Loss of Stream State on Navigation

Oct 13, 2025 by pinkandtrash.com 29 views

Problem Description

Currently, hooks like useStream and useMessageStream are used inside components that unmount and remount during navigation. This causes state inconsistencies and stale event handlers, leading to several issues.

Main Scenario

1. A user enters a route with a component (e.g., `Chat.tsx`) that uses the `useStream` hook.

The component binds startStreaming to an input form submit handler.

2. The user inputs a message and presses Enter.

In the form handler:

(1) A session is created.
(2) The user is redirected to /sessions/{id} via a React route.

3. The new page also mounts `Chat.tsx`, which creates a new instance of `useStream`.

4. The `startStreaming()` function is then invoked, but it is still associated with the previous (now unmounted) `Chat.tsx` instance.

5. The events are streamed to the old `Chat.tsx` component, so the new instance does not receive any events.

🚨 Key Problems

- Loss of Stream State on Navigation

Since useStream is created inside Chat.tsx, it resets when the component unmounts. The new Chat.tsx has no connection to the previous event stream, causing lost messages.

- Stale Component Instances Handling Events

The previous Chat.tsx instance remains in memory for a short time. When the user submits a message, the old handleSubmit event handler is invoked, binding startStreaming to the unmounted instance. Events are sent to the old Chat component, and the new one does not reflect them.

- Multiple Instances of `useStream` Running in Parallel

When useStream is used both directly and within other hooks like useMessageStream, multiple independent instances may exist. This results in state mismatches across different parts of the app.

Proposed Solution: Create `useStreamContext` in a Context (`StreamProvider`)

To ensure that streaming is persistent across navigation, we should manage useStream at a higher level using React Context. This ensures:

State persists across route changes.
Only one instance of useStream is used throughout the app.
All components using useStream or useMessageStream share the same state.

Benefits of Using React Context

Using React Context to manage useStream provides several benefits:

Global State Management: React Context allows us to manage global state, ensuring that all components have access to the same data.
Decoupling: By managing useStream at a higher level, we decouple the component from the stream, making it easier to manage and maintain.
Reusability: React Context enables us to reuse the same stream instance across multiple components, reducing code duplication and improving maintainability.

Implementing `useStreamContext`

To implement useStreamContext, we need to create a new context, StreamProvider, and a hook, useStreamContext. The StreamProvider context will manage the useStream instance, and the useStreamContext hook will provide access to the stream instance.

// StreamProvider.ts
import { createContext, useState, useEffect } from 'react';

const StreamContext = createContext();

const StreamProvider = ({ children }) => {
  const [stream, setStream] = useState(null);

  useEffect(() => {
    // Initialize the stream instance
    const initStream = async () => {
      const streamInstance = await createStreamInstance();
      setStream(streamInstance);
    };
    initStream();
  }, []);

  return (
    <StreamContext.Provider value={stream}>
      {children}
    </StreamContext.Provider>
  );
};

export { StreamProvider, StreamContext };

// useStreamContext.ts
import { useContext } from 'react';
import { StreamContext } from './StreamProvider';

const useStreamContext = () => {
  const stream = useContext(StreamContext);
  return stream;
};

export { useStreamContext };

Using `useStreamContext` in Components

To use useStreamContext in components, we need to wrap the component with the StreamProvider context and use the useStreamContext hook to access the stream instance.

// Chat.tsx
import { useStreamContext } from './useStreamContext';

const Chat = () => {
  const stream = useStreamContext();

  useEffect(() => {
    // Bind the startStreaming function to the input form submit handler
    const handleSubmit = async (event) => {
      event.preventDefault();
      const message = event.target.message.value;
      await stream.startStreaming(message);
    };
    document.getElementById('form').addEventListener('submit', handleSubmit);
  }, [stream]);

  return (
    <form id="form">
      <input type="text" id="message" />
      <button type="submit">Send</button>
    </form>
  );
};

export default Chat;

By using React Context to manage useStream, we ensure that streaming is persistent across navigation, and all components using useStream or useMessageStream share the same state.

Conclusion

Q: What is the main problem with using useStream and useMessageStream inside components that unmount and remount during navigation?

A: The main problem is that state inconsistencies and stale event handlers are caused, leading to several issues such as loss of stream state on navigation, stale component instances handling events, and multiple instances of useStream running in parallel.

Q: What is the proposed solution to ensure that streaming is persistent across navigation?

A: The proposed solution is to manage useStream at a higher level using React Context. This ensures that state persists across route changes, only one instance of useStream is used throughout the app, and all components using useStream or useMessageStream share the same state.

Q: What are the benefits of using React Context to manage useStream?

A: The benefits of using React Context to manage useStream include global state management, decoupling, and reusability. By managing useStream at a higher level, we can ensure that all components have access to the same data, decouple the component from the stream, and reuse the same stream instance across multiple components.

Q: How do I implement useStreamContext using React Context?

A: To implement useStreamContext, you need to create a new context, StreamProvider, and a hook, useStreamContext. The StreamProvider context will manage the useStream instance, and the useStreamContext hook will provide access to the stream instance.

// StreamProvider.ts
import { createContext, useState, useEffect } from 'react';

const StreamContext = createContext();

const StreamProvider = ({ children }) => {
  const [stream, setStream] = useState(null);

  useEffect(() => {
    // Initialize the stream instance
    const initStream = async () => {
      const streamInstance = await createStreamInstance();
      setStream(streamInstance);
    };
    initStream();
  }, []);

  return (
    <StreamContext.Provider value={stream}>
      {children}
    </StreamContext.Provider>
  );
};

export { StreamProvider, StreamContext };

// useStreamContext.ts
import { useContext } from 'react';
import { StreamContext } from './StreamProvider';

const useStreamContext = () => {
  const stream = useContext(StreamContext);
  return stream;
};

export { useStreamContext };

Q: How do I use useStreamContext in components?

A: To use useStreamContext in components, you need to wrap the component with the StreamProvider context and use the useStreamContext hook to access the stream instance.

// Chat.tsx
import { useStreamContext } from './useStreamContext';

const Chat = () => {
  const stream = useStreamContext();

  useEffect(() => {
    // Bind the startStreaming function to the input form submit handler
    const handleSubmit = async (event) => {
      event.preventDefault();
      const message = event.target.message.value;
      await stream.startStreaming(message);
    };
    document.getElementById('form').addEventListener('submit', handleSubmit);
  }, [stream]);

  return (
    <form id="form">
      <input type="text" id="message" />
      <button type="submit">Send</button>
    </form>
  );
};

export default Chat;

Q: What are the advantages of using React Context to manage useStream?

A: The advantages of using React Context to manage useStream include:

Improved maintainability: By managing useStream at a higher level, we can ensure that all components have access to the same data, reducing code duplication and improving maintainability.
Better scalability: By reusing the same stream instance across multiple components, we can improve the scalability of our application.
Easier debugging: By managing useStream at a higher level, we can easily debug and troubleshoot issues related to streaming.

Q: What are the common mistakes to avoid when using React Context to manage useStream?

A: Some common mistakes to avoid when using React Context to manage useStream include:

Not properly initializing the stream instance: Make sure to properly initialize the stream instance in the StreamProvider context.
Not using the useStreamContext hook correctly: Make sure to use the useStreamContext hook correctly in components to access the stream instance.
Not handling errors properly: Make sure to handle errors properly when using React Context to manage useStream.

By following these best practices and avoiding common mistakes, you can effectively use React Context to manage useStream and ensure that streaming is persistent across navigation.