LiorMazig · Sep 9, 2026 · Sep 10, 2026 · Sep 10, 2026 · Sep 10, 2026 · Sep 10, 2026
diff --git a/scripts/mintlify-post-processing/appended-articles.json b/scripts/mintlify-post-processing/appended-articles.json
@@ -1,4 +1,7 @@
 {
+  "interfaces/ExperimentsModule": [
+    "interfaces/ExperimentsSnapshot"
+  ],
   "interfaces/ConnectorsModule": [
     "type-aliases/ConnectorIntegrationType",
     "interfaces/ConnectorIntegrationTypeRegistry",

diff --git a/scripts/mintlify-post-processing/types-to-expose.json b/scripts/mintlify-post-processing/types-to-expose.json
@@ -22,6 +22,8 @@
   "EntityHandler",
   "EntityRecord",
   "EntityTypeRegistry",
+  "ExperimentsModule",
+  "ExperimentsSnapshot",
   "FunctionName",
   "FunctionNameRegistry",
   "FunctionsModule",

diff --git a/src/client.ts b/src/client.ts
@@ -23,6 +23,9 @@ import type {
   CreateClientOptions,
 } from "./client.types.js";
 import { createAnalyticsModule } from "./modules/analytics.js";
+import { createExperimentsModule } from "./modules/experiments.js";
+import { createExposureTracker } from "./modules/experiment-exposures.js";
+import { EXPERIMENTS_CONTEXT_HEADER, getBrowserExperimentsContext, readExperimentsContext } from "./modules/experiments-context.js";
 import {
   createActorsModule,
   resolveActorsHost,
@@ -90,6 +93,7 @@ export function createClient(config: CreateClientConfig): Base44Client {
 
   // Normalize appBaseUrl to always be a string (empty if not provided or invalid)
   const normalizedAppBaseUrl = typeof appBaseUrl === "string" ? appBaseUrl : "";
+  const experimentsContext = config.experiments ?? getBrowserExperimentsContext(appId);
 
   const socketConfig: RoomsSocketConfig = {
     serverUrl,
@@ -110,9 +114,14 @@ export function createClient(config: CreateClientConfig): Base44Client {
     return socket;
   };
 
+  const { [EXPERIMENTS_CONTEXT_HEADER]: inheritedExperimentsContext, ...requestHeaders } = optionalHeaders ?? {};
   const headers = {
-    ...optionalHeaders,
+    ...requestHeaders,
     "X-App-Id": String(appId),
+    ...(experimentsContext ? {
+      "Base44-Visitor-Id": experimentsContext.identity.visitorId,
+      "Base44-Experiment-Preview": JSON.stringify(experimentsContext.preview ?? {}),
+    } : {}),
   };
 
   const functionHeaders = functionsVersion
@@ -166,6 +175,20 @@ export function createClient(config: CreateClientConfig): Base44Client {
     headers,
   });
 
+  const exposureTracker = createExposureTracker({
+      axiosClient,
+      appId,
+      enabled: analytics?.enabled ?? true,
+      source: typeof window === "undefined" ? "backend" : "browser",
+      pageUrl: experimentsContext?.pageUrl,
+  });
+  const experiments = createExperimentsModule({
+    getAuth: () => userAuthModule,
+    trackExposure: exposureTracker.track,
+    flushExposures: exposureTracker.flush,
+    context: experimentsContext,
+  });
+
   const userAuthModule = createAuthModule(
     axiosClient,
     functionsAxiosClient,
@@ -174,6 +197,7 @@ export function createClient(config: CreateClientConfig): Base44Client {
       appBaseUrl: normalizedAppBaseUrl,
       serverUrl,
       token,
+      onAuthStateChange: experiments.onAuthStateChange,
     }
   );
 
@@ -187,6 +211,14 @@ export function createClient(config: CreateClientConfig): Base44Client {
       userAuthModule.setToken(accessToken);
     }
   }
+  if (experimentsContext) {
+    const { userId, status } = experimentsContext.identity;
+    // The document's cookie identity may differ from this client's localStorage token.
+    const needsClientIdentity = typeof window !== "undefined" && userAuthModule.hasToken() &&
+      experimentsContext.config.experiments.some((experiment) => experiment.assign_by === "user");
+    experiments.onAuthStateChange(status === "pending" || needsClientIdentity ? { status: "pending" } :
+      userId ? { status: "authenticated", userId } : { status: "anonymous" });
+  }
 
