diff --git a/assets/AGENTS.md b/assets/AGENTS.md
index 50666ad9..9a0a3b5d 100644
--- a/assets/AGENTS.md
+++ b/assets/AGENTS.md
@@ -88,7 +88,7 @@ An epic's or milestone's `Required` also holds back every quest under it.
 A child that must precede a sibling is in that sibling's `Required`.
 Nothing else orders work within a milestone: `quest unblocked` ranks it by downstream impact, then path.
 When the section is empty, delete it; the quest is now unblocked.
-`Required` must be acyclic.
+`Required` must be acyclic, and never link to a later milestone than the document listing it: move one side with `quest mv` or remove the link.
 
 `quest check` enforces this structure.
 Run it after creating or updating quests.
diff --git a/assets/skills/audit.md b/assets/skills/audit.md
index 0d10cdb5..877e9180 100644
--- a/assets/skills/audit.md
+++ b/assets/skills/audit.md
@@ -10,7 +10,7 @@ The scope is every outstanding quest, or the quests and epics the argument names
 Look for:
 - Disagreements: quests whose goals or plans contradict each other, the code, or the repository's docs.
 - Conflicts: quests that would change the same code or interface incompatibly, or that must land in order without a `Required` link.
-- Misaligned priorities: a quest placed in a milestone ahead of work it depends on, or behind work it blocks.
+- Misaligned priorities: a quest whose milestone no longer matches its urgency, or that depends on later-milestone work without a `Required` link saying so (`quest check` already rejects a `Required` link to a later milestone).
 - Stale plans: work already done, blockers that have cleared, or references to code that no longer exists.
 - Obsolete quests: a problem that is no longer real, or a plan a later change or decision has made the wrong solution.
 
diff --git a/quest/m0/milestone-order.md b/quest/m0/milestone-order.md
deleted file mode 100644
index bf0abb63..00000000
--- a/quest/m0/milestone-order.md
+++ /dev/null
@@ -1,62 +0,0 @@
-# [S] Reject Required links to a later milestone
-
-## Goal
-
-`quest check` fails on a `Required` entry whose target sits in a later
-milestone than the document listing it, such as an m1 quest requiring an m2
-one. The finding names both documents and their milestones, and says to move
-the later quest or epic earlier with `quest mv`, or remove the link. A
-milestone README cannot move, since milestones are permanent, so when either
-side is one the finding offers only moving the quest or epic on the other
-side, or removing the link. Quests, epic READMEs, and milestone READMEs are
-all covered; the root README, which belongs to no milestone, and links to
-other repositories are not.
-
-`quest unblocked` ranks a blocker by its own milestone, so an inverted link
-leaves the earlier quest stalled behind all of the later milestone's work. On
-2026-11-13, moq-dev/moq's main held six such links, moq.pro's one, and rind's
-one.
-
-## Plan
-
-Decided 2026-11-13 (user, /quest-plan):
-
-- How is an inverted link prevented?
-  - ✅ `quest check` rejects it (recommended): the tree then states each
-    quest's real priority, and `/quest-audit` no longer has to spot it by eye
-    (rejected: ranking a blocker at its dependents' earliest milestone instead,
-    which hides the misplaced quest; both, which is redundant once check holds)
-- Milestone?
-  - ✅ m0 (recommended): it fixes stalls in moq-dev's own repositories (rejected:
-    m1, m2)
-- What about the links already on main in moq, moq.pro, and rind?
-  - ✅ Fix them now, in one PR per repository, before this rule ships
-    (rejected: list them here and leave them to each repository's pin bump):
-    [moq-dev/moq#8637](https://github.com/moq-dev/moq/pull/8637), the
-    pre-cut audit, which supersedes the closed moq-dev/moq#8645, and
-    [moq-dev/moq.pro#3992](https://github.com/moq-dev/moq.pro/pull/3992).
-- Challenged the same day: moq splits m1 and m2 by kind, not priority, and
-  its 2026-11-12 audit kept additive m1 quests requiring breaking m2 work on
-  purpose. Should ranking instead give a blocker its dependents' earliest
-  milestone?
-  - ✅ Keep the check rule (user: "I definitely don't want earlier milestones
-    blocked on later milestones") (rejected: ranking inheritance instead;
-    both). moq moves those quests to m3.
-    rind's one link goes when
-    [kixel-ai/rind#606](https://github.com/kixel-ai/rind/pull/606) merges
-    and deletes the quest it points to. Before this rule ships, re-scan
-    each repository's main for links added since.
-
-Implementation guidance:
-
-- A document's milestone is the root child directory that holds it, ordered
-  as `quest unblocked` orders milestones, so `m10` follows `m9`.
-- There is no `--fix`: which side moves is a priority decision for the
-  maintainer, as `/quest-audit` already treats moving a quest between
-  milestones.
-- Every check finding also makes `quest unblocked` and `quest start` fail, so
-  a repository whose tree holds an inverted link cannot rank work until it
-  fixes it. That is intended; the fixes above clear moq-dev's trees first.
-- Update the guide's `Required` rules in `assets/AGENTS.md` beside
-  "`Required` must be acyclic", and narrow `/quest-audit`'s "misaligned
-  priorities" item in `assets/skills/audit.md` to what check cannot see.
diff --git a/src/core/rules.ts b/src/core/rules.ts
index f66b2230..90034e1e 100644
--- a/src/core/rules.ts
+++ b/src/core/rules.ts
@@ -95,6 +95,7 @@ export function check(docs: Doc[], exists: (path: string) => boolean): Finding[]
 	collisions(found, known, docs);
 	membership(found, known, docs);
 	milestones(found, docs);
+	inversions(found, docs);
 	cycles(found, docs);
 
