Augment system prompt with date and user location (default SF)

server/src/routes.ts

@@ -48,6 +48,43 @@ function isToolCallLogMessage(message: { role: string; metadata: unknown }) {
   return message.role === "tool" && isToolCallLogMetadata(message.metadata);
 }
 
+function getHeaderString(req: FastifyRequest, name: string) {
+  const value = req.headers[name.toLowerCase()];
+  if (Array.isArray(value)) return value.find((item) => item.trim());
+  return typeof value === "string" && value.trim() ? value : undefined;
+}
+
+function decodeHeaderPart(value: string | undefined) {
+  if (!value) return undefined;
+  const trimmed = value.trim();
+  if (!trimmed) return undefined;
+  try {
+    return decodeURIComponent(trimmed);
+  } catch {
+    return trimmed;
+  }
+}
+
+function inferRequestUserLocation(req: FastifyRequest) {
+  const explicit = decodeHeaderPart(getHeaderString(req, "x-user-location"));
+  if (explicit) return explicit;
+
+  const vercelCity = decodeHeaderPart(getHeaderString(req, "x-vercel-ip-city"));
+  const vercelRegion = decodeHeaderPart(getHeaderString(req, "x-vercel-ip-country-region"));
+  const vercelCountry = decodeHeaderPart(getHeaderString(req, "x-vercel-ip-country"));
+  const vercelLocation = [vercelCity, vercelRegion, vercelCountry].filter(Boolean).join(", ");
+  if (vercelLocation) return vercelLocation;
+
+  const cfCity = decodeHeaderPart(getHeaderString(req, "cf-ipcity"));
+  const cfRegion = decodeHeaderPart(getHeaderString(req, "cf-region"));
+  const cfCountry = decodeHeaderPart(getHeaderString(req, "cf-ipcountry"));
+  return [cfCity, cfRegion, cfCountry].filter(Boolean).join(", ") || undefined;
+}
+
+function withRequestUserLocation<T extends { userLocation?: string }>(body: T, req: FastifyRequest): T {
+  return body.userLocation ? body : { ...body, userLocation: inferRequestUserLocation(req) };
+}
+
 async function storeNonAssistantMessages(chatId: string, messages: IncomingChatMessage[]) {
   const incoming = messages.filter((m) => m.role !== "assistant");
   if (!incoming.length) return;
@@ -132,6 +169,7 @@ const CompletionStreamBody = z
     provider: ProviderSchema,
     model: z.string().min(1),
     messages: z.array(CompletionMessageSchema),
+    userLocation: z.string().trim().min(1).max(200).optional(),
     temperature: z.number().min(0).max(2).optional(),
     maxTokens: z.number().int().positive().optional(),
   })
@@ -1211,13 +1249,14 @@ export async function registerRoutes(app: FastifyInstance) {
       provider: ProviderSchema,
       model: z.string().min(1),
       messages: z.array(CompletionMessageSchema),
+      userLocation: z.string().trim().min(1).max(200).optional(),
       temperature: z.number().min(0).max(2).optional(),
       maxTokens: z.number().int().positive().optional(),
     });
 
     const parsed = Body.safeParse(req.body);
     if (!parsed.success) return app.httpErrors.badRequest(parsed.error.message);
-    const body = parsed.data;
+    const body = withRequestUserLocation(parsed.data, req);
 
     // ensure chat exists if provided
     if (body.chatId) {
@@ -1244,7 +1283,7 @@ export async function registerRoutes(app: FastifyInstance) {
 
     const parsed = CompletionStreamBody.safeParse(req.body);
     if (!parsed.success) return app.httpErrors.badRequest(parsed.error.message);
-    const body = parsed.data;
+    const body = withRequestUserLocation(parsed.data, req);
 
     // ensure chat exists if provided
     if (body.chatId) {