Java SDK

This documentation is automatically synced from the Java SDK GitHub repository.

The Stagehand Java SDK provides convenient access to the Stagehand REST API from applications written in Java. It is generated with Stainless.

MCP Server

Use the Stagehand MCP Server to enable AI assistants to interact with this API, allowing them to explore endpoints, make test requests, and use documentation to help integrate this SDK into your application.

Note: You may need to set environment variables in your MCP client.

The REST API documentation can be found on docs.stagehand.dev. Javadocs are available on javadoc.io.

Installation

Gradle

implementation("com.browserbase.api:stagehand-java:0.5.0")

Maven

<dependency>
  <groupId>com.browserbase.api</groupId>
  <artifactId>stagehand-java</artifactId>
  <version>0.5.0</version>
</dependency>

Requirements

This library requires Java 8 through Java 21. Java 22+ is not currently supported.

Running the Example

A complete working example is available at stagehand-java-example/src/main/java/com/stagehand/api/example/Main.java. To run it, first export the required environment variables, then use Gradle:

export BROWSERBASE_API_KEY="your-bb-api-key"
export BROWSERBASE_PROJECT_ID="your-bb-project-uuid"
export MODEL_API_KEY="sk-proj-your-llm-api-key"

./gradlew :stagehand-java-example:run

Usage

This example demonstrates the full Stagehand workflow: starting a session, navigating to a page, observing possible actions, acting on elements, extracting data, and running an autonomous agent.

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;
import com.browserbase.api.core.JsonValue;
import com.browserbase.api.models.sessions.*;

import java.util.List;
import java.util.Map;
import java.util.Optional;

public class Main {
    private static final String SDK_VERSION = "3.0.6";

    public static void main(String[] args) {
        // Create client using environment variables:
        // BROWSERBASE_API_KEY, BROWSERBASE_PROJECT_ID, MODEL_API_KEY
        StagehandClient client = StagehandOkHttpClient.fromEnv();

        // Start a new browser session
        SessionStartResponse startResponse = client.sessions().start(
            SessionStartParams.builder()
                .modelName("openai/gpt-5-nano")
                .xLanguage(SessionStartParams.XLanguage.TYPESCRIPT)
                .xSdkVersion(SDK_VERSION)
                .build()
        );

        String sessionId = startResponse.data().sessionId();
        System.out.println("Session started: " + sessionId);

        try {
            // Navigate to a webpage
            // frameId is required - use empty string for the main frame
            client.sessions().navigate(
                SessionNavigateParams.builder()
                    .id(sessionId)
                    .url("https://news.ycombinator.com")
                    .frameId("")
                    .xLanguage(SessionNavigateParams.XLanguage.TYPESCRIPT)
                    .xSdkVersion(SDK_VERSION)
                    .build()
            );
            System.out.println("Navigated to Hacker News");

            // Observe to find possible actions on the page
            SessionObserveResponse observeResponse = client.sessions().observe(
                SessionObserveParams.builder()
                    .id(sessionId)
                    .instruction("find the link to view comments for the top post")
                    .xLanguage(SessionObserveParams.XLanguage.TYPESCRIPT)
                    .xSdkVersion(SDK_VERSION)
                    .build()
            );

            List<SessionObserveResponse.Data.Result> results = observeResponse.data().result();
            System.out.println("Found " + results.size() + " possible actions");

            if (results.isEmpty()) {
                System.out.println("No actions found");
                return;
            }

            // Take the first action returned by Observe
            // Convert the result to an Action to pass to Act
            SessionObserveResponse.Data.Result result = results.get(0);
            Action action = JsonValue.from(result).convert(Action.class);
            System.out.println("Acting on: " + action.description());

            // Pass the structured action to Act
            SessionActResponse actResponse = client.sessions().act(
                SessionActParams.builder()
                    .id(sessionId)
                    .input(action)
                    .xLanguage(SessionActParams.XLanguage.TYPESCRIPT)
                    .xSdkVersion(SDK_VERSION)
                    .build()
            );
            System.out.println("Act completed: " + actResponse.data().result().message());

