diff --git a/codex-rs/app-server-test-client/src/main.rs b/codex-rs/app-server-test-client/src/main.rs
index b66c59d55a..166acb3cc4 100644
--- a/codex-rs/app-server-test-client/src/main.rs
+++ b/codex-rs/app-server-test-client/src/main.rs
@@ -43,8 +43,14 @@ use codex_app_server_protocol::SendUserMessageParams;
 use codex_app_server_protocol::SendUserMessageResponse;
 use codex_app_server_protocol::ServerNotification;
 use codex_app_server_protocol::ServerRequest;
+use codex_app_server_protocol::ThreadItem;
+use codex_app_server_protocol::ThreadResumeParams;
+use codex_app_server_protocol::ThreadResumeResponse;
+use codex_app_server_protocol::ThreadRollbackParams;
+use codex_app_server_protocol::ThreadRollbackResponse;
 use codex_app_server_protocol::ThreadStartParams;
 use codex_app_server_protocol::ThreadStartResponse;
+use codex_app_server_protocol::Turn;
 use codex_app_server_protocol::TurnStartParams;
 use codex_app_server_protocol::TurnStartResponse;
 use codex_app_server_protocol::TurnStatus;
@@ -113,6 +119,9 @@ enum CliCommand {
     TestLogin,
     /// Fetch the current account rate limits from the Codex app-server.
     GetAccountRateLimits,
+    /// Send multiple turns, roll back the most recent turn, and verify the thread history changed.
+    #[command(name = "thread-rollback")]
+    ThreadRollback,
 }
 
 fn main() -> Result<()> {
@@ -134,6 +143,7 @@ fn main() -> Result<()> {
         } => send_follow_up_v2(codex_bin, first_message, follow_up_message),
         CliCommand::TestLogin => test_login(codex_bin),
         CliCommand::GetAccountRateLimits => get_account_rate_limits(codex_bin),
+        CliCommand::ThreadRollback => thread_rollback(codex_bin),
     }
 }
 
@@ -213,10 +223,7 @@ fn send_message_v2_with_policies(
     turn_params.approval_policy = approval_policy;
     turn_params.sandbox_policy = sandbox_policy;
 
-    let turn_response = client.turn_start(turn_params)?;
-    println!("< turn/start response: {turn_response:?}");
-
-    client.stream_turn(&thread_response.thread.id, &turn_response.turn.id)?;
+    let _ = client.run_turn(turn_params)?;
 
     Ok(())
 }
@@ -234,27 +241,8 @@ fn send_follow_up_v2(
     let thread_response = client.thread_start(ThreadStartParams::default())?;
     println!("< thread/start response: {thread_response:?}");
 
-    let first_turn_params = TurnStartParams {
-        thread_id: thread_response.thread.id.clone(),
-        input: vec![V2UserInput::Text {
-            text: first_message,
-        }],
-        ..Default::default()
-    };
-    let first_turn_response = client.turn_start(first_turn_params)?;
-    println!("< turn/start response (initial): {first_turn_response:?}");
-    client.stream_turn(&thread_response.thread.id, &first_turn_response.turn.id)?;
-
-    let follow_up_params = TurnStartParams {
-        thread_id: thread_response.thread.id.clone(),
-        input: vec![V2UserInput::Text {
-            text: follow_up_message,
-        }],
-        ..Default::default()
-    };
-    let follow_up_response = client.turn_start(follow_up_params)?;
-    println!("< turn/start response (follow-up): {follow_up_response:?}");
-    client.stream_turn(&thread_response.thread.id, &follow_up_response.turn.id)?;
+    let _ = client.run_turn_text(&thread_response.thread.id, first_message)?;
+    let _ = client.run_turn_text(&thread_response.thread.id, follow_up_message)?;
 
     Ok(())
 }
@@ -301,6 +289,143 @@ fn get_account_rate_limits(codex_bin: String) -> Result<()> {
     Ok(())
 }
 
