diff --git a/src/layers/streetLevel/index.js b/src/layers/streetLevel/index.js
index 1f7b0f7f0..8d332c227 100644
--- a/src/layers/streetLevel/index.js
+++ b/src/layers/streetLevel/index.js
@@ -126,8 +126,17 @@ export function createStreetLevelLayer({
     });
   }
 
-  // One source at a time: the first provider that defaults on.
-  const startsOn = defs.find((def) => def.defaultOn !== false);
+  /** `def`, or the first keyless provider not refused when `def` has no key. */
+  function keylessInstead(def, refused = () => false) {
+    if (def.keyReady?.() !== false) return def;
+    return defs.find((d) => !d.requiresKeyId && !refused(d.id)) || def;
+  }
+
+  // One source at a time: the first provider that defaults on. Without its
+  // key, the first keyless source instead, so a fresh keyless install opens
+  // on coverage rather than KEY REQUIRED.
+  const preferred = defs.find((def) => def.defaultOn !== false);
+  const startsOn = preferred && keylessInstead(preferred);
   for (const def of defs) {
     const entry = {
       def,
@@ -585,7 +594,15 @@ export function createStreetLevelLayer({
         providerIds: state.providers.keys(),
         filter: state.filter,
       });
-      const lit = litByParams(decoded.providers);
+      // Links and stored state omit Mapillary when it is on (the codec
+      // default), so a keyless install would restore a source it cannot draw.
+      const asked = litByParams(decoded.providers);
+      const lit =
+        asked &&
+        keylessInstead(
+          state.providers.get(asked).def,
+          (id) => decoded.providers.get(id) === false,
+        ).id;
       const before = litIds();
       for (const [id, entry] of state.providers)
         if (id !== lit) switchProvider(entry, false);
diff --git a/src/layers/streetLevel/index.test.mjs b/src/layers/streetLevel/index.test.mjs
index 6c79a52ca..93fc96d23 100644
--- a/src/layers/streetLevel/index.test.mjs
+++ b/src/layers/streetLevel/index.test.mjs
@@ -1127,3 +1127,64 @@ test('the panel says why a lit Street View draws nothing off Google 3D', async (
   const view = presentStreetLevelPanel(layer.getUIState());
   assert.match(view.meta, /Google Street View needs the Google 3D map/);
 });
+
+test('without a Mapillary key the first keyless source is lit instead', async (t) => {
+  const kartaViewSource = {
+    getTile: async () => ({ lines: [] }),
+    nearestPhotos: async () => [],
+    getPhoto: async () => {
+      throw new Error('KartaView has no such photo');
+    },
+    getSequencePhotos: async () => ({ photos: [], hasMore: false }),
+    probeImage: async () => true,
+  };
+  const lit = (hasToken) => {
+    const layer = createStreetLevelLayer({
+      providers: [
+        createMapillaryProvider({
+          source: fakeMapillarySource({ hasToken: () => hasToken }),
+          photoViewer: fakePhotoViewer(),
+        }),
+        createKartaViewProvider({ source: kartaViewSource }),
+      ],
+    });
+    t.after(() => layer.destroy());
+    return layer
+      .getUIState()
+      .providers.filter((provider) => provider.on)
+      .map((provider) => provider.id);
+  };
+  assert.deepEqual(lit(false), ['kartaview']);
+  assert.deepEqual(lit(true), ['mapillary']);
+});
+
+test('restoring the default "Mapillary on" without its key keeps a keyless source', (t) => {
+  const layer = createStreetLevelLayer({
+    providers: [
+      createMapillaryProvider({
+        source: fakeMapillarySource({ hasToken: () => false }),
+        photoViewer: fakePhotoViewer(),
+      }),
+      createKartaViewProvider({
+        source: {
+          getTile: async () => ({ lines: [] }),
+          nearestPhotos: async () => [],
+          getPhoto: async () => null,
+          getSequencePhotos: async () => ({ photos: [], hasMore: false }),
+          probeImage: async () => true,
+        },
+      }),
+    ],
+  });
+  t.after(() => layer.destroy());
+  const litIds = () =>
+    layer
+      .getUIState()
+      .providers.filter((provider) => provider.on)
+      .map((provider) => provider.id);
+  layer.setParams({ mapillary: true, providerSwitches: '' });
+  assert.deepEqual(litIds(), ['kartaview']);
+  // A link that switches KartaView off keeps its word.
+  layer.setParams({ mapillary: true, providerSwitches: 'kartaview-0' });
+  assert.deepEqual(litIds(), ['mapillary']);
+});
diff --git a/src/layers/streetLevel/providers/mapillary/index.js b/src/layers/streetLevel/providers/mapillary/index.js
index 928922195..c2e9e7850 100644
--- a/src/layers/streetLevel/providers/mapillary/index.js
+++ b/src/layers/streetLevel/providers/mapillary/index.js
@@ -74,6 +74,9 @@ export function createMapillaryProvider({ source, photoViewer = null }) {
     name: MAPILLARY_NAME,
     label: MAPILLARY_LABEL,
     requiresKeyId: MAPILLARY_KEY_ID,
+    /** A browser token or a token-adding Graph proxy; else KEY REQUIRED. */
+    keyReady: () =>
+      source.hasToken?.() !== false || Boolean(source.graphEndpoint),
     pickPrefix: PICK_PREFIX.root,
     colors: COLORS,
     credit: Object.freeze({ html: MAPILLARY_CREDIT_HTML }),
diff --git a/src/layers/streetLevel/registry.js b/src/layers/streetLevel/registry.js
index 5e51929a6..4ba1763ab 100644
--- a/src/layers/streetLevel/registry.js
+++ b/src/layers/streetLevel/registry.js
@@ -20,6 +20,8 @@ export function filtersOf(provider) {
  * @property {boolean} [groundClick]   No coverage: a ground click at street zoom opens its nearest image.
  * @property {string} [requiresMapStack]   Usable only on this map stack.
  * @property {boolean} [defaultOn]     Default true; the first that defaults on is lit.
+ * @property {() => boolean} [keyReady] False when its key is missing now; the
+ *   first keyless provider is lit instead of a default that cannot draw.
  * @property {{kind: 'view-cone', color: string}} [marker]   Default: GEV's pin.
  * @property {Array<'pano'|'since'>} [filters]   Filters it honours (default both).
  * @property {{noun: string, action: string}} [coverageLabel]   How the panel counts its lines and says what a click does (default: sequences, "click a line for its photos").