💥 BREAKING CHANGES

ActivityInfo properties related to workflow execution are now nullable

Due to introduction of Standalone Activities feature (see below), the prior assumption that every activity has a scheduling workflow no longer holds true. As a consequence, ActivityInfo methods getWorkflowId, getRunId, getWorkflowRunId, getWorkflowType and getWorkflowNamespace are now marked @Nullable.

As long as Standalone Activities are not being used, it is safe to ignore the resulting nullability errors. However, the recommended migration path is to call ActivityInfo.isInWorkflow() method and handle both cases - this way the activity can be run in standalone context.

Highlights

Spring AI integration

The new temporal-spring-ai module makes Spring AI agents durable on Temporal. Chat model calls run as Temporal Activities recorded in workflow history, so they retry on transient failures and replay deterministically. Tools are dispatched per their type — @ActivityInterface stubs and Nexus stubs as durable operations, @SideEffectTool classes wrapped in Workflow.sideEffect, and plain tools running directly in workflow code — without changing how you write Spring AI code. Vector stores, embeddings, and MCP tool calls are auto-registered when their Spring AI modules are on the classpath. (#2829)

Worker Heartbeating

This release adds a new feature called Worker Heartbeating. This feature spins up a single nexus-only worker per Client/Namespace in the background and periodically sends some basic metrics over to server for all of the workers registered on the same Client/Namespace. This feature is enabled by default. You can interact with the heartbeat data using CLI commands temporal worker list and temporal worker describe to query the data. (#2818)

Standalone Activities (Pre-release)

Activities can now be started directly, independent of any workflow. Use the new ActivityClient class to start, fetch results, and manage lifecycle of Standalone Activity executions. Learn more at https://docs.temporal.io/standalone-activity - Java SDK specific docs coming soon.

Note: although the Server feature is available as Public Preview, Java SDK's implementation is currently still in pre-release stage. (#2858)

gRPC Version Upgrade

Upgraded gRPC dependency to 1.76.0 to resolve network stream corruption issue that could happen if multiple Netty versions are present in the classpath. (#2866)

Bugfixes

Provide default (empty) client config when default user config dir does not exist (#2828)

Add explicit opt-in flags for activity/nexus bean auto-discovery in Spring Boot (#2830)

Fix worker options default application overriding poller behavior (#2838)

What's Changed

2026-04-06 - 522d669 - Fix - provide default (empty) client config when default user config dir does not exist (#2828)
2026-04-06 - 80e6a1c - Claude fix all docstring problems & add check to CI (#2822)
2026-04-07 - 187b778 - Deprecate namespace field in ChildWorkflowOptions (#2831)
2026-04-07 - 2bbf52d - Worker Heartbeating (#2818)
2026-04-07 - f4a26e0 - Fix native-image CI docker build flake (#2832)
2026-04-07 - f8ddd7e - Add doc comment saying when SKIP_YIELD_ON_VERSION was enabled by (#2825)
2026-04-08 - 8716d22 - Add explicit opt-in flags for activity/nexus bean auto-discovery in Spring Boot (#2830)
2026-04-13 - 05ee827 - chore: bump workflowcheck asm version for latest JDK version support (#2835)
2026-04-15 - dce350c - Fix worker options default application overriding poller behavior (#2838)
2026-04-17 - 686a62d - Add temporal-spring-ai module (#2829)
2026-04-17 - b6f4283 - Bump JDK version requirement in Gradle and CI (#2845)
2026-04-18 - a9389e6 - Update and pin all GHA actions (#2847)
2026-04-20 - 69bbb6e - Update Required Temporal Java SDK version in Spring AI README to next upcoming release (#2849)
2026-04-21 - d3c157c - Revise README for project name and preview warning (#2850)
2026-04-23 - 64d5b2e - temporal-spring-ai: guard large media byte[] from entering workflow history (#2860)
2026-04-23 - cad6172 - temporal-spring-ai: attach activity summaries for chat and MCP calls (#2852)
2026-04-23 - ccaf4a6 - temporal-spring-ai: accept ActivityOptions and classify non-retryable AI errors (#2853)
2026-04-24 - 87c519e - temporal-spring-ai: discover MCP clients by type, not by bean name (#2859)
2026-04-24 - 9eae4a8 - temporal-spring-ai: add side-effect replay tests for chat, activity tools, and @SideEffectTool (#2856)
2026-04-24 - c402f55 - temporal-spring-ai: README expansion and default-model-name consolidation (#2861)
2026-04-24 - f109c0c - temporal-spring-ai: preserve Usage and RateLimit in ChatResponse metadata (#2854)
2026-04-27 - 79c9fe5 - temporal-spring-ai: per-model ActivityOptions registry (#2855)
2026-04-27 - 911dd02 - temporal-spring-ai: pass provider-specific ChatOptions through the activity boundary (#2857)
2026-04-27 - cddafe4 - Setup contrib/ directory with CODEOWNERS that is extensible for non-SDK team extensions. (#2862)
2026-04-30 - 3892394 - 💥 Standalone Activities for Java (#2858)
2026-04-30 - 4b2c294 - Update Temporal Cloud-API to v 0.14.0 (#2864)
2026-04-30 - a2c6f37 - Upgraded gRPC to 1.76.0 and Guava to 33.4.8 (#2866)