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Agent skill

Classloading And Runtime Dev

by quarkusio in quarkusio/quarkus

Quarkus split classloading model, runtime-dev module wiring, conditional dependencies, and common classloading mistakes.

Apache-2.0Auto-check passed

Install Classloading And Runtime Dev

skills CLI
$ npx skills add quarkusio/quarkus --skill classloading-and-runtime-dev -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install quarkusio/quarkus classloading-and-runtime-dev --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/quarkusio/quarkus.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/classloading-and-runtime-dev .claude/skills/classloading-and-runtime-dev && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
classloading-and-runtime-dev
GitHub stars
16k
Token cost
~635 tokens
SKILL.md length
203 words
Files
1
Skills in repo
12
Repo updated
First seen
Licence
Apache-2.0

At a glance

Quarkus split classloading model, runtime-dev module wiring, conditional dependencies, and common classloading mistakes.

  • Works in 2 steps: Register as conditional dev dependency → Guard build steps with IsLocalDevelopment
  • SKILL.md covers The Two ClassLoaders, Core Rules, Runtime-Dev Modules and Why This Matters, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Classloading And Runtime Dev is an agent skill from quarkusio/quarkus. Quarkus split classloading model, runtime-dev module wiring, conditional dependencies, and common classloading mistakes.

Its SKILL.md is about 640 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: Quarkus: Supersonic Subatomic Java. The licence is Apache-2.0.

Example prompts

  • “/classloading-and-runtime-dev”

Workflow steps

2 steps, taken from the step headings in SKILL.md.

  1. Register as conditional dev dependency
  2. Guard build steps with IsLocalDevelopment

What it can do on your machine

Read from SKILL.md and the folder at commit 8e813fd. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are xml and java).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Classloading And Runtime Dev loads about 635 tokens when it runs. Until then it costs about 37 tokens; SKILL.md has 203 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~37
When it runs · the whole SKILL.md, loaded when a task matches
~635

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from quarkusio/quarkus at commit 8e813fd, republished under its Apache-2.0 licence (© quarkusio). 203 words, ~635 tokens.

Download SKILL.mdSave it as .claude/skills/classloading-and-runtime-dev/SKILL.md (or your agent's skills folder).
name
classloading-and-runtime-dev
description
Quarkus split classloading model, runtime-dev module wiring, conditional dependencies, and common classloading mistakes.

Classloading and Runtime-Dev Modules

The Two ClassLoaders

  1. Deployment ClassLoader — Used at build time. Has access to all dependencies including deployment-only libraries.
  2. Runtime ClassLoader — Used at application runtime. Only has access to runtime dependencies.

Core Rules

  • Runtime code MUST NOT reference deployment classes. Violations cause ClassNotFoundException at runtime.
  • Deployment code CAN reference runtime classes.
  • Recorders bridge the gap. A @Recorder lives in the runtime module but is invoked from deployment build steps.

Runtime-Dev Modules

Extensions providing dev-mode-only functionality (e.g., Dev UI pages) use a runtime-dev/ module. These classes are only loaded in dev mode, not in production. This requires two steps:

1. Register as conditional dev dependency

In the runtime module's pom.xml, configure quarkus-extension-maven-plugin:

xml
<plugin>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-extension-maven-plugin</artifactId>
    <executions>
        <execution>
            <phase>process-resources</phase>
            <goals>
                <goal>extension-descriptor</goal>
            </goals>
            <configuration>
                <conditionalDevDependencies>
                    <artifact>${project.groupId}:${project.artifactId}-dev:${project.version}</artifact>
                </conditionalDevDependencies>
            </configuration>
        </execution>
    </executions>
</plugin>

Without this, runtime-dev classes will NOT be loaded in dev mode — you get ClassNotFoundException.

2. Guard build steps with IsLocalDevelopment
java
@BuildSteps(onlyIf = IsLocalDevelopment.class)
class MyExtensionDevUIProcessor {
    // Dev UI build steps here
}

Why This Matters

Forgetting conditionalDevDependencies is particularly confusing because:

  • The code compiles without errors
  • It only fails at runtime in dev mode
  • The error message doesn't hint at the missing configuration

Common Mistakes

  • Importing a deployment class in runtime code
  • Using a build-time-only library in a recorder
  • Accessing runtime config during augmentation (build time)
  • Putting user-facing API classes in deployment instead of runtime
  • Forgetting conditionalDevDependencies for runtime-dev modules

© quarkusio, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/classloading-and-runtime-dev of quarkusio/quarkus.

Open the folder on GitHubat commit 8e813fd

Compare with similar skills

Classloading And Runtime Dev next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Classloading And Runtime Dev compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Classloading And Runtime Dev this skillquarkusio/quarkus16k—~635Automated safety check: PassApache-2.0
Quarkus TDDaffaan-m/ECC274k1 repos~6.4kAutomated safety check: PassMIT
Quarkus Securityaffaan-m/ECC274k—~3.1kAutomated safety check: PassMIT
Quarkus Patternsaffaan-m/ECC274k1 repos~5.4kAutomated safety check: PassMIT
Quarkus Patternsaffaan-m/ECC274k—~6.1kAutomated safety check: PassMIT
Quarkus Securityaffaan-m/ECC274k1 repos~3.1kAutomated safety check: PassMIT

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Questions about Classloading And Runtime Dev

What does Classloading And Runtime Dev do?

Quarkus split classloading model, runtime-dev module wiring, conditional dependencies, and common classloading mistakes. Classloading And Runtime Dev is an agent skill from quarkusio/quarkus. Quarkus split classloading model, runtime-dev module wiring, conditional dependencies, and common classloading mistakes.

How do I install Classloading And Runtime Dev in Claude Code?

Run `npx skills add quarkusio/quarkus --skill classloading-and-runtime-dev -a claude-code`. Or copy the skill folder (.agents/skills/classloading-and-runtime-dev in quarkusio/quarkus) into .claude/skills/classloading-and-runtime-dev in your project. Claude Code loads it when a task matches its description.

How do I install Classloading And Runtime Dev in Codex?

Run `npx skills add quarkusio/quarkus --skill classloading-and-runtime-dev -a codex`. Or copy the skill folder (.agents/skills/classloading-and-runtime-dev in quarkusio/quarkus) into .agents/skills/classloading-and-runtime-dev in your project. Codex loads it when a task matches its description.

Can I use Classloading And Runtime Dev in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add quarkusio/quarkus --skill classloading-and-runtime-dev -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/classloading-and-runtime-dev, .gemini/skills/classloading-and-runtime-dev, .github/skills/classloading-and-runtime-dev and .opencode/skills/classloading-and-runtime-dev in your project.

What does Classloading And Runtime Dev need to run?

SKILL.md names no scripts, command-line tools or credentials: Classloading And Runtime Dev is instructions for the agent only.

Does Classloading And Runtime Dev access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Classloading And Runtime Dev safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Classloading And Runtime Dev use?

Classloading And Runtime Dev is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Classloading And Runtime Dev use?

About 635 tokens (SKILL.md is roughly 2.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Classloading And Runtime Dev?

Skills that share tags, products or a category with Classloading And Runtime Dev: Quarkus TDD (affaan-m/ECC, 274k stars), Quarkus Security (affaan-m/ECC, 274k stars), Quarkus Patterns (affaan-m/ECC, 274k stars) and Quarkus Patterns (affaan-m/ECC, 274k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Classloading And Runtime Dev?

quarkusio (a GitHub organization) maintains it in quarkusio/quarkus, which has 15,929 GitHub stars. The repository holds 12 skills in this directory. The repository was last updated on October 6, 2026.

Source: quarkusio/quarkus on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.