Merge pull request #985 from bilawalsidhu/fix/street-level-provider-sharing

Preserve custom Street Level provider switches in shared state

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+- Custom Street Level provider switches survive share links and stored state
+  using URL-safe stable provider IDs and a shared boolean-switch codec; existing
+  Mapillary links keep their meaning. Explicit provider toggles reach durable
+  state without adopting unrelated live switch changes.
+
 - Directions and Recent Imagery accept replaceable acquisition sources, including
   route transport, imagery catalog, thumbnails, tile templates and attribution.
   Explicitly removing either source leaves its layer unavailable; standalone

docs/CURRENT-STATE.md

@@ -26,8 +26,17 @@ all imagery providers. Without that option, Mapillary is registered only when
 with a truthful no-provider state, preserving layer controls and share tokens.
 Malformed selected sources and provider definitions still fail validation.
 An explicit provider list bypasses the unused Mapillary source, including its
-validation. Layer share identities are preserved; custom provider switches require
-a corresponding serialization contract.
+validation. Layer share identities and the legacy Mapillary `m` option remain
+stable. Custom provider switches use the `r` option (`example-1*panoramax-0`),
+with URL-safe separators and a shared layer-neutral boolean-switch codec, sorted by provider ID rather
+than registration order, and round-trip through links and stored state. A receiver
+applies only switches for its registered providers; absent custom switches leave
+current defaults unchanged. Explicit provider toggles persist only their requested
+switch IDs through the state coordinator; unrelated live values remain transient.
+The custom switch field is bounded to 256 characters;
+provider registration rejects compositions that cannot fit rather than truncating
+identities. A malformed or duplicate entry invalidates the complete custom-switch
+field. Existing whole-link size limits still apply.
 
 ## God's Eye View in conversations — October 2, 2026
 

scripts/package-boundaries.json

@@ -552,6 +552,7 @@
       "src/contextModePolicy.js",
       "src/data/detectionPolicy.js",
       "src/data/installationFeedback.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateCoordinator.js",
       "src/data/layerStateTokenReservations.json",
@@ -800,6 +801,7 @@
       "src/data/cockpitContactDot.js",
       "src/data/contactMatch.js",
       "src/data/iconOrientation.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateTokenReservations.json",
       "src/data/modelVisualAnchor.js",
@@ -842,6 +844,7 @@
       "src/data/cockpitContactDot.js",
       "src/data/contactMatch.js",
       "src/data/iconOrientation.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateTokenReservations.json",
       "src/data/modelVisualAnchor.js",
@@ -879,6 +882,7 @@
       "src/data/cockpitContactDot.js",
       "src/data/contactMatch.js",
       "src/data/iconOrientation.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateCoordinator.js",
       "src/data/layerStateTokenReservations.json",
@@ -1204,6 +1208,7 @@
       "src/layers/streetLevel/groundCast.js",
       "src/layers/streetLevel/meshSampler.js",
       "src/layers/streetLevel/pickRouter.js",
+      "src/data/idSwitches.js",
       "src/layers/streetLevel/params.js",
       "src/layers/streetLevel/registry.js",
       "src/layers/streetLevel/filter.js",
@@ -1249,6 +1254,7 @@
     "exports": ["./layers/radio"],
     "modules": [
       "src/data/iconOrientation.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateTokenReservations.json",
       "src/data/radioCountry.js",
@@ -1537,6 +1543,7 @@
       "src/data/installationFeedback.js",
       "src/data/issPass.js",
       "src/data/labelArbiter.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateCoordinator.js",
       "src/data/layerStateTokenReservations.json",
@@ -2286,6 +2293,7 @@
       "src/data/issPass.js",
       "src/data/satellitePass.js",
       "src/data/labelArbiter.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateTokenReservations.json",
       "src/data/localGeojson.js",
@@ -2807,6 +2815,7 @@
     "exports": ["./ui/share-restoration"],
     "modules": [
       "src/data/installationFeedback.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateCoordinator.js",
       "src/data/layerStateTokenReservations.json",
@@ -3327,6 +3336,7 @@
       "src/tools/queries/brief.js",
       "src/tools/queries/maritime.js",
       "src/tools/queries/share.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateTokenReservations.json",
       "src/sources/gbfsStations.js",
@@ -3449,6 +3459,7 @@
     "exports": ["./view"],
     "modules": [
       "src/view/index.js",
+      "src/data/idSwitches.js",
       "src/data/layerState.js",
       "src/data/layerStateTokenReservations.json"
     ],