            // Extract structured data from the page using a JSON schema
            SessionExtractResponse extractResponse = client.sessions().extract(
                SessionExtractParams.builder()
                    .id(sessionId)
                    .instruction("extract the text of the top comment on this page")
                    .schema(SessionExtractParams.Schema.builder()
                        .putAdditionalProperty("type", JsonValue.from("object"))
                        .putAdditionalProperty("properties", JsonValue.from(Map.of(
                            "commentText", Map.of(
                                "type", "string",
                                "description", "The text content of the top comment"
                            ),
                            "author", Map.of(
                                "type", "string",
                                "description", "The username of the comment author"
                            )
                        )))
                        .putAdditionalProperty("required", JsonValue.from(List.of("commentText")))
                        .build())
                    .xLanguage(SessionExtractParams.XLanguage.TYPESCRIPT)
                    .xSdkVersion(SDK_VERSION)
                    .build()
            );

            JsonValue extractedResult = extractResponse.data()._result();
            System.out.println("Extracted data: " + extractedResult);

            // Get the author from the extracted data
            String author = extractedResult.asObject()
                .flatMap(obj -> Optional.ofNullable(obj.get("author")))
                .flatMap(JsonValue::asString)
                .orElse("unknown");
            System.out.println("Looking up profile for author: " + author);

            // Run an autonomous agent to accomplish a complex task
            SessionExecuteResponse executeResponse = client.sessions().execute(
                SessionExecuteParams.builder()
                    .id(sessionId)
                    .executeOptions(SessionExecuteParams.ExecuteOptions.builder()
                        .instruction(String.format(
                            "Find any personal website, GitHub, or LinkedIn profile for user '%s'. " +
                            "Click on their username to view their profile page.",
                            author
                        ))
                        .maxSteps(10.0)
                        .build())
                    .agentConfig(SessionExecuteParams.AgentConfig.builder()
                        .model(ModelConfig.ofModelConfigObject(
                            ModelConfig.ModelConfigObject.builder()
                                .modelName("openai/gpt-5-nano")
                                .apiKey(System.getenv("MODEL_API_KEY"))
                                .build()
                        ))
                        .cua(false)
                        .build())
                    .xLanguage(SessionExecuteParams.XLanguage.TYPESCRIPT)
                    .xSdkVersion(SDK_VERSION)
                    .build()
            );

            System.out.println("Agent completed: " + executeResponse.data().result().message());
            System.out.println("Agent success: " + executeResponse.data().result().success());

        } finally {
            // End the browser session to clean up resources
            client.sessions().end(
                SessionEndParams.builder()
                    .id(sessionId)
                    .xLanguage(SessionEndParams.XLanguage.TYPESCRIPT)
                    .xSdkVersion(SDK_VERSION)
                    .build()
            );
            System.out.println("Session ended");
        }
    }
}

Client configuration

Configure the client using system properties or environment variables:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;

// Configures using the `stagehand.browserbaseApiKey`, `stagehand.browserbaseProjectId`, `stagehand.modelApiKey` and `stagehand.baseUrl` system properties
// Or configures using the `BROWSERBASE_API_KEY`, `BROWSERBASE_PROJECT_ID`, `MODEL_API_KEY` and `STAGEHAND_BASE_URL` environment variables
StagehandClient client = StagehandOkHttpClient.fromEnv();

Or manually:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;

StagehandClient client = StagehandOkHttpClient.builder()
    .browserbaseApiKey("My Browserbase API Key")
    .browserbaseProjectId("My Browserbase Project ID")
    .modelApiKey("My Model API Key")
    .build();

Or using a combination of the two approaches:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;

StagehandClient client = StagehandOkHttpClient.builder()
    // Configures using the `stagehand.browserbaseApiKey`, `stagehand.browserbaseProjectId`, `stagehand.modelApiKey` and `stagehand.baseUrl` system properties
    // Or configures using the `BROWSERBASE_API_KEY`, `BROWSERBASE_PROJECT_ID`, `MODEL_API_KEY` and `STAGEHAND_BASE_URL` environment variables
    .fromEnv()
    .browserbaseApiKey("My Browserbase API Key")
    .build();

See this table for the available options:

Setter	System property	Environment variable	Required	Default value
`browserbaseApiKey`	`stagehand.browserbaseApiKey`	`BROWSERBASE_API_KEY`	true	-
`browserbaseProjectId`	`stagehand.browserbaseProjectId`	`BROWSERBASE_PROJECT_ID`	true	-
`modelApiKey`	`stagehand.modelApiKey`	`MODEL_API_KEY`	true	-
`baseUrl`	`stagehand.baseUrl`	`STAGEHAND_BASE_URL`	true	`"https://api.stagehand.browserbase.com"`

System properties take precedence over environment variables.

