diff --git a/src/plugin-handlers/config-handler.ts b/src/plugin-handlers/config-handler.ts
index 3ba18add..704036d5 100644
--- a/src/plugin-handlers/config-handler.ts
+++ b/src/plugin-handlers/config-handler.ts
@@ -260,6 +260,10 @@ export function createConfigHandler(deps: ConfigHandlerDeps) {
             .filter(([key]) => {
               if (key === "build") return false;
               if (key === "plan" && replacePlan) return false;
+              // Filter out agents that oh-my-opencode provides to prevent
+              // OpenCode defaults from overwriting user config in oh-my-opencode.json
+              // See: https://github.com/code-yeongyu/oh-my-opencode/issues/472
+              if (key in builtinAgents) return false;
               return true;
             })
             .map(([key, value]) => [