Claude API — the complete guide to calling Claude on Kunavo

Q: How do I get a Claude API key?

Create a Kunavo account, generate a key at /app/keys, and pass it as the bearer token with base_url set to https://api.kunavo.com/v1. The same key works for the OpenAI-compatible endpoint and the native Anthropic Messages API. Full steps are in the Claude API key guide.

Q: How much does the Claude API cost?

On Kunavo, Claude runs 30–60% under Anthropic's list price: Haiku 4.5 $0.40/$2.00, Sonnet 4.6 $1.20/$6.00, Opus 4.7 $2.00/$10.00 (60% off list), Sonnet 5 $2.10/$10.50 and Fable 5 $7.00/$35.00 per 1M tokens (30% off list). Prompt caching bills cached input at 10% of the input rate.

Q: Can I use the Anthropic SDK or Messages API?

Yes. Claude is available on both the OpenAI-compatible /v1/chat/completions endpoint and the native Anthropic Messages API at /v1/messages, including cache_control and extended thinking.

Q: Which Claude model should I use?

claude-sonnet-4-6 is the balanced value default for most reasoning, RAG and coding, with claude-sonnet-5 the newest near-Opus coder. Use claude-haiku-4-5 for cheap high-volume tasks, claude-opus-4-7 for hard reasoning on a budget, and claude-fable-5 — Anthropic's most capable model — for frontier reasoning and long-horizon agents.

Claude is Anthropic's frontier family — the default choice for reasoning, coding and agentic workflows. Kunavo serves the whole family, from Haiku to the new Claude 5 generation (Fable 5, Sonnet 5), through both an OpenAI-compatible API and the native Anthropic Messages API, at 30–60% under Anthropic's list price depending on the model, on one Stripe-billed balance. This is the hub for everything Claude on Kunavo.

What you can do with the Claude API

Reasoning & analysis — long-context document analysis, multi-step problem solving.
Coding — generation, refactoring and review; Sonnet and Opus are strong agentic coders.
Vision — image understanding alongside text.
Tool use — function calling for agents and structured output.
Prompt caching — cache large stable context and pay 10% of the input rate on cache hits.

Get a key and make your first call

Create a key at /app/keys, then keep the OpenAI SDK and point base_url at Kunavo. Step-by-step (and the native Messages API form) is in how to get a Claude API key.

claude.py

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["KUNAVO_API_KEY"],
    base_url="https://api.kunavo.com/v1",
)

resp = client.chat.completions.create(
    model="claude-sonnet-4-6",
    messages=[{"role": "user", "content": "Explain the CAP theorem to a backend engineer."}],
)
print(resp.choices[0].message.content)

Prefer Anthropic's native shape, with cache_control and extended thinking? The same key works against the Messages API (/v1/messages).

Claude models, and when to use each

claude-haiku-4-5 — cheapest and fastest; high-volume classification, support, simple extraction.
claude-sonnet-4-6 — the balanced value default for reasoning, RAG and coding.
claude-sonnet-5 — the newest Sonnet: near-Opus coding and agentic quality at Sonnet cost.
claude-opus-4-7 — heavy reasoning at a 60%-off-list price.
claude-fable-5 — Anthropic's most capable model: frontier reasoning, long-horizon agents, 1M context.

Pricing

Claude on Kunavo runs 30–60% under Anthropic's list: the Claude 4.x generation is 60% off (Sonnet 4.6 at $1.20/$6.00 per 1M vs $3/$15), and the new Claude 5 family is 30% off (Sonnet 5 at $2.10/$10.50, Fable 5 at $7.00/$35.00). Full per-model rates, worked cost examples and the prompt-caching math are in the Claude API pricing guide.

Go deeper

FAQ

How do I get a Claude API key?

Create a Kunavo account, generate a key at /app/keys, and use it with base_url=https://api.kunavo.com/v1. See the full guide.

How much does the Claude API cost?

30–60% under Anthropic's list — Sonnet 4.6 at $1.20/$6.00 per 1M (60% off), Sonnet 5 at $2.10/$10.50 and Fable 5 at $7.00/$35.00 (30% off). See the pricing guide.

Can I use the Anthropic SDK or Messages API?

Yes — both the OpenAI-compatible endpoint and the native Messages API (/v1/messages) work on the same key.

Which Claude model should I use?

Sonnet 4.6 as the value default and Sonnet 5 as the newest near-Opus coder; Haiku 4.5 for cheap high-volume work; Opus 4.7 for hard reasoning on a budget; Fable 5 for the most demanding frontier and agentic work.