Modern Java Development agent plugin

A portable Agent Plugins 1.0 package for version-aware Java development.

The plugin contributes the modern-java skill. The skill detects the project's effective Java compilation target before recommending language features, APIs, tooling, or modernization changes. Guidance is cumulative and grouped by the Java release in which each capability became final.

Package layout

modern-java-development/
├── plugin.json
└── skills/
    └── modern-java/
        ├── SKILL.md
        ├── references/
        │   ├── core-practices.md
        │   ├── enterprise-practices.md
        │   └── release-practices.md
        └── scripts/
            ├── detect_java_version.py
            ├── test_reference_coverage.py
            └── test_detect_java_version.py

Install

Versioned .tar.gz packages and SHA-256 checksums are available from the GitHub Releases. Each archive contains the modern-java-development package directory.

GitHub Copilot CLI

GitHub Copilot CLI supports the Agent Plugins specification. Add the java.evolved marketplace once:

copilot plugin marketplace add javaevolved/javaevolved.github.io

Then install the plugin:

copilot plugin install modern-java-development@javaevolved

See the GitHub Copilot CLI plugin reference for marketplace management and plugin updates.

Claude Code

Claude Code supports the Agent Skills format used by the modern-java skill. Clone this repository and copy the skill to your personal skills directory:

git clone --depth 1 https://github.com/javaevolved/javaevolved.github.io.git
mkdir -p ~/.claude/skills
cp -R javaevolved.github.io/agent-plugins/modern-java-development/skills/modern-java \
  ~/.claude/skills/

For a project-only installation, copy the skill to .claude/skills/modern-java in that project instead. See the Claude Code skills documentation.

OpenAI Codex CLI

Codex CLI also supports Agent Skills. Clone this repository and copy the skill to your personal skills directory:

git clone --depth 1 https://github.com/javaevolved/javaevolved.github.io.git
mkdir -p ~/.agents/skills
cp -R javaevolved.github.io/agent-plugins/modern-java-development/skills/modern-java \
  ~/.agents/skills/

For a project-only installation, copy the skill to .agents/skills/modern-java in that project instead. See the Codex skills documentation.

Claude Code and Codex CLI use their own product-specific plugin manifests, so the instructions above install the portable skill rather than the root Agent Plugins manifest.

Use

When the skill is active, the agent runs the detector from the Java project root:

python3 skills/modern-java/scripts/detect_java_version.py .

Pass an explicit target when build metadata is unavailable:

python3 skills/modern-java/scripts/detect_java_version.py . --java-version 21

The detector emits JSON so an agent can distinguish the selected target from lower-confidence runtime evidence and report conflicting build configuration.

Validate

python3 -m unittest \
  skills/modern-java/scripts/test_detect_java_version.py \
  skills/modern-java/scripts/test_reference_coverage.py

Release

Run the Release agent plugin workflow from the main branch. The first run publishes the manifest's initial 1.0.0 version. Later runs use a patch release by default (1.0.0 to 1.0.1); select Feature release for a minor bump or Major release for a major bump. The two release options are mutually exclusive.