   const actorsModule = createActorsModule({
     appId,
@@ -228,6 +260,7 @@ export function createClient(config: CreateClientConfig): Base44Client {
     integrations: createIntegrationsModule(axiosClient, appId),
     connectors: createUserConnectorsModule(axiosClient, appId),
     auth: userAuthModule,
+    experiments: experiments.module,
     functions: createFunctionsModule(functionsAxiosClient, appId, {
       getAuthHeaders: () => {
         const headers: Record<string, string> = {};
@@ -257,10 +290,13 @@ export function createClient(config: CreateClientConfig): Base44Client {
       appId,
       userAuthModule,
       enabled: analytics?.enabled ?? true,
+      getVisitorId: experiments.visitorId,
+      experimentsContext,
     }),
     actors: actorsModule.module,
     cleanup: () => {
       userModules.analytics.cleanup();
+      experiments.cleanup();
       actorsModule.closeAll();
       if (socket) {
         socket.disconnect();
@@ -331,7 +367,10 @@ export function createClient(config: CreateClientConfig): Base44Client {
       appId: String(appId),
       serverUrl,
       functionsVersion,
-      platformHeaders: optionalHeaders,
+      platformHeaders: {
+        ...headers,
+        ...(inheritedExperimentsContext ? { [EXPERIMENTS_CONTEXT_HEADER]: inheritedExperimentsContext } : {}),
+      },
     }),
 
     /**
@@ -507,6 +546,9 @@ export function createClientFromRequest(request: Request): Base44Client {
 
   // Prepare additional headers to propagate
   const additionalHeaders: Record<string, string> = {};
+  const encodedExperiments = request.headers.get(EXPERIMENTS_CONTEXT_HEADER);
+  const experimentsContext = readExperimentsContext(encodedExperiments, appId);
+  if (experimentsContext && encodedExperiments) additionalHeaders[EXPERIMENTS_CONTEXT_HEADER] = encodedExperiments;
   if (stateHeader) {
     additionalHeaders["Base44-State"] = stateHeader;
   }
@@ -528,5 +570,6 @@ export function createClientFromRequest(request: Request): Base44Client {
     serviceToken: serviceRoleToken,
     functionsVersion: functionsVersion ?? undefined,
     headers: additionalHeaders,
+    experiments: experimentsContext ? { ...experimentsContext, pageUrl: request.url ? new URL(request.url).pathname : "/" } : undefined,
   });
 }
diff --git a/src/client.types.ts b/src/client.types.ts
@@ -12,6 +12,8 @@ import type { AiGatewayModule } from "./modules/ai-gateway.types.js";
 import type { AppLogsModule } from "./modules/app-logs.types.js";
 import type { AppModule } from "./modules/app.types.js";
 import type { AnalyticsModule } from "./modules/analytics.types.js";
+import type { ExperimentsModule } from "./modules/experiments.types.js";
+import type { ExperimentsContext } from "./modules/experiments-config.types.js";
 import type { ActorsModule } from "./modules/actors.types.js";
 import type { FetchWithAuthInit } from "./utils/fetch-with-auth.js";
 
@@ -44,9 +46,9 @@ export interface CreateClientAnalyticsConfig {
   /**
    * Whether app analytics is enabled for this client.
    *
-   * When disabled, automatic analytics and calls to `analytics.track()` are
-   * no-ops. The SDK does not create an analytics session identifier, start
-   * heartbeat timers, or send analytics requests.
+   * When disabled, automatic analytics, experiment exposures and calls to
+   * `analytics.track()` are no-ops. The SDK does not create an analytics session
+   * identifier, start heartbeat timers, or send analytics requests.
    *
    * @defaultValue `true`
    */
@@ -85,6 +87,12 @@ export interface CreateClientConfig {
    * Omit this option to preserve the default analytics behavior.
    */
   analytics?: CreateClientAnalyticsConfig;
+  /**
+   * Platform-validated context for local flag evaluation. Request-scoped on servers.
+   * Automatically read from the platform bootstrap in browsers and trusted headers
+   * by createClientFromRequest(). Not an authorization credential.
+   */
+  experiments?: ExperimentsContext;
   /**
    * User authentication token. Used to authenticate as a specific user.
    *
@@ -141,6 +149,8 @@ export interface Base44Client {
   connectors: UserConnectorsModule;
   /** {@link EntitiesModule | Entities module} for CRUD operations on your data models. */
   entities: EntitiesModule;
+  /** {@link ExperimentsModule | Experiments module} for local feature flags and exposures. */
+  experiments: ExperimentsModule;
   /** {@link FunctionsModule | Functions module} for invoking custom backend functions. */
   functions: FunctionsModule;
   /** {@link IntegrationsModule | Integrations module} for calling pre-built integration endpoints. */

diff --git a/src/index.ts b/src/index.ts
@@ -33,8 +33,15 @@ export type {
 };
 
 export * from "./types.js";
+export { evaluateExperiments } from "./modules/experiments-evaluator.js";
+export type { ExperimentsConfig, ExperimentsContext, ExperimentsIdentity } from "./modules/experiments-config.types.js";
 
 // Module types
+export type {
+  ExperimentsModule,
+  ExperimentsSnapshot,
+} from "./modules/experiments.types.js";
+
 export type {
   DeleteManyResult,
   DeleteResult,