diff --git a/core/llm/autodetect.ts b/core/llm/autodetect.ts
index 2ccc325cfba..ad0bb85e7ad 100644
--- a/core/llm/autodetect.ts
+++ b/core/llm/autodetect.ts
@@ -142,7 +142,12 @@ function modelSupportsReasoning(
   if (!model) {
     return false;
   }
-  if ("anthropic" === model.underlyingProviderName) {
+  // do not turn reasoning on by default for claude 3 models
+  if (
+    model.model.includes("claude") &&
+    !model.model.includes("-3-") &&
+    !model.model.includes("-3.5-")
+  ) {
     return true;
   }
   if (model.model.includes("deepseek-r")) {