# What Claude Sonnet 4.5 introduced

> Anthropic emphasized coding and agent work, alongside changes to Claude Code and the API.

Source: https://fullbytedeveloper.com/blog/claude-sonnet-four-five-launch
Originally posted: 2025-10-01
Published here: 2026-11-06

Anthropic introduced Claude Sonnet 4.5 on 2025-09-29 with a focus on coding, computer use and extended agent tasks. The release also included Claude Code checkpoints and API features for context editing and memory. [1]

## Separate the model from the tools around it

A model's reasoning capability, a coding interface's rollback controls and an application's memory system are different parts of a workflow. The announcement discussed all of them, so a claim about the overall experience should identify which part changed. [1]

Anthropic's benchmark results were reported evaluations under particular conditions. They did not guarantee that every repository or long-running task would improve.

When comparing models, use the same task and acceptance criteria. Review the patch, run the project's relevant checks and count the corrections required. For work involving external systems, define the permissions and stopping conditions before allowing an agent to continue unattended.

## Sources

1. [Anthropic Sonnet 4.5 announcement](https://www.anthropic.com/news/claude-sonnet-4-5)

## Original posts

- [Instagram post](https://www.instagram.com/fullbytedeveloper/p/DPRmZMIjNuq/)