cloudflare/vinext

App Router: parallel route slots drop dynamic params (`catchAll`/`[...slug]`)

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#1,536 opened on May 22, 2026

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Description

This issue was created by an agent analysing CI failures from the Next.js Deploy Suite (vinext main vs Next.js v16.2.6, 2026-05-22).

Problem

Pages under a parallel slot with a catch-all dynamic segment receive a params object that omits the dynamic key entirely. The matched catchAll: ['sub','folder'] array is dropped both on initial SSR and on client navigations, leaving only the static keys.

Parallel slot's catchAll params key dropped from `params`

Estimated Impact

~2 test failures across the deploy suite.

Affected Test Suites

  • test/e2e/app-dir/parallel-route-navigations/parallel-route-navigations.test.ts (2 failures)

Recommendation

  1. Reproduce first in vinext's own test suite. Add a @slot/[...catchAll]/page.tsx and assert params.catchAll is populated on SSR and after client nav.

  2. Pass dynamic params through the parallel-slot resolver. When matching parallel slots, accumulate dynamic params from the slot path into params rather than only the children path.

Part of #1328.

Contributor guide

Research direction
Reproduce the issue in vinext's test suite with a parallel slot catch all route, then modify the parallel slot resolver to accumulate dynamic params from the slot path.
Tech stack
typescriptnextjs
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitTypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60