 	return found.sort(compareFindings);
@@ -339,6 +340,49 @@ export function finishedMilestone(docs: Doc[]): (doc: Doc, entry: Entry) => bool
 	};
 }
 
+/**
+ * The milestone README of the root child directory holding `path`, or `null`
+ * for the root README and files directly under the root.
+ */
+function milestoneOf(path: string): string | null {
+	const parts = path.split("/");
+	return parts.length >= 3 ? `${parts[0]}/${parts[1]}/README.md` : null;
+}
+
+/**
+ * A `Required` link must not point to a later milestone. `quest unblocked`
+ * ranks a blocker by its own milestone, so an inverted link stalls the earlier
+ * quest behind all of the later milestone's work. Which side moves is the
+ * maintainer's priority call, so there is no fix. A milestone README cannot
+ * move, since milestones are permanent.
+ */
+function inversions(found: Finding[], docs: Doc[]) {
+	for (const doc of docs) {
+		const from = milestoneOf(doc.path);
+		if (from === null) continue;
+		for (const entry of entries(doc, "Required")) {
+			if (entry.target === null) continue;
+			const target = rooted(entry.target);
+			if (target === null) continue;
+			const to = milestoneOf(target);
+			if (to === null || comparePaths(to, from) <= 0) continue;
+			const [early, late] = [from.split("/")[1], to.split("/")[1]];
+			const name = (path: string) => path.replace(/\/README\.md$/, "");
+			const moves = [
+				permanent(target) ? null : `move ${name(target)} to ${early}`,
+				permanent(doc.path) ? null : `move ${name(doc.path)} to ${late}`,
+			].filter((move) => move !== null);
+			const fix =
+				moves.length > 0 ? `${moves.join(" or ")} with \`quest mv\`, or remove the link` : "remove the link";
+			found.push({
+				path: doc.path,
+				line: entry.line,
+				message: `in milestone ${early}, requires ${target} in later milestone ${late}; ${fix}`,
+			});
+		}
+	}
+}
+
 /**
  * `Required` must be acyclic. A cycle is a set of quests none of which can ever
  * start, and walking the links to rule one out is exactly the manual step an
diff --git a/test/tree.test.ts b/test/tree.test.ts
index 290babf2..62f9e4a7 100644
--- a/test/tree.test.ts
+++ b/test/tree.test.ts
@@ -405,12 +405,18 @@ describe("finished milestones", () => {
 		expect(t.ready()).toEqual([]);
 	});
 
