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Claude Sonnet 4

chatCodeReasoningTool calling

Claude Sonnet 4 is served on Synthorai behind the OpenAI-compatible /v1/chat/completions endpoint: swap the base_url, keep your code.

Input
$3/M
Output
$15/M
Cache read
$0.3/M
Context
200K
vs GPT-4o
~40% cheaper

Benchmarks

Claude Sonnet 4: 57 published, but no benchmark it shares with enough other models to compare.

Claude Sonnet 4 other models measured peer average ★ no peer scored higher
EmbSpatialBench no thinking
67.5%
AI2D (test) no thinking
82.6%

Vendor-published: Alibaba (Qwen)

Price in context

Where the price sits among 68 comparable models

Input$3/M
$0.1 · Dola Seed 2.0 Mini GPT-5.4 Pro · $30
Output$15/M
$0.275 · DeepSeek V4 Flash GPT-5.4 Pro · $180
Cache read$0.3/M
$0.01 · Claude Haiku 5.5 GPT-5.4 Pro · $15

The bar shows how this model’s price compares with every other model of the same kind on Synthorai. The cheapest and the most expensive are named at each end. These are base rates; batch, region and cache-write discounts are on the pricing page.

Specs & limits

Prompt caching

How it caches explicit (opt-in)
Min prefix 1,024
Lifetime 5m default, 1h option
Write cost 1.25x (5m) / 2x (1h)

Use Claude Sonnet 4 in 30 seconds

OpenAI-compatible: swap the base_url, keep your SDK. POST /v1/chat/completions

from openai import OpenAI

client = OpenAI(
    base_url="https://synthorai.io/v1",
    api_key="sk-syn-...",
)

resp = client.chat.completions.create(
    model="claude-sonnet-4",
    messages=[{"role": "user", "content": "Summarize this diff"}],
    reasoning_effort="medium",
)
print(resp.choices[0].message.content)

FAQ

Is the Claude Sonnet 4 API free to try?

Yes: new accounts get 10 trial calls and up to $1 in free credit, no card required. At $3/M input tokens, that credit alone covers roughly 41 requests of ~8K tokens against Claude Sonnet 4.

How much does Claude Sonnet 4 cost?

Claude Sonnet 4 costs $3 per million input tokens and $15 per million output tokens on Synthorai. That is the provider's list price, with no platform markup. Cached input tokens bill at $0.3/M.

What is Claude Sonnet 4's context window?

Claude Sonnet 4 has a context window of 200K tokens on Synthorai.

Does Claude Sonnet 4 support prompt caching?

Yes, via opt-in: mark stable prefixes with cache_control breakpoints. Cached input tokens bill at $0.3/M vs $3/M uncached; prompts need a 1,024-token stable prefix to cache (TTL 5m default, 1h option). Prompt caching guide →

How do I get access to Claude Sonnet 4?

Point your existing OpenAI SDK at base_url="https://synthorai.io/v1", set model="claude-sonnet-4", and you're done. One API key covers every model on the gateway.

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Every value on this page is transcribed from the vendor's own documentation, linked above, and carries the date it was checked. Prices are compared across the catalogue; specification values that vendors define differently are shown with the difference stated rather than charted. Nothing here is measured by us, and nothing is scored.

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