diff --git a/src/report/client.ts b/src/report/client.ts
index 6d56f4f..e98a89f 100644
--- a/src/report/client.ts
+++ b/src/report/client.ts
@@ -346,6 +346,61 @@ function wireLayout(mounted: MountedDiff[]) {
   })
 }
 
+// The global control is one toggle: it folds every section while any is open and
+// unfolds them once they are all closed. It only touches `open` on existing section
+// folds, so the report data is untouched and a single section still toggles natively.
+function sectionFolds(): HTMLDetailsElement[] {
+  return [...document.querySelectorAll<HTMLDetailsElement>('details.section-fold')]
+}
+
+// The focused child of a fold that just closed is no longer rendered, but browsers can
+// leave focus on it. Only the fold's own summary row stays visible.
+function hiddenByClosedFold(element: Element): boolean {
+  for (let node: Element | null = element; node; node = node.parentElement) {
+    if (!node.matches('details:not([open])')) continue
+    const summary = node.querySelector(':scope > summary')
+    // A closed details hides its content but not its own summary row, so keep
+    // walking: an outer closed details can still hide that summary.
+    if (summary && (summary === element || summary.contains(element))) continue
+    return true
+  }
+  return false
+}
+
+function wireGlobalFolds() {
+  const button = document.querySelector<HTMLButtonElement>('[data-fold-all]')
+  if (!button) return
+  const label = button.querySelector<HTMLElement>('[data-fold-all-label]')
+  const folds = sectionFolds()
+  if (folds.length === 0) return
+
+  const allFolded = () => folds.every((fold) => !fold.open)
+  const sync = () => {
+    const folded = allFolded()
+    if (label) label.textContent = folded ? 'Unfold all' : 'Fold all'
+    button.setAttribute(
+      'aria-label',
+      folded ? 'Unfold all review sections' : 'Fold all review sections',
+    )
+  }
+
+  button.addEventListener('click', () => {
+    // Read focus before closing: a browser blurs a descendant the moment its
+    // ancestor details closes, so afterwards activeElement may already be body.
+    const active = document.activeElement
+    const unfold = allFolded()
+    for (const fold of folds) fold.open = unfold
+    if (active instanceof HTMLElement && hiddenByClosedFold(active)) {
+      const section = active.closest('details.section-fold')
+      const summary = section?.querySelector<HTMLElement>(':scope > summary')
+      ;(summary ?? button).focus({ preventScroll: true })
+    }
+    sync()
+  })
+  for (const fold of folds) fold.addEventListener('toggle', sync)
+  sync()
+}
+
 function prepareForPrint() {
   window.addEventListener('beforeprint', () => {
     for (const details of document.querySelectorAll<HTMLDetailsElement>('details')) {
@@ -372,6 +427,7 @@ export function mountReport(
   void mountedDiffs.initialRender.then(finishInitialRender)
   const { mounted } = mountedDiffs
   wireLayout(mounted)
+  wireGlobalFolds()
   prepareForPrint()
 }
 
diff --git a/src/report/shell.ts b/src/report/shell.ts
index c41fead..a0434ff 100644
--- a/src/report/shell.ts
+++ b/src/report/shell.ts
@@ -50,13 +50,15 @@ function renderReportBody(
     <label><input type="radio" name="layout" value="unified" ${layout === 'unified' ? 'checked' : ''}> Unified</label>
     <button type="submit" hidden aria-hidden="true" tabindex="-1"></button>
   </form>`
+  const foldAll = `<button type="button" class="fold-all" data-fold-all aria-label="Fold all review sections"><span data-fold-all-label>Fold all</span></button>`
+  const readingControls = `<div class="review-controls">${layoutForm}${foldAll}</div>`
   const reviewMap = renderReviewMap(
     document.sections.map((section, index) => ({
