Spring Boot 4.1.1

Let's not get ahead of ourselves. Spring Boot 4.1.1 is a bug-fix release that landed August 20, 2026 — but it ships with one change that deserves your attention before you hit upgrade.

The One Thing to Watch

The Gradle plugin no longer auto-configures gRPC when the Protobuf plugin is applied. That silent behavior was causing headaches for anyone using Protobuf without gRPC. The fix means you must opt in explicitly: configure the protobuf extension with the grpc plugin using an empty block, and only then will the plugin reconfigure protoc-gen-grpc-java as before. If your build relies on Gradle quietly wiring up gRPC, read this note first — it will break otherwise.

What Got Fixed

• Kafka — consumer-specific security protocol is now respected.
• Structured logging — a failed JSON encode no longer corrupts the next log event on the same thread.
• Micrometer — registries no longer pin the application context; the managed Prometheus version is aligned with Micrometer's registry.
• Redis — the auto-configured message listener container now uses virtual threads when spring.threads.virtual.enabled is true.
• Mongo — the health indicator no longer spins up an excessive number of connections.
• gRPC — health overall-include flag is honored; test server port exposure backs off when gRPC absents.
• Jersey/Cloud Foundry — context refresh failures when Actuator runs without spring-boot-health are resolved.

Real-World Caveats

Beyond the gRPC gradle change, watch the server.servlet.session.cookie.partitioned quirk — setting it to false still emitted the Partitioned attribute, fixed here. And property binding on @Validated classes with wildcard map values no longer throws IllegalStateException.

4.1.1 is a solid stability release, but don't treat it as a no-brainer. Confirm your gRPC Gradle setup before upgrading, then let the rest of the fixes roll through.