@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Features
+
+- Add `Session.State.Unhandled` for unhandled errors that do not terminate the process ([#5919](https://github.com/getsentry/sentry-java/pull/5919))
+
 ### Fixes
 
 - Keep dropped tombstone and ANR events dropped, instead of reporting the same app exit again at every app start ([#6002](https://github.com/getsentry/sentry-java/pull/6002))
 
@@ -4324,7 +4324,9 @@ public final class io/sentry/Session : io/sentry/JsonSerializable, io/sentry/Jso
 	public fun getTimestamp ()Ljava/util/Date;
 	public fun getUnknown ()Ljava/util/Map;
 	public fun getUserAgent ()Ljava/lang/String;
+	public fun hasNonTerminatingUnhandledError ()Z
 	public fun isTerminated ()Z
+	public fun recordNonTerminatingUnhandledError ()Z
 	public fun serialize (Lio/sentry/ObjectWriter;Lio/sentry/ILogger;)V
 	public fun setInitAsTrue ()V
 	public fun setUnknown (Ljava/util/Map;)V
@@ -4347,6 +4349,7 @@ public final class io/sentry/Session$JsonKeys {
 	public static final field ERRORS Ljava/lang/String;
 	public static final field INIT Ljava/lang/String;
 	public static final field IP_ADDRESS Ljava/lang/String;
+	public static final field NON_TERMINATING_UNHANDLED_ERROR Ljava/lang/String;
 	public static final field RELEASE Ljava/lang/String;
 	public static final field SEQ Ljava/lang/String;
 	public static final field SID Ljava/lang/String;
@@ -4362,6 +4365,7 @@ public final class io/sentry/Session$State : java/lang/Enum {
 	public static final field Crashed Lio/sentry/Session$State;
 	public static final field Exited Lio/sentry/Session$State;
 	public static final field Ok Lio/sentry/Session$State;
+	public static final field Unhandled Lio/sentry/Session$State;
 	public static fun valueOf (Ljava/lang/String;)Lio/sentry/Session$State;
 	public static fun values ()[Lio/sentry/Session$State;
 }
 
@@ -21,7 +21,13 @@ public enum State {
     Ok,
     Exited,
     Crashed,
-    Abnormal
+    Abnormal,
+    /**
+     * Final status when an unhandled error did not kill the process, such as a Flutter exception.
+     * The session stays {@link #Ok} until {@link Session#end()}. Native crashes still end as {@link
+     * #Crashed}.
+     */
+    Unhandled
   }
 
   /** started timestamp */
@@ -66,6 +72,9 @@ public enum State {
   /** the Abnormal mechanism, e.g. what was the reason for session to become abnormal (ANR) */
   private @Nullable String abnormalMechanism;
 
+  /** Whether an unhandled error occurred that did not terminate the process */
+  private boolean hasNonTerminatingUnhandledError;
+
   /** The session lock, ops should be atomic */
   private final @NotNull AutoClosableReentrantLock sessionLock = new AutoClosableReentrantLock();
 
@@ -188,6 +197,45 @@ public int errorCount() {
     return abnormalMechanism;
   }
 
+  /**
+   * Whether the session experienced an unhandled error that did <em>not</em> terminate the process,
+   * e.g. an unhandled Flutter exception, and so finalizes as {@link State#Unhandled} rather than
+   * {@link State#Exited}. A native crash is also unhandled, but it kills the process and ends the
+   * session as {@link State#Crashed} instead.
+   *
+   * <p>Never sent as a status while the session is alive; it is only persisted with the session.
+   */
+  @ApiStatus.Internal
+  public boolean hasNonTerminatingUnhandledError() {
+    return hasNonTerminatingUnhandledError;
+  }
+
+  /**
+   * Records that an active session experienced an unhandled error which did not terminate the
+   * process, counting the error and advancing the session's sequence without ending it. On {@link
+   * #end()} the session is finalized as {@link State#Unhandled} unless a terminal status such as
+   * {@link State#Crashed} or {@link State#Abnormal} took over first.
+   *
+   * <p>Hybrid SDKs whose unhandled errors do not kill the process. Native Java/Android capture
+   * should not call this.
+   *
+   * @return whether the session was updated, i.e. false if it had already reached a terminal state
+   */
+  @ApiStatus.Internal
+  public boolean recordNonTerminatingUnhandledError() {
+    try (final @NotNull ISentryLifecycleToken ignored = sessionLock.acquire()) {
+      if (status != State.Ok) {
+        return false;
+      }
+      hasNonTerminatingUnhandledError = true;
+      errorCount.incrementAndGet();
+      init = null;
+      timestamp = DateUtils.getCurrentDateTime();
+      sequence = getSequenceTimestamp(timestamp);
+      return true;
+    }
+  }
+
   @SuppressWarnings({"JdkObsolete", "JavaUtilDate"})
   public @Nullable Date getTimestamp() {
     return timestamp;
@@ -209,7 +257,7 @@ public void end(final @Nullable Date timestamp) {
 
