diff --git a/src/core/raw/CLAUDE.md b/src/core/raw/CLAUDE.md
index cc37d06..3be4f2e 100644
--- a/src/core/raw/CLAUDE.md
+++ b/src/core/raw/CLAUDE.md
@@ -88,7 +88,11 @@ mutation is in-memory until `cli/raw/commit.ts` saves after the last gate.
   `validationXmlFor` applies **MCE preprocessing to a CLONE** first — strip
   `mc:Ignorable`-declared attrs/elements, resolve `mc:AlternateContent` →
   `mc:Fallback` — because real Word markup (`w14:paraId` on every `w:p`) is
-  valid OOXML that the base schema doesn't know. Gate 6 is a **baseline diff**
+  valid OOXML that the base schema doesn't know. The same clone also unwraps
+  the `<w:ins>`/`<w:del>` Word writes INSIDE a math run (`<m:r><w:del>…`),
+  its documented extension for a tracked equation edit ([MS-OI29500] Part 1
+  §22.1.2.87 (e)) that `CT_R` has no slot for; what the mark wraps is still
+  checked. Gate 6 is a **baseline diff**
   (`diffValidationIssues`, multiset on message text): a third of real documents
   carry pre-existing violations, so a raw edit is judged only on errors it
   ADDS. `docx validate` reuses the engine standalone, per WML part (parts are
diff --git a/src/core/raw/validate.ts b/src/core/raw/validate.ts
index 7323869..8251c8a 100644
--- a/src/core/raw/validate.ts
+++ b/src/core/raw/validate.ts
@@ -91,10 +91,12 @@ export const WML_ROOT_TAGS = new Set([
 	"w:glossaryDocument",
 ]);
 
-/** Serialize a part root for validation: clone, apply MCE preprocessing, emit. */
+/** Serialize a part root for validation: clone, apply MCE preprocessing and
+ *  Word's math-run revision unwrap, emit. */
 export function validationXmlFor(root: XmlNode): string {
 	const cleaned = root.clone();
 	mceStrip(cleaned, new Set());
+	unwrapMathRunRevisions(cleaned);
 	return XmlNode.serialize([cleaned]);
 }
 
@@ -185,6 +187,21 @@ function mceStrip(node: XmlNode, ignorableAbove: Set<string>): void {
 	node.children = kept;
 }
 
+/** Word records a tracked equation edit INSIDE each math run —
+ *  `<m:r><w:del …><m:t>x</m:t></w:del></m:r>` — and documents that it does,
+ *  though ECMA-376's `CT_R` has no slot for it ([MS-OI29500] Part 1
+ *  §22.1.2.87 (e)). Every file Word saved with such an edit failed validation,
+ *  including docx-cli's own `<w:del><m:oMath>` edits once Word re-saved them.
+ *  Unwrapping the mark in the clone keeps what it wraps checked against
+ *  `CT_R`. */
+function unwrapMathRunRevisions(node: XmlNode): void {
+	for (const child of node.children) unwrapMathRunRevisions(child);
+	if (node.tag !== "m:r") return;
+	node.children = node.children.flatMap((child) =>
+		child.tag === "w:ins" || child.tag === "w:del" ? child.children : [child],
+	);
+}
+
 /** Compile the schema once per process and keep it (libxml2 objects need
  *  explicit disposal, but a process-lifetime validator is the point here).
  *  Cross-file `xsd:import`s resolve through a virtual input provider over the
diff --git a/tests/core/raw.test.ts b/tests/core/raw.test.ts
index 7624a33..46c69ad 100644
--- a/tests/core/raw.test.ts
+++ b/tests/core/raw.test.ts
@@ -346,6 +346,38 @@ describe("gate 6 — XSD engine", () => {
 		);
 		expect(fresh).toEqual([]);
 	});
+
+	// Word marks a tracked equation edit inside each math run (MS-OI29500,
+	// Part 1 §22.1.2.87 (e)); the transitional XSD has no slot for it, so every
+	// such file Word saved used to fail `validate`. Shape copied from Word 365.
+	function mathDocument(run: string): XmlNode {
+		const root = XmlNode.findRoot(
+			XmlNode.parse(
+				`<w:document xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><w:body><w:p><m:oMath>${run}</m:oMath></w:p></w:body></w:document>`,
+			),
+			"w:document",
+		);
+		if (!root) throw new Error("no document root");
+		return root;
+	}
+
+	test("Word's revision marks inside a math run validate clean", () => {
+		for (const tag of ["w:del", "w:ins"]) {
+			const root = mathDocument(
+				`<m:r><${tag} w:id="0" w:author="Word User" w:date="2026-10-28T11:55:00Z"><m:rPr><m:sty m:val="p"/></m:rPr><w:rPr><w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/></w:rPr><m:t>=</m:t></${tag}></m:r>`,
+			);
+			expect(validateWmlXml(validationXmlFor(root))).toEqual([]);
+		}
+	});
+
+	test("what a math-run revision mark wraps is still checked", () => {
+		const root = mathDocument(
+			`<m:r><w:del w:id="0" w:author="Word User"><w:bogusElement/></w:del></m:r>`,
+		);
+		const issues = validateWmlXml(validationXmlFor(root));
+		expect(issues).toHaveLength(1);
+		expect(issues[0]?.message).toContain("bogusElement");
+	});
 });
 
 describe("diffValidationIssues", () => {