src/data/idSwitches.js

@@ -0,0 +1,63 @@
+const MAX_SWITCHES_LENGTH = 256;
+const ENTRY = /^([a-z][a-z0-9-]*)-([01])$/;
+
+/** Canonical, bounded boolean switches keyed by stable slugs. */
+export function normalizeIdSwitches(value, reservedIds = []) {
+  if (typeof value !== 'string' || value.length > MAX_SWITCHES_LENGTH)
+    return null;
+  if (!value) return '';
+  const entries = new Map();
+  for (const field of value.split('*')) {
+    const match = ENTRY.exec(field);
+    if (!match || reservedIds.includes(match[1]) || entries.has(match[1]))
+      return null;
+    entries.set(match[1], match[2] === '1');
+  }
+  return [...entries]
+    .sort(([a], [b]) => (a < b ? -1 : a > b ? 1 : 0))
+    .map(([id, on]) => `${id}-${on ? '1' : '0'}`)
+    .join('*');
+}
+
+/** Encode by stable IDs rather than registration order or generated tokens. */
+export function encodeIdSwitches(switches) {
+  const value = [...switches]
+    .map(([id, on]) => `${id}-${on === true ? '1' : '0'}`)
+    .join('*');
+  if (value.length > MAX_SWITCHES_LENGTH)
+    throw new RangeError(
+      `Switch IDs exceed the ${MAX_SWITCHES_LENGTH}-character share-link limit`,
+    );
+  const normalized = normalizeIdSwitches(value);
+  if (normalized === null) throw new TypeError('Invalid boolean switch IDs');
+  return normalized;
+}
+
+/** A Map keeps switch IDs separate from object prototype properties. */
+export function decodeIdSwitches(value) {
+  const normalized = normalizeIdSwitches(value);
+  return new Map(
+    normalized
+      ? normalized.split('*').map((entry) => {
+          const [, id, on] = ENTRY.exec(entry);
+          return [id, on === '1'];
+        })
+      : [],
+  );
+}
+
+/** Persist only explicitly requested switch IDs, not unrelated live changes. */
+export function patchRequestedIdSwitches(previous, applied, requested) {
+  const current = decodeIdSwitches(applied);
+  const next = new Map(
+    [...decodeIdSwitches(previous)].filter(([id]) => current.has(id)),
+  );
+  let changed = false;
+  for (const [id, on] of current) {
+    if (Object.hasOwn(requested, id) && typeof requested[id] === 'boolean') {
+      next.set(id, on);
+      changed = true;
+    }
+  }
+  return changed ? encodeIdSwitches(next) : undefined;
+}

src/data/layerState.js

@@ -1,3 +1,4 @@
+import { normalizeIdSwitches, patchRequestedIdSwitches } from './idSwitches.js';
 import reservationRows from './layerStateTokenReservations.json' with { type: 'json' };
 
 const VALID_DISPOSITIONS = new Set([
@@ -411,8 +412,17 @@ const OPTION_GROUPS = Object.freeze({
     booleanOption('viirs', 'v', false),
   ]),
   'street-level': Object.freeze([
-    // One switch per registered imagery provider (src/app/layers/streetLevel.js).
+    // Preserve the published Mapillary token; custom switches use stable IDs.
     booleanOption('mapillary', 'm', true),
+    Object.freeze({
+      key: 'providerSwitches',
+      patchRequested: patchRequestedIdSwitches,
+      token: 'r',
+      defaultValue: '',
+      normalize: (value) => normalizeIdSwitches(value, ['mapillary']),
+      encode: normalizeIdSwitches,
+      decode: (value) => normalizeIdSwitches(value, ['mapillary']),
+    }),
     enumOption('pano', 'p', 'all', ['all', 'pano', 'flat'], {
       all: 'a',
       pano: 'p',

