diff --git a/crates/goose/src/providers/codex.rs b/crates/goose/src/providers/codex.rs
index abfa54c299d8..79cb3797fc24 100644
--- a/crates/goose/src/providers/codex.rs
+++ b/crates/goose/src/providers/codex.rs
@@ -31,7 +31,7 @@ pub const CODEX_KNOWN_MODELS: &[&str] = &[
 pub const CODEX_DOC_URL: &str = "https://developers.openai.com/codex/cli";
 
 /// Valid reasoning effort levels for Codex
-pub const CODEX_REASONING_LEVELS: &[&str] = &["low", "medium", "high"];
+pub const CODEX_REASONING_LEVELS: &[&str] = &["none", "low", "medium", "high", "xhigh"];
 
 #[derive(Debug, serde::Serialize)]
 pub struct CodexProvider {
@@ -39,7 +39,7 @@ pub struct CodexProvider {
     model: ModelConfig,
     #[serde(skip)]
     name: String,
-    /// Reasoning effort level (low, medium, high)
+    /// Reasoning effort level (none, low, medium, high, xhigh)
     reasoning_effort: String,
     /// Whether to enable skills
     enable_skills: bool,
@@ -60,15 +60,17 @@ impl CodexProvider {
             .unwrap_or_else(|_| "high".to_string());
 
         // Validate reasoning effort
-        let reasoning_effort = if CODEX_REASONING_LEVELS.contains(&reasoning_effort.as_str()) {
-            reasoning_effort
-        } else {
-            tracing::warn!(
-                "Invalid CODEX_REASONING_EFFORT '{}', using 'high'",
+        let reasoning_effort =
+            if Self::supports_reasoning_effort(&model.model_name, &reasoning_effort) {
                 reasoning_effort
-            );
-            "high".to_string()
-        };
+            } else {
+                tracing::warn!(
+                    "Invalid CODEX_REASONING_EFFORT '{}' for model '{}', using 'high'",
+                    reasoning_effort,
+                    model.model_name
+                );
+                "high".to_string()
+            };
 
         // Get enable_skills from config, default to true
         let enable_skills = config
@@ -92,6 +94,18 @@ impl CodexProvider {
         })
     }
 
+    fn supports_reasoning_effort(model_name: &str, reasoning_effort: &str) -> bool {
+        if !CODEX_REASONING_LEVELS.contains(&reasoning_effort) {
+            return false;
+        }
+
+        if reasoning_effort == "none" && model_name.contains("codex") {
+            return false;
+        }
+
+        true
+    }
+
     /// Convert goose messages to a simple text prompt format
     /// Similar to Gemini CLI, we use Human:/Assistant: prefixes
     fn messages_to_prompt(&self, system: &str, messages: &[Message]) -> String {
@@ -699,12 +713,28 @@ mod tests {
 
     #[test]
     fn test_reasoning_level_validation() {
+        assert!(CODEX_REASONING_LEVELS.contains(&"none"));
         assert!(CODEX_REASONING_LEVELS.contains(&"low"));
         assert!(CODEX_REASONING_LEVELS.contains(&"medium"));
         assert!(CODEX_REASONING_LEVELS.contains(&"high"));
+        assert!(CODEX_REASONING_LEVELS.contains(&"xhigh"));
+        assert!(!CODEX_REASONING_LEVELS.contains(&"minimal"));
         assert!(!CODEX_REASONING_LEVELS.contains(&"invalid"));
     }
 
+    #[test]
+    fn test_reasoning_effort_support_by_model() {
+        assert!(CodexProvider::supports_reasoning_effort("gpt-5.2", "none"));
+        assert!(!CodexProvider::supports_reasoning_effort(
+            "gpt-5.2-codex",
+            "none"
+        ));
+        assert!(CodexProvider::supports_reasoning_effort(
+            "gpt-5.2-codex",
+            "xhigh"
+        ));
+    }
+
     #[test]
     fn test_known_models() {
         assert!(CODEX_KNOWN_MODELS.contains(&"gpt-5.2-codex"));