File Size Limits for At-Mentions

What: Enforces a 256KB size limit when files are attached via at-mention (@ symbol).

How it works:

# If you try to attach a large file via at-mention:
@/path/to/large-file.log

# Claude Code will now check the file size first and reject if > 256KB

Details:

• Prevents accidental attachment of large log files, binaries, or data files that would waste tokens
• Size check happens before file content is read, saving processing time
• Logs telemetry event tengu_attachment_file_too_large with file size for monitoring
• Regular Read tool usage (without at-mention) is unaffected and can still handle large files with offset/limit parameters
• Evidence: npA() at line 481542, ob1() at line 313340 (size check at lines 313344-313349)