diff --git a/codex-rs/core/src/unified_exec/process_manager.rs b/codex-rs/core/src/unified_exec/process_manager.rs
index 851b92d24f1..e51dc5e266c 100644
--- a/codex-rs/core/src/unified_exec/process_manager.rs
+++ b/codex-rs/core/src/unified_exec/process_manager.rs
@@ -47,7 +47,7 @@ use crate::unified_exec::process::OutputHandles;
 use crate::unified_exec::process::UnifiedExecProcess;
 use crate::unified_exec::resolve_max_tokens;
 
-const UNIFIED_EXEC_ENV: [(&str, &str); 9] = [
+const UNIFIED_EXEC_ENV: [(&str, &str); 10] = [
     ("NO_COLOR", "1"),
     ("TERM", "dumb"),
     ("LANG", "C.UTF-8"),
@@ -57,6 +57,7 @@ const UNIFIED_EXEC_ENV: [(&str, &str); 9] = [
     ("PAGER", "cat"),
     ("GIT_PAGER", "cat"),
     ("GH_PAGER", "cat"),
+    ("CODEX_CI", "1"),
 ];
 
 fn apply_unified_exec_env(mut env: HashMap<String, String>) -> HashMap<String, String> {
@@ -688,6 +689,7 @@ mod tests {
             ("PAGER".to_string(), "cat".to_string()),
             ("GIT_PAGER".to_string(), "cat".to_string()),
             ("GH_PAGER".to_string(), "cat".to_string()),
+            ("CODEX_CI".to_string(), "1".to_string()),
         ]);
 
         assert_eq!(env, expected);