diff --git a/packages/opencode/src/server/server.ts b/packages/opencode/src/server/server.ts
index 89ac822ab9..545aa2b4c0 100644
--- a/packages/opencode/src/server/server.ts
+++ b/packages/opencode/src/server/server.ts
@@ -62,7 +62,7 @@ export namespace Server {
         log.error("failed", {
           error: err,
           message: msg,
-          stack,
+          stack: stack ? JSON.stringify(stack) : undefined,
           named,
         })
         if (err instanceof NamedError) {