Remote environment only ships JDK 21 — projects targeting Java 22+ can't compile

Problem

The Claude Code remote sandbox ships with OpenJDK 21 (21.0.10+7-Ubuntu-124.04). Projects targeting newer Java versions (e.g. Java 25 with Spring Boot 4.x) fail at compilation:

Fatal error compiling: error: release version 25 not supported

This means Claude Code can't verify backend changes compile correctly, reducing confidence in code modifications.

Additional context: Maven DNS resolution

Maven Central (repo.maven.apache.org) also fails DNS resolution in the sandbox. The egress proxy is configured via JAVA_TOOL_OPTIONS, but Maven resolves DNS before routing through the proxy. This is fixable with a workaround (mapping the hostname to the proxy IP in /etc/hosts + configuring ~/.m2/settings.xml with proxy credentials), but it would be better handled at the infrastructure level.

Suggestion

• Ship a more recent JDK in the remote container (JDK 25+ or latest EA), or
• Allow users to specify a custom base image / JDK version for their remote environment
• Route Maven Central DNS through the egress proxy at the network level so ./mvnw works out of the box

Environment

• Platform: Claude Code remote (web)
• JDK: openjdk 21.0.10+7-Ubuntu-124.04
• Maven wrapper: works after DNS/proxy workaround, fails at javac