README

TYPO3 CKEditor 5 Development Skill

Expert patterns for CKEditor 5 integration in TYPO3, including custom plugin development, configuration, and migration from CKEditor 4.

🔌 Compatibility

This is an Agent Skill following the open standard originally developed by Anthropic and released for cross-platform use.

Supported Platforms:

✅ Claude Code (Anthropic)
✅ Cursor
✅ GitHub Copilot
✅ Other skills-compatible AI agents

Skills are portable packages of procedural knowledge that work across any AI agent supporting the Agent Skills specification.

Features

CKEditor 5 Architecture: Plugin system, schema and conversion system, command pattern implementation, UI component development
TYPO3 Integration: RTE configuration (YAML), custom plugin registration, content element integration, backend module integration
Migration Patterns: CKEditor 4 to 5 migration, custom plugin conversion, configuration transformation, data migration strategies
Plugin Development: Complete patterns for creating custom CKEditor 5 plugins with schema definitions, converters, and commands
Configuration Management: YAML-based RTE presets with toolbar, heading, table, and link configurations
ES6 Module Development: Modern JavaScript patterns for CKEditor 5 plugin architecture

Installation

Marketplace (Recommended)

Add the Netresearch marketplace once, then browse and install skills:

# Claude Code
/plugin marketplace add netresearch/claude-code-marketplace
/plugin install typo3-ckeditor5@netresearch-claude-code-marketplace

Without a marketplace

Since Claude Code 2.1.157 a plugin directory under your personal skills directory loads on its own:

mkdir -p ~/.claude/skills
git clone https://github.com/netresearch/typo3-ckeditor5-skill.git \
  ~/.claude/skills/typo3-ckeditor5

It loads as typo3-ckeditor5@skills-dir on the next session. Update with git -C ~/.claude/skills/typo3-ckeditor5 pull and start a new session; remove it by deleting the directory. This route has no claude plugin update.

npx (skills.sh)

Install with any Agent Skills-compatible agent:

npx skills add https://github.com/netresearch/typo3-ckeditor5-skill --skill typo3-ckeditor5

Download Release

Download the latest release and extract to your agent's skills directory.

Git Clone

git clone https://github.com/netresearch/typo3-ckeditor5-skill.git

Composer (PHP Projects)

composer require netresearch/typo3-ckeditor5-skill

Requires netresearch/composer-agent-skill-plugin.

Usage

This skill is automatically triggered when:

Developing custom CKEditor 5 plugins for TYPO3
Configuring RTE presets in TYPO3 v12+
Integrating CKEditor with TYPO3 backend modules
Migrating from CKEditor 4 to CKEditor 5
Working with CKEditor 5 schema, conversion, or command patterns

Example queries:

"Create a custom CKEditor 5 plugin for TYPO3"
"Configure RTE preset with custom toolbar"
"Migrate CKEditor 4 plugin to CKEditor 5"
"Implement custom element with schema and converters"

Structure

typo3-ckeditor5-skill/
├── skills/typo3-ckeditor5/
│   ├── SKILL.md                          # Skill metadata and core patterns
│   ├── checkpoints.yaml                  # CK-XX checkpoints for assessment tools
│   ├── references/
│   │   ├── ckeditor5-architecture.md     # CKEditor 5 gotchas (figcaption, view vs DOM)
│   │   ├── typo3-integration.md          # TYPO3-specific integration patterns
│   │   ├── plugin-development.md         # TYPO3 plugin wiring and gotchas
│   │   └── migration-guide.md            # CKEditor 4 to 5 migration
│   └── scripts/
│       └── verify-ckeditor5.sh           # Verification script
├── tests/                                # Behavioural tests for the scripts
├── evals/                                # Skill evaluation suite and A/B runner
├── Build/                                # Version check and pre-push hook
└── docs/                                 # Architecture and security assurance case

Expertise Areas

CKEditor 5 Architecture

Plugin system and architecture
Schema and conversion system
Command pattern implementation
UI component development

TYPO3 Integration

RTE configuration (YAML)
Custom plugin registration
Content element integration
Backend module integration

Migration Patterns

CKEditor 4 to 5 migration
Custom plugin conversion
Configuration transformation
Data migration strategies

Related Skills

typo3-extension-upgrade-skill: References this skill for RTE migration
php-modernization-skill: Modern PHP patterns for backend integration

Contributing

Open issues and pull requests on GitHub. The commands for working on this repository are listed in AGENTS.md. A pull request that adds or changes behaviour in a script adds or updates a check in tests/ that fails without the change.

