@@ -6,6 +6,9 @@
  * without touching the real catalog. validate.mjs wires them into the run.
  */
 
+import path from "node:path";
+import { parseStack, pickPath, StackError } from "./lib/stacks.mjs";
+
 const DATE_RE = /^\d{4}-\d{2}-\d{2}$/;
 const DATE_ANY_RE = /\d{4}-\d{2}-\d{2}/g;
 
@@ -309,6 +312,44 @@ export function checkActiveIsSettled(rel, meta) {
   return errors;
 }
 
+/* ----------------------------------------------------------------- V15 */
+/**
+ * Starter stacks (stacks/<id>.md). The shape rules live in lib/stacks.mjs so
+ * the build and this check cannot drift; here each pick must also be a
+ * catalog entry that is still listed, and the stack id must be unique.
+ */
+export function checkStacks(stackFiles, entriesByPath, terms, today) {
+  const errors = [];
+  const ids = new Map();
+  for (const { rel, text } of stackFiles) {
+    let stack;
+    try {
+      stack = parseStack(text, { file: rel, terms });
+    } catch (err) {
+      if (err instanceof StackError) {
+        errors.push(err.message);
+        continue;
+      }
+      throw err;
+    }
+    const { id, walked } = stack.meta;
+    if (id !== path.posix.basename(rel, ".md")) errors.push(`${rel}: id "${id}" does not match the filename`);
+    if (ids.has(id)) errors.push(`duplicate stack id "${id}": ${ids.get(id)} and ${rel}`);
+    else ids.set(id, rel);
+    if (today && walked > today) errors.push(`${rel}: walked ${walked} is in the future`);
+    for (const section of stack.sections) {
+      for (const pick of section.picks) {
+        const entry = entriesByPath.get(pickPath(rel, pick.href));
+        if (!entry) errors.push(`${rel}:${pick.line}: pick "${pick.href}" is not a catalog entry`);
+        else if (String(entry.status) === "deprecated") {
+          errors.push(`${rel}:${pick.line}: pick "${entry.id}" is deprecated; repick or move the need to Gaps`);
+        }
+      }
+    }
+  }
+  return errors;
+}
+
 /* ----------------------------------------------------------------- V11 */
 /**
  * A category README row must not contradict its entry's frontmatter. The
 
@@ -19,6 +19,7 @@ import {
   checkLicenseVocabulary,
   checkPublisherConsistency,
   checkSpdxConsistency,
+  checkStacks,
   checkTaxonomyValues,
   checkValueSpellings,
 } from "./checks.mjs";
@@ -538,10 +539,29 @@ accepts(
   checkActiveIsSettled("ok.md", { status: "active", license: "MIT", commercial: true, attribution_required: false })
 );
 
