claude-sonnet-4-6

Quick example

curl https://api.reapi.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-6",
    "group": "default",
    "messages": [
      { "role": "user", "content": "Hello" }
    ],
    "stream": true,
    "max_tokens": 4096,
    "temperature": 0.7
  }'

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://api.reapi.ai/v1",
)

stream = client.chat.completions.create(
    model="claude-sonnet-4-6",
    messages=[{"role": "user", "content": "Hello"}],
    stream=True,
    max_tokens=4096,
    temperature=0.7,
    extra_body={"group": "default"},
)

for chunk in stream:
    delta = chunk.choices[0].delta.content or ""
    print(delta, end="", flush=True)

from anthropic import Anthropic

client = Anthropic(
    api_key="YOUR_API_KEY",
    base_url="https://api.reapi.ai",
)

with client.messages.stream(
    model="claude-sonnet-4-6",
    max_tokens=4096,
    messages=[{"role": "user", "content": "Hello"}],
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: "YOUR_API_KEY",
  baseURL: "https://api.reapi.ai/v1",
});

const stream = await client.chat.completions.create({
  model: "claude-sonnet-4-6",
  messages: [{ role: "user", content: "Hello" }],
  stream: true,
  max_tokens: 4096,
  temperature: 0.7,
  // @ts-expect-error — `group` is an api.reapi.ai-specific extension
  group: "default",
});

for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
}

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "net/http"
)

func main() {
    body, _ := json.Marshal(map[string]any{
        "model": "claude-sonnet-4-6",
        "group": "default",
        "messages": []map[string]string{
            {"role": "user", "content": "Hello"},
        },
        "stream":      true,
        "max_tokens":  4096,
        "temperature": 0.7,
    })
    req, _ := http.NewRequest("POST",
        "https://api.reapi.ai/v1/chat/completions", bytes.NewReader(body))
    req.Header.Set("Authorization", "Bearer YOUR_API_KEY")
    req.Header.Set("Content-Type", "application/json")

    resp, _ := http.DefaultClient.Do(req)
    defer resp.Body.Close()
    out, _ := io.ReadAll(resp.Body)
    fmt.Println(string(out))
}

Authentication

Every request needs a Bearer token. The Claude Sonnet 4.6 chat workspace lives on the api.reapi.ai platform — sign in there to create a key and top up tokens.

1. Open api.reapi.ai and sign in (or create an account).
2. Generate an API key under API Keys.
3. Top up tokens under Top Up (pay-as-you-go, billed in USD per 1M tokens — see api.reapi.ai/pricing).

Authorization: Bearer YOUR_API_KEY

Endpoints

POST https://api.reapi.ai/v1/chat/completions   # OpenAI-compatible
POST https://api.reapi.ai/v1/messages           # Anthropic-native

Both surfaces accept claude-sonnet-4-6. Pick whichever matches your SDK of record:

• /v1/chat/completions — drop-in for the OpenAI SDKs. Same request shape, same SSE wire format. Set base_url to https://api.reapi.ai/v1.
• /v1/messages — native Anthropic Messages format. Set base_url to https://api.reapi.ai for the Anthropic Python / TypeScript SDKs. Use this when you want the full Anthropic tool-use spec or native content blocks.

Request body — /v1/chat/completions

model — string, required

Must be "claude-sonnet-4-6". The value is echoed back in the response envelope.

messages — array, required

Conversation history as an array of message objects. Same shape as the OpenAI Chat Completions spec, plus content-parts for vision:

{
  "role": "system" | "user" | "assistant" | "tool",
  "content": "string OR content-parts array (text + image_url parts)"
}

max_tokens — integer, default 4096

Upper bound on output tokens. Anthropic's API requires max_tokens on every call, including streamed ones — even though the OpenAI SDKs treat it as optional. Set it generously (128000 is the hard cap); the model still stops at the natural end of its response.

stream — boolean, default false

When true, the response is streamed as server-sent events (SSE) with Content-Type: text/event-stream. Each event is a JSON delta in the OpenAI format, terminated by a data: [DONE] line.

temperature — number, default 1

Range 0.0 – 1.0. Sampling temperature. Anthropic recommends tuning either temperature or top_p, not both.

top_p — number, default 1

Range 0.0 – 1.0. Nucleus sampling cutoff.

tools / tool_choice — optional

Standard OpenAI tool-calling parameters. For Anthropic's native tool-use schema, call /v1/messages directly.

group — string, default "default"

api.reapi.ai-specific extension. Selects a token group on the gateway. Omit if default routing is fine.

