REST API - Layercode

Authorize Client Session

To connect a client (browser or mobile app) to a Layercode voice agent, you must first authorize the session. This is done by calling the Layercode REST API endpoint below from your backend. How the authorization flow works: When using a Layercode frontend SDK (such as @layercode/react-sdk or @layercode/js-sdk), the SDK will automatically make a POST request to the authorizeSessionEndpoint URL that you specify in your frontend code. This authorizeSessionEndpoint should be an endpoint on your own backend (not Layercode’s). Your backend receives this request from the frontend, then securely calls the Layercode REST API (https://api.layercode.com/v1/agents/web/authorize_session) using your LAYERCODE_API_KEY. Your backend then returns the client_session_key to the frontend.

Your Layercode API key should never be exposed to the frontend. Always call this endpoint from your backend, then return the client_session_key to your frontend.

Endpoint

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POST https://api.layercode.com/v1/agents/web/authorize_session

Headers

Authorization

string

required

Bearer token using your LAYERCODE_API_KEY.

Content-Type

string

default:"application/json"

required

Must be application/json.

Request Body

agent_id

string

required

The ID of the Layercode agent the client should connect to.

conversation_id

string

(Optional) The conversation ID to resume an existing conversation. If not provided, a new conversation will be created.

config

object

(Optional) Per-session pipeline configuration override. When provided, it is stored on the session and takes precedence over the agent’s saved config for that session. Use this to customize the config options (e.g. the TTS voice).

Response

client_session_key

string

required

The key your frontend uses to connect to the Layercode WebSocket API.

conversation_id

string

required

The unique conversation ID.

config

object

Optional configuration for this session used by the frontend SDK. When present, it can include:
transcription.trigger and VAD settings such as vad.enabled, vad.gate_audio, vad.buffer_frames, vad.model, vad.positive_speech_threshold, vad.negative_speech_threshold, vad.redemption_frames, vad.min_speech_frames, vad.pre_speech_pad_frames, vad.frame_samples.

Example Request

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# Example with only agent_id (creates a new session)
curl -X POST https://api.layercode.com/v1/agents/web/authorize_session \
  -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"agent_id": "ag-123456"}'

# Example with agent_id and conversation_id (resumes an existing conversation)
curl -X POST https://api.layercode.com/v1/agents/web/authorize_session \
  -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"agent_id": "ag-123456", "conversation_id": "lc_conv_abc123..."}'

# Example with per-session config
curl -X POST https://api.layercode.com/v1/agents/web/authorize_session \
  -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "agent_id": "ag-123456",
    "config": {
      "type": "voice",
      "clients": {
        "browser": {
          "enabled": true
        }
      },
      "plugins": [
        { "use": "stt.deepgram", "options": { "model_id": "flux" } },
        { "use": "turn_manager", "options": { "mode": "automatic" } },
        { "use": "agent.llm", "options": { "provider": "google", "model_id": "gemini-2.5-flash-lite" } },
        { "use": "tts.rime", "options": { "model_id": "mistv2", "voice_id": "courtney" } }
      ],
      "session_webhook": {
        "url": "https://example.com/session-webhook",
        "events": ["session.start", "session.end", "session.update"],
        "custom_metadata": { "tenant_id": "t_42", "plan": "enterprise" },
        "custom_headers": { "x-tenant-id": "t_42", "x-session-origin": "mobile" }
      }
    }
  }'

Example Response

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{
  "client_session_key": "lc_sesskey_abc123...",
  "conversation_id": "lc_conv_abc123..."
}

Error Responses

error

string

required

Error message describing the problem.

Possible error cases:

400 – Invalid or missing bearer token, invalid agent ID, missing or invalid conversation ID.
402 – Insufficient balance for the organization.

Example error response:

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{
  "error": "insufficient balance"
}

Example: Backend Endpoint (Next.js)

Here’s how you might implement an authorization endpoint in your backend (Next.js example):

Next.js app/api/authorize/route.ts

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export const dynamic = 'force-dynamic';
import { NextResponse } from 'next/server';

export const POST = async (request: Request) => {
  // Here you could do any user authorization checks you need for your app
  const endpoint = 'https://api.layercode.com/v1/agents/web/authorize_session';
  const apiKey = process.env.LAYERCODE_API_KEY;
  if (!apiKey) {
    throw new Error('LAYERCODE_API_KEY is not set.');
  }
  const requestBody = await request.json();
  if (!requestBody || !requestBody.agent_id) {
    throw new Error('Missing agent_id in request body.');
  }
  try {
    const response = await fetch(endpoint, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${apiKey}`
      },
      body: JSON.stringify(requestBody)
    });
    if (!response.ok) {
      const text = await response.text();
      throw new Error(text || response.statusText);
    }
    return NextResponse.json(await response.json());
  } catch (error: any) {
    console.log('Layercode authorize session response error:', error.message);
    return NextResponse.json({ error: error.message }, { status: 500 });
  }
};

For other backend frameworks (Express, FastAPI, etc.), the logic is the same: receive a request from your frontend, call the Layercode authorize_session endpoint with your API key, and return the client_session_key to your frontend.

