diff --git a/.github/workflows/app-tests.yaml b/.github/workflows/app-tests.yaml
index f90b1838..1b8a009d 100644
--- a/.github/workflows/app-tests.yaml
+++ b/.github/workflows/app-tests.yaml
@@ -146,6 +146,11 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y ffmpeg
           ffmpeg -version
+          # Keep video assertions enabled while avoiding agent-browser 0.21.2's
+          # undersized JPEG probe on Ubuntu FFmpeg 6 (see the compatibility shim).
+          echo "CUJ_FFMPEG_REAL=$(command -v ffmpeg)" >> "$GITHUB_ENV"
+          chmod +x app/test/browser/compat-bin/ffmpeg
+          echo "$GITHUB_WORKSPACE/app/test/browser/compat-bin" >> "$GITHUB_PATH"
 
       - name: Checkout Runme (direct Jupyter bridge)
         uses: actions/checkout@v4
diff --git a/app/src/components/Actions/ActionOutputItems.tsx b/app/src/components/Actions/ActionOutputItems.tsx
index 869fad91..4dd59ccb 100644
--- a/app/src/components/Actions/ActionOutputItems.tsx
+++ b/app/src/components/Actions/ActionOutputItems.tsx
@@ -108,7 +108,7 @@ function ActionOutputItemView({
     )
   } else {
     content = (
-      <pre className="whitespace-pre-wrap break-words text-xs leading-relaxed text-nb-text">
+      <pre className="whitespace-pre-wrap [overflow-wrap:anywhere] text-xs leading-relaxed text-nb-text">
         {text}
       </pre>
     )
diff --git a/app/src/components/Actions/Actions.test.tsx b/app/src/components/Actions/Actions.test.tsx
index bd5257ef..129ae4b8 100644
--- a/app/src/components/Actions/Actions.test.tsx
+++ b/app/src/components/Actions/Actions.test.tsx
@@ -1333,7 +1333,7 @@ describe('Actions tabs', () => {
     })
   })
 
-  it('enables horizontal scrolling for wide notebook content', () => {
+  it('bounds the notebook scroll area so wide blocks scroll within cells', () => {
     const uri = 'local://file/wide-table.runme.md'
     contextMocks.currentDoc = uri
     contextMocks.workspaceDocuments = [
@@ -1361,9 +1361,9 @@ describe('Actions tabs', () => {
 
     expect(scrollViewport).toBeTruthy()
     expect(scrollRoot).toBeTruthy()
-    expect(scrollRoot?.className).not.toContain('overflow-x-hidden')
+    expect(scrollRoot?.className).toContain('notebook-scroll-area')
     expect((scrollViewport as HTMLElement | undefined)?.style.overflowX).toBe(
-      'scroll'
+      'hidden'
     )
   })
 
diff --git a/app/src/components/Actions/Actions.tsx b/app/src/components/Actions/Actions.tsx
index cab8b27f..6945b4a3 100644
--- a/app/src/components/Actions/Actions.tsx
+++ b/app/src/components/Actions/Actions.tsx
@@ -3730,8 +3730,8 @@ function NotebookTabContent({
       <ScrollArea
         key={`scroll-${docUri}`}
         type="auto"
-        scrollbars="both"
-        className="h-full min-w-0 max-w-full flex-1"
+        scrollbars="vertical"
+        className="notebook-scroll-area h-full min-w-0 max-w-full flex-1"
         data-document-id={docUri}
       >
         {/* Full-width notebook column with horizontal padding for breathing room.