       title: section.title,
       fragment: targets[index]!.fragment,
     })),
     { sections: sections.length, files },
-    layoutForm,
+    readingControls,
   )
   const summary =
     document.summary.trim() === ''
@@ -205,7 +207,7 @@ ${steps.join('\n')}
 function renderReviewMap(
   sections: { title: string; fragment: string }[],
   counts: { sections: number; files: number },
-  layoutForm: string,
+  controls: string,
 ): string {
   const links = sections
     .map(
@@ -214,7 +216,7 @@ function renderReviewMap(
     )
     .join('\n')
   return `<nav class="review-map" aria-label="Review map">
-  ${layoutForm}
+  ${controls}
   <p class="review-map-label">Review map</p>
   <ol class="review-map-list">
 ${links}
@@ -308,9 +310,14 @@ body {
 .source-metadata dt { color: #7e8d82; font-weight: 600; text-transform: uppercase; letter-spacing: .08em; }
 .source-metadata dd { margin: 0; min-width: 0; overflow: hidden; color: #4e5d53; text-overflow: ellipsis; white-space: nowrap; }
 .source-metadata code { color: #263a2d; font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 11px; }
+.review-controls {
+  display: grid;
+  gap: 8px;
+  margin: 0 10px 20px;
+}
 .layout-form {
   display: flex;
-  margin: 0 10px 20px;
+  margin: 0;
   border: 1px solid #bdcbbf;
   border-radius: 7px;
   overflow: hidden;
@@ -319,6 +326,18 @@ body {
 .layout-form label { flex: 1; padding: 5px 10px; color: #607066; font-size: 13px; text-align: center; cursor: pointer; }
 .layout-form input { display: none; }
 .layout-form label:has(input:checked) { color: #ffffff; background: var(--accent); font-weight: 600; }
+.fold-all {
+  padding: 6px 10px;
+  border: 1px solid #bdcbbf;
+  border-radius: 7px;
+  color: #53665a;
+  background: #f3f7f3;
+  font-size: 13px;
+  font-weight: 600;
+  cursor: pointer;
+}
+.fold-all:hover { color: var(--accent); border-color: #8eaa95; background: #eef5ef; }
+.fold-all:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
 .review-workspace {
   display: grid;
   grid-template-columns: 238px minmax(0, 1fr);
@@ -529,13 +548,16 @@ main { max-width: none; min-width: 0; margin: 0; padding: 22px 28px 72px; }
     backdrop-filter: blur(12px);
   }
   .review-map-label, .review-map-list, .review-map-counts { display: none; }
-  .layout-form { max-width: 260px; margin: 0 0 0 auto; }
+  .review-controls { display: flex; gap: 6px; justify-content: flex-end; margin: 0; }
+  .layout-form { flex: 1 1 auto; max-width: 220px; margin: 0 0 0 auto; }
+  .fold-all { flex: none; padding: 5px 9px; font-size: 12px; }
   main { padding: 14px 10px 50px; }
 }
 @media (max-width: 520px) {
   .report-cover { padding: 18px 16px 8px; }
   .report-cover h1 { font-size: 21px; }
   .layout-form label { padding: 4px 7px; font-size: 11px; }
+  .fold-all { padding: 4px 7px; font-size: 11px; }
   .section-fold > summary { font-size: 14px; }
 }
 @media print {
diff --git a/test/report-dom.test.ts b/test/report-dom.test.ts
index d987852..896c980 100644
--- a/test/report-dom.test.ts
+++ b/test/report-dom.test.ts
@@ -908,4 +908,180 @@ describe('report browser client', () => {
     },
     120000,
   )
+
+  test(
+    'one control folds and unfolds every section and individual folds still work',
+    async () => {
+      const value = document([
+        section(simplePatch('one', 'one!'), 'First section'),
+        section(simplePatch('two', 'two!'), 'Second section'),
+      ])
+      const dom = loadReport(renderReport(value, clientBundle), {
+        url: 'https://reports.example/r/report-id',
+      })
+      const doc = dom.document as unknown as Document
+      const dataScript = doc.querySelector<HTMLScriptElement>('#diffwalk-report-data')!