Vision input

Send images alongside text via OpenAI content-parts:

{
  "model": "claude-sonnet-4-6",
  "max_tokens": 4096,
  "messages": [
    {
      "role": "user",
      "content": [
        { "type": "text", "text": "Summarise the error in this screenshot." },
        {
          "type": "image_url",
          "image_url": { "url": "https://example.com/screenshot.png" }
        }
      ]
    }
  ]
}

Supported formats: PNG, JPEG, GIF, WebP. Base64 URLs work too (data:image/png;base64,...). Each image counts toward the input token budget based on its resolution.

Response shape — /v1/chat/completions

Non-streaming (stream: false)

{
  "id": "chatcmpl-018f5a3a1b6e7d9f8c2b4d6e8f0a2c4e",
  "object": "chat.completion",
  "created": 1735000000,
  "model": "claude-sonnet-4-6",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "Hello! How can I help you today?"
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 12,
    "completion_tokens": 9,
    "total_tokens": 21
  }
}

Streaming (stream: true)

Content-Type: text/event-stream. Each data: line is a JSON delta in the OpenAI chunk format; the final event before [DONE] carries the finish_reason (stop / length / tool_calls / content_filter).

Pricing

Claude Sonnet 4.6 is billed pay-as-you-go in USD against your api.reapi.ai token balance. Current rates live on api.reapi.ai/pricing and in the pricing card at the top of the model page.

Per-call bill:

input_cost  = prompt_tokens     × input_rate  / 1,000,000
output_cost = completion_tokens × output_rate / 1,000,000

Failed requests are not charged.

Limits

Streams that hit the output cap finish with finish_reason: "length"; call again with a continuation message if you need more text.

Errors

The error envelope follows the OpenAI shape:

{
  "error": {
    "message": "...",
    "type": "invalid_request_error",
    "code": "..."
  }
}

Recipes

Minimum request

{
  "model": "claude-sonnet-4-6",
  "max_tokens": 4096,
  "messages": [
    { "role": "user", "content": "Summarise this in three sentences." }
  ]
}

Tool use (function calling)

{
  "model": "claude-sonnet-4-6",
  "max_tokens": 4096,
  "messages": [
    { "role": "user", "content": "What's the weather in Tokyo?" }
  ],
  "tools": [
    {
      "type": "function",
      "function": {
        "name": "get_weather",
        "description": "Look up the current weather for a city.",
        "parameters": {
          "type": "object",
          "properties": { "city": { "type": "string" } },
          "required": ["city"]
        }
      }
    }
  ],
  "tool_choice": "auto"
}

Vision

{
  "model": "claude-sonnet-4-6",
  "max_tokens": 4096,
  "messages": [
    {
      "role": "user",
      "content": [
        { "type": "text", "text": "Read the error in this screenshot and suggest a fix." },
        {
          "type": "image_url",
          "image_url": { "url": "https://your-cdn.com/screenshot.png" }
        }
      ]
    }
  ]
}

When to pick Claude Sonnet 4.6 over Claude Opus 4.7

Both share the same endpoint, the same context window, and the same OpenAI-compatible wire format — switching is a one-line change in the model field. Pick Claude Sonnet 4.6 when:

• Production chat traffic where time-to-first-token shows up in user-experience metrics.
• Code review and PR triage that runs across high volume.
• Mid-complexity agents where Claude-grade reasoning is enough and Opus-tier reasoning would be overkill.
• Default routing — use Sonnet as the everyday model and escalate to Opus for the genuinely hard turns.

Pick Claude Opus 4.7 for high-stakes coding, large refactors, complex multi-step agents, and long-context analysis where output quality dominates the decision.

Tips

• Set max_tokens generously. Anthropic enforces it strictly; the model still stops at the natural end of its response, but a low cap will truncate before the real ending.
• Stream by default for chat UX. Sonnet's lower time-to-first-token makes the perceived latency advantage especially visible in streamed responses.
• Tune temperature or top_p, not both. Mixing them produces results that are hard to reason about.
• Use Sonnet as the default and escalate to Opus. The cleanest production pattern: route everything to Sonnet, switch to Opus on the calls where quality matters most.

Related

• Authentication
• Quickstart
• Errors catalog