diff --git a/.github/scripts/__tests__/resolve-hermes-url.test.mjs b/.github/scripts/__tests__/resolve-hermes-url.test.mjs
new file mode 100644
index 00000000000..6b368d24779
--- /dev/null
+++ b/.github/scripts/__tests__/resolve-hermes-url.test.mjs
@@ -0,0 +1,56 @@
+import assert from 'node:assert/strict';
+import {readFileSync} from 'node:fs';
+import {createRequire, stripTypeScriptTypes} from 'node:module';
+import {test} from 'node:test';
+import {runInNewContext} from 'node:vm';
+
+const callerSource = readFileSync(new URL('../resolve-hermes.mts', import.meta.url), 'utf8');
+const helperSource = readFileSync(new URL(
+  '../../../packages/react-native/scripts/ios-prebuild/utils.js', import.meta.url,
+), 'utf8');
+// Execute the actual downloader without the CLI dispatch or the zx dependency.
+const downloaderSource = stripTypeScriptTypes(callerSource.slice(
+  callerSource.indexOf('async function downloadUpstreamHermesTarball('),
+  callerSource.indexOf('/**\n * Extracts an upstream Hermes tarball'),
+));
+
+for (const buildType of ['Debug', 'Release']) {
+  for (const metadataAvailable of [true, false]) {
+    test(`${buildType}: ${metadataAvailable ? 'resolves nightly metadata' : 'missing metadata keeps release fallback'}`, async () => {
+      const version = buildType === 'Debug' ? '123.4.5' : '987.6.5';
+      const flavor = buildType.toLowerCase();
+      const snapshotRoot = `https://central.sonatype.com/repository/maven-snapshots/com/facebook/hermes/hermes-ios/${version}-SNAPSHOT`;
+      const metadataUrl = `${snapshotRoot}/maven-metadata.xml`;
+      const releaseUrl = `https://repo1.maven.org/maven2/com/facebook/hermes/hermes-ios/${version}/hermes-ios-${version}-hermes-ios-${flavor}.tar.gz`;
+      const nightlyUrl = `${snapshotRoot}/hermes-ios-${version}-20260915.123456-7-hermes-ios-${flavor}.tar.gz`;
+      const requests = [];
+      const fetch = async url => {
+        requests.push(url);
+        if (url === metadataUrl && metadataAvailable) {
+          return {
+            ok: true,
+            text: async () => '<metadata><versioning><snapshot><timestamp>20260915.123456</timestamp><buildNumber>7</buildNumber></snapshot></versioning></metadata>',
+          };
+        }
+        return {ok: false, status: 404, statusText: 'Not Found'};
+      };
+      const module = {exports: {}};
+      runInNewContext(helperSource, {
+        module,
+        require: createRequire(import.meta.url),
+        fetch,
+      });
+      const download = runInNewContext(`${downloaderSource}\ndownloadUpstreamHermesTarball`, {
+        computeNightlyTarballURL: module.exports.computeNightlyTarballURL,
+        resolveHermesArtifactVersion: () => version,
+        fetch,
+        echo: () => {},
+      });
+
+      assert.equal(await download(buildType), null);
+      assert.deepEqual(requests, metadataAvailable
+        ? [metadataUrl, releaseUrl, nightlyUrl]
+        : [metadataUrl, releaseUrl]);
+    });
+  }
+}
diff --git a/jest.config.js b/jest.config.js
index 5bc7bfdc30a..273b27feb34 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -51,9 +51,6 @@ module.exports = {
   },
   // [macOS
   moduleNameMapper: {
-    // `resolver.js` strips `exports`; match this before the broad fork mapper.
-    '^react-native/setup-env$':
-      '<rootDir>/packages/react-native/src/setup-env.js',
     // These mappers allow out-of-tree platforms tests to resolve RN imports
     '^react-native/setup-env$':
       '<rootDir>/packages/react-native/src/setup-env.js',