diff --git a/packages/bots/telnyx/src/index.test.ts b/packages/bots/telnyx/src/index.test.ts
index 5976ec1d..2068b2a3 100644
--- a/packages/bots/telnyx/src/index.test.ts
+++ b/packages/bots/telnyx/src/index.test.ts
@@ -185,6 +185,50 @@ describe('bot-telnyx webhook behavior', () => {
     }
   });
 
+  it('rejects non-decimal-integer Telnyx webhook timestamps', async () => {
+    const keys = generateKeyPairSync('ed25519');
+    const publicKey = Buffer.from(keys.publicKey.export({ format: 'der', type: 'spki' })).toString('base64');
+    const handler = vi.fn();
+    const handle = await bot.register(ctx(), [{ match: { type: 'message' }, handle: handler }], {
+      from: '+15551234567',
+      webhookPort: 0,
+      publicKey,
+    }) as { close(): Promise<void>; port: number };
+
+    try {
+      const body = JSON.stringify({
+        data: {
+          event_type: 'message.received',
+          payload: { from: { phone_number: '+15559876543' }, text: 'hello' },
+        },
+      });
+      const now = Math.floor(Date.now() / 1000);
+      const invalidTimestamps = [
+        `${now}e0`,
+        `0x${now.toString(16)}`,
+        `${now}.5`,
+        ` ${now} `,
+        `+${now}`,
+      ];
+
+      for (const timestamp of invalidTimestamps) {
+        const response = await fetch(`http://127.0.0.1:${handle.port}/telnyx/messaging`, {
+          method: 'POST',
+          headers: {
+            'Content-Type': 'application/json',
+            'telnyx-timestamp': timestamp,
+            'telnyx-signature-ed25519': signature(keys.privateKey, timestamp, body),
+          },
+          body,
+        });
+        expect(response.status).toBe(403);
+      }
+      expect(handler).not.toHaveBeenCalled();
+    } finally {
+      await handle.close();
+    }
+  });
+
   it('falls back to the default signature tolerance for invalid config values', async () => {
     const keys = generateKeyPairSync('ed25519');
     const publicKey = Buffer.from(keys.publicKey.export({ format: 'der', type: 'spki' })).toString('base64');
diff --git a/packages/bots/telnyx/src/index.ts b/packages/bots/telnyx/src/index.ts
index e7de5913..7c45693f 100644
--- a/packages/bots/telnyx/src/index.ts
+++ b/packages/bots/telnyx/src/index.ts
@@ -302,8 +302,9 @@ function telnyxPublicKey(value: string): ReturnType<typeof createPublicKey> {
 }
 
 function validTimestamp(value: string, toleranceSeconds: number): boolean {
+  if (!/^\d+$/.test(value)) return false;
   const parsed = Number(value);
-  if (!Number.isFinite(parsed)) return false;
+  if (!Number.isSafeInteger(parsed)) return false;
   return Math.abs(Date.now() / 1000 - parsed) <= toleranceSeconds;
 }