fix: Found the secret sauce!

packages/nuqs/src/adapters/next/impl.pages.ts

@@ -1,6 +1,6 @@
-import { useSearchParams } from 'next/navigation.js'
+import { useRouter } from 'next/compat/router'
 import type { NextRouter } from 'next/router'
-import { useCallback } from 'react'
+import { useCallback, useMemo } from 'react'
 import { debug } from '../../debug'
 import { createAdapterProvider } from '../lib/context'
 import type { AdapterInterface, UpdateUrlFunction } from '../lib/defs'
@@ -23,7 +23,24 @@ export function isPagesRouter(): boolean {
 }
 
 export function useNuqsNextPagesRouterAdapter(): AdapterInterface {
-  const searchParams = useSearchParams()
+  const router = useRouter()
+  const searchParams = useMemo(() => {
+    const searchParams = new URLSearchParams()
+    if (router === null) {
+      return searchParams
+    }
+    for (const [key, value] of Object.entries(router.query)) {
+      if (typeof value === 'string') {
+        searchParams.set(key, value)
+      } else if (Array.isArray(value)) {
+        for (const v of value) {
+          searchParams.append(key, v)
+        }
+      }
+    }
+    return searchParams
+  }, [JSON.stringify(router?.query)])
+
   const updateUrl: UpdateUrlFunction = useCallback((search, options) => {
     // While the Next.js team doesn't recommend using internals like this,
     // we need access to the pages router here to let it know about non-shallow
@@ -32,21 +49,77 @@ export function useNuqsNextPagesRouterAdapter(): AdapterInterface {
     // The router adapter imported from next/navigation also doesn't support
     // passing an asPath, causing issues in dynamic routes in the pages router.
     const nextRouter = window.next?.router!
-    const url = renderURL(nextRouter.state.asPath.split('?')[0] ?? '', search)
-    debug('[nuqs queue (pages)] Updating url: %s', url)
+    const urlParams = extractDynamicUrlParams(
+      nextRouter.pathname,
+      nextRouter.query
+    )
+    const query = Object.fromEntries(search.entries())
+    const asPath = renderURL(
+      nextRouter.state.asPath.split('?')[0] ?? '',
+      search
+    )
+    debug('[nuqs queue (pages)] Updating url: %s', asPath)
     const method =
       options.history === 'push' ? nextRouter.push : nextRouter.replace
-    method.call(nextRouter, url, url, {
-      scroll: options.scroll,
-      shallow: options.shallow
-    })
+
+    method.call(
+      nextRouter,
+      {
+        pathname: nextRouter.pathname,
+        query: {
+          ...urlParams,
+          ...query
+        },
+        hash: location.hash
+      },
+      {
+        pathname: nextRouter.state.asPath.split('?')[0] ?? '',
+        query,
+        hash: location.hash
+      },
+      {
+        scroll: options.scroll,
+        shallow: options.shallow
+      }
+    )
   }, [])
   return {
     searchParams,
     updateUrl,
     // See: https://github.com/47ng/nuqs/issues/603#issuecomment-2317057128
-    rateLimitFactor: 2
+    rateLimitFactor: 1
   }
 }
 
 export const NuqsAdapter = createAdapterProvider(useNuqsNextPagesRouterAdapter)
+
+function extractDynamicUrlParams(
+  pathname: string,
+  values: Record<string, string | string[] | undefined>
+): Record<string, string | string[] | undefined> {
+  const paramNames = new Set<string>()
+  const dynamicRegex = /\[([^\]]+)\]/g
+  const catchAllRegex = /\[\.{3}([^\]]+)\]$/
+  const optionalCatchAllRegex = /\[\[\.{3}([^\]]+)\]\]$/
+
+  let match
+  while ((match = dynamicRegex.exec(pathname)) !== null) {
+    const paramName = match[1]
+    if (paramName) {
+      paramNames.add(paramName)
+    }
+  }
+  const dynamicValues = Object.fromEntries(
+    Object.entries(values).filter(([key]) => paramNames.has(key))
+  )
+  const matchCatchAll = catchAllRegex.exec(pathname)
+  const matchOptionalCatchAll = optionalCatchAllRegex.exec(pathname)
+  if (matchCatchAll) {
+    dynamicValues[matchCatchAll[1]!] = values[matchCatchAll[1]!] ?? []
+  }
+  if (matchOptionalCatchAll) {
+    dynamicValues[matchOptionalCatchAll[1]!] =
+      values[matchOptionalCatchAll[1]!] ?? []
+  }
+  return dynamicValues
+}