diff --git a/packages/cli/src/ui/components/AskUserDialog.test.tsx b/packages/cli/src/ui/components/AskUserDialog.test.tsx
index 5810a9f922..320ba321f5 100644
--- a/packages/cli/src/ui/components/AskUserDialog.test.tsx
+++ b/packages/cli/src/ui/components/AskUserDialog.test.tsx
@@ -962,5 +962,70 @@ describe('AskUserDialog', () => {
 
       expect(lastFrame()).toMatchSnapshot();
     });
+
+    it('truncates long content when availableTerminalHeight is small', async () => {
+      const longContent = Array.from(
+        { length: 30 },
+        (_, i) => `Line ${i + 1}`,
+      ).join('\n');
+      const questionWithLongContent: Question[] = [
+        {
+          question: 'Approve this plan?',
+          header: 'Plan',
+          options: [{ label: 'Yes', description: '' }],
+          content: longContent,
+        },
+      ];
+
+      const { lastFrame } = renderWithProviders(
+        <AskUserDialog
+          questions={questionWithLongContent}
+          onSubmit={vi.fn()}
+          onCancel={vi.fn()}
+        />,
+        {
+          width: 120,
+          uiState: {
+            availableTerminalHeight: 15,
+          },
+        },
+      );
+
+      await waitFor(() => {
+        expect(lastFrame()).toMatchSnapshot();
+      });
+    });
+
+    it('does not truncate content when availableTerminalHeight is undefined', () => {
+      const content = Array.from(
+        { length: 10 },
+        (_, i) => `Line ${i + 1}`,
+      ).join('\n');
+      const questionWithContent: Question[] = [
+        {
+          question: 'Approve this plan?',
+          header: 'Plan',
+          options: [{ label: 'Yes', description: '' }],
+          content,
+        },
+      ];
+
+      const { lastFrame } = renderWithProviders(
+        <AskUserDialog
+          questions={questionWithContent}
+          onSubmit={vi.fn()}
+          onCancel={vi.fn()}
+        />,
+        {
+          width: 120,
+          uiState: {
+            availableTerminalHeight: undefined,
+          },
+        },
+      );
+
+      expect(lastFrame()).not.toContain('lines hidden');
+      expect(lastFrame()).toMatchSnapshot();
+    });
   });
 });
diff --git a/packages/cli/src/ui/components/AskUserDialog.tsx b/packages/cli/src/ui/components/AskUserDialog.tsx
index 886698a408..269f5e9353 100644
--- a/packages/cli/src/ui/components/AskUserDialog.tsx
+++ b/packages/cli/src/ui/components/AskUserDialog.tsx
@@ -31,6 +31,17 @@ import { useTabbedNavigation } from '../hooks/useTabbedNavigation.js';
 import { DialogFooter } from './shared/DialogFooter.js';
 import { MaxSizedBox } from './shared/MaxSizedBox.js';
 
+// Width reduction for content inside the dialog border/padding
+const CONTENT_WIDTH_REDUCTION = 4;
+
+// Height consumed by dialog chrome surrounding the content area:
+// - Border top/bottom: 2
+// - Question text + marginBottom: 2
+// - Footer (keyboard hints): 2
+// - Options/input minimum: 4
+// - Buffer for tab header when present: 2
+const DIALOG_CHROME_HEIGHT = 12;
+
 interface AskUserDialogState {
   answers: { [key: string]: string };
   isEditingCustomOption: boolean;
@@ -283,11 +294,16 @@ const TextQuestionView: React.FC<TextQuestionViewProps> = ({
       {progressHeader}
       {question.content && (
         <Box marginBottom={1} flexDirection="column">
-          <MaxSizedBox maxHeight={uiState?.availableTerminalHeight}>
+          <MaxSizedBox
+            maxHeight={
+              uiState?.availableTerminalHeight &&
+              uiState.availableTerminalHeight - DIALOG_CHROME_HEIGHT
+            }
+          >
             <MarkdownDisplay
               text={question.content}
               isPending={false}
-              terminalWidth={availableWidth - 4} // Adjust for parent border/padding
+              terminalWidth={availableWidth - CONTENT_WIDTH_REDUCTION}
             />
           </MaxSizedBox>
         </Box>
@@ -722,11 +738,16 @@ const ChoiceQuestionView: React.FC<ChoiceQuestionViewProps> = ({
       {progressHeader}
       {question.content && (
         <Box marginBottom={1} flexDirection="column">
-          <MaxSizedBox maxHeight={uiState?.availableTerminalHeight}>
+          <MaxSizedBox
+            maxHeight={
+              uiState?.availableTerminalHeight &&
+              uiState.availableTerminalHeight - DIALOG_CHROME_HEIGHT
+            }
+          >
             <MarkdownDisplay
               text={question.content}
               isPending={false}
-              terminalWidth={availableWidth - 4} // Adjust for parent border/padding
+              terminalWidth={availableWidth - CONTENT_WIDTH_REDUCTION}
             />
           </MaxSizedBox>
         </Box>
diff --git a/packages/cli/src/ui/components/__snapshots__/AskUserDialog.test.tsx.snap b/packages/cli/src/ui/components/__snapshots__/AskUserDialog.test.tsx.snap
index 53f1e9d821..36b53636ae 100644
--- a/packages/cli/src/ui/components/__snapshots__/AskUserDialog.test.tsx.snap
+++ b/packages/cli/src/ui/components/__snapshots__/AskUserDialog.test.tsx.snap
@@ -11,6 +11,28 @@ exports[`AskUserDialog > Question content field > does not render content when c
 ╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯"
 `;
 
+exports[`AskUserDialog > Question content field > does not truncate content when availableTerminalHeight is undefined 1`] = `
+"╭──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
+│ Line 1                                                                                                               │
+│ Line 2                                                                                                               │
+│ Line 3                                                                                                               │
+│ Line 4                                                                                                               │
+│ Line 5                                                                                                               │
+│ Line 6                                                                                                               │
+│ Line 7                                                                                                               │
+│ Line 8                                                                                                               │
+│ Line 9                                                                                                               │
+│ Line 10                                                                                                              │
+│                                                                                                                      │
+│ Approve this plan?                                                                                                   │
+│                                                                                                                      │
+│ ● 1.  Yes                                                                                                            │
+│   2.  Enter a custom value                                                                                           │
+│                                                                                                                      │
+│ Enter to select · ↑/↓ to navigate · Esc to cancel                                                                    │
+╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯"
+`;
+
 exports[`AskUserDialog > Question content field > renders content in a choice question 1`] = `
 "╭──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
 │ Plan Details                                                                                                         │
@@ -44,6 +66,21 @@ exports[`AskUserDialog > Question content field > renders content in a text ques
 ╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯"
 `;
 
+exports[`AskUserDialog > Question content field > truncates long content when availableTerminalHeight is small 1`] = `
+"╭──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
+│ ... first 28 lines hidden ...                                                                                        │
+│ Line 29                                                                                                              │
+│ Line 30                                                                                                              │
+│                                                                                                                      │
+│ Approve this plan?                                                                                                   │
+│                                                                                                                      │
+│ ● 1.  Yes                                                                                                            │
+│   2.  Enter a custom value                                                                                           │
+│                                                                                                                      │
+│ Enter to select · ↑/↓ to navigate · Esc to cancel                                                                    │
+╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯"
+`;
+
 exports[`AskUserDialog > Question content field > uses customOptionPlaceholder for the Other option 1`] = `
 "╭──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
 │ Approve this?                                                                                                        │