Claude Opus 5.5 API

anthropic/claude-opus-5.5
Claude Opus 5.5 is Anthropic's flagship model for demanding reasoning, coding and long-horizon agentic work. It performs at the level of Claude Fable 5.1 on most work at a lower price than Claude Opus 5.
Context
1M tokens
Input
$5.2 / 1M tokens
Output
$26 / 1M tokens
Released
Sep 22, 2026

How to use Claude Opus 5.5 API

Install any OpenAI-compatible SDK, point it at api.aimlapi.com/v1, and set the model to anthropic/claude-opus-5.5.
import requests

r = requests.post(
    "https://api.aimlapi.com/v1/chat/completions",
    headers={"Authorization": "Bearer " + AIMLAPI_KEY},
    json={
      "model": "anthropic/claude-opus-5.5",
      "messages": [
        {
          "role": "user",
          "content": "Hello!"
        }
      ]
    },
)
print(r.json())
const r = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "anthropic/claude-opus-5.5",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }),
});
console.log(await r.json());
curl -X POST https://api.aimlapi.com/v1/chat/completions \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"anthropic/claude-opus-5.5","messages":[{"role":"user","content":"Hello!"}]}'

OpenAI-compatible — swap the base URL and it works with your existing SDK.

Claude Opus 5.5 API Pricing

TypePrice
Input
$5.2 / 1M tokens
Output
$26 / 1M tokens
Cached input
$0.26 / 1M tokens

Cache writes are billed at $6.5 / 1M tokens.

Claude Opus 5.5 vs other models

ModelInputOutputContextBest for
$5.2 / 1M tokens
$26 / 1M tokens
1M tokens
Complex agentic coding and enterprise workflows
$6.5 / 1M tokens
$32.5 / 1M tokens
1M tokens
Complex agentic coding and enterprise workflows
$13 / 1M tokens
$65 / 1M tokens
1M tokens
Long-horizon agentic coding and research
$6.877 / 1M tokens
$32.5 / 1M tokens
1M tokens
Chat + assistants

Frequently asked questions

Yes. Claude Opus 5.5 is available on AI/ML API through the OpenAI-compatible chat completions endpoint under the model ID anthropic/claude-opus-5.5.

Anthropic released Claude Opus 5.5 on 22 September 2026 as the first model in the Claude 5.5 family.

On AI/ML API, Claude Opus 5.5 costs $5.2 per million input tokens, $26 per million output tokens and $0.26 per million cached input tokens. Cache writes are billed at $6.5 per million tokens.

Anthropic reports that Opus 5.5 performs at the level of Claude Fable 5.1 on most work, costs about 40% less to run than Opus 5 and generates output more than 30% faster. The biggest gains are in agentic coding: Terminal-Bench 4.0 goes from 52.3% on Opus 5 to 66.4%, and CursorBench 4.0 from 46.6% to 57.8%.

Change the model ID from anthropic/claude-opus-5 to anthropic/claude-opus-5.5. Both are served through the same chat completions endpoint on AI/ML API, so nothing else in your integration needs to change.

Start building with Claude Opus 5.5

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