[BUG] Ctrl+G notepad editor truncates multiline input on return to Claude Code

Description

When using Ctrl+G to open the external notepad editor for multiline input, Claude Code truncates the text when returning from the editor.

Reproduction

1. Press Ctrl+G to open notepad editor
2. Write/paste multiline text (e.g., 74+ lines of detailed instructions)
3. Save and close notepad
4. Return to Claude Code
5. Text is displayed as: This ph[...Truncated text #1 +74 lines...]ematical drift.

The beginning and end of the text are shown, but the middle 74 lines are truncated and marked as [...Truncated text #1 +74 lines...].

Environment

• Platform: Claude Code CLI (latest), Windows
• Version: v2.1.32
• Date: February 7, 2026

Expected Behavior

Full text from the notepad editor should be passed to Claude Code without truncation.

Actual Behavior

Text is truncated mid-content with a placeholder showing how many lines were cut.

Notes

This is different from:

• #19219 (Ctrl+G erasing text - closed)
• #13125 (paste truncation - different mechanism)

This is specifically about the Ctrl+G external editor workflow truncating on return.