       // at this state it might be Crashed already, so we don't check for it.
       if (status == State.Ok) {
-        status = State.Exited;
+        status = hasNonTerminatingUnhandledError ? State.Unhandled : State.Exited;
       }
 
       if (timestamp != null) {
@@ -262,6 +310,11 @@ public boolean update(
       boolean sessionHasBeenUpdated = false;
       if (status != null) {
         this.status = status;
+        // the flag only decides how an Ok session is finalized, so an explicit terminal status
+        // such as a crash or an ANR takes precedence over a non-terminating error.
+        if (status != State.Ok) {
+          hasNonTerminatingUnhandledError = false;
+        }
         sessionHasBeenUpdated = true;
       }
 
@@ -318,21 +371,24 @@ private long getSequenceTimestamp(final @NotNull Date timestamp) {
    */
   @SuppressWarnings("MissingOverride")
   public @NotNull Session clone() {
-    return new Session(
-        status,
-        started,
-        timestamp,
-        errorCount.get(),
-        distinctId,
-        sessionId,
-        init,
-        sequence,
-        duration,
-        ipAddress,
-        userAgent,
-        environment,
-        release,
-        abnormalMechanism);
+    final @NotNull Session session =
+        new Session(
+            status,
+            started,
+            timestamp,
+            errorCount.get(),
+            distinctId,
+            sessionId,
+            init,
+            sequence,
+            duration,
+            ipAddress,
+            userAgent,
+            environment,
+            release,
+            abnormalMechanism);
+    session.hasNonTerminatingUnhandledError = hasNonTerminatingUnhandledError;
+    return session;
   }
 
   // JsonSerializable
@@ -354,6 +410,7 @@ public static final class JsonKeys {
     public static final String IP_ADDRESS = "ip_address";
     public static final String USER_AGENT = "user_agent";
     public static final String ABNORMAL_MECHANISM = "abnormal_mechanism";
+    public static final String NON_TERMINATING_UNHANDLED_ERROR = "non_terminating_unhandled_error";
   }
 
   @Override
@@ -384,6 +441,9 @@ public void serialize(final @NotNull ObjectWriter writer, final @NotNull ILogger
     if (abnormalMechanism != null) {
       writer.name(JsonKeys.ABNORMAL_MECHANISM).value(logger, abnormalMechanism);
     }
+    if (hasNonTerminatingUnhandledError) {
+      writer.name(JsonKeys.NON_TERMINATING_UNHANDLED_ERROR).value(hasNonTerminatingUnhandledError);
+    }
     writer.name(JsonKeys.ATTRS);
     writer.beginObject();
     writer.name(JsonKeys.RELEASE).value(logger, release);
@@ -440,6 +500,7 @@ public static final class Deserializer implements JsonDeserializer<Session> {
       String environment = null;
       String release = null; // @NotNull
       String abnormalMechanism = null;
+      boolean hasNonTerminatingUnhandledError = false;
 
