fix: Vercel serverless function crash and await async completions routes

- Make generateDeviceFingerprint resilient to os.cpus() and os.hostname() returning empty or throwing in lambda sandboxes.
- Await async handleChatCompletion and handleAnthropicMessages calls in route handlers to prevent unhandled promise rejections.
- Catch runtime exceptions from completions and return clean HTTP 500 JSON error responses.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/mimo-auth.ts

@@ -34,11 +34,26 @@ const EXPIRY_BUFFER_MS = 300_000; // 5 minutes
  * Uses Web Crypto API (available in Bun, Workers, and Node.js 20+).
  */
 async function generateDeviceFingerprint(): Promise<string> {
-  const hostname = os.hostname();
-  const platform = process.platform;
-  const arch = process.arch;
-  const cpus = os.cpus();
-  const cpuModel = cpus.length > 0 ? (cpus[0]?.model ?? "unknown") : "unknown";
+  let hostname = "unknown";
+  try {
+    hostname = os.hostname() ?? "unknown";
+  } catch {
+    // OS module hostname not available in this sandbox
+  }
+
+  const platform = process.platform ?? "unknown";
+  const arch = process.arch ?? "unknown";
+
+  let cpuModel = "unknown";
+  try {
+    const cpus = os.cpus();
+    if (cpus && cpus.length > 0) {
+      cpuModel = cpus[0]?.model ?? "unknown";
+    }
+  } catch {
+    // OS module cpus not available in this sandbox
+  }
+
   const username = process.env.USER ?? process.env.USERNAME ?? "unknown";
 
   const raw = `${hostname}|${platform}|${arch}|${cpuModel}|${username}`;

src/lib/router.ts

@@ -9,7 +9,6 @@ import {
 	createErrorResponse,
 	createCorsPreflightResponse,
 	getCorsHeaders,
-	classifyFetchError,
 } from "./relay-utils";
 
 import { checkBodySize } from "../middleware/body-limiter";
@@ -615,11 +614,18 @@ export async function handleRequest(
 		try {
 			const body = await req.json();
 			const sessionId = crypto.randomUUID();
-			return handleChatCompletion(body, proxyPool!, sessionPool!, sessionId);
-		} catch {
+			return await handleChatCompletion(body, proxyPool!, sessionPool!, sessionId);
+		} catch (err) {
+			const isJsonError = err instanceof Error && (err.name === "SyntaxError" || err.message.includes("JSON"));
+			if (isJsonError) {
+				return new Response(
+					JSON.stringify({ error: { message: "Invalid JSON body", type: "invalid_request_error" } }),
+					{ status: 400, headers: { "Content-Type": "application/json", ...getCorsHeaders() } },
+				);
+			}
 			return new Response(
-				JSON.stringify({ error: { message: "Invalid JSON body", type: "invalid_request_error" } }),
-				{ status: 400, headers: { "Content-Type": "application/json", ...getCorsHeaders() } },
+				JSON.stringify({ error: { message: err instanceof Error ? err.message : "Internal Server Error", type: "server_error" } }),
+				{ status: 500, headers: { "Content-Type": "application/json", ...getCorsHeaders() } },
 			);
 		}
 	}
@@ -634,14 +640,24 @@ export async function handleRequest(
 			const body = await req.json();
 			const sessionId = crypto.randomUUID();
 			const anthropicVersion = req.headers.get("anthropic-version") ?? undefined;
-			return handleAnthropicMessages(body, proxyPool!, sessionPool!, sessionId, undefined, anthropicVersion);
-		} catch {
+			return await handleAnthropicMessages(body, proxyPool!, sessionPool!, sessionId, undefined, anthropicVersion);
+		} catch (err) {
+			const isJsonError = err instanceof Error && (err.name === "SyntaxError" || err.message.includes("JSON"));
+			if (isJsonError) {
+				return new Response(
+					JSON.stringify({
+						type: "error",
+						error: { message: "Invalid JSON body", type: "invalid_request_error" },
+					}),
+					{ status: 400, headers: { "Content-Type": "application/json", ...getCorsHeaders() } },
+				);
+			}
 			return new Response(
 				JSON.stringify({
 					type: "error",
-					error: { message: "Invalid JSON body", type: "invalid_request_error" },
+					error: { message: err instanceof Error ? err.message : "Internal Server Error", type: "server_error" },
 				}),
-				{ status: 400, headers: { "Content-Type": "application/json", ...getCorsHeaders() } },
+				{ status: 500, headers: { "Content-Type": "application/json", ...getCorsHeaders() } },
 			);
 		}
 	}