Lang Smith Java API Library

The Lang Smith Java SDK provides convenient access to the Lang Smith REST API from applications written in Java. It includes helper classes with helpful types and documentation for every request and response property.

The Lang Smith Java SDK is similar to the Lang Smith Kotlin SDK but with minor differences that make it more ergonomic for use in Java, such as Optional instead of nullable values, Stream instead of Sequence, and CompletableFuture instead of suspend functions.

Documentation

The REST API documentation can be found on docs.langsmith.com.

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Getting started

Install dependencies

Gradle

implementation("com.langsmith.api:langsmith-java:0.0.1-alpha.0")

Maven

<dependency>
    <groupId>com.langsmith.api</groupId>
    <artifactId>langsmith-java</artifactId>
    <version>0.0.1-alpha.0</version>
</dependency>

Configure the client

Use LangSmithOkHttpClient.builder() to configure the client. At a minimum you need to set .apiKey():

import com.langsmith.api.client.LangSmithClient;
import com.langsmith.api.client.okhttp.LangSmithOkHttpClient;

LangSmithClient client = LangSmithOkHttpClient.builder()
    .apiKey("My API Key")
    .build();

Alternately, set the environment with LANGCHAIN_API_KEY, and use LangSmithOkHttpClient.fromEnv() to read from the environment.

LangSmithClient client = LangSmithOkHttpClient.fromEnv();

// Note: you can also call fromEnv() from the client builder, for example if you need to set additional properties
LangSmithClient client = LangSmithOkHttpClient.builder()
    .fromEnv()
    // ... set properties on the builder
    .build();

Property	Environment variable	Required	Default value
apiKey	LANGCHAIN_API_KEY	true	—

Read the documentation for more configuration options.

You can also set the LANGCHAIN_PROJECT to post runs to a specific project. If unspecified, runs will be posted to the default project.

Property	Environment variable	Required	Default value
project	LANGCHAIN_PROJECT	false	—

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Example: using the RunTree API (experimental)

The RunTree API is currently the recommended way to post runs to LangSmith.

See a full example in the here.

Example: creating a resource

To create a new run, first use the RunBatchParams builder to specify attributes, then pass that to the batch method of the runs service.

import com.langsmith.api.models.RunBatchParams;
import com.langsmith.api.models.RunBatchResponse;

RunBatchParams params = RunBatchParams.builder().build();
RunBatchResponse runBatchResponse = client.runs().batch(params);

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Requests

Parameters and bodies

To make a request to the Lang Smith API, you generally build an instance of the appropriate Params class.

In Example: creating a resource above, we used the SessionCreateParams.builder() to pass to the create method of the sessions service.

Sometimes, the API may support other properties that are not yet supported in the Java SDK types. In that case, you can attach them using the putAdditionalProperty method.

SessionCreateParams params = SessionCreateParams.builder()
    // ... normal properties
    .putAdditionalProperty("secret_param", "4242")
    .build();

Responses

Response validation

When receiving a response, the Lang Smith Java SDK will deserialize it into instances of the typed model classes. In rare cases, the API may return a response property that doesn't match the expected Java type. If you directly access the mistaken property, the SDK will throw an unchecked LangSmithInvalidDataException at runtime. If you would prefer to check in advance that that response is completely well-typed, call .validate() on the returned model.

TracerSessionWithoutVirtualFields tracerSessionWithoutVirtualFields = client.sessions().create().validate();

Response properties as JSON

In rare cases, you may want to access the underlying JSON value for a response property rather than using the typed version provided by this SDK. Each model property has a corresponding JSON version, with an underscore before the method name, which returns a JsonField value.

JsonField field = responseObj._field();

if (field.isMissing()) {
  // Value was not specified in the JSON response
} else if (field.isNull()) {
  // Value was provided as a literal null
} else {
  // See if value was provided as a string
  Optional<String> jsonString = field.asString();

  // If the value given by the API did not match the shape that the SDK expects
  // you can deserialise into a custom type
  MyClass myObj = responseObj._field().asUnknown().orElseThrow().convert(MyClass.class);
}

Additional model properties

Sometimes, the server response may include additional properties that are not yet available in this library's types. You can access them using the model's _additionalProperties method:

JsonValue secret = tracerSessionWithoutVirtualFields._additionalProperties().get("secret_field");

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Error handling

This library throws exceptions in a single hierarchy for easy handling:

• LangSmithException - Base exception for all exceptions

  • LangSmithServiceException - HTTP errors with a well-formed response body we were able to parse. The exception message and the .debuggingRequestId() will be set by the server.

    | 400 | BadRequestException | | ------ | ----------------------------- | | 401 | AuthenticationException | | 403 | PermissionDeniedException | | 404 | NotFoundException | | 422 | UnprocessableEntityException | | 429 | RateLimitException | | 5xx | InternalServerException | | others | UnexpectedStatusCodeException |

  • LangSmithIoException - I/O networking errors

  • LangSmithInvalidDataException - any other exceptions on the client side, e.g.:

    • We failed to serialize the request body
    • We failed to parse the response body (has access to response code and body)

Network options

Retries

Requests that experience certain errors are automatically retried 2 times by default, with a short exponential backoff. Connection errors (for example, due to a network connectivity problem), 408 Request Timeout, 409 Conflict, 429 Rate Limit, and >=500 Internal errors will all be retried by default. You can provide a maxRetries on the client builder to configure this:

LangSmithClient client = LangSmithOkHttpClient.builder()
    .fromEnv()
    .maxRetries(4)
    .build();

Timeouts

Requests time out after 1 minute by default. You can configure this on the client builder:

LangSmithClient client = LangSmithOkHttpClient.builder()
    .fromEnv()
    .timeout(Duration.ofSeconds(30))
    .build();

Proxies

Requests can be routed through a proxy. You can configure this on the client builder:

LangSmithClient client = LangSmithOkHttpClient.builder()
    .fromEnv()
    .proxy(new Proxy(
        Type.HTTP,
        new InetSocketAddress("proxy.com", 8080)
    ))
    .build();

Semantic Versioning

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

1. 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).
2. 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.