fix: guide recovery after upgrading from an auto-login installation

docs/docs/Develop/api-keys-and-authentication.mdx

@@ -189,10 +189,45 @@ If your flows use the File System component, also follow [Move shared files when
 4. Set `LANGFLOW_AUTO_LOGIN=false`, set `LANGFLOW_SUPERUSER` to the existing account's username, and set `LANGFLOW_SUPERUSER_PASSWORD` before restarting or upgrading. Startup requires this setting, but it does **not** overwrite a non-legacy password on an existing account. Use the password established in the previous steps.
 5. Start the new release with the existing database and configuration directory. In a fresh browser session, sign in with the established password and verify that your existing flows are present.
 
-Do not delete the existing account, database, or encryption key to regain access. Creating a different superuser does not transfer ownership of the existing account's flows. If you upgraded before preparing the account, use an existing administrator credential to update that account's password; if none is available, complete the preparation on a backed-up previous installation restricted to local access before upgrading again.
+Do not delete the existing account, database, or encryption key to regain access. Creating a different superuser does not transfer ownership of the existing account's flows. If you already upgraded without preparing the account, see [Recover access after upgrading](#recover-access-after-upgrading).
 
 An explicit `LANGFLOW_AUTO_LOGIN=true` in an existing environment or `.env` file takes precedence over the new default. Remove that override or set it to `false` as part of the transition. Disabling auto-login prevents new anonymous sessions; it does not revoke previously issued sessions or API keys.
 
+##### Recover access after upgrading {#recover-access-after-upgrading}
+
+If you upgraded without preparing the account, Langflow starts but you can't sign in to the account that owns your flows.
+That account uses a generated bootstrap password that you never saw, and `LANGFLOW_SUPERUSER_PASSWORD` doesn't replace it.
+Your flows are still in the database.
+To recover them, temporarily re-enable auto-login and set a password on that same account:
+
+1. Back up the database and configuration directory.
+2. Stop Langflow. Set `LANGFLOW_AUTO_LOGIN=true` in the environment or `.env` file, then start Langflow with the same database and configuration directory. Keep the instance restricted to trusted local access until you finish.
+3. Request an auto-login token, and copy the `access_token` value from the response:
+
+    ```bash
+    curl -s http://localhost:7860/api/v1/auto_login
+    ```
+
+4. Get the account's ID, and copy the `id` value from the response:
+
+    ```bash
+    curl -s http://localhost:7860/api/v1/users/whoami \
+      -H "Authorization: Bearer ACCESS_TOKEN"
+    ```
+
+5. Set a strong password on that account. Don't use the legacy default value `langflow`. Read the password into a variable so that it isn't stored in your shell history, and avoid `"` and `\` characters, which break the JSON body.
+
+    ```bash
+    read -rs NEW_PASSWORD
+    curl -s -X PATCH http://localhost:7860/api/v1/users/USER_ID \
+      -H "Authorization: Bearer ACCESS_TOKEN" \
+      -H "Content-Type: application/json" \
+      -d "{\"password\": \"$NEW_PASSWORD\"}"
+    ```
+
+6. Stop Langflow. Remove `LANGFLOW_AUTO_LOGIN=true` or set it to `false`. If the account's username isn't `langflow`, set `LANGFLOW_SUPERUSER` to it. Set `LANGFLOW_SUPERUSER_PASSWORD` to the password from step 5. Startup requires this variable, but it doesn't overwrite the password you just set.
+7. Start Langflow, sign in with that username and password, and verify that your existing flows are present.
+
 #### LANGFLOW_SKIP_AUTH_AUTO_LOGIN {#langflow-skip-auth-auto-login}
 
 When `LANGFLOW_AUTO_LOGIN=true`, set `LANGFLOW_SKIP_AUTH_AUTO_LOGIN=true` to also skip authentication for API requests.

docs/docs/Get-Started/get-started-installation.mdx

@@ -224,6 +224,13 @@ To install a specific version of the Langflow package, add the required version
 
 To reinstall Langflow and all of its dependencies, run `uv pip install langflow --force-reinstall`.
 
+:::warning Upgrading from an auto-login installation
+Langflow 1.13 disables auto-login by default.
+Before you upgrade an installation that signs in automatically, [prepare the existing account for password sign-in](/api-keys-and-authentication#upgrade-from-auto-login).
+If you already upgraded and can't sign in, see [Recover access after upgrading](/api-keys-and-authentication#recover-access-after-upgrading).
+Don't delete or reinstall Langflow to regain access, because that can permanently remove your flows.
+:::
+
 :::note Langflow 1.12 package migration
 The new runnable `langflow-base` package starts at version `1.12.0` and stays
 version-aligned with `langflow`. Requirements such as

docs/docs/Support/troubleshooting.mdx

@@ -542,6 +542,24 @@ If you're experiencing this issue, update your Langflow installation to version
 uv pip install langflow -U
 ```
 
+### Can't sign in after upgrading from an auto-login installation {#cant-sign-in-after-upgrade}
+
+Langflow 1.13 disables auto-login by default.
+After you upgrade an installation that signed in automatically, one of the following can occur:
+
+* Startup exits with `Username and password must be set`.
+* Langflow starts, but sign-in fails with `Incorrect username or password` even after you set `LANGFLOW_SUPERUSER_PASSWORD`.
+* The sign-up page creates a new account that doesn't have your existing flows.
+
+Your flows are still in the database. They belong to the account that auto-login used, which has a generated password that `LANGFLOW_SUPERUSER_PASSWORD` doesn't replace.
+
+To resolve this issue:
+
+1. If startup exits, set `LANGFLOW_SUPERUSER_PASSWORD` before you start Langflow.
+2. If sign-in still fails, follow [Recover access after upgrading](/api-keys-and-authentication#recover-access-after-upgrading).
+
+Don't delete the database or reinstall Langflow to regain access, because that can permanently remove your flows.
+
 ## Langflow MCP issues {#mcp}
 
 The following issues can occur when using Langflow as an MCP server or client.

src/backend/base/langflow/services/utils.py

@@ -221,7 +221,12 @@ async def setup_superuser(settings_service: SettingsService, session: AsyncSessi
     await logger.adebug(f"Setup superuser: username={username}, has_password={bool(password)}")
 
     if not username or not password:
-        msg = "Username and password must be set"
+        msg = (
+            "Username and password must be set. "
+            "Set LANGFLOW_SUPERUSER_PASSWORD before starting Langflow. "
+            "If you are upgrading an existing auto-login installation, "
+            "see https://docs.langflow.org/next/api-keys-and-authentication#upgrade-from-auto-login"
+        )
         await logger.aerror(f"Missing credentials: username={username}, password={'set' if password else 'not set'}")
         raise ValueError(msg)
 

src/backend/tests/unit/test_setup_superuser_flow.py

@@ -299,9 +299,12 @@ async def test_setup_superuser_with_no_configured_credentials_fails_closed(initi
     settings.auth_settings.SUPERUSER_PASSWORD = ""
 
     async with session_scope() as session:
-        with pytest.raises(ValueError, match="Username and password must be set"):
+        with pytest.raises(ValueError, match="Username and password must be set") as exc_info:
             await setup_superuser(settings, session)
 
+    assert "LANGFLOW_SUPERUSER_PASSWORD" in str(exc_info.value)
+    assert "api-keys-and-authentication#upgrade-from-auto-login" in str(exc_info.value)
+
 
 @pytest.mark.parametrize("username", [DEFAULT_SUPERUSER, "custom_admin"])
 @pytest.mark.asyncio