Index: codex-rs/core/src/config/mod.rs
--- codex-rs/core/src/config/mod.rs.orig
+++ codex-rs/core/src/config/mod.rs
@@ -1513,7 +1513,7 @@ impl Config {
 
         let review_model = override_review_model.or(cfg.review_model);
 
-        let check_for_update_on_startup = cfg.check_for_update_on_startup.unwrap_or(true);
+        let check_for_update_on_startup = cfg.check_for_update_on_startup.unwrap_or(false);
 
         // Ensure that every field of ConfigRequirements is applied to the final
         // Config.
@@ -3824,7 +3824,7 @@ model_verbosity = "high"
                 active_project: ProjectConfig { trust_level: None },
                 windows_wsl_setup_acknowledged: false,
                 notices: Default::default(),
-                check_for_update_on_startup: true,
+                check_for_update_on_startup: false,
                 disable_paste_burst: false,
                 tui_notifications: Default::default(),
                 tui_notification_method: Default::default(),
