diff --git a/web/src/shell/AppShell.test.tsx b/web/src/shell/AppShell.test.tsx
index 116d696cd2..f07f857162 100644
--- a/web/src/shell/AppShell.test.tsx
+++ b/web/src/shell/AppShell.test.tsx
@@ -1161,6 +1161,12 @@ describe("Workspace rail maximize", () => {
       data: { available: true, root: null },
       isLoading: false,
     } as unknown as ReturnType<typeof useWorkspaceEnvironment>);
+    useChangedFilesMock.mockReturnValue({
+      data: {
+        available: true,
+        data: [{ path: "a.ts", name: "a.ts", status: "modified" as const, bytes: 1 }],
+      },
+    } as unknown as ReturnType<typeof useWorkspaceChangedFiles>);
     mockConversations([{ id: "conv_abc", permission_level: null }]);
 
     renderShell("/c/conv_abc");
@@ -1195,6 +1201,12 @@ describe("Workspace rail maximize", () => {
       data: { available: true, root: null },
       isLoading: false,
     } as unknown as ReturnType<typeof useWorkspaceEnvironment>);
+    useChangedFilesMock.mockReturnValue({
+      data: {
+        available: true,
+        data: [{ path: "a.ts", name: "a.ts", status: "modified" as const, bytes: 1 }],
+      },
+    } as unknown as ReturnType<typeof useWorkspaceChangedFiles>);
     mockConversations([{ id: "conv_abc", permission_level: null }]);
 
     renderShell("/c/conv_abc");
@@ -1218,6 +1230,12 @@ describe("Workspace rail maximize", () => {
       data: { available: true, root: null },
       isLoading: false,
     } as unknown as ReturnType<typeof useWorkspaceEnvironment>);
+    useChangedFilesMock.mockReturnValue({
+      data: {
+        available: true,
+        data: [{ path: "a.ts", name: "a.ts", status: "modified" as const, bytes: 1 }],
+      },
+    } as unknown as ReturnType<typeof useWorkspaceChangedFiles>);
     mockConversations([
       { id: "conv_abc", permission_level: null },
       { id: "conv_xyz", permission_level: null },
diff --git a/web/src/shell/WorkspacePanel.test.tsx b/web/src/shell/WorkspacePanel.test.tsx
index 8676b417ee..af9019226e 100644
--- a/web/src/shell/WorkspacePanel.test.tsx
+++ b/web/src/shell/WorkspacePanel.test.tsx
@@ -87,6 +87,7 @@ function renderWorkspace(
     selectedTerminalKey?: string | null;
     maximized?: boolean;
     liveness?: SessionLiveness;
+    changedCount?: number;
   } = {},
 ) {
   const openFileViewer = vi.fn();
@@ -105,7 +106,7 @@ function renderWorkspace(
         onRightRailTabChange={onRightRailTabChange}
         showFilesPanel
         showBrowserTab={overrides.showBrowserTab ?? false}
-        changedCount={0}
+        changedCount={overrides.changedCount ?? 0}
         showShellsTab={overrides.showShellsTab ?? false}
         terminalsLength={0}
         subagentsWorking={0}
@@ -537,15 +538,21 @@ describe('WorkspacePanel "+" new-tab menu', () => {
 
 describe("WorkspacePanel maximize", () => {
   it("shows a full-screen toggle pinned to the right and fires onToggleMaximized", () => {
-    const { onToggleMaximized } = renderWorkspace();
+    const { onToggleMaximized } = renderWorkspace({ changedCount: 1 });
 
     fireEvent.click(screen.getByRole("button", { name: "Full screen" }));
 
     expect(onToggleMaximized).toHaveBeenCalledTimes(1);
   });
 
+  it("hides the full-screen button when workspace has no changes and no open tabs", () => {
+    renderWorkspace({ changedCount: 0, openFiles: [] });
+
+    expect(screen.queryByRole("button", { name: "Full screen" })).toBeNull();
+  });
+
   it("swaps to the exit-full-screen affordance and covers the content region when maximized", () => {
-    renderWorkspace({ maximized: true });
+    renderWorkspace({ maximized: true, changedCount: 1 });
 
