diff --git a/codex-rs/app-server/tests/suite/v2/thread_read.rs b/codex-rs/app-server/tests/suite/v2/thread_read.rs
index d8ca3aa696..ac3442fd3d 100644
--- a/codex-rs/app-server/tests/suite/v2/thread_read.rs
+++ b/codex-rs/app-server/tests/suite/v2/thread_read.rs
@@ -2,7 +2,9 @@ use anyhow::Result;
 use app_test_support::McpProcess;
 use app_test_support::create_fake_rollout_with_text_elements;
 use app_test_support::create_mock_responses_server_repeating_assistant;
+use app_test_support::rollout_path;
 use app_test_support::to_response;
+use chrono::Utc;
 use codex_app_server_protocol::JSONRPCResponse;
 use codex_app_server_protocol::RequestId;
 use codex_app_server_protocol::SessionSource;
@@ -14,6 +16,7 @@ use codex_app_server_protocol::UserInput;
 use codex_protocol::user_input::ByteRange;
 use codex_protocol::user_input::TextElement;
 use pretty_assertions::assert_eq;
+use std::fs::FileTimes;
 use std::path::Path;
 use std::path::PathBuf;
 use tempfile::TempDir;
@@ -134,6 +137,57 @@ async fn thread_read_can_include_turns() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn thread_read_does_not_change_updated_at_or_mtime() -> Result<()> {
+    let server = create_mock_responses_server_repeating_assistant("Done").await;
+    let codex_home = TempDir::new()?;
+    create_config_toml(codex_home.path(), &server.uri())?;
+
+    let preview = "Saved user message";
+    let filename_ts = "2025-01-05T12-00-00";
+    let meta_rfc3339 = "2025-01-05T12:00:00Z";
+    let expected_updated_at_rfc3339 = "2025-01-07T00:00:00Z";
+    let conversation_id = create_fake_rollout_with_text_elements(
+        codex_home.path(),
+        filename_ts,
+        meta_rfc3339,
+        preview,
+        Vec::new(),
+        Some("mock_provider"),
+        None,
+    )?;
+    let rollout_file_path = rollout_path(codex_home.path(), filename_ts, &conversation_id);
+    set_rollout_mtime(rollout_file_path.as_path(), expected_updated_at_rfc3339)?;
+
+    let before_modified = std::fs::metadata(&rollout_file_path)?.modified()?;
+
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
+
+    let read_id = mcp
+        .send_thread_read_request(ThreadReadParams {
+            thread_id: conversation_id,
+            include_turns: false,
+        })
+        .await?;
+    let read_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(read_id)),
+    )
+    .await??;
+    let ThreadReadResponse { thread } = to_response::<ThreadReadResponse>(read_resp)?;
+
+    let expected_updated_at = chrono::DateTime::parse_from_rfc3339(expected_updated_at_rfc3339)?
+        .with_timezone(&Utc)
+        .timestamp();
+    assert_eq!(thread.updated_at, expected_updated_at);
+
+    let after_modified = std::fs::metadata(&rollout_file_path)?.modified()?;
+    assert_eq!(after_modified, before_modified);
+
+    Ok(())
+}
+
 // Helper to create a config.toml pointing at the mock model server.
 fn create_config_toml(codex_home: &Path, server_uri: &str) -> std::io::Result<()> {
     let config_toml = codex_home.join("config.toml");
@@ -157,3 +211,13 @@ stream_max_retries = 0
         ),
     )
 }
+
+fn set_rollout_mtime(path: &Path, updated_at_rfc3339: &str) -> Result<()> {
+    let parsed = chrono::DateTime::parse_from_rfc3339(updated_at_rfc3339)?.with_timezone(&Utc);
+    let times = FileTimes::new().set_modified(parsed.into());
+    std::fs::OpenOptions::new()
+        .append(true)
+        .open(path)?
+        .set_times(times)?;
+    Ok(())
+}