diff --git a/coverage/emitted-schema-known-failures.json b/coverage/emitted-schema-known-failures.json
index 7abd554..fe51488 100644
--- a/coverage/emitted-schema-known-failures.json
+++ b/coverage/emitted-schema-known-failures.json
@@ -1,8 +1 @@
-[
-  {
-    "id": "synthetic-table-missing-tblgrid",
-    "issue": "#453",
-    "match": "}tr': This element is not expected.",
-    "reason": "synthetic table fixtures omit the required w:tblGrid, and the engine faithfully preserves the gap into emitted output"
-  }
-]
+[]
diff --git a/packages/docx-core/src/integration/canonical-emission-regression.test.ts b/packages/docx-core/src/integration/canonical-emission-regression.test.ts
index 5920af9..3ffffde 100644
--- a/packages/docx-core/src/integration/canonical-emission-regression.test.ts
+++ b/packages/docx-core/src/integration/canonical-emission-regression.test.ts
@@ -215,7 +215,7 @@ describe('Canonical emission catalog', () => {
     await given('a table row with a prior height definition', async () => {
       const { doc } = await loadIndexedDoc(
         await makeMinimalDocx(
-          '<w:tbl><w:tr><w:trPr><w:trHeight w:val="360" w:hRule="atLeast"/></w:trPr><w:tc><w:p><w:r><w:t>Cell</w:t></w:r></w:p></w:tc></w:tr></w:tbl>',
+          '<w:tbl><w:tblPr/><w:tblGrid><w:gridCol/></w:tblGrid><w:tr><w:trPr><w:trHeight w:val="360" w:hRule="atLeast"/></w:trPr><w:tc><w:p><w:r><w:t>Cell</w:t></w:r></w:p></w:tc></w:tr></w:tbl>',
         ),
       );
 
@@ -240,7 +240,7 @@ describe('Canonical emission catalog', () => {
     await given('a table cell with prior padding properties', async () => {
       const { doc } = await loadIndexedDoc(
         await makeMinimalDocx(
-          '<w:tbl><w:tr><w:tc><w:tcPr><w:tcMar><w:top w:w="100" w:type="dxa"/></w:tcMar></w:tcPr><w:p><w:r><w:t>Cell</w:t></w:r></w:p></w:tc></w:tr></w:tbl>',
+          '<w:tbl><w:tblPr/><w:tblGrid><w:gridCol/></w:tblGrid><w:tr><w:tc><w:tcPr><w:tcMar><w:top w:w="100" w:type="dxa"/></w:tcMar></w:tcPr><w:p><w:r><w:t>Cell</w:t></w:r></w:p></w:tc></w:tr></w:tbl>',
         ),
       );
 
diff --git a/packages/docx-core/src/primitives/layout.test.ts b/packages/docx-core/src/primitives/layout.test.ts
index 3ce1146..cea8034 100644
--- a/packages/docx-core/src/primitives/layout.test.ts
+++ b/packages/docx-core/src/primitives/layout.test.ts
@@ -143,56 +143,61 @@ describe('layout tracked-change emission', () => {
     });
   });
 
-  test('setTableCellPadding emits tcPrChange with the prior cell properties snapshot', async ({ given, when, then }: AllureBddContext) => {
-    let doc: Document;
-    let tcMar: Element;
-    let left: Element;
-    let tcPrChange: Element;
-    let previousTcMar: Element;
-
-    await given('a table cell that already has top padding', () => {
-      doc = makeDocument(
-        `<w:tbl><w:tr><w:tc><w:tcPr><w:tcMar><w:top w:w="100" w:type="dxa"/></w:tcMar></w:tcPr><w:p><w:r><w:t>Cell</w:t></w:r></w:p></w:tc></w:tr></w:tbl>`,
-      );
-    });
-
-    await when('tracked left padding is added', () => {
-      const result = setTableCellPadding(
-        doc,
-        { tableIndexes: [0], leftDxa: 240 },
-        createRevisionContext({
-          author: 'SafeDocX AI',
-          date: '2026-05-03T14:15:16Z',
-          idState: createRevisionIdState(),
-        }),
-      );
-      expect(result).toEqual({
-        affectedCells: 1,
-        missingTableIndexes: [],
-        missingRowIndexes: [],
-        missingCellIndexes: [],
-      });
-
-      const table = doc.getElementsByTagNameNS(W_NS, W.tbl).item(0) as Element;
-      const row = firstDirectChild(table, W.tr);
-      const cell = firstDirectChild(row, W.tc);
-      const tcPr = firstDirectChild(cell, W.tcPr);
-      tcMar = firstDirectChild(tcPr, W.tcMar);
-      left = firstDirectChild(tcMar, W.left);
