The default basemap has been a vector style since 4.1.0, and maplibre-gl builds
its WebGL context inside the Map constructor. A browser that refuses one throws
from there, and VectorBasemap attaches the layer inside an async effect, so the
throw became an unhandled rejection no boundary could see.
What actually took the page down was the teardown. Leaflet registers a layer
before onAdd runs, so the half-built one stayed on the map, and the bridge's
onRemove calls this._glMap.remove() without asking whether there is one. That
TypeError lands in a React cleanup, which is why the error appears on the way
out of a map rather than on the way in, and why it reads as "Something went
wrong" when a tab changes and "TREK could not start" when the route does.
The browser is now asked first, once per page load, with a one-pixel probe that
hands the context straight back. Without WebGL the basemap is OSM raster tiles
instead of an empty map, and the maplibre chunk, about a megabyte, is never
fetched. The teardown path is safe either way: a half-built GL layer gets a
no-op stand-in so the bridge can finish its own cleanup, and detaching never
throws, because unmounting a map must not fail just because its basemap did.
Reproduced against demo.liketrek.com with WebGL switched off, and verified with
the fix: 14 raster tiles drawn, no GL canvas, no error screen.
Closes#2288
CARTO started stamping "API KEY REQUIRED" across every keyless basemap tile
on 26.08.2026. #2060 added a key field as the immediate answer, but it leaves
a self-hosted instance needing an email exchange with CARTO before its maps
look right, and every default in the client still pointed at CARTO. Default
to OpenFreeMap Positron instead: no key, no account, no request limit,
commercial use allowed, attribution required.
OpenFreeMap serves vector tiles only, so the Leaflet basemap is a MapLibre
style document rather than an XYZ template. maplibre-gl-leaflet hangs a GL
canvas into Leaflet's own tile pane, which leaves everything above it alone -
markers, GeoJSON, clusters, plugin layers, the custom panes, and the click
handling, since Leaflet's CSS already puts pointer-events:none on that layer.
maplibre-gl still arrives only through a dynamic import, so no chunk that
draws a map grows by a megabyte.
Switched: the trip planner, the MapView fallback every preview goes through,
the journey map, collections, the atlas, the shared trip page and the offline
tile prefetch. OpenFreeMap Positron and Bright join the tile presets in
settings, the admin defaults and both mobile screens.
A CARTO template that is already saved keeps working when a key backs it -
that stays a supported choice. Without a key it is not drawn at all:
resolveTileUrl falls back to the default rather than to a watermark, so an
instance that upgrades with one in its settings sees the new basemap
immediately and needs no migration. The stored value is left as it is, so the
Map settings tab still shows what was chosen and the warning underneath it
explains why - one sentence appended, in all 23 locales.
OpenFreeMap asks for a credit of its own; OpenStreetMap alone under its tiles
is wrong and a licence problem. attributionForTile() derives it from the URL
rather than from a flag at each call site, and the shared trip map, which
carried no attribution at all, now gets one.
Offline maps keep working and get cheaper. A vector style is four things
instead of one, so sync/glPrefetcher.ts walks the style document, its sprite,
the Latin glyph ranges of each font stack it uses, the TileJSON - the planet
path is versioned, so guessing it answers 200 with an empty body - and then
the .pbf tiles. Over the Berlin bounding box TREK computes, raster z10-16 is
2237 requests and 34.6 MB and gives up above z16; vector z10-14 is 177
requests and 32.1 MB and stays sharp above that, because MapLibre scales the
z14 tile rather than asking for another. The Workbox rule for
tiles.openfreemap.org moves to CacheFirst and shares the prefetcher's cache,
so browsing tops a downloaded region up instead of filling a second copy
beside it - a versioned tile path can never be stale. Clearing offline maps
clears it too.
The atlas loses its second raster layer. It existed to warm the HTTP cache of
neighbouring zoom levels, which a vector basemap does not need; a second one
would only cost a second WebGL context. OpenFreeMap has no label-free style,
so its labels are switched off on the live map instead - they are all symbol
layers, while borders and coastlines are line and fill - re-armed on
style.load so a theme switch keeps them off.
Theme changes call setStyle in place rather than rebuilding the layer: a swap
per toggle would leak a WebGL context, and browsers cap those in the low
teens.
Maurice