[!TIP] Don’t create more than one client in the same application. Each client has a connection pool and thread pools, which are more efficient to share between requests.

Modifying configuration

To temporarily use a modified client configuration, while reusing the same connection and thread pools, call withOptions() on any client or service:

import com.browserbase.api.client.StagehandClient;

StagehandClient clientWithOptions = client.withOptions(optionsBuilder -> {
    optionsBuilder.modelApiKey("sk-your-llm-api-key-here");
    optionsBuilder.maxRetries(42);
});

The withOptions() method does not affect the original client or service.

Requests and responses

To send a request to the Stagehand API, build an instance of some Params class and pass it to the corresponding client method. When the response is received, it will be deserialized into an instance of a Java class. For example, client.sessions().act(...) should be called with an instance of SessionActParams, and it will return an instance of SessionActResponse.

Immutability

Each class in the SDK has an associated builder or factory method for constructing it. Each class is immutable once constructed. If the class has an associated builder, then it has a toBuilder() method, which can be used to convert it back to a builder for making a modified copy. Because each class is immutable, builder modification will never affect already built class instances.

Asynchronous execution

The default client is synchronous. To switch to asynchronous execution, call the async() method:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;
import com.browserbase.api.models.sessions.SessionActParams;
import com.browserbase.api.models.sessions.SessionActResponse;
import java.util.concurrent.CompletableFuture;

// Configures using the `stagehand.browserbaseApiKey`, `stagehand.browserbaseProjectId`, `stagehand.modelApiKey` and `stagehand.baseUrl` system properties
// Or configures using the `BROWSERBASE_API_KEY`, `BROWSERBASE_PROJECT_ID`, `MODEL_API_KEY` and `STAGEHAND_BASE_URL` environment variables
StagehandClient client = StagehandOkHttpClient.fromEnv();

SessionActParams params = SessionActParams.builder()
    .id("00000000-your-session-id-000000000000")
    .input("click the first link on the page")
    .build();
CompletableFuture<SessionActResponse> response = client.async().sessions().act(params);

Or create an asynchronous client from the beginning:

import com.browserbase.api.client.StagehandClientAsync;
import com.browserbase.api.client.okhttp.StagehandOkHttpClientAsync;
import com.browserbase.api.models.sessions.SessionActParams;
import com.browserbase.api.models.sessions.SessionActResponse;
import java.util.concurrent.CompletableFuture;

// Configures using the `stagehand.browserbaseApiKey`, `stagehand.browserbaseProjectId`, `stagehand.modelApiKey` and `stagehand.baseUrl` system properties
// Or configures using the `BROWSERBASE_API_KEY`, `BROWSERBASE_PROJECT_ID`, `MODEL_API_KEY` and `STAGEHAND_BASE_URL` environment variables
StagehandClientAsync client = StagehandOkHttpClientAsync.fromEnv();

SessionActParams params = SessionActParams.builder()
    .id("00000000-your-session-id-000000000000")
    .input("click the first link on the page")
    .build();
CompletableFuture<SessionActResponse> response = client.sessions().act(params);

The asynchronous client supports the same options as the synchronous one, except most methods return CompletableFutures.

Streaming

The SDK defines methods that return response “chunk” streams, where each chunk can be individually processed as soon as it arrives instead of waiting on the full response. Streaming methods generally correspond to SSE or JSONL responses. Some of these methods may have streaming and non-streaming variants, but a streaming method will always have a Streaming suffix in its name, even if it doesn’t have a non-streaming variant. These streaming methods return StreamResponse for synchronous clients:

import com.browserbase.api.core.http.StreamResponse;
import com.browserbase.api.models.sessions.StreamEvent;

try (StreamResponse<StreamEvent> streamResponse = client.sessions().actStreaming(params)) {
    streamResponse.stream().forEach(chunk -> {
        System.out.println(chunk);
    });
    System.out.println("No more chunks!");
}

Or AsyncStreamResponse for asynchronous clients:

import com.browserbase.api.core.http.AsyncStreamResponse;
import com.browserbase.api.models.sessions.StreamEvent;
import java.util.Optional;

client.async().sessions().actStreaming(params).subscribe(chunk -> {
    System.out.println(chunk);
});

