docs: clarify route pathname normalization

Author: Prayaksh

src/content/docs/en/guides/upgrade-to/v6.mdx

@@ -832,13 +832,16 @@ If you have route files with `%25` in the filename, rename them to use a differe
 src/pages/test%25file.astro
 src/pages/test-file.astro
 ```
-Astro v6 also changed how URLs and route parameters are handled at runtime.
+## Changed: Route pathname normalization
 
-`Astro.url` returns a normalized and partially decoded URL, so it may differ from `new URL(Astro.request.url)`.
+Since Astro v6, route pathnames are partially decoded during route normalization. This means `Astro.url.pathname` may differ from `new URL(Astro.request.url).pathname` for percent-encoded route segments.
 
-`Astro.params` values are automatically decoded, and percent-encoded characters in pathnames or parameters (like `%25`) may appear decoded in `Astro.url` or `Astro.params`.
+This also affects route params derived from normalized pathnames.
+
+### What should I do?
+
+If you need access to the original encoded pathname, use `new URL(Astro.request.url).pathname` instead of `Astro.url.pathname`.
 
-If you need the raw request URL with no decoding, use `Astro.request.url` and parse it manually.
 
 ### Removed: `astro:ssr-manifest` virtual module (Integration API)
 

src/content/docs/en/reference/api-reference.mdx

@@ -137,8 +137,6 @@ In static builds, this will be the `params` returned by `getStaticPaths()` used
 
 When routes are rendered on demand, `params` can be any value matching the path segments in the dynamic route pattern.
 
-`params` values are automatically decoded from route pathnames.
-
 ```astro title="src/pages/posts/[id].astro" "Astro.params"
 ---
 import { getPost } from '../api';
@@ -165,11 +163,9 @@ See also: [`params`](/en/reference/routing-reference/#params)
 <Since v="1.0.0" />
 </p>
 
-`url` is a [URL](https://developer.mozilla.org/en-US/docs/Web/API/URL) object constructed from the current `request.url` value. It is useful for interacting with individual properties of the request URL, like pathname and origin. 
-
-`Astro.url` is a normalized `URL` instance derived from `Astro.request.url`.
+A normalized [URL](https://developer.mozilla.org/en-US/docs/Web/API/URL) object derived from the current `request.url` value. It is useful for interacting with individual properties of the request URL, like pathname and origin. 
 
-In Astro v6, the pathname is partially decoded during route normalization, so `Astro.url.pathname` may differ from `new URL(Astro.request.url).pathname` for percent-encoded route segments.
+Since Astro v6, the pathname is partially decoded during route normalization. This means `Astro.url.pathname` may differ from `new URL(Astro.request.url).pathname` for percent-encoded route segments.
 
 `url` will be a `localhost` URL in dev mode. When building a site, prerendered routes will receive a URL based on the [`site`](/en/reference/configuration-reference/#site) and [`base`](/en/reference/configuration-reference/#base) options. If `site` is not configured, prerendered pages will receive a `localhost` URL during builds as well.
 

src/content/docs/en/reference/configuration-reference.mdx

@@ -517,6 +517,8 @@ In some specific contexts (e.g., applications behind trusted reverse proxies wit
 
 When not configured, `X-Forwarded-Host` headers are not trusted and will be ignored.
 
+When deploying behind reverse proxies or serverless platforms (for example Vercel), configure `allowedDomains` so Astro can safely trust forwarded host headers during origin validation.
+
 #### security.actionBodySizeLimit
 
 <p>