diff --git a/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx b/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx
index 5ec2a18e06..752aed35c9 100644
--- a/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx
+++ b/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx
@@ -191,7 +191,7 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
         maxLinesLimit: maxLines,
       });
 
-      if (!contentMaxLines) return false;
+      if (contentMaxLines === undefined) return false;
 
       if (typeof tool.resultDisplay === 'string') {
         const text = tool.resultDisplay;
diff --git a/packages/cli/src/ui/components/messages/ToolResultDisplay.tsx b/packages/cli/src/ui/components/messages/ToolResultDisplay.tsx
index 1c29407e91..09dee9cd31 100644
--- a/packages/cli/src/ui/components/messages/ToolResultDisplay.tsx
+++ b/packages/cli/src/ui/components/messages/ToolResultDisplay.tsx
@@ -23,7 +23,10 @@ import { Scrollable } from '../shared/Scrollable.js';
 import { ScrollableList } from '../shared/ScrollableList.js';
 import { SCROLL_TO_ITEM_END } from '../shared/VirtualizedList.js';
 import { ACTIVE_SHELL_MAX_LINES } from '../../constants.js';
-import { calculateToolContentMaxLines } from '../../utils/toolLayoutUtils.js';
+import {
+  calculateToolContentMaxLines,
+  TOOL_RESULT_MIN_LINES_SHOWN,
+} from '../../utils/toolLayoutUtils.js';
 import { SubagentProgressDisplay } from './SubagentProgressDisplay.js';
 
 // Large threshold to ensure we don't cause performance issues for very large
@@ -61,6 +64,11 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
     maxLinesLimit: maxLines,
   });
 
+  const effectiveMaxHeight =
+    availableHeight !== undefined
+      ? Math.max(TOOL_RESULT_MIN_LINES_SHOWN, availableHeight)
+      : undefined;
+
   const combinedPaddingAndBorderWidth = 4;
   const childWidth = terminalWidth - combinedPaddingAndBorderWidth;
 
@@ -132,7 +140,7 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
   if (isAlternateBuffer && Array.isArray(truncatedResultDisplay)) {
     // If availableHeight is undefined, fallback to a safe default to prevents infinite loop
     // where Container grows -> List renders more -> Container grows.
-    const limit = maxLines ?? availableHeight ?? ACTIVE_SHELL_MAX_LINES;
+    const limit = maxLines ?? effectiveMaxHeight ?? ACTIVE_SHELL_MAX_LINES;
     const listHeight = Math.min(
       // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
       (truncatedResultDisplay as AnsiOutput).length,
@@ -205,7 +213,7 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
         diffContent={(truncatedResultDisplay as FileDiffResult).fileDiff}
         // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
         filename={(truncatedResultDisplay as FileDiffResult).fileName}
-        availableTerminalHeight={availableHeight}
+        availableTerminalHeight={effectiveMaxHeight}
         terminalWidth={childWidth}
       />
     );
@@ -219,7 +227,7 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
         // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
         data={truncatedResultDisplay as AnsiOutput}
         availableTerminalHeight={
-          isAlternateBuffer ? undefined : availableHeight
+          isAlternateBuffer ? undefined : effectiveMaxHeight
         }
         width={childWidth}
         maxLines={isAlternateBuffer ? undefined : maxLines}
@@ -233,7 +241,7 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
     return (
       <Scrollable
         width={childWidth}
-        maxHeight={maxLines ?? availableHeight}
+        maxHeight={maxLines ?? effectiveMaxHeight}
         hasFocus={hasFocus} // Allow scrolling via keyboard (Shift+Up/Down)
         scrollToBottom={true}
       >
@@ -245,7 +253,7 @@ export const ToolResultDisplay: React.FC<ToolResultDisplayProps> = ({
   return (
     <Box width={childWidth} flexDirection="column">
       <MaxSizedBox
-        maxHeight={availableHeight}
+        maxHeight={effectiveMaxHeight}
         maxWidth={childWidth}
         additionalHiddenLinesCount={hiddenLinesCount}
       >