included evaluated_at properties in $feature_flag_called events

posthog-android/CHANGELOG.md

@@ -1,5 +1,11 @@
 ## Next
 
+## 3.28.0 - 2025-12-01
+
+- feat: include `evaluated_at` properties in `$feature_flag_called` events ([#321](https://github.com/PostHog/posthog-android/pull/321))
+
+## 3.27.0 - 2025-11-24
+
 - feat: proguard support ([#316](https://github.com/PostHog/posthog-android/pull/316))
 
 ## 3.26.0 - 2025-11-05

posthog-server/CHANGELOG.md

@@ -1,5 +1,9 @@
 ## Next
 
+## 2.2.0 - 2025-12-01
+
+- feat: include `evaluated_at` properties in `$feature_flag_called` events ([#321](https://github.com/PostHog/posthog-android/pull/321))
+
 ## 2.0.1 - 2025-11-24
 
 - fix: Local evaluation properly handles cases when flag dependency should be false ([#320](https://github.com/PostHog/posthog-android/pull/320))

posthog-server/src/main/java/com/posthog/server/internal/FeatureFlagCacheEntry.kt

@@ -9,6 +9,8 @@ internal data class FeatureFlagCacheEntry(
     val flags: Map<String, FeatureFlag>?,
     val timestamp: Long,
     val expiresAt: Long,
+    val requestId: String? = null,
+    val evaluatedAt: Long? = null,
 ) {
     /**
      * Check if this cache entry has expired
@@ -21,6 +23,8 @@ internal data class FeatureFlagCacheEntry(
         var result = flags?.hashCode() ?: 0
         result = 31 * result + (timestamp xor (timestamp ushr 32)).toInt()
         result = 31 * result + (expiresAt xor (expiresAt ushr 32)).toInt()
+        result = 31 * result + (requestId?.hashCode() ?: 0)
+        result = 31 * result + (evaluatedAt?.hashCode() ?: 0)
         return result
     }
 
@@ -31,6 +35,8 @@ internal data class FeatureFlagCacheEntry(
         if (flags != other.flags) return false
         if (timestamp != other.timestamp) return false
         if (expiresAt != other.expiresAt) return false
+        if (requestId != other.requestId) return false
+        if (evaluatedAt != other.evaluatedAt) return false
 
         return true
     }

posthog-server/src/main/java/com/posthog/server/internal/PostHogFeatureFlagCache.kt

@@ -38,20 +38,42 @@ internal class PostHogFeatureFlagCache(
         return entry.flags
     }
 
+    /**
+     * Get full cache entry (including requestId and evaluatedAt) if present and not expired
+     */
+    @Synchronized
+    fun getEntry(key: FeatureFlagCacheKey): FeatureFlagCacheEntry? {
+        val entry = cache[key]
+        if (entry == null) {
+            return null
+        }
+
+        if (entry.isExpired()) {
+            cache.remove(key)
+            return null
+        }
+
+        return entry
+    }
+
     /**
      * Put feature flags into cache with current timestamp
      */
     @Synchronized
     fun put(
         key: FeatureFlagCacheKey,
         flags: Map<String, FeatureFlag>?,
+        requestId: String? = null,
+        evaluatedAt: Long? = null,
     ) {
         val currentTime = System.currentTimeMillis()
         val entry =
             FeatureFlagCacheEntry(
                 flags = flags,
                 timestamp = currentTime,
                 expiresAt = currentTime + maxAgeMs,
+                requestId = requestId,
+                evaluatedAt = evaluatedAt,
             )
 
