fix(roadmap): handle numbered, bracketed, and indented prose H3 headers in slice parser (#3063)

The prose slice header fallback parser failed to extract slices when
LLMs generated common formatting variants: numbered prefixes (### 1. S01),
parenthetical numbering (### (1) S01), bracketed IDs (### [S01]), or
indented headings (  ### S01). This caused auto-mode to permanently block
with "No slice eligible" when the plan-milestone prompt produced these
formats inside a ## Slices section.

Broadened the parseProseSliceHeaders regex to accept optional leading
whitespace, numeric prefixes, parenthetical numbering, and square brackets
around slice IDs.

Closes #2567

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/resources/extensions/gsd/roadmap-slices.ts

@@ -219,13 +219,14 @@ export function parseRoadmapSlices(content: string): RoadmapSliceEntry[] {
 function parseProseSliceHeaders(content: string): RoadmapSliceEntry[] {
   const slices: RoadmapSliceEntry[] = [];
   // Match H1-H4 headers containing S<digits> with optional "Slice" prefix, bold markers,
-  // and optional checkmark completion marker before the slice ID.
+  // numeric prefixes (e.g., "1.", "(1)"), bracketed IDs (e.g., "[S01]"),
+  // optional checkmark completion marker, and optional leading indentation.
   // Separator after the ID is flexible: colon, dash, em/en dash, dot, or just whitespace.
-  const headerPattern = /^#{1,4}\s+\*{0,2}(?:\u2713\s+)?(?:Slice\s+)?(S\d+)\*{0,2}[:\s.\u2014\u2013-]*\s*(.+)/gm;
+  const headerPattern = /^\s*#{1,4}\s+\*{0,2}(?:\u2713\s+)?(?:\d+[.)]\s+)?(?:\(\d+\)\s+)?(?:Slice\s+)?\[?(S\d+)\]?\*{0,2}[:\s.\u2014\u2013-]*\s*(.+)/gm;
   let match: RegExpExecArray | null;
 
   // Check for checkmark before the slice ID (e.g., "## checkmark S01: Title")
-  const prefixCheckPattern = /^#{1,4}\s+\*{0,2}\u2713\s+/;
+  const prefixCheckPattern = /^\s*#{1,4}\s+\*{0,2}\u2713\s+/;
 
   while ((match = headerPattern.exec(content)) !== null) {
     const id = match[1]!;
@@ -251,7 +252,7 @@ function parseProseSliceHeaders(content: string): RoadmapSliceEntry[] {
 
     // Try to extract depends from prose: "Depends on: S01" or "**Depends on:** S01, S02"
     const afterHeader = content.slice(match.index + match[0].length);
-    const nextHeader = afterHeader.search(/^#{1,4}\s/m);
+    const nextHeader = afterHeader.search(/^\s*#{1,4}\s/m);
     const section = nextHeader !== -1 ? afterHeader.slice(0, nextHeader) : afterHeader.slice(0, 500);
 
     const depsMatch = section.match(/\*{0,2}Depends\s+on:?\*{0,2}\s*(.+)/i);

src/resources/extensions/gsd/tests/roadmap-slices.test.ts

@@ -296,3 +296,100 @@ Do the second thing.
   assert.equal(slices[0]?.id, "S01");
   assert.equal(slices[1]?.id, "S02");
 });
+
+// ── Regression tests for #2567 ─────────────────────────────────────────────
+// Prose H3 parser fails on common LLM-generated patterns: numbered prefixes,
+// parenthetical numbering, bracketed IDs, and indented headings.
+
+test("parseRoadmapSlices: numbered H3 headers under ## Slices (#2567)", () => {
+  const numberedContent = `# M002: My Milestone
+
+**Vision:** Ship the product.
+
+## Slices
+
+### 1. S01: Setup Environment
+Set up the dev environment and tooling.
+
+### 2. S02: Build Core
+Implement the core logic.
+**Depends on:** S01
+
+### 3. S03: Polish UI
+Final polish and theming.
+**Depends on:** S01, S02
+`;
+  const slices = parseRoadmapSlices(numberedContent);
+  assert.equal(slices.length, 3, "should parse 3 slices from numbered H3 headers");
+  assert.equal(slices[0]?.id, "S01");
+  assert.equal(slices[0]?.title, "Setup Environment");
+  assert.equal(slices[1]?.id, "S02");
+  assert.deepEqual(slices[1]?.depends, ["S01"]);
+  assert.equal(slices[2]?.id, "S03");
+  assert.deepEqual(slices[2]?.depends, ["S01", "S02"]);
+});
+
+test("parseRoadmapSlices: parenthetical-numbered H3 headers (#2567)", () => {
+  const parenContent = `# M002: Milestone
+
+**Vision:** Ship.
+
+## Slices
+
+### (1) S01: Setup
+Setup work.
+
+### (2) S02: Build
+Build work.
+**Depends on:** S01
+`;
+  const slices = parseRoadmapSlices(parenContent);
+  assert.equal(slices.length, 2, "should parse slices with parenthetical numbering");
+  assert.equal(slices[0]?.id, "S01");
+  assert.equal(slices[0]?.title, "Setup");
+  assert.equal(slices[1]?.id, "S02");
+  assert.deepEqual(slices[1]?.depends, ["S01"]);
+});
+
+test("parseRoadmapSlices: bracketed slice IDs in H3 headers (#2567)", () => {
+  const bracketContent = `# M002: Milestone
+
+**Vision:** Ship.
+
+## Slices
+
+### [S01] Setup Environment
+Setup work.
+
+### [S02] Build Core
+Build work.
+**Depends on:** S01
+`;
+  const slices = parseRoadmapSlices(bracketContent);
+  assert.equal(slices.length, 2, "should parse slices with bracketed IDs");
+  assert.equal(slices[0]?.id, "S01");
+  assert.equal(slices[0]?.title, "Setup Environment");
+  assert.equal(slices[1]?.id, "S02");
+  assert.deepEqual(slices[1]?.depends, ["S01"]);
+});
+
+test("parseRoadmapSlices: indented H3 headers under ## Slices (#2567)", () => {
+  const indentedContent = `# M002: Milestone
+
+**Vision:** Ship.
+
+## Slices
+
+  ### S01: Setup
+  Setup work.
+
+  ### S02: Build
+  Build work.
+`;
+  const slices = parseRoadmapSlices(indentedContent);
+  assert.equal(slices.length, 2, "should parse slices from indented H3 headers");
+  assert.equal(slices[0]?.id, "S01");
+  assert.equal(slices[0]?.title, "Setup");
+  assert.equal(slices[1]?.id, "S02");
+  assert.equal(slices[1]?.title, "Build");
+});