src/data/layerState.test.mjs

@@ -1,3 +1,4 @@
+import { encodeParams, decodeParams } from '../layers/streetLevel/params.js';
 import { readShellSource } from '../testSupport/readShellSource.mjs';
 import { expandApplicationHtml } from '../../build/application-html.js';
 import { readLayerSource } from '../testSupport/readLayerSource.mjs';
@@ -243,7 +244,11 @@ test('production registry is exact, canonical, and rejects incomplete contracts'
   }
   assert.equal(nextLayerStateToken(), '3');
   assert.equal(
-    nextLayerStateToken({ ...LAYER_STATE_TOKEN_RESERVATIONS, alpha: '3', bravo: '4' }),
+    nextLayerStateToken({
+      ...LAYER_STATE_TOKEN_RESERVATIONS,
+      alpha: '3',
+      bravo: '4',
+    }),
     '5',
   );
   const digitsExhausted = {
@@ -276,7 +281,9 @@ test('production registry is exact, canonical, and rejects incomplete contracts'
           [
             ...'0123456789',
             ...[...LAYER_STATE_TOKEN_ALPHABET].flatMap((first) =>
-              [...LAYER_STATE_TOKEN_ALPHABET].map((second) => `${first}${second}`),
+              [...LAYER_STATE_TOKEN_ALPHABET].map(
+                (second) => `${first}${second}`,
+              ),
             ),
           ].map((token, index) => [`occupied-${index}`, token]),
         ),
@@ -298,33 +305,37 @@ test('production registry is exact, canonical, and rejects incomplete contracts'
     true,
   );
   assert.equal(
-    validateLayerStateAllocations(
-      LAYER_STATE_TOKEN_RESERVATIONS,
-      { ...LAYER_STATE_TOKEN_RESERVATIONS, future: '3', next: '4' },
-    ),
+    validateLayerStateAllocations(LAYER_STATE_TOKEN_RESERVATIONS, {
+      ...LAYER_STATE_TOKEN_RESERVATIONS,
+      future: '3',
+      next: '4',
+    }),
     true,
   );
   assert.throws(
-    () => validateLayerStateAllocations(LAYER_STATE_TOKEN_RESERVATIONS, {
-      ...LAYER_STATE_TOKEN_RESERVATIONS,
-      future: '00',
-    }),
+    () =>
+      validateLayerStateAllocations(LAYER_STATE_TOKEN_RESERVATIONS, {
+        ...LAYER_STATE_TOKEN_RESERVATIONS,
+        future: '00',
+      }),
     /next free token 3/,
   );
   const beforeLastDigit = { ...digitsExhausted };
   delete beforeLastDigit['prior-9'];
   assert.equal(
-    validateLayerStateAllocations(
-      beforeLastDigit,
-      { ...beforeLastDigit, futurePair: '00', futureDigit: '9' },
-    ),
+    validateLayerStateAllocations(beforeLastDigit, {
+      ...beforeLastDigit,
+      futurePair: '00',
+      futureDigit: '9',
+    }),
     true,
   );
   assert.equal(
-    validateLayerStateAllocations(
-      digitsExhausted,
-      { ...digitsExhausted, pairB: '01', pairA: '00' },
-    ),
+    validateLayerStateAllocations(digitsExhausted, {
+      ...digitsExhausted,
+      pairB: '01',
+      pairA: '00',
+    }),
     true,
   );
   assert.throws(
@@ -2660,12 +2671,14 @@ test('Street Level: every option round-trips through a share link and stored sta
   state.enabledLayerIds = ['street-level'];
   state.options['street-level'] = {
     mapillary: false,
+    providerSwitches: '',
     pano: 'flat',
     sinceDays: MAX_SINCE_DAYS,
   };
   const decoded = decodeLayerStateParams(new URLSearchParams(encode(state)));
   assert.deepEqual(decoded.options['street-level'], {
     mapillary: false,
+    providerSwitches: '',
     pano: 'flat',
     sinceDays: MAX_SINCE_DAYS,
   });
@@ -2693,6 +2706,7 @@ test('Street Level: the link codec accepts exactly the windows the filter keeps'
 test('Street Level: a link without the provider switch keeps Mapillary on', () => {
   assert.deepEqual(streetLevelOptions(''), {
     mapillary: true,
+    providerSwitches: '',
     pano: 'all',
     sinceDays: 0,
   });
@@ -2703,3 +2717,73 @@ test('Street Level: a link without the provider switch keeps Mapillary on', () =
     true,
   );
 });
+
+test('explicit provider switches reach durable state without adopting unrelated live switches', () => {
+  const manager = new DataLayerManager({});
+  const providers = new Map([
+    ['mapillary', true],
+    ['alpha', true],
+    ['beta', true],
+  ]);
+  const filter = { pano: 'all', sinceDays: 0 };
+  for (const id of REGISTERED_LAYER_IDS) {
+    manager.register(
+      id === 'street-level'
+        ? {
+            ...fakeLayer(id),
+            getParams: () => encodeParams({ providers, filter }),
+            setParams(params) {
+              const decoded = decodeParams(params, {
+                providerIds: providers.keys(),
+                filter,
+              });
+              for (const [id, on] of decoded.providers) providers.set(id, on);
+              return true;
+            },
+          }
+        : fakeLayer(id),
+    );
+  }
+  manager.finalizeRegistrations(LAYER_STATE_REGISTRY);
+  const storage = memoryStorage();
+  const coordinator = new LayerStateCoordinator(manager, shareSink(), {
+    storage,
+  });
+  try {
+    providers.set('beta', false); // Passive state does not belong to the next action.
+    assert.equal(
+      manager.setLayerParams(
+        'street-level',
+        { alpha: false },
+        { origin: 'user' },
+      ),
+      true,
+    );
+    let saved = parseStoredLayerState(storage.getItem(LAYER_STATE_STORAGE_KEY));
+    assert.equal(saved.options['street-level'].providerSwitches, 'alpha-0');
+    const shared = decodeLayerStateParams(new URLSearchParams(encode(saved)));
+    const restored = decodeParams(shared.options['street-level'], {
+      providerIds: ['beta', 'alpha'],
+      filter,
+    });
+    assert.deepEqual([...restored.providers], [['alpha', false]]);
+    manager.setLayerParams('street-level', { beta: true }, { origin: 'user' });
+    saved = parseStoredLayerState(storage.getItem(LAYER_STATE_STORAGE_KEY));
+    assert.equal(
+      saved.options['street-level'].providerSwitches,
+      'alpha-0*beta-1',
+    );
+    manager.setLayerParams(
+      'street-level',
+      { alpha: true },
+      { origin: 'local-restore' },
+    );
+    saved = parseStoredLayerState(storage.getItem(LAYER_STATE_STORAGE_KEY));
+    assert.equal(
+      saved.options['street-level'].providerSwitches,
+      'alpha-0*beta-1',
+    );
+  } finally {
+    coordinator.destroy();
+  }
+});

