diff --git a/src/renderer/modals/subtitle-sidebar.test.ts b/src/renderer/modals/subtitle-sidebar.test.ts
index 9a5aceb..fb5d6e3 100644
--- a/src/renderer/modals/subtitle-sidebar.test.ts
+++ b/src/renderer/modals/subtitle-sidebar.test.ts
@@ -299,6 +299,100 @@ test('subtitle sidebar rows support keyboard activation', async () => {
   }
 });
 
+test('subtitle sidebar renders hour-long cue timestamps as HH:MM:SS', async () => {
+  const globals = globalThis as typeof globalThis & { window?: unknown; document?: unknown };
+  const previousWindow = globals.window;
+  const previousDocument = globals.document;
+
+  const snapshot: SubtitleSidebarSnapshot = {
+    cues: [{ startTime: 3665, endTime: 3670, text: 'long cue' }],
+    currentSubtitle: {
+      text: 'long cue',
+      startTime: 3665,
+      endTime: 3670,
+    },
+    config: {
+      enabled: true,
+      autoOpen: false,
+      layout: 'overlay',
+      toggleKey: 'Backslash',
+      pauseVideoOnHover: false,
+      autoScroll: true,
+      maxWidth: 420,
+      opacity: 0.92,
+      backgroundColor: 'rgba(54, 58, 79, 0.88)',
+      textColor: '#cad3f5',
+      fontFamily: '"Iosevka Aile", sans-serif',
+      fontSize: 17,
+      timestampColor: '#a5adcb',
+      activeLineColor: '#f5bde6',
+      activeLineBackgroundColor: 'rgba(138, 173, 244, 0.22)',
+      hoverLineBackgroundColor: 'rgba(54, 58, 79, 0.84)',
+    },
+  };
+
+  Object.defineProperty(globalThis, 'window', {
+    configurable: true,
+    value: {
+      electronAPI: {
+        getSubtitleSidebarSnapshot: async () => snapshot,
+        sendMpvCommand: () => {},
+      } as unknown as ElectronAPI,
+    },
+  });
+  Object.defineProperty(globalThis, 'document', {
+    configurable: true,
+    value: {
+      createElement: () => createCueRow(),
+      body: {
+        classList: createClassList(),
+      },
+      documentElement: {
+        style: {
+          setProperty: () => {},
+        },
+      },
+    },
+  });
+
+  try {
+    const state = createRendererState();
+    const cueList = createListStub();
+    const ctx = {
+      dom: {
+        overlay: { classList: createClassList() },
+        subtitleSidebarModal: {
+          classList: createClassList(['hidden']),
+          setAttribute: () => {},
+          style: { setProperty: () => {} },
+          addEventListener: () => {},
+        },
+        subtitleSidebarContent: {
+          classList: createClassList(),
+          getBoundingClientRect: () => ({ width: 420 }),
+        },
+        subtitleSidebarClose: { addEventListener: () => {} },
+        subtitleSidebarStatus: { textContent: '' },
+        subtitleSidebarList: cueList,
+      },
+      state,
+    };
+
+    const modal = createSubtitleSidebarModal(ctx as never, {
+      modalStateReader: { isAnyModalOpen: () => false },
+    });
+
+    await modal.openSubtitleSidebarModal();
+
+    const firstRow = cueList.children[0]!;
+    assert.equal(firstRow.attributes['aria-label'], 'Jump to subtitle at 01:01:05');
+    assert.equal((firstRow.children[0] as { textContent: string }).textContent, '01:01:05');
+  } finally {
+    Object.defineProperty(globalThis, 'window', { configurable: true, value: previousWindow });
+    Object.defineProperty(globalThis, 'document', { configurable: true, value: previousDocument });
+  }
+});
+
 test('subtitle sidebar does not open when the feature is disabled', async () => {
   const globals = globalThis as typeof globalThis & { window?: unknown; document?: unknown };
   const previousWindow = globals.window;
@@ -1501,6 +1595,127 @@ test('subtitle sidebar embedded layout reserves and releases mpv right margin',
   }
 });
 
