For tests

transact/src/main/java/dev/dbos/transact/DBOS.java

@@ -515,6 +515,17 @@ public static <T, E extends Exception> T getResult(@NonNull String workflowId) t
     return executor("getWorkflowStatus").getWorkflowStatus(workflowId);
   }
 
+  /**
+   * Get the serialization format of the current workflow context.
+   *
+   * @return the serialization format name (e.g., "portable_json", "java_jackson"), or null if not
+   *     in a workflow context or using default serialization
+   */
+  public static @Nullable SerializationStrategy getSerialization() {
+    var ctx = DBOSContextHolder.get();
+    return ctx != null ? ctx.getSerialization() : null;
+  }
+
   /**
    * Send a message to a workflow
    *
@@ -528,8 +539,33 @@ public static void send(
       @NonNull Object message,
       @NonNull String topic,
       @Nullable String idempotencyKey) {
+    send(destinationId, message, topic, idempotencyKey, null);
+  }
+
+  /**
+   * Send a message to a workflow with serialization strategy
+   *
+   * @param destinationId recipient of the message
+   * @param message message to be sent
+   * @param topic topic to which the message is send
+   * @param idempotencyKey optional idempotency key for exactly-once send
+   * @param serialization serialization strategy to use (null for default)
+   */
+  public static void send(
+      @NonNull String destinationId,
+      @NonNull Object message,
+      @NonNull String topic,
+      @Nullable String idempotencyKey,
+      @Nullable SerializationStrategy serialization) {
+    if (serialization == null) serialization = SerializationStrategy.DEFAULT;
     executor("send")
-        .send(destinationId, message, topic, instance().internalWorkflowsService, idempotencyKey);
+        .send(
+            destinationId,
+            message,
+            topic,
+            instance().internalWorkflowsService,
+            idempotencyKey,
+            serialization);
   }
 
   /**
@@ -541,7 +577,7 @@ public static void send(
    */
   public static void send(
       @NonNull String destinationId, @NonNull Object message, @NonNull String topic) {
-    DBOS.send(destinationId, message, topic, null);
+    DBOS.send(destinationId, message, topic, null, null);
   }
 
   /**
@@ -556,13 +592,29 @@ public static void send(
   }
 
   /**
-   * Call within a workflow to publish a key value pair
+   * Call within a workflow to publish a key value pair. Uses the workflow's serialization format.
    *
    * @param key identifier for published data
    * @param value data that is published
    */
   public static void setEvent(@NonNull String key, @NonNull Object value) {
-    executor("setEvent").setEvent(key, value);
+    setEvent(key, value, null);
+  }
+
+  /**
+   * Call within a workflow to publish a key value pair with a specific serialization strategy.
+   *
+   * @param key identifier for published data
+   * @param value data that is published
+   * @param serialization serialization strategy to use (null to use workflow's default)
+   */
+  public static void setEvent(
+      @NonNull String key, @NonNull Object value, @Nullable SerializationStrategy serialization) {
+    // If no explicit serialization specified, use the workflow context's serialization
+    if (serialization == null) {
+      serialization = getSerialization();
+    }
+    executor("setEvent").setEvent(key, value, serialization);
   }
 
   /**

transact/src/main/java/dev/dbos/transact/DBOSClient.java

@@ -3,8 +3,10 @@
 import dev.dbos.transact.database.Result;
 import dev.dbos.transact.database.SystemDatabase;
 import dev.dbos.transact.execution.DBOSExecutor;
+import dev.dbos.transact.json.SerializationUtil;
 import dev.dbos.transact.workflow.ForkOptions;
 import dev.dbos.transact.workflow.ListWorkflowsInput;
+import dev.dbos.transact.workflow.SerializationStrategy;
 import dev.dbos.transact.workflow.StepInfo;
 import dev.dbos.transact.workflow.Timeout;
 import dev.dbos.transact.workflow.WorkflowHandle;
@@ -15,6 +17,7 @@
 import java.time.Duration;
 import java.time.Instant;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.UUID;
@@ -123,7 +126,8 @@ public record EnqueueOptions(
       @Nullable Instant deadline,
       @Nullable String deduplicationId,
       @Nullable Integer priority,
-      @Nullable String queuePartitionKey) {
+      @Nullable String queuePartitionKey,
+      @Nullable SerializationStrategy serialization) {
 
