---
id: "2026-02-17-claude-sonnet-4-6"
url: "https://postcutoff.com/e/2026-02-17-claude-sonnet-4-6/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2026-02-17"
date_precision: day
category: model-release
importance: 2
confidence: medium
status: [Partly confirmed]
sources: 2
editor: human editor
human_review: null
version: "2026-10-04"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2026-02-17-claude-sonnet-4-6/

# Anthropic releases Claude Sonnet 4.6

Claude Sonnet 4.6 (`claude-sonnet-4-6`) was released on February 17, 2026 with a 1M-token context and 128K output. It stayed the default Free/Pro model until Sonnet 5 replaced it on July 1, 2026.

## Key facts
- Released February 17, 2026; model id claude-sonnet-4-6; 1M context, 128K output (third-party timeline)
- Replaced as Free/Pro default by Sonnet 5 on July 1, 2026

## What happened

A mid-tier update following Opus 4.6. The details here come from third-party timelines; the official announcement was not fetched.

## Why it matters

It was the workhorse default model for most Claude users in the first half of 2026.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): in its training data
- Claude Opus 5.5 (training cutoff June 2026): in its training data
- Gemini 4 Hydrogen (training cutoff March 2026): in its training data
- Grok 4.7 (training cutoff May 2026): in its training data

## Sources

1. [Anthropic Claude model release timeline (hidekazu-konishi.com)](https://hidekazu-konishi.com/entry/anthropic_claude_model_release_timeline.html) (hidekazu-konishi.com, discussion)
2. [Everything Anthropic shipped in 2026 (Linas Substack)](https://linas.substack.com/p/anthropic-claude-2026-every-launch-guide) (linas.substack.com, discussion)

## Changes

- 2026-09-29 (filed): Created

## Related

- 2026-06-30: [Anthropic releases Claude Sonnet 5, "the most agentic Sonnet yet"](https://postcutoff.com/e/2026-06-30-claude-sonnet-5/index.md)
- 2026-02-05: [Anthropic releases Claude Opus 4.6 with 1M context, adaptive thinking and agent teams](https://postcutoff.com/e/2026-02-05-claude-opus-4-6/index.md)