+fn thread_rollback(codex_bin: String) -> Result<()> {
+    let codex_bin_resume = codex_bin.clone();
+    let mut client = CodexClient::spawn(codex_bin)?;
+
+    let initialize = client.initialize()?;
+    println!("< initialize response: {initialize:?}");
+
+    let thread_response = client.thread_start(ThreadStartParams::default())?;
+    println!("< thread/start response: {thread_response:?}");
+    let thread_id = thread_response.thread.id;
+
+    let _ = client.run_turn_text(&thread_id, "Say pineapple")?;
+    let _ = client.run_turn_text(&thread_id, "Say banana")?;
+
+    let rollback_response = client.thread_rollback(ThreadRollbackParams {
+        thread_id: thread_id.clone(),
+        num_turns: 1,
+    })?;
+    println!("< thread/rollback response: {rollback_response:?}");
+
+    let answer = client
+        .run_turn_text(&thread_id, "What was the last word you said?")?
+        .context("turn completed without an agent message item")?;
+
+    if answer.to_lowercase().contains("pineapple") {
+        println!("Rollback success!");
+    } else {
+        println!("Rollback did not work as expected!");
+    }
+
+    let mut resume_client = CodexClient::spawn(codex_bin_resume)?;
+    let initialize = resume_client.initialize()?;
+    println!("< initialize response (resume client): {initialize:?}");
+
+    let resume_response = resume_client.thread_resume(ThreadResumeParams {
+        thread_id: thread_id.clone(),
+        ..Default::default()
+    })?;
+    println!("< thread/resume response: {resume_response:?}");
+
+    verify_resumed_thread_after_rollback(
+        &resume_response,
+        "Say pineapple",
+        "Say banana",
+        "What was the last word you said?",
+        "pineapple",
+    )?;
+    println!("Resume verification success!");
+
+    Ok(())
+}
+
+fn verify_resumed_thread_after_rollback(
+    resume: &ThreadResumeResponse,
+    expected_first_prompt: &str,
+    rolled_back_prompt: &str,
+    expected_follow_up_prompt: &str,
+    expected_word: &str,
+) -> Result<()> {
+    let mut saw_expected_first_turn = false;
+    let mut saw_expected_follow_up_turn = false;
+
+    for turn in &resume.thread.turns {
+        let user_messages = turn_user_messages(turn);
+        let agent_messages = turn_agent_messages(turn);
+
+        for user_message in &user_messages {
+            if user_message.contains(rolled_back_prompt) {
+                bail!(
+                    "thread/resume returned a rolled back prompt: {rolled_back_prompt:?} (thread {})",
+                    resume.thread.id
+                );
+            }
+        }
+
+        if user_messages
+            .iter()
+            .any(|message| message.contains(expected_first_prompt))
+            && agent_messages
+                .iter()
+                .any(|message| message.to_lowercase().contains(expected_word))
+        {
+            saw_expected_first_turn = true;
+        }
+
+        if user_messages
+            .iter()
+            .any(|message| message.contains(expected_follow_up_prompt))
+            && agent_messages
+                .iter()
+                .any(|message| message.to_lowercase().contains(expected_word))
+        {
+            saw_expected_follow_up_turn = true;
+        }
+    }
+
+    if !saw_expected_first_turn {
+        bail!(
+            "thread/resume did not include expected prompt {expected_first_prompt:?} with answer containing {expected_word:?}"
+        );
+    }
+
+    if !saw_expected_follow_up_turn {
+        bail!(
+            "thread/resume did not include expected prompt {expected_follow_up_prompt:?} with answer containing {expected_word:?}"
+        );
+    }
+
+    Ok(())
+}
+
+fn turn_user_messages(turn: &Turn) -> Vec<String> {
+    turn.items
+        .iter()
+        .filter_map(|item| match item {
+            ThreadItem::UserMessage { content, .. } => Some(content),
+            _ => None,
+        })
+        .flat_map(|content| {
+            content.iter().filter_map(|input| match input {
+                V2UserInput::Text { text } => Some(text.clone()),
+                _ => None,
+            })
+        })
+        .collect()
+}
+
+fn turn_agent_messages(turn: &Turn) -> Vec<String> {
+    turn.items
+        .iter()
+        .filter_map(|item| match item {
+            ThreadItem::AgentMessage { text, .. } => Some(text.clone()),
+            _ => None,
+        })
+        .collect()
+}
+
 struct CodexClient {
     child: Child,
     stdin: Option<ChildStdin>,
@@ -422,6 +547,16 @@ impl CodexClient {
         self.send_request(request, request_id, "thread/start")
     }
 