diff --git a/app/src/components/Actions/MarkdownCell.test.tsx b/app/src/components/Actions/MarkdownCell.test.tsx
index 61a815e5..462a63a1 100644
--- a/app/src/components/Actions/MarkdownCell.test.tsx
+++ b/app/src/components/Actions/MarkdownCell.test.tsx
@@ -83,6 +83,41 @@ function renderMarkdownCell(
 }
 
 describe("MarkdownCell", () => {
+  it.each(["Scrollable code block", "Scrollable table"])(
+    "preserves focus on %s when its cell becomes active",
+    async (label) => {
+      const stub = new StubCellData(
+        create(parser_pb.CellSchema, {
+          refId: "md-nested-scroll-focus",
+          kind: parser_pb.CellKind.MARKUP,
+          languageId: "markdown",
+          value: "```sh\necho hello\n```\n\n| Column |\n| --- |\n| value |",
+        }),
+      );
+      /** Model the parent activation caused by a descendant's focus event. */
+      function ActivatingCell() {
+        const [active, setActive] = React.useState(false);
+        return (
+          <MarkdownCell
+            cellData={stub as unknown as CellData}
+            selectedLanguage="markdown"
+            languageSelectId="lang-nested-focus"
+            languageOptions={[{ label: "Markdown", value: "markdown" }]}
+            onLanguageChange={() => {}}
+            isActiveCell={active}
+            activeFocusRole="rendered"
+            isWindowFocused
+            onFocusRoleChange={() => setActive(true)}
+          />
+        );
+      }
+      render(<ActivatingCell />);
+      const scroller = screen.getByLabelText(label);
+      await act(async () => scroller.focus());
+      expect(document.activeElement).toBe(scroller);
+    },
+  );
+
   it("starts markdown cells in editor mode when persisted focus target is editor", () => {
     const cell = create(parser_pb.CellSchema, {
       refId: "md-active-editor",
diff --git a/app/src/components/Actions/MarkdownCell.tsx b/app/src/components/Actions/MarkdownCell.tsx
index 41c30c16..9bd8db73 100644
--- a/app/src/components/Actions/MarkdownCell.tsx
+++ b/app/src/components/Actions/MarkdownCell.tsx
@@ -108,7 +108,7 @@ const markdownComponents: Components = {
     }
     return (
       <code
-        className={`block bg-nb-surface-2 p-3 rounded-md text-[12.6px] font-mono overflow-x-auto ${className}`}
+        className={`block text-[12.6px] font-mono ${className}`}
         {...props}
       >
         {children}
@@ -118,6 +118,8 @@ const markdownComponents: Components = {
   pre: ({ children, ...props }) => (
     <pre
       className="bg-nb-surface-2 p-3 rounded-md overflow-x-auto mb-3"
+      tabIndex={0}
+      aria-label="Scrollable code block"
       {...props}
     >
       {children}
@@ -132,7 +134,12 @@ const markdownComponents: Components = {
     </blockquote>
   ),
   table: ({ children, ...props }) => (
-    <div className="overflow-x-auto mb-3">
+    <div
+      className="overflow-x-auto mb-3"
+      tabIndex={0}
+      role="region"
+      aria-label="Scrollable table"
+    >
       <table className="min-w-full border border-nb-border-strong" {...props}>
         {children}
       </table>
@@ -283,6 +290,18 @@ const MarkdownCell = memo(
     const shouldOwnFocus = isActiveCell && isWindowFocused
     const tracksActiveCell = Boolean(onFocusRoleChange)
 
+    /**
+     * Activating a cell also runs focus restoration. Preserve focus already
+     * inside it, so a newly focused table, code scroller, or link receives
+     * the user's next key instead of losing focus to the rendered wrapper.
+     */
+    const restoreRenderedFocus = useCallback(() => {
+      const root = renderedRef.current
+      if (root && !root.contains(root.ownerDocument.activeElement)) {
+        root.focus({ preventScroll: true })
+      }
+    }, [])
+
     // Enforce invariant: empty cells must be in edit mode.
     // This handles external changes (undo/redo, sync) that clear the value.
