Input text truncation when pasting multi-line content

Description

When pasting multi-line text into the Claude Code input field, the content gets silently truncated. There is no warning or indication that the input was cut off, which can lead to Claude receiving incomplete context and producing incorrect or incomplete responses.

Reproduction Steps

1. Copy the following 20-line test text:

LINE 01: The quick brown fox jumps over the lazy dog.
LINE 02: Pack my box with five dozen liquor jugs.
LINE 03: How vexingly quick daft zebras jump at dawn.
LINE 04: The five boxing wizards jump quickly today.
LINE 05: Sphinx of black quartz, judge my vow carefully.
LINE 06: Two driven jocks help fax my big quiz now.
LINE 07: The jay, pig, fox, zebra and my wolves quack.
LINE 08: Sympathizing would fix Quaker objectives greatly.
LINE 09: A wizard's job is to vex chumps quickly in fog.
LINE 10: Watch Jeopardy, Alex Trebek's fun TV quiz game.
LINE 11: By Jove, my quick study of lexicography won a prize.
LINE 12: Waxy and quivering, jocks fumble the pizza badly.
LINE 13: MARKER_ALPHA - This is the alpha checkpoint marker.
LINE 14: MARKER_BETA - This is the beta checkpoint marker.
LINE 15: MARKER_GAMMA - This is the gamma checkpoint marker.
LINE 16: MARKER_DELTA - This is the delta checkpoint marker.
LINE 17: MARKER_EPSILON - This is the epsilon checkpoint marker.
LINE 18: The lazy dog finally caught the quick brown fox.
LINE 19: All good things must come to an end eventually.
LINE 20: FINAL_LINE - END_OF_TEST_TEXT - TRANSMISSION_COMPLETE

1. Paste into Claude Code input
2. Submit
3. Ask Claude what the last line received was

Expected Behavior

All 20 lines should be received, ending with LINE 20.

Actual Behavior

Only lines 01-19 were received. LINE 20 was silently dropped.

Impact

This is a critical usability issue. Users frequently need to paste:

• Code snippets for review/debugging
• Error logs and stack traces
• Configuration files
• Requirements or specifications

Silent truncation means Claude works with incomplete information, leading to:

• Incorrect diagnoses of bugs
• Missing context in code reviews
• Incomplete implementations
• User frustration when Claude "misses" something that was (supposedly) provided

Environment

• OS: Windows 11
• Claude Code CLI 2.0.73