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# v0.5.20 — Skills, rewind, and a stronger agent harness

Released April 13, 2026

## Highlights

* Nine production-grade game-building skills (movement, combat, UI, and more)
* Rewind an individual assistant message when you want to back up one step
* Run-and-verify loop with heartbeats and raised timeouts for multi-step engine work
* Opus 4.7 on the free tier plus an expanded model lineup

## Changes

Added
* Skill library wired into orchestrator prompts for repeatable multi-step workflows
* Per-message Rewind with confirmation modal
* previewScene and SummerGit checkpoint tools in the harness
* Plan files and updateTodos verify-gate for structured agent tasks
* summer/skills knowledge pattern for composing tools across a turn
* Template import via download + tar extract; enableGodotPlugin helper for fresh projects

Improved
* runAndVerify: three-attempt retry loop with progress heartbeats
* 3D generation capabilities and in-chat documentation
* Chat model entitlements and routing for new providers
* Turn caps on tool calls and wall-clock time to keep long runs bounded

Fixed
* Reject Pending Changes renamed from Undo All, with a confirm dialog
* Bridge timeout diagnostics downgraded to warnings where appropriate

Source: https://www.summerengine.com/changelog/0.5.20

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## Machine-readable resources

- Site index for agents: https://www.summerengine.com/llms.txt
- Full inlined content: https://www.summerengine.com/llms-full.txt
- Porting catalog: https://www.summerengine.com/llms-porting.txt
- Structured catalog: https://www.summerengine.com/agent-catalog.json
- Sitemap: https://www.summerengine.com/sitemap.xml
- Developer resources: https://www.summerengine.com/docs