Agents

List Agents

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GET https://api.layercode.com/v1/agents

Authorization

string

required

Bearer token using your LAYERCODE_API_KEY.

Response

Returns all agents.

agents

array

required

Each agent object includes id, name, type, agent_template_id, created_at, updated_at, and assigned_phone_numbers (array of phone number assignments with phone_number, twilio_sid, friendly_name, assigned_at).

Example

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curl -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  https://api.layercode.com/v1/agents

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{
  "agents": [
    {
      "id": "ag-123456",
      "name": "My Agent ag-123456",
      "type": "voice",
      "agent_template_id": "tmpl_default",
      "created_at": "2024-04-01T12:00:00.000Z",
      "updated_at": "2024-04-08T16:30:16.000Z",
      "assigned_phone_numbers": [
        {
          "phone_number": "+15551234567",
          "twilio_sid": "PNxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
          "friendly_name": "Support Line",
          "assigned_at": "2024-04-02T09:21:00.000Z"
        }
      ]
    }
  ]
}

Create Agent From Template

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POST https://api.layercode.com/v1/agents

Authorization

string

required

Bearer token using your LAYERCODE_API_KEY.

Content-Type

string

default:"application/json"

required

Must be application/json.

template_id

string

Optional template ID to initialize the agent configuration. If omitted, the default recommended template is used.

name

string

Optional display name for the new agent. If omitted, Layercode assigns a default name (e.g., My Agent ag-123456).

Response

Returns the newly created agent record, including configuration and webhook secret.

string

required

Unique identifier for the agent.

name

string

required

Human-friendly name assigned by Layercode.

type

string

required

Agent type (currently voice).

config

object

required

Full pipeline configuration cloned from the template.

webhook_secret

string

required

Secret used to validate incoming webhooks.

agent_template_id

string

required

ID of the template used to create the agent.

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curl -X POST https://api.layercode.com/v1/agents \
  -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "template_id": "tmpl_sales", "name": "Sales Assistant" }'

Get Agent Details

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GET https://api.layercode.com/v1/agents/{agent_id}

Authorization

string

required

Bearer token using your LAYERCODE_API_KEY.

Response

Returns the agent.

string

required

Agent ID.

name

string

required

Agent display name.

config

object

required

Current pipeline configuration.

assigned_phone_numbers

array

Array of phone number assignments for this agent.

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curl -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  https://api.layercode.com/v1/agents/ag-123456

Update Agent Configuration

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POST https://api.layercode.com/v1/agents/{agent_id}

Authorization

string

required

Bearer token using your LAYERCODE_API_KEY.

Content-Type

string

default:"application/json"

required

Must be application/json.

webhook_url

string

URL for production webhooks. When provided, agent.llm is swapped for agent.webhook (disabling demo_mode and routing traffic to your backend).

name

string

Optional display name to set for this agent. If omitted, the name remains unchanged.

name

string

Optional display name to set for this agent. If omitted, the name remains unchanged.

Response

Returns the updated agent record with the new configuration.

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curl -X POST https://api.layercode.com/v1/agents/ag-123456 \
  -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "webhook_url": "https://example.com/layercode-webhook"
  }'

Sessions

Get Session Details

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GET https://api.layercode.com/v1/agents/{agent_id}/sessions/{session_id}

Authorization

string

required

Bearer token using your LAYERCODE_API_KEY.

Response

Returns JSON with details about the session, transcript, and recording status.

session_id

string

required

Connection ID for the session.

agent_id

string

required

ID of the agent.

started_at

string

ISO timestamp when the connection started.

ended_at

string

ISO timestamp when the connection ended (if ended).

duration_ms

number

Total connection duration in milliseconds.

metadata

object

Custom metadata associated with the session.

from_phone_number

string

Caller phone number (Twilio), if applicable.

from_phone_country

string

Caller country code (Twilio), if applicable.

to_phone_number

string

Agent phone number (Twilio), if applicable.

to_phone_country

string

Agent phone number country code (Twilio), if applicable.

ip_address

string

IP address of the connection.

country_code

string

Country code derived from IP address when available.

transcription_duration_seconds

number

Total seconds of user speech.

tts_duration_seconds

number

Total seconds of generated speech.

latency_ms

number

Processing latency in milliseconds.

transcript

array

Array of transcript entries. Each entry includes: timestamp, user_message, assistant_message, latency_ms.

recording_status

string

One of not_available, in_progress, completed.

recording_url

string

If recording_status is completed, a URL to download the WAV recording for this session connection.