       Map<String, Object> unknown = null;
       while (reader.peek() == JsonToken.NAME) {
@@ -483,6 +544,12 @@ public static final class Deserializer implements JsonDeserializer<Session> {
           case JsonKeys.ABNORMAL_MECHANISM:
             abnormalMechanism = reader.nextStringOrNull();
             break;
+          case JsonKeys.NON_TERMINATING_UNHANDLED_ERROR:
+            final Boolean hasNonTerminatingUnhandledErrorValue = reader.nextBooleanOrNull();
+            hasNonTerminatingUnhandledError =
+                hasNonTerminatingUnhandledErrorValue != null
+                    && hasNonTerminatingUnhandledErrorValue;
+            break;
           case JsonKeys.ATTRS:
             reader.beginObject();
             while (reader.peek() == JsonToken.NAME) {
@@ -542,6 +609,7 @@ public static final class Deserializer implements JsonDeserializer<Session> {
               environment,
               release,
               abnormalMechanism);
+      session.hasNonTerminatingUnhandledError = hasNonTerminatingUnhandledError;
       session.setUnknown(unknown);
       reader.endObject();
       return session;
 
@@ -200,6 +200,51 @@ class PreviousSessionFinalizerTest {
       )
   }
 
+  @Test
+  fun `if previous session has a non-terminating unhandled error and no crash marker, finalizes as unhandled`() {
+    val finalizer =
+      fixture.getSut(
+        tmpDir,
+        session =
+          Session(null, null, null, "io.sentry.sample@1.0").apply {
+            recordNonTerminatingUnhandledError()
+          },
+      )
+    finalizer.run()
+
+    verify(fixture.scopes)
+      .captureEnvelope(
+        argThat {
+          val session = fixture.sessionFromEnvelope(this)
+          session.release == "io.sentry.sample@1.0" &&
+            session.status == Session.State.Unhandled &&
+            session.hasNonTerminatingUnhandledError()
+        }
+      )
+  }
+
+  @Test
+  fun `if previous session has a non-terminating unhandled error but a native crash marker exists, finalizes as crashed`() {
+    val finalizer =
+      fixture.getSut(
+        tmpDir,
+        session =
+          Session(null, null, null, "io.sentry.sample@1.0").apply {
+            recordNonTerminatingUnhandledError()
+          },
+        nativeCrashTimestamp = DateUtils.getDateTime("2023-10-01T00:00:00.000Z"),
+      )
+    finalizer.run()
+
+    verify(fixture.scopes)
+      .captureEnvelope(
+        argThat {
+          val session = fixture.sessionFromEnvelope(this)
+          session.release == "io.sentry.sample@1.0" && session.status == Crashed
+        }
+      )
+  }
+
   @Test
   fun `if previous session file exists, deletes previous session file`() {
     val finalizer = fixture.getSut(tmpDir, sessionFileExists = true)
 
@@ -346,6 +346,36 @@ class EnvelopeCacheTest {
     assertEquals(sessionExitedWithAbnormal, updatedSession!!.timestamp!!.time)
   }
 
+  @Test
+  fun `AbnormalExit hint keeps persisted unhandled session as abnormal`() {
+    val cache = fixture.getSUT()
+
+    val previousSessionFile = EnvelopeCache.getPreviousSessionFile(fixture.options.cacheDirPath!!)
+    val session = createSession().apply { recordNonTerminatingUnhandledError() }
+    fixture.options.serializer.serialize(session, previousSessionFile.bufferedWriter())
+
+    val envelope = SentryEnvelope.from(fixture.options.serializer, SentryEvent(), null)
+    val abnormalHint =
+      object : AbnormalExit {
+        override fun mechanism(): String = "abnormal_mechanism"
+
+        override fun ignoreCurrentThread(): Boolean = false
+
+        override fun timestamp(): Long = session.started!!.time + TimeUnit.HOURS.toMillis(1)
+      }
+    val hints = HintUtils.createWithTypeCheckHint(abnormalHint)
+    cache.storeEnvelope(envelope, hints)
+
+    val updatedSession =
+      fixture.options.serializer.deserialize(
+        previousSessionFile.bufferedReader(),
+        Session::class.java,
+      )
+    assertEquals(State.Abnormal, updatedSession!!.status)
+    assertEquals("abnormal_mechanism", updatedSession.abnormalMechanism)
+    assertFalse(updatedSession.hasNonTerminatingUnhandledError())
+  }
+
   @Test
   fun `when AbnormalExit happened before previous session start, does not mark as abnormal`() {
     val cache = fixture.getSUT()
@@ -400,6 +430,29 @@ class EnvelopeCacheTest {
     assertEquals(nativeCrashTimestamp, updatedSession.timestamp!!.time)
   }
 