         cache[key] = entry

posthog-server/src/main/java/com/posthog/server/internal/PostHogFeatureFlags.kt

@@ -259,7 +259,7 @@ internal class PostHogFeatureFlags(
         return try {
             val response = api.flags(distinctId, null, groups, personProperties, groupProperties)
             val flags = response?.flags
-            cache.put(cacheKey, flags)
+            cache.put(cacheKey, flags, response?.requestId, response?.evaluatedAt)
             flags
         } catch (e: Throwable) {
             config.logger.log("Loading remote feature flags failed: $e")
@@ -499,4 +499,48 @@ internal class PostHogFeatureFlags(
     private fun localEvaluationEnabled(): Boolean {
         return localEvaluation && !personalApiKey.isNullOrBlank()
     }
+
+    /**
+     * Get the requestId from the cache for the given distinctId and groups
+     */
+    override fun getRequestId(
+        distinctId: String?,
+        groups: Map<String, String>?,
+        personProperties: Map<String, Any?>?,
+        groupProperties: Map<String, Map<String, Any?>>?,
+    ): String? {
+        if (distinctId == null) {
+            return null
+        }
+        val cacheKey =
+            FeatureFlagCacheKey(
+                distinctId = distinctId,
+                groups = groups,
+                personProperties = personProperties,
+                groupProperties = groupProperties,
+            )
+        return cache.getEntry(cacheKey)?.requestId
+    }
+
+    /**
+     * Get the evaluatedAt from the cache for the given distinctId and groups
+     */
+    override fun getEvaluatedAt(
+        distinctId: String?,
+        groups: Map<String, String>?,
+        personProperties: Map<String, Any?>?,
+        groupProperties: Map<String, Map<String, Any?>>?,
+    ): Long? {
+        if (distinctId == null) {
+            return null
+        }
+        val cacheKey =
+            FeatureFlagCacheKey(
+                distinctId = distinctId,
+                groups = groups,
+                personProperties = personProperties,
+                groupProperties = groupProperties,
+            )
+        return cache.getEntry(cacheKey)?.evaluatedAt
+    }
 }

posthog/CHANGELOG.md

@@ -1,5 +1,10 @@
 ## Next
 
+## 5.2.0 - 2025-11-24
+
+- feat: include `evaluated_at` properties in `$feature_flag_called` events ([#321](https://github.com/PostHog/posthog-android/pull/321))
+
+
 ## 5.1.0 - 2025-11-06
 
 - feat: Add an optional shutdown override to `FeatureFlagInterface` ([#299](https://github.com/PostHog/posthog-android/pull/299))

posthog/api/posthog.api

@@ -611,32 +611,38 @@ public final class com/posthog/internal/PostHogDeviceDateProvider : com/posthog/
 
 public abstract interface class com/posthog/internal/PostHogFeatureFlagsInterface {
 	public abstract fun clear ()V
+	public abstract fun getEvaluatedAt (Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/Long;
 	public abstract fun getFeatureFlag (Ljava/lang/String;Ljava/lang/Object;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/Object;
 	public abstract fun getFeatureFlagPayload (Ljava/lang/String;Ljava/lang/Object;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/Object;
 	public abstract fun getFeatureFlags (Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/util/Map;
+	public abstract fun getRequestId (Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/String;
 	public abstract fun shutDown ()V
 }
 
 public final class com/posthog/internal/PostHogFeatureFlagsInterface$DefaultImpls {
+	public static synthetic fun getEvaluatedAt$default (Lcom/posthog/internal/PostHogFeatureFlagsInterface;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;ILjava/lang/Object;)Ljava/lang/Long;
 	public static synthetic fun getFeatureFlag$default (Lcom/posthog/internal/PostHogFeatureFlagsInterface;Ljava/lang/String;Ljava/lang/Object;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;ILjava/lang/Object;)Ljava/lang/Object;
 	public static synthetic fun getFeatureFlagPayload$default (Lcom/posthog/internal/PostHogFeatureFlagsInterface;Ljava/lang/String;Ljava/lang/Object;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;ILjava/lang/Object;)Ljava/lang/Object;
 	public static synthetic fun getFeatureFlags$default (Lcom/posthog/internal/PostHogFeatureFlagsInterface;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;ILjava/lang/Object;)Ljava/util/Map;
+	public static synthetic fun getRequestId$default (Lcom/posthog/internal/PostHogFeatureFlagsInterface;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;ILjava/lang/Object;)Ljava/lang/String;
 	public static fun shutDown (Lcom/posthog/internal/PostHogFeatureFlagsInterface;)V
 }
 
