sse-streaming

type	skill
lifecycle	stable
inheritance	inheritable
name	sse-streaming
description	POST-based Server-Sent Events streaming for Azure Functions — HTTP streaming, chunked response parsing, reconnection
tier	extended
applyTo	**/*sse*,**/*streaming*,**/*server-sent*,**/*real-time*
metadata	{"version":"1.0.0","category":"web-development","tags":["sse","streaming","azure-functions","http-streaming","readablestream","real-time"],"activation":{"triggers":["SSE","streaming","server-sent events","HTTP streaming","ReadableStream","chunked response","real-time"],"context":"Working on real-time streaming from Azure Functions to client"},"prerequisites":[]}
currency	2026-04-22T00:00:00.000Z

SSE Streaming

POST-based Server-Sent Events pattern for Azure Functions. Solves the gap where native EventSource (GET-only) can't send request bodies, and Azure Static Web Apps don't proxy WebSocket to the API layer.

---

Why POST-Based SSE

Option	SWA API Support?	POST body?	Limitation
WebSocket	No	N/A	SWA doesn't proxy WebSocket to Functions
EventSource	Yes	GET only	Can't send context in request body
POST + ReadableStream	Yes	Yes	Recommended pattern

---

Azure Functions Setup

Enable HTTP Streaming

// host.json
{
  "version": "2.0",
  "extensions": {
    "http": {
      "enableHttpStream": true
    }
  }
}

Streaming Function Pattern

import { app, HttpRequest, HttpResponseInit, InvocationContext } from '@azure/functions';

app.http('stream-response', {
  methods: ['POST'],
  authLevel: 'anonymous', // SWA handles auth via EasyAuth
  : ,
  :  (: , : ): <> => {
     payload =  req.();

     stream =  ({
       () {
         {
          
           aiStream =  (payload);

            ( chunk  aiStream) {
             sseData = ;
            controller.( ().(sseData));
          }

          
          controller.(
             ().()
          );
        }  (error) {
          controller.(
             ().()
          );
        }  {
          controller.();
        }
      },
    });

     {
      : ,
      : {
        : ,
        : ,
        : ,
        : , 
      },
      : stream,
    };
  },
});