A picked engine now lives in the switch until it runs; only then is the
address written, so a pick superseded by Back or one that fails rewrites no
entry. An engine-changing history visit holds the outgoing share link, which
neither restores nor writes the visited entry, and the running engine takes
the address back once the switch settles, restoring any entry visited while
it was held or not yet listening. Handed-off layers keep running where the
incoming address agrees with the outgoing one and follow a visited entry
where it differs. A failed recovery keeps the error on the loading screen
with an engine picker for a retry, and a failing reveal of the new globe no
longer blocks the cover removal or later requests.
qa-all-layer-switches.mjs now checks once that Puppeteer can start Chrome and that the preview answers, and names PUPPETEER_EXECUTABLE_PATH and npx puppeteer browsers install chrome when it cannot. Each run writes <output>/acceptance.json with the commit, dirty files at both ends, Chrome, Node, base URL, times and, per scenario, status, exit code, duration, covered layer ids and the sha256 of its log. It replaces summary.json.
Live Sentinel-2 imagery is bright at this altitude, so a fixed crop of white two-pixel vehicles changed anywhere from 14 to 300 pixels. The scenario now serves a uniform dark ground tile, waits for the layer to settle with vehicles in view, projects each vehicle to the window and requires 90% of those above the drawn terrain to change the picture where the layer places them; in simulation nothing else may change. Vehicles below the terrain and the population left after the round trip are reported, not asserted.
The engine switch moves out of main.js into src/standalone/engineSwitch.js: every
engine change in the page hands the session off (layers, Director, Contacts,
directions and satellite cameras), whether it came from the picker or from
history. Each attempt has a generation; a failure rolls back to the last engine
that started, requests made during a switch or recovery are reconciled once it
settles, and a picked engine adds its history entry only after it starts. The
first-frame wait only lifts the cover and never fails a started engine; a
hidden tab does not wait. Nothing starts after pagehide, and a failed recovery
leaves the picker usable.
German Khokhlov