     useEffect(() => {
@@ -327,15 +346,22 @@ const MarkdownCell = memo(
         return
       }
       setRendered(true)
-      renderedRef.current?.focus({ preventScroll: true })
-    }, [activeFocusRole, canOpenSource, readOnly, shouldOwnFocus, value])
+      restoreRenderedFocus()
+    }, [
+      activeFocusRole,
+      canOpenSource,
+      readOnly,
+      restoreRenderedFocus,
+      shouldOwnFocus,
+      value,
+    ])
 
     useEffect(() => {
       if (!shouldOwnFocus || activeFocusRole !== 'rendered' || !rendered) {
         return
       }
-      renderedRef.current?.focus({ preventScroll: true })
-    }, [activeFocusRole, rendered, shouldOwnFocus])
+      restoreRenderedFocus()
+    }, [activeFocusRole, rendered, restoreRenderedFocus, shouldOwnFocus])
 
     useEffect(() => {
       if (!tracksActiveCell || isActiveCell || rendered || !value.trim()) {
@@ -562,7 +588,7 @@ const MarkdownCell = memo(
           // Rendered markdown view - double-click or keyboard to edit
           <div
             id={`markdown-rendered-${cell.refId}`}
-            className="cursor-text rounded-nb-md border border-transparent p-4 transition-[border-color,background-color,box-shadow] duration-200 hover:border-nb-border hover:bg-nb-surface-2/60 hover:shadow-nb-xs"
+            className="notebook-markdown cursor-text rounded-nb-md border border-transparent p-4 transition-[border-color,background-color,box-shadow] duration-200 hover:border-nb-border hover:bg-nb-surface-2/60 hover:shadow-nb-xs"
             onDoubleClick={canOpenSource ? handleDoubleClick : undefined}
             onKeyDown={canOpenSource ? handleRenderedKeyDown : undefined}
             ref={renderedRef}
diff --git a/app/src/index.css b/app/src/index.css
index 01c12391..b28bf57b 100644
--- a/app/src/index.css
+++ b/app/src/index.css
@@ -1,6 +1,28 @@
 @import url("https://fonts.googleapis.com/css2?family=PT+Sans:wght@400;700&family=Fira+Mono:wght@400;500&display=swap");
 @import "tailwindcss";
 
+/* Notebook width belongs to the viewport, never to the widest descendant.
+   Radix Themes gives its generated content wrapper width: fit-content; even a
+   locally scrollable table/output can then widen every sibling cell. Override
+   that wrapper only for notebook panes, leaving other ScrollAreas unchanged.
+   Keep this outside Tailwind layers so the unlayered Radix rule cannot win.
+   Wide blocks own their horizontal scrolling inside the bounded notebook. */
+.notebook-scroll-area > .rt-ScrollAreaViewport > div {
+  width: 100%;
+  max-width: 100%;
+}
+
+/* Unlike break-word, anywhere also reduces intrinsic minimum width. This is
+   for prose/inline code/links; fenced code retains whitespace and scrolls. */
+.notebook-markdown {
+  overflow-wrap: anywhere;
+}
+
+.notebook-markdown pre,
+.notebook-markdown table {
+  overflow-wrap: normal;
+}
+
 /* ═══════════════════════════════════════════════════════════════════
    1. Breakpoints (build-time only — no CSS vars emitted)
    ═══════════════════════════════════════════════════════════════════ */
diff --git a/app/test/browser/compat-bin/ffmpeg b/app/test/browser/compat-bin/ffmpeg
new file mode 100755
index 00000000..625e670c
--- /dev/null
+++ b/app/test/browser/compat-bin/ffmpeg
@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# agent-browser 0.21.2 disables buffering and probes only 32 bytes of its
+# streamed JPEG input. Ubuntu's FFmpeg 6 can then exit before discovering the
+# image dimensions. Use FFmpeg's normal input buffering/probing for this exact
+# recorder signature. Preserve every other argument, output, and exit status.
+# Remove this shim when the pinned recorder no longer emits these flags.