+      const dataBefore = dataScript.textContent
+      runReportClient()
+
+      const button = doc.querySelector<HTMLButtonElement>('[data-fold-all]')!
+      const folds = [...doc.querySelectorAll<HTMLDetailsElement>('details.section-fold')]
+      const label = () => button.querySelector('[data-fold-all-label]')?.textContent
+      const aria = () => button.getAttribute('aria-label')
+      expect(folds).toHaveLength(2)
+      expect(folds.every((fold) => fold.open)).toBe(true)
+      expect(label()).toBe('Fold all')
+      expect(aria()).toBe('Fold all review sections')
+
+      button.click()
+      expect(folds.every((fold) => !fold.open)).toBe(true)
+      expect(label()).toBe('Unfold all')
+      expect(aria()).toBe('Unfold all review sections')
+
+      button.click()
+      expect(folds.every((fold) => fold.open)).toBe(true)
+      expect(label()).toBe('Fold all')
+      expect(aria()).toBe('Fold all review sections')
+
+      expect(dataScript.textContent).toBe(dataBefore)
+
+      // Individual sections still fold and unfold natively after the global action,
+      // and their toggle drives the global label.
+      folds[0]!
+        .querySelector('summary')!
+        .dispatchEvent(new dom.window.MouseEvent('click', { bubbles: true, cancelable: true }) as unknown as Event)
+      expect(folds[0]!.open).toBe(false)
+      expect(folds[1]!.open).toBe(true)
+      expect(label()).toBe('Fold all')
+
+      folds[1]!
+        .querySelector('summary')!
+        .dispatchEvent(new dom.window.MouseEvent('click', { bubbles: true, cancelable: true }) as unknown as Event)
+      expect(folds.every((fold) => !fold.open)).toBe(true)
+      expect(label()).toBe('Unfold all')
+
+      button.click()
+      expect(folds.every((fold) => fold.open)).toBe(true)
+      expect(label()).toBe('Fold all')
+    },
+    120000,
+  )
+
+  test(
+    'folding all moves focus from a hidden child to the visible section row',
+    async () => {
+      const value = document([
+        {
+          title: 'First section',
+          steps: [{ text: 'First.', diff: simplePatch('one', 'one!'), changes: ['change-001'] }],
+        },
+        {
+          title: 'Second section',
+          steps: [{ text: 'Second.', diff: simplePatch('two', 'two!'), changes: ['change-002'] }],
+        },
+      ])
+      const dom = loadReport(renderReport(value, clientBundle), {
+        url: 'https://reports.example/r/report-id',
+      })
+      const doc = dom.document as unknown as Document
+      runReportClient()
+
+      const firstSection = doc.querySelector<HTMLElement>('.section')!
+      const focused = firstSection.querySelector<HTMLButtonElement>(
+        '.step [data-copy-fragment]',
+      )!
+      focused.focus()
+      expect(doc.activeElement).toBe(focused)
+
+      // Real browsers blur a focused descendant the moment its ancestor details
+      // closes; happy-dom keeps focus, so simulate that blur to prove the global
+      // action still restores focus on the surviving section row.
+      for (const fold of doc.querySelectorAll<HTMLDetailsElement>('details.section-fold')) {
+        fold.addEventListener('toggle', () => {
+          if (!fold.open && fold.contains(focused)) focused.blur()
+        })
+      }
+
+      doc.querySelector<HTMLButtonElement>('[data-fold-all]')!.click()
+
+      const folds = [...doc.querySelectorAll<HTMLDetailsElement>('details.section-fold')]
+      expect(folds.every((fold) => !fold.open)).toBe(true)
+      expect(firstSection.querySelector('details')?.open).toBe(false)
+      const summary = firstSection.querySelector<HTMLElement>('.section-fold > summary')!
