Non-streaming chat

Build reliable chat integrations with complete response patterns for batch processing and simple UIs

Overview

Build a chat integration that receives complete responses after processing, perfect for batch processing, simple UIs, or when you need the full response before proceeding. Ideal for integrations where real-time display isn’t essential.

What You’ll Build:

Simple request-response chat patterns with immediate complete responses
Context management using previousChatId for linked conversations
Basic integration with predictable response timing

For comprehensive context management options including sessions, see Session management.

Prerequisites

Completed Chat quickstart tutorial
Understanding of basic HTTP requests and JSON handling
Familiarity with JavaScript/TypeScript promises or async/await

Scenario

We’ll build a help desk system for “TechFlow” that processes support messages through text chat and maintains conversation history using previousChatId.

1. Basic Non-Streaming Implementation

Create a simple chat function

Start with a basic non-streaming chat implementation:

Basic Non-Streaming Request

$ curl -X POST https://api.vapi.ai/chat \
>   -H "Authorization: Bearer YOUR_API_KEY" \
>   -H "Content-Type: application/json" \
>   -d '{
>     "assistantId": "your-assistant-id",
>     "input": "I need help resetting my password"
>   }'

Understand the response structure

Non-streaming responses come back as complete JSON objects:

Complete Chat Response

1 {
2   "id": "chat_123456",
3   "orgId": "org_789012",
4   "assistantId": "assistant_345678",
5   "name": "Password Reset Help",
6   "sessionId": "session_901234",
7   "messages": [
8     {
9       "role": "user",
10       "content": "I need help resetting my password"
11     }
12   ],
13   "output": [
14     {
15       "role": "assistant",
16       "content": "I can help you reset your password. First, let me verify your account information..."
17     }
18   ],
19   "createdAt": "2024-01-15T09:30:00Z",
20   "updatedAt": "2024-01-15T09:30:01Z"
21 }

Implement in TypeScript

Create a reusable function for non-streaming chat:

non-streaming-chat.ts

1 async function sendChatMessage(
2   message: string, 
3   previousChatId?: string
4 ): Promise<{ chatId: string; response: string }> {
5   const response = await fetch('https://api.vapi.ai/chat', {
6     method: 'POST',
7     headers: {
8       'Authorization': 'Bearer YOUR_API_KEY',
9       'Content-Type': 'application/json'
10     },
11     body: JSON.stringify({
12       assistantId: 'your-assistant-id',
13       input: message,
14       ...(previousChatId && { previousChatId })
15     })
16   });
17 
18   const chat = await response.json();
19   return {
20     chatId: chat.id,
21     response: chat.output[0].content
22   };
23 }

2. Context Management with previousChatId

Link chats for conversation context

Use previousChatId to maintain context across multiple chats:

conversation-chain.ts

1 async function createConversation() {
2   let lastChatId: string | undefined;
3 
4   async function sendMessage(input: string): Promise<string> {
5     const response = await fetch('https://api.vapi.ai/chat', {
6       method: 'POST',
7       headers: {
8         'Authorization': 'Bearer YOUR_API_KEY',
9         'Content-Type': 'application/json'
10       },
11       body: JSON.stringify({
12         assistantId: 'your-assistant-id',
13         input: input,
14         ...(lastChatId && { previousChatId: lastChatId })
15       })
16     });
17 
18     const chat = await response.json();
19     lastChatId = chat.id;
20     return chat.output[0].content;
21   }
22 
23   return { sendMessage };
24 }
25 
26 // Usage
27 const conversation = await createConversation();
28 
29 const response1 = await conversation.sendMessage("Hello, I'm Alice");
30 console.log(response1);
31 
32 const response2 = await conversation.sendMessage("What's my name?");
33 console.log(response2); // Should remember "Alice"

3. Custom Assistant Configuration

Use inline assistant configuration

Instead of pre-created assistants, define configuration per request:

Custom Assistant Request

$ curl -X POST https://api.vapi.ai/chat \
>   -H "Authorization: Bearer YOUR_API_KEY" \
>   -H "Content-Type: application/json" \
>   -d '{
>     "input": "I need help with enterprise features",
>     "assistant": {
>       "model": {
>         "provider": "openai",
>         "model": "gpt-4o",
>         "temperature": 0.7,
>         "messages": [
>           {
>             "role": "system",
>             "content": "You are a helpful technical support agent specializing in enterprise features."
>           }
>         ]
>       }
>     }
>   }'