     public EnqueueOptions {
       if (Objects.requireNonNull(workflowName, "EnqueueOptions workflowName must not be null")
@@ -169,7 +173,7 @@ public record EnqueueOptions(
     /** Construct `EnqueueOptions` with a minimum set of required options */
     public EnqueueOptions(
         @NonNull String className, @NonNull String workflowName, @NonNull String queueName) {
-      this(workflowName, queueName, className, "", null, null, null, null, null, null, null);
+      this(workflowName, queueName, className, "", null, null, null, null, null, null, null, null);
     }
 
     /**
@@ -190,7 +194,8 @@ public EnqueueOptions(
           this.deadline,
           this.deduplicationId,
           this.priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -212,7 +217,8 @@ public EnqueueOptions(
           this.deadline,
           this.deduplicationId,
           this.priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -234,7 +240,8 @@ public EnqueueOptions(
           this.deadline,
           this.deduplicationId,
           this.priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -256,7 +263,8 @@ public EnqueueOptions(
           this.deadline,
           this.deduplicationId,
           this.priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -278,7 +286,8 @@ public EnqueueOptions(
           deadline,
           this.deduplicationId,
           this.priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -300,7 +309,8 @@ public EnqueueOptions(
           this.deadline,
           deduplicationId,
           this.priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -322,7 +332,8 @@ public EnqueueOptions(
           this.deadline,
           this.deduplicationId,
           this.priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -343,7 +354,8 @@ public EnqueueOptions(
           this.deadline,
           this.deduplicationId,
           priority,
-          this.queuePartitionKey);
+          this.queuePartitionKey,
+          this.serialization);
     }
 
     /**
@@ -366,7 +378,33 @@ public EnqueueOptions(
           this.deadline,
           this.deduplicationId,
           this.priority,
-          partitionKey);
+          partitionKey,
+          this.serialization);
+    }
+
+    /**
+     * Specify the serialization strategy for the workflow arguments.
+     *
+     * @param serialization The serialization strategy ({@link SerializationStrategy#PORTABLE} for
+     *     cross-language compatibility, {@link SerializationStrategy#NATIVE} for Java-specific, or
+     *     {@link SerializationStrategy#DEFAULT} for the default behavior)
+     * @return New `EnqueueOptions` with the serialization strategy set
+     */
+    public @NonNull EnqueueOptions withSerialization(
+        @Nullable SerializationStrategy serialization) {
+      return new EnqueueOptions(
+          this.workflowName,
+          this.queueName,
+          this.className,
+          this.instanceName,
+          this.workflowId,
+          this.appVersion,
+          this.timeout,
+          this.deadline,
+          this.deduplicationId,
+          this.priority,
+          this.queuePartitionKey,
+          serialization);
     }
 
     /**
@@ -392,6 +430,9 @@ public EnqueueOptions(
   public <T, E extends Exception> @NonNull WorkflowHandle<T, E> enqueueWorkflow(
       @NonNull EnqueueOptions options, @Nullable Object[] args) {
 
+    String serializationFormat =
+        options.serialization() != null ? options.serialization().formatName() : null;
+
     return DBOSExecutor.enqueueWorkflow(
         Objects.requireNonNull(
             options.workflowName(), "EnqueueOptions workflowName must not be null"),
@@ -409,14 +450,89 @@ public EnqueueOptions(
             options.priority,
             options.queuePartitionKey,
             false,
-            false),
+            false,
+            serializationFormat),
         null,
         null,
         null,
         options.appVersion,
         systemDatabase);
   }
 
