diff --git a/packages/core/src/__tests__/middleware/bootstrap-security.test.ts b/packages/core/src/__tests__/middleware/bootstrap-security.test.ts
new file mode 100644
index 000000000..aa05b108e
--- /dev/null
+++ b/packages/core/src/__tests__/middleware/bootstrap-security.test.ts
@@ -0,0 +1,138 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { verifySecurityConfig } from '../../middleware/bootstrap'
+
+describe('verifySecurityConfig', () => {
+  let warnSpy: ReturnType<typeof vi.spyOn>
+
+  beforeEach(() => {
+    warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {})
+  })
+
+  afterEach(() => {
+    warnSpy.mockRestore()
+  })
+
+  it('should not warn when all config is properly set', () => {
+    verifySecurityConfig({
+      DB: {} as D1Database,
+      KV: {} as KVNamespace,
+      JWT_SECRET: 'a-strong-random-secret-value-here',
+      CORS_ORIGINS: 'https://mysite.com',
+      ENVIRONMENT: 'production',
+    })
+
+    expect(warnSpy).not.toHaveBeenCalled()
+  })
+
+  it('should warn when JWT_SECRET is not set', () => {
+    verifySecurityConfig({
+      DB: {} as D1Database,
+      KV: {} as KVNamespace,
+      CORS_ORIGINS: 'http://localhost:8787',
+      ENVIRONMENT: 'development',
+    })
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('JWT_SECRET is not set')
+    )
+  })
+
+  it('should warn when JWT_SECRET contains the default value', () => {
+    verifySecurityConfig({
+      DB: {} as D1Database,
+      KV: {} as KVNamespace,
+      JWT_SECRET: 'your-super-secret-jwt-key-change-in-production',
+      CORS_ORIGINS: 'http://localhost:8787',
+      ENVIRONMENT: 'development',
+    })
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('JWT_SECRET contains the default value')
+    )
+  })
+
+  it('should warn when CORS_ORIGINS is not set', () => {
+    verifySecurityConfig({
+      DB: {} as D1Database,
+      KV: {} as KVNamespace,
+      JWT_SECRET: 'a-strong-secret',
+      ENVIRONMENT: 'development',
+    })
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('CORS_ORIGINS is not set')
+    )
+  })
+
+  it('should warn when ENVIRONMENT is not set', () => {
+    verifySecurityConfig({
+      DB: {} as D1Database,
+      KV: {} as KVNamespace,
+      JWT_SECRET: 'a-strong-secret',
+      CORS_ORIGINS: 'http://localhost:8787',
+    })
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('ENVIRONMENT is not set')
+    )
+  })
+
+  it('should log multiple warnings when multiple items are missing', () => {
+    verifySecurityConfig({
+      DB: {} as D1Database,
+      KV: {} as KVNamespace,
+    })
+
+    expect(warnSpy).toHaveBeenCalledTimes(3)
+  })
+
+  it('should throw in production when JWT_SECRET is not set', () => {
+    expect(() => {
+      verifySecurityConfig({
+        DB: {} as D1Database,
+        KV: {} as KVNamespace,
+        CORS_ORIGINS: 'https://mysite.com',
+        ENVIRONMENT: 'production',
+      })
+    }).toThrow('[SonicJS Security] CRITICAL')
+  })
+
+  it('should throw in production when JWT_SECRET is the default value', () => {
+    expect(() => {
+      verifySecurityConfig({
+        DB: {} as D1Database,
+        KV: {} as KVNamespace,
+        JWT_SECRET: 'your-super-secret-jwt-key-change-in-production',
+        CORS_ORIGINS: 'https://mysite.com',
+        ENVIRONMENT: 'production',
+      })
+    }).toThrow('[SonicJS Security] CRITICAL')
+  })
+
+  it('should NOT throw in production when JWT_SECRET is properly set', () => {
+    verifySecurityConfig({
+      DB: {} as D1Database,
+      KV: {} as KVNamespace,
+      JWT_SECRET: 'a-strong-random-secret-value',
+      ENVIRONMENT: 'production',
+    })
+
+    // Should warn about CORS_ORIGINS but not throw
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('CORS_ORIGINS is not set')
+    )
+  })
+
+  it('should NOT throw in development even when JWT_SECRET is missing', () => {
+    expect(() => {
+      verifySecurityConfig({
+        DB: {} as D1Database,
+        KV: {} as KVNamespace,
+        ENVIRONMENT: 'development',
+      })
+    }).not.toThrow()
+
+    // Should still warn
+    expect(warnSpy).toHaveBeenCalled()
+  })
+})
diff --git a/packages/core/src/middleware/bootstrap.ts b/packages/core/src/middleware/bootstrap.ts
index 5b6ebee5f..4fbdbd588 100644
--- a/packages/core/src/middleware/bootstrap.ts
+++ b/packages/core/src/middleware/bootstrap.ts
@@ -7,11 +7,71 @@ import type { SonicJSConfig } from "../app";
 type Bindings = {
   DB: D1Database;
   KV: KVNamespace;
+  JWT_SECRET?: string;
+  CORS_ORIGINS?: string;
+  ENVIRONMENT?: string;
 };
 
