diff --git a/README.md b/README.md
index 9b84f49..1e4884d 100644
--- a/README.md
+++ b/README.md
@@ -71,6 +71,11 @@ This tool is designed **exclusively for individuals who personally own multiple
 
 By using this software, you agree that you are the rightful owner of all accounts you add to the application. The authors are not responsible for any misuse or violations of OpenAI's terms of service.
 
+## Attribution
+
+This project is based on [Lampese/codex-switcher](https://github.com/Lampese/codex-switcher).
+Original author: Lampese.
+
 ## Versioning
 
 Use the version bump helper to keep app versions in sync across Tauri, Cargo, and the frontend.
diff --git a/src-tauri/src/auth/storage.rs b/src-tauri/src/auth/storage.rs
index 0ee5573..ba16338 100644
--- a/src-tauri/src/auth/storage.rs
+++ b/src-tauri/src/auth/storage.rs
@@ -63,11 +63,71 @@ pub fn save_accounts(store: &AccountsStore) -> Result<()> {
     Ok(())
 }
 
+fn normalized_identity_value(value: Option<&str>) -> Option<String> {
+    let normalized = value?.trim().to_ascii_lowercase();
+    if normalized.is_empty() || matches!(normalized.as_str(), "unknown" | "n/a" | "none" | "?") {
+        None
+    } else {
+        Some(normalized)
+    }
+}
+
+fn chatgpt_identity(account: &StoredAccount) -> Option<(String, String)> {
+    match &account.auth_data {
+        AuthData::ChatGPT { .. } => Some((
+            normalized_identity_value(account.email.as_deref())?,
+            normalized_identity_value(account.plan_type.as_deref())?,
+        )),
+        AuthData::ApiKey { .. } => None,
+    }
+}
+
+fn accounts_have_same_chatgpt_identity(left: &StoredAccount, right: &StoredAccount) -> bool {
+    match (chatgpt_identity(left), chatgpt_identity(right)) {
+        (Some(left_identity), Some(right_identity)) => left_identity == right_identity,
+        _ => false,
+    }
+}
+
+fn account_plan_suffix(account: &StoredAccount) -> String {
+    normalized_identity_value(account.plan_type.as_deref()).unwrap_or_else(|| "account".to_string())
+}
+
+fn ensure_unique_account_name(account: &mut StoredAccount, existing: &[StoredAccount]) {
+    if !existing.iter().any(|a| a.name == account.name) {
+        return;
+    }
+
+    let base_name = account.name.clone();
+    let suffix = account_plan_suffix(account);
+    let mut candidate = format!("{base_name} ({suffix})");
+    let mut counter = 2;
+
+    while existing.iter().any(|a| a.name == candidate) {
+        candidate = format!("{base_name} ({suffix} {counter})");
+        counter += 1;
+    }
+
+    account.name = candidate;
+}
+
 /// Add a new account to the store
-pub fn add_account(account: StoredAccount) -> Result<StoredAccount> {
+pub fn add_account(mut account: StoredAccount) -> Result<StoredAccount> {
     let mut store = load_accounts()?;
 
-    // Check for duplicate names
+    if store
+        .accounts
+        .iter()
+        .any(|existing| accounts_have_same_chatgpt_identity(existing, &account))
+    {
+        let email = account.email.as_deref().unwrap_or("unknown email");
+        let plan = account.plan_type.as_deref().unwrap_or("unknown plan");
+        anyhow::bail!("An account with email '{email}' and plan '{plan}' already exists");
+    }
+
+    ensure_unique_account_name(&mut account, &store.accounts);
+
+    // Check for duplicate names after automatic disambiguation.
     if store.accounts.iter().any(|a| a.name == account.name) {
         anyhow::bail!("An account with name '{}' already exists", account.name);
     }
@@ -263,3 +323,49 @@ pub fn set_masked_account_ids(ids: Vec<String>) -> Result<()> {
     save_accounts(&store)?;
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{accounts_have_same_chatgpt_identity, ensure_unique_account_name};
+    use crate::types::StoredAccount;
+
+    fn chatgpt_account(name: &str, email: &str, plan: &str, account_id: &str) -> StoredAccount {
+        StoredAccount::new_chatgpt(
+            name.to_string(),
+            Some(email.to_string()),
+            Some(plan.to_string()),
+            None,
+            "id-token".to_string(),
+            "access-token".to_string(),
+            "refresh-token".to_string(),
+            Some(account_id.to_string()),
+        )
+    }
+
+    #[test]
+    fn same_email_different_plan_is_not_same_chatgpt_identity() {
+        let plus = chatgpt_account("Personal", "user@example.com", "plus", "acc_plus");
+        let team = chatgpt_account("Team", "USER@example.com", "team", "acc_team");
+
+        assert!(!accounts_have_same_chatgpt_identity(&plus, &team));
+    }
+
+    #[test]
+    fn same_email_same_plan_is_same_chatgpt_identity() {
+        let first = chatgpt_account("First", "user@example.com", "plus", "acc_one");
+        let second = chatgpt_account("Second", "USER@example.com", "PLUS", "acc_two");
+
+        assert!(accounts_have_same_chatgpt_identity(&first, &second));
+    }
+
+    #[test]
+    fn duplicate_display_name_for_distinct_identity_gets_plan_suffix() {
+        let existing = chatgpt_account("user@example.com", "user@example.com", "plus", "acc_plus");
+        let mut candidate =
+            chatgpt_account("user@example.com", "user@example.com", "team", "acc_team");
+
+        ensure_unique_account_name(&mut candidate, &[existing]);
+
+        assert_eq!(candidate.name, "user@example.com (team)");
+    }
+}