// If you need to handle errors or completion of the stream
client.async().sessions().actStreaming(params).subscribe(new AsyncStreamResponse.Handler<>() {
    @Override
    public void onNext(StreamEvent chunk) {
        System.out.println(chunk);
    }

    @Override
    public void onComplete(Optional<Throwable> error) {
        if (error.isPresent()) {
            System.out.println("Something went wrong!");
            throw new RuntimeException(error.get());
        } else {
            System.out.println("No more chunks!");
        }
    }
});

// Or use futures
client.async().sessions().actStreaming(params)
    .subscribe(chunk -> {
        System.out.println(chunk);
    })
    .onCompleteFuture();
    .whenComplete((unused, error) -> {
        if (error != null) {
            System.out.println("Something went wrong!");
            throw new RuntimeException(error);
        } else {
            System.out.println("No more chunks!");
        }
    });

Async streaming uses a dedicated per-client cached thread pool Executor to stream without blocking the current thread. This default is suitable for most purposes. To use a different Executor, configure the subscription using the executor parameter:

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

Executor executor = Executors.newFixedThreadPool(4);
client.async().sessions().actStreaming(params).subscribe(
    chunk -> System.out.println(chunk), executor
);

Or configure the client globally using the streamHandlerExecutor method:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;
import java.util.concurrent.Executors;

StagehandClient client = StagehandOkHttpClient.builder()
    .fromEnv()
    .streamHandlerExecutor(Executors.newFixedThreadPool(4))
    .build();

Raw responses

The SDK defines methods that deserialize responses into instances of Java classes. However, these methods don’t provide access to the response headers, status code, or the raw response body. To access this data, prefix any HTTP method call on a client or service with withRawResponse():

import com.browserbase.api.core.http.Headers;
import com.browserbase.api.core.http.HttpResponseFor;
import com.browserbase.api.models.sessions.SessionStartParams;
import com.browserbase.api.models.sessions.SessionStartResponse;

SessionStartParams params = SessionStartParams.builder()
    .modelName("openai/gpt-5-nano")
    .build();
HttpResponseFor<SessionStartResponse> response = client.sessions().withRawResponse().start(params);

int statusCode = response.statusCode();
Headers headers = response.headers();

You can still deserialize the response into an instance of a Java class if needed:

import com.browserbase.api.models.sessions.SessionStartResponse;

SessionStartResponse parsedResponse = response.parse();

Error handling

The SDK throws custom unchecked exception types:

StagehandServiceException: Base class for HTTP errors. See this table for which exception subclass is thrown for each HTTP status code:

Status	Exception
400	`BadRequestException`
401	`UnauthorizedException`
403	`PermissionDeniedException`
404	`NotFoundException`
422	`UnprocessableEntityException`
429	`RateLimitException`
5xx	`InternalServerException`
others	`UnexpectedStatusCodeException`

SseException is thrown for errors encountered during SSE streaming after a successful initial HTTP response.

StagehandIoException: I/O networking errors.
StagehandRetryableException: Generic error indicating a failure that could be retried by the client.
StagehandInvalidDataException: Failure to interpret successfully parsed data. For example, when accessing a property that’s supposed to be required, but the API unexpectedly omitted it from the response.
StagehandException: Base class for all exceptions. Most errors will result in one of the previously mentioned ones, but completely generic errors may be thrown using the base class.

Logging

The SDK uses the standard OkHttp logging interceptor. Enable logging by setting the STAGEHAND_LOG environment variable to info:

export STAGEHAND_LOG=info

Or to debug for more verbose logging:

export STAGEHAND_LOG=debug

ProGuard and R8

Although the SDK uses reflection, it is still usable with ProGuard and R8 because stagehand-java-core is published with a configuration file containing keep rules. ProGuard and R8 should automatically detect and use the published rules, but you can also manually copy the keep rules if necessary.

Jackson

The SDK depends on Jackson for JSON serialization/deserialization. It is compatible with version 2.13.4 or higher, but depends on version 2.18.2 by default. The SDK throws an exception if it detects an incompatible Jackson version at runtime (e.g. if the default version was overridden in your Maven or Gradle config). If the SDK threw an exception, but you’re certain the version is compatible, then disable the version check using the checkJacksonVersionCompatibility on StagehandOkHttpClient or StagehandOkHttpClientAsync.

