diff --git a/lib/gbrain-supabase-provision.ts b/lib/gbrain-supabase-provision.ts
index 7355e4abd..76eecbff4 100644
--- a/lib/gbrain-supabase-provision.ts
+++ b/lib/gbrain-supabase-provision.ts
@@ -411,6 +411,12 @@ async function cmdWait(ctx: Ctx, args: string[]): Promise<void> {
     else ref = arg;
   }
   if (!ref) die(ctx, 'wait: missing <ref>');
+  // Validate up front: NaN would make the deadline comparison below always
+  // false and the poll loop run forever (the bash predecessor errored here).
+  const timeoutSeconds = Number(timeout);
+  if (!Number.isFinite(timeoutSeconds) || timeoutSeconds < 0) {
+    die(ctx, 'wait: --timeout must be a non-negative integer (seconds)');
+  }
 
   requirePat(ctx);
 
@@ -439,7 +445,7 @@ async function cmdWait(ctx: Ctx, args: string[]): Promise<void> {
       ctx.stderr(`${PROG}: unexpected status '${status}' — continuing to poll\n`);
     }
 
-    if (elapsed >= Number(timeout)) {
+    if (elapsed >= timeoutSeconds) {
       ctx.stderr(`${PROG}: wait timed out after ${timeout}s (last status: ${status})\n`);
       ctx.stderr(`${PROG}: re-run with /setup-gbrain --resume-provision ${ref}\n`);
       throw new ExitError(6);
diff --git a/test/gbrain-supabase-provision.test.ts b/test/gbrain-supabase-provision.test.ts
index 0cff7f1e0..a0d2a981e 100644
--- a/test/gbrain-supabase-provision.test.ts
+++ b/test/gbrain-supabase-provision.test.ts
@@ -360,6 +360,17 @@ describe('wait', () => {
     expect(r.stderr).toContain('wait timed out');
     expect(r.stderr).toContain('--resume-provision abc');
   });
+
+  test('non-numeric --timeout dies at parse time instead of polling forever', async () => {
+    // NaN would make `elapsed >= timeout` always false: an infinite 5s poll loop.
+    // The bash predecessor errored on `[ "$elapsed" -ge "abc" ]`; the port
+    // must be at least as strict.
+    const r = await runCmd(['wait', 'abc', '--timeout', 'abc'], {
+      SUPABASE_ACCESS_TOKEN: 'sbp_test',
+    });
+    expect(r.status).toBe(2);
+    expect(r.stderr).toContain('--timeout must be a non-negative integer');
+  });
 });
 
 describe('pooler-url', () => {