diff --git a/changelog.d/manifest-baseline-yaml-anchors.md b/changelog.d/manifest-baseline-yaml-anchors.md
new file mode 100644
index 000000000..082982751
--- /dev/null
+++ b/changelog.d/manifest-baseline-yaml-anchors.md
@@ -0,0 +1,7 @@
+## Fixed
+
+- Manifest validation and the devkit's `defineTypePack` accept seed upgrade
+  baselines whose frontmatter uses YAML anchors. They now read only a starter's
+  top-level `kind`, `name` and `version`, without alias expansion, instead of
+  rejecting the whole document; TaskNotes' first task starter uses an anchor,
+  so its `tasknotes.task` manifests failed validation.
diff --git a/packages/devkit/src/index.test.ts b/packages/devkit/src/index.test.ts
index fe1e87d56..2e6a4d5d3 100644
--- a/packages/devkit/src/index.test.ts
+++ b/packages/devkit/src/index.test.ts
@@ -382,6 +382,11 @@ describe("canonical developer validation", () => {
     });
     expect(pack.resources).toEqual([{ source: "_types/task.md", document: starter(3) }]);
 
+    // A starter that reuses values through YAML anchors still declares its version.
+    const anchored = starter(1, "schema:\n  value:\n    properties:\n      status: { enum: &a1 [open, done] }\n      next: { enum: *a1 }\n");
+    expect(defineTypePack(seed([{ document: anchored }])).manifest.resources[0].upgrade_from)
+      .toEqual([{ digest: digest(anchored), document: anchored, version: 1 }]);
+
     const path = "/manifest/resources/0/upgrade_from";
     const rejected = (definition: ReturnType<typeof seed>) => {
       try {
diff --git a/packages/devkit/src/index.ts b/packages/devkit/src/index.ts
index 258e22014..ff7a64a2a 100644
--- a/packages/devkit/src/index.ts
+++ b/packages/devkit/src/index.ts
@@ -1,6 +1,6 @@
 import { createHash } from "node:crypto";
 import { Ajv2020, type ErrorObject, type ValidateFunction } from "ajv/dist/2020.js";
-import { parseDocument } from "yaml";
+import { isMap, parseDocument } from "yaml";
 import {
   connectError,
   MdbaseCollectionClient,
@@ -186,8 +186,9 @@ function upgradeBaseline({ document, version }: { document: string; version?: nu
 function declaredTypeVersion(document: string): number | undefined {
   const frontmatter = /^---\r?\n([\s\S]*?)\r?\n---(?:\r?\n|$)/u.exec(document)?.[1];
   const parsed = frontmatter === undefined ? undefined : parseDocument(frontmatter, { uniqueKeys: true });
-  if (!parsed || parsed.errors.length > 0) return undefined;
-  const version = (parsed.toJS({ maxAliasCount: 0 }) as { version?: unknown } | null)?.version;
+  if (!parsed || parsed.errors.length > 0 || !isMap(parsed.contents)) return undefined;
+  // Read only `version`, so anchors elsewhere in a starter need no alias expansion.
+  const version = parsed.get("version");
   return Number.isInteger(version) && Number(version) > 0 ? Number(version) : undefined;
 }
 
diff --git a/packages/protocol/src/manifest.ts b/packages/protocol/src/manifest.ts
index 2ef75a939..1bd3c3c80 100644
--- a/packages/protocol/src/manifest.ts
+++ b/packages/protocol/src/manifest.ts
@@ -1,7 +1,7 @@
 import { createHash } from "node:crypto";
 import { Ajv2020, type ErrorObject, type ValidateFunction } from "ajv/dist/2020.js";
 import addFormatsModule from "ajv-formats";
-import { parseDocument } from "yaml";
+import { isMap, parseDocument } from "yaml";
 import appManifestSchema from "../schemas/mdbase-app.schema.json" with { type: "json" };
 import legacyAppManifestSchema from "../schemas/mdbase-app.legacy-v1.schema.json" with { type: "json" };
 import type { LegacyMdbaseAppManifest } from "./index.js";
@@ -509,15 +509,15 @@ function validateSeedUpgrade(
 }
 
 /** Top-level frontmatter of a type document, or undefined when it has none. */
+// The identity a type document declares. Only these top-level keys are read, so
+// anchors and aliases elsewhere in a starter are harmless and alias expansion
+// stays disabled.
 function typeFrontmatter(document: string): Record<string, unknown> | undefined {
   const source = /^---\r?\n([\s\S]*?)\r?\n---(?:\r?\n|$)/u.exec(document)?.[1];
   if (source === undefined) return undefined;
   const parsed = parseDocument(source, { uniqueKeys: true });
-  if (parsed.errors.length > 0) return undefined;
-  const value = parsed.toJS({ maxAliasCount: 0 }) as unknown;
-  return value !== null && typeof value === "object" && !Array.isArray(value)
-    ? value as Record<string, unknown>
-    : undefined;
+  if (parsed.errors.length > 0 || !isMap(parsed.contents)) return undefined;
+  return { kind: parsed.get("kind"), name: parsed.get("name"), version: parsed.get("version") };
 }
 
 function sha256(document: string): string {
diff --git a/packages/protocol/test/manifest.test.mjs b/packages/protocol/test/manifest.test.mjs
index 7c636957f..0906ac1dc 100644
--- a/packages/protocol/test/manifest.test.mjs
+++ b/packages/protocol/test/manifest.test.mjs
@@ -125,6 +125,14 @@ test("seed upgrades accept a non-empty list of distinct earlier starters", () =>
   assert.ok(issuesOf(upgradeManifest([])).some((entry) => entry.startsWith("minItems ")));
 });
 
+test("seed upgrade baselines may use YAML anchors without alias expansion", () => {
+  // TaskNotes' first task starter reuses an enum through an anchor.
+  const anchored = starter(1, "schema:\n  value:\n    properties:\n      status: { enum: &a1 [open, done] }\n      next: { enum: *a1 }\n");
+  const value = upgradeManifest([anchored, starter(2)]);
+  assert.deepEqual(validateAppManifest(value), { valid: true, issues: [] });
+  assert.deepEqual(issuesOf(upgradeManifest([{ ...anchored, version: 2 }])), [`seedUpgrade ${upgradePath}/0/version`]);
+});
+
 test("seed upgrade baselines are rejected with the offending baseline's path", () => {
   const first = starter(1);
   const second = starter(2);