Fix crash.

packages/cli/src/ui/components/AnsiOutput.tsx

@@ -35,11 +35,12 @@ export const AnsiOutputText: React.FC<AnsiOutputProps> = ({
       ? Math.min(availableHeightLimit, maxLines)
       : (availableHeightLimit ?? maxLines ?? DEFAULT_HEIGHT);
 
+  const arrayData = Array.isArray(data) ? data : [];
   const lastLines = disableTruncation
-    ? data
+    ? arrayData
     : numLinesRetained === 0
       ? []
-      : data.slice(-numLinesRetained);
+      : arrayData.slice(-numLinesRetained);
   return (
     <Box flexDirection="column" width={width} flexShrink={0} overflow="hidden">
       {lastLines.map((line: AnsiLine, lineIndex: number) => (

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

@@ -148,6 +148,9 @@ describe('ToolResultDisplay', () => {
     const diffResult = {
       fileDiff: 'diff content',
       fileName: 'test.ts',
+      filePath: 'test.ts',
+      originalContent: null,
+      newContent: 'new',
     };
     const { lastFrame, waitUntilReady, unmount } = await renderWithProviders(
       <ToolResultDisplay
@@ -222,6 +225,34 @@ describe('ToolResultDisplay', () => {
     unmount();
   });
 
+  it('renders unknown objects as stringified JSON', async () => {
+    const unknownObject = {
+      hello: 'world',
+      nested: {
+        value: 42,
+      },
+    };
+    const { lastFrame, waitUntilReady, unmount } = await renderWithProviders(
+      <ToolResultDisplay
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        resultDisplay={unknownObject as any}
+        terminalWidth={80}
+        availableTerminalHeight={20}
+      />,
+      {
+        config: makeFakeConfig({ useAlternateBuffer: false }),
+        settings: createMockSettings({ ui: { useAlternateBuffer: false } }),
+      },
+    );
+    await waitUntilReady();
+    const output = lastFrame();
+
+    expect(output).toContain('"hello": "world"');
+    expect(output).toContain('"value": 42');
+    expect(output).toMatchSnapshot();
+    unmount();
+  });
+
   it('does not fall back to plain text if availableHeight is set and not in alternate buffer', async () => {
     // availableHeight calculation: 20 - 1 - 5 = 14 > 3
     const { lastFrame, waitUntilReady, unmount } = await renderWithProviders(

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

@@ -12,9 +12,9 @@ import { AnsiOutputText, AnsiLineText } from '../AnsiOutput.js';
 import { SlicingMaxSizedBox } from '../shared/SlicingMaxSizedBox.js';
 import { theme } from '../../semantic-colors.js';
 import {
-  type AnsiOutput,
   type AnsiLine,
   isSubagentProgress,
+  type ToolResultDisplay as CoreToolResultDisplay,
 } from '@google/gemini-cli-core';
 import { useUIState } from '../../contexts/UIStateContext.js';
 import { tryParseJSON } from '../../../utils/jsonoutput.js';
@@ -27,7 +27,7 @@ import { calculateToolContentMaxLines } from '../../utils/toolLayoutUtils.js';
 import { SubagentProgressDisplay } from './SubagentProgressDisplay.js';
 
 export interface ToolResultDisplayProps {
-  resultDisplay: string | object | undefined;
+  resultDisplay: CoreToolResultDisplay | undefined;
   availableTerminalHeight?: number;
   terminalWidth: number;
   renderOutputAsMarkdown?: boolean;
@@ -36,11 +36,6 @@ export interface ToolResultDisplayProps {
   overflowDirection?: 'top' | 'bottom';
 }
 
-interface FileDiffResult {
-  fileDiff: string;
-  fileName: string;
-}
-
 export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
   resultDisplay,
   availableTerminalHeight,
@@ -84,7 +79,7 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
     return null;
   }
 
-  const renderContent = (contentData: string | object | undefined) => {
+  const renderContent = (contentData: CoreToolResultDisplay | undefined) => {
     // Check if string content is valid JSON and pretty-print it
     const prettyJSON =
       typeof contentData === 'string' ? tryParseJSON(contentData) : null;
@@ -123,28 +118,27 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
           {contentData}
         </Text>
       );
-    } else if (typeof contentData === 'object' && 'fileDiff' in contentData) {
+    } else if (
+      contentData &&
+      typeof contentData === 'object' &&
+      'fileDiff' in contentData
+    ) {
       content = (
         <DiffRenderer
-          diffContent={
-            // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
-            (contentData as FileDiffResult).fileDiff
-          }
-          // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
-          filename={(contentData as FileDiffResult).fileName}
+          diffContent={contentData.fileDiff}
+          filename={contentData.fileName}
           availableTerminalHeight={availableHeight}
           terminalWidth={childWidth}
         />
       );
-    } else {
+    } else if (Array.isArray(contentData)) {
       const shouldDisableTruncation =
         isAlternateBuffer ||
         (availableTerminalHeight === undefined && maxLines === undefined);
 
       content = (
         <AnsiOutputText
-          // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
-          data={contentData as AnsiOutput}
+          data={contentData}
           availableTerminalHeight={
             isAlternateBuffer ? undefined : availableHeight
           }
@@ -153,6 +147,12 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
           disableTruncation={shouldDisableTruncation}
         />
       );
+    } else {
+      content = (
+        <Text wrap="wrap" color={theme.text.primary}>
+          {JSON.stringify(contentData, null, 2)}
+        </Text>
+      );
     }
 
     // Final render based on session mode
@@ -178,18 +178,13 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
     // Virtualized path for large ANSI arrays
     if (Array.isArray(resultDisplay)) {
       const limit = maxLines ?? availableHeight ?? ACTIVE_SHELL_MAX_LINES;
-      const listHeight = Math.min(
-        // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
-        (resultDisplay as AnsiOutput).length,
-        limit,
-      );
+      const listHeight = Math.min(resultDisplay.length, limit);
 
       return (
         <Box width={childWidth} flexDirection="column" maxHeight={listHeight}>
           <ScrollableList
             width={childWidth}
-            // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
-            data={resultDisplay as AnsiOutput}
+            data={resultDisplay}
             renderItem={renderVirtualizedAnsiLine}
             estimatedItemHeight={() => 1}
             keyExtractor={keyExtractor}

packages/cli/src/ui/components/messages/__snapshots__/ToolResultDisplay.test.tsx.snap

@@ -36,6 +36,16 @@ exports[`ToolResultDisplay > renders string result as plain text when renderOutp
 "
 `;
 
+exports[`ToolResultDisplay > renders unknown objects as stringified JSON 1`] = `
+"{
+  "hello": "world",
+  "nested": {
+    "value": 42
+  }
+}
+"
+`;
+
 exports[`ToolResultDisplay > truncates very long string results 1`] = `
 "... 249 hidden (Ctrl+O) ...
 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa