fix(skills): preserve escaped quotes in frontmatter lists (#6265)

* fix(skills): preserve escaped quotes in frontmatter lists

* test(skills): use descriptive frontmatter examples

---------

Co-authored-by: Bolt4243 <277300782+Bolt4243@users.noreply.github.com>

services/memory/skill_format.py

@@ -130,10 +130,15 @@ def _parse_scalar(raw: str, *, string_only: bool = False) -> Any:
 def _split_top_level(s: str, sep: str) -> List[str]:
     """Split `s` on `sep` ignoring separators inside [] or quotes."""
     out, buf, depth, quote = [], [], 0, None
+    escaped = False
     for ch in s:
         if quote:
             buf.append(ch)
-            if ch == quote:
+            if escaped:
+                escaped = False
+            elif ch == "\\" and quote == '"':
+                escaped = True
+            elif ch == quote:
                 quote = None
             continue
         if ch in ("'", '"'):

tests/test_skill_frontmatter_list_escapes.py

@@ -0,0 +1,54 @@
+"""Inline frontmatter lists must preserve quoted values across save/load cycles."""
+
+import importlib.util
+from pathlib import Path
+import sys
+import unittest
+
+
+# Load the dependency-free formatter without starting the services package.
+_PATH = Path(__file__).resolve().parents[1] / "services" / "memory" / "skill_format.py"
+_SPEC = importlib.util.spec_from_file_location("_skill_list_format_under_test", _PATH)
+_FORMAT = importlib.util.module_from_spec(_SPEC)
+sys.modules[_SPEC.name] = _FORMAT
+_SPEC.loader.exec_module(_FORMAT)
+
+
+class FrontmatterListEscapesTests(unittest.TestCase):
+    def test_skill_tags_survive_repeated_save_load_cycles(self):
+        tags = ['review "release, notes', 'use "search", then summarize', 'publish']
+        skill = _FORMAT.Skill(name="release-review", tags=tags)
+        for _ in range(5):
+            skill = _FORMAT.Skill.from_markdown(skill.to_markdown())
+            self.assertEqual(skill.tags, tags)
+
+    def test_escaped_quotes_preserve_each_list_field(self):
+        for field in ("tags", "platforms", "requires_toolsets", "fallback_for_toolsets"):
+            with self.subTest(field=field):
+                values = ['review "release, notes', 'publish']
+                skill = _FORMAT.Skill(name="release-review", **{field: values})
+                restored = _FORMAT.Skill.from_markdown(skill.to_markdown())
+                self.assertEqual(getattr(restored, field), values)
+
+    def test_backslash_parity_does_not_hide_quotes_or_list_separators(self):
+        for count in range(1, 5):
+            with self.subTest(backslashes=count):
+                values = ['review ' + '\\' * count + '"release, notes', 'path, ' + '\\' * count, 'publish']
+                text = _FORMAT.emit_frontmatter({"tags": values})
+                parsed, _ = _FORMAT.parse_frontmatter(f"---\n{text}\n---\n")
+                self.assertEqual(parsed["tags"], values)
+
+    def test_single_quoted_backslashes_remain_literal(self):
+        text = "---\ntags: ['C:\\', next]\n---\n"
+        parsed, _ = _FORMAT.parse_frontmatter(text)
+        self.assertEqual(parsed["tags"], ["C:\\", "next"])
+
+    def test_nested_lists_preserve_quoted_brackets_and_commas(self):
+        values = [['review "], notes', 'publish'], 'archive']
+        text = _FORMAT.emit_frontmatter({"tags": values})
+        parsed, _ = _FORMAT.parse_frontmatter(f"---\n{text}\n---\n")
+        self.assertEqual(parsed["tags"], values)
+
+
+if __name__ == "__main__":
+    unittest.main()