optimizely · junaed-optimizely · Nov 6, 2025 · Nov 5, 2025 · Nov 5, 2025
diff --git a/OptimizelySDK.Tests/CmabTests/DefaultCmabClientTest.cs b/OptimizelySDK.Tests/CmabTests/DefaultCmabClientTest.cs
@@ -96,7 +96,7 @@ private static string ValidBody(string variationId = "v1")
         public void FetchDecisionReturnsSuccessNoRetry()
         {
             var http = MakeClient(new ResponseStep(HttpStatusCode.OK, ValidBody("v1")));
-            var client = new DefaultCmabClient(http, retryConfig: null, logger: new NoOpLogger(), errorHandler: new NoOpErrorHandler());
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retryConfig: null, logger: new NoOpLogger(), errorHandler: new NoOpErrorHandler());
             var result = client.FetchDecision("rule-1", "user-1", null, "uuid-1");
 
             Assert.AreEqual("v1", result);
@@ -106,7 +106,7 @@ public void FetchDecisionReturnsSuccessNoRetry()
         public void FetchDecisionHttpExceptionNoRetry()
         {
             var http = MakeClientExceptionSequence(new HttpRequestException("boom"));
-            var client = new DefaultCmabClient(http, retryConfig: null);
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retryConfig: null);
 
             Assert.Throws<CmabFetchException>(() =>
                 client.FetchDecision("rule-1", "user-1", null, "uuid-1"));
@@ -116,7 +116,7 @@ public void FetchDecisionHttpExceptionNoRetry()
         public void FetchDecisionNon2xxNoRetry()
         {
             var http = MakeClient(new ResponseStep(HttpStatusCode.InternalServerError, null));
-            var client = new DefaultCmabClient(http, retryConfig: null);
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retryConfig: null);
 
             Assert.Throws<CmabFetchException>(() =>
                 client.FetchDecision("rule-1", "user-1", null, "uuid-1"));
@@ -126,7 +126,7 @@ public void FetchDecisionNon2xxNoRetry()
         public void FetchDecisionInvalidJsonNoRetry()
         {
             var http = MakeClient(new ResponseStep(HttpStatusCode.OK, "not json"));
-            var client = new DefaultCmabClient(http, retryConfig: null);
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retryConfig: null);
 
             Assert.Throws<CmabInvalidResponseException>(() =>
                 client.FetchDecision("rule-1", "user-1", null, "uuid-1"));
@@ -136,7 +136,7 @@ public void FetchDecisionInvalidJsonNoRetry()
         public void FetchDecisionInvalidStructureNoRetry()
         {
             var http = MakeClient(new ResponseStep(HttpStatusCode.OK, "{\"predictions\":[]}"));
-            var client = new DefaultCmabClient(http, retryConfig: null);
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retryConfig: null);
 
             Assert.Throws<CmabInvalidResponseException>(() =>
                 client.FetchDecision("rule-1", "user-1", null, "uuid-1"));
@@ -147,7 +147,7 @@ public void FetchDecisionSuccessWithRetryFirstTry()
         {
             var http = MakeClient(new ResponseStep(HttpStatusCode.OK, ValidBody("v2")));
             var retry = new CmabRetryConfig(maxRetries: 2, initialBackoff: TimeSpan.Zero, maxBackoff: TimeSpan.FromSeconds(1), backoffMultiplier: 2.0);
-            var client = new DefaultCmabClient(http, retry);
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retry);
             var result = client.FetchDecision("rule-1", "user-1", null, "uuid-1");
 
             Assert.AreEqual("v2", result);
@@ -162,7 +162,7 @@ public void FetchDecisionSuccessWithRetryThirdTry()
                 new ResponseStep(HttpStatusCode.OK, ValidBody("v3"))
             );
             var retry = new CmabRetryConfig(maxRetries: 2, initialBackoff: TimeSpan.Zero, maxBackoff: TimeSpan.FromSeconds(1), backoffMultiplier: 2.0);
-            var client = new DefaultCmabClient(http, retry);
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retry);
             var result = client.FetchDecision("rule-1", "user-1", null, "uuid-1");
 
