diff --git a/packages/opencode/src/bus/bus-event.ts b/packages/opencode/src/bus/bus-event.ts
index 0e58e962dc..d97922290e 100644
--- a/packages/opencode/src/bus/bus-event.ts
+++ b/packages/opencode/src/bus/bus-event.ts
@@ -17,7 +17,8 @@ export namespace BusEvent {
 
   export function payloads() {
     return z
-      .union(
+      .discriminatedUnion(
+        "type",
         registry
           .entries()
           .map(([type, def]) => {