diff --git a/codex-rs/exec-server/src/cloud.rs b/codex-rs/exec-server/src/cloud.rs
index b4c635686d..b573fe388d 100644
--- a/codex-rs/exec-server/src/cloud.rs
+++ b/codex-rs/exec-server/src/cloud.rs
@@ -13,6 +13,7 @@ use tokio::time::sleep;
 use tokio_tungstenite::connect_async;
 use tracing::info;
 use tracing::warn;
+use uuid::Uuid;
 
 use crate::ExecServerError;
 use crate::ExecServerRuntimePaths;
@@ -131,9 +132,10 @@ impl CloudExecutorConfig {
     fn registration_request(
         &self,
         auth: &CodexAuth,
+        registration_id: Uuid,
     ) -> Result<CloudEnvironmentRegisterExecutorRequest, ExecServerError> {
         Ok(CloudEnvironmentRegisterExecutorRequest {
-            idempotency_id: self.default_idempotency_id(auth)?,
+            idempotency_id: self.default_idempotency_id(auth, registration_id)?,
             environment_id: self.cloud_environment_id.clone(),
             name: Some(self.cloud_name.clone()),
             labels: BTreeMap::new(),
@@ -141,7 +143,11 @@ impl CloudExecutorConfig {
         })
     }
 
-    fn default_idempotency_id(&self, auth: &CodexAuth) -> Result<String, ExecServerError> {
+    fn default_idempotency_id(
+        &self,
+        auth: &CodexAuth,
+        registration_id: Uuid,
+    ) -> Result<String, ExecServerError> {
         let mut hasher = sha2::Sha256::new();
         hasher.update(chatgpt_account_id(auth)?.as_bytes());
         hasher.update(b"\0");
@@ -150,6 +156,8 @@ impl CloudExecutorConfig {
         hasher.update(self.cloud_name.as_bytes());
         hasher.update(b"\0");
         hasher.update(PROTOCOL_VERSION);
+        hasher.update(b"\0");
+        hasher.update(registration_id.as_bytes());
         let digest = hasher.finalize();
         Ok(format!("codex-exec-server-{digest:x}"))
     }
@@ -164,11 +172,12 @@ pub async fn run_cloud_executor(
 ) -> Result<(), ExecServerError> {
     let client = CloudEnvironmentClient::new(config.cloud_base_url.clone(), auth_manager.clone())?;
     let processor = ConnectionProcessor::new(runtime_paths);
+    let registration_id = Uuid::new_v4();
     let mut backoff = Duration::from_secs(1);
 
     loop {
         let auth = cloud_environment_chatgpt_auth(&auth_manager).await?;
-        let request = config.registration_request(&auth)?;
+        let request = config.registration_request(&auth, registration_id)?;
         let response = client.register_executor(&request).await?;
         eprintln!(
             "codex exec-server cloud executor {} registered in environment {}",
@@ -356,8 +365,9 @@ mod tests {
     async fn register_executor_posts_with_chatgpt_auth_headers() {
         let server = MockServer::start().await;
         let auth = CodexAuth::create_dummy_chatgpt_auth_for_testing();
+        let registration_id = Uuid::from_u128(1);
         let request = CloudExecutorConfig::new(server.uri())
-            .registration_request(&auth)
+            .registration_request(&auth, registration_id)
             .expect("registration request");
         let expected_request = serde_json::to_value(&request).expect("serialize request");
         Mock::given(method("POST"))
@@ -388,4 +398,25 @@ mod tests {
             }
         );
     }
+
+    #[test]
+    fn registration_idempotency_key_is_stable_within_process_and_unique_across_launches() {
+        let auth = CodexAuth::create_dummy_chatgpt_auth_for_testing();
+        let config = CloudExecutorConfig::new("http://127.0.0.1:18084".to_string());
+        let first_registration_id = Uuid::from_u128(1);
+        let second_registration_id = Uuid::from_u128(2);
+
+        let first = config
+            .registration_request(&auth, first_registration_id)
+            .expect("first registration");
+        let repeated = config
+            .registration_request(&auth, first_registration_id)
+            .expect("repeated registration");
+        let second = config
+            .registration_request(&auth, second_registration_id)
+            .expect("second registration");
+
+        assert_eq!(first.idempotency_id, repeated.idempotency_id);
+        assert_ne!(first.idempotency_id, second.idempotency_id);
+    }
 }