Module on_disk 

On-disk identity of a file-backed buffer — the shared “did this file change underneath us” primitive.

SS.1 (2026-08-11): lowered here from lattice-host::autoread so lattice-multibuffer can reach it. A multibuffer’s sources are snapshots read at view-creation time, and its Document::save writes every dirty source back to disk — without a baseline to compare against, that silently overwrites whatever changed the file externally. See docs/dev/architecture/multibuffer-stale-sources.md.

Deliberately ONE mechanism, not two. autoread had already worked out the distinction that matters — content hash authoritative so a bare touch is not a change, (mtime, size) only as a cheap pre-gate — and a second copy would drift from it.

Structs

OnDiskFingerprint

The on-disk identity of a file-backed buffer at the moment the editor last synced with disk — a load, or its own :w.