Tests

The behavioural tests live in tests/ and run offline; they need bash, git, find, grep and python3:

bash tests/verify-ckeditor5.sh      # skills/typo3-ckeditor5/scripts/verify-ckeditor5.sh
bash tests/check-plugin-version.sh  # Build/Scripts/check-plugin-version.sh and Build/hooks/pre-push

tests/verify-ckeditor5.sh builds fixture extension directories (empty, complete, with empty configuration directories, with a weak preset and plugin, with CKEditor 4 remnants, with four warnings to pin the significant-warnings threshold, with a file name containing a space) and checks the verifier's exit code, that every section runs, the individual findings and the exact warning count.
tests/check-plugin-version.sh builds throwaway git repositories and checks that a semver tag at HEAD must match the version in .claude-plugin/plugin.json, and that the pre-push hook passes the result on.

Each check prints ok or FAIL; a FAIL line names the expectation that was not met and is followed by the script's output. A test file exits 1 when any check failed. In CI, the Skill Tests workflow (.github/workflows/tests.yml) runs every tests/**/*.sh on each pull request and on pushes to main, and fails when the repository ships scripts under skills/*/scripts/ but no test ran.

The skill's Markdown is not executed. Skill Validation checks its structure, and Eval Validation checks the eval definitions in evals/evals.json. evals/run-ab-test.sh, which runs those evals against a model through the claude CLI, costs money per run and is not run in CI. pre-commit run --all-files runs the hooks of .pre-commit-config.yaml locally.

Dependencies

Composer: composer.json requires netresearch/composer-agent-skill-plugin (*, the latest release at install time), which installs the skill into a PHP project. No composer.lock is committed (.gitignore).
Scripts: verify-ckeditor5.sh needs bash, find, grep, wc and basename; check-plugin-version.sh needs git and python3. Nothing is installed by them.
Development tools: the hooks in .pre-commit-config.yaml are pinned by rev:. Renovate (renovate.json, config:recommended with the pre-commit manager enabled) proposes updates for them. The Composer requirement has no version range and no lock file, so there is nothing for it to update.
CI: the workflows call reusable workflows of netresearch/.github, netresearch/skill-repo-skill and netresearch/typo3-ci-workflows; those reusables pin the actions they use by commit SHA.

Governance and policies

This repository follows the Netresearch organisation policies:

Governance: ownership, roles, how decisions are made and disputes resolved, and continuity.
Roadmap: planned and explicitly excluded work for the coming year.
Handling of dependency and code analysis findings: thresholds, deadlines and the exception process for dependency (SCA) and static analysis (SAST) findings.
Secret management: how CI and release credentials are stored, accessed and rotated.
Access roster: who holds administrative access to this repository and the organisation.

The security assurance case for this skill (threat model, trust boundaries, countermeasures and limits) is in docs/SECURITY-ASSURANCE.md.

Checks that run on pull requests in this repository:

Every pull request: Skill Validation (lint.yml: skill structure, markdownlint, yamllint, actionlint, JSON syntax, ShellCheck, ruff, checkpoint schema), Eval Validation (eval-validate.yml) and Skill Tests (tests.yml).
Pull requests to main: security.yml with Betterleaks (secret scanning), zizmor (workflow static analysis), dependency review (fails on vulnerabilities of severity high or above), Composer Audit and Opengrep SAST (findings handled under the organisation's static analysis rule); Harness Verification (harness-verify.yml) and Template Drift (check-template-drift.yml).
Every pull request, from the template workflows: Labeler (labeler.yml) and the dependency auto-merge job (auto-merge-deps.yml, skipped unless a dependency bot opened the pull request).
Configured outside the workflows: CodeQL (GitHub default setup), SonarCloud code analysis, the DCO sign-off check, Copilot code review (a repository ruleset), CodeRabbit review, and GitHub secret scanning with push protection.

License

This project uses split licensing:

Code (scripts, workflows, configs): MIT
Content (skill definitions, documentation, references): CC-BY-SA-4.0

See the individual license files for full terms.

Credits

Developed and maintained by Netresearch DTT GmbH.

Made with ❤️ for Open Source by Netresearch

netresearch / agent-typo3-ckeditor5

Package info

Security

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