+  @Test
+  fun `NativeCrashExit hint keeps persisted unhandled session as crashed`() {
+    val cache = fixture.getSUT()
+
+    val previousSessionFile = EnvelopeCache.getPreviousSessionFile(fixture.options.cacheDirPath!!)
+    val session = createSession().apply { recordNonTerminatingUnhandledError() }
+    fixture.options.serializer.serialize(session, previousSessionFile.bufferedWriter())
+
+    val nativeCrashTimestamp = session.started!!.time + TimeUnit.HOURS.toMillis(1)
+    val envelope = SentryEnvelope.from(fixture.options.serializer, SentryEvent(), null)
+    val hints = HintUtils.createWithTypeCheckHint(NativeCrashExit { nativeCrashTimestamp })
+    cache.storeEnvelope(envelope, hints)
+
+    val updatedSession =
+      fixture.options.serializer.deserialize(
+        previousSessionFile.bufferedReader(),
+        Session::class.java,
+      )
+    assertEquals(State.Crashed, updatedSession!!.status)
+    assertEquals(nativeCrashTimestamp, updatedSession.timestamp!!.time)
+    assertFalse(updatedSession.hasNonTerminatingUnhandledError())
+  }
+
   @Test
   fun `when NativeCrashExit happened before previous session start, does not mark as crashed`() {
     val cache = fixture.getSUT()
 
@@ -1,5 +1,6 @@
 package io.sentry.protocol
 
+import com.google.common.truth.Truth.assertThat
 import io.sentry.DateUtils
 import io.sentry.FileFromResources
 import io.sentry.ILogger
@@ -34,6 +35,34 @@ class SessionSerializationTest {
         "b2d0224b-4b1f-49db-94c9-fd4a439b3ef5",
         "anr_foreground",
       )
+
+    /**
+     * An unhandled session cannot be built by mutating [getSut]: the flag is only reachable through
+     * [Session.recordNonTerminatingUnhandledError], which no-ops unless the session is still `Ok`,
+     * and a terminal status would clear it again. Ending on a fixed timestamp keeps `seq` and
+     * `duration` deterministic.
+     */
+    fun getUnhandledSut() =
+      Session(
+          Session.State.Ok,
+          DateUtils.getDateTime("1945-06-16T06:36:49.000Z"),
+          DateUtils.getDateTime("1970-04-21T09:32:21.000Z"),
+          9001,
+          "631693c2-3d61-4a93-8fd1-89817426ba5a",
+          "3c1ffc32-f68f-4af2-a1ee-dd72f4d62d17",
+          true,
+          4,
+          5.5,
+          "5a174e69-a297-4ba4-b6e1-2244a8299ec8",
+          "790da4ae-50ca-48a2-98f6-9b7f4e05a8c3",
+          "d732be55-b57e-48ec-afe6-b0040c7f93de",
+          "b2d0224b-4b1f-49db-94c9-fd4a439b3ef5",
+          null,
+        )
+        .apply {
+          recordNonTerminatingUnhandledError()
+          end(DateUtils.getDateTime("1970-04-21T09:32:21.000Z"))
+        }
   }
 
   private val fixture = Fixture()
@@ -53,6 +82,22 @@ class SessionSerializationTest {
     assertEquals(expectedJson, actualJson)
   }
 
+  @Test
+  fun serializeUnhandled() {
+    val expected = sanitizedFile("json/session_unhandled.json")
+    val actual = serialize(fixture.getUnhandledSut())
+    assertThat(actual).isEqualTo(expected)
+  }
+
+  @Test
+  fun deserializeUnhandled() {
+    val expectedJson = sanitizedFile("json/session_unhandled.json")
+    val actual = deserialize(expectedJson)
+    assertThat(actual.status).isEqualTo(Session.State.Unhandled)
+    assertThat(actual.hasNonTerminatingUnhandledError()).isTrue()
+    assertThat(serialize(actual)).isEqualTo(expectedJson)
+  }
+
   // Helper
 
   private fun sanitizedFile(path: String): String =