Start a new browser session

import Stagehand from 'stagehand-sdk';

const client = new Stagehand({
  browserbaseAPIKey: process.env['BROWSERBASE_API_KEY'], // This is the default and can be omitted
  browserbaseProjectID: process.env['BROWSERBASE_PROJECT_ID'], // This is the default and can be omitted
  modelAPIKey: process.env['MODEL_API_KEY'], // This is the default and can be omitted
});

const response = await client.sessions.start({ modelName: 'openai/gpt-5.4-mini' });

console.log(response.data);

import os
from stagehand import Stagehand

client = Stagehand(
    browserbase_api_key=os.environ.get("BROWSERBASE_API_KEY"),  # This is the default and can be omitted
    browserbase_project_id=os.environ.get("BROWSERBASE_PROJECT_ID"),  # This is the default and can be omitted
    model_api_key=os.environ.get("MODEL_API_KEY"),  # This is the default and can be omitted
)
response = client.sessions.start(
    model_name="openai/gpt-5.4-mini",
)
print(response.data)

package main

import (
	"context"
	"fmt"

	"github.com/browserbase/stagehand-go"
	"github.com/browserbase/stagehand-go/option"
)

func main() {
	client := stagehand.NewClient(
		option.WithBrowserbaseAPIKey("My Browserbase API Key"),
		option.WithBrowserbaseProjectID("My Browserbase Project ID"),
		option.WithModelAPIKey("My Model API Key"),
	)
	response, err := client.Sessions.Start(context.TODO(), stagehand.SessionStartParams{
		ModelName: "openai/gpt-5.4-mini",
	})
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf("%+v\n", response.Data)
}

package com.browserbase.api.example;

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;
import com.browserbase.api.models.sessions.SessionStartParams;
import com.browserbase.api.models.sessions.SessionStartResponse;

public final class Main {
    private Main() {}

    public static void main(String[] args) {
        StagehandClient client = StagehandOkHttpClient.fromEnv();

        SessionStartParams params = SessionStartParams.builder()
            .modelName("openai/gpt-5.4-mini")
            .build();
        SessionStartResponse response = client.sessions().start(params);
    }
}

package com.browserbase.api.example

import com.browserbase.api.client.StagehandClient
import com.browserbase.api.client.okhttp.StagehandOkHttpClient
import com.browserbase.api.models.sessions.SessionStartParams
import com.browserbase.api.models.sessions.SessionStartResponse

fun main() {
    val client: StagehandClient = StagehandOkHttpClient.fromEnv()

    val params: SessionStartParams = SessionStartParams.builder()
        .modelName("openai/gpt-5.4-mini")
        .build()
    val response: SessionStartResponse = client.sessions().start(params)
}

require "stagehand"

stagehand = Stagehand::Client.new(
  browserbase_api_key: "My Browserbase API Key",
  browserbase_project_id: "My Browserbase Project ID",
  model_api_key: "My Model API Key"
)

response = stagehand.sessions.start(model_name: "openai/gpt-5.4-mini")

puts(response)

<?php

require_once dirname(__DIR__) . '/vendor/autoload.php';

use Stagehand\Client;
use Stagehand\Core\Exceptions\APIException;

$client = new Client(
  browserbaseAPIKey: getenv('BROWSERBASE_API_KEY') ?: 'My Browserbase API Key',
  browserbaseProjectID: getenv(
    'BROWSERBASE_PROJECT_ID'
  ) ?: 'My Browserbase Project ID',
  modelAPIKey: getenv('MODEL_API_KEY') ?: 'My Model API Key',
);

