support streaming and closes properly on site targets

server/lib/aiCapabilities.ts

@@ -62,9 +62,10 @@ export function joinUpstreamUrl(baseUrl: string, path: string): string {
 }
 
 function pathFromRequest(req: Request): string {
-    // Prefer originalUrl path (includes mounted path) over req.path when available.
-    const raw =
-        req.originalUrl?.split("?")[0] || req.url?.split("?")[0] || req.path;
+    // Prefer originalUrl (includes mounted path) over req.url when available.
+    // Query string is preserved - some providers use it to select the
+    // streaming response format (e.g. Gemini's `?alt=sse`).
+    const raw = req.originalUrl || req.url || req.path;
     return raw.startsWith("/") ? raw : `/${raw}`;
 }
 

server/lib/aiGatewayUpstreamFetch.ts

@@ -7,6 +7,7 @@ type UpstreamFetchInit = {
     headers: Record<string, string>;
     body?: string;
     skipTlsVerification?: boolean;
+    signal?: AbortSignal;
 };
 
 const insecureHttpsAgent = new https.Agent({
@@ -25,6 +26,11 @@ export function aiGatewayUpstreamFetch(
         isHttps && init.skipTlsVerification ? insecureHttpsAgent : undefined;
 
     return new Promise((resolve, reject) => {
+        if (init.signal?.aborted) {
+            reject(init.signal.reason ?? new Error("Request aborted"));
+            return;
+        }
+
         const req = lib.request(
             url,
             {
@@ -60,6 +66,14 @@ export function aiGatewayUpstreamFetch(
 
         req.on("error", reject);
 
+        if (init.signal) {
+            const onAbort = () => req.destroy(init.signal!.reason);
+            init.signal.addEventListener("abort", onAbort, { once: true });
+            req.on("close", () =>
+                init.signal!.removeEventListener("abort", onAbort)
+            );
+        }
+
         if (init.body !== undefined) {
             req.write(init.body);
         }