feat(app-router): enable type-aware parameter tracking and resolve parallel route param inconsistencies

Removes special-case filtering for parallel route parameters that caused
inconsistent behavior and adds explicit parameter type tracking throughout
the routing system. This enables more predictable parameter resolution
and provides foundation for advanced parameter handling features.

Key improvements:
- Add DynamicParamTypes to track parameter semantics
- Introduce resolveParallelRouteParams for consistent param handling
- Remove parallel route exclusion logic from build pipeline
- Enhance FallbackRouteParam with type information

Author: wyattjoh

packages/next/errors.json

@@ -782,7 +782,6 @@
   "781": "No LRU node to remove",
   "782": "Failed to find the root directory of the project. This is a bug in Next.js.",
   "783": "\\`experimental.clientParamParsing\\` can not be \\`true\\` when \\`experimental.clientSegmentCache\\` is \\`false\\`. Client param parsing is only relevant when client segment cache is enabled.",
-  "784": "Unexpected dynamic param type: %s",
-  "785": "Expected RSC response, got %s",
-  "786": "Invariant: Expected RSC response, got %s"
+  "784": "Expected RSC response, got %s",
+  "785": "Unexpected dynamic param type: %s"
 }

packages/next/src/build/index.ts

@@ -3134,12 +3134,7 @@ export default async function build(
             for (const prerenderedRoute of prerenderedRoutes) {
               if (
                 prerenderedRoute.fallbackRouteParams &&
-                prerenderedRoute.fallbackRouteParams.length > 0 &&
-                // If all the fallback route params are parallel route params,
-                // then we still consider it a known route.
-                !prerenderedRoute.fallbackRouteParams.every(
-                  (param) => param.isParallelRouteParam
-                )
+                prerenderedRoute.fallbackRouteParams.length > 0
               ) {
                 unsortedUnknownPrerenderRoutes.push(prerenderedRoute)
               } else {
@@ -3165,12 +3160,7 @@ export default async function build(
               if (
                 isRoutePPREnabled &&
                 prerenderedRoute.fallbackRouteParams &&
-                prerenderedRoute.fallbackRouteParams.length > 0 &&
-                // If all the fallback route params are parallel route params,
-                // then we still consider it a static route.
-                !prerenderedRoute.fallbackRouteParams.every(
-                  (param) => param.isParallelRouteParam
-                )
+                prerenderedRoute.fallbackRouteParams.length > 0
               ) {
                 // If the route has unknown params, then we need to add it to
                 // the list of dynamic routes.
@@ -3478,14 +3468,7 @@ export default async function build(
                     : undefined,
                   fallbackSourceRoute:
                     route.fallbackRouteParams &&
-                    route.fallbackRouteParams.length > 0 &&
-                    // If all the fallback route params are parallel route
-                    // params, then we still consider it a static route. This is
-                    // required to ensure that the changes are backwards
-                    // compatible with the previous builder implementations.
-                    !route.fallbackRouteParams.every(
-                      (param) => param.isParallelRouteParam
-                    )
+                    route.fallbackRouteParams.length > 0
                       ? page
                       : undefined,
                   fallbackRouteParams: route.fallbackRouteParams,

packages/next/src/build/segment-config/app/app-segments.ts

@@ -20,6 +20,7 @@ import {
 import { PAGE_SEGMENT_KEY } from '../../../shared/lib/segment'
 import type { FallbackRouteParam } from '../../static-paths/types'
 import { createFallbackRouteParam } from '../../static-paths/utils'
+import type { DynamicParamTypes } from '../../../shared/lib/app-router-types'
 
 type GenerateStaticParams = (options: { params?: Params }) => Promise<Params[]>
 
@@ -59,6 +60,7 @@ function attach(segment: AppSegment, userland: unknown, route: string) {
 export type AppSegment = {
   name: string
   paramName: string | undefined
+  paramType: DynamicParamTypes | undefined
   filePath: string | undefined
   config: AppSegmentConfig | undefined
   isDynamicSegment: boolean
@@ -98,11 +100,12 @@ async function collectAppPageSegments(routeModule: AppPageRouteModule) {
     const { mod: userland, filePath } = await getLayoutOrPageModule(loaderTree)
     const isClientComponent = userland && isClientReference(userland)
 
-    const paramName = getSegmentParam(name)?.param
+    const { param: paramName, type: paramType } = getSegmentParam(name) ?? {}
 
     const segment: AppSegment = {
       name,
       paramName,
+      paramType,
       filePath,
       config: undefined,
       isDynamicSegment: !!paramName,
@@ -169,11 +172,12 @@ function collectAppRouteSegments(
 
   // Generate all the segments.
   const segments: AppSegment[] = parts.map((name) => {
-    const paramName = getSegmentParam(name)?.param
+    const { param: paramName, type: paramType } = getSegmentParam(name) ?? {}
 
     return {
       name,
       paramName,
+      paramType,
       filePath: undefined,
       isDynamicSegment: !!paramName,
       config: undefined,
@@ -244,7 +248,11 @@ export function collectFallbackRouteParams(
       if (!uniqueSegments.has(key)) {
         uniqueSegments.set(
           key,
-          createFallbackRouteParam(segmentParam.param, isParallelRouteSegment)
+          createFallbackRouteParam(
+            segmentParam.param,
+            segmentParam.type,
+            isParallelRouteSegment
+          )
         )
       }
     }