try {
  $response = $client->sessions->start(
    modelName: 'openai/gpt-5.4-mini',
    actTimeoutMs: 0,
    browser: [
      'cdpURL' => 'ws://localhost:9222',
      'launchOptions' => [
        'acceptDownloads' => true,
        'args' => ['string'],
        'cdpHeaders' => ['foo' => 'string'],
        'cdpURL' => 'cdpUrl',
        'chromiumSandbox' => true,
        'connectTimeoutMs' => 0,
        'deviceScaleFactor' => 0,
        'devtools' => true,
        'downloadsPath' => 'downloadsPath',
        'executablePath' => 'executablePath',
        'hasTouch' => true,
        'headless' => true,
        'ignoreDefaultArgs' => true,
        'ignoreHTTPSErrors' => true,
        'locale' => 'locale',
        'port' => 0,
        'preserveUserDataDir' => true,
        'proxy' => [
          'server' => 'server',
          'bypass' => 'bypass',
          'password' => 'password',
          'username' => 'username',
        ],
        'userDataDir' => 'userDataDir',
        'viewport' => ['height' => 0, 'width' => 0],
      ],
      'type' => 'local',
    ],
    browserbaseSessionCreateParams: [
      'browserSettings' => [
        'advancedStealth' => true,
        'blockAds' => true,
        'captchaImageSelector' => 'captchaImageSelector',
        'captchaInputSelector' => 'captchaInputSelector',
        'context' => ['id' => 'id', 'persist' => true],
        'extensionID' => 'extensionId',
        'fingerprint' => [
          'browsers' => ['chrome'],
          'devices' => ['desktop'],
          'httpVersion' => '1',
          'locales' => ['string'],
          'operatingSystems' => ['android'],
          'screen' => [
            'maxHeight' => 0, 'maxWidth' => 0, 'minHeight' => 0, 'minWidth' => 0
          ],
        ],
        'logSession' => true,
        'os' => 'windows',
        'recordSession' => true,
        'solveCaptchas' => true,
        'verified' => true,
        'viewport' => ['height' => 0, 'width' => 0],
      ],
      'extensionID' => 'extensionId',
      'keepAlive' => true,
      'projectID' => 'projectId',
      'proxies' => true,
      'region' => 'us-west-2',
      'timeout' => 0,
      'userMetadata' => ['foo' => 'bar'],
    ],
    browserbaseSessionID: 'browserbaseSessionID',
    domSettleTimeoutMs: 5000,
    experimental: true,
    selfHeal: true,
    systemPrompt: 'systemPrompt',
    verbose: 1,
    waitForCaptchaSolves: true,
    xStreamResponse: 'true',
  );

  var_dump($response);
} catch (APIException $e) {
  echo $e->getMessage();
}

using System;
using Stagehand;
using Stagehand.Models.Sessions;

StagehandClient client = new();

SessionStartParams parameters = new() { ModelName = "openai/gpt-5.4-mini" };

var response = await client.Sessions.Start(parameters);

Console.WriteLine(response);

curl --request POST \
  --url https://api.stagehand.browserbase.com/v1/sessions/start \
  --header 'Content-Type: application/json' \
  --header 'x-bb-api-key: <api-key>' \
  --header 'x-bb-project-id: <api-key>' \
  --data '
{
  "modelName": "openai/gpt-5.4-mini",
  "domSettleTimeoutMs": 5000,
  "verbose": 1,
  "systemPrompt": "<string>",
  "browserbaseSessionCreateParams": {
    "projectId": "<string>",
    "browserSettings": {
      "advancedStealth": true,
      "blockAds": true,
      "captchaImageSelector": "<string>",
      "captchaInputSelector": "<string>",
      "extensionId": "<string>",
      "fingerprint": {
        "browsers": [],
        "devices": [],
        "locales": [
          "<string>"
        ],
        "operatingSystems": [],
        "screen": {
          "maxHeight": 123,
          "maxWidth": 123,
          "minHeight": 123,
          "minWidth": 123
        }
      },
      "logSession": true,
      "recordSession": true,
      "solveCaptchas": true,
      "verified": true,
      "viewport": {
        "width": 123,
        "height": 123
      }
    },
    "extensionId": "<string>",
    "keepAlive": true,
    "proxies": true,
    "timeout": 123,
    "userMetadata": {}
  },
  "browser": {
    "type": "local",
    "cdpUrl": "ws://localhost:9222",
    "launchOptions": {
      "args": [
        "<string>"
      ],
      "executablePath": "<string>",
      "port": 123,
      "userDataDir": "<string>",
      "preserveUserDataDir": true,
      "headless": true,
      "devtools": true,
      "chromiumSandbox": true,
      "ignoreDefaultArgs": true,
      "locale": "<string>",
      "deviceScaleFactor": 123,
      "hasTouch": true,
      "ignoreHTTPSErrors": true,
      "cdpUrl": "<string>",
      "cdpHeaders": {},
      "connectTimeoutMs": 123,
      "downloadsPath": "<string>",
      "acceptDownloads": true
    }
  },
  "selfHeal": true,
  "browserbaseSessionID": "<string>",
  "experimental": true,
  "waitForCaptchaSolves": true,
  "actTimeoutMs": 123
}
'

{
  "success": true,
  "data": {
    "sessionId": "c4dbf3a9-9a58-4b22-8a1c-9f20f9f9e123",
    "available": true,
    "cdpUrl": "wss://connect.browserbase.com/?signingKey=abc123"
  }
}