 public final class com/posthog/internal/PostHogFlagsResponse : com/posthog/internal/PostHogRemoteConfigResponse {
-	public fun <init> (ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;)V
-	public synthetic fun <init> (ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public fun <init> (ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;Ljava/lang/Long;)V
+	public synthetic fun <init> (ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;Ljava/lang/Long;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public final fun component1 ()Z
 	public final fun component2 ()Ljava/util/Map;
 	public final fun component3 ()Ljava/util/Map;
 	public final fun component4 ()Ljava/util/Map;
 	public final fun component5 ()Ljava/util/List;
 	public final fun component6 ()Ljava/lang/String;
-	public final fun copy (ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;)Lcom/posthog/internal/PostHogFlagsResponse;
-	public static synthetic fun copy$default (Lcom/posthog/internal/PostHogFlagsResponse;ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;ILjava/lang/Object;)Lcom/posthog/internal/PostHogFlagsResponse;
+	public final fun component7 ()Ljava/lang/Long;
+	public final fun copy (ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;Ljava/lang/Long;)Lcom/posthog/internal/PostHogFlagsResponse;
+	public static synthetic fun copy$default (Lcom/posthog/internal/PostHogFlagsResponse;ZLjava/util/Map;Ljava/util/Map;Ljava/util/Map;Ljava/util/List;Ljava/lang/String;Ljava/lang/Long;ILjava/lang/Object;)Lcom/posthog/internal/PostHogFlagsResponse;
 	public fun equals (Ljava/lang/Object;)Z
 	public final fun getErrorsWhileComputingFlags ()Z
+	public final fun getEvaluatedAt ()Ljava/lang/Long;
 	public final fun getFeatureFlagPayloads ()Ljava/util/Map;
 	public final fun getFeatureFlags ()Ljava/util/Map;
 	public final fun getFlags ()Ljava/util/Map;
@@ -720,12 +726,13 @@ public final class com/posthog/internal/PostHogRemoteConfig : com/posthog/intern
 	public fun <init> (Lcom/posthog/PostHogConfig;Lcom/posthog/internal/PostHogApi;Ljava/util/concurrent/ExecutorService;Lkotlin/jvm/functions/Function0;)V
 	public synthetic fun <init> (Lcom/posthog/PostHogConfig;Lcom/posthog/internal/PostHogApi;Ljava/util/concurrent/ExecutorService;Lkotlin/jvm/functions/Function0;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun clear ()V
+	public fun getEvaluatedAt (Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/Long;
 	public fun getFeatureFlag (Ljava/lang/String;Ljava/lang/Object;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/Object;
 	public fun getFeatureFlagPayload (Ljava/lang/String;Ljava/lang/Object;Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/Object;
 	public fun getFeatureFlags (Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/util/Map;
 	public final fun getFlagDetails (Ljava/lang/String;)Lcom/posthog/internal/FeatureFlag;
 	public final fun getOnRemoteConfigLoaded ()Lkotlin/jvm/functions/Function0;
-	public final fun getRequestId ()Ljava/lang/String;
+	public fun getRequestId (Ljava/lang/String;Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Ljava/lang/String;
 	public final fun getSurveys ()Ljava/util/List;
 	public final fun isSessionReplayFlagActive ()Z
 	public final fun loadFeatureFlags (Ljava/lang/String;Ljava/lang/String;Ljava/util/Map;Lcom/posthog/PostHogOnFeatureFlags;Lcom/posthog/PostHogOnFeatureFlags;)V

posthog/src/main/java/com/posthog/PostHog.kt

@@ -889,12 +889,14 @@ public class PostHog private constructor(
             remoteConfig?.let {
                 val flagDetails = it.getFlagDetails(key)
                 val requestId = it.getRequestId()
+                val evaluatedAt = it.getEvaluatedAt()
 
                 val props = mutableMapOf<String, Any>()
                 props["\$feature_flag"] = key
                 // value should never be nullabe anyway
                 props["\$feature_flag_response"] = value ?: ""
-                props["\$feature_flag_request_id"] = requestId ?: ""
+                requestId?.let { props["\$feature_flag_request_id"] = it }
+                evaluatedAt?.let { props["\$feature_flag_evaluated_at"] = it }
                 flagDetails?.let {
                     props["\$feature_flag_id"] = it.metadata.id
                     props["\$feature_flag_version"] = it.metadata.version

