diff --git a/src/tau_coding/tui/app.py b/src/tau_coding/tui/app.py
index 4ba902c63..7894db162 100644
--- a/src/tau_coding/tui/app.py
+++ b/src/tau_coding/tui/app.py
@@ -1654,6 +1654,10 @@ class TauTuiApp(App[None]):
         dock: top;
     }
 
+    Header.-tall {
+        height: 1;
+    }
+
     Footer {
         background: $tau-chrome-background;
         color: $tau-chrome-text;
@@ -2120,7 +2124,7 @@ def get_theme_variable_defaults(self) -> dict[str, str]:
 
     def compose(self) -> ComposeResult:
         """Compose the TUI widgets."""
-        yield Header()
+        yield Header(id="header")
         with Horizontal(id="workspace"):
             yield SessionSidebar(id="sidebar")
             with Vertical(id="main-pane"):
diff --git a/tests/test_tui_app.py b/tests/test_tui_app.py
index 3ca511d3a..2cb9c3bfc 100644
--- a/tests/test_tui_app.py
+++ b/tests/test_tui_app.py
@@ -3542,6 +3542,27 @@ async def test_tui_app_notifications_render_literal_markup_text() -> None:
     assert notification.markup is False
 
 
+@pytest.mark.anyio
+async def test_tui_app_clicking_header_does_not_resize_workspace() -> None:
+    app = TauTuiApp(FakeSession())
+
+    async with app.run_test(size=(120, 30)) as pilot:
+        header = app.query_one("#header")
+        workspace = app.query_one("#workspace")
+        sidebar = app.query_one("#sidebar")
+        assert sidebar.display is True
+        initial_header_height = header.region.height
+        initial_workspace_region = workspace.region
+        initial_sidebar_region = sidebar.region
+
+        await pilot.click("#header")
+        await pilot.pause()
+
+        assert header.region.height == initial_header_height == 1
+        assert workspace.region == initial_workspace_region
+        assert sidebar.region == initial_sidebar_region
+
+
 @pytest.mark.anyio
 async def test_tui_app_clicking_transcript_refocuses_prompt() -> None:
     app = TauTuiApp(FakeSession())