diff --git a/codex-rs/core/src/config.rs b/codex-rs/core/src/config.rs
index b4f96b5e..0eba6c85 100644
--- a/codex-rs/core/src/config.rs
+++ b/codex-rs/core/src/config.rs
@@ -835,7 +835,7 @@ impl Config {
                 .unwrap_or(false),
             use_experimental_unified_exec_tool: cfg
                 .experimental_use_unified_exec_tool
-                .unwrap_or(true),
+                .unwrap_or(false),
             include_view_image_tool,
             active_profile: active_profile_name,
             disable_paste_burst: cfg.disable_paste_burst.unwrap_or(false),
@@ -1210,7 +1210,7 @@ model_verbosity = "high"
                 include_apply_patch_tool: false,
                 tools_web_search_request: false,
                 use_experimental_streamable_shell_tool: false,
-                use_experimental_unified_exec_tool: true,
+                use_experimental_unified_exec_tool: false,
                 include_view_image_tool: true,
                 active_profile: Some("o3".to_string()),
                 disable_paste_burst: false,
@@ -1267,7 +1267,7 @@ model_verbosity = "high"
             include_apply_patch_tool: false,
             tools_web_search_request: false,
             use_experimental_streamable_shell_tool: false,
-            use_experimental_unified_exec_tool: true,
+            use_experimental_unified_exec_tool: false,
             include_view_image_tool: true,
             active_profile: Some("gpt3".to_string()),
             disable_paste_burst: false,
@@ -1339,7 +1339,7 @@ model_verbosity = "high"
             include_apply_patch_tool: false,
             tools_web_search_request: false,
             use_experimental_streamable_shell_tool: false,
-            use_experimental_unified_exec_tool: true,
+            use_experimental_unified_exec_tool: false,
             include_view_image_tool: true,
             active_profile: Some("zdr".to_string()),
             disable_paste_burst: false,
@@ -1397,7 +1397,7 @@ model_verbosity = "high"
             include_apply_patch_tool: false,
             tools_web_search_request: false,
             use_experimental_streamable_shell_tool: false,
-            use_experimental_unified_exec_tool: true,
+            use_experimental_unified_exec_tool: false,
             include_view_image_tool: true,
             active_profile: Some("gpt5".to_string()),
             disable_paste_burst: false,
diff --git a/codex-rs/core/tests/suite/prompt_caching.rs b/codex-rs/core/tests/suite/prompt_caching.rs
index e77df01f..5ac3da60 100644
--- a/codex-rs/core/tests/suite/prompt_caching.rs
+++ b/codex-rs/core/tests/suite/prompt_caching.rs
@@ -191,8 +191,7 @@ async fn prompt_tools_are_consistent_across_requests() {
     let expected_instructions: &str = include_str!("../../prompt.md");
     // our internal implementation is responsible for keeping tools in sync
     // with the OpenAI schema, so we just verify the tool presence here
-    let expected_tools_names: &[&str] =
-        &["unified_exec", "update_plan", "apply_patch", "view_image"];
+    let expected_tools_names: &[&str] = &["shell", "update_plan", "apply_patch", "view_image"];
     let body0 = requests[0].body_json::<serde_json::Value>().unwrap();
     assert_eq!(
         body0["instructions"],