diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/logging/FirebaseSessionsEnforcementCheck.kt b/firebase-perf/src/main/java/com/google/firebase/perf/logging/FirebaseSessionsEnforcementCheck.kt
index 089611564e8..1efa37050b7 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/logging/FirebaseSessionsEnforcementCheck.kt
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/logging/FirebaseSessionsEnforcementCheck.kt
@@ -16,7 +16,6 @@
 
 package com.google.firebase.perf.logging
 
-import com.google.firebase.perf.session.PerfSession
 import com.google.firebase.perf.session.isLegacy
 import com.google.firebase.perf.v1.PerfSession as ProtoPerfSession
 
@@ -27,19 +26,16 @@ class FirebaseSessionsEnforcementCheck {
     private var logger: AndroidLogger = AndroidLogger.getInstance()
 
     @JvmStatic
-    fun checkSession(sessions: List<ProtoPerfSession>, failureMessage: String) {
-      sessions.forEach { checkSession(it.sessionId, failureMessage) }
-    }
-
-    @JvmStatic
-    fun checkSession(session: PerfSession, failureMessage: String) {
-      checkSession(session.sessionId(), failureMessage)
+    fun checkSessionsList(sessions: List<ProtoPerfSession>, failureMessage: String) {
+      if (sessions.count { it.sessionId.isLegacy() } == sessions.size) {
+        sessions.forEach { checkSession(it.sessionId, failureMessage) }
+      }
     }
 
     @JvmStatic
     fun checkSession(sessionId: String, failureMessage: String) {
       if (sessionId.isLegacy()) {
-        logger.debug("legacy session ${sessionId}: $failureMessage")
+        logger.verbose("Contains Legacy Session ${sessionId}: $failureMessage")
         assert(!enforcement) { failureMessage }
       }
     }
diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/session/FirebasePerformanceSessionSubscriber.kt b/firebase-perf/src/main/java/com/google/firebase/perf/session/FirebasePerformanceSessionSubscriber.kt
index 0f93f45586e..f524e52ed34 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/session/FirebasePerformanceSessionSubscriber.kt
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/session/FirebasePerformanceSessionSubscriber.kt
@@ -17,7 +17,7 @@
 package com.google.firebase.perf.session
 
 import com.google.firebase.perf.config.ConfigResolver
-import com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck
+import com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck.Companion.checkSession
 import com.google.firebase.sessions.api.SessionSubscriber
 
 class FirebasePerformanceSessionSubscriber(val configResolver: ConfigResolver) : SessionSubscriber {
@@ -30,7 +30,7 @@ class FirebasePerformanceSessionSubscriber(val configResolver: ConfigResolver) :
   override fun onSessionChanged(sessionDetails: SessionSubscriber.SessionDetails) {
     val currentPerfSession = SessionManager.getInstance().perfSession()
     // TODO(b/394127311): Add logic to deal with app start gauges if necessary.
-    FirebaseSessionsEnforcementCheck.checkSession(currentPerfSession, "onSessionChanged")
+    checkSession(currentPerfSession.sessionId(), "Existing session in onSessionChanged().")
 
     val updatedSession = PerfSession.createWithId(sessionDetails.sessionId)
     SessionManager.getInstance().updatePerfSession(updatedSession)
diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/session/SessionManager.java b/firebase-perf/src/main/java/com/google/firebase/perf/session/SessionManager.java
index a5f20ec6aa4..873965d7aaa 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/session/SessionManager.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/session/SessionManager.java
@@ -18,7 +18,6 @@
 import android.content.Context;
 import androidx.annotation.Keep;
 import androidx.annotation.VisibleForTesting;
-import com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck;
 import com.google.firebase.perf.session.gauges.GaugeManager;
 import com.google.firebase.perf.v1.GaugeMetadata;
 import com.google.firebase.perf.v1.GaugeMetric;
@@ -46,8 +45,6 @@ public static SessionManager getInstance() {
 
   /** Returns the currently active PerfSession. */
   public final PerfSession perfSession() {
-    FirebaseSessionsEnforcementCheck.checkSession(perfSession, "PerfSession.perfSession()");
-
     return perfSession;
   }
 
@@ -55,7 +52,6 @@ private SessionManager() {
     // Creates a legacy session by default. This is a safety net to allow initializing
     // SessionManager - but the current implementation replaces it immediately.
     this(GaugeManager.getInstance(), PerfSession.createWithId(null));
-    FirebaseSessionsEnforcementCheck.checkSession(perfSession, "SessionManager()");
   }
 
