Anthropic
Operational· 100% uptime, 7 days

Claude Sonnet 5.5 API

The Claude Sonnet 5.5 API: Anthropic's fastest Sonnet, 60% below list price.

Price per 1M tokens60%off
Input
$0.80$2.00
Output
$4.00$10.00
Cached input
$0.08
Get your API keyTry it in the playground
Model IDclaude-sonnet-5-5
chat.py
from openai import OpenAI
client = OpenAI(
    base_url="https://api.zurelay.com/v1",
    api_key="YOUR_ZURELAY_KEY",
)
stream = client.chat.completions.create(
    model="claude-sonnet-5-5",
    messages=[{"role": "user", "content": "Explain quicksort in two sentences."}],
    stream=True,
)
for chunk in stream:
    if chunk.choices:
        print(chunk.choices[0].delta.content or "", end="")

Base URL https://api.zurelay.com/v1. Works with any OpenAI SDK, and the Anthropic SDK and Claude Code.

Context window
1M tokens
Max output
128K tokens
Input
Text, Image
Output
Text
Released
Sep 28, 2026
Uptime, 7 days
100%

Pricing

Claude Sonnet 5.5 API pricing. A fraction of the list price.

Pay as you go from prepaid credit, with no subscription and no minimum. Requests that fail are never billed.

RatezurelayAnthropic listYou save
Input
per 1M tokens
$0.80$2.0060%off
Output
per 1M tokens
$4.00$10.0060%off
Cached input
per 1M tokens
$0.08——

One rate at every prompt length, up to the full 1M context window. Streaming, tool calls and structured outputs cost nothing extra.

Savings calculator

Move the sliders to your monthly usage.

Input tokens per month50M
Output tokens per month10M
zurelay
$80.00
Anthropic list price
$200.00
You save every month$120.00

$1,440 a year

Overview

What is Claude Sonnet 5.5?

Claude Sonnet 5.5 is Anthropic's current Sonnet model, which Anthropic calls its best combination of speed and intelligence. The zurelay Claude Sonnet 5.5 API serves it through an OpenAI-compatible or Anthropic-compatible endpoint at 60% below list price, for teams running coding, agent and document work at volume.

Claude Sonnet 5.5 was released on September 28, 2026, as the second model in Anthropic's 5.5 family. It replaces Claude Sonnet 5 at the same list price. On zurelay, the Claude Sonnet 5.5 API uses the model ID claude-sonnet-5-5 and costs $0.80 per 1M input tokens and $4.00 per 1M output tokens.

Anthropic says Sonnet 5.5 generates output more than 30% faster than Sonnet 5, which makes it the fastest Sonnet so far. In Anthropic's testing it also costs up to 30% less per task, because it needs fewer tokens to finish. It is strongest at well-scoped everyday tasks, bug fixes, and polished documents, slides and spreadsheets, and Anthropic notes a sharp eye for design. It is the first Sonnet model to beat Pokémon Red working only from screenshots, a test of long-horizon work and image understanding.

The specs: a 1M-token context window, up to 128K output tokens per request, text and image input, and text output. Adaptive thinking is on by default and effort defaults to high. Unlike Opus 5.5, Sonnet 5.5 lets you turn off up-front thinking with the between_tools setting, which suits latency-sensitive routes. Anthropic recalibrated the effort levels, so re-test your settings instead of copying them from Sonnet 5. Sampling parameters (temperature, top_p, top_k) must stay at their defaults.

Sonnet 5.5 or Opus 5.5? Anthropic positions Sonnet 5.5 as a faster, lower-cost complement to Opus 5.5, while Opus stays stronger at complex, open-ended work that needs sustained judgment. On zurelay both run on the same key, so you can send routine traffic to Sonnet and escalate hard cases to Opus without a second integration.

Strengths

Where Claude Sonnet 5.5 shines. And what teams build with it.

01

Speed

Anthropic measured output more than 30% faster than Sonnet 5. Its comparative latency is rated fast, a step quicker than Opus 5.5.

02

Lower cost per task

Same list price as Sonnet 5, but up to 30% lower cost per task in Anthropic's testing, because the model reaches the answer in fewer tokens.

03

Documents, slides and spreadsheets

Anthropic calls out polished documents, slides and spreadsheets, plus a sharp eye for design.

04

Close to Opus on knowledge work

On the GDPval-AA knowledge-work benchmark that Anthropic reports, Sonnet 5.5 scores almost level with Opus 5.5.

