diff --git a/apps/backend/src/lib/ai/models.ts b/apps/backend/src/lib/ai/models.ts
index 00cea899d..69c58eaf6 100644
--- a/apps/backend/src/lib/ai/models.ts
+++ b/apps/backend/src/lib/ai/models.ts
@@ -32,7 +32,7 @@ const MODEL_SELECTION_MATRIX: Record<
       unauthenticated: { modelId: "z-ai/glm-5.2" },
     },
     fast: {
-      authenticated: { modelId: "google/gemini-3.5-flash" },
+      authenticated: { modelId: "openai/gpt-5.5" },
       unauthenticated: { modelId: "google/gemini-3.5-flash" },
     },
   },