The updater located its managed block by substring (`marker in content`
and `next(... if marker in line)`), so a heading that merely appeared as
a substring of another line, or a duplicate heading, matched the wrong
offset and the rewrite could truncate or drop unrelated content in
CLAUDE.md / AGENTS.md.
It now matches the section heading exactly (`line.strip() == marker`),
appends when the section is absent, and prefers the last exact match
when several exist. Thanks @bdfinst for the report.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
safishamsi