             Assert.AreEqual("v3", result);
@@ -177,10 +177,40 @@ public void FetchDecisionExhaustsAllRetries()
                 new ResponseStep(HttpStatusCode.InternalServerError, null)
             );
             var retry = new CmabRetryConfig(maxRetries: 2, initialBackoff: TimeSpan.Zero, maxBackoff: TimeSpan.FromSeconds(1), backoffMultiplier: 2.0);
-            var client = new DefaultCmabClient(http, retry);
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, http, retry);
 
             Assert.Throws<CmabFetchException>(() =>
                 client.FetchDecision("rule-1", "user-1", null, "uuid-1"));
         }
+
+        [Test]
+        public void FetchDecision_CustomEndpoint_CallsCorrectUrl()
+        {
+            var customEndpoint = "https://custom.example.com/api/{0}";
+            string capturedUrl = null;
+
+            var handler = new Mock<HttpMessageHandler>(MockBehavior.Strict);
+            handler.Protected()
+                .Setup<Task<HttpResponseMessage>>("SendAsync",
+                    ItExpr.IsAny<HttpRequestMessage>(),
+                    ItExpr.IsAny<CancellationToken>())
+                .Returns((HttpRequestMessage req, CancellationToken _) =>
+                {
+                    capturedUrl = req.RequestUri.ToString();
+                    var response = new HttpResponseMessage(HttpStatusCode.OK)
+                    {
+                        Content = new StringContent(ValidBody("variation123"))
+                    };
+                    return Task.FromResult(response);
+                });
+
+            var http = new HttpClient(handler.Object);
+            var client = new DefaultCmabClient(customEndpoint, http, retryConfig: null);
+            var result = client.FetchDecision("rule-456", "user-1", null, "uuid-1");
+
+            Assert.AreEqual("variation123", result);
+            Assert.AreEqual("https://custom.example.com/api/rule-456", capturedUrl,
+                "Should call custom endpoint with rule ID formatted into template");
+        }
     }
 }
diff --git a/OptimizelySDK.Tests/CmabTests/DefaultCmabServiceTest.cs b/OptimizelySDK.Tests/CmabTests/DefaultCmabServiceTest.cs
@@ -383,7 +383,7 @@ public void ConstructorWithoutConfigUsesDefaultCacheSettings()
         {
             var cache = new LruCache<CmabCacheEntry>(CmabConstants.DEFAULT_CACHE_SIZE,
                 CmabConstants.DEFAULT_CACHE_TTL, _logger);
-            var client = new DefaultCmabClient(null,
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, null,
                 new CmabRetryConfig(1, TimeSpan.FromMilliseconds(100)), _logger);
             var service = new DefaultCmabService(cache, client, _logger);
             var internalCache = GetInternalCache(service) as LruCache<CmabCacheEntry>;
@@ -397,7 +397,7 @@ public void ConstructorWithoutConfigUsesDefaultCacheSettings()
         public void ConstructorAppliesCustomCacheSize()
         {
             var cache = new LruCache<CmabCacheEntry>(42, CmabConstants.DEFAULT_CACHE_TTL, _logger);
-            var client = new DefaultCmabClient(null,
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, null,
                 new CmabRetryConfig(1, TimeSpan.FromMilliseconds(100)), _logger);
             var service = new DefaultCmabService(cache, client, _logger);
             var internalCache = GetInternalCache(service) as LruCache<CmabCacheEntry>;
@@ -413,7 +413,7 @@ public void ConstructorAppliesCustomCacheTtl()
             var expectedTtl = TimeSpan.FromMinutes(3);
             var cache = new LruCache<CmabCacheEntry>(CmabConstants.DEFAULT_CACHE_SIZE, expectedTtl,
                 _logger);
-            var client = new DefaultCmabClient(null,
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, null,
                 new CmabRetryConfig(1, TimeSpan.FromMilliseconds(100)), _logger);
             var service = new DefaultCmabService(cache, client, _logger);
             var internalCache = GetInternalCache(service) as LruCache<CmabCacheEntry>;
@@ -428,7 +428,7 @@ public void ConstructorAppliesCustomCacheSizeAndTtl()
         {
             var expectedTtl = TimeSpan.FromSeconds(90);
             var cache = new LruCache<CmabCacheEntry>(5, expectedTtl, _logger);
-            var client = new DefaultCmabClient(null,
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, null,
                 new CmabRetryConfig(1, TimeSpan.FromMilliseconds(100)), _logger);
             var service = new DefaultCmabService(cache, client, _logger);
             var internalCache = GetInternalCache(service) as LruCache<CmabCacheEntry>;
@@ -442,7 +442,7 @@ public void ConstructorAppliesCustomCacheSizeAndTtl()
         public void ConstructorUsesProvidedCustomCacheInstance()
         {
             var customCache = new LruCache<CmabCacheEntry>(3, TimeSpan.FromSeconds(5), _logger);
-            var client = new DefaultCmabClient(null,
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, null,
                 new CmabRetryConfig(1, TimeSpan.FromMilliseconds(100)), _logger);
             var service = new DefaultCmabService(customCache, client, _logger);
             var cache = GetInternalCache(service);
@@ -455,7 +455,7 @@ public void ConstructorUsesProvidedCustomCacheInstance()
         public void ConstructorAcceptsAnyICacheImplementation()
         {
             var fakeCache = new FakeCache();
-            var client = new DefaultCmabClient(null,
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, null,
                 new CmabRetryConfig(1, TimeSpan.FromMilliseconds(100)), _logger);
             var service = new DefaultCmabService(fakeCache, client, _logger);
             var cache = GetInternalCache(service);
@@ -470,7 +470,7 @@ public void ConstructorCreatesDefaultClientWhenNoneProvided()
         {
             var cache = new LruCache<CmabCacheEntry>(CmabConstants.DEFAULT_CACHE_SIZE,
                 CmabConstants.DEFAULT_CACHE_TTL, _logger);
-            var client = new DefaultCmabClient(null,
+            var client = new DefaultCmabClient(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE, null,
                 new CmabRetryConfig(1, TimeSpan.FromMilliseconds(100)), _logger);
             var service = new DefaultCmabService(cache, client, _logger);
             var internalClient = GetInternalClient(service);

