diff --git a/packages/host/app/services/realm.ts b/packages/host/app/services/realm.ts
index 16bbaea85f..c01e3dc7f0 100644
--- a/packages/host/app/services/realm.ts
+++ b/packages/host/app/services/realm.ts
@@ -1057,7 +1057,11 @@ export default class RealmService extends Service {
     for (const realm of this.realms.keys()) {
       let paths = this.realmPathsCache.get(realm);
       if (!paths) {
-        paths = new RealmPaths(new URL(realm));
+        // The VirtualNetwork lets inRealm() match prefix-form ids (the store
+        // keys mapped-realm instances in prefix form) against URL-keyed
+        // realms. The cached RealmPaths reads the live VN's mappings at call
+        // time, so entries don't go stale as mappings register.
+        paths = new RealmPaths(new URL(realm), this.network.virtualNetwork);
         this.realmPathsCache.set(realm, paths);
       }
       if (paths.inRealm(id)) {
diff --git a/packages/host/app/services/render-service.ts b/packages/host/app/services/render-service.ts
index b6b5975396..596d3fc97f 100644
--- a/packages/host/app/services/render-service.ts
+++ b/packages/host/app/services/render-service.ts
@@ -140,13 +140,19 @@ export class CardStoreWithErrors implements CardStore {
   }
 
   private normalizeKey(id: string): string {
-    return this.normalizeURL(id).replace(/\.json$/, '');
+    let key = id.replace(/\.json$/, '');
+    // Cache keys fold to the canonical spelling (prefix form where a realm
+    // mapping exists) so prefix-form and URL-form lookups share an entry,
+    // matching the host store's keying.
+    return isLocalId(key)
+      ? key
+      : this.#virtualNetwork.unresolveURL(this.#virtualNetwork.toURL(key).href);
   }
 
   private normalizeURL(id: string): string {
     let key = id.replace(/\.json$/, '');
-    // Local IDs pass through; remote IDs canonicalize to URL form via the
-    // VN so prefix-form and URL-form lookups share a cache key.
+    // Load targets resolve to the real URL — this is the fetch boundary, and
+    // the loaded document's id is stamped from it.
     return isLocalId(key) ? id : this.#virtualNetwork.toURL(id).href;
   }
 
diff --git a/packages/host/app/services/store.ts b/packages/host/app/services/store.ts
index ea1de30fd5..27b109fd94 100644
--- a/packages/host/app/services/store.ts
+++ b/packages/host/app/services/store.ts
@@ -1673,7 +1673,13 @@ export default class StoreService extends Service implements StoreInterface {
       );
     }
 
-    // if there are no more subscribers to this realm then unsubscribe from realm
+    // if there are no more subscribers to this realm then unsubscribe from
+    // realm. Note this uses a same-form startsWith, so a mapped realm whose
+    // instances are keyed in prefix form (e.g. the base realm) never matches
+    // and its subscription is left installed for the session — a benign,
+    // deliberate leak. Making the teardown form-aware races invalidation
+    // delivery, and removing it entirely regresses invalidation-heavy paths;
+    // see the realm-subscription-lifecycle follow-up.
     let realmHref = !isLocalId(id)
       ? [...this.subscriptions.keys()].find((realmURL) =>
           id.startsWith(realmURL),
@@ -2918,12 +2924,13 @@ export function asURL(
     return urlOrDoc.data.id;
   }
   let id = urlOrDoc.replace(/\.json$/, '');
-  // Locals stay as-is; remotes resolve through the VN to a normalized URL.
-  // Keying stays in URL form so it matches gc-card-store, which keys instances
-  // by their (URL-form) data.id. Flipping the store's canonical key to RRI is
-  // deferred — it needs gc-card-store keyed the same way and the URL
-  // normalization `toURL` provides here (see CS-11730).
-  return isLocalId(id) ? id : vn.toURL(id).href;
+  // Locals stay as-is; remotes fold to the canonical spelling — through the
+  // VN's URL parse first (normalizing slashes/encoding the way a served URL
+  // is spelled), then back to prefix form where a realm mapping exists. This
+  // matches the document branch above, which returns `data.id` verbatim and
+  // is canonical (prefix form for mapped realms) as served, so both branches
+  // key a mapped realm's instance identically.
+  return isLocalId(id) ? id : vn.unresolveURL(vn.toURL(id).href);
 }
 
 function isSystemCardDefaultId(
diff --git a/packages/host/tests/integration/store-test.gts b/packages/host/tests/integration/store-test.gts
index 9e5591b2a8..28de918a3e 100644
--- a/packages/host/tests/integration/store-test.gts
+++ b/packages/host/tests/integration/store-test.gts
@@ -343,6 +343,31 @@ module('Integration | Store', function (hooks) {
     assert.strictEqual(file, undefined, 'delete() removes the remote card');
   });
 
+  test('adding a prefix-form reference installs the realm subscription', async function (assert) {
+    getService('network').virtualNetwork.addRealmMapping(
+      '@test-prefix/',
+      testRealmURL,
+    );
+    let subscriptions = (storeService as any).subscriptions as Map<
+      string,
+      { unsubscribe: () => void }
+    >;
+    assert.false(
+      subscriptions.has(testRealmURL),
+      'realm is not subscribed before adding the reference',
+    );
+
+    storeService.addReference('@test-prefix/Person/hassan');
+
+    assert.true(
+      subscriptions.has(testRealmURL),
+      'a prefix-form reference subscribes to its realm under the URL-form key',
+    );
+
+    await storeService.flush();
+    storeService.dropReference('@test-prefix/Person/hassan');
+  });
+
   test('deleting a linked target rewrites a loaded consumer linksTo slot to a broken-link sentinel', async function (assert) {
     // Load the consumer and the target, then link them so the consumer holds
     // the target as a resolved (present) link — the state a user is looking at