Claude Sonnet 4.6

Name: Claude Sonnet 4.6
Brand: Anthropic
SKU: claude-sonnet-4-6
Price: 3.6 USD
Availability: InStock

MultimodalLegacyAvailable

by Anthropicclaude-sonnet-4-6

Anthropic's balanced mid-tier model from February 2026. Best price/performance for production workloads: 5x cheaper than Opus, near-flagship quality.

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Price · 1M in / out: $3.60 / $18.00
Context: 1,000,000 tokens
Max. output: 128,000 tokens
Input → output: Text + Image → Text
Developer: Anthropic
Updated: September 23, 2026

This is an older version of the model.

Newer version available: Claude Sonnet 5

Playground

Try Claude Sonnet 4.6

Chat

$3.60/1M in

Send a message. The answer arrives in full once the model is done (no streaming).

System prompt

Max. answer length (tokens)

TemperatureModel default

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This run

at most $0.0185 · 1.85 credits reserved

Billed by the tokens actually used; the unused part of the reservation is refunded.

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10 free credits ($0.10) when you sign up with Google

Usable 24 hours after sign-up, up to 5 runs per day and at most 2 credits per run. Other sign-in methods start without credits. Enough for 5 runs of this model.

About Claude Sonnet 4.6

TL;DRAs of September 23, 2026

Claude Sonnet 4.6 is a model by Anthropic in the Multimodal category. On Railwail, Claude Sonnet 4.6 costs $3.60 per 1M input tokens and $18.00 per 1M output tokens. The context window holds 1,000,000 tokens, and one response can be up to 128,000 tokens long. Newer version: Claude Sonnet 5.

Released February 17, 2026, Claude Sonnet 4.6 is the workhorse of the 4.x Claude family. Delivers near-Opus quality on most coding, writing and analysis tasks at one-fifth the cost. 1M-token context window, extended thinking, full vision support, and the same tool-use loop as Opus 4.7. Suited to production agents, developer copilots, customer support, and most enterprise API scenarios.

Background

About Anthropic

Founded 2021 · San Francisco, USA

Anthropic was founded in 2021 by Dario and Daniela Amodei together with senior researchers from OpenAI. The company is a Public Benefit Corporation focused on AI safety. Key research milestones include Constitutional AI (2022), Sparse Autoencoders for interpretability, and the Claude model family launched in March 2023. Claude Sonnet has been Anthropic's flagship 'balanced' tier since the Claude 3 family, with major releases including Sonnet 3.5 (June 2024), Sonnet 3.7 with extended thinking (February 2025), Sonnet 4 (May 2025), Sonnet 4.5 (late 2025) and Sonnet 4.6 (February 17, 2026). Investors include Google, Amazon, Spark Capital and Lightspeed; total funding exceeds $20 billion with a 2026 valuation above $150 billion.

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Architecture

Decoder-only Transformer (balanced production model with extended thinking)

Claude Sonnet 4.6 was released February 17, 2026 as the mid-tier workhorse of the Claude 4.x family. It is a decoder-only Transformer engineered to deliver near-Opus quality at one-fifth the cost. Pretraining used the same multi-trillion-token mixture as Opus 4.7 with a knowledge cutoff in early 2026. Post-training combined RLHF, Constitutional AI, RLAIF, and reinforcement learning against verifiable rewards on coding, math and tool-use trajectories. Sonnet 4.6 supports the full Opus feature set: extended thinking mode, native vision, computer use, parallel tool calling, and 200K context. The training emphasis was on efficiency: Sonnet 4.6 outperforms Opus 4 on most coding and writing benchmarks while running ~2x faster and at one-fifth the cost. Anthropic positions Sonnet 4.6 as the recommended default for production workloads.

Parameters: Undisclosed (estimated dense model in the 100B-range)
Context: 200,000 tokens

Capabilities

Near-Opus quality on most coding, writing and analysis tasks at 5x lower cost
Extended thinking mode with adjustable thinking budget
200K token context window with strong needle-in-haystack recall
Multimodal input: text, images, PDFs, charts and diagrams
Native computer use: screenshots, mouse and keyboard control
Parallel tool calling and stable multi-turn agent loops
Strong instruction following including XML tags, schemas and strict JSON
Constitutional-AI alignment with low refusal rate on benign questions
Multilingual fluency across 20+ languages
~2x faster latency than Opus 4.7 on equivalent tasks
Best for: production agents, developer copilots, customer support, most enterprise API scenarios.

Training & license

Pretrained on a curated multi-trillion-token mixture identical to the Opus 4.7 corpus, with heavy quality filtering, deduplication and copyright screening. Knowledge cutoff in early 2026. Post-training uses RLHF, Constitutional AI, RLAIF and RL against verifiable rewards.

License: Proprietary commercial license via Anthropic API, Amazon Bedrock and Google Vertex AI. Commercial use permitted under Anthropic's Usage Policy.

Safety testing: Deployed under Responsible Scaling Policy ASL-3 safeguards with constitutional classifiers, automated red-teaming, third-party evaluations and a public Bug Bounty programme.

