0.29.7

docs/WEB_SERVER.md

@@ -35,6 +35,44 @@ The Web Service editor is split into stable configuration tabs so later features
 
 After the Web Service is saved, attach it under **Vhosts** by selecting `Web Server` and the service ID for the main source or a custom location.
 
+### Intercept application HTTP errors (0.29.7)
+
+Open **Vhosts → Edit vhost → Pages** (not the Web Service PHP tab), enable
+**Intercept application error responses**, and enter statuses such as `404, 500, 503`.
+This opt-in vhost policy applies to response bodies returned by both **Reverse
+Proxy origins** and **Web Server/PHP-FPM origins**. It is configured in
+`vhosts[].pages.intercept_statuses`; an omitted/empty list disables it and
+preserves the application error HTML. Supported codes: 400, 401, 403, 404,
+408, 413, 429, 500, 502, 503, 504.
+
+For each opted-in origin status, RustProxy replaces the *body* using the
+vhost's configured error page, then the global error page, then its built-in
+error page. The HTTP response status always remains the application's status,
+even if the selected page has a custom `status` for standalone error handling.
+`Cache-Control: no-store` is set and origin response cookies, compression
+metadata and application error HTML are not forwarded. Relevant protocol
+headers such as `WWW-Authenticate`, `Allow` and `Retry-After` are retained.
+Local RustProxy security/routing failures are not treated as application
+responses. If `error_fallback` sends an error to a named internal location,
+that response takes precedence and is not overwritten by this option.
+
+```json
+{
+  "id": "my-vhost",
+  "pages": {
+    "intercept_statuses": [404, 500, 503],
+    "errors": {
+      "404": {"kind": "html", "status": null, "html": "<h1>Not found</h1>"}
+    }
+  }
+}
+```
+
+This is a **vhost fragment**, not a standalone valid vhost object. A page's
+`status` override still applies to locally generated RustProxy error pages,
+but is ignored when replacing an application's error body. See also
+[Custom locations](CUSTOM_LOCATIONS.md).
+
 ### Application presets
 
 The editor provides one-shot presets for **Static site, SPA, PHP generic, WordPress, Drupal, Laravel, Symfony, Joomla, PrestaShop and Downloads/file repository**. Applying a preset writes normal Web Service fields; it does not store a hidden CMS mode and every generated field remains editable. Service ID/name, document root and the deployment-specific PHP-FPM endpoint/tuning are preserved. Laravel/Symfony operators should point `document_root` at the application's `public/` directory.