Diagnosing State Persistence Failures in Reflex

In Reflex, state persistence allows user data—such as theme preferences or form progress—to survive a page refresh or browser navigation. When state variables revert to their initial values after a reload, the persistence mechanism is failing. This typically stems from a missing configuration flag or the use of data types that cannot be serialized into JSON for browser storage.

Identifying the Failure Mode

Use the following table to match your observed behavior to the most likely cause:

Symptom	Likely Cause
Values reset to defaults immediately after page refresh.	The persist = True flag is missing from the State class.
State updates during the session but disappears after reload.	The state contains non-serializable objects (e.g., custom classes, lambdas).
Persistence works for some fields but fails for others.	Nested structures contain non-serializable types.
App behaves unpredictably or crashes after a state variable change.	Schema mismatch between stored local storage and current code.

Step 1: Verify the Persistence Flag

Reflex does not persist state by default to minimize browser resource usage. You must explicitly enable this behavior in your State subclass.

Check your state definition for the persist attribute:

class MyState(rx.State):
    persist = True  # Required for local storage syncing
    count: int = 0

If this flag is omitted, the state exists only in the server-side session memory and is purged when the browser connection is reset.

Step 2: Audit Data Serializability

Reflex persists state by serializing it to JSON. If a state variable contains an object that cannot be converted to a JSON string, the persistence process will fail. This often happens silently or manifests as a serialization error in the server logs.

Supported Types

• Primitives: int, float, str, bool
• Collections: list and dict (provided all nested elements are also supported)

Unsupported Types

• Custom class instances (e.g., a User object from a database model)
• Functions, lambdas, or method references
• Open file handles or active network sockets
• Complex NumPy arrays or Pandas DataFrames

Example: Converting Custom Objects to Serializable Formats

If you need to persist a complex object, store it as a dictionary and reconstruct the object in your event handlers.

# INCORRECT: This will break persistence
class BadState(rx.State):
    persist = True
    user_profile: UserProfile = UserProfile(name="Alice")

# CORRECT: Use a dictionary for the persisted field
class GoodState(rx.State):
    persist = True
    user_profile: dict = {"name": "Alice", "role": "admin"}

Step 3: Inspect Browser Local Storage

If the configuration is correct but values still reset, verify if the data is actually reaching the browser.

1. Open your application in a web browser.
2. Open Developer Tools (F12 or Right-click > Inspect).
3. Navigate to the Application tab.
4. Select Local Storage from the left-hand sidebar.
5. Look for a key prefixed with your state class name (e.g., rx-MyState).

If the key is missing after you have interacted with the UI, the server is not triggering the sync. Check your terminal for SerializationError messages.

Handling Schema Mismatches

Changing the type of a persisted variable (e.g., changing count: int to count: str) creates a conflict between the data stored in the user's browser and the new code definition. This can lead to runtime errors.

To resolve this, you must clear the stale data. You can do this by:

• Manually clearing the Local Storage in the browser developer tools.
• Implementing a versioning key in your state that triggers a reset when the version increments.

Escalation and Debugging

If persistence fails after verifying the flag and serializability, enable debug mode to surface hidden errors:

Run your app with the environment variable REFLEX_DEBUG=1. Inspect the browser console and server logs for specific serialization tracebacks. If the issue persists, provide the State definition and your Reflex version when reporting the issue to the repository.

Verification Process

To confirm the fix is working:

1. Interact with the app to change a persisted state value.
2. Verify the rx-StateName key in the browser's Local Storage reflects the change.
3. Reload the page (F5) and confirm the UI displays the updated value rather than the default.
4. Toggle persist = False and verify the value resets upon reload to confirm the flag is the controlling mechanism.