-      tcPrChange = firstDirectChild(tcPr, 'tcPrChange');
-      previousTcMar = firstDirectChild(firstDirectChild(tcPrChange, W.tcPr), W.tcMar);
-    });
-
-    await then('the outer cell properties are updated while the inner tcPr snapshot preserves the old padding', () => {
-      expect(wordAttr(tcPrChange, 'author')).toBe('SafeDocX AI');
-      expect(wordAttr(tcPrChange, 'date')).toBe('2026-05-03T14:15:16Z');
-      expect(revisionId(tcPrChange)).toBe(1);
-      expect(wordAttr(left, 'w')).toBe('240');
-      expect(wordAttr(left, 'type')).toBe('dxa');
-      expect(getDirectChildrenByName(previousTcMar, W.left)).toHaveLength(0);
-      expect(firstDirectChild(previousTcMar, W.top)).toBeDefined();
-    });
-  });
+  test
+    .conformance({ spec: 'ECMA-376', edition: 5, part: 1, section: '17.4.68' })(
+      'setTableCellPadding emits tcPrChange with the prior cell properties snapshot',
+      async ({ given, when, then }: AllureBddContext) => {
+        let doc: Document;
+        let tcMar: Element;
+        let left: Element;
+        let tcPrChange: Element;
+        let previousTcMar: Element;
+
+        await given('a table cell that already has top padding', () => {
+          doc = makeDocument(
+            `<w:tbl><w:tr><w:tc><w:tcPr><w:tcMar><w:top w:w="100" w:type="dxa"/></w:tcMar></w:tcPr><w:p><w:r><w:t>Cell</w:t></w:r></w:p></w:tc></w:tr></w:tbl>`,
+          );
+        });
+
+        await when('tracked left padding is added', () => {
+          const result = setTableCellPadding(
+            doc,
+            { tableIndexes: [0], leftDxa: 240 },
+            createRevisionContext({
+              author: 'SafeDocX AI',
+              date: '2026-05-03T14:15:16Z',
+              idState: createRevisionIdState(),
+            }),
+          );
+          expect(result).toEqual({
+            affectedCells: 1,
+            missingTableIndexes: [],
+            missingRowIndexes: [],
+            missingCellIndexes: [],
+          });
+
+          const table = doc.getElementsByTagNameNS(W_NS, W.tbl).item(0) as Element;
+          const row = firstDirectChild(table, W.tr);
+          const cell = firstDirectChild(row, W.tc);
+          const tcPr = firstDirectChild(cell, W.tcPr);
+          tcMar = firstDirectChild(tcPr, W.tcMar);
+          left = firstDirectChild(tcMar, W.left);
+          tcPrChange = firstDirectChild(tcPr, 'tcPrChange');
+          previousTcMar = firstDirectChild(firstDirectChild(tcPrChange, W.tcPr), W.tcMar);
+        });
+
+        await then('the outer cell properties are updated while the inner tcPr snapshot preserves the old padding', () => {
+          expect(wordAttr(tcPrChange, 'author')).toBe('SafeDocX AI');
+          expect(wordAttr(tcPrChange, 'date')).toBe('2026-05-03T14:15:16Z');
+          expect(revisionId(tcPrChange)).toBe(1);
+          expect(Array.from(tcMar.children).map((child) => child.localName)).toEqual([W.top, W.left]);
+          expect(wordAttr(left, 'w')).toBe('240');
+          expect(wordAttr(left, 'type')).toBe('dxa');
+          expect(getDirectChildrenByName(previousTcMar, W.left)).toHaveLength(0);
+          expect(firstDirectChild(previousTcMar, W.top)).toBeDefined();
+        });
+      },
+    );
 
   test('layout primitives preserve legacy mutation behavior when revision context is omitted', async ({ given, when, then }: AllureBddContext) => {
     let doc: Document;
diff --git a/packages/docx-core/src/primitives/layout.ts b/packages/docx-core/src/primitives/layout.ts
index 63bb952..e5d7e8d 100644
--- a/packages/docx-core/src/primitives/layout.ts
+++ b/packages/docx-core/src/primitives/layout.ts
@@ -92,6 +92,19 @@ function ensureChild(parent: Element, localName: string): Element {
   return created;
 }
 
+/**
+ * Keep per-cell margins in the CT_TcMar child sequence required by the schema.