   @VisibleForTesting
@@ -78,9 +74,6 @@ public void setApplicationContext(final Context appContext) {
    * @see PerfSession#isSessionRunningTooLong()
    */
   public void stopGaugeCollectionIfSessionRunningTooLong() {
-    FirebaseSessionsEnforcementCheck.checkSession(
-        perfSession, "SessionManager.stopGaugeCollectionIfSessionRunningTooLong");
-
     if (perfSession.isSessionRunningTooLong()) {
       gaugeManager.stopCollectingGauges();
     }
@@ -158,16 +151,12 @@ public void unregisterForSessionUpdates(WeakReference<SessionAwareObject> client
   }
 
   private void logGaugeMetadataIfCollectionEnabled() {
-    FirebaseSessionsEnforcementCheck.checkSession(
-        perfSession, "logGaugeMetadataIfCollectionEnabled");
     if (perfSession.isVerbose()) {
       gaugeManager.logGaugeMetadata(perfSession.sessionId());
     }
   }
 
   private void startOrStopCollectingGauges() {
-    FirebaseSessionsEnforcementCheck.checkSession(perfSession, "startOrStopCollectingGauges");
-
     if (perfSession.isVerbose()) {
       gaugeManager.startCollectingGauges(perfSession);
     } else {
diff --git a/firebase-perf/src/main/java/com/google/firebase/perf/transport/TransportManager.java b/firebase-perf/src/main/java/com/google/firebase/perf/transport/TransportManager.java
index d1eb5ae059c..d53443e471c 100644
--- a/firebase-perf/src/main/java/com/google/firebase/perf/transport/TransportManager.java
+++ b/firebase-perf/src/main/java/com/google/firebase/perf/transport/TransportManager.java
@@ -14,6 +14,8 @@
 
 package com.google.firebase.perf.transport;
 
+import static com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck.checkSession;
+import static com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck.checkSessionsList;
 import static com.google.firebase.perf.util.AppProcessesProvider.getProcessName;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.MINUTES;
@@ -39,7 +41,6 @@
 import com.google.firebase.perf.config.ConfigResolver;
 import com.google.firebase.perf.logging.AndroidLogger;
 import com.google.firebase.perf.logging.ConsoleUrlGenerator;
-import com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck;
 import com.google.firebase.perf.metrics.validator.PerfMetricValidator;
 import com.google.firebase.perf.session.SessionManager;
 import com.google.firebase.perf.util.Constants;
@@ -300,8 +301,7 @@ public void log(final TraceMetric traceMetric) {
    * {@link #isAllowedToDispatch(PerfMetric)}).
    */
   public void log(final TraceMetric traceMetric, final ApplicationProcessState appState) {
-    FirebaseSessionsEnforcementCheck.checkSession(
-        traceMetric.getPerfSessionsList(), "log TraceMetric");
+    checkSessionsList(traceMetric.getPerfSessionsList(), "log(TraceMetric)");
     executorService.execute(
         () -> syncLog(PerfMetric.newBuilder().setTraceMetric(traceMetric), appState));
   }
@@ -330,8 +330,7 @@ public void log(final NetworkRequestMetric networkRequestMetric) {
    */
   public void log(
       final NetworkRequestMetric networkRequestMetric, final ApplicationProcessState appState) {
-    FirebaseSessionsEnforcementCheck.checkSession(
-        networkRequestMetric.getPerfSessionsList(), "log NetworkRequestMetric");
+    checkSessionsList(networkRequestMetric.getPerfSessionsList(), "log(NetworkRequestMetric)");
     executorService.execute(
         () ->
             syncLog(
@@ -361,7 +360,7 @@ public void log(final GaugeMetric gaugeMetric) {
    * {@link #isAllowedToDispatch(PerfMetric)}).
    */
   public void log(final GaugeMetric gaugeMetric, final ApplicationProcessState appState) {
-    FirebaseSessionsEnforcementCheck.checkSession(gaugeMetric.getSessionId(), "log GaugeMetric");
+    checkSession(gaugeMetric.getSessionId(), "log(GaugeMetric)");
     executorService.execute(
         () -> syncLog(PerfMetric.newBuilder().setGaugeMetric(gaugeMetric), appState));
   }
diff --git a/firebase-perf/src/test/java/com/google/firebase/perf/session/FirebaseSessionsTestHelper.kt b/firebase-perf/src/test/java/com/google/firebase/perf/session/FirebaseSessionsTestHelper.kt
index a617af94a58..dae8afc3db1 100644
--- a/firebase-perf/src/test/java/com/google/firebase/perf/session/FirebaseSessionsTestHelper.kt
+++ b/firebase-perf/src/test/java/com/google/firebase/perf/session/FirebaseSessionsTestHelper.kt
@@ -25,3 +25,5 @@ fun createTestSession(suffix: Int): PerfSession {
 }
 