Known limitations

Below Opus 4.7 on the hardest agentic and reasoning benchmarks
No native audio or video input
Knowledge cutoff in early 2026; needs tool use for fresh information
Will refuse some legitimate red-team and security research prompts
No fine-tuning available to external customers

Research papers

Pricing

Prices in US dollars. Usage is charged from prepaid credits.

Input	$3.60 / 1M tokens
Output	$18.00 / 1M tokens

Billed by the tokens each request actually uses.
1 credit = $0.01

Cost calculator

Price calculator

Input tokens

/ req.

Output tokens

/ req.

Requests

Total

$1.26

126 credits

Per request

$0.0126 · 1.26 credits

Each request is rounded up to 0.01 credits.

API

Call Claude Sonnet 4.6 with your Railwail API key. Use this model ID in the request:

claude-sonnet-4-6API documentation Get an API key

curl https://railwail.com/api/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-6",
    "messages": [
      {
        "role": "user",
        "content": "Explain what a vector database is in two sentences."
      }
    ],
    "max_tokens": 1024
  }'

import os
from openai import OpenAI

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

completion = client.chat.completions.create(
    model="claude-sonnet-4-6",
    messages=[
        {
            "role": "user",
            "content": "Explain what a vector database is in two sentences.",
        },
    ],
    max_tokens=1024,
)

print(completion.choices[0].message.content)

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://railwail.com/api/v1",
});

const completion = await client.chat.completions.create({
  model: "claude-sonnet-4-6",
  messages: [
    {
      role: "user",
      content: "Explain what a vector database is in two sentences."
    }
  ],
  max_tokens: 1024
});

console.log(completion.choices[0].message.content);

// npm install railwail
import railwail from "railwail";

const rw = railwail(process.env.RAILWAIL_API_KEY);

const res = await rw.chat("claude-sonnet-4-6", [
  { role: "user", content: "Explain what a vector database is in two sentences." },
], { max_tokens: 1024 });

console.log(res.choices[0].message.content);

Set your key as RAILWAIL_API_KEYCreate API key

Specifications

Model ID: claude-sonnet-4-6
Developer: Anthropic
Category: Multimodal
Input: Text, Image
Output: Text
Context window: 1,000,000 tokens
Max. output: 128,000 tokens
Billing: By usage (tokens or GPU time)
Released: February 17, 2026
Lifecycle: Legacy
Model size: Undisclosed (estimated dense model in the 100B-range)
License: Proprietary commercial license via Anthropic API, Amazon Bedrock and Google Vertex AI. Commercial use permitted under Anthropic's Usage Policy.
Catalog entry updated: September 23, 2026

Input parameters

Inputs and settings from the model's input schema. The example in the API section shows which of them the API accepts.

ParameterTypeDefaultAllowed values

promptrequired
User message
Type: Text
Default: –
Allowed values: up to 32,000 characters
top_p
Type: Number
Default: 1
Allowed values: 0 to 1
stream
Type: Yes/no
Default: false
Allowed values: –
image_url
Optional image URL to analyze
Type: Text
Default: –
Allowed values: –
max_tokens
Type: Integer
Default: 4096
Allowed values: 1 to 32,000
temperature
Type: Number
Default: 1
Allowed values: 0 to 1
system_prompt
Optional system instruction
Type: Text
Default: –
Allowed values: up to 8,000 characters

Use cases

What it is used for

Production coding assistants and IDE copilots
Customer support chatbots and triage agents
Enterprise document analysis and summarisation
Multi-turn agent loops with tool use
Computer-use automation
Content generation and editing pipelines

All models in Multimodal

Frequently asked questions

What is Claude Sonnet 4.6?

Claude Sonnet 4.6 is a model by Anthropic in the Multimodal category. On Railwail you can call it with an API key through the Railwail API.

How much does Claude Sonnet 4.6 cost on Railwail?

On Railwail, Claude Sonnet 4.6 costs $3.60 per 1M input tokens and $18.00 per 1M output tokens. You are charged for what each request actually uses. Usage is paid from prepaid credits; 1 credit equals $0.01.

What is the context window of Claude Sonnet 4.6?

The context window of Claude Sonnet 4.6 holds 1,000,000 tokens. One response can be up to 128,000 tokens long.

How fast is Claude Sonnet 4.6?

There are not enough measured runs of Claude Sonnet 4.6 on Railwail yet to state a run time. It depends on the input, the settings and the load at the provider.

Is Claude Sonnet 4.6 better than Claude Sonnet 5?

That depends on the task. Claude Sonnet 4.6 (Anthropic) and Claude Sonnet 5 (Anthropic) are both models in the Multimodal category. The comparison page shows their prices and specifications side by side.

Compare Claude Sonnet 4.6 and Claude Sonnet 5

Can Claude Sonnet 4.6 process images?

Yes. Claude Sonnet 4.6 accepts images as input in addition to text.

How do I use Claude Sonnet 4.6 through the API?

Create a Railwail API key and send your request with the model ID claude-sonnet-4-6. Code examples for curl, Python and JavaScript are in the API section of this page.

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Use Claude Sonnet 4.6 via the API

One API key for every model on Railwail. Usage is charged from prepaid credits, 1 credit = $0.01.

Get API key Browse all models