Claude Sonnet 5.5

    anthropic/claude-sonnet-5.5
    Playground

    Sonnet-class model for well-scoped everyday work, with stronger feature building, bug fixing, and office deliverables than the prior generation, suited to responsive agentic loops.

    ReasoningCodingBalanced PerformanceOfficeAgent CodingAgent
    Modality
    Input / Output Pricing
    $2 / $10M tokens
    Context
    1M
    Release date
    2026-09-28

    Pricing

    SpecificationPrice
    Input$2/ M tokens
    Output$10/ M tokens
    Cache read$0.1/ M tokens
    Cache write$2.5/ M tokens
    Cache write 1h$4/ M tokens

    Quick Start

    Paste and run the sample code below. The Gate.AI API is OpenAI-compatible—most SDKs only need a new base URL. To switch models, change the model ID.

    1

    Get your API key

    Sign in to the Gate.AI console and create a new key under "API Keys". Keep it safe and send it via the Authorization header on every request.

    Create a key in the console
    2

    Make a request

    Send a POST request to the Chat Completions endpoint with a model ID and an array of messages to get a reply.

    POSThttps://api.gate.ai/anthropic/v1/messages
    curl --location "https://api.gate.ai/anthropic/v1/messages" \
  --header "x-api-key: {API_KEY}" \
  --header "anthropic-version: 2023-06-01" \
  --header "Content-Type: application/json" \
  --data '{
  "model": "claude-sonnet-5.5",
  "max_tokens": 256,
  "messages": [
    {"role": "user", "content": "Hello"}
  ]
}'
    3

    Handle the response \\& streaming

    By default a full JSON response is returned. Add "stream": true to the request body to receive incremental chunks over SSE.

    POSThttps://api.gate.ai/anthropic/v1/messages
    curl --no-buffer --location "https://api.gate.ai/anthropic/v1/messages" \
  --header "x-api-key: {API_KEY}" \
  --header "anthropic-version: 2023-06-01" \
  --header "Content-Type: application/json" \
  --data '{
  "model": "claude-sonnet-5.5",
  "max_tokens": 256,
  "messages": [
    {"role": "user", "content": "Hello"}
  ],
  "stream": true
}'

    Endpoint

    Create messages in Anthropic Messages API format with text, images, tools, and extended thinking.

    POSThttps://api.gate.ai/anthropic/v1/messages
    Field
    Value
    x-api-key
    Gate.AI API key header with the value {API_KEY}
    anthropic-version
    Anthropic protocol version; for example 2023-06-01
    Content-Type
    Request content type, fixed to application/json
    model
    Model ID; the current model is claude-sonnet-5.5
    max_tokens
    Maximum number of tokens the model may generate
    messages
    Ordered array of Anthropic messages
    stream
    Whether to return the result as an SSE stream

    Related Models

    Claude Haiku 5.5

    Small, fast model for high-volume, latency-sensitive summarization, subagents, and browser use, with stronger coding and computer use than the prior generation.

    Claude Opus 5.5

    Successor to Opus 5 for demanding reasoning, coding, and long-horizon agent work; excels at multi-step changes across large codebases and sustained knowledge tasks.

    Claude Opus 5

    Flagship model for demanding reasoning, coding, and long-horizon agentic work, spanning end-to-end software, code review, parallel subagent coordination, visual analysis of charts and documents, and complex office deliverables.

    Claude Sonnet 5

    Coding and agent quality approach the frontier, with native reasoning built in, well-suited for complex planning and long-horizon professional tasks that require cross-step consistency.

    Claude Fable 5

    Claude Fable 5 is Anthropic’s advanced long-horizon reasoning model, supporting text, image, and file inputs with text output. It features reasoning capabilities and a 1M-token context window, making it suitable for autonomous knowledge work, software development, and complex multi-step tasks.

    Claude Opus 4.8

    Opus family flagship with reasoning. Suited for long-horizon autonomous agents, large-codebase analysis, and multimodal knowledge work.

    Claude Opus 4.8 beta

    Opus family flagship with reasoning. Suited for long-horizon autonomous agents, large-codebase analysis, and multimodal knowledge work.

    Claude Opus 4.7 beta

    Built for long-running async agents, excelling at complex multi-step tasks and end-to-end workflow execution.

    Claude Opus 4.7

    Built for long-running async agents, excelling at complex multi-step tasks and end-to-end workflow execution.

    Claude Sonnet 4.6

    Best balance of quality and cost from Anthropic.