Release 4.2.0

4.2.0

Nov 13, 2025

New Features

• Added support for Contextual Multi-Armed Bandit (CMAB): Added support for CMAB experiments(Contextual Bandits rules) with new configuration options and cache control. To get decision from CMAB rules, decide and related methods must be used.

CMAB Configuration Options

The following new configuration options have been added for CMAB:

using OptimizelySDK;

// Configure CMAB settings before creating the Optimizely instance
var cmabConfig = new CmabConfig()
    .SetCacheSize(1000)                        // Optional: Set CMAB cache size (default: 1000)
    .SetCacheTtl(TimeSpan.FromMinutes(30));    // Optional: Set CMAB cache TTL (default: 30 minutes)
    // .SetCache(customCache)                  // Optional: Custom cache implementation

OptimizelyFactory.SetCmabConfig(cmabConfig);

var optimizely = OptimizelyFactory.NewDefaultInstance("SDK_KEY_HERE");

CMAB-Related OptimizelyDecideOptions

New decide options are available to control CMAB caching behavior:

• OptimizelyDecideOption.IGNORE_CMAB_CACHE: Bypass CMAB cache for fresh decisions
• OptimizelyDecideOption.RESET_CMAB_CACHE: Clear and reset CMAB cache before making decisions
• OptimizelyDecideOption.INVALIDATE_USER_CMAB_CACHE: Invalidate CMAB cache for the particular user and experiment

using OptimizelySDK.OptimizelyDecisions;

// Example usage with CMAB decide options
var user = optimizely.CreateUserContext("user123");
var decision = user.Decide("feature-flag-key", new[]
{
    OptimizelyDecideOption.IGNORE_CMAB_CACHE
});