Ignore inline YAML comments in skill frontmatter

cli/src/sandbox-layer.ts

@@ -12,6 +12,27 @@ export interface SkillFrontmatter {
   requiredCapabilities?: string[];
 }
 
+function stripSkillInlineComment(value: string): string {
+  for (let i = 0; i < value.length; i++) {
+    const ch = value[i];
+    const prev = value[i - 1];
+    const afterSpace = i === 0 || prev === " " || prev === "\t";
+    if ((ch === '"' || ch === "'") && (afterSpace || prev === "[" || prev === ",")) {
+      let close = i + 1;
+      while (close < value.length) {
+        if (ch === '"' && value[close] === "\\") close += 2;
+        else if (value[close] !== ch) close++;
+        else if (ch === "'" && value[close + 1] === "'") close += 2;
+        else break;
+      }
+      if (close < value.length) i = close;
+    } else if (ch === "#" && afterSpace) {
+      return value.slice(0, i).trimEnd();
+    }
+  }
+  return value;
+}
+
 function stripSkillQuotes(value: string): string {
   const trimmed = value.trim();
   if (
@@ -47,7 +68,7 @@ export function parseSkillFrontmatter(md: string, sourcePath: string): SkillFron
     const kv = /^([A-Za-z0-9_-]+):\s*(.*)$/.exec(line);
     if (!kv) continue;
     const key = kv[1]!;
-    const rest = kv[2] ?? "";
+    const rest = stripSkillInlineComment(kv[2] ?? "");
     if (rest === ">" || rest === "|" || rest === ">-" || rest === "|-") {
       const literal = rest[0] === "|";
       const baseIndent = skillIndent(line);
@@ -75,10 +96,10 @@ export function parseSkillFrontmatter(md: string, sourcePath: string): SkillFron
       if (!next.trim() || skillIndent(next) <= baseIndent) break;
       const item = /^\s*-\s+(.*)$/.exec(next);
       if (!item) break;
-      items.push(stripSkillQuotes(item[1]!));
+      items.push(stripSkillQuotes(stripSkillInlineComment(item[1]!)));
       i++;
     }
-    fields[key] = items;
+    fields[key] = items.filter(Boolean);
   }
 
   const name = fields["name"];

cli/test/tool-descriptor.test.ts

@@ -257,6 +257,21 @@ test("parseSkillFrontmatter requires name + description + body; requiredCapabili
     "SKILL.md",
   );
   assert.deepEqual(caps.requiredCapabilities, ["a", "b"]);
+  const commented = parseSkillFrontmatter(
+    '---\nname: demo # note\ndescription: "a # inside quotes" # note\ntag: c#sharp\nrequiredCapabilities: [a, b] # why\n---\nbody',
+    "SKILL.md",
+  );
+  assert.equal(commented.name, "demo");
+  assert.equal(commented.description, "a # inside quotes");
+  assert.deepEqual(commented.requiredCapabilities, ["a", "b"]);
+  assert.throws(
+    () => parseSkillFrontmatter("---\nname: # note\ndescription: y\n---\nbody", "SKILL.md"),
+    /missing "name"/,
+  );
+  const long = `a${" ".repeat(200_000)}${'\\"'.repeat(100_000)}b`;
+  const started = performance.now();
+  assert.equal(parseSkillFrontmatter(`---\nname: x\ndescription: "${long}"\n---\nbody`, "SKILL.md").description, long);
+  assert.ok(performance.now() - started < 2_000, "parseSkillFrontmatter must not backtrack on long scalars");
   assert.throws(() => parseSkillFrontmatter("no frontmatter", "SKILL.md"), /missing YAML frontmatter/);
   assert.throws(() => parseSkillFrontmatter("---\ndescription: y\n---\nbody", "SKILL.md"), /missing "name"/);
   assert.throws(() => parseSkillFrontmatter("---\nname: x\n---\nbody", "SKILL.md"), /missing "description"/);
@@ -278,6 +293,17 @@ test("drift-lock: cli skill parser matches the core seed parser's output", () =>
     "---\nname: a\ndescription: b\n---\nbody\n",
     "\uFEFF---\r\nname: a\r\ndescription: b\r\n---\r\nbody\r\n",
     "---\nname: a\ndescription: b\nrequiredCapabilities: [one, 'two']\n---\nbody\n",
+    "---\nname: a # inline note\ndescription: b # inline note\n---\nbody\n",
+    "---\nname: a\ndescription: b\nrequiredCapabilities: [one, two] # why\n---\nbody\n",
+    "---\nname: a\ndescription: > # note\n  folded\n---\nbody\n",
+    "---\nname: a\ndescription: b\nrequiredCapabilities:\n  - one # why\n---\nbody\n",
+    "---\nname: # note\ndescription: b\n---\nbody\n",
+    "---\nname: a\ndescription: 'b # c'\n---\nbody\n",
+    "---\nname: a\ndescription: b#c\n---\nbody\n",
+    '---\nname: a\ndescription: "He said \\"go\\" # really"\n---\nbody\n',
+    "---\nname: a\ndescription: 'it''s # fine'\n---\nbody\n",
+    "---\nname: a\ndescription: use 'em all # note\n---\nbody\n",
+    "---\nname: a\ndescription: b\nrequiredCapabilities:\n  - one # why\n  - # dropped\n  - two\n---\nbody\n",
     "---\nname: a\ndescription: b\nrequiredCapabilities:\n  - one\n  - two\n---\nbody\n",
     "---\nname: a\ndescription: >\n  folded description\n---\nbody\n",
     "---\nname: a\ndescription: b\nrequiredCapabilities: one, two\n---\nbody\n",