+args=("$@")
+if [[ " ${*} " == *" -f image2pipe -c:v mjpeg "* ]]; then
+  args=()
+  while (($#)); do
+    case "$1:${2-}" in
+      -avioflags:direct|-fpsprobesize:0|-probesize:32|-analyzeduration:0)
+        shift 2 ;;
+      *) args+=("$1"); shift ;;
+    esac
+  done
+fi
+exec "${CUJ_FFMPEG_REAL:?Set CUJ_FFMPEG_REAL to the system ffmpeg}" "${args[@]}"
diff --git a/app/test/browser/run-cuj-scenarios.ts b/app/test/browser/run-cuj-scenarios.ts
index 062f314a..95f1f09c 100644
--- a/app/test/browser/run-cuj-scenarios.ts
+++ b/app/test/browser/run-cuj-scenarios.ts
@@ -80,6 +80,7 @@ function fetchWithTimeout(
 
 const SCENARIO_DRIVERS = [
   join(SCRIPT_DIR, "test-scenario-colab-export-recovery.ts"),
+  join(SCRIPT_DIR, "test-scenario-horizontal-rendering.ts"),
   join(SCRIPT_DIR, "test-scenario-drive-revision-recovery.ts"),
   join(SCRIPT_DIR, "test-scenario-html-cell.ts"),
   join(SCRIPT_DIR, "test-scenario-hello-world.ts"),
diff --git a/app/test/browser/test-scenario-horizontal-rendering.ts b/app/test/browser/test-scenario-horizontal-rendering.ts
new file mode 100644
index 00000000..6fea948c
--- /dev/null
+++ b/app/test/browser/test-scenario-horizontal-rendering.ts
@@ -0,0 +1,221 @@
+/** CUJ: docs-dev/cujs/horizontal-rendering.md.
+ * Use stored output and synthetic Markdown: no runner or authenticated service
+ * is needed. Layout must be checked in Chromium; jsdom has no layout engine.
+ */
+import { execFileSync } from 'node:child_process'
+import { mkdirSync, readFileSync, writeFileSync } from 'node:fs'
+import { dirname, join, resolve } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const here = dirname(fileURLToPath(import.meta.url))
+const dir = here.endsWith('/.generated') ? dirname(here) : here
+const output = join(dir, 'test-output')
+const url = process.env.CUJ_FRONTEND_URL ?? 'http://localhost:5173'
+const session =
+  process.env.AGENT_BROWSER_SESSION?.trim() ||
+  `horizontal-rendering-${Date.now()}`
+const profile = process.env.AGENT_BROWSER_PROFILE?.trim()
+const headed = process.env.AGENT_BROWSER_HEADED?.toLowerCase() === 'true'
+const keepOpen = process.env.AGENT_BROWSER_KEEP_OPEN?.toLowerCase() === 'true'
+const movie = join(output, 'scenario-horizontal-rendering.webm')
+const uri = 'local://file/horizontal-rendering-regression'
+const fixture = JSON.parse(
+  readFileSync(
+    resolve(dir, '../fixtures/notebooks/horizontal-rendering.json'),
+    'utf8'
+  )
+)
+mkdirSync(output, { recursive: true })
+let passed = 0
+let failed = 0
+
+/** Invoke the existing CUJ browser tool with argument boundaries preserved. */
+function browser(...args: string[]): string {
+  const options = ['--session', session]
+  if (profile) options.push('--profile', profile)
+  if (headed) options.push('--headed')
+  return execFileSync('agent-browser', [...options, ...args], {
+    encoding: 'utf8',
+    timeout: 30000,
+    maxBuffer: 4 * 1024 * 1024,
+  }).trim()
+}
+
+/** Measure visible elements only: inactive tabs deliberately remain mounted. */
+function inspectLayout() {
+  const column = document.querySelector<HTMLElement>(
+    '[role="tabpanel"][data-state="active"] #notebook-column'
+  )!
+  const viewport = column.closest<HTMLElement>('.rt-ScrollAreaViewport')!
+  const markdown = column.querySelector<HTMLElement>('.notebook-markdown')!
+  const paragraph = markdown.querySelector<HTMLElement>('p')!
+  const tables = [...markdown.querySelectorAll('table')]
+  const pre = markdown.querySelector<HTMLElement>('pre')!
+  const output = column.querySelector<HTMLElement>(
+    '[data-testid="cell-output-item"] pre'
+  )!
