diff --git a/codex-rs/tui/src/model_migration_notice.rs b/codex-rs/tui/src/model_migration_notice.rs
new file mode 100644
index 0000000000..ee447434ae
--- /dev/null
+++ b/codex-rs/tui/src/model_migration_notice.rs
@@ -0,0 +1,109 @@
+use codex_core::config::Config;
+use serde::Deserialize;
+use serde::Serialize;
+use std::path::PathBuf;
+
+/// Pending "show on next run" model migration notice.
+///
+/// This is persisted outside `config.toml` to avoid growing the config file with
+/// ephemeral UI state.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
+pub struct PendingModelMigrationNotice {
+    pub from_model: String,
+    pub to_model: String,
+}
+
+const MODEL_MIGRATION_NOTICE_FILENAME: &str = "model_migration_notice.json";
+
+fn pending_model_migration_notice_filepath(config: &Config) -> PathBuf {
+    config.codex_home.join(MODEL_MIGRATION_NOTICE_FILENAME)
+}
+
+/// Read a pending notice if present.
+///
+/// Returns `Ok(None)` if no pending notice is scheduled.
+pub async fn read_pending_model_migration_notice(
+    config: &Config,
+) -> anyhow::Result<Option<PendingModelMigrationNotice>> {
+    let path = pending_model_migration_notice_filepath(config);
+    let contents = match tokio::fs::read_to_string(&path).await {
+        Ok(contents) => contents,
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => return Ok(None),
+        Err(err) => return Err(err.into()),
+    };
+    Ok(Some(serde_json::from_str(contents.trim())?))
+}
+
+/// Persist a pending notice to be displayed on the next run.
+pub async fn write_pending_model_migration_notice(
+    config: &Config,
+    from_model: &str,
+    to_model: &str,
+) -> anyhow::Result<()> {
+    let path = pending_model_migration_notice_filepath(config);
+    let notice = PendingModelMigrationNotice {
+        from_model: from_model.to_string(),
+        to_model: to_model.to_string(),
+    };
+    let json_line = format!("{}\n", serde_json::to_string(&notice)?);
+    if let Some(parent) = path.parent() {
+        tokio::fs::create_dir_all(parent).await?;
+    }
+    tokio::fs::write(path, json_line).await?;
+    Ok(())
+}
+
+/// Clear any pending notice.
+pub async fn clear_pending_model_migration_notice(config: &Config) -> anyhow::Result<()> {
+    let path = pending_model_migration_notice_filepath(config);
+    match tokio::fs::remove_file(path).await {
+        Ok(()) => Ok(()),
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => Ok(()),
+        Err(err) => Err(err.into()),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use codex_core::config::ConfigBuilder;
+    use pretty_assertions::assert_eq;
+
+    #[tokio::test]
+    async fn write_read_clear_round_trips() {
+        let tmp = tempfile::tempdir().expect("tmpdir");
+        let config = ConfigBuilder::default()
+            .codex_home(tmp.path().to_path_buf())
+            .build()
+            .await
+            .expect("config");
+
+        assert_eq!(
+            read_pending_model_migration_notice(&config).await.unwrap(),
+            None
+        );
+
+        write_pending_model_migration_notice(&config, "gpt-5", "gpt-5.1")
+            .await
+            .expect("write");
+
+        assert_eq!(
+            read_pending_model_migration_notice(&config)
+                .await
+                .expect("read"),
+            Some(PendingModelMigrationNotice {
+                from_model: "gpt-5".to_string(),
+                to_model: "gpt-5.1".to_string(),
+            })
+        );
+
+        clear_pending_model_migration_notice(&config)
+            .await
+            .expect("clear");
+
+        assert_eq!(
+            read_pending_model_migration_notice(&config).await.unwrap(),
+            None
+        );
+    }
+}