IntelliJ IDEA 2025.3.4 fully supports Java 26
JetBrains offers many new features for Java in its IntelliJ development environment and the Koog agent framework. Additionally, there is a new version of Kotlin.
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The update of the development environment IntelliJ IDEA 2025.3.4 from JetBrains now fully supports Java 26, released on March 17th. Additionally, the company is giving the Koog agent framework a Java API.
After the update, developers can work with all ten of Java 26's major new features, including the five stable ones like HTTP/3 and the five previews, such as Pattern Matching with Primitives.
To enable preview features, set the language level in the IDE to “Language level to 26 (Preview) – Primitive types in patterns (Fourth preview)”. IntelliJ will then display all aids for this language level, including inspections and quick fixes. For preview features, the tool also shows a warning, as users may not want to use them in production code.
JetBrains also supports immature incubator features of Java 26, such as the Vector API. To use it, a special switch is required: --add-modules jdk.incubator.vector.
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In addition, there are minor bug fixes and improvements in the IDE. For example, the update fixes an error that triggers incorrect HTTP requests, and the tab for Dependencies in the Analyze Cyclic Dependencies function now opens correctly. In the DB Explorer, nodes of query files can now be hidden, and there are improvements in auto-completion for the Language Server for Astro.
The corresponding JDK is required for using Java 26. This can be downloaded directly in IntelliJ or with the help of tools like SDKMAN. A new build of Project Valhalla is also available for download. The IntelliJ update can be installed within the IDE using the Toolbox, via Ubuntu Snaps, or downloaded from the website.
Koog and Kotlin
Also new from JetBrains is a Java API for the Koog agent framework, which provides access to all functions of the framework originally developed purely for Kotlin: planning and organization of agentic workflows, all major models, Spring Boot, or Observability.
Also, an update is available for the Kotlin 2.3.30 programming language, which offers a new model for using C libraries and is compatible with Gradle 9.3.
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