diff --git a/src/__tests__/ui-inline-scripts-parse.test.ts b/src/__tests__/ui-inline-scripts-parse.test.ts
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+++ b/src/__tests__/ui-inline-scripts-parse.test.ts
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+/**
+ * Regression guard for issue #111 — "APP doesn't initialize / unresponsive".
+ *
+ * The SPA is a single classic <script> in docs/index.html. A duplicate `response`
+ * declaration in `_safeLLMCallOnce` made the whole script fail to PARSE
+ * (`SyntaxError: Identifier 'response' has already been declared`), so nothing ran:
+ * the UI stuck on "Initializing…", every handler unwired, only a pre-registered
+ * poller still firing. A parse error in one inline script breaks that entire script
+ * tag, so we compile every classic inline <script> the way a browser would (a
+ * `vm.Script` is parsed as a classic script — no module/CORS/DOM needed) and require
+ * each to compile. This catches the whole class of "the app won't boot because the
+ * script won't parse" regressions with no browser and no new dependency.
+ */
+import { describe, it, expect } from 'vitest';
+import { readFileSync } from 'node:fs';
+import vm from 'node:vm';
+
+const html = readFileSync(new URL('../../docs/index.html', import.meta.url), 'utf8');
+
+/**
+ * Extract the bodies of bare inline `<script>` blocks (the app's own scripts). We
+ * deliberately match only `<script>` with no attributes: external libs are
+ * `<script src=…>` and never inline code, and the app never uses `type="module"`.
+ * In-string occurrences (`'<script'`, the escaped `<\/script>` inside a regex
+ * literal) can't false-match: they aren't a bare `<script>` open, and the real
+ * close tag is `</script>` while the in-string one is written `<\/script>`.
+ */
+function inlineScripts(source: string): string[] {
+  const blocks: string[] = [];
+  const re = /<script>([\s\S]*?)<\/script>/g;
+  let m: RegExpExecArray | null;
+  while ((m = re.exec(source)) !== null) blocks.push(m[1]);
+  return blocks;
+}
+
+describe('docs/index.html inline scripts (issue #111 regression)', () => {
+  const blocks = inlineScripts(html);
+
+  it('extracts the app inline scripts (guard against a vacuous pass)', () => {
+    expect(blocks.length).toBeGreaterThanOrEqual(5);
+  });
+
+  it('every classic inline <script> compiles without a SyntaxError', () => {
+    const failures: string[] = [];
+    blocks.forEach((src, i) => {
+      try {
+        // eslint-disable-next-line no-new
+        new vm.Script(src, { filename: `docs/index.html#inline-${i}` });
+      } catch (e) {
+        failures.push(`inline #${i}: ${(e as Error).message}`);
+      }
+    });
+    expect(failures, failures.join('\n')).toEqual([]);
+  });
+});