feat: add double-click to expand/collapse large paste placeholders

docs/cli/keyboard-shortcuts.md

@@ -124,3 +124,6 @@ available combinations.
   single-line input, navigate backward or forward through prompt history.
 - `Number keys (1-9, multi-digit)` inside selection dialogs: Jump directly to
   the numbered radio option and confirm when the full number is entered.
+- `Double-click` on a paste placeholder (`[Pasted Text: X lines]`) in alternate
+  buffer mode: Expand to view full content inline. Double-click again to
+  collapse.

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

@@ -11,10 +11,11 @@ import { Box, Text, useStdout, type DOMElement } from 'ink';
 import { SuggestionsDisplay, MAX_WIDTH } from './SuggestionsDisplay.js';
 import { theme } from '../semantic-colors.js';
 import { useInputHistory } from '../hooks/useInputHistory.js';
-import type { TextBuffer } from './shared/text-buffer.js';
 import {
+  type TextBuffer,
   logicalPosToOffset,
   PASTED_TEXT_PLACEHOLDER_REGEX,
+  getTransformUnderCursor,
 } from './shared/text-buffer.js';
 import { cpSlice, cpLen, toCodePoints } from '../utils/textUtils.js';
 import chalk from 'chalk';
@@ -52,8 +53,10 @@ import { useUIState } from '../contexts/UIStateContext.js';
 import { useSettings } from '../contexts/SettingsContext.js';
 import { StreamingState } from '../types.js';
 import { useMouseClick } from '../hooks/useMouseClick.js';
+import { useMouseDoubleClick } from '../hooks/useMouseDoubleClick.js';
 import { useMouse, type MouseEvent } from '../contexts/MouseContext.js';
 import { useUIActions } from '../contexts/UIActionsContext.js';
+import { useAlternateBuffer } from '../hooks/useAlternateBuffer.js';
 
 /**
  * Returns if the terminal can be trusted to handle paste events atomically
@@ -391,6 +394,40 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
     { isActive: focus },
   );
 
+  const isAlternateBuffer = useAlternateBuffer();
+
+  // Double-click to expand/collapse paste placeholders
+  useMouseDoubleClick(
+    innerBoxRef,
+    (_event, relX, relY) => {
+      if (!isAlternateBuffer) return;
+
+      const logicalPos = buffer.getLogicalPositionFromVisual(
+        buffer.visualScrollRow + relY,
+        relX,
+      );
+      if (!logicalPos) return;
+
+      // Check for paste placeholder (collapsed state)
+      const transform = getTransformUnderCursor(
+        logicalPos.row,
+        logicalPos.col,
+        buffer.transformationsByLine,
+      );
+      if (transform?.type === 'paste' && transform.id) {
+        buffer.togglePasteExpansion(transform.id);
+        return;
+      }
+
+      // Check for expanded paste region
+      const expandedId = buffer.getExpandedPasteAtLine(logicalPos.row);
+      if (expandedId) {
+        buffer.togglePasteExpansion(expandedId);
+      }
+    },
+    { isActive: focus },
+  );
+
   useMouse(
     (event: MouseEvent) => {
       if (event.name === 'right-release') {

packages/cli/src/ui/components/shared/text-buffer.test.ts

@@ -57,6 +57,7 @@ const initialState: TextBufferState = {
   transformationsByLine: [[]],
   visualLayout: defaultVisualLayout,
   pastedContent: {},
+  expandedPasteInfo: new Map(),
 };
 
