Ruby SDK

The Anthropic Ruby library provides convenient access to the Anthropic REST API from any Ruby 3.2.0+ application. It ships with comprehensive types and docstrings in Yard, RBS, and RBI. The standard library's net/http is used as the HTTP transport, with connection pooling via the connection_pool gem.

Installation

To use this gem, install via Bundler by adding the following to your application's Gemfile:

gem "anthropic", "~> 1.16.3"

Requirements

Ruby 3.2.0 or higher.

Usage

require "anthropic"

anthropic = Anthropic::Client.new(
  api_key: ENV["ANTHROPIC_API_KEY"] # This is the default and can be omitted
)

message = anthropic.messages.create(
  max_tokens: 1024,
  messages: [{role: "user", content: "Hello, Claude"}],
  model: :"claude-opus-4-6"
)

puts(message.content)

Streaming

We provide support for streaming responses using Server-Sent Events (SSE).

stream = anthropic.messages.stream(
  max_tokens: 1024,
  messages: [{role: "user", content: "Hello, Claude"}],
  model: :"claude-opus-4-6"
)

stream.each do |message|
  puts(message.type)
end

Streaming helpers

This library provides several conveniences for streaming messages, for example:

stream = anthropic.messages.stream(
  max_tokens: 1024,
  messages: [{role: :user, content: "Say hello there!"}],
  model: :"claude-opus-4-6"
)

stream.text.each do |text|
  print(text)
end

Streaming with anthropic.messages.stream(...) exposes various helpers including accumulation and SDK-specific events.

Input Schema and Tool Calling

The SDK provides helper mechanisms to define structured data classes for tools and let Claude automatically execute them. For detailed documentation on tool use patterns including the tool runner, see Implementing Tool Use.

class CalculatorInput < Anthropic::BaseModel
  required :lhs, Float
  required :rhs, Float
  required :operator, Anthropic::InputSchema::EnumOf[:+, :-, :*, :/]
end

class Calculator < Anthropic::BaseTool
  input_schema CalculatorInput

  def call(expr)
    expr.lhs.public_send(expr.operator, expr.rhs)
  end
end

# Automatically handles tool execution loop
client.beta.messages.tool_runner(
  model: "claude-opus-4-6",
  max_tokens: 1024,
  messages: [{role: "user", content: "What's 15 * 7?"}],
  tools: [Calculator.new]
).each_message { puts _1.content }

Handling errors

When the library is unable to connect to the API, or if the API returns a non-success status code (i.e., 4xx or 5xx response), a subclass of Anthropic::Errors::APIError will be thrown:

begin
  message = anthropic.messages.create(
    max_tokens: 1024,
    messages: [{role: "user", content: "Hello, Claude"}],
    model: :"claude-opus-4-6"
  )
rescue Anthropic::Errors::APIConnectionError => e
  puts("The server could not be reached")
  puts(e.cause)  # an underlying Exception, likely raised within `net/http`
rescue Anthropic::Errors::RateLimitError => e
  puts("A 429 status code was received; we should back off a bit.")
rescue Anthropic::Errors::APIStatusError => e
  puts("Another non-200-range status code was received")
  puts(e.status)
end

Error codes are as follows:

Retries

Certain errors will be 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, >=500 Internal errors, and timeouts will all be retried by default.

You can use the max_retries option to configure or disable this:

# Configure the default for all requests:
anthropic = Anthropic::Client.new(
  max_retries: 0 # default is 2
)

# Or, configure per-request:
anthropic.messages.create(
  max_tokens: 1024,
  messages: [{role: "user", content: "Hello, Claude"}],
  model: :"claude-opus-4-6",
  request_options: {max_retries: 5}
)

Timeouts

By default, requests will time out after 600 seconds. You can use the timeout option to configure or disable this:

# Configure the default for all requests:
anthropic = Anthropic::Client.new(
  timeout: nil # default is 600
)

# Or, configure per-request:
anthropic.messages.create(
  max_tokens: 1024,
  messages: [{role: "user", content: "Hello, Claude"}],
  model: :"claude-opus-4-6",
  request_options: {timeout: 5}
)

On timeout, Anthropic::Errors::APITimeoutError is raised.

Note that requests that time out are retried by default.

Pagination

List methods in the Claude API are paginated.

This library provides auto-paginating iterators with each list response, so you do not have to request successive pages manually:

page = anthropic.messages.batches.list(limit: 20)

# Fetch single item from page.
batch = page.data[0]
puts(batch.id)

# Automatically fetches more pages as needed.
page.auto_paging_each do |batch|
  puts(batch.id)
end

Alternatively, you can use the #next_page? and #next_page methods for more granular control working with pages.

if page.next_page?
  new_page = page.next_page
  puts(new_page.data[0].id)
end

File uploads

Request parameters that correspond to file uploads can be passed as raw contents, a Pathname instance, StringIO, or more.

require "pathname"

# Use `Pathname` to send the filename and/or avoid paging a large file into memory:
file_metadata = anthropic.beta.files.upload(file: Pathname("/path/to/file"))

# Alternatively, pass file contents or a `StringIO` directly:
file_metadata = anthropic.beta.files.upload(file: File.read("/path/to/file"))

# Or, to control the filename and/or content type:
file = Anthropic::FilePart.new(File.read("/path/to/file"), filename: "/path/to/file", content_type: "...")
file_metadata = anthropic.beta.files.upload(file: file)

puts(file_metadata.id)

Note that you can also pass a raw IO descriptor, but this disables retries, as the library can't be sure if the descriptor is a file or pipe (which cannot be rewound).