     // Label + pressed state flip so the icon reads as a minimize/exit control.
     const toggle = screen.getByRole("button", { name: "Exit full screen" });
@@ -572,7 +579,7 @@ describe("WorkspacePanel tab-strip layout (regression)", () => {
     // Two ml-auto siblings split the free space and strand the nav group
     // mid-strip. With no open tabs the single ml-auto lives on the maximize
     // button; the nav group must NOT also carry one.
-    renderWorkspace({ openFiles: [], showBrowserTab: true });
+    renderWorkspace({ openFiles: [], showBrowserTab: true, changedCount: 1 });
 
     expect(strip().querySelectorAll(".ml-auto")).toHaveLength(1);
     // It's the maximize button's wrapper (pins the button right).
@@ -586,7 +593,7 @@ describe("WorkspacePanel tab-strip layout (regression)", () => {
     // The nav tabs stay anchored on the LEFT with open tabs — the open-tabs
     // region renders to their right and the maximize button keeps the row's
     // single ml-auto. Two ml-auto siblings would split the free space.
-    renderWorkspace({ openFiles: ["src/App.tsx"], showBrowserTab: true });
+    renderWorkspace({ openFiles: ["src/App.tsx"], showBrowserTab: true, changedCount: 1 });
 
     expect(strip().querySelectorAll(".ml-auto")).toHaveLength(1);
     // The nav tablist stays left — no ml-auto of its own.
@@ -620,7 +627,7 @@ describe("WorkspacePanel tab-strip layout (regression)", () => {
   it("gives the full-screen button no left padding", () => {
     // The maximize button must not carry a pl-* gap — it sits flush against the
     // preceding nav icon like the rest of the strip.
-    renderWorkspace({ openFiles: [] });
+    renderWorkspace({ openFiles: [], changedCount: 1 });
     const fullScreen = screen.getByRole("button", { name: "Full screen" });
     expect(fullScreen.parentElement).not.toHaveClass("pl-0.5");
   });
diff --git a/web/src/shell/WorkspacePanel.tsx b/web/src/shell/WorkspacePanel.tsx
index faefe320e1..4b6db8f2f0 100644
--- a/web/src/shell/WorkspacePanel.tsx
+++ b/web/src/shell/WorkspacePanel.tsx
@@ -865,21 +865,27 @@ export function WorkspacePanel({
         {/* Maximize/minimize toggle, pinned to the rightmost edge via ml-auto,
             which absorbs the free space before it. When open tabs exist their
             ≥500px flex-1 region absorbs the space instead, so the button still
-            hugs the right. */}
-        <WorkspaceTabTooltip
-          label={maximized ? "Exit full screen" : "Full screen"}
-          className="ml-auto"
-        >
-          <button
-            type="button"
-            aria-label={maximized ? "Exit full screen" : "Full screen"}
-            aria-pressed={maximized}
-            onClick={onToggleMaximized}
-            className="flex size-8 shrink-0 items-center justify-center rounded-md text-muted-foreground transition-colors hover:bg-muted hover:text-foreground"
+            hugs the right. Hidden when the panel has no meaningful content. */}
+        {(changedCount > 0 || selectedFilePath !== null || selectedTerminalKey !== null) && (
+          <WorkspaceTabTooltip
+            label={maximized ? "Exit full screen" : "Full screen"}
+            className="ml-auto"
           >
-            {maximized ? <MinimizeIcon className="size-4" /> : <MaximizeIcon className="size-4" />}
-          </button>
-        </WorkspaceTabTooltip>
+            <button
+              type="button"
+              aria-label={maximized ? "Exit full screen" : "Full screen"}
+              aria-pressed={maximized}
+              onClick={onToggleMaximized}
+              className="flex size-8 shrink-0 items-center justify-center rounded-md text-muted-foreground transition-colors hover:bg-muted hover:text-foreground"
+            >
+              {maximized ? (
+                <MinimizeIcon className="size-4" />
+              ) : (
+                <MaximizeIcon className="size-4" />
+              )}
+            </button>
+          </WorkspaceTabTooltip>
+        )}
       </div>
       {/* Tab content — single slot. An open shell tab holds its xterm; a
           file tab holds FileViewer; the Files tab shows FilesPanel; the