posthog/src/main/java/com/posthog/PostHogStateless.kt

@@ -432,6 +432,8 @@ public open class PostHogStateless protected constructor(
         distinctId: String,
         key: String,
         value: Any?,
+        requestId: String? = null,
+        evaluatedAt: Long? = null,
     ) {
         if (config?.sendFeatureFlagEvent == true) {
             val isNewlySeen = featureFlagsCalled?.add(distinctId, key, value) ?: false
@@ -440,6 +442,8 @@ public open class PostHogStateless protected constructor(
                 props["\$feature_flag"] = key
                 // value should never be nullable anyway
                 props["\$feature_flag_response"] = value ?: ""
+                requestId?.let { props["\$feature_flag_request_id"] = it }
+                evaluatedAt?.let { props["\$feature_flag_evaluated_at"] = it }
 
                 captureStateless("\$feature_flag_called", distinctId, properties = props)
             }
@@ -467,7 +471,11 @@ public open class PostHogStateless protected constructor(
                 groupProperties,
             ) ?: defaultValue
 
-        sendFeatureFlagCalled(distinctId, key, value)
+        // Get requestId and evaluatedAt from feature flags
+        val requestId = featureFlags?.getRequestId(distinctId, groups, personProperties, groupProperties)
+        val evaluatedAt = featureFlags?.getEvaluatedAt(distinctId, groups, personProperties, groupProperties)
+
+        sendFeatureFlagCalled(distinctId, key, value, requestId, evaluatedAt)
 
         return value
     }

posthog/src/main/java/com/posthog/internal/PostHogFeatureFlagsInterface.kt

@@ -34,4 +34,18 @@ public interface PostHogFeatureFlagsInterface {
     public fun shutDown() {
         // no-op by default
     }
+
+    public fun getRequestId(
+        distinctId: String? = null,
+        groups: Map<String, String>? = null,
+        personProperties: Map<String, Any?>? = null,
+        groupProperties: Map<String, Map<String, Any?>>? = null,
+    ): String?
+
+    public fun getEvaluatedAt(
+        distinctId: String? = null,
+        groups: Map<String, String>? = null,
+        personProperties: Map<String, Any?>? = null,
+        groupProperties: Map<String, Map<String, Any?>>? = null,
+    ): Long?
 }

posthog/src/main/java/com/posthog/internal/PostHogFlagsResponse.kt

@@ -10,6 +10,8 @@ import org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
  * @property featureFlagPayloads the feature flag payloads
  * @property flags the feature flags.
  * @property quotaLimited array of quota limited features
+ * @property requestId the request id generated by the flags server on evaluation
+ * @property evaluatedAt the evaluated at timestamp generated by the flags server on evaluation
  */
 @IgnoreJRERequirement
 @PostHogInternal
@@ -21,4 +23,5 @@ public data class PostHogFlagsResponse(
     val flags: Map<String, FeatureFlag>? = null,
     val quotaLimited: List<String>? = null,
     val requestId: String?,
+    val evaluatedAt: Long?,
 ) : PostHogRemoteConfigResponse()

posthog/src/main/java/com/posthog/internal/PostHogPreferences.kt

@@ -35,6 +35,7 @@ public interface PostHogPreferences {
         internal const val FEATURE_FLAGS = "featureFlags"
         internal const val FEATURE_FLAGS_PAYLOAD = "featureFlagsPayload"
         internal const val FEATURE_FLAG_REQUEST_ID = "feature_flag_request_id"
+        internal const val FEATURE_FLAG_EVALUATED_AT = "feature_flag_evaluated_at"
         internal const val SESSION_REPLAY = "sessionReplay"
         internal const val SURVEYS = "surveys"
         internal const val PERSON_PROPERTIES_FOR_FLAGS = "personPropertiesForFlags"
@@ -61,6 +62,7 @@ public interface PostHogPreferences {
                 BUILD,
                 STRINGIFIED_KEYS,
                 FEATURE_FLAG_REQUEST_ID,
+                FEATURE_FLAG_EVALUATED_AT,
                 FLAGS,
                 PERSON_PROPERTIES_FOR_FLAGS,
                 GROUP_PROPERTIES_FOR_FLAGS,