src/skills/frontmatter.ts

@@ -5,6 +5,27 @@ export interface Frontmatter {
   body: string;
 }
 
+function stripInlineComment(value: string): string {
+  for (let i = 0; i < value.length; i++) {
+    const ch = value[i];
+    const prev = value[i - 1];
+    const afterSpace = i === 0 || prev === " " || prev === "\t";
+    if ((ch === '"' || ch === "'") && (afterSpace || prev === "[" || prev === ",")) {
+      let close = i + 1;
+      while (close < value.length) {
+        if (ch === '"' && value[close] === "\\") close += 2;
+        else if (value[close] !== ch) close++;
+        else if (ch === "'" && value[close + 1] === "'") close += 2;
+        else break;
+      }
+      if (close < value.length) i = close;
+    } else if (ch === "#" && afterSpace) {
+      return value.slice(0, i).trimEnd();
+    }
+  }
+  return value;
+}
+
 function stripQuotes(value: string): string {
   const t = value.trim();
   if (t.length >= 2 && ((t[0] === '"' && t.at(-1) === '"') || (t[0] === "'" && t.at(-1) === "'"))) {
@@ -44,7 +65,7 @@ export function parseFrontmatter(raw: string): Frontmatter {
     const m = /^([A-Za-z0-9_-]+):\s*(.*)$/.exec(line);
     if (!m) continue;
     const key = m[1]!;
-    const rest = m[2] ?? "";
+    const rest = stripInlineComment(m[2] ?? "");
 
     if (rest === ">" || rest === "|" || rest === ">-" || rest === "|-") {
       const literal = rest[0] === "|";
@@ -74,10 +95,10 @@ export function parseFrontmatter(raw: string): Frontmatter {
       if (indentOf(next) <= baseIndent) break;
       const item = /^\s*-\s+(.*)$/.exec(next);
       if (!item) break;
-      items.push(stripQuotes(item[1]!));
+      items.push(stripQuotes(stripInlineComment(item[1]!)));
       i++;
     }
-    attrs[key] = items;
+    attrs[key] = items.filter((s) => s.length > 0);
   }
 
   return { attrs, body: source.slice(end + closing[0].length).replace(/^\s+/, "") };

test/frontmatter.test.ts

@@ -97,3 +97,57 @@ test("seed skill names cannot escape or alias their materialized directory", ()
   }
   assert.equal(parseSeedSkillFrontmatter(skill("foo-bar_v1.2")).name, "foo-bar_v1.2");
 });
+
+test("drops unquoted inline comments but keeps # inside quotes or words", () => {
+  const { attrs } = parseFrontmatter(`---
+name: demo # human-readable note
+description: "a # inside quotes" # trailing note
+tag: c#sharp
+joined: foo# bar
+caps: [one, two] # why
+folded: > # note
+  folded body
+empty: # nothing left
+list:
+  - command:demo # why
+---
+body`);
+  assert.equal(attrs.name, "demo");
+  assert.equal(attrs.description, "a # inside quotes");
+  assert.equal(attrs.tag, "c#sharp");
+  assert.equal(attrs.joined, "foo# bar");
+  assert.deepEqual(attrs.caps, ["one", "two"]);
+  assert.equal(attrs.folded, "folded body");
+  assert.deepEqual(attrs.empty, []);
+  assert.deepEqual(attrs.list, ["command:demo"]);
+});
+
+test("a commented-out value is missing, not a literal comment", () => {
+  assert.throws(() => parseSeedSkillFrontmatter("---\nname: # note\ndescription: d\n---\nbody"), /requires name/);
+  assert.equal(parseSeedSkillFrontmatter("---\nname: demo # note\ndescription: d # note\n---\nbody").name, "demo");
+});
+
+test("a # inside quotes (with escapes, doubling, or an unclosed quote) is not a comment", () => {
+  const { attrs } = parseFrontmatter(`---
+escaped: "He said \\"go\\" # really"
+doubled: 'it''s # fine'
+unclosed: use 'em all # note
+caps:
+  - one # why
+  - # dropped
+  - two
+---
+body`);
+  assert.equal(attrs.escaped, 'He said \\"go\\" # really');
+  assert.equal(attrs.doubled, "it''s # fine");
+  assert.equal(attrs.unclosed, "use 'em all");
+  assert.deepEqual(attrs.caps, ["one", "two"]);
+});
+
+test("inline comment stripping stays linear on long scalars", () => {
+  const value = `a${" ".repeat(200_000)}${'\\"'.repeat(100_000)}b`;
+  const started = performance.now();
+  const { attrs } = parseFrontmatter(`---\nname: demo\ndescription: "${value}"\n---\nbody`);
+  assert.ok(performance.now() - started < 2_000, "parseFrontmatter must not backtrack on long scalars");
+  assert.equal(attrs.description, value);
+});