Why: Byte truncation split UTF-8, subagent results could return unbounded text, and a write could overwrite a file that changed after it was read.
Evidence: cutRunes keeps a two-character Chinese prefix; tool selection honors -name; checklist reminders go through the reminder bus.
Impact: Tool output limits count characters. A subagent result over 32000 characters is stored as an artifact and the parent sees the path. fs_write_file rejects an existing file that was not read in this run.
Refs: feature/context-engineering
Co-authored-by: Cursor <cursoragent@cursor.com>