diff --git a/apps/server/src/provider/GrokProvider.test.ts b/apps/server/src/provider/GrokProvider.test.ts
index 9cc1a9a7e3238..9be799112cc23 100644
--- a/apps/server/src/provider/GrokProvider.test.ts
+++ b/apps/server/src/provider/GrokProvider.test.ts
@@ -722,6 +722,36 @@ it.layer(Layer.mergeAll(NodeServices.layer, NodeCrypto.layer))("readGrokAccount"
       }
     }),
   );
+
+  it.effect("tells accounts in Legacy (no storage) to switch to Privacy Mode", () =>
+    Effect.gen(function* () {
+      const { usageLimits: limits } = yield* readGrokAccount({
+        HOME: "/definitely/not/a/grok-home",
+        GROK_AUTH: '{"https://accounts.x.ai/sign-in":{"key":"private-token"}}',
+      }).pipe(
+        Effect.provideService(
+          HttpClient.HttpClient,
+          HttpClient.make((request) =>
+            Effect.succeed(
+              HttpClientResponse.fromWeb(
+                request,
+                Response.json(
+                  {
+                    error:
+                      "Grok Build is not supported in Legacy (no storage). Switch to Privacy Mode to use Grok Build. [WKE=privacy-mode:legacy]",
+                  },
+                  { status: 403 },
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+      expect(limits.unavailable?.reason).toBe("probeFailed");
+      expect(limits.unavailable?.message).toMatch(/Privacy Mode/);
+      expect(limits.unavailable?.message).not.toMatch(/WKE=|Grok Build is not supported/);
+    }),
+  );
 });
 
 it.layer(Layer.mergeAll(NodeServices.layer, NodeCrypto.layer))("readGrokAccount email", (it) => {
diff --git a/packages/provider-grok/src/server/usageLimits.ts b/packages/provider-grok/src/server/usageLimits.ts
index 8036df0dd3e99..c6ba583c139ce 100644
--- a/packages/provider-grok/src/server/usageLimits.ts
+++ b/packages/provider-grok/src/server/usageLimits.ts
@@ -38,6 +38,7 @@ const GrokUsageResponse = Schema.Struct({
     }),
   ),
 });
+const GrokErrorResponse = Schema.Struct({ error: Schema.String });
 
 function parsePeriodBoundary(value: string | undefined) {
   if (
@@ -182,6 +183,17 @@ export const readGrokAccount = Effect.fn("readGrokAccount")(function* (
         HttpClientRequest.bearerToken(token),
       ),
     );
+    if (response.status === 403) {
+      const { error } = yield* HttpClientResponse.schemaBodyJson(GrokErrorResponse)(response);
+      // xAI refuses Grok Build while the account's privacy setting is a legacy mode.
+      if (error.includes("WKE=privacy-mode:")) {
+        return makeUnavailableUsageLimits({
+          checkedAt,
+          reason: "probeFailed",
+          message: "Switch your xAI account to Privacy Mode to show Grok usage limits.",
+        });
+      }
+    }
     const body = yield* HttpClientResponse.schemaBodyJson(GrokUsageResponse)(
       yield* HttpClientResponse.filterStatusOk(response),
     );