+  const rect = paragraph.getBoundingClientRect()
+  const pane = viewport.getBoundingClientRect()
+  return {
+    viewport: viewport.clientWidth,
+    column: column.clientWidth,
+    scroll: viewport.scrollWidth,
+    proseFits: rect.left >= pane.left && rect.right <= pane.right + 1,
+    proseWraps:
+      rect.height > parseFloat(getComputedStyle(paragraph).lineHeight) * 1.5,
+    smallTableFits:
+      tables[0].scrollWidth <= tables[0].parentElement!.clientWidth + 1,
+    wideTableScrolls:
+      tables[1].parentElement!.scrollWidth >
+        tables[1].parentElement!.clientWidth &&
+      getComputedStyle(tables[1].parentElement!).overflowX === 'auto',
+    codeScrolls:
+      pre.scrollWidth > pre.clientWidth &&
+      getComputedStyle(pre).overflowX === 'auto',
+    scrollRegionsFocusable:
+      pre.tabIndex === 0 && tables[1].parentElement!.tabIndex === 0,
+    outputFits: output.scrollWidth <= output.clientWidth + 1,
+    outputIntact: output.textContent!.includes(
+      'unbroken_output_identifier_'.repeat(500)
+    ),
+    siblingFits:
+      column.querySelectorAll('.notebook-markdown').length === 2 &&
+      [...column.querySelectorAll<HTMLElement>('.notebook-markdown')].every(
+        (cell) => {
+          const bounds = cell.getBoundingClientRect()
+          return bounds.left >= pane.left && bounds.right <= pane.right + 1
+        }
+      ),
+  }
+}
+
+/** Fail on missing elements rather than treating empty measurements as success. */
+function check(name: string, ok: boolean) {
+  if (ok) passed++
+  else failed++
+  console.log(`[${ok ? 'PASS' : 'FAIL'}] ${name}`)
+}
+
+try {
+  browser('open', url)
+  browser('record', 'start', movie)
+  // Recording may replace the context. Seed only after recording has started.
+  browser('wait', '--fn', 'Boolean(window.app?.localNotebooks)')
+  browser(
+    'eval',
+    `(async () => {
+    const store = window.app?.localNotebooks;
+    if (!store) throw new Error('Local notebook store is not ready');
+    await store.files.put({
+      id:${JSON.stringify(uri)}, uri:${JSON.stringify(uri)},
+      name:'horizontal-rendering.json', remoteId:'',
+      doc:${JSON.stringify(JSON.stringify(fixture))},
+      parent:'local://folder/local', updatedAt:new Date().toISOString(),
+      lastSynced:'', lastRemoteChecksum:''
+    });
+    sessionStorage.setItem('runme/openNotebooks',JSON.stringify([{uri:${JSON.stringify(uri)},name:'horizontal-rendering.json',type:'file',children:[],parents:['local://folder/local']} ]));
+    sessionStorage.setItem('runme/currentDoc',${JSON.stringify(uri)});
+  })()`
+  )
+  browser('reload')
+  browser('wait', '#markdown-rendered-markup_horizontal_rendering')
+  browser('wait', '[data-testid="cell-output-item"] pre')
+  browser('wait', '--fn', 'document.fonts.status === "loaded"')
+  // Exercise a normal and a narrow viewport; the sidebar may consume width too.
+  for (const width of [1280, 900]) {
+    browser('set', 'viewport', String(width), '900')
+    browser('wait', '300')
+    const raw = browser('eval', `(${inspectLayout.toString()})()`)
+    let result = JSON.parse(raw)
+    if (typeof result === 'string') result = JSON.parse(result)
+    writeFileSync(
+      join(output, `scenario-horizontal-rendering-${width}.json`),
+      JSON.stringify(result, null, 2)
+    )
+    check(
+      `${width}: notebook width is bounded`,
+      result.column <= result.viewport + 1 &&
+        result.scroll <= result.viewport + 1
+    )
+    for (const key of [
+      'proseFits',
+      'proseWraps',
+      'smallTableFits',
+      'wideTableScrolls',
+      'codeScrolls',
+      'scrollRegionsFocusable',
+      'outputFits',
+      'outputIntact',
+      'siblingFits',
+    ])
+      check(`${width}: ${key}`, result[key] === true)
+    browser(
+      'screenshot',
+      join(output, `scenario-horizontal-rendering-${width}.png`)
+    )
+    // Capture the blocks the geometry checks cover, not just the first screen.
+    // Pressing Right must move each local scroll region; focusability alone
+    // would miss keyboard handlers that accidentally swallow navigation.
