fix(ai-gateway): fall back to default when routing override is cleared (#2790)

* fix(ai-gateway): fall back to default when routing override is cleared

When an admin clears the Vercel routing override the admin router
persists `{vercel_routing_percentage: null, ...}` to Redis. The hot
path parsed that with a non-nullable schema and threw; `createCachedFetch`
then kept serving the last cached numeric value, so a worker that had
cached a non-null override would never pick up the intended default.

Accept `null` in `GatewayPercentageSchema` and treat it as 'use
`DEFAULT_VERCEL_PERCENTAGE`' in the fetcher.

* refactor: move gateway-config into ai-gateway folder

* style: wrap long import after rename

---------

Co-authored-by: kiloconnect[bot] <240665456+kiloconnect[bot]@users.noreply.github.com>

Author: kilo-code-bot[bot]

apps/web/src/app/admin/gateway/RoutingContent.tsx

@@ -7,7 +7,7 @@ import { toast } from 'sonner';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card';
-import { DEFAULT_VERCEL_PERCENTAGE } from '@/lib/gateway-config';
+import { DEFAULT_VERCEL_PERCENTAGE } from '@/lib/ai-gateway/gateway-config';
 
 export function RoutingContent() {
   const trpc = useTRPC();

apps/web/src/lib/ai-gateway/gateway-config.test.ts

@@ -0,0 +1,21 @@
+import { describe, test, expect } from '@jest/globals';
+import { GatewayPercentageSchema } from './gateway-config';
+
+describe('GatewayPercentageSchema', () => {
+  test('accepts a numeric percentage', () => {
+    expect(GatewayPercentageSchema.parse({ vercel_routing_percentage: 25 })).toEqual({
+      vercel_routing_percentage: 25,
+    });
+  });
+
+  test('accepts null (written when an admin clears the override)', () => {
+    expect(GatewayPercentageSchema.parse({ vercel_routing_percentage: null })).toEqual({
+      vercel_routing_percentage: null,
+    });
+  });
+
+  test('rejects out-of-range values', () => {
+    expect(() => GatewayPercentageSchema.parse({ vercel_routing_percentage: 101 })).toThrow();
+    expect(() => GatewayPercentageSchema.parse({ vercel_routing_percentage: -1 })).toThrow();
+  });
+});

apps/web/src/lib/gateway-config.ts …web/src/lib/ai-gateway/gateway-config.tsapps/web/src/lib/gateway-config.ts renamed to apps/web/src/lib/ai-gateway/gateway-config.ts apps/web/src/lib/gateway-config.ts renamed to apps/web/src/lib/ai-gateway/gateway-config.ts

@@ -20,9 +20,15 @@ export const DEFAULT_GATEWAY_CONFIG: GatewayConfig = {
   updated_by_email: null,
 };
 
-/** Schema for parsing just the percentage from Redis (used on the hot path). */
+/**
+ * Schema for parsing just the percentage from Redis (used on the hot path).
+ *
+ * `vercel_routing_percentage` is nullable because clearing the override in
+ * the admin UI persists an explicit `null`. Callers should treat `null` as
+ * "no override, use DEFAULT_VERCEL_PERCENTAGE".
+ */
 export const GatewayPercentageSchema = z.object({
-  vercel_routing_percentage: vercelRoutingPercentage,
+  vercel_routing_percentage: vercelRoutingPercentage.nullable(),
 });
 
 /** Schema for the admin set-mutation input. */

apps/web/src/lib/ai-gateway/providers/vercel/index.ts

@@ -16,15 +16,20 @@ import { isReasoningExplicitlyDisabled } from '@/lib/ai-gateway/providers/openro
 import { mapModelIdToVercel } from '@/lib/ai-gateway/providers/vercel/mapModelIdToVercel';
 import { redisGet } from '@/lib/redis';
 import { createCachedFetch } from '@/lib/cached-fetch';
-import { GatewayPercentageSchema, DEFAULT_VERCEL_PERCENTAGE } from '@/lib/gateway-config';
+import {
+  GatewayPercentageSchema,
+  DEFAULT_VERCEL_PERCENTAGE,
+} from '@/lib/ai-gateway/gateway-config';
 import { VERCEL_ROUTING_REDIS_KEY } from '@/lib/redis-keys';
 import { getRandomNumber } from '@/lib/ai-gateway/getRandomNumber';
 import { getVercelModels } from '@/lib/ai-gateway/providers/gateway-models-cache';
 
 const getVercelRoutingPercentage = createCachedFetch(
   async () => {
     const raw = await redisGet(VERCEL_ROUTING_REDIS_KEY);
-    return GatewayPercentageSchema.parse(JSON.parse(raw ?? 'null')).vercel_routing_percentage;
+    if (!raw) return DEFAULT_VERCEL_PERCENTAGE;
+    const { vercel_routing_percentage } = GatewayPercentageSchema.parse(JSON.parse(raw));
+    return vercel_routing_percentage ?? DEFAULT_VERCEL_PERCENTAGE;
   },
   10_000,
   DEFAULT_VERCEL_PERCENTAGE

apps/web/src/routers/admin/gateway-config-router.ts

@@ -4,9 +4,9 @@ import {
   GatewayConfigSchema,
   GatewayConfigInputSchema,
   DEFAULT_GATEWAY_CONFIG,
-} from '@/lib/gateway-config';
+} from '@/lib/ai-gateway/gateway-config';
 import { VERCEL_ROUTING_REDIS_KEY } from '@/lib/redis-keys';
-import type { GatewayConfig } from '@/lib/gateway-config';
+import type { GatewayConfig } from '@/lib/ai-gateway/gateway-config';
 import { TRPCError } from '@trpc/server';
 
 async function readConfig(): Promise<GatewayConfig> {