A recovery loads the server's diagram in full and waits for draw.io's
load report, as the classic page does: whether the canvas takes a write
in place is decided inside DiagramProvider, and an autosave of the
canvas being replaced went to the server as an edit when the decision
was wrong. A paper size change alone is pushed again: autosaves are
compared as documents only for draw.io's own copy of a committed write.
A projection stays on screen until draw.io reports the restore load
(5 s at most), the whole export ends in 15 s even when its result POST
hangs, and an export in flight is dropped when draw.io starts over. A
refused poll shows the tab offline. With several pages and the page on
screen unknown, a write loads in full. hasLoadOnlySettings and the
highlight of an AI change are shared with the editor bridge.
The recovery, thumbnail, size limit and History cases of
tests/unit/mcp-preview-recovery.test.ts, driven against mcp-sync-core.ts
with a stubbed server and canvas, plus the stale 409 recovery, an export
request answered once, a projection that ignores edits and restores the
document, the thumbnail of a write loaded before draw.io was ready, writes
taken in place as commits (draw.io's own copy is not pushed), and the
commit-or-load decision table of decideLoad.
dayuan.jiang