+    for (const [name, selector] of [
+      ['code', '#markdown-rendered-markup_horizontal_rendering pre'],
+      [
+        'table',
+        '#markdown-rendered-markup_horizontal_rendering [role="region"]:has(th:nth-child(12))',
+      ],
+    ]) {
+      browser('scrollintoview', selector)
+      browser('focus', selector)
+      const before = JSON.parse(
+        browser(
+          'eval',
+          `document.querySelector(${JSON.stringify(selector)}).scrollLeft`
+        )
+      )
+      browser('press', 'ArrowRight')
+      browser(
+        'wait',
+        '--fn',
+        `document.querySelector(${JSON.stringify(selector)}).scrollLeft > ${Number(before)}`
+      )
+      check(`${width}: ${name} scrolls with the keyboard`, true)
+      browser(
+        'screenshot',
+        join(output, `scenario-horizontal-rendering-${width}-${name}.png`)
+      )
+    }
+    browser('scrollintoview', '[data-testid="cell-output-item"]')
+    browser(
+      'screenshot',
+      join(output, `scenario-horizontal-rendering-${width}-output.png`)
+    )
+    browser('scrollintoview', '#markdown-rendered-markup_horizontal_sibling')
+    browser(
+      'screenshot',
+      join(output, `scenario-horizontal-rendering-${width}-sibling.png`)
+    )
+    browser(
+      'scrollintoview',
+      '#markdown-rendered-markup_horizontal_rendering h1'
+    )
+  }
+} catch (error) {
+  check(String(error), false)
+} finally {
+  try {
+    browser('record', 'stop')
+  } catch (error) {
+    check(`Could not finalize browser recording: ${error}`, false)
+  }
+  if (!keepOpen) {
+    try {
+      browser('close')
+    } catch {
+      /* Preserve test result during cleanup. */
+    }
+  }
+}
+console.log(`Movie: ${movie}`)
+console.log(
+  `Assertions: ${passed + failed}, Passed: ${passed}, Failed: ${failed}`
+)
+process.exitCode = failed ? 1 : 0
diff --git a/app/test/fixtures/notebooks/horizontal-rendering.json b/app/test/fixtures/notebooks/horizontal-rendering.json
new file mode 100644
index 00000000..64e47042
--- /dev/null
+++ b/app/test/fixtures/notebooks/horizontal-rendering.json
@@ -0,0 +1,36 @@
+{
+  "metadata": {},
+  "cells": [
+    {
+      "kind": 1,
+      "refId": "markup_horizontal_rendering",
+      "languageId": "markdown",
+      "value": "# Horizontal rendering regression\n\n## Outcome\n\n**Readable prose stays within the notebook pane.** This paragraph must wrap naturally even when a different cell contains a very long URL, code line or output. The notebook should never require horizontal scrolling to read ordinary text.\n\n## Timeline\n\n| Time | Evidence |\n| --- | --- |\n| 10:00 | A two-column table should wrap its descriptions and remain readable at narrow widths. |\n| 10:05 | Wider content below must not increase the width of this paragraph or its siblings. |\n\n## Long inline identifier\n\n`unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_unbroken_identifier_`\n\n## Wide code block\n\n```sh\necho long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_long_command_argument_\n```\n\n## Wide table\n\n| Column 1 | Column 2 | Column 3 | Column 4 | Column 5 | Column 6 | Column 7 | Column 8 | Column 9 | Column 10 | Column 11 | Column 12 |\n| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |\n| value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ | value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_value_without_spaces_ |\n\n## After the wide content\n\nThis final paragraph should also fit within the notebook pane. All code and table content remains accessible through its own local scrolling.\n",
+      "metadata": {}
+    },
+    {
+      "kind": 2,
+      "refId": "code_horizontal_output",
+      "languageId": "javascript",
+      "value": "// Stored output fixture; no backend execution is required.",
+      "metadata": {},
+      "outputs": [
+        {
+          "items": [
+            {
+              "mime": "text/plain",
+              "data": "Long output URL: https://example.test/unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_ou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identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_unbroken_output_identifier_"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "kind": 1,
+      "refId": "markup_horizontal_sibling",
+      "languageId": "markdown",
+      "metadata": {},
+      "value": "## Independent sibling cell\n\nThis cell must stay within the viewport even when earlier cells have very wide content. Unicode stays intact: caf\u00e9 \ud83d\udc68\u200d\ud83d\udc69\u200d\ud83d\udc67\u200d\ud83d\udc66 \u65e5\u672c\u8a9e."