+  /**
+   * Enqueue a workflow using portable JSON serialization. This method is intended for
+   * cross-language workflow initiation where the workflow function definition may not be available
+   * in Java. Unlike {@link #enqueueWorkflow}, this method does not validate function names or
+   * arguments.
+   *
+   * @param <T> Return type of workflow function
+   * @param <E> Exception thrown by workflow function
+   * @param options `DBOSClient.EnqueueOptions` for enqueuing the workflow
+   * @param positionalArgs Positional arguments to pass to the workflow function
+   * @param namedArgs Optional named arguments (for workflows that support them, e.g., Python
+   *     kwargs)
+   * @return WorkflowHandle for retrieving workflow ID, status, and results
+   */
+  public <T, E extends Exception> @NonNull WorkflowHandle<T, E> enqueuePortableWorkflow(
+      @NonNull EnqueueOptions options,
+      @Nullable Object[] positionalArgs,
+      @Nullable Map<String, Object> namedArgs) {
+
+    String workflowId =
+        Objects.requireNonNullElseGet(options.workflowId(), () -> UUID.randomUUID().toString());
+
+    // Serialize arguments in portable format
+    SerializationUtil.SerializedResult serializedArgs =
+        SerializationUtil.serializeArgs(
+            positionalArgs, namedArgs, SerializationUtil.PORTABLE, null);
+
+    // Create workflow status directly with portable serialization
+    var statusBuilder =
+        WorkflowStatusInternal.builder(workflowId, WorkflowState.ENQUEUED)
+            .name(options.workflowName())
+            .className(options.className())
+            .instanceName(Objects.requireNonNullElse(options.instanceName(), ""))
+            .queueName(options.queueName())
+            .inputs(serializedArgs.serializedValue())
+            .serialization(serializedArgs.serialization())
+            .createdAt(System.currentTimeMillis())
+            .deduplicationId(options.deduplicationId())
+            .priority(Objects.requireNonNullElse(options.priority(), 0))
+            .queuePartitionKey(options.queuePartitionKey())
+            .appVersion(options.appVersion());
+
+    if (options.timeout() != null) {
+      statusBuilder.timeoutMs(options.timeout().toMillis());
+    }
+    if (options.deadline() != null) {
+      statusBuilder.deadlineEpochMs(options.deadline().toEpochMilli());
+    }
+
+    var status = statusBuilder.build();
+
+    systemDatabase.initWorkflowStatus(status, null, false, false);
+
+    return new WorkflowHandleClient<>(workflowId);
+  }
+
+  /** Options for sending a message. */
+  public record SendOptions(@Nullable SerializationStrategy serialization) {
+    /** Create SendOptions with default serialization. */
+    public static SendOptions defaults() {
+      return new SendOptions(SerializationStrategy.DEFAULT);
+    }
+
+    /** Create SendOptions with portable JSON serialization. */
+    public static SendOptions portable() {
+      return new SendOptions(SerializationStrategy.PORTABLE);
+    }
+
+    /** Create SendOptions with native Java serialization. */
+    public static SendOptions nativeSerialization() {
+      return new SendOptions(SerializationStrategy.NATIVE);
+    }
+  }
+
   /**
    * Send a message to a workflow
    *
@@ -430,17 +546,42 @@ public void send(
       @NonNull Object message,
       @NonNull String topic,
       @Nullable String idempotencyKey) {
+    send(destinationId, message, topic, idempotencyKey, null);
+  }
+
+  /**
+   * Send a message to a workflow with serialization options
+   *
+   * @param destinationId workflowId of the workflow to receive the message
+   * @param message Message contents
+   * @param topic Topic for the message
+   * @param idempotencyKey If specified, use the value to ensure exactly-once send semantics
+   * @param options Optional send options including serialization type
+   */
+  public void send(
+      @NonNull String destinationId,
+      @NonNull Object message,
+      @NonNull String topic,
+      @Nullable String idempotencyKey,
+      @Nullable SendOptions options) {
     if (idempotencyKey == null) {
       idempotencyKey = UUID.randomUUID().toString();
     }
     var workflowId = "%s-%s".formatted(destinationId, idempotencyKey);
 
+    String serializationFormat =
+        (options != null && options.serialization() != null)
+            ? options.serialization().formatName()
+            : null;
+
     var status =
         WorkflowStatusInternal.builder(workflowId, WorkflowState.SUCCESS)
             .name("temp_workflow-send-client")
+            .serialization(
+                serializationFormat != null ? serializationFormat : SerializationUtil.NATIVE)
             .build();
     systemDatabase.initWorkflowStatus(status, null, false, false);
-    systemDatabase.send(status.workflowId(), 0, destinationId, message, topic);
+    systemDatabase.send(status.workflowId(), 0, destinationId, message, topic, serializationFormat);
   }
 
   /**