+      expect(doc.activeElement).toBe(summary)
+    },
+    120000,
+  )
+
+  test(
+    'folding all moves focus off a closed nested file row onto the section row',
+    async () => {
+      const value = document([
+        section(simplePatch('one', 'one!'), 'First section'),
+        section(simplePatch('two', 'two!'), 'Second section'),
+      ])
+      const dom = loadReport(renderReport(value, clientBundle), {
+        url: 'https://reports.example/r/report-id',
+      })
+      const doc = dom.document as unknown as Document
+      runReportClient()
+
+      const firstSection = doc.querySelector<HTMLElement>('.section')!
+      const file = firstSection.querySelector<HTMLDetailsElement>('details.file')!
+      file.open = false
+      const fileSummary = file.querySelector<HTMLElement>(':scope > summary')!
+      fileSummary.focus()
+      expect(doc.activeElement).toBe(fileSummary)
+
+      for (const fold of doc.querySelectorAll<HTMLDetailsElement>('details.section-fold')) {
+        fold.addEventListener('toggle', () => {
+          if (!fold.open && fold.contains(fileSummary)) fileSummary.blur()
+        })
+      }
+
+      doc.querySelector<HTMLButtonElement>('[data-fold-all]')!.click()
+
+      const sectionSummary = firstSection.querySelector<HTMLElement>('.section-fold > summary')!
+      expect(doc.activeElement).toBe(sectionSummary)
+      expect(sectionSummary.closest('details')?.open).toBe(false)
+    },
+    120000,
+  )
+
+  test(
+    'a visible focused section row stays focused and mixed states fold then unfold',
+    async () => {
+      const value = document([
+        section(simplePatch('one', 'one!'), 'First section'),
+        section(simplePatch('two', 'two!'), 'Second section'),
+      ])
+      const dom = loadReport(renderReport(value, clientBundle), {
+        url: 'https://reports.example/r/report-id',
+      })
+      const doc = dom.document as unknown as Document
+      runReportClient()
+
+      const button = doc.querySelector<HTMLButtonElement>('[data-fold-all]')!
+      const folds = [...doc.querySelectorAll<HTMLDetailsElement>('details.section-fold')]
+      const label = () => button.querySelector('[data-fold-all-label]')?.textContent
+
+      // A section summary is never hidden by its own fold, so focus must not move.
+      const summary = folds[0]!.querySelector<HTMLElement>(':scope > summary')!
+      summary.focus()
+      button.click()
+      expect(doc.activeElement).toBe(summary)
+
+      // Mixed state: any open section means the global control folds all.
+      folds[1]!.open = true
+      expect(label()).toBe('Fold all')
+      button.click()
+      expect(folds.every((fold) => !fold.open)).toBe(true)
+      expect(label()).toBe('Unfold all')
+
+      button.click()
+      expect(folds.every((fold) => fold.open)).toBe(true)
+      expect(label()).toBe('Fold all')
+    },
+    120000,
+  )
 })
diff --git a/test/report.test.ts b/test/report.test.ts
index b0ef928..1eb310e 100644
--- a/test/report.test.ts
+++ b/test/report.test.ts
@@ -360,6 +360,21 @@ describe('renderReport shell', () => {
     expect(html).toContain('value="unified" checked')
   })
 
+  test('the review map carries one global fold control after the layout toggle', () => {
+    const html = renderReport(document([section(simplePatch(), 'Plain')]), stubClient)
+    const form = html.indexOf('<form class="layout-form"')
+    const fold = html.indexOf('data-fold-all')
+    const label = html.indexOf('<p class="review-map-label">')
+
+    expect(fold).toBeGreaterThan(form)
+    expect(label).toBeGreaterThan(fold)
+    expect(html).toContain('<button type="button" class="fold-all" data-fold-all')
+    expect(html).toContain('aria-label="Fold all review sections"')
+    expect(html).toContain('data-fold-all-label>Fold all<')
+    expect(html).toContain('.review-controls {')
+    expect(html).toContain('.fold-all:focus-visible')
+  })
+
   test('review map lists every section in document order with zero-padded anchors and counts', () => {
     const value = document([
       section(simplePatch('a', 'b'), 'First section'),