Index: wp-includes/classes.php
===================================================================
--- wp-includes/classes.php	(revision 10485)
+++ wp-includes/classes.php	(working copy)
@@ -194,11 +194,17 @@
 
 			$this->request = $request;
 
+			// Remove 'posts' from wp-app requests
+			if ($req_uri == 'wp-app.php' && substr($request, 0, 6) === 'posts/') {
+				$request = substr($request, 6);
+				$match_app_requests = true;
+			}
+			
 			// Look for matches.
 			$request_match = $request;
 			foreach ( (array) $rewrite as $match => $query) {
-				// Don't try to match against AtomPub calls
-				if ( $req_uri == 'wp-app.php' )
+				// Don't try to match against some AtomPub calls
+				if ( $req_uri == 'wp-app.php' && empty($match_app_requests) )
 					break;
 
 				// If the requesting file is the anchor of the match, prepend it