diff --git a/packages/host/app/lib/externals.ts b/packages/host/app/lib/externals.ts
index ffd74cf6ddc..c9e13737ead 100644
--- a/packages/host/app/lib/externals.ts
+++ b/packages/host/app/lib/externals.ts
@@ -188,60 +188,26 @@ export function shimExternals(virtualNetwork: VirtualNetwork) {
   shimHostCommands(virtualNetwork);
 }
 
-// Shims test-only module IDs into the virtual network as throwing stubs so
-// realm cards that colocate test imports can load in any environment without
-// executing test code. live-test.js overrides these at the loader level with
-// the real implementations when a test runner is present.
+// Shims test-only module IDs into the virtual network as empty fallbacks so
+// realm cards that co-locate test imports (e.g. *.test.gts) can load in any
+// environment without crashing. These are never actually called in production
+// — they just prevent import resolution errors.
+//
+// In live-test runs, live-test.js overrides these at the *realm loader* level
+// (via loader.shimModule) with the real implementations before importing test
+// modules. The loader-level shim takes precedence over this network-level
+// fallback, so the real helpers are used during test execution.
 export function shimModulesForLiveTests(virtualNetwork: VirtualNetwork) {
-  const windowQUnit = (globalThis as any).QUnit;
-
-  const testOnlyStub = (moduleId: string) =>
-    new Proxy(
-      {},
-      {
-        get: () => {
-          throw new Error(
-            `${moduleId} is only available in a test environment.`,
-          );
-        },
-      },
-    );
-
-  // Use real @ember/test-helpers only when QUnit is running; stub otherwise.
-  virtualNetwork.shimModule(
-    '@ember/test-helpers',
-    windowQUnit ? emberTestHelpers : testOnlyStub('@ember/test-helpers'),
-  );
-
-  // Always stub host test helpers here — live-test.js shimModule() on the
-  // realm loader overrides these with real implementations at test time.
-  virtualNetwork.shimModule(
-    '@cardstack/host/tests/helpers',
-    testOnlyStub('@cardstack/host/tests/helpers'),
-  );
-  virtualNetwork.shimModule(
-    '@cardstack/host/tests/helpers/mock-matrix',
-    testOnlyStub('@cardstack/host/tests/helpers/mock-matrix'),
-  );
-  virtualNetwork.shimModule(
-    '@cardstack/host/tests/helpers/setup',
-    testOnlyStub('@cardstack/host/tests/helpers/setup'),
-  );
-  virtualNetwork.shimModule(
-    '@cardstack/host/tests/helpers/adapter',
-    testOnlyStub('@cardstack/host/tests/helpers/adapter'),
-  );
+  virtualNetwork.shimModule('@ember/test-helpers', emberTestHelpers);
+  virtualNetwork.shimModule('@cardstack/host/tests/helpers', {});
+  virtualNetwork.shimModule('@cardstack/host/tests/helpers/mock-matrix', {});
+  virtualNetwork.shimModule('@cardstack/host/tests/helpers/setup', {});
+  virtualNetwork.shimModule('@cardstack/host/tests/helpers/adapter', {});
   virtualNetwork.shimModule(
     '@cardstack/host/tests/helpers/render-component',
-    testOnlyStub('@cardstack/host/tests/helpers/render-component'),
-  );
-  virtualNetwork.shimModule(
-    '@cardstack/host/tests/helpers/base-realm',
-    testOnlyStub('@cardstack/host/tests/helpers/base-realm'),
-  );
-  virtualNetwork.shimModule(
-    '@universal-ember/test-support',
-    testOnlyStub('@universal-ember/test-support'),
+    {},
   );
-  virtualNetwork.shimModule('@ember/owner', testOnlyStub('@ember/owner'));
+  virtualNetwork.shimModule('@cardstack/host/tests/helpers/base-realm', {});
+  virtualNetwork.shimModule('@universal-ember/test-support', {});
+  virtualNetwork.shimModule('@ember/owner', {});
 }
diff --git a/packages/host/docs/live-tests.md b/packages/host/docs/live-tests.md
new file mode 100644
index 00000000000..6fe8e796fc2
--- /dev/null
+++ b/packages/host/docs/live-tests.md
@@ -0,0 +1,26 @@
+# Live Tests (Card-Based)
+
+Live tests run directly against a realm server. Test modules are `*.test.gts` files inside a realm that export a `runTests()` function — files must follow this naming pattern to be auto-discovered via the realm's `_mtimes` endpoint.
+
+## Run in Browser
+
+Requires servers to already be running.
+
+- Experiments realm: `http://localhost:4200/tests/index.html?liveTest=true&realmURL=http://localhost:4201/experiments/&hidepassed`
+- Catalog realm: `http://localhost:4200/tests/index.html?liveTest=true&realmURL=http://localhost:4201/catalog/&hidepassed`
+
+## Run as a Script
+
+Requires realm servers to be running (experiments + catalog). If you already have `pnpm start:all` running, that is sufficient.
+
+```sh
+# Terminal 1 — start realm servers if not already running
+mise run test-services:host
+
+# Terminal 2 — run the default live test suite (catalog realm)
+cd packages/host
+pnpm test:live
+
+# Or target a specific realm via the REALM_URL env var (trailing slash optional)
+REALM_URL=http://localhost:4201/experiments/ pnpm test:live
+```
diff --git a/packages/host/scripts/live-test-wait-for-servers.sh b/packages/host/scripts/live-test-wait-for-servers.sh
index fc4587ce41c..f2b5bf5664c 100755
--- a/packages/host/scripts/live-test-wait-for-servers.sh
+++ b/packages/host/scripts/live-test-wait-for-servers.sh
@@ -2,13 +2,27 @@
 