+ *
+ * @conformance ECMA-376 edition 5, Part 1 § 17.4.68
+ */
+function reorderCellMarginEdges(tcMar: Element): void {
+  const orderedNames = [W.top, W.left, W.bottom, W.right];
+  const ordered = orderedNames.flatMap((name) => getDirectChildrenByName(tcMar, name));
+  for (const child of ordered) {
+    tcMar.appendChild(child);
+  }
+}
+
 function setWAttr(el: Element, localName: string, value: string): void {
   el.setAttributeNS(OOXML.W_NS, `w:${localName}`, value);
 }
@@ -274,6 +287,7 @@ export function setTableCellPadding(
           setWAttr(right, W.w, String(mutation.rightDxa));
           setWAttr(right, W.type, 'dxa');
         }
+        reorderCellMarginEdges(tcMar);
         if (ctx) {
           // CT_TcPr permits at most one <w:tcPrChange> child.
           for (const stale of getDirectChildrenByName(tcPr, 'tcPrChange')) {
diff --git a/packages/docx-core/src/primitives/minimal_save.test.ts b/packages/docx-core/src/primitives/minimal_save.test.ts
index c3af726..a0d6c12 100644
--- a/packages/docx-core/src/primitives/minimal_save.test.ts
+++ b/packages/docx-core/src/primitives/minimal_save.test.ts
@@ -193,7 +193,7 @@ describe('minimal re-serialization on save (issue #408)', () => {
       `<w:p><w:proofErr w:type="spellStart"/><w:r w:rsidR="00CC0001"><w:t>cell</w:t></w:r>` +
       `<w:proofErr w:type="spellEnd"/><w:r w:rsidR="00CC0002"><w:t xml:space="preserve"> text</w:t></w:r></w:p>`;
     const TBL = (cellP: string) =>
-      `<w:tbl><w:tr><w:tc>${cellP}</w:tc></w:tr></w:tbl>`;
+      `<w:tbl><w:tblPr/><w:tblGrid><w:gridCol/></w:tblGrid><w:tr><w:tc>${cellP}</w:tc></w:tr></w:tbl>`;
     let untouched: { originalXml: string; savedXml: string };
     let modified: { originalXml: string; savedXml: string };
 
@@ -240,10 +240,10 @@ describe('minimal re-serialization on save (issue #408)', () => {
     // proofErr/rsid-bearing paragraph in the table must keep its original
     // XML — issue #408's repro document is almost entirely tables.
