diff --git a/apps/desktop/e2e/session-workbar.spec.ts b/apps/desktop/e2e/session-workbar.spec.ts
index 22a6ae701d..c090b996f2 100644
--- a/apps/desktop/e2e/session-workbar.spec.ts
+++ b/apps/desktop/e2e/session-workbar.spec.ts
@@ -144,7 +144,7 @@ async function waitForCompanionForkId(page: Page, sourceSessionId: string) {
 }
 
 async function setRightWorkbarWidth(page: Page, width: number) {
-  const layoutOwner = page.locator('.maka-workbar-layout-vars');
+  const layoutOwner = page.locator('.appFrame');
   const workbar = page.locator('.maka-session-workbar[data-placement="right"]');
   await expect(layoutOwner).toHaveCount(1);
   await expect(workbar).toBeVisible();
@@ -160,6 +160,40 @@ async function setRightWorkbarWidth(page: Page, width: number) {
   return workbar;
 }
 
+test('a wide right workbar keeps a long session title and Share action outside the panel', async ({
+  window: page,
+}) => {
+  const { sessionId } = await createSession(page, 'create long title workbar session');
+  const longTitle =
+    'Investigate why the completed plan session title overlaps the token usage dashboard';
+  await page.evaluate(
+    ({ id, title }) => window.maka.sessions.rename(id, title),
+    { id: sessionId, title: longTitle },
+  );
+
+  const identity = page.locator('[data-maka-contract="titlebar-identity"]');
+  const share = page.getByRole('button', { name: '分享此任务' });
+  await expect(identity).toContainText('Investigate why the completed plan session title');
+  await expect(share).toBeVisible();
+
+  await page.getByRole('button', { name: '打开用量追踪' }).click();
+  const workbar = await setRightWorkbarWidth(page, 600);
+  await expect(
+    page.locator('[data-maka-contract="session-inspector"]'),
+  ).toBeVisible();
+
+  const [identityBox, workbarBox] = await Promise.all([
+    identity.boundingBox(),
+    workbar.boundingBox(),
+  ]);
+  expect(identityBox).not.toBeNull();
+  expect(workbarBox).not.toBeNull();
+  expect(identityBox!.x + identityBox!.width).toBeLessThanOrEqual(workbarBox!.x);
+
+  await share.click();
+  await expect(page.getByText('分享任务', { exact: true })).toBeVisible();
+});
+
 test('narrow right workbar keeps launcher shortcuts and side-chat send button inside', async ({
   window: page,
 }) => {
diff --git a/apps/desktop/renderer-architecture.json b/apps/desktop/renderer-architecture.json
index a163a5c3e0..acc7bd8ecd 100644
--- a/apps/desktop/renderer-architecture.json
+++ b/apps/desktop/renderer-architecture.json
@@ -899,7 +899,7 @@
           "react": 1
         },
         "importSpecifiers": 124,
-        "nonTriviaTokens": 15588
+        "nonTriviaTokens": 15573
       },
       "src/renderer/use-app-shell-composer-quotes.ts": {
         "importDeclarations": 2,
diff --git a/apps/desktop/src/renderer/app-shell.tsx b/apps/desktop/src/renderer/app-shell.tsx
index 8c8f20fa33..e3738afcb1 100644
--- a/apps/desktop/src/renderer/app-shell.tsx
+++ b/apps/desktop/src/renderer/app-shell.tsx
@@ -24,7 +24,6 @@ import {
   useMemo,
   useRef,
   useState,
-  type CSSProperties,
   type ComponentProps,
   type Dispatch,
   type SetStateAction,
@@ -2673,13 +2672,7 @@ function AppShellContent({
          `data-sidebar-state`. Writing both here would duplicate the constant;
          writing this one unconditionally would bury the other, since an inline
          custom property outranks any rule that redefines it. */
-      style={
-        sessionListCollapsed
-          ? undefined
-          : ({
-              '--maka-sidenav-width': `${sessionListWidth}px`,
-            } as CSSProperties)
-      }
+      style={workbar.getFrameStyle(sessionListCollapsed, sessionListWidth)}
     >
       <LiveTurnReconciler
         controller={sessionUiController}
diff --git a/apps/desktop/src/renderer/features/workbar/controller/use-workbar-controller.ts b/apps/desktop/src/renderer/features/workbar/controller/use-workbar-controller.ts
index c400d6060f..88c0c5564d 100644
--- a/apps/desktop/src/renderer/features/workbar/controller/use-workbar-controller.ts
+++ b/apps/desktop/src/renderer/features/workbar/controller/use-workbar-controller.ts
@@ -25,6 +25,7 @@ import {
   useRef,
   useState,
   type ComponentProps,
+  type CSSProperties,
 } from 'react';
 import type { ClientCapabilityResponse } from '@maka/core/client-capability-grant';
 import type { QuoteRef } from '@maka/core/events';
@@ -101,6 +102,7 @@ export interface UseWorkbarControllerInput {
 
