Premium

Chat UI with Streaming Response

By FrontendAtlas Team · Updated Jan 31, 2026

Build a simplified ChatGPT-like interface that streams an assistant response token-by-token. The goal is to model chat state, append streaming chunks efficiently, and keep the UI responsive with clear loading/cancel states.

Render a chat layout with a scrollable message list, an input, and…
On submit, append the user message immediately and clear the input.

What you’ll build / What this tests

This premium react coding focuses on Chat UI with Streaming Response. You’ll apply react and state thinking with hard level constraints. The prompt emphasizes Build a simplified ChatGPT-like interface that streams an assistant response token-by-token. The goal is to model….

Learning goals

Translate the prompt into a clear react API signature and return shape.
Apply react, state, effects techniques to implement chat ui with streaming response.
Handle hard edge cases without sacrificing readability.
Reason about time/space complexity and trade-offs in react.

Key decisions to discuss

Define the exact input/output contract before coding.
Decide on concurrency and error propagation behavior.
Prioritize predictable edge-case handling over micro-optimizations.

Evaluation rubric

Correctness: covers required behaviors and edge cases.
Clarity: readable structure and predictable control flow.
Complexity: avoids unnecessary work for large inputs.
API discipline: no mutation of inputs; returns expected shape.
Testability: solution is easy to unit test.

Constraints / Requirements

Render a chat layout with a scrollable message list, an input, and a Send button.
On submit, append the user message immediately and clear the input.
Append an assistant message placeholder and stream chunks into it over time.
Disable Send while streaming and show a streaming indicator.
Provide a Stop button to cancel the stream and keep the partial response.
User messages appear instantly after submit.
Assistant messages grow incrementally as chunks arrive.
Send is disabled while streaming and re-enabled when the stream finishes or is stopped.
Stopping the stream halts further updates and leaves the partial text visible.
Clearing the input does not affect existing messages.

Mini snippet (usage only)

// Example usage
const input = /* chat ui with streaming response input */;
const result = solve(input);
console.log(result);

// Edge case check
const empty = input ?? null;
const fallback = solve(input);
console.log(fallback);

// Expected: describe output shape, not the implementation
// (no solution code in preview)

Common pitfalls

Mutating inputs instead of returning a new value.
Skipping edge cases like empty input, duplicates, or nulls.
Overlooking time complexity for large inputs.