Create specialized chat handlers

Build different chat handlers for different types of requests:

specialized-handlers.ts

1 async function createSpecializedChat(systemPrompt: string) {
2   return async function(userInput: string): Promise<string> {
3     const response = await fetch('https://api.vapi.ai/chat', {
4       method: 'POST',
5       headers: {
6         'Authorization': 'Bearer YOUR_API_KEY',
7         'Content-Type': 'application/json'
8       },
9       body: JSON.stringify({
10         input: userInput,
11         assistant: {
12           model: {
13             provider: 'openai',
14             model: 'gpt-4o',
15             temperature: 0.3,
16             messages: [{ role: 'system', content: systemPrompt }]
17           }
18         }
19       })
20     });
21 
22     const chat = await response.json();
23     return chat.output[0].content;
24   };
25 }
26 
27 const technicalSupport = await createSpecializedChat(
28   "You are a technical support specialist. Ask clarifying questions and provide step-by-step troubleshooting."
29 );
30 
31 const billingSupport = await createSpecializedChat(
32   "You are a billing support specialist. Be precise about billing terms and always verify account information."
33 );
34 
35 // Usage
36 const techResponse = await technicalSupport("My API requests are returning 500 errors");
37 const billingResponse = await billingSupport("I was charged twice this month");

Next Steps

Enhance your non-streaming chat system further:

Add streaming capabilities - Upgrade to real-time responses for better UX
OpenAI compatibility - Use familiar OpenAI SDK patterns
Integrate tools - Enable your assistant to call external APIs and databases
Session management - Learn about advanced context management with sessions
Add voice capabilities - Extend your text chat to voice interactions

Need help? Chat with the team on our Discord or mention us on X/Twitter.

$	curl -X POST https://api.vapi.ai/chat \
>	-H "Authorization: Bearer YOUR_API_KEY" \
>	-H "Content-Type: application/json" \
>	-d '{
>	"assistantId": "your-assistant-id",
>	"input": "I need help resetting my password"
>	}'

1	{
2	"id": "chat_123456",
3	"orgId": "org_789012",
4	"assistantId": "assistant_345678",
5	"name": "Password Reset Help",
6	"sessionId": "session_901234",
7	"messages": [
8	{
9	"role": "user",
10	"content": "I need help resetting my password"
11	}
12	],
13	"output": [
14	{
15	"role": "assistant",
16	"content": "I can help you reset your password. First, let me verify your account information..."
17	}
18	],
19	"createdAt": "2024-01-15T09:30:00Z",
20	"updatedAt": "2024-01-15T09:30:01Z"
21	}

1	async function sendChatMessage(
2	message: string,
3	previousChatId?: string
4	): Promise<{ chatId: string; response: string }> {
5	const response = await fetch('https://api.vapi.ai/chat', {
6	method: 'POST',
7	headers: {
8	'Authorization': 'Bearer YOUR_API_KEY',
9	'Content-Type': 'application/json'
10	},
11	body: JSON.stringify({
12	assistantId: 'your-assistant-id',
13	input: message,
14	...(previousChatId && { previousChatId })
15	})
16	});
17
18	const chat = await response.json();
19	return {
20	chatId: chat.id,
21	response: chat.output[0].content
22	};
23	}

1	async function createConversation() {
2	let lastChatId: string \| undefined;
3
4	async function sendMessage(input: string): Promise<string> {
5	const response = await fetch('https://api.vapi.ai/chat', {
6	method: 'POST',
7	headers: {
8	'Authorization': 'Bearer YOUR_API_KEY',
9	'Content-Type': 'application/json'
10	},
11	body: JSON.stringify({
12	assistantId: 'your-assistant-id',
13	input: input,
14	...(lastChatId && { previousChatId: lastChatId })
15	})
16	});
17
18	const chat = await response.json();
19	lastChatId = chat.id;
20	return chat.output[0].content;
21	}
22
23	return { sendMessage };
24	}
25
26	// Usage
27	const conversation = await createConversation();
28
29	const response1 = await conversation.sendMessage("Hello, I'm Alice");
30	console.log(response1);
31
32	const response2 = await conversation.sendMessage("What's my name?");
33	console.log(response2); // Should remember "Alice"

1	async function createSpecializedChat(systemPrompt: string) {
2	return async function(userInput: string): Promise<string> {
3	const response = await fetch('https://api.vapi.ai/chat', {
4	method: 'POST',
5	headers: {
6	'Authorization': 'Bearer YOUR_API_KEY',
7	'Content-Type': 'application/json'
8	},
9	body: JSON.stringify({
10	input: userInput,
11	assistant: {
12	model: {
13	provider: 'openai',
14	model: 'gpt-4o',
15	temperature: 0.3,
16	messages: [{ role: 'system', content: systemPrompt }]
17	}
18	}
19	})
20	});
21
22	const chat = await response.json();
23	return chat.output[0].content;
24	};
25	}
26
27	const technicalSupport = await createSpecializedChat(
28	"You are a technical support specialist. Ask clarifying questions and provide step-by-step troubleshooting."
29	);
30
31	const billingSupport = await createSpecializedChat(
32	"You are a billing support specialist. Be precise about billing terms and always verify account information."
33	);
34
35	// Usage
36	const techResponse = await technicalSupport("My API requests are returning 500 errors");
37	const billingResponse = await billingSupport("I was charged twice this month");