Together Chat API

An authenticated chat API on Render, backed by Together AI chat completions. Express accepts a bearer token and a message, calls Together, and returns the reply, model ID, and token usage.

What This Demo Shows

This repo is the TypeScript path from Together's Build a chat API on Render guide. server.ts matches that guide. The landing page and model picker live in src/ui/ so the documented handler stays small.

Platform	Role
Render Web Services	Hosts the Express API, health checks, and landing page on 0.0.0.0:$PORT
Together AI	Chat completions, plus GET /models for the picker
CHAT_API_KEY	Separate bearer token for POST /chat, so the Together key never leaves the server

Python sibling: together-render-chat-python.

How It Works

1. Browser loads chat/language/code models from GET /ui/models (Together's live catalog) and sends the thread to POST /ui/chat with the selected model.
2. A trusted API client calls documented POST /chat with Authorization: Bearer $CHAT_API_KEY. That route always uses TOGETHER_MODEL.
3. Express validates the body, then calls https://api.together.ai/v1/chat/completions (60 second timeout).
4. The service returns { model, reply, usage }, or an explicit 401 / 400 / 502 / 504.

The service stores no chat history. The browser keeps the thread in memory.

Image, embedding, moderation, and rerank models are omitted from the picker: this demo only calls chat completions.

Quick Start

Prerequisites

• Render account
• Together AI account with an active credit balance and a project API key
• A caller secret: openssl rand -hex 32 (this becomes CHAT_API_KEY, not the Together key)

Deploy

1. Click Deploy to Render above
2. You'll be prompted for:
   • TOGETHER_API_KEY — Get one here
   • CHAT_API_KEY — the hex secret you generated
3. Wait until the service is Live
4. Open the web service URL, pick a model, and send a message

Features

Feature	Description
Authenticated chat	POST /chat compares the bearer token with timingSafeEqual
Model picker	The page lists Together text models from GET /v1/models
Browser thread	The landing page sends conversation history to POST /ui/chat
Request inspector	After each reply, the right pane shows JSON, token usage, and a POST /chat curl
Public health check	GET /health is unauthenticated so Render can probe it
Upstream mapping	Together 4xx/5xx become 502; 60s timeouts become 504

Configuration

Variable	Where	Description
TOGETHER_API_KEY	Web service	Together project API key
CHAT_API_KEY	Web service	Bearer token for POST /chat
TOGETHER_MODEL	Web service	Default picker value and the only model POST /chat uses (Qwen/Qwen3.5-9B)
PORT	Web service	Set by Render; the server binds 0.0.0.0:$PORT

Warning

Do not embed CHAT_API_KEY in browser or mobile app code. The shared token is a server-to-server guard for this demo. The landing page uses POST /ui/chat for that reason.

Project Structure

server.ts            Documented Express /health and /chat handler
src/index.ts         Listen, static files, mounts UI routes
src/ui/              Model catalog + /ui/chat
public/              Landing page
public/js/           Browser chat + model picker
render.yaml          Render Blueprint
package.json         Node 22–24, Express 5

API Routes

Method	Path	Description
GET	/	Landing page
GET	/health	{ ok, model } using TOGETHER_MODEL
POST	/chat	Single-turn chat. Requires Authorization: Bearer $CHAT_API_KEY and {"message":"..."}
GET	/ui/models	{ default, models } from Together GET /v1/models
POST	/ui/chat	Multi-turn helper. Body is {"model":"...","messages":[{"role","content"}, ...]}

export SERVICE_URL="https://together-chat-ts-xxxx.onrender.com"

curl "$SERVICE_URL/health"

read -s CHAT_API_KEY
export CHAT_API_KEY

curl -X POST "$SERVICE_URL/chat" \
  -H "Authorization: Bearer $CHAT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"message":"In one sentence, what is a vector database?"}'

unset CHAT_API_KEY

Troubleshooting

Problem	Solution
Deploy asks for secrets	TOGETHER_API_KEY and CHAT_API_KEY are sync: false. Enter them on first Blueprint apply.
Health check fails	Confirm the process listens on 0.0.0.0 and PORT, and that both secrets are set so the process can start.
401 on /chat	Send Authorization: Bearer plus the same CHAT_API_KEY value stored on the service.
502 with upstreamStatus	Together rejected the call. Check the key, model ID, and Together credit balance.
Picker only shows the default model	Together GET /models failed. Check TOGETHER_API_KEY and Together status.
Image model missing from the picker	This demo only lists chat, language, and code models.
Follow-ups forget earlier turns	Use the landing page (POST /ui/chat). Documented POST /chat is single-turn.

Learn More

Render:

• Render Web Services
• Deploy to Render button
• Render Developers Discord

Together AI:

• Build a chat API on Render
• Chat completions
• List models
• Together AI Discord

License

MIT