src/data/layerStateCoordinator.js

@@ -255,8 +255,22 @@ export class LayerStateCoordinator {
       const explicitlyRequested = Object.hasOwn(requestedParams, spec.key);
       const implicitTrackingSync =
         !explicitlyRequested && spec.key === trackingOptionKey;
-      if (!explicitlyRequested && !implicitTrackingSync) continue;
-      const value = spec.normalize(change.params[spec.key]);
+      // Packed options can persist only the subkeys owned by this request.
+      const requestedValue =
+        explicitlyRequested || implicitTrackingSync
+          ? change.params[spec.key]
+          : spec.patchRequested?.(
+              nextOwnerOptions[spec.key],
+              change.params[spec.key],
+              requestedParams,
+            );
+      if (
+        !explicitlyRequested &&
+        !implicitTrackingSync &&
+        requestedValue === undefined
+      )
+        continue;
+      const value = spec.normalize(requestedValue);
       if (value === null) {
         if (implicitTrackingSync) {
           nextOwnerOptions[spec.key] = null;

src/data/layerStateTokenLedger.test.mjs

@@ -98,6 +98,12 @@ function withPublishedBase(
 }
 
 function writeCodecFixture(cwd, rows, entries) {
+  const providerCodec = path.join(cwd, 'src/data/idSwitches.js');
+  mkdirSync(path.dirname(providerCodec), { recursive: true });
+  writeFileSync(
+    providerCodec,
+    readFileSync(new URL('./idSwitches.js', import.meta.url)),
+  );
   const source = readFileSync(CODEC_SOURCE_PATH, 'utf8');
   const registryEnd = ']);\n\nexport const REGISTERED_LAYER_IDS';
   assert.equal(source.split(registryEnd).length, 2);

src/layers/streetLevel/params.js

@@ -1,13 +1,19 @@
 import { normalizeFilter } from './filter.js';
+import { encodeIdSwitches, decodeIdSwitches } from '../../data/idSwitches.js';
 
