Summary & Key Takeaways ​

• New @solidjs/diagnostics package provides a harness for dev-mode diagnostics and attribution.
• captureArtifact() runs scenarios with open diagnostic channels, folding results into serializable artifacts.
• Assertion helpers like expectNoDiagnostics and expectRerunBudget gate correctness and update granularity.
• Vitest matchers are available via @solidjs/diagnostics/vitest for integrated testing.
• Browser and Playwright adapters enable artifact capture from real pages with live queries.
• A skills/reactivity-diagnostics repair guide maps diagnostic codes to fixes.

Our Commentary ​

This is a huge win for SolidJS developers. Debugging reactivity graphs can be notoriously tricky, and a dedicated diagnostics package with assertion helpers and browser integration feels like a game-changer. We've seen similar tools in other ecosystems, but Solid's approach here looks incredibly thorough. I'm genuinely excited to see how this improves the developer experience.