typo3-v11-to-v12-upgrade

TYPO3 v11 to v12 Upgrade

Use this skill to analyze, plan, and execute a TYPO3 11.5 to TYPO3 12.4 LTS upgrade in Composer-based projects. Treat the upgrade as a staged change: stabilize TYPO3 11 first, remove blockers, then upgrade Composer constraints and migrate code/configuration in small steps.

Required Start

1. Check Repositories: Read the repository's AGENTS.md and follow it. If it requires SequentialThinking, DDEV, Context7, Rector, Fractor, or browser checks, apply those rules before editing.
2. Fetch Docs: Fetch current documentation before making version-specific claims. Resolve/query TYPO3 docs via Context7, and prefer official TYPO3 docs, get.typo3.org, TYPO3 Core changelogs, and package vendor docs.
3. Environment check: Confirm the project is not production. Major upgrades should run locally, in DDEV, or on a parallel copy with database and file backups.
4. Git Branch: Create or confirm a dedicated branch before making upgrade edits. Do not run destructive Git commands.
5. Support status: TYPO3 v12 reached regular end of life on 2026-04-30. If upgrading after that date, call out whether v12 is an interim step toward v13/v14 or requires ELTS.

Operating Modes

If not specified, start with analyze, then ask before executing.

• analyze: Inventory versions, extensions, Composer blockers, deprecations, and risks. Do not change code.
• plan: Produce a detailed migration plan with phases, commands, risks, rollback points, and acceptance criteria using the plan template.
• execute: Perform the upgrade incrementally. Run dry-runs first, inspect diffs, and verify after every phase.

Reference Materials

Use the following detailed resources located in this skill:

• Command Reference: references/command-reference.md (All execution commands, scans, and verification tasks)
• Change Hotspots: references/v12-change-hotspots.md (Platform requirements, Doctrine DBAL 3, CKEditor 5, TypoScript parser, TCA, FlexForms, and Hooks/Events)
• Plan Template: references/plan-template.md (Checklists, planning output formats, and completion reports)