+    }
+  ]
+}
diff --git a/docs-dev/cujs/README.md b/docs-dev/cujs/README.md
index 2708d9f2..f93733fa 100644
--- a/docs-dev/cujs/README.md
+++ b/docs-dev/cujs/README.md
@@ -8,6 +8,9 @@ from `docs-dev/cujs/`.
 
 ## Current CUJs
 
+- [horizontal-rendering.md](horizontal-rendering.md) — viewport-bounded prose with locally scrolling wide
+  tables/code and wrapping outputs; verified at normal and narrow widths.
+
 - `hello-world-local-notebook.md` — baseline notebook flow:
   - configure local runner,
   - open local notebook,
diff --git a/docs-dev/cujs/horizontal-rendering.md b/docs-dev/cujs/horizontal-rendering.md
new file mode 100644
index 00000000..354b1372
--- /dev/null
+++ b/docs-dev/cujs/horizontal-rendering.md
@@ -0,0 +1,46 @@
+# Read notebooks containing wide Markdown and outputs
+
+Regression: a wide table, code block, or output expands Radix's fit-content
+wrapper and makes every paragraph wrap beyond the visible pane.
+
+## Design decisions
+
+- The viewport owns notebook width. Constrain Radix's generated inner wrapper
+  to 100% width and max-width, scoped to `.notebook-scroll-area`. `w-full` on
+  the notebook alone refers to the already expanded wrapper and cannot fix it.
+- The notebook scrolls vertically. Horizontal scrolling belongs to individual
+  tables and fenced code blocks, with keyboard-focusable scroll regions.
+- Prose, links, inline identifiers and plain-text outputs use `overflow-wrap:
+  anywhere`. Unlike `break-word`, it also reduces intrinsic minimum width.
+- Tables use normal wrapping so wide columns stay readable and scroll locally.
+  Fenced code preserves whitespace; the `pre`, not a second nested `code`
+  scroller, owns overflow. Do not clip content to conceal a sizing regression.
+- Scope the unlayered CSS override to notebook panes; other Radix scroll areas,
+  including the tab rail and review panels, keep their existing behavior.
+- Restoring active-cell focus must preserve a focused descendant. Otherwise
+  activating a cell steals focus from its table/code scroller and prevents
+  the first keyboard scroll. Test this with a previously inactive cell.
+
+Full design and before/after evidence:
+[20260910_horizontal_rendering.runme](https://runme.gateway.unified-0.internal.api.openai.org/?doc=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F1m4Zx1EPXjrrXKYdzgXBhTatI5nYLj-ES%2Fview).
+
+## Fixture and acceptance criteria
+
+`app/test/fixtures/notebooks/horizontal-rendering.json` includes ordinary prose,
+a two-column table, long inline code, a long fenced command, a 12-column table,
+a long stored output URL, and a sibling Markdown cell. It contains no real
+incident data or service credentials and needs no backend execution.
+
+Run `test-scenario-horizontal-rendering.ts` through the canonical CUJ runner.
+At 1280px and 900px browser widths, require:
+
+1. Notebook column and scroll width do not exceed the viewport (1px tolerance).
+2. Paragraphs fit and wrap; the small table fits.
+3. Wide table and code block overflow locally, with keyboard focus available.
+4. Long output remains intact and wraps within its output panel.
+5. The sibling cell is present; earlier wide content does not expand the column.
+
+Record measurements, screenshots and video under `app/test/browser/test-output/`.
+Also inspect the wide blocks after scrolling locally and test resizing with
+Explorer/Comments panels open. A CSS-class test in jsdom cannot establish these
+layout properties; use browser geometry and inspect screenshots.