+/* V15 ------------------------------------------------------------------- */
+const stackEntries = new Map([
+  ["catalog/2d/good.md", { id: "good", status: "active" }],
+  ["catalog/2d/old.md", { id: "old", status: "deprecated" }],
+]);
+const stackText = (pick, meta = {}) =>
+  `---\nid: ${meta.id || "s1"}\ntitle: T\ntask: A task.\nwalked: ${meta.walked || "2026-09-01"}\n---\n\nLead.\n\n${meta.section || "## Art"}\n\n${pick}\n`;
+const goodPick = "- **Tiles:** [Good](../catalog/2d/good.md). Sixteen tiles.";
+const oneStack = (text, rel = "stacks/s1.md") => checkStacks([{ rel, text }], stackEntries, ["MIT"], TODAY);
+accepts("V15 accepts a good stack", oneStack(stackText(goodPick)));
+rejects("V15 rejects a pick that is not an entry", oneStack(stackText("- **Tiles:** [Nope](../catalog/2d/nope.md). Why.")), 'stacks/s1.md:12: pick "../catalog/2d/nope.md" is not a catalog entry');
+rejects("V15 rejects a deprecated pick", oneStack(stackText("- **Tiles:** [Old](../catalog/2d/old.md). Why.")), 'stacks/s1.md:12: pick "old" is deprecated');
+rejects("V15 rejects a malformed pick line", oneStack(stackText("- Tiles: Good. Why.")), "stacks/s1.md:12: a pick line is");
+rejects("V15 rejects an id that is not the filename", oneStack(stackText(goodPick), "stacks/other.md"), 'id "s1" does not match the filename');
+rejects("V15 rejects a duplicate id", checkStacks([{ rel: "stacks/s1.md", text: stackText(goodPick) }, { rel: "stacks/s1.md", text: stackText(goodPick) }], stackEntries, [], TODAY), 'duplicate stack id "s1"');
+rejects("V15 rejects a licence in a why sentence", oneStack(stackText("- **Tiles:** [Good](../catalog/2d/good.md). A MIT pack.")), 'names a licence ("MIT")');
+rejects("V15 rejects a walked date in the future", oneStack(stackText(goodPick, { walked: "2099-01-01" })), "walked 2099-01-01 is in the future");
+rejects("V15 rejects an unknown section", oneStack(stackText(goodPick, { section: "## Levels" })), 'section "Levels" is not one of');
+
 /* ----------------------------------------------------------------------- */
 if (failures.length) {
   console.error(`checks.test failed (${failures.length}):`);
   for (const f of failures) console.error(`  - ${f}`);
   process.exit(1);
 }
-console.log(`checks.test ok: ${passed} assertions across 14 checks`);
+console.log(`checks.test ok: ${passed} assertions across 15 checks`);
@@ -15,16 +15,19 @@ import {
   checkLicenseVocabulary,
   checkPublisherConsistency,
   checkSpdxConsistency,
+  checkStacks,
   checkTaxonomyValues,
   checkValueSpellings,
 } from "./checks.mjs";
+import { licenceTerms } from "./lib/stacks.mjs";
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 const ROOT = path.resolve(__dirname, "..");
 const CATALOG = path.join(ROOT, "catalog");
 const CONFIG_PATH = path.join(__dirname, "config.json");
 const SPDX_ALLOWED_PATH = path.join(__dirname, "spdx-allowed.json");
 const VOCAB_PATH = path.join(__dirname, "license-vocabulary.json");
+const STACKS = path.join(ROOT, "stacks");
 const REQUIRED = [
   "id",
   "name",
@@ -341,6 +344,14 @@ function main() {
   errors.push(...checkPublisherConsistency(records));
   errors.push(...checkValueSpellings(records));
 
+  // V15: starter stacks. README.md in stacks/ is the directory's guide, not a stack.
+  const stackFiles = walkFiles(STACKS, [], (f) => f.endsWith(".md") && path.basename(f) !== "README.md").map(
+    (f) => ({ rel: relFromRoot(f), text: fs.readFileSync(f, "utf8") })
+  );
+  for (const { rel, text } of stackFiles) if (hasEmoji(text)) errors.push(`${rel} contains emoji`);
+  const entriesByPath = new Map(records.map(({ rel, meta }) => [rel, { id: String(meta.id), status: String(meta.status) }]));
+  errors.push(...checkStacks(stackFiles, entriesByPath, licenceTerms(vocab, [...spdxAllowed]), today));
+
   const byCategory = new Map();
   for (const record of records) {
     const cat = String(record.meta.category);
@@ -388,6 +399,7 @@ function main() {
 
   const mdRoots = [
     CATALOG,
+    STACKS,
     path.join(ROOT, "docs"),
     path.join(ROOT, "README.md"),
     path.join(ROOT, "CONTRIBUTING.md"),
@@ -417,7 +429,7 @@ function main() {
   }
 
   console.log(
-    `validate ok: ${entryFiles.length} entries, ${ids.size} ids, no broken links`
+    `validate ok: ${entryFiles.length} entries, ${ids.size} ids, ${stackFiles.length} stacks, no broken links`
   );
   console.log(coverageReport(entries));
 }