 READY_PATH="_readiness-check?acceptHeader=application%2Fvnd.api%2Bjson"
 BASE_REALM_READY="http-get://localhost:4201/base/${READY_PATH}"
-CATALOG_REALM_READY="http-get://localhost:4201/catalog/${READY_PATH}"
 SYNAPSE_URL="http://localhost:8008"
 SMTP_4_DEV_URL="http://localhost:5001"
 
-READY_URLS="$BASE_REALM_READY|$CATALOG_REALM_READY|$SYNAPSE_URL|$SMTP_4_DEV_URL"
+if [ -n "$REALM_URL" ]; then
+  REALM_HOST="$REALM_URL"
+  case "$REALM_HOST" in
+    http://*) REALM_HOST="${REALM_HOST#http://}" ;;
+    https://*) REALM_HOST="${REALM_HOST#https://}" ;;
+  esac
+  case "$REALM_HOST" in
+    */) ;;
+    *) REALM_HOST="${REALM_HOST}/" ;;
+  esac
+  REALM_READY="http-get://${REALM_HOST}${READY_PATH}"
+  READY_URLS="$BASE_REALM_READY|$REALM_READY|$SYNAPSE_URL|$SMTP_4_DEV_URL"
+else
+  CATALOG_REALM_READY="http-get://localhost:4201/catalog/${READY_PATH}"
+  READY_URLS="$BASE_REALM_READY|$CATALOG_REALM_READY|$SYNAPSE_URL|$SMTP_4_DEV_URL"
+fi
 
-WAIT_ON_TIMEOUT=600000 NODE_NO_WARNINGS=1 start-server-and-test \
+WAIT_ON_TIMEOUT=600000 NODE_NO_WARNINGS=1 REALM_URL="${REALM_URL:-}" start-server-and-test \
   'pnpm run wait' \
   "$READY_URLS" \
   'ember test --config-file testem-live.js --path ./dist'
diff --git a/packages/host/testem-live.js b/packages/host/testem-live.js
index 696942ad6e3..4306fbd48f0 100644
--- a/packages/host/testem-live.js
+++ b/packages/host/testem-live.js
@@ -6,9 +6,17 @@ const XunitReporter = require('testem/lib/reporters/xunit_reporter');
 const fs = require('fs');
 const path = require('path');
 
+const DEFAULT_REALM_URLS = ['http://localhost:4201/catalog/'];
+
+const realmURLs = process.env.REALM_URL
+  ? [process.env.REALM_URL]
+  : DEFAULT_REALM_URLS;
+
 const config = {
-  test_page:
-    'tests/index.html?liveTest=true&realmURL=http://localhost:4201/catalog/&hidepassed',
+  test_page: realmURLs.map(
+    (url) =>
+      `tests/index.html?liveTest=true&realmURL=${encodeURIComponent(url)}&hidepassed`,
+  ),
   disable_watching: true,
   browser_timeout: 120,
   browser_no_activity_timeout: 120,
diff --git a/packages/host/tests/live-test.js b/packages/host/tests/live-test.js
index 5e13a1f8b52..fcd54bc16a2 100644
--- a/packages/host/tests/live-test.js
+++ b/packages/host/tests/live-test.js
@@ -1,7 +1,7 @@
 import * as QUnit from 'qunit';
 
 /**
- * Discovers all .gts/.ts module URLs in a realm using the _mtimes endpoint,
+ * Discovers all *.test.gts module URLs in a realm using the _mtimes endpoint,
  * which returns a flat map of every file URL in the realm in one request.
  * Only modules that export a `runTests` function will actually register tests.
  *
@@ -12,6 +12,11 @@ async function discoverTestModules(realmURL) {
   const resp = await fetch(`${realmURL}_mtimes`, {
     headers: { Accept: 'application/vnd.api+json' },
   });
+  if (!resp.ok) {
+    throw new Error(
+      `Cannot access realm ${realmURL} (HTTP ${resp.status}). Check that the realm is publicly readable.`,
+    );
+  }
   const {
     data: {
       attributes: { mtimes },
@@ -19,8 +24,8 @@ async function discoverTestModules(realmURL) {
   } = await resp.json();
 
   return Object.keys(mtimes)
-    .filter((url) => url.endsWith('.gts') || url.endsWith('.ts'))
-    .map((url) => url.replace(/\.(gts|ts)$/, ''));
+    .filter((url) => url.endsWith('.test.gts'))
+    .map((url) => url.slice(0, -'.gts'.length));
 }
 
 // eslint-disable-next-line ember/no-test-import-export