diff --git a/harness/codex/config.toml b/harness/codex/config.toml
index d5a25fe67..9598f43e3 100644
--- a/harness/codex/config.toml
+++ b/harness/codex/config.toml
@@ -1,5 +1,5 @@
 model = "gpt-5.5"
-model_reasoning_effort = "low"
+model_reasoning_effort = "medium"
 personality = "pragmatic"
 model_verbosity = "low"
 service_tier = "fast"