diff --git a/OptimizelySDK.Tests/OptimizelyTest.cs b/OptimizelySDK.Tests/OptimizelyTest.cs
@@ -22,6 +22,7 @@
 using Moq;
 using NUnit.Framework;
 using OptimizelySDK.Bucketing;
+using OptimizelySDK.Cmab;
 using OptimizelySDK.Config;
 using OptimizelySDK.Entity;
 using OptimizelySDK.ErrorHandler;
@@ -6268,5 +6269,76 @@ public void TestConstructedOptimizelyWithDatafileShouldHaveOdpEnabledByDefault()
         }
 
         #endregion
+
+        #region Test Optimizely & CMAB
+
+        [Test]
+        public void TestInitializeCmabServiceWithCustomEndpointPropagatesCorrectly()
+        {
+            var customEndpoint = "https://custom.example.com/predict/{0}";
+            var cmabConfig = new CmabConfig().SetPredictionEndpointTemplate(customEndpoint);
+            var configManager = new Mock<ProjectConfigManager>();
+            var datafileConfig = DatafileProjectConfig.Create(TestData.Datafile, LoggerMock.Object, ErrorHandlerMock.Object);
+            configManager.Setup(cm => cm.GetConfig()).Returns(datafileConfig);
+
+            var optimizely = new Optimizely(
+                configManager: configManager.Object,
+                notificationCenter: null,
+                eventDispatcher: EventDispatcherMock.Object,
+                logger: LoggerMock.Object,
+                errorHandler: ErrorHandlerMock.Object,
+                userProfileService: null,
+                eventProcessor: null,
+                defaultDecideOptions: null,
+                odpManager: null,
+                cmabConfig: cmabConfig
+            );
+
+            var decisionService = optimizely.GetType()
+                .GetField("DecisionService", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(optimizely);
+            var cmabService = decisionService?.GetType()
+                .GetField("CmabService", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(decisionService);
+            var client = cmabService?.GetType()
+                .GetField("_cmabClient", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(cmabService);
+            var actualEndpoint = client?.GetType()
+                .GetField("_predictionEndpointTemplate", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(client) as string;
+
+            Assert.AreEqual(customEndpoint, actualEndpoint, "Custom endpoint should propagate to CMAB client");
+        }
+
+        [Test]
+        public void TestInitializeCmabServiceWithoutCustomEndpointUsesDefault()
+        {
+            var configManager = new Mock<ProjectConfigManager>();
+            var datafileConfig = DatafileProjectConfig.Create(TestData.Datafile, LoggerMock.Object, ErrorHandlerMock.Object);
+            configManager.Setup(cm => cm.GetConfig()).Returns(datafileConfig);
+
+            var optimizely = new Optimizely(
+                configManager: configManager.Object,
+                notificationCenter: null,
+                eventDispatcher: EventDispatcherMock.Object,
+                logger: LoggerMock.Object,
+                errorHandler: ErrorHandlerMock.Object,
+                userProfileService: null,
+                eventProcessor: null,
+                defaultDecideOptions: null,
+                odpManager: null,
+                cmabConfig: null
+            );
+
+            var decisionService = optimizely.GetType()