 // Track if bootstrap has been run in this worker instance
 let bootstrapComplete = false;
 
+/**
+ * Verify security-critical environment configuration at startup.
+ * Logs warnings in development, throws in production to prevent
+ * insecure deployments from silently running.
+ */
+export function verifySecurityConfig(env: Bindings): void {
+  const warnings: string[] = [];
+
+  // Check JWT secret
+  if (!env.JWT_SECRET) {
+    warnings.push(
+      "JWT_SECRET is not set — using hardcoded fallback. Set via `wrangler secret put JWT_SECRET`"
+    );
+  } else if (env.JWT_SECRET.includes("change-in-production")) {
+    warnings.push(
+      "JWT_SECRET contains the default value — tokens are forgeable. Generate a strong random secret"
+    );
+  }
+
+  // Check CORS origins
+  if (!env.CORS_ORIGINS) {
+    warnings.push(
+      "CORS_ORIGINS is not set — all cross-origin API requests will be rejected"
+    );
+  }
+
+  // Check environment designation
+  if (!env.ENVIRONMENT) {
+    warnings.push(
+      "ENVIRONMENT is not set — HSTS header will not be applied. Set to \"production\" or \"development\""
+    );
+  }
+
+  if (warnings.length === 0) {
+    return;
+  }
+
+  const isProduction = env.ENVIRONMENT === "production";
+
+  for (const warning of warnings) {
+    console.warn(`[SonicJS Security] ${warning}`);
+  }
+
+  if (isProduction) {
+    // In production, a missing or default JWT_SECRET is a hard failure —
+    // every token issued would be forgeable by anyone reading the source code.
+    const hasCritical =
+      !env.JWT_SECRET || env.JWT_SECRET.includes("change-in-production");
+    if (hasCritical) {
+      throw new Error(
+        "[SonicJS Security] CRITICAL: Production deployment is missing a secure JWT_SECRET. " +
+          "Set it via `wrangler secret put JWT_SECRET` before deploying."
+      );
+    }
+  }
+}
+
 /**
  * Bootstrap middleware that ensures system initialization
  * Runs once per worker instance
@@ -77,6 +137,10 @@ export function bootstrapMiddleware(config: SonicJSConfig = {}) {
       // Don't prevent the app from starting, but log the error
     }
 
+    // 4. Verify security configuration (outside try/catch so critical
+    // errors in production propagate and prevent insecure deployments)
+    verifySecurityConfig(c.env as Bindings);
+
     return next();
   };
 }
diff --git a/packages/core/src/middleware/index.ts b/packages/core/src/middleware/index.ts
index 96abeb470..1c25cf15b 100644
--- a/packages/core/src/middleware/index.ts
+++ b/packages/core/src/middleware/index.ts
@@ -8,7 +8,7 @@
  */
 
 // Bootstrap middleware
-export { bootstrapMiddleware } from './bootstrap'
+export { bootstrapMiddleware, verifySecurityConfig } from './bootstrap'
 
 // Auth middleware
 export { AuthManager, requireAuth, requireRole, optionalAuth } from './auth'