Sorbet

This library provides comprehensive RBI definitions, and has no dependency on sorbet-runtime.

You can provide typesafe request parameters like so:

anthropic.messages.create(
  max_tokens: 1024,
  messages: [Anthropic::MessageParam.new(role: "user", content: "Hello, Claude")],
  model: :"claude-opus-4-6"
)

Or, equivalently:

# Hashes work, but are not typesafe:
anthropic.messages.create(
  max_tokens: 1024,
  messages: [{role: "user", content: "Hello, Claude"}],
  model: :"claude-opus-4-6"
)

# You can also splat a full Params class:
params = Anthropic::MessageCreateParams.new(
  max_tokens: 1024,
  messages: [Anthropic::MessageParam.new(role: "user", content: "Hello, Claude")],
  model: :"claude-opus-4-6"
)
anthropic.messages.create(**params)

Enums

Since this library does not depend on sorbet-runtime, it cannot provide T::Enum instances. Instead, we provide "tagged symbols" instead, which is always a primitive at runtime:

# :auto
puts(Anthropic::MessageCreateParams::ServiceTier::AUTO)

# Revealed type: `T.all(Anthropic::MessageCreateParams::ServiceTier, Symbol)`
T.reveal_type(Anthropic::MessageCreateParams::ServiceTier::AUTO)

Enum parameters have a "relaxed" type, so you can either pass in enum constants or their literal value:

# Using the enum constants preserves the tagged type information:
anthropic.messages.create(
  service_tier: Anthropic::MessageCreateParams::ServiceTier::AUTO,
  # ...
)

# Literal values are also permissible:
anthropic.messages.create(
  service_tier: :auto,
  # ...
)

BaseModel

All parameter and response objects inherit from Anthropic::Internal::Type::BaseModel, which provides several conveniences, including:

1. All fields, including unknown ones, are accessible with obj[:prop] syntax, and can be destructured with obj => {prop: prop} or pattern-matching syntax.

2. Structural equivalence for equality; if two API calls return the same values, comparing the responses with == will return true.

3. Both instances and the classes themselves can be pretty-printed.

4. Helpers such as #to_h, #deep_to_h, #to_json, and #to_yaml.

Concurrency and connection pooling

The Anthropic::Client instances are threadsafe, but are only fork-safe when there are no in-flight HTTP requests.

Each instance of Anthropic::Client has its own HTTP connection pool with a default size of 99. As such, we recommend instantiating the client once per application in most settings.

When all available connections from the pool are checked out, requests wait for a new connection to become available, with queue time counting towards the request timeout.

Unless otherwise specified, other classes in the SDK do not have locks protecting their underlying data structure.

Making custom or undocumented requests

Undocumented properties

You can send undocumented parameters to any endpoint, and read undocumented response properties, like so:

message =
  anthropic.messages.create(
    max_tokens: 1024,
    messages: [{role: "user", content: "Hello, Claude"}],
    model: :"claude-opus-4-6",
    request_options: {
      extra_query: {my_query_parameter: value},
      extra_body: {my_body_parameter: value},
      extra_headers: {"my-header": value}
    }
  )

puts(message[:my_undocumented_property])

Undocumented request params

If you want to explicitly send an extra param, you can do so with the extra_query, extra_body, and extra_headers under the request_options: parameter when making a request, as seen in the examples above.

Undocumented endpoints

To make requests to undocumented endpoints while retaining the benefit of auth, retries, and so on, you can make requests using client.request, like so:

response = client.request(
  method: :post,
  path: '/undocumented/endpoint',
  query: {"dog": "woof"},
  headers: {"useful-header": "interesting-value"},
  body: {"hello": "world"}
)

Platform integrations

Amazon Bedrock

This library also provides support for the Anthropic Bedrock API if you install this library with the aws-sdk-bedrockruntime gem.

You can then instantiate a separate Anthropic::BedrockClient class, and use AWS's standard guide for configuring credentials. It has the same API as the base Anthropic::Client class.

Note that the model ID required is different for Bedrock models, and, depending on the model you want to use, you will need to use either AWS's model ID for Anthropic models -- which can be found in AWS's Bedrock model catalog -- or an inference profile id (e.g. us.anthropic.claude-3-5-haiku-20241022-v1:0 for Claude 3.5 Haiku).

require "anthropic"

anthropic = Anthropic::BedrockClient.new

message = anthropic.messages.create(
  max_tokens: 1024,
  messages: [
    {
      role: "user",
      content: "Hello, Claude"
    }
  ],
  model: "anthropic.claude-opus-4-6-v1"
)

puts(message)

Google Vertex AI

This library also provides support for the Anthropic Vertex API if you install this library with the googleauth gem.

You can then import and instantiate a separate Anthropic::VertexClient class, and use Google's guide for configuring Application Default Credentials. It has the same API as the base Anthropic::Client class.

require "anthropic"

anthropic = Anthropic::VertexClient.new(region: "us-east5", project_id: "my-project-id")

message = anthropic.messages.create(
  max_tokens: 1024,
  messages: [
    {
      role: "user",
      content: "Hello, Claude"
    }
  ],
  model: "claude-opus-4-6"
)

puts(message)

Additional resources

• GitHub repository
• RubyDoc documentation
• API reference
• Streaming guide