     const cellP = (id: string, marker: string) =>
-      `<w:p w14:paraId="${id}"><w:proofErr w:type="spellStart"/><w:r w:rsidR="00${marker}01"><w:t>${marker}</w:t></w:r>` +
-      `<w:proofErr w:type="spellEnd"/><w:r w:rsidR="00${marker}02"><w:t xml:space="preserve"> tail</w:t></w:r></w:p>`;
+      `<w:p w14:paraId="${id}"><w:proofErr w:type="spellStart"/><w:r w:rsidR="0000${marker}01"><w:t>${marker}</w:t></w:r>` +
+      `<w:proofErr w:type="spellEnd"/><w:r w:rsidR="0000${marker}02"><w:t xml:space="preserve"> tail</w:t></w:r></w:p>`;
     const tableBody =
-      `<w:tbl><w:tblPr><w:tblW w:w="0" w:type="auto"/></w:tblPr>` +
+      `<w:tbl><w:tblPr><w:tblW w:w="0" w:type="auto"/></w:tblPr><w:tblGrid><w:gridCol/><w:gridCol/></w:tblGrid>` +
       `<w:tr><w:tc>${cellP('00000A01', 'AA')}${cellP('00000A02', 'AB')}</w:tc><w:tc>${cellP('00000B01', 'BA')}</w:tc></w:tr>` +
       `<w:tr><w:tc>${cellP('00000C01', 'CA')}</w:tc><w:tc>${cellP('00000D01', 'DA')}</w:tc></w:tr>` +
       `</w:tbl>`;
diff --git a/packages/docx-mcp/src/integration/canonical-emission-mcp.test.ts b/packages/docx-mcp/src/integration/canonical-emission-mcp.test.ts
index b6517af..b8da33c 100644
--- a/packages/docx-mcp/src/integration/canonical-emission-mcp.test.ts
+++ b/packages/docx-mcp/src/integration/canonical-emission-mcp.test.ts
@@ -268,6 +268,8 @@ describe('Tool integration through SessionManager: canonical revision emission',
         xml: makeDocXml(
           '<w:p><w:r><w:t>Spacing paragraph.</w:t></w:r></w:p>' +
             '<w:tbl>' +
+            '<w:tblPr/>' +
+            '<w:tblGrid><w:gridCol/><w:gridCol/></w:tblGrid>' +
             '<w:tr>' +
             '<w:tc><w:p><w:r><w:t>A1</w:t></w:r></w:p></w:tc>' +
             '<w:tc><w:p><w:r><w:t>B1</w:t></w:r></w:p></w:tc>' +
diff --git a/packages/docx-mcp/src/tools/add_accept_tracked_changes.test.ts b/packages/docx-mcp/src/tools/add_accept_tracked_changes.test.ts
index fab92e2..431a2fa 100644
--- a/packages/docx-mcp/src/tools/add_accept_tracked_changes.test.ts
+++ b/packages/docx-mcp/src/tools/add_accept_tracked_changes.test.ts
@@ -161,7 +161,7 @@ describe('Traceability: Accept Tracked Changes', () => {
         `<w:pPr><w:pStyle w:val="Heading1"/><w:pPrChange w:id="10" w:author="A"><w:pPr/></w:pPrChange></w:pPr>` +
         `<w:r><w:rPr><w:b/><w:rPrChange w:id="11" w:author="A"><w:rPr/></w:rPrChange></w:rPr><w:t>bold text</w:t></w:r>` +
         `</w:p>` +
-        `<w:tbl><w:tblPr><w:tblPrChange w:id="12" w:author="A"><w:tblPr/></w:tblPrChange></w:tblPr>` +
+        `<w:tbl><w:tblPr><w:tblPrChange w:id="12" w:author="A"><w:tblPr/></w:tblPrChange></w:tblPr><w:tblGrid><w:gridCol/></w:tblGrid>` +
         `<w:tr><w:tc><w:tcPr><w:tcPrChange w:id="13" w:author="A"><w:tcPr/></w:tcPrChange></w:tcPr>` +
         `<w:p><w:r><w:t>cell</w:t></w:r></w:p></w:tc></w:tr></w:tbl>`;
       const filePath = await writeTestDocx(dir, 'prchange.docx', bodyXml);
diff --git a/packages/docx-mcp/src/tools/add_safe_docx_layout_format_controls.test.ts b/packages/docx-mcp/src/tools/add_safe_docx_layout_format_controls.test.ts
index c69989c..16d2e91 100644
--- a/packages/docx-mcp/src/tools/add_safe_docx_layout_format_controls.test.ts
+++ b/packages/docx-mcp/src/tools/add_safe_docx_layout_format_controls.test.ts
@@ -77,6 +77,8 @@ describe('Traceability: Layout Format Controls', () => {
       `<w:body>` +
       `<w:p><w:r><w:t>Table heading</w:t></w:r></w:p>` +
       `<w:tbl>` +
