fix(ui): prevent empty tool-group border stubs after filtering (#21852)

Co-authored-by: jacob314 <jacob314@gmail.com>

packages/cli/src/ui/components/messages/ToolGroupMessage.test.tsx

@@ -69,6 +69,11 @@ describe('<ToolGroupMessage />', () => {
       ui: { errorVerbosity: 'full' },
     },
   });
+  const lowVerbositySettings = createMockSettings({
+    merged: {
+      ui: { errorVerbosity: 'low' },
+    },
+  });
 
   describe('Golden Snapshots', () => {
     it('renders single successful tool call', async () => {
@@ -721,6 +726,245 @@ describe('<ToolGroupMessage />', () => {
       expect(lastFrame({ allowEmpty: true })).toBe('');
       unmount();
     });
+
+    it('does not render a bottom-border fragment when all tools are filtered out', async () => {
+      const toolCalls = [
+        createToolCall({
+          callId: 'hidden-error-tool',
+          name: 'error-tool',
+          status: CoreToolCallStatus.Error,
+          resultDisplay: 'Hidden in low verbosity',
+          isClientInitiated: false,
+        }),
+      ];
+      const item = createItem(toolCalls);
+
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={item}
+          toolCalls={toolCalls}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: lowVerbositySettings,
+        },
+      );
+
+      await waitUntilReady();
+      expect(lastFrame({ allowEmpty: true })).toBe('');
+      unmount();
+    });
+
+    it('still renders explicit closing slices for split static/pending groups', async () => {
+      const toolCalls: IndividualToolCallDisplay[] = [];
+      const item = createItem(toolCalls);
+
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={item}
+          toolCalls={toolCalls}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: fullVerbositySettings,
+        },
+      );
+
+      await waitUntilReady();
+      expect(lastFrame({ allowEmpty: true })).not.toBe('');
+      unmount();
+    });
+
+    it('does not render a border fragment when plan-mode tools are filtered out', async () => {
+      const toolCalls = [
+        createToolCall({
+          callId: 'plan-write',
+          name: WRITE_FILE_DISPLAY_NAME,
+          approvalMode: ApprovalMode.PLAN,
+          status: CoreToolCallStatus.Success,
+          resultDisplay: 'Plan file written',
+        }),
+      ];
+      const item = createItem(toolCalls);
+
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={item}
+          toolCalls={toolCalls}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: fullVerbositySettings,
+        },
+      );
+
+      await waitUntilReady();
+      expect(lastFrame({ allowEmpty: true })).toBe('');
+      unmount();
+    });
+
+    it('does not render a border fragment when only confirming tools are present', async () => {
+      const toolCalls = [
+        createToolCall({
+          callId: 'confirm-only',
+          status: CoreToolCallStatus.AwaitingApproval,
+          confirmationDetails: {
+            type: 'info',
+            title: 'Confirm',
+            prompt: 'Proceed?',
+          },
+        }),
+      ];
+      const item = createItem(toolCalls);
+
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={item}
+          toolCalls={toolCalls}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: fullVerbositySettings,
+        },
+      );
+
+      await waitUntilReady();
+      expect(lastFrame({ allowEmpty: true })).toBe('');
+      unmount();
+    });
+
+    it('does not leave a border stub when transitioning from visible to fully filtered tools', async () => {
+      const visibleTools = [
+        createToolCall({
+          callId: 'visible-success',
+          name: 'visible-tool',
+          status: CoreToolCallStatus.Success,
+          resultDisplay: 'visible output',
+        }),
+      ];
+      const hiddenTools = [
+        createToolCall({
+          callId: 'hidden-error',
+          name: 'hidden-error-tool',
+          status: CoreToolCallStatus.Error,
+          resultDisplay: 'hidden output',
+          isClientInitiated: false,
+        }),
+      ];
+
+      const initialItem = createItem(visibleTools);
+      const hiddenItem = createItem(hiddenTools);
+
+      const firstRender = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={initialItem}
+          toolCalls={visibleTools}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: lowVerbositySettings,
+        },
+      );
+      await firstRender.waitUntilReady();
+      expect(firstRender.lastFrame()).toContain('visible-tool');
+      firstRender.unmount();
+
+      const secondRender = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={hiddenItem}
+          toolCalls={hiddenTools}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: lowVerbositySettings,
+        },
+      );
+      await secondRender.waitUntilReady();
+      expect(secondRender.lastFrame({ allowEmpty: true })).toBe('');
+      secondRender.unmount();
+    });
+
+    it('keeps visible tools rendered with many filtered tools (stress case)', async () => {
+      const visibleTool = createToolCall({
+        callId: 'visible-tool',
+        name: 'visible-tool',
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'visible output',
+      });
+      const hiddenTools = Array.from({ length: 50 }, (_, index) =>
+        createToolCall({
+          callId: `hidden-${index}`,
+          name: `hidden-error-${index}`,
+          status: CoreToolCallStatus.Error,
+          resultDisplay: `hidden output ${index}`,
+          isClientInitiated: false,
+        }),
+      );
+      const toolCalls = [visibleTool, ...hiddenTools];
+      const item = createItem(toolCalls);
+
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          {...baseProps}
+          item={item}
+          toolCalls={toolCalls}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: lowVerbositySettings,
+        },
+      );
+
+      await waitUntilReady();
+      const output = lastFrame();
+      expect(output).toContain('visible-tool');
+      expect(output).not.toContain('hidden-error-0');
+      expect(output).not.toContain('hidden-error-49');
+      unmount();
+    });
+
+    it('renders explicit closing slice even at very narrow terminal width', async () => {
+      const toolCalls: IndividualToolCallDisplay[] = [];
+      const item = createItem(toolCalls);
+
+      const { lastFrame, unmount, waitUntilReady } = renderWithProviders(
+        <ToolGroupMessage
+          item={item}
+          toolCalls={toolCalls}
+          terminalWidth={8}
+          borderTop={false}
+          borderBottom={true}
+        />,
+        {
+          config: baseMockConfig,
+          settings: fullVerbositySettings,
+        },
+      );
+
+      await waitUntilReady();
+      expect(lastFrame({ allowEmpty: true })).not.toBe('');
+      unmount();
+    });
   });
 
   describe('Plan Mode Filtering', () => {

packages/cli/src/ui/components/messages/ToolGroupMessage.tsx

@@ -141,11 +141,15 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
 
   const contentWidth = terminalWidth - TOOL_MESSAGE_HORIZONTAL_MARGIN;
 
-  // If all tools are filtered out (e.g., in-progress AskUser tools, confirming tools),
-  // only render if we need to close a border from previous
-  // tool groups. borderBottomOverride=true means we must render the closing border;
-  // undefined or false means there's nothing to display.
-  if (visibleToolCalls.length === 0 && borderBottomOverride !== true) {
+  // If all tools are filtered out (e.g., in-progress AskUser tools, low-verbosity
+  // internal errors, plan-mode hidden write/edit), we should not emit standalone
+  // border fragments. The only case where an empty group should render is the
+  // explicit "closing slice" (tools: []) used to bridge static/pending sections.
+  const isExplicitClosingSlice = allToolCalls.length === 0;
+  if (
+    visibleToolCalls.length === 0 &&
+    (!isExplicitClosingSlice || borderBottomOverride !== true)
+  ) {
     return null;
   }