Create api_changes_list_2026.md + Java Plugin 2026.1 changes

reference_guide/api_changes_list_2026.md

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+<!-- Copyright 2000-2026 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license. -->
+
+# Incompatible Changes in IntelliJ Platform and Plugins API 2026.*
+
+<!--
+Before documenting a breaking API change, please make sure that the change cannot be avoided in an alternative way.
+
+APIs marked with @Deprecated(forRemoval=true), @ApiStatus.Experimental, @ApiStatus.Internal/IntellijInternalApi, or @ApiStatus.ScheduledForRemoval don't need to be documented.
+
+To document a new incompatible change, add a new line with the problem pattern followed by a 2nd line with ": "-prefixed human-readable description
+and recommended fix/action (REQUIRED, please write full sentence ending with '.', see existing entries as reference).
+Non-platform changes must be grouped under relevant section for plugin.
+
+The following problem patterns are supported and must be followed EXACTLY (e.g., no '#' instead of '.'):
+
+<package name> package removed
+
+<class name> class removed
+<class name> class renamed to <new class name>
+<class name> class moved to package <package name>
+
+<class name>.<method name>(<human-readable parameters>) marked abstract
+<class name>.<method name>(<human-readable parameters>) abstract method added
+<class name>.<method name>(<human-readable parameters>) method removed
+<class name>.<method name>(<human-readable parameters>) method moved to the superclass
+<class name>.<method name>(<human-readable parameters>) method return type changed from <before> to <after>
+<class name>.<method name>(<human-readable parameters>) method visibility changed from <before> to <after>
+<class name>.<method name>(<human-readable parameters>) method marked final
+<class name>.<method name>(<human-readable parameters>) method parameter <type> removed
+<class name>.<method name>(<human-readable parameters>) method parameter type changed from <before> to <after>
+<class name>.<method name> method <parameter name> parameter marked @<class name>
+<class name> (class|interface) now (extends|implements) <class name> and inherits its final method <method name>(<human-readable parameters>)?
+<class name> (class|interface) now (extends|implements) <class name> and inherits its abstract method <method name>(<human-readable parameters>)?
+<class name> class now interface
+
+<class name>(<human-readable parameters>) constructor removed
+<class name>(<human-readable parameters>) constructor parameter <type> removed
+<class name>(<human-readable parameters>) constructor parameter type changed from <before> to <after>
+<class name>(<human-readable parameters>) constructor visibility changed from <before> to <after>
+
+<class name>.<field name> field removed
+<class name>.<field name> field moved to the superclass
+<class name>.<field name> field type changed from <before> to <after>
+<class name>.<field name> field visibility changed from <before> to <after>
+
+<property name> property removed from resource bundle <bundle name>
+
+Where the placeholders must be enclosed in code quotes (`name`):
+
+<class name> is a fully-qualified name of the class, e.g. `com.intellij.openapi.actionSystem.AnAction$InnerClass`.
+<method name> is the exact method's name. Note that constructors have dedicated patterns.
+<human-readable parameters> is a string representing parameters, which are not necessarily fully qualified. They do not affect the parser. For example, instead of (java.lang.Object, java.util.List, int) you are free to write (Object, List<String>, int)
+<parameter name> is exact name of the method's parameter
+<property name> is a full name of a property from .properties file, like `some.action.description`
+<bundle name> is a fully qualified name of the property bundle, which includes its package, like `message.IdeBundle`
+
+NOTE: If a code change you're trying to document doesn't match any of the above patterns, please ask in #plugins-verifier
+
+NOTE: You are allowed to prettify the pattern using links: [`org.example.Foo`](https://github.com/JetBrains/intellij-community/tree/master/)
+
+NOTE: Entries not starting with code quotes (`name`) can be added to document non-code changes and will be skipped in API verification.
+-->
+
+<link-summary>List of known Breaking API Changes in 2026.*</link-summary>
+
+<include from="snippets.topic" element-id="apiChangesHeader"/>
+
+<include from="snippets.topic" element-id="apiChangesJavaVersion"/>
+
+<include from="snippets.topic" element-id="gradlePluginVersion"/>
+
+## 2026.1
+
+### Java Plugin 2026.1                                                                                                                                                            
+
+The Java plugin has been split into several modules with their own classloaders.                                                                                                  
+This shouldn't affect plugins that use standard `<depends>com.intellij.java</depends>` dependency.                                                                                
+If a plugin depends on specific Java plugin modules directly, the dependencies should be updated to reference the new module names.