[!CAUTION] We make no guarantee that the SDK works correctly when the Jackson version check is disabled.

Network options

Retries

The SDK automatically retries 2 times by default, with a short exponential backoff between requests. Only the following error types are retried:

Connection errors (for example, due to a network connectivity problem)
408 Request Timeout
409 Conflict
429 Rate Limit
5xx Internal

The API may also explicitly instruct the SDK to retry or not retry a request. To set a custom number of retries, configure the client using the maxRetries method:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;

StagehandClient client = StagehandOkHttpClient.builder()
    .fromEnv()
    .maxRetries(4)
    .build();

Timeouts

Requests time out after 1 minute by default. To set a custom timeout, configure the method call using the timeout method:

import com.browserbase.api.models.sessions.SessionStartResponse;

SessionStartResponse response = client.sessions().start(
  params, RequestOptions.builder().timeout(Duration.ofSeconds(30)).build()
);

Or configure the default for all method calls at the client level:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;
import java.time.Duration;

StagehandClient client = StagehandOkHttpClient.builder()
    .fromEnv()
    .timeout(Duration.ofSeconds(30))
    .build();

Proxies

To route requests through a proxy, configure the client using the proxy method:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;
import java.net.InetSocketAddress;
import java.net.Proxy;

StagehandClient client = StagehandOkHttpClient.builder()
    .fromEnv()
    .proxy(new Proxy(
      Proxy.Type.HTTP, new InetSocketAddress(
        "https://example.com", 8080
      )
    ))
    .build();

HTTPS

[!NOTE] Most applications should not call these methods, and instead use the system defaults. The defaults include special optimizations that can be lost if the implementations are modified.

To configure how HTTPS connections are secured, configure the client using the sslSocketFactory, trustManager, and hostnameVerifier methods:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;

StagehandClient client = StagehandOkHttpClient.builder()
    .fromEnv()
    // If `sslSocketFactory` is set, then `trustManager` must be set, and vice versa.
    .sslSocketFactory(yourSSLSocketFactory)
    .trustManager(yourTrustManager)
    .hostnameVerifier(yourHostnameVerifier)
    .build();

Custom HTTP client

The SDK consists of three artifacts:

stagehand-java-core
- Contains core SDK logic
- Does not depend on OkHttp
- Exposes StagehandClient, StagehandClientAsync, StagehandClientImpl, and StagehandClientAsyncImpl, all of which can work with any HTTP client
stagehand-java-client-okhttp
- Depends on OkHttp
- Exposes StagehandOkHttpClient and StagehandOkHttpClientAsync, which provide a way to construct StagehandClientImpl and StagehandClientAsyncImpl, respectively, using OkHttp
stagehand-java
- Depends on and exposes the APIs of both stagehand-java-core and stagehand-java-client-okhttp
- Does not have its own logic

This structure allows replacing the SDK’s default HTTP client without pulling in unnecessary dependencies.

Customized `OkHttpClient`

[!TIP] Try the available network options before replacing the default client.

To use a customized OkHttpClient:

Replace your stagehand-java dependency with stagehand-java-core
Copy stagehand-java-client-okhttp’s OkHttpClient class into your code and customize it
Construct StagehandClientImpl or StagehandClientAsyncImpl, similarly to StagehandOkHttpClient or StagehandOkHttpClientAsync, using your customized client

Completely custom HTTP client

To use a completely custom HTTP client:

Replace your stagehand-java dependency with stagehand-java-core
Write a class that implements the HttpClient interface
Construct StagehandClientImpl or StagehandClientAsyncImpl, similarly to StagehandOkHttpClient or StagehandOkHttpClientAsync, using your new client class

Undocumented API functionality

The SDK is typed for convenient usage of the documented API. However, it also supports working with undocumented or not yet supported parts of the API.