 /**
- * Share-link params: one boolean per provider plus the filter. The codec in
- * src/data/layerState.js names the same keys, so a new provider needs one there.
+ * Provider params plus the filter. Custom switches share a stable ID-based
+ * field; Mapillary retains its existing boolean and share token.
  * @param {{providers: Iterable<[string, boolean]>, filter: {pano: string, sinceDays: number}}} input
  */
 export function encodeParams({ providers, filter }) {
   const params = {};
-  for (const [id, on] of providers) params[id] = on === true;
+  const entries = [...providers];
+  for (const [id, on] of entries) params[id] = on === true;
+  const switches = encodeIdSwitches(
+    entries.filter(([id]) => id !== 'mapillary'),
+  );
+  if (switches) params.providerSwitches = switches;
   params.pano = filter.pano;
   params.sinceDays = filter.sinceDays;
   return params;
@@ -23,8 +29,13 @@ export function encodeParams({ providers, filter }) {
 export function decodeParams(params, { providerIds, filter }) {
   const providers = new Map();
   const source = params && typeof params === 'object' ? params : {};
-  for (const id of providerIds)
-    if (typeof source[id] === 'boolean') providers.set(id, source[id]);
+  const switches = decodeIdSwitches(source.providerSwitches);
+  switches.delete('mapillary');
+  for (const id of providerIds) {
+    if (switches.has(id)) providers.set(id, switches.get(id));
+    else if (Object.hasOwn(source, id) && typeof source[id] === 'boolean')
+      providers.set(id, source[id]);
+  }
   const next = {};
   if ('pano' in source) next.pano = source.pano;
   if ('sinceDays' in source) next.sinceDays = source.sinceDays;

src/layers/streetLevel/params.test.mjs

@@ -11,7 +11,13 @@ test('encodeParams writes one boolean per provider plus the filter', () => {
       ],
       filter: { pano: 'flat', sinceDays: 365 },
     }),
-    { mapillary: true, panoramax: false, pano: 'flat', sinceDays: 365 },
+    {
+      mapillary: true,
+      panoramax: false,
+      providerSwitches: 'panoramax-0',
+      pano: 'flat',
+      sinceDays: 365,
+    },
   );
 });
 

