The shell's VersionsSource (shell/node-versions-source.ts) reads GET
/api/history through the sync and shows one version per distinct content
(a restore's copy folds into the entry it copies; the blank page is none),
numbered as they first appeared, with what changed since the one before.
The entry the server says is on the canvas marks the version; undo and
redo of the newest version restore the one before it, or it again, through
POST /api/restore, so hand edits stay as versions of their own. The cards
sit in a panel beside the canvas (toggle in the header); the strip and
Compare come from the shared canvas components. The sync tells listeners
once per server version, and when History changed without one, so the
list is read again only then.
A write taken in place that leaves the canvas as it is gets no autosave from draw.io, so the marker for its copy stayed armed and ate the user's next paper-size edit: arm it only when the write changed the document. The 15 s export timeout now retires the export's sequence number, so a result POST that answers late no longer restores the document a second time.
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.
shell/mcp-sync-core.ts ports preview.js's protocol without the page or
React: polling GET /api/state every 2 s with the state id and version,
pushes of the user's edits with their base version and state, 409 and 413
handling, recovery of a recreated session (the tab's copy goes to History),
the token refresh after a 403, sync and export requests (PNG by page id,
SVG of another page through a transient one-page projection with autosave
ignored, the 600 ms wait for icons), thumbnails for History, and History
reads and restores that name the state the list belongs to.
A server write goes on the canvas as one undo step (loadDiagram commit,
with the change marked) when decideLoad finds it changes only the page on
screen, keeps the file variables and needs no load-only setting; the other
pages are compared with the MCP core's contentFingerprint. draw.io's own
re-serialized copy of such a write is recognized with isSameDocument and
not pushed back as an edit.
shell/use-mcp-sync.ts mounts the sync once inside DiagramProvider, reads
draw.io's autosave and load messages, and reports the connection state,
which the shell's status bar shows; notices come as toasts from the
dictionaries.
dayuan.jiang