---
title: Claude 3.5 vs Claude 4 — What Changed
description: "Moving from Claude 3.5 to the current Claude 4 line? What improved, updated model IDs, and how to switch on apiToken.sale with one base-URL change."
url: https://apitoken.sale/docs/learn/claude-3-5-vs-claude-4
language: en
---

# Claude 3.5 vs Claude 4: what changed

The current Claude line is a clear step up from 3.5 in reasoning and coding. Migrating is mostly a model-ID change — everything else stays the same.

## What improved

The Opus, Sonnet and Haiku 4-series models improve on 3.5 for agentic coding, long-context consistency and complex reasoning, while keeping the same Messages API.

## How to migrate

Swap the model ID to a current one — for example claude-opus-4-8, claude-sonnet-5 or claude-haiku-4-5 — and keep your existing request code. On apiToken.sale it is the same key and endpoint.

## Frequently asked questions

### Is Claude 4 much better than 3.5?

Yes, especially for coding, agents and long-context tasks, while using the same API format.

### Is migrating hard?

No — update the model ID (e.g. to claude-sonnet-5) and your existing Messages API code keeps working.

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