fix(parser): lenient answer salvage — no raw JSON leaks when the brain breaks JSON with unescaped quotes (e.g. German „..." quotes); 3 new tests

apps/desktop/src/agent.js

@@ -75,6 +75,38 @@ export function parseToolCall(text) {
   return null;
 }
 
+/**
+ * Lenient salvage: LLMs often emit a JSON answer with an unescaped quote
+ * inside the string (e.g. German quotes), breaking strict parsing. Extract
+ * the string value of `key` by scanning with escape awareness. Returns the
+ * decoded string, or null when the field cannot be found.
+ */
+export function lenientStringField(text, key) {
+  const re = new RegExp('"' + key + '"\\s*:\\s*"');
+  const m = re.exec(String(text || ''));
+  if (!m) return null;
+  let i = m.index + m[0].length;
+  let out = '';
+  while (i < text.length) {
+    const c = text[i];
+    if (c === '\\') {
+      const n = text[i + 1];
+      if (n === 'n') out += '\n';
+      else if (n === 't') out += '\t';
+      else if (n === 'r') out += '\r';
+      else if (n === '\\') out += '\\';
+      else if (n === '"') out += '"';
+      else out += (n ?? '');
+      i += 2;
+      continue;
+    }
+    if (c === '"') return out;
+    out += c;
+    i++;
+  }
+  return out !== '' ? out : null;
+}
+
 /**
  * Reasoning-protocol parser: the brain answers in one of three shapes:
  *   {reasoning, tool, args}      → {kind:'tools',  calls:[...]}
@@ -82,6 +114,7 @@ export function parseToolCall(text) {
  *   plain text                   → {kind:'text',   text}
  *   valid JSON, wrong shape      → null (malformed → corrective nudge)
  *   prose wrapping any of those  → detected via balanced-brace extraction
+ *   broken JSON with an answer   → salvaged leniently (no raw JSON leaks)
  */
 export function parseBrainReply(text) {
   if (!text) return null;
@@ -144,6 +177,15 @@ export function parseBrainReply(text) {
       ai += 6;
     }
   }
+  // Lenient salvage: broken JSON (unescaped quotes etc.) but a readable
+  // answer field — deliver the answer instead of leaking raw JSON.
+  if (text.trim().startsWith('{')) {
+    const answer = lenientStringField(text, 'answer');
+    if (answer !== null && answer.trim() !== '') {
+      const reasoning = lenientStringField(text, 'reasoning');
+      return { kind: 'answer', answer, reasoning: reasoning ?? '' };
+    }
+  }
   return { kind: 'text', text };
 }
 

apps/desktop/test/agent.test.mjs

@@ -132,9 +132,9 @@ describe('tools/registry', () => {
 // ── Brain reply parser (reasoning protocol) ──────────────────────
 
 describe('brain reply parser', () => {
-  let parseBrainReply, parseToolCall;
+  let parseBrainReply, parseToolCall, lenientStringField;
   before(async () => {
-    ({ parseBrainReply, parseToolCall } = await import('../src/agent.js'));
+    ({ parseBrainReply, parseToolCall, lenientStringField } = await import('../src/agent.js'));
   });
 
   it('parses a plain tool call (legacy)', () => {
@@ -187,6 +187,24 @@ describe('brain reply parser', () => {
     assert.equal(parseBrainReply(''), null);
     assert.equal(parseBrainReply(null), null);
   });
+
+  it('salvages a broken answer JSON with unescaped quotes (no raw JSON leak)', () => {
+    const raw = '{"reasoning":"Der Befehl wurde ausgeführt","answer":"Er sagte: „Ich bin ein KI-Assistent."\n\nHinweis: sag Bescheid."}';
+    const r = parseBrainReply(raw);
+    assert.equal(r.kind, 'answer');
+    assert.ok(r.answer.startsWith('Er sagte:'));
+    assert.ok(!r.answer.includes('{') && !r.answer.includes('reasoning'));
+  });
+
+  it('does not salvage plain text that merely starts with a brace', () => {
+    const r = parseBrainReply('{"weird": "broken string without answer');
+    assert.equal(r.kind, 'text');
+  });
+
+  it('lenientStringField handles escapes', () => {
+    const out = lenientStringField('{"answer":"line1\\nline2 \\\\ back \\\"q\\\""}', 'answer');
+    assert.equal(out, 'line1\nline2 \\ back "q"');
+  });
 });
 
 // ── Config tests ──────────────────────────────────────────────────