 fun testSessionId(suffix: Int): String = "abc$suffix"
+
+fun testLegacySessionId(suffix: Int): String = "zabc$suffix"
diff --git a/firebase-perf/src/test/java/com/google/firebase/perf/session/PerfSessionTest.java b/firebase-perf/src/test/java/com/google/firebase/perf/session/PerfSessionTest.java
index f7c8d400483..47c6d745baf 100644
--- a/firebase-perf/src/test/java/com/google/firebase/perf/session/PerfSessionTest.java
+++ b/firebase-perf/src/test/java/com/google/firebase/perf/session/PerfSessionTest.java
@@ -15,7 +15,9 @@
 package com.google.firebase.perf.session;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.firebase.perf.session.FirebaseSessionsHelperKt.isLegacy;
 import static com.google.firebase.perf.session.FirebaseSessionsTestHelperKt.createTestSession;
+import static com.google.firebase.perf.session.FirebaseSessionsTestHelperKt.testLegacySessionId;
 import static com.google.firebase.perf.session.FirebaseSessionsTestHelperKt.testSessionId;
 import static com.google.firebase.perf.util.Constants.PREFS_NAME;
 import static org.mockito.Mockito.mock;
@@ -224,6 +226,57 @@ public void testBuildAndSortMovesTheVerboseSessionToTop() {
     assertThat(PerfSession.isVerbose(perfSessions[0])).isTrue();
   }
 
+  @Test
+  public void testBuildAndSortMovesTheVerboseSessionToTop_legacySession() {
+    // Force all the sessions from now onwards to be non-verbose
+    forceNonVerboseSession();
+
+    // Next, create 3 non-verbose sessions, including a legacy session.
+    List<PerfSession> sessions = new ArrayList<>();
+    sessions.add(PerfSession.createWithId(testLegacySessionId(1)));
+    sessions.add(PerfSession.createWithId(testSessionId(2)));
+    sessions.add(PerfSession.createWithId(testSessionId(3)));
+
+    // Force all the sessions from now onwards to be verbose
+    forceVerboseSession();
+
+    // Next, create 2 verbose sessions
+    sessions.add(PerfSession.createWithId(testSessionId(4)));
+    sessions.add(PerfSession.createWithId(testSessionId(5)));
+
+    // Verify that the first session in the list of sessions was not verbose
+    assertThat(sessions.get(0).isVerbose()).isFalse();
+
+    com.google.firebase.perf.v1.PerfSession[] perfSessions =
+        PerfSession.buildAndSort(ImmutableList.copyOf(sessions));
+
+    // Verify that after building the proto objects for PerfSessions, the first session in the array
+    // of proto objects is a verbose session
+    assertThat(PerfSession.isVerbose(perfSessions[0])).isTrue();
+  }
+
+  @Test
+  public void testBuildAndSortKeepsLegacySessionAtTopWithNoVerboseSessions() {
+    // Force all the sessions from now onwards to be non-verbose
+    forceNonVerboseSession();
+
+    // Next, create 3 non-verbose sessions, including a legacy session.
+    List<PerfSession> sessions = new ArrayList<>();
+    sessions.add(PerfSession.createWithId(testLegacySessionId(1)));
+    sessions.add(PerfSession.createWithId(testSessionId(2)));
+    sessions.add(PerfSession.createWithId(testSessionId(3)));
+
+    // Verify that the first session in the list of sessions was legacy.
+    assertThat(isLegacy(sessions.get(0))).isTrue();
+
+    com.google.firebase.perf.v1.PerfSession[] perfSessions =
+        PerfSession.buildAndSort(ImmutableList.copyOf(sessions));
+
+    // Verify that after building the proto objects for PerfSessions, the first session in the array
+    // of proto objects is a legacy session.
+    assertThat(isLegacy(perfSessions[0].getSessionId())).isTrue();
+  }
+
   @Test
   public void testIsExpiredReturnsFalseWhenCurrentSessionLengthIsLessThanMaxSessionLength() {
     Timer mockTimer = mock(Timer.class);