-	// moq-dev/moq's m1 lists m0 quests: those blockers keep it open.
+	// A milestone README may list earlier quests: those blockers keep it open.
 	test("a milestone with only blockers left is open", () => {
-		gated()
-			.append("quest/m0/README.md", "\n## Required\n\n- [Other](/quest/m1/other.md)\n")
-			.remove("quest/m0/epic")
-			.write("quest/m1/other.md", "# [S] Other\n\n## Goal\n\nOpen work m0 waits on.\n")
+		tree()
+			.write(
+				"quest/m1/README.md",
+				"# M1\n\n## Goal\n\nThe next milestone.\n\n## Required\n\n- [One](/quest/m0/epic/one.md)\n",
+			)
+			.write("quest/m2/README.md", "# M2\n\n## Goal\n\nLater.\n")
+			.write(
+				"quest/m2/gate.md",
+				"# [S] Gate\n\n## Goal\n\nRuns once m1 finishes.\n\n## Required\n\n- [M1](/quest/m1/README.md)\n",
+			)
 			.accepts();
 	});
 
@@ -815,3 +821,66 @@ describe("scheduled", () => {
 		expect(t.ready()).toEqual(["quest/m0/epic/one.md"]);
 	});
 });
+
+// `quest unblocked` ranks a blocker by its own milestone, so a link to a later
+// one stalls the earlier quest behind all of that milestone's work.
+describe("Required links to a later milestone", () => {
+	const later = () =>
+		tree()
+			.write("quest/m1/README.md", "# M1\n\n## Goal\n\nLater.\n")
+			.write("quest/m1/late.md", "# [S] Late\n\n## Goal\n\nLater work.\n");
+	const REQ = "\n## Required\n\n- [Late](/quest/m1/late.md)\n";
+
+	test("a quest requiring a later quest", () => {
+		expect(later().append("quest/m0/epic/two.md", REQ).findings()).toEqual([
+			"quest/m0/epic/two.md:13: in milestone m0, requires quest/m1/late.md in later milestone m1; move quest/m1/late.md to m0 or move quest/m0/epic/two.md to m1 with `quest mv`, or remove the link",
+		]);
+	});
+
+	test("an epic README requiring a later quest", () => {
+		const findings = later().append("quest/m0/epic/README.md", REQ).findings();
+		expect(findings).toHaveLength(1);
+		expect(findings[0]).toContain("move quest/m1/late.md to m0 or move quest/m0/epic to m1");
+	});
+
+	test("a milestone README offers only moving the other side", () => {
+		const findings = later().append("quest/m0/README.md", REQ).findings();
+		expect(findings).toHaveLength(1);
+		expect(findings[0]).toContain(
+			"in later milestone m1; move quest/m1/late.md to m0 with `quest mv`, or remove the link",
+		);
+	});
+
+	test("a later milestone README offers only moving the requirer", () => {
+		const findings = later()
+			.append("quest/m0/epic/two.md", "\n## Required\n\n- [M1](/quest/m1/README.md)\n")
+			.findings();
+		expect(findings[0]).toContain("move quest/m0/epic/two.md to m1 with `quest mv`, or remove the link");
+	});
+
+	test("m10 follows m9", () => {
+		const t = tree()
+			.write("quest/m9/README.md", "# M9\n\n## Goal\n\nNine.\n")
+			.write("quest/m9/nine.md", "# [S] Nine\n\n## Goal\n\nNine.\n")
+			.write("quest/m10/README.md", "# M10\n\n## Goal\n\nTen.\n")
+			.write("quest/m10/a.md", "# [S] A\n\n## Goal\n\nA.\n\n## Required\n\n- [M9](/quest/m9/README.md)\n");
+		t.accepts();
+		t.write("quest/m10/a.md", "# [S] A\n\n## Goal\n\nA.\n").write(
+			"quest/m9/b.md",
+			"# [S] B\n\n## Goal\n\nB.\n\n## Required\n\n- [A](/quest/m10/a.md)\n",
+		);
+		expect(t.findings()).toEqual([
+			"quest/m9/b.md:9: in milestone m9, requires quest/m10/a.md in later milestone m10; move quest/m10/a.md to m9 or move quest/m9/b.md to m10 with `quest mv`, or remove the link",
+		]);
+	});
+
+	test("earlier and same-milestone links pass", () => {
+		later()
+			.write("quest/m1/other.md", "# [S] Other\n\n## Goal\n\nSame milestone.\n")
+			.append(
+				"quest/m1/late.md",
+				"\n## Required\n\n- [One](/quest/m0/epic/one.md)\n- [Other](/quest/m1/other.md)\n",
+			)
+			.accepts();
+	});
+});