 /**
@@ -531,6 +532,148 @@ describe('textBufferReducer', () => {
       expect(state.cursorCol).toBe(5);
     });
   });
+
+  describe('toggle_paste_expansion action', () => {
+    const placeholder = '[Pasted Text: 6 lines]';
+    const content = 'line1\nline2\nline3\nline4\nline5\nline6';
+
+    it('should expand a placeholder correctly', () => {
+      const stateWithPlaceholder = createStateWithTransformations({
+        lines: ['prefix ' + placeholder + ' suffix'],
+        cursorRow: 0,
+        cursorCol: 0,
+        pastedContent: { [placeholder]: content },
+      });
+
+      const action: TextBufferAction = {
+        type: 'toggle_paste_expansion',
+        payload: { id: placeholder },
+      };
+
+      const state = textBufferReducer(stateWithPlaceholder, action);
+
+      expect(state.lines).toEqual([
+        'prefix line1',
+        'line2',
+        'line3',
+        'line4',
+        'line5',
+        'line6 suffix',
+      ]);
+      expect(state.expandedPasteInfo.has(placeholder)).toBe(true);
+      const info = state.expandedPasteInfo.get(placeholder);
+      expect(info).toEqual({
+        startLine: 0,
+        lineCount: 6,
+        prefix: 'prefix ',
+        suffix: ' suffix',
+      });
+      // Cursor should be at the end of expanded content (before suffix)
+      expect(state.cursorRow).toBe(5);
+      expect(state.cursorCol).toBe(5); // length of 'line6'
+    });
+
+    it('should collapse an expanded placeholder correctly', () => {
+      const expandedState = createStateWithTransformations({
+        lines: [
+          'prefix line1',
+          'line2',
+          'line3',
+          'line4',
+          'line5',
+          'line6 suffix',
+        ],
+        cursorRow: 5,
+        cursorCol: 5,
+        pastedContent: { [placeholder]: content },
+        expandedPasteInfo: new Map([
+          [
+            placeholder,
+            {
+              startLine: 0,
+              lineCount: 6,
+              prefix: 'prefix ',
+              suffix: ' suffix',
+            },
+          ],
+        ]),
+      });
+
+      const action: TextBufferAction = {
+        type: 'toggle_paste_expansion',
+        payload: { id: placeholder },
+      };
+
+      const state = textBufferReducer(expandedState, action);
+
+      expect(state.lines).toEqual(['prefix ' + placeholder + ' suffix']);
+      expect(state.expandedPasteInfo.has(placeholder)).toBe(false);
+      // Cursor should be at the end of the collapsed placeholder
+      expect(state.cursorRow).toBe(0);
+      expect(state.cursorCol).toBe(('prefix ' + placeholder).length);
+    });
+
+    it('should expand single-line content correctly', () => {
+      const singleLinePlaceholder = '[Pasted Text: 10 chars]';
+      const singleLineContent = 'some text';
+      const stateWithPlaceholder = createStateWithTransformations({
+        lines: [singleLinePlaceholder],
+        cursorRow: 0,
+        cursorCol: 0,
+        pastedContent: { [singleLinePlaceholder]: singleLineContent },
+      });
+
+      const state = textBufferReducer(stateWithPlaceholder, {
+        type: 'toggle_paste_expansion',
+        payload: { id: singleLinePlaceholder },
+      });
+
+      expect(state.lines).toEqual(['some text']);
+      expect(state.cursorRow).toBe(0);
+      expect(state.cursorCol).toBe(9);
+    });
+
+    it('should return current state if placeholder ID not found in pastedContent', () => {
+      const action: TextBufferAction = {
+        type: 'toggle_paste_expansion',
+        payload: { id: 'unknown' },
+      };
+      const state = textBufferReducer(initialState, action);
+      expect(state).toBe(initialState);
+    });
+
+    it('should clear expandedPasteInfo when lines change from other edits', () => {
+      // Start with an expanded paste
+      const expandedState = createStateWithTransformations({
+        lines: ['prefix line1', 'line2', 'line3 suffix'],
+        cursorRow: 0,
+        cursorCol: 0,
+        pastedContent: { [placeholder]: 'line1\nline2\nline3' },
+        expandedPasteInfo: new Map([
+          [
+            placeholder,
+            {
+              startLine: 0,
+              lineCount: 3,
+              prefix: 'prefix ',
+              suffix: ' suffix',
+            },
+          ],
+        ]),
+      });
+
+      expect(expandedState.expandedPasteInfo.size).toBe(1);
+
+      // Insert a newline - this changes lines and should clear expandedPasteInfo
+      const stateAfterInsert = textBufferReducer(expandedState, {
+        type: 'insert',
+        payload: '\n',
+      });
+
+      // Lines changed, so expandedPasteInfo should be cleared
+      expect(stateAfterInsert.expandedPasteInfo.size).toBe(0);
+    });
+  });
 });
 
 const getBufferState = (result: { current: TextBuffer }) => {