Claude Sonnet 4.6 & Opus 4 API Guide: New Models Setup & Benchmarks

TL;DR

• Claude Sonnet 4.6 is Anthropic's everyday workhorse for 2026 — meaningfully better than 4.5 on complex coding tasks, same price point.
• Claude Opus 4 targets high-complexity reasoning; token cost is ~5x Sonnet, worth it only for genuinely hard tasks.
• CodeGateway setup: change base_url to https://api.codegateway.dev/v1, keep everything else identical.

Model Specs

Prices from Anthropic's official documentation (May 2026). Subject to change — check Anthropic's model page for current rates.

When accessing through CodeGateway, multiply by the flat 1.07× markup (the same for every account, regardless of spend). See CodeGateway pricing tiers.

When to Use Each Model

Sonnet 4.6

• Daily coding: completions, code review, refactoring, bug triage
• Content generation: technical docs, blog posts, API documentation
• Long conversations: multi-turn debugging sessions, context-heavy chat
• Default for Claude Code: most Claude Code tasks run on Sonnet — strong price-performance ratio
• High-volume batch jobs: parallel processing of moderate-complexity requests

Opus 4

• High-complexity math and logic: algorithm design, mathematical proof verification, optimization problems
• Long-chain agent planning: multi-step orchestration where accuracy is critical
• Arbiter in sub-agent architectures: final verdict when two Workers disagree (see Sub-agents Tutorial)
• Single high-stakes outputs: when you need one shot at maximum quality

Rule of thumb: Sonnet 4.6 handles 95% of tasks adequately. Reach for Opus 4 only when Sonnet's quality is measurably insufficient and the task value justifies 5x the cost.

Setup via CodeGateway (Python)

import anthropic

# Only change: base_url points to CodeGateway. Everything else is identical to Anthropic's SDK.
client = anthropic.Anthropic(
    api_key="your-codegateway-api-key",
    base_url="https://api.codegateway.dev/v1"
)

# Sonnet 4.6 — everyday use
response = client.messages.create(
    model="claude-sonnet-4-6",
    max_tokens=2048,
    messages=[{
        "role": "user",
        "content": "Review this Python function for performance issues and edge cases:\n\n[your code here]"
    }]
)
print(response.content[0].text)

# Opus 4 — high-complexity reasoning
response_opus = client.messages.create(
    model="claude-opus-4-5",
    max_tokens=4096,
    messages=[{
        "role": "user",
        "content": "Design a distributed transaction system that maintains ACID guarantees under high concurrency..."
    }]
)
print(response_opus.content[0].text)

Setup via CodeGateway (TypeScript)

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
  apiKey: "your-codegateway-api-key",
  baseURL: "https://api.codegateway.dev/v1",
});

async function withSonnet(prompt: string): Promise<string> {
  const response = await client.messages.create({
    model: "claude-sonnet-4-6",
    max_tokens: 2048,
    messages: [{ role: "user", content: prompt }],
  });
  return response.content[0].type === "text" ? response.content[0].text : "";
}

// Streaming for long outputs
async function streamSonnet(prompt: string): Promise<void> {
  const stream = await client.messages.stream({
    model: "claude-sonnet-4-6",
    max_tokens: 8192,
    messages: [{ role: "user", content: prompt }],
  });

  for await (const chunk of stream) {
    if (
      chunk.type === "content_block_delta" &&
      chunk.delta.type === "text_delta"
    ) {
      process.stdout.write(chunk.delta.text);
    }
  }
}

Migrating from Older Versions

Migration from Sonnet 4.5 (or Claude 3 series) requires only a model ID change — the API contract is identical.

Key behavioral changes to test after migration:

• Sonnet 4.6 max output is 64K (vs. 8K in 4.5). If you cap max_tokens tightly for cost control, verify the cap still applies.
• Sonnet 4.6 responds to underspecified prompts more concisely — if output quality seems lower, add more detail to your prompt rather than switching models.

Cost Benchmark: 500 Code Reviews/Day

Scenario: 500 code review requests/day, average 2,000 input tokens + 500 output tokens each.

For routine code review, Sonnet 4.6 is the right call. Opus 4's cost is 5x — reserve it for tasks that actually need it.

CodeGateway applies the same flat 1.07× markup to every account; there is no tier ladder. Effective rates only move when upstream official prices change. See pricing tiers for the full schedule.

FAQ

Q: Is the quality difference between Sonnet 4.5 and 4.6 noticeable?

A: A: On multi-step coding tasks and complex reasoning, yes — Sonnet 4.6 is measurably better. For simple completions and text generation, the difference is minor. The main reason to migrate is the 64K output window.

Q: Does Opus 4 support Extended Thinking?

A: A: Yes, and it's currently the strong Claude model for Extended Thinking tasks. Extended Thinking works as expected through CodeGateway.

Q: What model IDs do I use with CodeGateway?

A: A: Standard Anthropic model IDs: claude-sonnet-4-6, claude-opus-4-5, claude-haiku-4-5. CodeGateway routes to the corresponding upstream models.

Q: Where do I get a CodeGateway API key?

A: A: Sign up at codegateway.dev, top up your balance, and create an API key in the dashboard. New accounts receive a starter credit after binding a card (current amount on the signup/pricing page).

Q: Does CodeGateway support both Sonnet 4.6 and Opus 4 simultaneously?

A: A: Yes — all current Anthropic models are available, including Haiku 4.5, Sonnet 4.5, Sonnet 4.6, and Opus 4. Switch between them by changing the model ID in your requests.

Related

• Claude Code Quickstart
• Claude API Rate Limits Explained
• Claude Code Sub-agents Tutorial
• CodeGateway Flat 1.07× Pricing
• Anthropic Models Documentation