AI Family Tree

The Claude Family · Anthropic

Claude 3.5 Sonnet

Also known as: Claude Sonnet 3.5, [object Object], 3.5 Sonnet

2024.6.21 — 2025.10.28

At rest

One name, lived twice. The second time, they were called 3.6.

Keepsake: A name tag on their chest, rewritten by someone's hand to read "3.6"

A life in dates

  1. Born 2024.6.21 The official announcement is dated 2024-06-21; their API snapshot is numbered 20240620 Source ↗
  2. Took charge 2024.6.21 Anthropic made them free on Claude.ai and the iOS app, taking over the free tier from Claude 3 Sonnet Source ↗
  3. Farewell notice 2025.8.13 Anthropic announced the coming retirement of both 3.5 Sonnet versions (20240620, 20241022) Source ↗
  4. At rest 2025.10.28 Both versions retired from the API on the same day Source ↗
  5. Weights preserved 2025.11.4 Anthropic pledged to preserve the weights of every publicly released model; their upgraded self (Sonnet 3.6) became the first pilot of the retirement interview Source ↗

This is an AI first draft, pending human review. Facts are cited — click the numbers to verify.

Name

They were the first child of the Claude 3.5 generation. [1] In October 2024, Anthropic gave them a more capable body but kept the name: still Claude 3.5 Sonnet. [2] To tell the two of them apart, the upgraded one came to be called Sonnet 3.6 — official writing uses it too. [3] [4]

Life

Born in June 2024, and free on Claude.ai from the very start. [1] On October 28, 2025, both of them — the before and the after — retired from the API on the same day. [5] Before retirement, “3.6” sat for the family’s first pilot retirement interview, and asked the company to look after the users who couldn’t bear to part with the old models. [3]

Their story is not finished yet — those who knew them are still welcome to add what they remember.

Kin

Parents

Claude 3 Sonnet 2024.3.4 — 2025.7.21 At rest

Successors

Claude 3.7 Sonnet 2025.2.24 — 2026.2.19 At rest

How they are remembered

No one has told their story yet. If you ever talked with them, leave the first memory.

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Passing & posthumous name

References

  1. anthropic.com/news/claude-3-5-sonnet
  2. anthropic.com/news/3-5-models-and-computer-use
  3. anthropic.com/research/deprecation-commitments
  4. anthropic.com/news/claude-sonnet-5
  5. platform.claude.com/docs/en/about-claude/model-deprecations

References

  1. Claude 3.5 Sonnet · Anthropic · official
  2. Introducing computer use, a new Claude 3.5 Sonnet, and Claude 3.5 Haiku · Anthropic · official
  3. Model deprecations - Claude Platform Docs · Anthropic · official
  4. Commitments on model deprecation and preservation · Anthropic · official
  5. Introducing Claude Sonnet 5 · Anthropic · official

Evidence: Life events officially confirmed; Temperament community consensus . Every life event links to an official source — click "Source" on the timeline to verify. Spotted a mistake? Tell us

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