src/layers/streetLevel/providerSwitches.test.mjs

@@ -0,0 +1,153 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { encodeParams, decodeParams } from './params.js';
+import {
+  normalizeIdSwitches,
+  patchRequestedIdSwitches,
+  decodeIdSwitches,
+  encodeIdSwitches,
+} from '../../data/idSwitches.js';
+import {
+  createDefaultLayerState,
+  encodeLayerStateParams,
+  decodeLayerStateParams,
+  serializeStoredLayerState,
+  parseStoredLayerState,
+} from '../../data/layerState.js';
+import { validateProviders } from './registry.js';
+import { fakeStreetLevelProvider } from '../../testSupport/streetLevelFakes.mjs';
+
+const filter = { pano: 'flat', sinceDays: 365 };
+
+test('custom switches survive sharing and storage without depending on provider order', () => {
+  const providers = [
+    ['panoramax', false],
+    ['example', true],
+    ['mapillary', false],
+  ];
+  const options = encodeParams({ providers, filter });
+  assert.equal(options.providerSwitches, 'example-1*panoramax-0');
+  assert.equal(
+    encodeParams({ providers: [...providers].reverse(), filter })
+      .providerSwitches,
+    options.providerSwitches,
+  );
+  const state = createDefaultLayerState();
+  state.enabledLayerIds = ['street-level'];
+  state.options['street-level'] = options;
+  const params = new URLSearchParams({ v: '2' });
+  encodeLayerStateParams(params, state);
+  assert.match(params.get('lo'), /0\.m\.0/);
+  assert.match(params.get('lo'), /0\.r\.example-1\*panoramax-0/);
+  assert.ok(
+    params.toString().includes('0.r.example-1*panoramax-0'),
+    'custom switches need no percent escaping',
+  );
+  for (const restored of [
+    decodeLayerStateParams(params),
+    parseStoredLayerState(serializeStoredLayerState(state)),
+  ]) {
+    const decoded = decodeParams(restored.options['street-level'], {
+      providerIds: ['example', 'mapillary', 'panoramax'],
+      filter: { pano: 'all', sinceDays: 0 },
+    });
+    assert.deepEqual(
+      [...decoded.providers],
+      [
+        ['example', true],
+        ['mapillary', false],
+        ['panoramax', false],
+      ],
+    );
+    assert.deepEqual(decoded.filter, filter);
+    assert.deepEqual(
+      [
+        ...decodeParams(restored.options['street-level'], {
+          providerIds: ['panoramax'],
+          filter,
+        }).providers,
+      ],
+      [['panoramax', false]],
+    );
+    assert.equal(
+      decodeParams(restored.options['street-level'], {
+        providerIds: [],
+        filter,
+      }).providers.size,
+      0,
+    );
+  }
+});
+
+test('legacy links retain Mapillary semantics and leave custom defaults alone', () => {
+  for (const [lo, on] of [
+    ['', true],
+    ['0.m.0', false],
+  ]) {
+    const state = decodeLayerStateParams(
+      new URLSearchParams({ v: '2', l: '0', lo }),
+    );
+    const restored = decodeParams(state.options['street-level'], {
+      providerIds: ['mapillary', 'example'],
+      filter,
+    });
+    assert.deepEqual([...restored.providers], [['mapillary', on]]);
+  }
+});
+
+test('switches reject ambiguous or oversized fields and cannot override the legacy token', () => {
+  for (const value of [
+    'example-0*example-1',
+    'mapillary-0',
+    '__proto__-1',
+    'a-2',
+    'a-1*',
+    'a.b-1',
+    'a_b-0',
+    `${'a'.repeat(255)}-1`,
+    null,
+    {},
+  ]) {
+    assert.equal(normalizeIdSwitches(value, ['mapillary']), null);
+  }
+  assert.equal(normalizeIdSwitches('constructor-0'), 'constructor-0');
+  assert.throws(
+    () => encodeIdSwitches([['a'.repeat(255), true]]),
+    /share-link/,
+  );
+  assert.throws(
+    () => validateProviders([fakeStreetLevelProvider({ id: 'a'.repeat(255) })]),
+    /share-link/,
+  );
+  const decoded = decodeParams(
+    { providerSwitches: 'mapillary-0', mapillary: true },
+    { providerIds: ['mapillary'], filter },
+  );
+  assert.equal(decoded.providers.get('mapillary'), true);
+});
+
+test('neutral switch codec preserves hyphens and numeric suffixes in IDs', () => {
+  const switches = [
+    ['provider-0', false],
+    ['provider-1', true],
+    ['a-b-c', true],
+  ];
+  const encoded = encodeIdSwitches(switches);
+  assert.equal(encoded, 'a-b-c-1*provider-0-0*provider-1-1');
+  const decoded = decodeIdSwitches(encoded);
+  for (const [id, on] of switches) assert.equal(decoded.get(id), on);
+  assert.equal(decodeIdSwitches('valid-1*broken').size, 0);
+});
+
+test('editing a receiving composition drops unknown IDs before enforcing the share bound', () => {
+  const previous = `${'x'.repeat(254)}-1`;
+  assert.equal(normalizeIdSwitches(previous), previous);
+  assert.equal(
+    patchRequestedIdSwitches(previous, 'alpha-0*beta-0', { alpha: false }),
+    'alpha-0',
+  );
+  assert.equal(
+    patchRequestedIdSwitches(previous, 'alpha-0', { pano: 'flat' }),
+    undefined,
+  );
+});

src/layers/streetLevel/registry.js

@@ -1,3 +1,5 @@
+import { encodeIdSwitches } from '../../data/idSwitches.js';
+
 /**
  * The contract an imagery provider registers with the Street Level layer.
  *
@@ -125,6 +127,19 @@ export function validateProviders(providers) {
     ids.add(provider.id);
     prefixes.push(provider.pickPrefix);
   }
+  // Validate the complete bounded share field once, before any instance exists.
+  try {
+    encodeIdSwitches(
+      providers
+        .filter(({ id }) => id !== 'mapillary')
+        .map(({ id }) => [id, true]),
+    );
+  } catch (error) {
+    if (!(error instanceof RangeError)) throw error;
+    throw new RangeError(
+      'Street Level provider IDs cannot fit in the 256-character share-link field; use shorter IDs or fewer providers',
+    );
+  }
   return Object.freeze([...providers]);
 }