PR #6922 made /api/media revalidate on every use, so overwriting a file in
place (same filename) also rewrote every historical chat preview that
referenced it — the old/new comparison was lost.
At settle time, snapshot each local-file MEDIA: reference into a
content-addressed store (<STATE_DIR>/media_snapshots/<sha256>.snap) and stamp
the message with _media_snapshots {path: digest}. The frontend appends
&snap=<digest> to historical preview URLs; /api/media serves the frozen bytes
with immutable caching when the digest is valid, and falls back to the live
file otherwise (eviction/never-captured). The existing path allow/deny checks
still gate the request — snap only selects which bytes to serve, it never
widens access.
- api/media_snapshots.py: content-addressed store (sha256 key, dedup, 50MB
per-file / 2GB total caps with FIFO eviction), MEDIA ref resolver, capture
allow-list mirroring the /api/media roots + #3234 deny list
- streaming.py: annotate settled assistant messages (idempotent, best-effort)
- routes.py: snap= serving branch + download_name override + deny direct
store-path access
- models.py: _media_snapshots registered in display-metadata merge keys
- ui.js: _stampMediaSnapshots post-cache stamping (main transcript,
transparent ordered segments, worklog scene prose) + data-snap threading
through the five lazy preview loaders
25 new tests incl. node-executed frontend behavior tests; reverse-verified.
happy5318
4eb98889ba