Parameters

To set undocumented parameters, call the putAdditionalHeader, putAdditionalQueryParam, or putAdditionalBodyProperty methods on any Params class:

import com.browserbase.api.core.JsonValue;
import com.browserbase.api.models.sessions.SessionActParams;

SessionActParams params = SessionActParams.builder()
    .putAdditionalHeader("Secret-Header", "42")
    .putAdditionalQueryParam("secret_query_param", "42")
    .putAdditionalBodyProperty("secretProperty", JsonValue.from("42"))
    .build();

These can be accessed on the built object later using the _additionalHeaders(), _additionalQueryParams(), and _additionalBodyProperties() methods. To set undocumented parameters on nested headers, query params, or body classes, call the putAdditionalProperty method on the nested class:

import com.browserbase.api.core.JsonValue;
import com.browserbase.api.models.sessions.SessionActParams;

SessionActParams params = SessionActParams.builder()
    .options(SessionActParams.Options.builder()
        .putAdditionalProperty("secretProperty", JsonValue.from("42"))
        .build())
    .build();

These properties can be accessed on the nested built object later using the _additionalProperties() method. To set a documented parameter or property to an undocumented or not yet supported value, pass a JsonValue object to its setter:

import com.browserbase.api.core.JsonValue;
import com.browserbase.api.models.sessions.SessionActParams;

SessionActParams params = SessionActParams.builder()
    .input(JsonValue.from(42))
    .build();

The most straightforward way to create a JsonValue is using its from(...) method:

import com.browserbase.api.core.JsonValue;
import java.util.List;
import java.util.Map;

// Create primitive JSON values
JsonValue nullValue = JsonValue.from(null);
JsonValue booleanValue = JsonValue.from(true);
JsonValue numberValue = JsonValue.from(42);
JsonValue stringValue = JsonValue.from("Hello World!");

// Create a JSON array value equivalent to `["Hello", "World"]`
JsonValue arrayValue = JsonValue.from(List.of(
  "Hello", "World"
));

// Create a JSON object value equivalent to `{ "a": 1, "b": 2 }`
JsonValue objectValue = JsonValue.from(Map.of(
  "a", 1,
  "b", 2
));

// Create an arbitrarily nested JSON equivalent to:
// {
//   "a": [1, 2],
//   "b": [3, 4]
// }
JsonValue complexValue = JsonValue.from(Map.of(
  "a", List.of(
    1, 2
  ),
  "b", List.of(
    3, 4
  )
));

Normally a Builder class’s build method will throw IllegalStateException if any required parameter or property is unset. To forcibly omit a required parameter or property, pass JsonMissing:

import com.browserbase.api.core.JsonMissing;
import com.browserbase.api.models.sessions.SessionActParams;

SessionActParams params = SessionActParams.builder()
    .input("Click the login button")
    .id(JsonMissing.of())
    .build();

Response properties

To access undocumented response properties, call the _additionalProperties() method:

import com.browserbase.api.core.JsonValue;
import java.util.Map;

Map<String, JsonValue> additionalProperties = client.sessions().act(params)._additionalProperties();
JsonValue secretPropertyValue = additionalProperties.get("secretProperty");

String result = secretPropertyValue.accept(new JsonValue.Visitor<>() {
    @Override
    public String visitNull() {
        return "It's null!";
    }

    @Override
    public String visitBoolean(boolean value) {
        return "It's a boolean!";
    }

    @Override
    public String visitNumber(Number value) {
        return "It's a number!";
    }

    // Other methods include `visitMissing`, `visitString`, `visitArray`, and `visitObject`
    // The default implementation of each unimplemented method delegates to `visitDefault`, which throws by default, but can also be overridden
});

To access a property’s raw JSON value, which may be undocumented, call its _ prefixed method:

import com.browserbase.api.core.JsonField;
import com.browserbase.api.models.sessions.SessionActParams;
import java.util.Optional;

JsonField<SessionActParams.Input> input = client.sessions().act(params)._input();

if (input.isMissing()) {
  // The property is absent from the JSON response
} else if (input.isNull()) {
  // The property was set to literal null
} else {
  // Check if value was provided as a string
  // Other methods include `asNumber()`, `asBoolean()`, etc.
  Optional<String> jsonString = input.asString();

  // Try to deserialize into a custom type
  MyClass myObject = input.asUnknown().orElseThrow().convert(MyClass.class);
}

Response validation

In rare cases, the API may return a response that doesn’t match the expected type. For example, the SDK may expect a property to contain a String, but the API could return something else. By default, the SDK will not throw an exception in this case. It will throw StagehandInvalidDataException only if you directly access the property. If you would prefer to check that the response is completely well-typed upfront, then either call validate():

import com.browserbase.api.models.sessions.SessionActResponse;

