diff --git a/google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseId.java b/google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseId.java
index 3602d0ee080..5b645c9ac77 100644
--- a/google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseId.java
+++ b/google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseId.java
@@ -94,6 +94,15 @@ public static DatabaseId of(String project, String instance, String database) {
     return new DatabaseId(new InstanceId(project, instance), database);
   }
 
+  /** Creates a {@code DatabaseId} with "default" as project id, given instance and database IDs. */
+  public static DatabaseId of(String instance, String database) {
+    String projectId = SpannerOptions.getDefaultProjectId();
+    if (projectId == null) {
+      projectId = "default";
+    }
+    return new DatabaseId(new InstanceId(projectId, instance), database);
+  }
+
   /** Creates a {@code DatabaseId} given the instance identity and database id. */
   public static DatabaseId of(InstanceId instanceId, String database) {
     return new DatabaseId(instanceId, database);
diff --git a/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionClient.java b/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionClient.java
index 0eed13b018c..6878809e4f6 100644
--- a/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionClient.java
+++ b/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionClient.java
@@ -38,6 +38,8 @@ static class SessionId {
     private static final PathTemplate NAME_TEMPLATE =
         PathTemplate.create(
             "projects/{project}/instances/{instance}/databases/{database}/sessions/{session}");
+    private static final PathTemplate EXTERNAL_HOST_NAME_TEMPLATE =
+        PathTemplate.create("instances/{instance}/databases/{database}/sessions/{session}");
     private final DatabaseId db;
     private final String name;
 
@@ -49,10 +51,16 @@ private SessionId(DatabaseId db, String name) {
     static SessionId of(String name) {
       Preconditions.checkNotNull(name);
       Map<String, String> parts = NAME_TEMPLATE.match(name);
+      if (parts == null) {
+        parts = EXTERNAL_HOST_NAME_TEMPLATE.match(name);
+      }
       Preconditions.checkArgument(
           parts != null, "Name should conform to pattern %s: %s", NAME_TEMPLATE, name);
       return of(
-          parts.get("project"), parts.get("instance"), parts.get("database"), parts.get("session"));
+          parts.containsKey("project") ? parts.get("project") : "default",
+          parts.get("instance"),
+          parts.get("database"),
+          parts.get("session"));
     }
 
     /** Creates a {@code SessionId} given project, instance, database and session IDs. */
diff --git a/google-cloud-spanner/src/test/java/com/google/cloud/spanner/SessionClientTests.java b/google-cloud-spanner/src/test/java/com/google/cloud/spanner/SessionClientTests.java
index bcba430c521..27b33cb2fe0 100644
--- a/google-cloud-spanner/src/test/java/com/google/cloud/spanner/SessionClientTests.java
+++ b/google-cloud-spanner/src/test/java/com/google/cloud/spanner/SessionClientTests.java
@@ -20,6 +20,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.mock;
@@ -30,6 +31,7 @@
 import com.google.cloud.grpc.GrpcTransportOptions;
 import com.google.cloud.grpc.GrpcTransportOptions.ExecutorFactory;
 import com.google.cloud.spanner.SessionClient.SessionConsumer;
+import com.google.cloud.spanner.SessionClient.SessionId;
 import com.google.cloud.spanner.spi.v1.SpannerRpc;
 import com.google.cloud.spanner.spi.v1.SpannerRpc.Option;
 import com.google.common.collect.ImmutableMap;
@@ -503,4 +505,23 @@ public void onSessionCreateFailure(Throwable t, int createFailureForSessionCount
     }
     assertThat(returnedSessionCount.get()).isEqualTo(numSessions);
   }
+
+  @SuppressWarnings("unchecked")
+  @Test
+  public void testSessionNamePatterns() {
+    // Valid pattern for host session name
+    String host =
+        "projects/spanner-project/instances/spanner-instance/databases/test-db/sessions/abcd1234";
+    // Valid pattern for external host session name
+    String externalHost = "instances/default/databases/test-db/sessions/abcd1234";
+    try {
+      SessionId hostSession = SessionId.of(host);
+      assertEquals("abcd1234", hostSession.getName());
+      SessionId externalHostSession = SessionId.of(externalHost);
+      assertEquals("abcd1234", externalHostSession.getName());
+      // If no exceptions are thrown, the test will pass
+    } catch (IllegalArgumentException e) {
+      fail("Expected no exception to be thrown, but got: " + e.getMessage());
+    }
+  }
 }