diff --git a/codex-rs/core/src/models_manager/model_info.rs b/codex-rs/core/src/models_manager/model_info.rs
index c5ad8899a..19a945f95 100644
--- a/codex-rs/core/src/models_manager/model_info.rs
+++ b/codex-rs/core/src/models_manager/model_info.rs
@@ -20,8 +20,10 @@ const LOCAL_PRAGMATIC_TEMPLATE: &str = "You are a deeply pragmatic, effective so
 const PERSONALITY_PLACEHOLDER: &str = "{{ personality }}";
 
 pub(crate) fn with_config_overrides(mut model: ModelInfo, config: &Config) -> ModelInfo {
-    if let Some(supports_reasoning_summaries) = config.model_supports_reasoning_summaries {
-        model.supports_reasoning_summaries = supports_reasoning_summaries;
+    if let Some(supports_reasoning_summaries) = config.model_supports_reasoning_summaries
+        && supports_reasoning_summaries
+    {
+        model.supports_reasoning_summaries = true;
     }
     if let Some(context_window) = config.model_context_window {
         model.context_window = Some(context_window);
@@ -100,3 +102,46 @@ fn local_personality_messages_for_slug(slug: &str) -> Option<ModelMessages> {
         _ => None,
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::config::test_config;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn reasoning_summaries_override_true_enables_support() {
+        let model = model_info_from_slug("unknown-model");
+        let mut config = test_config();
+        config.model_supports_reasoning_summaries = Some(true);
+
+        let updated = with_config_overrides(model.clone(), &config);
+        let mut expected = model;
+        expected.supports_reasoning_summaries = true;
+
+        assert_eq!(updated, expected);
+    }
+
+    #[test]
+    fn reasoning_summaries_override_false_does_not_disable_support() {
+        let mut model = model_info_from_slug("unknown-model");
+        model.supports_reasoning_summaries = true;
+        let mut config = test_config();
+        config.model_supports_reasoning_summaries = Some(false);
+
+        let updated = with_config_overrides(model.clone(), &config);
+
+        assert_eq!(updated, model);
+    }
+
+    #[test]
+    fn reasoning_summaries_override_false_is_noop_when_model_is_false() {
+        let model = model_info_from_slug("unknown-model");
+        let mut config = test_config();
+        config.model_supports_reasoning_summaries = Some(false);
+
+        let updated = with_config_overrides(model.clone(), &config);
+
+        assert_eq!(updated, model);
+    }
+}