diff --git a/packages/ui/src/components/chat/__tests__/issue-2903-subagent-status-line-only.test.tsx b/packages/ui/src/components/chat/__tests__/issue-2903-subagent-status-line-only.test.tsx
index 54ed84d2..3b314a22 100644
--- a/packages/ui/src/components/chat/__tests__/issue-2903-subagent-status-line-only.test.tsx
+++ b/packages/ui/src/components/chat/__tests__/issue-2903-subagent-status-line-only.test.tsx
@@ -138,14 +138,27 @@ const buildMaterializedSubagentSession = () => {
   return { messages, part };
 };
 
-const syncContext = (globalThis as unknown as {
+// SAFETY: sync-context.tsx publishes exactly these two keys on globalThis
+// (SYNC_CONTEXT_GLOBAL_KEY / SYNC_RUNTIME_CONTEXT_GLOBAL_KEY) so every module
+// instance shares one context identity; the cast only adds those two optional
+// keys to the global object type, and the guards below re-check presence.
+const syncGlobals = globalThis as {
   __openchamber_sync_context__?: React.Context<unknown>;
-}).__openchamber_sync_context__;
+  __openchamber_sync_runtime_context__?: React.Context<unknown>;
+};
+
+const syncContext = syncGlobals.__openchamber_sync_context__;
 
 if (!syncContext) {
   throw new Error('sync context was not published on globalThis by @/sync/sync-context');
 }
 
+const syncRuntimeContext = syncGlobals.__openchamber_sync_runtime_context__;
+
+if (!syncRuntimeContext) {
+  throw new Error('sync runtime context was not published on globalThis by @/sync/sync-context');
+}
+
 describe('issue #2903 busy embedded subagent status-line-only', () => {
   test('cold disabled reads hide a fully materialized 14-message subagent; enabled reads return all 14', async () => {
     const dom = installMinimalDom();
@@ -173,7 +186,16 @@ describe('issue #2903 busy embedded subagent status-line-only', () => {
     });
 
     const system = { childStores, messageLoader: {}, sdk: {}, runtimeKey: 'test', directory: DIRECTORY };
-    const Provider = syncContext.Provider as React.Provider<unknown>;
+    // Mirrors SyncProvider's own nesting: system context outer, runtime inner.
+    // Directory-scoped hooks read the runtime context, so the harness must
+    // provide it with a currentDirectory source for the store lookups.
+    const runtime = {
+      childStores,
+      messageLoader: {},
+      sdk: {},
+      runtimeKey: 'test',
+      currentDirectory: { get: () => DIRECTORY, subscribe: () => () => undefined },
+    };
     let inactiveCount = -1;
     let activeCount = -1;
     let enabled = false;
@@ -188,15 +210,22 @@ describe('issue #2903 busy embedded subagent status-line-only', () => {
       return null;
     };
 
+    const renderHarness = () =>
+      React.createElement(
+        syncContext.Provider,
+        { value: system },
+        React.createElement(syncRuntimeContext.Provider, { value: runtime }, React.createElement(Harness)),
+      );
+
     try {
       await act(async () => {
-        root.render(React.createElement(Provider, { value: system }, React.createElement(Harness)));
+        root.render(renderHarness());
       });
       expect(inactiveCount).toBe(0);
 
       enabled = true;
       await act(async () => {
-        root.render(React.createElement(Provider, { value: system }, React.createElement(Harness)));
+        root.render(renderHarness());
       });
       expect(activeCount).toBe(14);
     } finally {
diff --git a/packages/ui/src/components/desktop/WindowsWindowControls.tsx b/packages/ui/src/components/desktop/WindowsWindowControls.tsx
index 4d257e30..b74fdcfb 100644
--- a/packages/ui/src/components/desktop/WindowsWindowControls.tsx
+++ b/packages/ui/src/components/desktop/WindowsWindowControls.tsx
@@ -142,7 +142,9 @@ export const WindowsWindowControls = React.memo(function WindowsWindowControls({
       <div
         className={cn(
           'app-region-no-drag group/wctl flex h-8 shrink-0 items-center',
-          isLeft ? 'mr-1' : 'ml-1',
+          // macOS-style circles keep an edge inset on the right (the header's
+          // flush pr-0 is a Windows-caption convention, classic style only).
+          isLeft ? 'mr-1' : 'ml-1 mr-3',
         )}
         aria-label={t('header.windowControls.groupAria')}
       >
@@ -207,7 +209,11 @@ export const WindowsWindowControls = React.memo(function WindowsWindowControls({
         type="button"
         className={cn(
           buttonClassName,
-          'hover:bg-[var(--status-error-background)] hover:text-[var(--status-error-foreground)]',
+          // Hover pairs the solid error red with its authored on-red
+          // foreground (the --destructive pairing). The error-background wash
+          // is a banner surface tint, not a glyph-button hover: against it the
+          // on-solid foreground is unreadable in both modes.
+          'hover:bg-[var(--status-error)] hover:text-[var(--status-error-foreground)]',
         )}
         onClick={() => { void invokeDesktop('desktop_close_current_window'); }}
         title={t('header.windowControls.close')}
diff --git a/packages/ui/src/components/layout/Header.tsx b/packages/ui/src/components/layout/Header.tsx
index f8a3f331..7c1f3d3e 100644
--- a/packages/ui/src/components/layout/Header.tsx
+++ b/packages/ui/src/components/layout/Header.tsx
@@ -1356,6 +1356,14 @@ export const Header: React.FC = () => {
       return undefined;
     }
 
+    // Custom in-window controls (frameless Electron, right side) own the right
+    // edge: no inline padding, so the pr-0 class applies and the close button
+    // sits flush with the window corner per Windows conventions. Only the
+    // browser's native window-controls overlay reserves padding + right inset.
+    if (usesFramelessChrome && windowControlsSide === 'right') {
+      return undefined;
+    }
+
     return {
       // Left inset is handled by the no-drag spacer (see renderDesktop); only
       // the right inset / titlebar height are owned by the window-controls overlay.
@@ -1363,7 +1371,7 @@ export const Header: React.FC = () => {
       minHeight: 'max(3rem, var(--oc-wco-titlebar-height, 0px))',
       height: 'max(3rem, var(--oc-wco-titlebar-height, 0px))',
     };
-  }, [isDesktopApp, isVSCode, usesFramelessChrome]);
+  }, [isDesktopApp, isVSCode, usesFramelessChrome, windowControlsSide]);
 
   const updateHeaderHeight = React.useCallback(() => {
     if (typeof document === 'undefined') {