Generation 3 release hardening
This document records compatibility guarantees tightened during the Generation 3 release audit.
Server-first parity
Server-first compilation is an execution optimization, not a separate visual API. Static/server primitives now use the same deterministic style compiler as the compatibility/client renderer, including responsive properties, CSS passthrough values, nested at-rules, cprop states, and primitive style precedence.
Slot fallbacks are compiled as real schema branches so their runtime, assets, capabilities, security diagnostics, and client-island requirements remain part of the page plan.
See server-first-parity.md for the detailed contract.
Artifact cache safety
Generation 3 artifact fingerprints distinguish function object identity. Different closures with identical source text therefore cannot reuse a compiled artifact containing stale closure or request state. Reusing the same function object remains cacheable.
Next.js image qualities
EngineImage uses these built-in quality presets:
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When the combined withEngine() plugin is used, it preserves application-provided images.qualities and adds 65, 75, 78, and 90. 75 is retained for normal Next.js image compatibility while the other values cover every built-in EngineImage preset.
An application that supplies an explicit custom quality, qualityMobile, or qualityDesktop outside those values should also include that value in its own Next.js images.qualities configuration.
Regression coverage
The main Generation 3 CI verifies server-first parity, artifact-cache function isolation, EngineImage quality configuration, TypeScript validation, the optimized Next.js integration build, production-only bundle/security proofs, and the browser/device matrix.