+      `<w:tblPr/>` +
+      `<w:tblGrid><w:gridCol/><w:gridCol/></w:tblGrid>` +
       `<w:tr>` +
       `<w:tc><w:p><w:r><w:t>A1</w:t></w:r></w:p></w:tc>` +
       `<w:tc><w:p><w:r><w:t>B1</w:t></w:r></w:p></w:tc>` +
diff --git a/packages/docx-mcp/src/tools/extract_revisions.test.ts b/packages/docx-mcp/src/tools/extract_revisions.test.ts
index 7150e12..a4be2b4 100644
--- a/packages/docx-mcp/src/tools/extract_revisions.test.ts
+++ b/packages/docx-mcp/src/tools/extract_revisions.test.ts
@@ -799,7 +799,7 @@ describe('extract_revisions tool', () => {
         `<?xml version="1.0" encoding="UTF-8" standalone="yes"?>` +
         `<w:document xmlns:w="${W_NS}">` +
         `<w:body>` +
-          `<w:tbl><w:tr><w:tc>` +
+          `<w:tbl><w:tblPr/><w:tblGrid><w:gridCol/></w:tblGrid><w:tr><w:tc>` +
             `<w:p><w:r><w:t>Cell </w:t></w:r>` +
             `<w:ins w:author="X"><w:r><w:t>edited</w:t></w:r></w:ins></w:p>` +
           `</w:tc></w:tr></w:tbl>` +
diff --git a/packages/docx-mcp/src/tools/format_layout.validation.test.ts b/packages/docx-mcp/src/tools/format_layout.validation.test.ts
index a524616..278d780 100644
--- a/packages/docx-mcp/src/tools/format_layout.validation.test.ts
+++ b/packages/docx-mcp/src/tools/format_layout.validation.test.ts
@@ -50,6 +50,8 @@ describe('format_layout validation + strictness', () => {
         `<w:body>` +
         `<w:p><w:r><w:t>Only paragraph</w:t></w:r></w:p>` +
         `<w:tbl>` +
+        `<w:tblPr/>` +
+        `<w:tblGrid><w:gridCol/></w:tblGrid>` +
         `<w:tr><w:tc><w:p><w:r><w:t>A1</w:t></w:r></w:p></w:tc></w:tr>` +
         `</w:tbl>` +
         `</w:body>` +
@@ -109,6 +111,8 @@ describe('format_layout validation + strictness', () => {
         `<w:body>` +
         `<w:p><w:r><w:t>P</w:t></w:r></w:p>` +
         `<w:tbl>` +
+        `<w:tblPr/>` +
+        `<w:tblGrid><w:gridCol/></w:tblGrid>` +
         `<w:tr><w:tc><w:p><w:r><w:t>A1</w:t></w:r></w:p></w:tc></w:tr>` +
         `</w:tbl>` +
         `</w:body>` +
diff --git a/packages/docx-mcp/src/tools/non_body_part_preservation.test.ts b/packages/docx-mcp/src/tools/non_body_part_preservation.test.ts
index e516e76..6edd956 100644
--- a/packages/docx-mcp/src/tools/non_body_part_preservation.test.ts
+++ b/packages/docx-mcp/src/tools/non_body_part_preservation.test.ts
@@ -31,6 +31,8 @@ describe('format_layout: non-body part preservation', () => {
       `<w:body>` +
       `<w:p><w:r><w:t>Cover Terms</w:t></w:r></w:p>` +
       `<w:tbl>` +
+      `<w:tblPr/>` +
+      `<w:tblGrid><w:gridCol/><w:gridCol/></w:tblGrid>` +
       `<w:tr>` +
       `<w:tc><w:p><w:r><w:t>A1</w:t></w:r></w:p></w:tc>` +
       `<w:tc><w:p><w:r><w:t>B1</w:t></w:r></w:p></w:tc>` +
diff --git a/packages/docx-mcp/src/tools/strict_transactionality.test.ts b/packages/docx-mcp/src/tools/strict_transactionality.test.ts
index 304144a..297cc07 100644
--- a/packages/docx-mcp/src/tools/strict_transactionality.test.ts
+++ b/packages/docx-mcp/src/tools/strict_transactionality.test.ts
@@ -40,6 +40,8 @@ describe('format_layout: strict failure transactionality', () => {
         `<w:body>` +
         `<w:p><w:r><w:t>Alpha</w:t></w:r></w:p>` +
         `<w:tbl>` +
+        `<w:tblPr/>` +
+        `<w:tblGrid><w:gridCol/></w:tblGrid>` +
         `<w:tr><w:tc><w:p><w:r><w:t>A1</w:t></w:r></w:p></w:tc></w:tr>` +
         `<w:tr><w:tc><w:p><w:r><w:t>A2</w:t></w:r></w:p></w:tc></w:tr>` +
         `</w:tbl>` +