The sync script previously overwrote ~/.codex/AGENTS.md on every run,
destroying any user-authored content. This adds marker-based merging
(<!-- BEGIN ECC --> / <!-- END ECC -->) so only the ECC-managed section
is replaced on subsequent runs, preserving user content outside the
markers.
Merge logic:
- No file → create with markers
- Both markers present (ordered, CRLF-safe) → replace only the ECC section
- BEGIN without END (corrupted) → full replace (backup saved)
- No markers at all → append ECC block (preserves existing content)
Also fixes:
- Symlink preservation: uses cat > instead of mv to write through symlinks
- CRLF handling: strips \r in marker detection to handle Windows-edited files
- Marker ordering: validates BEGIN appears before END, not just that both exist
The legacy heading-match heuristic was intentionally removed per council
review: any unmarked file is either user-authored (append is safe) or
legacy ECC-generated (duplicates once, deduplicates on next run via
markers). A timestamped backup is always saved before any mutation.
Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Happy <yesreply@happy.engineering>
