Skip to main content


As outlined in the Workflow Implementation Constraints section, Workflow code has to be deterministic by taking the same code path when replaying history events.
Any Workflow code change that affects the order in which commands are generated breaks this assumption. The solution that allows updating code of already running Workflows is to keep both the old and new code.
When replaying, use the code version that the events were generated with and when executing a new code path, always take the new code.

Worker versioning​

To use Worker Versioning, you need to do the following:

  1. Determine and assign a Build ID to your built Worker code, and opt in to versioning.
  2. Tell the Task Queue your Worker is listening on about that Build ID, and whether its compatible with an existing Build ID.

Assign a Build ID to your Worker​

Let's say you've chosen borsch as your Build ID, which might be a short git commit hash (a reasonable choice as Build ID).
To assign it in your Worker code, assign the following Worker Options:

import zio.temporal.worker._

val options = ZWorkerOptions.default.withBuildId("borsch")

val worker = ZWorkerFactory.newWorker("<task-queue>", options)
// ...

That's all you need to do in your Worker code. Importantly, if you start this Worker, it won't receive any tasks.
That's because you need to tell the Task Queue about your Worker's Build ID first.

Tell the Task Queue about your Worker's Build ID​

Now you can use the SDK (or the Temporal CLI) to tell the Task Queue about your Worker's Build ID. You might want to do this as part of your CI deployment process.

How to do it via Temporal CLI:

temporal task-queue update-build-ids add-new-default --build-id borsch --task-queue "<task-queue>"

How to do it via SDK:

import zio._
import zio.temporal.workflow._
import io.temporal.client._

ZIO.serviceWithZIO[ZWorkflowClient] { workflowClient =>
workflowClient.updateWorkerBuildIdCompatibility("<task-queue>", BuildIdOperation.newIdInNewDefaultSet("borsch"))

This code adds the borsch Build ID to the Task Queue as the sole version in a new version set, which becomes the default for the queue. New Workflows execute on Workers with this Build ID, and existing ones will continue to process by appropriately compatible Workers.

If, instead, you want to add the Build ID to an existing compatible set, you can do this:

ZIO.serviceWithZIO[ZWorkflowClient] { workflowClient =>
workflowClient.updateWorkerBuildIdCompatibility("<task-queue>", BuildIdOperation.newCompatibleVersion("borsch", "some-existing-build-id"))

This code adds borsch to the existing compatible set containing some-existing-build-id and marks it as the new default Build ID for that set.

You can also promote an existing Build ID in a set to be the default for that set:

ZIO.serviceWithZIO[ZWorkflowClient] { workflowClient =>
workflowClient.updateWorkerBuildIdCompatibility("<task-queue>", BuildIdOperation.promoteBuildIdWithinSet("borsch"))

You can also promote an entire set to become the default set for the queue. New Workflows will start using that set's default.

ZIO.serviceWithZIO[ZWorkflowClient] { workflowClient =>
workflowClient.updateWorkerBuildIdCompatibility("<task-queue>", BuildIdOperation.promoteSetByBuildId("borsch"))

Specify versions for Commands​

By default, Activities, Child Workflows, and Continue-as-New use the same compatible version set as the Workflow that invoked them if they're also using the same Task Queue.

If you want to override this behavior, you can specify your intent via the withVersioningIntent method on the activity options, child workflow options, or continue-as-new options objects.

For example, if you want to use the latest default version for an Activity, you can define your Activity Options like this:

import zio._
import zio.temporal._
import zio.temporal.activity._
import zio.temporal.workflow._
import io.temporal.common.VersioningIntent

trait MyActivity {
// ... some activity methods

trait MyWorkflow {
def doSomething(): Unit

class MyWorkflowImpl extends MyWorkflow {
private val activity = ZWorkflow.newActivityStub[MyActivity](
// ...other options

override def doSomething(): Unit = ???
// Building the activity stub