+                .GetField("DecisionService", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(optimizely);
+            var cmabService = decisionService?.GetType()
+                .GetField("CmabService", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(decisionService);
+            var client = cmabService?.GetType()
+                .GetField("_cmabClient", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(cmabService);
+            var actualEndpoint = client?.GetType()
+                .GetField("_predictionEndpointTemplate", BindingFlags.NonPublic | BindingFlags.Instance)?.GetValue(client) as string;
+
+            Assert.AreEqual(CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE,
+                actualEndpoint, "Should use default endpoint when no config provided");
+        }
+
+        #endregion
     }
 }
diff --git a/OptimizelySDK/Cmab/CmabConfig.cs b/OptimizelySDK/Cmab/CmabConfig.cs
@@ -43,6 +43,11 @@ public class CmabConfig
         /// </summary>
         public ICacheWithRemove<CmabCacheEntry> Cache { get; private set; }
 
+        /// <summary>
+        ///     Gets or sets the prediction endpoint URL template for CMAB requests.
+        /// </summary>
+        public string PredictionEndpointTemplate { get; private set; } = CmabConstants.DEFAULT_PREDICTION_URL_TEMPLATE;
+
         /// <summary>
         ///     Sets the maximum number of entries in the CMAB cache.
         /// </summary>
@@ -58,7 +63,7 @@ public CmabConfig SetCacheSize(int cacheSize)
         ///     Sets the time-to-live for CMAB cache entries.
         /// </summary>
         /// <param name="cacheTtl">Time-to-live for cache entries.</param>
-        /// <returns>This CmabConfig instance for method chaining.</returns>
+        /// <returns>CmabConfig instance</returns>
         public CmabConfig SetCacheTtl(TimeSpan cacheTtl)
         {
             CacheTtl = cacheTtl;
@@ -70,11 +75,22 @@ public CmabConfig SetCacheTtl(TimeSpan cacheTtl)
         ///     When set, CacheSize and CacheTtl will be ignored.
         /// </summary>
         /// <param name="cache">Custom cache implementation for CMAB decisions.</param>
-        /// <returns>This CmabConfig instance for method chaining.</returns>
+        /// <returns>CmabConfig Instance</returns>
         public CmabConfig SetCache(ICacheWithRemove<CmabCacheEntry> cache)
         {
             Cache = cache ?? throw new ArgumentNullException(nameof(cache));
             return this;
         }
+
+        /// <summary>
+        ///     Sets the prediction endpoint URL template for CMAB requests.
+        /// </summary>
+        /// <param name="template">The URL template</param>
+        /// <returns>CmabConfig Instance</returns>
+        public CmabConfig SetPredictionEndpointTemplate(string template)
+        {
+            PredictionEndpointTemplate = template;
+            return this;
+        }
     }
 }
diff --git a/OptimizelySDK/Cmab/CmabConstants.cs b/OptimizelySDK/Cmab/CmabConstants.cs
@@ -20,7 +20,7 @@ namespace OptimizelySDK.Cmab
 {
     internal static class CmabConstants
     {
-        public const string PREDICTION_URL = "https://prediction.cmab.optimizely.com/predict";
+        public const string DEFAULT_PREDICTION_URL_TEMPLATE = "https://prediction.cmab.optimizely.com/predict/{0}";
         public const int DEFAULT_CACHE_SIZE = 10_000;
         public const string CONTENT_TYPE = "application/json";
 