 export interface WorkbarController {
   host: WorkbarHostModel;
+  getFrameStyle(sidebarCollapsed: boolean, sidebarWidth: number): CSSProperties;
   commands: WorkbarControllerCommands;
   selectors: WorkbarControllerSelectors;
   /**
@@ -702,6 +704,17 @@ export function useWorkbarController(
   );
 
   return {
+    getFrameStyle: (sidebarCollapsed, sidebarWidth) =>
+      ({
+        '--maka-session-workbar-width': `${layout.workbarWidth}px`,
+        // The reserve assumes the only side placement is `right`; add a
+        // placement guard here if left-side workbars are introduced.
+        '--maka-titlebar-workbar-reserve':
+          input.available && !layout.workbarCollapsed
+            ? 'calc(var(--maka-session-workbar-width) + var(--agents-content-area-gap))'
+            : '0px',
+        ...(sidebarCollapsed ? {} : { '--maka-sidenav-width': `${sidebarWidth}px` }),
+      }) as CSSProperties,
     commands,
     LiveContextUsageProbe,
     selectors: {
diff --git a/apps/desktop/src/renderer/features/workbar/ui/workbar-host.tsx b/apps/desktop/src/renderer/features/workbar/ui/workbar-host.tsx
index 08af527931..2cce85524e 100644
--- a/apps/desktop/src/renderer/features/workbar/ui/workbar-host.tsx
+++ b/apps/desktop/src/renderer/features/workbar/ui/workbar-host.tsx
@@ -127,7 +127,6 @@ export function WorkbarHost({ model: props }: { model: WorkbarHostModel }) {
   const toast = useToast();
   const copy = getShellCopy(locale).app;
   const style = {
-    '--maka-session-workbar-width': `${props.rightWidth}px`,
     '--maka-session-bottom-panel-height': `${props.bottomHeight}px`,
   } as CSSProperties;
 
diff --git a/apps/desktop/src/renderer/styles/shell-layout.css b/apps/desktop/src/renderer/styles/shell-layout.css
index ce6ea21dd8..98a2adf640 100644
--- a/apps/desktop/src/renderer/styles/shell-layout.css
+++ b/apps/desktop/src/renderer/styles/shell-layout.css
@@ -273,7 +273,10 @@
      the OS reports (macOS: traffic lights on the left; Windows: caption buttons
      on the right; Linux: neither, so the design floor stands). */
   padding-left: var(--maka-titlebar-gutter-left);
-  padding-right: calc(var(--space-6) + var(--maka-titlebar-overlay-right-width));
+  padding-right: calc(
+    var(--space-6) + var(--maka-titlebar-overlay-right-width) +
+      var(--maka-titlebar-workbar-reserve, 0px)
+  );
   -webkit-app-region: drag;
 
   /* Three columns, not a flex row, because the middle one has to line up with