Spring Boot 4.2.0-RC1 Moves Buildpacks to Ubuntu 26.04 and Speeds Up Executable Jar Startup
October's Patch Thursday release train brought Spring Boot 4.2.0-RC1, the last milestone before 4.2 goes GA. It contains 113 enhancements, documentation improvements and bug fixes. The default Cloud Native Buildpacks builder is now paketobuildpacks/ubuntu-resolute-builder, based on Ubuntu 26.04. Teams that build OCI images with bootBuildImage or spring-boot:build-image will get the new base image without changing anything, so check any native dependencies or OS-level assumptions in your images before 4.2 ships.
Two other changes in the RC are worth testing. spring-boot-properties-migrator can now fail the application when it finds errors or warnings, instead of only logging them. That makes it practical to run in CI and catch renamed or removed properties before an upgrade reaches production. Startup is also faster, including quicker class and resource lookup inside executable jars.
The same day saw maintenance releases on the supported lines. Spring Boot 4.1.2 carries 126 bug fixes, documentation improvements and dependency upgrades, and Spring Boot 4.0.9 shipped alongside it. If you are already on 4.x, upgrade to the patch release for your line now, and use the RC to test the 4.2 migration.
Read more — Spring Blog
Spring AI 2.1.0-RC1: Session Memory, Tool-Call Confirmation and Message Parts Across Providers
Spring AI 2.1.0-RC1 is built on Boot 4.2.0-RC1 and finishes the move to ordered message parts. OpenAI Chat Completions, Anthropic, Google GenAI, Bedrock Converse, Ollama, Mistral AI and DeepSeek now produce and consume MessagePart content natively. Reasoning blocks, tool calls and opaque payloads such as Anthropic thinking signatures and Gemini thought signatures keep their order across a conversation. A new replay-reasoning-content option lets you stop replaying reasoning_content to endpoints such as Groq that reject the field.
The release adds two features for building agents:
- Session memory: an append-only event log ported from the community Spring AI Session project. Compaction is turn-aware, so it never separates a tool call from its result. It comes with
TurnCountTrigger,WindowCompactionStrategyand an optionalChatModelSummarizer, plus in-memory and JDBC repositories for PostgreSQL, MySQL, MariaDB and H2. Every call must pass a session ID, and there is no shared default session. - Tool-call confirmation:
@Tool(requiresConfirmation = true)pauses the tool-calling loop so your application can approve or deny each call throughToolCallDecision. Policies are set withToolCallConfirmationPolicyandspring.ai.tools.confirmation.*properties. - Search with your own query vector:
similaritySearch(float[], SearchRequest)works on pgvector, Qdrant, Redis, Elasticsearch and OpenSearch. Stores that don't support it fail fast. - Qxotic jinfer: a pure-JVM engine for chat, embedding, text-to-speech and transcription models.
Watch for these upgrade issues. ChatMemory, MessageWindowChatMemory, MessageChatMemoryAdvisor and several memory repositories are now deprecated for removal in 3.0.0. BedrockChatOptions.requestParameters is now a Map<String, Object>, so code that assigns it to a string-valued map won't compile. PgVectorStore no longer writes distance metadata, so read Document#getScore() instead. Dependencies move to MCP Java SDK 2.1.0, OpenAI Java SDK 4.80.0 and Anthropic Java SDK 2.72.0. Spring AI 2.0.2 ships the same fixes for the 2.0 line.
Read more — Spring Blog
Spring Cloud 2026.0.0-RC1 Paddington: OAuth 2 for Config Clients, WebSockets in Gateway MVC, Bus Folded Into Stream
Spring Cloud 2026.0.0-RC1 (Paddington) moves its modules to 5.1.0-RC1 on Spring Boot 4.2.0-RC1. The most useful change for many teams is in Spring Cloud Config: clients can now authenticate to the Config Server with OAuth 2, not only basic auth or custom headers. Spring Cloud Gateway MVC, the servlet-based gateway, adds WebSocket support, closing one of the remaining gaps with the reactive gateway.
Spring Cloud Kubernetes gives the Configuration Watcher high-availability support and upgrades to Fabric8 8.0.0 and Kubernetes Java Client 27.0.0. The release also restructures the project list: Spring Cloud Bus is no longer a standalone project and its code now lives in Spring Cloud Stream. The Bus artifact coordinates haven't changed, so existing dependencies should resolve without edits.
The other modules (Circuitbreaker, Commons, Consul, Function, Netflix, OpenFeign, Task, Vault, Zookeeper) only got version bumps in this RC. The Northfields line received a maintenance release, Spring Cloud 2025.1.4, the same day.
Read more — Spring Blog
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