Context

Follow-up from review of #1788 (searchParams static-bailout via access observation).

Problem

buildAppPageProbes (packages/vinext/src/server/app-page-probe.ts) probes every declared slot's page.default, including slots that are inactive for the current request.

At render time, a parallel-route slot with both page.tsx and default.tsx may render default (or have its page replaced by an interception override — see app-page-route-wiring.tsx slot resolution around the overrideOrPageComponent ?? defaultComponent logic). But the probe unconditionally invokes slot.page.default.

A route whose inactive @modal/page.tsx awaits searchParams therefore marks the whole request dynamic on a request where that page never renders, defeating static caching for an otherwise-static page.

Severity

This fails safe (toward dynamic — it never serves a stale query-bearing response), so it is a caching-efficiency regression, not a correctness/security issue.

Fix direction

Narrow the slot fan-out so only the slot pages that will actually render for the request are probed. This requires mirroring the render-time active-slot resolution (slot overrides from interception, mounted-slot state) which is currently computed in app-page-route-wiring.tsx and not readily available at probe time in the RSC entry. Extracting/sharing that active-slot resolution would let the probe and the render path agree on which slot components run.