+test('subtitle sidebar embedded layout measures reserved width after embedded classes apply', async () => {
+  const globals = globalThis as typeof globalThis & { window?: unknown; document?: unknown };
+  const previousWindow = globals.window;
+  const previousDocument = globals.document;
+  const mpvCommands: Array<Array<string | number>> = [];
+  const rootStyleCalls: Array<[string, string]> = [];
+  const bodyClassList = createClassList();
+  const contentClassList = createClassList();
+
+  const snapshot: SubtitleSidebarSnapshot = {
+    cues: [{ startTime: 1, endTime: 2, text: 'first' }],
+    currentSubtitle: {
+      text: 'first',
+      startTime: 1,
+      endTime: 2,
+    },
+    currentTimeSec: 1.1,
+    config: {
+      enabled: true,
+      autoOpen: false,
+      layout: 'embedded',
+      toggleKey: 'Backslash',
+      pauseVideoOnHover: false,
+      autoScroll: true,
+      maxWidth: 420,
+      opacity: 0.92,
+      backgroundColor: 'rgba(54, 58, 79, 0.88)',
+      textColor: '#cad3f5',
+      fontFamily: '"Iosevka Aile", sans-serif',
+      fontSize: 17,
+      timestampColor: '#a5adcb',
+      activeLineColor: '#f5bde6',
+      activeLineBackgroundColor: 'rgba(138, 173, 244, 0.22)',
+      hoverLineBackgroundColor: 'rgba(54, 58, 79, 0.84)',
+    },
+  };
+
+  Object.defineProperty(globalThis, 'window', {
+    configurable: true,
+    value: {
+      innerWidth: 1200,
+      electronAPI: {
+        getSubtitleSidebarSnapshot: async () => snapshot,
+        sendMpvCommand: (command: Array<string | number>) => {
+          mpvCommands.push(command);
+        },
+      } as unknown as ElectronAPI,
+      addEventListener: () => {},
+      removeEventListener: () => {},
+    },
+  });
+  Object.defineProperty(globalThis, 'document', {
+    configurable: true,
+    value: {
+      createElement: () => createCueRow(),
+      body: {
+        classList: bodyClassList,
+      },
+      documentElement: {
+        style: {
+          setProperty: (name: string, value: string) => {
+            rootStyleCalls.push([name, value]);
+          },
+        },
+      },
+    },
+  });
+
+  try {
+    const state = createRendererState();
+    const ctx = {
+      dom: {
+        overlay: { classList: createClassList() },
+        subtitleSidebarModal: {
+          classList: createClassList(['hidden']),
+          setAttribute: () => {},
+          style: { setProperty: () => {} },
+          addEventListener: () => {},
+        },
+        subtitleSidebarContent: {
+          classList: contentClassList,
+          getBoundingClientRect: () => ({
+            width: contentClassList.contains('subtitle-sidebar-content-embedded') ? 300 : 0,
+          }),
+        },
+        subtitleSidebarClose: { addEventListener: () => {} },
+        subtitleSidebarStatus: { textContent: '' },
+        subtitleSidebarList: createListStub(),
+      },
+      platform: {
+        shouldToggleMouseIgnore: false,
+      },
+      state,
+    };
+
+    const modal = createSubtitleSidebarModal(ctx as never, {
+      modalStateReader: { isAnyModalOpen: () => false },
+    });
+
+    await modal.openSubtitleSidebarModal();
+
+    assert.ok(bodyClassList.contains('subtitle-sidebar-embedded-open'));
+    assert.ok(
+      rootStyleCalls.some(
+        ([name, value]) => name === '--subtitle-sidebar-reserved-width' && value === '300px',
+      ),
+    );
+    assert.ok(
+      mpvCommands.some(
+        (command) =>
+          command[0] === 'set_property' &&
+          command[1] === 'video-margin-ratio-right' &&
+          command[2] === 0.25,
+      ),
+    );
+  } finally {
+    Object.defineProperty(globalThis, 'window', { configurable: true, value: previousWindow });
+    Object.defineProperty(globalThis, 'document', { configurable: true, value: previousDocument });
+  }
+});
+
 test('subtitle sidebar embedded layout restores macOS and Windows passthrough outside sidebar hover', async () => {
   const globals = globalThis as typeof globalThis & { window?: unknown; document?: unknown };
   const previousWindow = globals.window;
diff --git a/src/renderer/modals/subtitle-sidebar.ts b/src/renderer/modals/subtitle-sidebar.ts
index 745c146..59582db 100644
--- a/src/renderer/modals/subtitle-sidebar.ts
+++ b/src/renderer/modals/subtitle-sidebar.ts
@@ -38,8 +38,16 @@ function normalizeCueText(text: string): string {
 
 function formatCueTimestamp(seconds: number): string {
   const totalSeconds = Math.max(0, Math.floor(seconds));
-  const mins = Math.floor(totalSeconds / 60);
+  const hours = Math.floor(totalSeconds / 3600);
+  const mins = Math.floor((totalSeconds % 3600) / 60);
   const secs = totalSeconds % 60;
+  if (hours > 0) {
+    return [
+      String(hours).padStart(2, '0'),
+      String(mins).padStart(2, '0'),
+      String(secs).padStart(2, '0'),
+    ].join(':');
+  }
   return `${String(mins).padStart(2, '0')}:${String(secs).padStart(2, '0')}`;
 }
 
@@ -162,10 +170,11 @@ export function createSubtitleSidebarModal(
 
   function syncEmbeddedSidebarLayout(): void {
     const config = ctx.state.subtitleSidebarConfig;
-    const reservedWidthPx = getReservedSidebarWidthPx();
-    const embedded = Boolean(config && config.layout === 'embedded' && reservedWidthPx > 0);
+    const wantsEmbedded = Boolean(
+      config && config.layout === 'embedded' && ctx.state.subtitleSidebarModalOpen,
+    );
 
-    if (embedded) {
+    if (wantsEmbedded) {
       ctx.dom.subtitleSidebarContent.classList.add('subtitle-sidebar-content-embedded');
       ctx.dom.subtitleSidebarModal.classList.add('subtitle-sidebar-modal-embedded');
       document.body.classList.add('subtitle-sidebar-embedded-open');
@@ -174,6 +183,8 @@ export function createSubtitleSidebarModal(
       ctx.dom.subtitleSidebarModal.classList.remove('subtitle-sidebar-modal-embedded');
       document.body.classList.remove('subtitle-sidebar-embedded-open');
     }
+    const reservedWidthPx = wantsEmbedded ? getReservedSidebarWidthPx() : 0;
+    const embedded = wantsEmbedded && reservedWidthPx > 0;
     document.documentElement.style.setProperty(
       '--subtitle-sidebar-reserved-width',
       `${Math.max(0, Math.round(reservedWidthPx))}px`,