fix(react): use explicit experimental flag for headless runtime instead of standardBrowser

Replace the `standardBrowser !== false` check with an explicit
`experimental.runtimeEnvironment === 'headless'` opt-in for the
`loadHeadlessClerk` path. This ensures only Expo native takes the
headless initialization path, while chrome-extension and all other
SDKs continue using `getEntryChunks` (matching main branch behavior).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: chriscanin

packages/expo/src/provider/ClerkProvider.tsx

@@ -282,6 +282,7 @@ export function ClerkProvider<TUi extends Ui = Ui>(props: ClerkProviderProps<TUi
         ...experimental,
         // force the rethrowOfflineNetworkErrors flag to true if the asyncStorage is provided
         rethrowOfflineNetworkErrors: !!__experimental_resourceCache || experimental?.rethrowOfflineNetworkErrors,
+        ...(isNative() && { runtimeEnvironment: 'headless' as const }),
       }}
     >
       {children}

packages/react/src/isomorphicClerk.ts

@@ -279,12 +279,17 @@ export class IsomorphicClerk implements IsomorphicLoadedClerk {
     this.#eventBus.emit(clerkEvents.Status, 'loading');
     this.#eventBus.prioritizedOn(clerkEvents.Status, status => (this.#status = status));
 
-    // Only load entry chunks in standard browser environments (not React Native/headless)
-    if (this.#publishableKey && this.options.standardBrowser !== false) {
-      void this.getEntryChunks();
-    } else if (this.#publishableKey && this.options.Clerk) {
-      // For React Native/headless: initialize with the provided Clerk instance
+    // TODO: Please check into refactoring the type logic here, the experimental type interface is using type Autocomplete<U extends T, T = string> = U | (T & Record<never, never>);
+    //       so we are casting options.experimental.runtimeEnvironment to avoid changing Autocomplete to use an intersection (&) instead of a union (|), as this could cause problems in other parts of the codebase if not also refactored.
+
+    if (
+      this.#publishableKey &&
+      (this.options.experimental as { runtimeEnvironment?: string } | undefined)?.runtimeEnvironment === 'headless' &&
+      this.options.Clerk
+    ) {
       void this.loadHeadlessClerk();
+    } else if (this.#publishableKey) {
+      void this.getEntryChunks();
     }
   }
 

packages/shared/src/types/clerk.ts

@@ -1254,6 +1254,11 @@ export type ClerkOptions = ClerkOptionsNavigation &
          */
         rethrowOfflineNetworkErrors: boolean;
         commerce: boolean;
+        /**
+         * When set to `'headless'`, Clerk will skip script/chunk loading and initialize
+         * directly with the provided Clerk instance. Used by React Native / Expo.
+         */
+        runtimeEnvironment: 'headless';
       },
       Record<string, any>
     >;