SessionActResponse response = client.sessions().act(params).validate();

Or configure the method call to validate the response using the responseValidation method:

import com.browserbase.api.models.sessions.SessionActResponse;

SessionActResponse response = client.sessions().act(
  params, RequestOptions.builder().responseValidation(true).build()
);

Or configure the default for all method calls at the client level:

import com.browserbase.api.client.StagehandClient;
import com.browserbase.api.client.okhttp.StagehandOkHttpClient;

StagehandClient client = StagehandOkHttpClient.builder()
    .fromEnv()
    .responseValidation(true)
    .build();

FAQ

Why don’t you use plain `enum` classes?

Java enum classes are not trivially forwards compatible. Using them in the SDK could cause runtime exceptions if the API is updated to respond with a new enum value.

Why do you represent fields using `JsonField<T>` instead of just plain `T`?

Using JsonField<T> enables a few features:

Allowing usage of undocumented API functionality
Lazily validating the API response against the expected shape
Representing absent vs explicitly null values

Why don’t you use `data` classes?

It is not backwards compatible to add new fields to a data class and we don’t want to introduce a breaking change every time we add a field to a class.

Why don’t you use checked exceptions?

Checked exceptions are widely considered a mistake in the Java programming language. In fact, they were omitted from Kotlin for this reason. Checked exceptions:

Are verbose to handle
Encourage error handling at the wrong level of abstraction, where nothing can be done about the error
Are tedious to propagate due to the function coloring problem
Don’t play well with lambdas (also due to the function coloring problem)

Semantic versioning

This package generally follows SemVer conventions, though certain backwards-incompatible changes may be released as minor versions:

Changes to library internals which are technically public but not intended or documented for external use. (Please open a GitHub issue to let us know if you are relying on such internals.)
Changes that we do not expect to impact the vast majority of users in practice.

We take backwards-compatibility seriously and work hard to ensure you can rely on a smooth upgrade experience. We are keen for your feedback; please open an issue with questions, bugs, or suggestions.

SDK Reference

API Reference

MCP Server

Installation

Gradle

Maven

Requirements

Running the Example

Usage

Client configuration

Modifying configuration

Requests and responses

Immutability

Asynchronous execution

Streaming

Raw responses

Error handling

Logging

ProGuard and R8

Jackson

Network options

Retries

Timeouts

Proxies

HTTPS

Custom HTTP client

Customized `OkHttpClient`

Completely custom HTTP client

Undocumented API functionality

Parameters

Response properties

Response validation

FAQ

Why don’t you use plain `enum` classes?

Why do you represent fields using `JsonField<T>` instead of just plain `T`?

Why don’t you use `data` classes?

Why don’t you use checked exceptions?

Semantic versioning

SDK Reference

API Reference

​MCP Server

​Installation

​Gradle

​Maven

​Requirements

​Running the Example

​Usage

​Client configuration

​Modifying configuration

​Requests and responses

​Immutability

​Asynchronous execution

​Streaming

​Raw responses

​Error handling

​Logging

​ProGuard and R8

​Jackson

​Network options

​Retries

​Timeouts

​Proxies

​HTTPS

​Custom HTTP client

​Customized OkHttpClient

​Completely custom HTTP client

​Undocumented API functionality

​Parameters

​Response properties

​Response validation

​FAQ

​Why don’t you use plain enum classes?

​Why do you represent fields using JsonField<T> instead of just plain T?

​Why don’t you use data classes?

​Why don’t you use checked exceptions?

​Semantic versioning

MCP Server

Installation

Gradle

Maven

Requirements

Running the Example

Usage

Client configuration

Modifying configuration

Requests and responses

Immutability

Asynchronous execution

Streaming

Raw responses

Error handling

Logging

ProGuard and R8

Jackson

Network options

Retries

Timeouts

Proxies

HTTPS

Custom HTTP client

Customized `OkHttpClient`

Completely custom HTTP client

Undocumented API functionality

Parameters

Response properties

Response validation

FAQ

Why don’t you use plain `enum` classes?

Why do you represent fields using `JsonField<T>` instead of just plain `T`?

Why don’t you use `data` classes?

Why don’t you use checked exceptions?

Semantic versioning