+    fn thread_resume(&mut self, params: ThreadResumeParams) -> Result<ThreadResumeResponse> {
+        let request_id = self.request_id();
+        let request = ClientRequest::ThreadResume {
+            request_id: request_id.clone(),
+            params,
+        };
+
+        self.send_request(request, request_id, "thread/resume")
+    }
+
     fn turn_start(&mut self, params: TurnStartParams) -> Result<TurnStartResponse> {
         let request_id = self.request_id();
         let request = ClientRequest::TurnStart {
@@ -432,6 +567,39 @@ impl CodexClient {
         self.send_request(request, request_id, "turn/start")
     }
 
+    fn run_turn(&mut self, params: TurnStartParams) -> Result<Option<String>> {
+        let thread_id = params.thread_id.clone();
+        let turn_response = self.turn_start(params)?;
+        println!("< turn/start response: {turn_response:?}");
+        self.stream_turn(&thread_id, &turn_response.turn.id)
+    }
+
+    fn run_turn_text(
+        &mut self,
+        thread_id: &str,
+        user_message: impl Into<String>,
+    ) -> Result<Option<String>> {
+        let turn_params = TurnStartParams {
+            thread_id: thread_id.to_string(),
+            input: vec![V2UserInput::Text {
+                text: user_message.into(),
+            }],
+            ..Default::default()
+        };
+
+        self.run_turn(turn_params)
+    }
+
+    fn thread_rollback(&mut self, params: ThreadRollbackParams) -> Result<ThreadRollbackResponse> {
+        let request_id = self.request_id();
+        let request = ClientRequest::ThreadRollback {
+            request_id: request_id.clone(),
+            params,
+        };
+
+        self.send_request(request, request_id, "thread/rollback")
+    }
+
     fn login_chat_gpt(&mut self) -> Result<LoginChatGptResponse> {
         let request_id = self.request_id();
         let request = ClientRequest::LoginChatGpt {
@@ -526,7 +694,9 @@ impl CodexClient {
         }
     }
 
-    fn stream_turn(&mut self, thread_id: &str, turn_id: &str) -> Result<()> {
+    fn stream_turn(&mut self, thread_id: &str, turn_id: &str) -> Result<Option<String>> {
+        let mut last_agent_message = None::<String>;
+
         loop {
             let notification = self.next_notification()?;
 
@@ -561,7 +731,16 @@ impl CodexClient {
                     println!("\n< item started: {:?}", payload.item);
                 }
                 ServerNotification::ItemCompleted(payload) => {
-                    println!("< item completed: {:?}", payload.item);
+                    if payload.thread_id == thread_id && payload.turn_id == turn_id {
+                        if let ThreadItem::AgentMessage { text, .. } = payload.item {
+                            last_agent_message = Some(text);
+                            println!("< agent message completed >");
+                        } else {
+                            println!("< item completed: {:?}", payload.item);
+                        }
+                    } else {
+                        println!("< item completed: {:?}", payload.item);
+                    }
                 }
                 ServerNotification::TurnCompleted(payload) => {
                     if payload.turn.id == turn_id {
@@ -583,7 +762,7 @@ impl CodexClient {
             }
         }
 
-        Ok(())
+        Ok(last_agent_message)
     }
 
     fn extract_event(