Root cause: the IDE only detected installed JDKs and had no way to get one, so any launch needing a newer JDK than the machine has (latest jdtls needs JDK 25) dead-ended in an error.
Fix: IDEA-style Download JDK (Eclipse Temurin via the Adoptium API, sha256-verified, reusing ide-tools' download/verify code; Windows zip, Linux tar.gz, macOS Contents/Home) into <app-data>/tools/jdks, registered with JDK discovery and rescanned after each download. "Download JDK…" in the Project SDK and Language Server JDK pickers; a one-click `java.downloadJdk` "Download JDK N" on "needs JDK N" errors, which also repoints a too-old language server JDK and restarts jdtls.
Siblings: language server status popup, jdtls launch notification, run console classpath error, debug launch, run configurations without a JDK ≥ the module's Java version, Maven/Gradle sync failures, single-file Java run without `java` on PATH.
Verified in the app on macOS: vendor/version/location queries, the Download JDK dialog from the Language Server JDK picker, a real Temurin 25.0.5 download that runs. Not verified on Windows/Linux.
Fixes#49https://claude.ai/code/session_01VUYsdXA2nkF5v6zsC93dpn
- Languages & Frameworks › Java › Language Server › JDK (languages.java.jdtlsJdk) runs jdtls on its own JDK, like IDEA's JDK for importer; the project keeps compiling and running with the Project JDK.
- Toolchain pages get the Global / This project switch (default This project); Global shows and edits the global layer.
- File › New Projects Setup › Settings for New Projects… edits only the global layer, which new projects inherit.
- Configuration errors (launch_error) show as "Not started" instead of "Crashed".
Fixes#18Fixes#19
Claude-Session: https://claude.ai/code/session_01SaPPsVPuk6ZTNsoUCNCbMv
Project windows are created in setup with the saved theme's frame colour, and the splash covers the first render while the launch project opens, so a window no longer flashes white or the Welcome screen. Single-instance is now release-only so a dev build can run beside an installed release.
l0ng-ai