Example

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curl -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  https://api.layercode.com/v1/agents/ag-123456/sessions/lc_conn_abc123

Download Session Recording

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GET https://api.layercode.com/v1/agents/{agent_id}/sessions/{session_id}/recording

Authorization

string

required

Bearer token using your LAYERCODE_API_KEY.

Returns a WAV audio file if available.

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curl -L -H "Authorization: Bearer $LAYERCODE_API_KEY" \
  -o session.wav \
  https://api.layercode.com/v1/agents/ag-123456/sessions/lc_conn_abc123/recording

Recordings are generated after a session completes. If a recording is still processing, the details endpoint will return recording_status: “in_progress”.

Once your frontend receives the client_session_key, it can connect to the Layercode WebSocket API to start streaming audio.

Calls

Initiate Outbound Call

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POST https://api.layercode.com/v1/agents/ag-123456/calls/initiate_outbound

from_phone_number

string

required

The phone number assigned to your Layercode Agent that will make the call.

Remember: the from_phone_number must be a number already assigned to your Laycode Agent in the dashboard.

to_phone_number

string

required

The phone number to call (e.g., your mobile number for testing).

Response

conversation_id

string

required

The unique conversation ID.

A Session (associated with the returned conversation_id) will be created shortly after once Twilio initiates the call)

Example Request

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  curl -X POST https://api.layercode.com/v1/agents/ag-123456/calls/initiate_outbound \
  -H 'Authorization: Bearer $LAYERCODE_API_KEY' \
  -H 'Content-Type: application/json' \
  -D '{
      "from_phone_number": "NUMBER_ASSIGNED_TO_YOUR_AGENT",
      "to_phone_number": "PHONE_NUMBER_TO_CALL"
  }'

Example Response

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{
  "conversation_id": "lc_conv_abc123..."
}

Error Responses

error

string

required

Error message describing the problem.

Possible error cases:

400 – Invalid or missing bearer token, missing or request body, invalid from_phone_number (i.e. not assigned to the agent specified in the url).
429 – Account session concurrency limit reached.
402 – Insufficient balance for the organization.

Twilio Voice

TwiML Webhook

Use this endpoint as the Voice webhook in your Twilio phone number configuration. Layercode validates the incoming request, authorizes a session, and returns TwiML that connects the call to your agent’s WebSocket stream.

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POST https://api.layercode.com/v1/agents/twilio/twiml

X-Twilio-Signature

string

Signature supplied by Twilio for request verification. Required when you have stored Twilio credentials in Layercode.

Direction

string

required

Call direction reported by Twilio (e.g., inbound or outbound-api).

From

string

required

Caller phone number.

FromCountry

string

Caller country code supplied by Twilio.

string

required

Phone number assigned to your agent.

ToCountry

string

Destination country code supplied by Twilio.

Response

Returns TwiML that streams the call to the Layercode Twilio WebSocket endpoint.

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<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Connect>
    <Stream url="wss://twilio.layercode.com/v1/agents/twilio/websocket/{client_session_key}" />
  </Connect>
</Response>

The response Streaming URL is generated dynamically for each request. Do not cache or reuse the client session key.

API

​Authorize Client Session

​Endpoint

​Headers

​Request Body

​Response

​Example Request

​Example Response

​Error Responses

​Example: Backend Endpoint (Next.js)

​Agents

​List Agents

​Response

​Example

​Create Agent From Template

​Response

​Get Agent Details

​Response

​Update Agent Configuration

​Response

​Sessions

​Get Session Details

​Response

​Example

​Download Session Recording

​Calls

​Initiate Outbound Call

​Response

​Example Request

​Example Response

​Error Responses

​Twilio Voice

​TwiML Webhook

​Response

Authorize Client Session

Endpoint

Headers

Request Body

Response

Example Request

Example Response

Error Responses

Example: Backend Endpoint (Next.js)

Agents

List Agents

Response

Example

Create Agent From Template

Response

Get Agent Details

Response

Update Agent Configuration

Response

Sessions

Get Session Details

Response

Example

Download Session Recording

Calls

Initiate Outbound Call

Response

Example Request

Example Response

Error Responses

Twilio Voice

TwiML Webhook

Response