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OpenKey

Claude Sonnet 5

AnthropicReleased Jun 30, 2026

Sonnet 5 is Anthropic's most capable Sonnet-class model, with frontier performance across coding, agents, and professional work. It supports adaptive thinking with selectable reasoning effort levels (low, medium, high, max,...

Try in playground
Context window
1M tokens
Max output
128K tokens
Input
text, image, file
Output
text
Tokenizer
Claude
Released
Jun 30, 2026
Reasoning
optional

Pricing

Per 1M tokens. The provider price and our flat 3% fee are separate columns — what you pay is their sum.

Per 1M tokensProvider+ 3% feeYou pay
Input$2.00$0.060$2.06
Output$10.00$0.300$10.30
Cache read$0.200$0.0060$0.206
Cache write$2.50$0.075$2.58

Benchmarks

Artificial Analysis

Intelligence index
53.4
Coding index
71.5
Agentic index
46.7

Supported parameters

  • include_reasoning
  • max_completion_tokens
  • max_tokens
  • reasoning
  • response_format
  • stop
  • structured_outputs
  • tool_choice
  • tools
  • verbosity

Call it

OpenAI-compatible: point your SDK at api.openkey.ai/v1 and use model anthropic/claude-sonnet-5.

Code sample language
curl https://api.openkey.ai/v1/chat/completions \
  -H "Authorization: Bearer $OPENKEY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-sonnet-5",
    "messages": [{"role": "user", "content": "Hello"}]
  }'
import os
from openai import OpenAI

client = OpenAI(
    base_url="https://api.openkey.ai/v1",
    api_key=os.environ["OPENKEY_API_KEY"],
)

completion = client.chat.completions.create(
    model="anthropic/claude-sonnet-5",
    messages=[{"role": "user", "content": "Hello"}],
)
print(completion.choices[0].message.content)
import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://api.openkey.ai/v1",
  apiKey: process.env.OPENKEY_API_KEY,
});

const completion = await client.chat.completions.create({
  model: "anthropic/claude-sonnet-5",
  messages: [{ role: "user", content: "Hello" }],
});
console.log(completion.choices[0].message.content);

Questions

How much does Claude Sonnet 5 cost via API?
Through OpenKey, Claude Sonnet 5 costs $2.06 per 1M input tokens and $10.30 per 1M output tokens. That is the provider price ($2.00 / $10.00) plus a flat 3% fee — nothing else.
What is Claude Sonnet 5's context window?
Claude Sonnet 5 accepts up to 1M tokens of context and returns up to 128K tokens per request.
Is Claude Sonnet 5 OpenAI-compatible?
Yes. Send requests to OpenKey's /v1/chat/completions endpoint with model "anthropic/claude-sonnet-5" using any OpenAI SDK — only the base URL and API key change.
What inputs does Claude Sonnet 5 support?
Claude Sonnet 5 accepts text, image, file input and produces text output.

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