Redux Toolkit configureStore middleware ordering when using a plain array

Answer

Redux Toolkit does not offer a flag or option that forces custom middleware to run after the default middleware when you supply a plain array to configureStore’s middleware option.

Why the plain array approach loses order

When you pass a plain array, RTK replaces the entire default middleware chain with that array; the defaults are not automatically appended or prepended. Consequently the relative order of your custom middleware versus thunk, immutableCheck and serializableCheck is whatever you place in the array, and there is no built‑in way to guarantee they appear after the defaults.

Confirmed facts (RTK ≥ 1.9)

• The default middleware, when all checks are enabled, is returned by getDefaultMiddleware() in the order [thunk, immutableCheck, serializableCheck].
• This order is not exposed as a public constant and may change in future releases.
• RTK provides only two ways to supply middleware: a plain array (replaces defaults) or a callback that receives getDefaultMiddleware.

Reliable pattern to guarantee custom middleware runs after defaults

1. Use the callback form:

const store = configureStore({
  reducer: rootReducer,
  middleware: (getDefaultMiddleware) =>
    getDefaultMiddleware().concat(customLogger, customAnalytics),
});

2. Or, if you prefer the array syntax, explicitly spread the defaults:

const store = configureStore({
  reducer: rootReducer,
  middleware: [...getDefaultMiddleware(), customLogger, customAnalytics],
});

Diagnostic question

Are you disabling any of the default middleware via options passed to getDefaultMiddleware (e.g., { immutableCheck: false, serializableCheck: false })? If yes, you must mirror those options in the manual list; otherwise the chain will unintentionally omit or duplicate checks.