throws
+ *  - prod env  + strong secret (≥32)   → no throw, no warn
+ *  - dev  env  + default secret        → console.log warn, no throw
+ *  - test env  + default secret        → console.log warn, no throw
+ *  - local env + default secret        → console.log warn, no throw
+ */
+import { jest, describe, test, expect, beforeEach, afterEach } from '@jest/globals';
+
+// We import the module directly (no mocking needed — pure utility).
+import configHelper from '../config.js';
+
+const { validateJwtSecret } = configHelper;
+
+const STRONG_SECRET = 'a'.repeat(32); // exactly 32 chars, non-default
+const DEVKIT_PLACEHOLDER = 'WaosSecretKeyExampleToChnageAbsolutely';
+const DOWNSTREAM_DEFAULT = 'TrawlNodeDevSecret'; // known downstream placeholder (< 32 chars too)
+const SHORT_SECRET = 'tooshort'; // < 32 chars, not a known default
+
+describe('config.validateJwtSecret', () => {
+  let consoleLogSpy;
+  const originalEnv = process.env.NODE_ENV;
+
+  beforeEach(() => {
+    consoleLogSpy = jest.spyOn(console, 'log').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    consoleLogSpy.mockRestore();
+    process.env.NODE_ENV = originalEnv;
+  });
+
+  // ---- prod: fail-closed ------------------------------------------------
+
+  test('prod + undefined secret → throws', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({ jwt: { secret: undefined } })).toThrow();
+  });
+
+  test('prod + empty string secret → throws', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({ jwt: { secret: '' } })).toThrow();
+  });
+
+  test('prod + whitespace-only secret → throws', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({ jwt: { secret: '   ' } })).toThrow();
+  });
+
+  test('prod + short secret (< 32 chars) → throws', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({ jwt: { secret: SHORT_SECRET } })).toThrow();
+  });
+
+  test('prod + devkit placeholder → throws', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({ jwt: { secret: DEVKIT_PLACEHOLDER } })).toThrow();
+  });
+
+  test('prod + downstream default (TrawlNodeDevSecret) → throws', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({ jwt: { secret: DOWNSTREAM_DEFAULT } })).toThrow();
+  });
+
+  test('prod + no jwt key at all → throws', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({})).toThrow();
+  });
+
+  test('prod + strong secret (≥32 chars, non-default) → no throw, no warn', () => {
+    process.env.NODE_ENV = 'production';
+    expect(() => validateJwtSecret({ jwt: { secret: STRONG_SECRET } })).not.toThrow();
+    expect(consoleLogSpy).not.toHaveBeenCalled();
+  });
+
+  // ---- staging / other non-dev: also fail-closed -----------------------
+
+  test('staging env + short secret → throws', () => {
+    process.env.NODE_ENV = 'staging';
+    expect(() => validateJwtSecret({ jwt: { secret: SHORT_SECRET } })).toThrow();
+  });
+
+  // ---- dev/test/local: warn, never throw --------------------------------
+
+  test('dev env + devkit placeholder → warns (console.log), no throw', () => {
+    process.env.NODE_ENV = 'development';
+    expect(() => validateJwtSecret({ jwt: { secret: DEVKIT_PLACEHOLDER } })).not.toThrow();
+    expect(consoleLogSpy).toHaveBeenCalled();
+  });
+
+  test('dev env + empty secret → warns (console.log), no throw', () => {
+    process.env.NODE_ENV = 'development';
+    expect(() => validateJwtSecret({ jwt: { secret: '' } })).not.toThrow();
+    expect(consoleLogSpy).toHaveBeenCalled();
+  });
+
+  test('dev env + short secret → warns (console.log), no throw', () => {
+    process.env.NODE_ENV = 'development';
+    expect(() => validateJwtSecret({ jwt: { secret: SHORT_SECRET } })).not.toThrow();
+    expect(consoleLogSpy).toHaveBeenCalled();
+  });
+
+  test('test env + devkit placeholder → warns (console.log), no throw', () => {
+    process.env.NODE_ENV = 'test';
+    expect(() => validateJwtSecret({ jwt: { secret: DEVKIT_PLACEHOLDER } })).not.toThrow();
+    expect(consoleLogSpy).toHaveBeenCalled();
+  });
+
+  test('local env + devkit placeholder → warns (console.log), no throw', () => {
+    process.env.NODE_ENV = 'local';
+    expect(() => validateJwtSecret({ jwt: { secret: DEVKIT_PLACEHOLDER } })).not.toThrow();
+    expect(consoleLogSpy).toHaveBeenCalled();
+  });
+
+  test('dev env + strong secret → no throw, no warn', () => {
+    process.env.NODE_ENV = 'development';
+    expect(() => validateJwtSecret({ jwt: { secret: STRONG_SECRET } })).not.toThrow();
+    expect(consoleLogSpy).not.toHaveBeenCalled();
+  });
+});
diff --git a/modules/home/services/home.service.js b/modules/home/services/home.service.js
index e3f2fb018..0b8413182 100644
--- a/modules/home/services/home.service.js
+++ b/modules/home/services/home.service.js
@@ -74,12 +74,22 @@ const getReadinessStatus = () => {
   });
 
   // security — JWT secret
+  // Re-use the same weakness predicate as validateJwtSecret (config helper):
+  //   empty / whitespace / < 32 chars / known default placeholder.
+  const JWT_DEFAULTS = new Set([
+    'WaosSecretKeyExampleToChnageAbsolutely',
+    'TrawlNodeDevSecret',
+    'ComesNodeDevSecret',
+    'MontaineNodeDevSecret',
+    'PierrebNodeDevSecret',
+    'IsmNodeDevSecret',
+  ]);
   const jwtSecret = config.jwt?.secret;
-  const jwtInsecure = !jwtSecret || jwtSecret.trim() === '' || jwtSecret === 'WaosSecretKeyExampleToChnageAbsolutely';
+  const jwtInsecure = !jwtSecret || jwtSecret.trim() === '' || jwtSecret.length < 32 || JWT_DEFAULTS.has(jwtSecret);
   checks.push({
     category: 'security',
     status: jwtInsecure ? 'warning' : 'ok',
-    message: jwtInsecure ? 'JWT secret is missing or default — change it before production' : 'JWT secret is custom',
+    message: jwtInsecure ? 'JWT secret is missing, too short (< 32 chars), or a known default — change it before production' : 'JWT secret is custom',
   });
 
   // auth — OAuth providers
diff --git a/modules/home/tests/home.integration.tests.js b/modules/home/tests/home.integration.tests.js
index c89e4a12e..6fd5c110d 100644
--- a/modules/home/tests/home.integration.tests.js
+++ b/modules/home/tests/home.integration.tests.js
@@ -190,7 +190,7 @@ describe('Home integration tests:', () => {
       const mailerSpy = jest.spyOn(mailer, 'isConfigured').mockReturnValue(true);
       try {
         config.domain = 'example.com';
-        config.jwt.secret = 'a-real-custom-secret-key';
+        config.jwt.secret = 'a-real-custom-secret-key-well-over-32-characters-long';
         config.oAuth = { google: { clientID: 'google-id' }, apple: { clientID: 'apple-id' } };
         config.stripe = { secretKey: 'sk_test_123' };
         config.analytics = { posthog: { key: 'phk_123', errorTracking: true } };