diff --git a/src/lib/langfuse/trace-proxy-request.ts b/src/lib/langfuse/trace-proxy-request.ts
index 2d4ec6bc3..09a23f7fd 100644
--- a/src/lib/langfuse/trace-proxy-request.ts
+++ b/src/lib/langfuse/trace-proxy-request.ts
@@ -408,7 +408,7 @@ export async function traceProxyRequest(ctx: TraceContext): Promise<void> {
     );
 
     // Explicitly set trace-level input/output (propagateAttributes does not support these)
-    rootSpan.updateTrace({
+    rootSpan.setTraceIO({
       input: actualRequestBody,
       output: actualResponseBody,
     });