Use cases

  • Coding assistants and bug fixes

    Handle well-scoped tickets, bug fixes and code edits with fast turnaround in IDE tools, CLIs and CI.

  • Agents at volume

    Run multi-step tool-calling agents where cost per task and latency matter, and turn off up-front thinking on the simplest routes.

  • Docs, slides and spreadsheets

    Generate reports, slide content and spreadsheet logic that need little cleanup before they ship.

  • Chat and support

    Serve user-facing chat where response time matters. Anthropic suggests starting chat workloads at low or medium effort.

Get started

Call Claude Sonnet 5.5 in three steps.

No waitlist and no new SDK. If your code already talks to OpenAI, it already talks to zurelay.

  1. 1

    Create a key

    Sign up, add credit and create an API key. Set a monthly budget or a rate limit per key if you like.

    Get your API key
  2. 2

    Point your SDK at zurelay

    Change the base URL. Everything else in your code stays the same.

    https://api.zurelay.com/v1
  3. 3

    Use claude-sonnet-5-5

    Send chat completions as usual. Streaming, tool calls and usage reporting work as you expect.

    claude-sonnet-5-5

Works with the tools you already use

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Pick Claude Opus 5.5 for complex, open-ended work that needs sustained judgment, such as large migrations or long agent runs.

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Pick Nano Banana Pro to generate images; Sonnet 5.5 reads images but only returns text.

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Try GPT-6 Luna, which has a much lower list price, for bulk simple text jobs once your evals show it holds up.

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FAQ

Claude Sonnet 5.5 API questions.

Anything else, write to sales@zurelay.com and an engineer will answer.

How much does the Claude Sonnet 5.5 API cost on zurelay?

zurelay charges $0.80 per 1M input tokens and $4.00 per 1M output tokens, with cached input at $0.08. Anthropic's list price is $2.00 input and $10.00 output, so you save 60%. The rate is the same across the full context window.

Is there a cheaper Claude Sonnet API than Anthropic's?

Yes. zurelay serves claude-sonnet-5-5 at 60% below Anthropic's list price. It is the same model, not a smaller substitute. Switch the base URL and key and keep the rest of your code.

How do I call Claude Sonnet 5.5 with the OpenAI SDK?

Create a zurelay API key, set the base URL to https://api.zurelay.com/v1 and set the model to claude-sonnet-5-5. Chat completions, streaming and tool calls work as they do with OpenAI. Leave temperature and top_p unset, and keep tool_choice on auto: this model rejects non-default sampling values and forced tool choice.

Can I use the Anthropic SDK or Claude Code with Claude Sonnet 5.5?

Yes. zurelay serves the Anthropic Messages API too. Set the base URL, or ANTHROPIC_BASE_URL for Claude Code, to https://api.zurelay.com with no /v1, and authenticate with your zurelay key. The same key works for every model in the catalog.

Should I use Claude Sonnet 5.5 or Claude Opus 5.5?

Start with Sonnet 5.5 for well-scoped tasks, bug fixes, documents and chat, where its speed and lower price pay off. Move to Opus 5.5 for complex, open-ended work such as large refactors, long agent runs or careful analysis. Both are on one zurelay key, so you can route per request.

What is the Claude Sonnet 5.5 context window?

Claude Sonnet 5.5 has a 1M-token context window and returns up to 128K output tokens per request. Stream long responses so tokens arrive as they are generated.

Can I turn off thinking on Claude Sonnet 5.5?

Not with thinking type disabled, which returns an error on this model. Send thinking type between_tools instead. It turns off up-front thinking and works at high effort or below. For xhigh or max effort, keep adaptive thinking on.

Does the zurelay Claude Sonnet 5.5 API support streaming, and what are the rate limits?

Streaming works on both chat completions and the Messages API, using server-sent events. You set your own requests-per-minute cap and spend limit on each key. If a route errors, times out or hits a rate limit, zurelay retries on another route for the same model, and failed attempts are not billed.

Are Claude Sonnet 5.5 responses on zurelay identical to Anthropic's API?

Your requests run on Claude Sonnet 5.5 itself, and zurelay never swaps in a different or smaller model. Output is sampled, so the wording varies between calls on any API, but capability and behavior are the model's own. zurelay is an independent service and is not affiliated with or endorsed by Anthropic.

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