# Streaming AI Responses in Laravel with Server-Sent Events

> Source: <https://dev.to/adityakdevin/streaming-ai-responses-in-laravel-with-server-sent-events-3bob>
> Published: 2026-07-16 07:49:29+00:00

In [the first post of this series](https://dev.to/adityakdevin/adding-an-ai-chatbot-to-your-laravel-app-with-the-openai-api-177f) we built a working AI chatbot in Laravel. It had one problem every user notices immediately: you send a message, then stare at a spinner for five seconds while the whole response generates.

LLMs produce text token by token. If you wait for the full completion before showing anything, you're throwing away the single biggest UX win available: **streaming**. The same answer that takes 5 seconds to finish starts appearing in ~300ms when streamed. Nothing about the model got faster — but to the user, it feels 10x faster.

In this post we'll upgrade the chatbot to stream responses with **Server-Sent Events (SSE)** — no WebSockets, no Pusher, no extra infrastructure. Just Laravel.

WebSockets are bidirectional and need a long-running server (Reverb, Soketi) or a paid service. For chat completions you only need **one direction**: server → browser, for the lifetime of one request. That's exactly what SSE is for, and since Laravel 11 it's built into the framework as `response()->eventStream()`

.

Rule of thumb: presence, typing indicators, multiplayer → WebSockets. Streaming one AI answer → SSE.

We keep the `ChatService`

from part 1 and add a streaming method. The `openai-php`

client exposes `createStreamed()`

, which returns an iterator of deltas:

``` php
<?php

namespace App\Services;

use Generator;
use OpenAI\Laravel\Facades\OpenAI;

class ChatService
{
    // ... SYSTEM_PROMPT and reply() from part 1 ...

    /**
     * @param array<int, array{role: string, content: string}> $history
     */
    public function streamReply(array $history, string $userMessage): Generator
    {
        $stream = OpenAI::chat()->createStreamed([
            'model' => 'gpt-4o-mini',
            'messages' => [
                ['role' => 'system', 'content' => self::SYSTEM_PROMPT],
                ...$history,
                ['role' => 'user', 'content' => $userMessage],
            ],
            'max_tokens' => 500,
        ]);

        foreach ($stream as $response) {
            $delta = $response->choices[0]->delta->content;

            if ($delta !== null) {
                yield $delta;
            }
        }
    }
}
```

A `Generator`

is the right return type here: the controller can forward chunks as they arrive without ever holding the full response in memory.

Laravel 11.19+ ships `response()->eventStream()`

, which handles the SSE formatting (`event:`

/ `data:`

lines) for you:

``` php
<?php

namespace App\Http\Controllers;

use App\Services\ChatService;
use Illuminate\Http\Request;

class ChatStreamController extends Controller
{
    public function __invoke(Request $request, ChatService $chat)
    {
        $validated = $request->validate([
            'message' => ['required', 'string', 'max:2000'],
        ]);

        $history = $request->session()->get('chat_history', []);

        // CRITICAL: release the session lock. A streaming response is a
        // long-lived request — with the default file/database session
        // driver it would block every other request from this user
        // (including page loads!) until the stream finishes.
        $request->session()->save();

        return response()->eventStream(function () use ($request, $chat, $history, $validated) {
            $full = '';

            foreach ($chat->streamReply($history, $validated['message']) as $chunk) {
                $full .= $chunk;
                yield $chunk;
            }

            // persist history once the stream completes
            $history[] = ['role' => 'user', 'content' => $validated['message']];
            $history[] = ['role' => 'assistant', 'content' => $full];
            $request->session()->put('chat_history', array_slice($history, -20));
            $request->session()->save();
        }, headers: [
            'X-Accel-Buffering' => 'no', // tell nginx not to buffer the stream
        ]);
    }
}
```

Route it with the same throttling as part 1:

``` php
Route::post('/chat/stream', ChatStreamController::class)
    ->middleware(['auth', 'throttle:20,1']);
```

The native `EventSource`

API only supports GET requests, and we need to POST a message body — so we read the stream with `fetch`

instead:

``` js
<script>
async function streamChat(message, botEl) {
    const res = await fetch('/chat/stream', {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            'X-CSRF-TOKEN': document.querySelector('meta[name="csrf-token"]').content,
        },
        body: JSON.stringify({ message }),
    });

    const reader = res.body.getReader();
    const decoder = new TextDecoder();
    let buffer = '';

    while (true) {
        const { done, value } = await reader.read();
        if (done) break;

        buffer += decoder.decode(value, { stream: true });

        // SSE messages are separated by a blank line
        const events = buffer.split('\n\n');
        buffer = events.pop(); // keep the incomplete tail

        for (const evt of events) {
            const data = evt.split('\n')
                .filter(l => l.startsWith('data: '))
                .map(l => l.slice(6))
                .join('\n');

            if (data && data !== '</stream>') {
                botEl.textContent += data;
            }
        }
    }
}
</script>
```

`</stream>`

is Laravel's default end-of-stream marker — filter it out (or customize it with the `endStreamWith`

argument).

That's it. Send a message and watch the answer type itself out.

This is the part most tutorials skip. Streaming works instantly on `php artisan serve`

, then mysteriously arrives all-at-once on your server. The culprit is always **buffering somewhere between PHP and the browser**:

`X-Accel-Buffering: no`

header above disables it per-response; alternatively set `proxy_buffering off;`

for the route.`output_buffering`

in `php.ini`

. Laravel's `eventStream`

flushes after every yield, but an outer buffer can still swallow it.`curl -N`

against production before blaming your code.Debug tip: `curl -N -X POST https://yourapp.test/chat/stream ...`

shows you exactly what arrives and when, with no browser magic in between.

`X-Accel-Buffering: no`

`max_execution_time`

and your web server's send timeout. Set both above your worst-case generation time (60s is a sane ceiling with `max_tokens: 500`

).Our bot streams beautifully, but it still only knows what's in its system prompt. Next up: **RAG in Laravel — embeddings and pgvector**, where we'll give it your actual documentation to answer from. Follow me to catch it.

*I'm Aditya Kumar ( adityakdevin) — Tech Lead & full-stack developer building AI-powered web products with Laravel, Vue, and LLM APIs. Find me at adityadev.in.*