diff --git a/OptimizelySDK/Cmab/DefaultCmabClient.cs b/OptimizelySDK/Cmab/DefaultCmabClient.cs
@@ -38,13 +38,16 @@ public class DefaultCmabClient : ICmabClient
         private readonly CmabRetryConfig _retryConfig;
         private readonly ILogger _logger;
         private readonly IErrorHandler _errorHandler;
+        private readonly string _predictionEndpointTemplate;
 
         public DefaultCmabClient(
+            string predictionEndpointTemplate,
             HttpClient httpClient = null,
             CmabRetryConfig retryConfig = null,
             ILogger logger = null,
             IErrorHandler errorHandler = null)
         {
+            _predictionEndpointTemplate = predictionEndpointTemplate;
             _httpClient = httpClient ?? new HttpClient();
             _retryConfig = retryConfig;
             _logger = logger ?? new NoOpLogger();
@@ -58,7 +61,7 @@ private async Task<string> FetchDecisionAsync(
             string cmabUuid,
             TimeSpan? timeout = null)
         {
-            var url = $"{CmabConstants.PREDICTION_URL}/{ruleId}";
+            var url = string.Format(_predictionEndpointTemplate, ruleId);
             var body = BuildRequestBody(ruleId, userId, attributes, cmabUuid);
             var perAttemptTimeout = timeout ?? CmabConstants.MAX_TIMEOUT;
 

diff --git a/OptimizelySDK/Optimizely.cs b/OptimizelySDK/Optimizely.cs
@@ -146,7 +146,7 @@
            try
            {
 #if USE_ODP
                InitializeComponents(eventDispatcher, logger, errorHandler, userProfileService,
                    null, eventProcessor, defaultDecideOptions, odpManager);
 #else
                InitializeComponents(eventDispatcher, logger, errorHandler, userProfileService,
@@ -218,7 +218,7 @@
            ProjectConfigManager = configManager;

 #if USE_ODP && USE_CMAB
            InitializeComponents(eventDispatcher, logger, errorHandler, userProfileService,
                notificationCenter, eventProcessor, defaultDecideOptions, odpManager, null, cmabConfig);
 #elif USE_ODP
            InitializeComponents(eventDispatcher, logger, errorHandler, userProfileService,
@@ -299,7 +299,7 @@
 
             var cmabRetryConfig = new CmabRetryConfig(CmabConstants.CMAB_MAX_RETRIES,
                 CmabConstants.CMAB_INITIAL_BACKOFF);
-            var cmabClient = new DefaultCmabClient(null, cmabRetryConfig, Logger);
+            var cmabClient = new DefaultCmabClient(config.PredictionEndpointTemplate, null, cmabRetryConfig, Logger, null);
 
             cmabService = new DefaultCmabService(cache, cmabClient, Logger);