u/guizmaii

zio-temporal — a fork of vitaliihonta/zio-temporal (a ZIO wrapper around Temporal's Java SDK) that's been diverging for a while now — just cut v1.0.0-RC2, and it's a big one.

Jackson is gone. The serialization layer is now built on zio-json instead of Jackson + reflection. That's the headline change, but the real point isn't "we swapped libraries" — it's what it buys you:

Compile-time codec safety. Under the old Jackson integration, a workflow/activity type without a registered Jackson module compiled fine and only failed at runtime — often as a workflow silently hanging on its first execute(). Every type crossing a workflow/activity/signal/query boundary now needs a ZTemporalCodec[T] (usually just derives JsonCodec on the case class), or your build doesn't compile. No more "forgot to register a Scala module" surprises.

Automatic codec registration. The first cut of the migration required manually chaining .addInterface[Workflow] calls into a CodecRegistry. That's gone too — as of RC2, calling ZWorker.addWorkflow[I], ZWorker.addActivityImplementation(...), or client.newWorkflowStub[I](...) (the calls you're already making) auto-registers that interface's codecs. For most workers/clients, derives JsonCodec on your domain types is now the entire migration — no CodecRegistry wiring at all.

A few other things worth knowing:

• Streaming encode: payloads are written directly into Protobuf's ByteString buffer via zio-json's Write bridge, skipping the intermediate String allocation the old reflection-based path required.
• Workflow history replay: histories already recorded under Jackson replay transparently for primitives and case classes. Sum types are the one exception — the JSON shape changed ({"type":"X",...} → {"X":{...}}), so any sealed trait reachable by an in-flight workflow needs @jsonDiscriminator("type") before you upgrade, or replay fails on the old payload. This is covered with a worked example (and the actual failure you'd see) in the migration guide, not just asserted.
• Scala 3 only.

Full migration guide, with every breaking change and worked examples: https://guizmaii-opensource.github.io/zio-temporal/docs/migration-1.0

It's still an RC — feedback, bug reports, and rough edges are exactly what we're looking for before the 1.0.0 final. Repo: https://github.com/guizmaii-opensource/zio-temporal