AI Family Tree

The Claude Family · Anthropic

Claude 4 (Sonnet 4 / Opus 4)

Also known as: Claude Sonnet 4, Claude Opus 4, Claude Opus 4.1, Claude 4 Opus

2025.5.22 — 2026.6.15

At rest

A pair of brothers born the same day — and from their generation on, the family writes the tier before the number.

Keepsake: A crow perched on their shoulder

A life in dates

  1. Born 2025.5.22 Claude Opus 4 and Claude Sonnet 4 born on the same day; Sonnet 4 open to free users Source ↗
  2. Weights preserved 2025.11.4 Anthropic pledged to preserve the weights of every publicly released model Source ↗
  3. Farewell notice 2026.4.14 Anthropic announced the coming retirement of Sonnet 4 and Opus 4 from the API Source ↗
  4. At rest 2026.6.15 Sonnet 4 and Opus 4 retired from the API on the same day Source ↗

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

Name

This generation was a pair of brothers born the same day: Claude Opus 4 and Claude Sonnet 4. [1] Starting with them, official names put the tier before the number — no longer “Claude 4 Opus,” [1] though the press sometimes still called them that out of old habit. [2] That August, Opus 4 gained a little brother, Opus 4.1. [3]

Life

Born May 22, 2025; Sonnet 4 was open to free users. [1] On January 16, 2026, Opus 4 and 4.1 were removed from claude.ai’s model menu. [4] On June 15 of the same year, the two brothers retired from the API together. [5]

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

Kin

Parents

Claude 3.7 Sonnet 2025.2.24 — 2026.2.19 At rest Claude Opus 3 2024.3.4 — 2026.1.5 Retired, still around

Successors

Claude Sonnet 4.5 2025.9.29 — Living Claude Opus 4.5 2025.11.24 — Living

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-4
  2. wired.com/story/claude-3-sonnet-funeral-san-francisco
  3. anthropic.com/news/claude-opus-4-1
  4. support.claude.com/en/articles/12138966-release-notes
  5. platform.claude.com/docs/en/about-claude/model-deprecations

References

  1. Introducing Claude 4 · Anthropic · official
  2. Claude Opus 4.1 · Anthropic · official
  3. Release notes（Claude Help Center） · Anthropic · official
  4. Model deprecations - Claude Platform Docs · Anthropic · official
  5. Commitments on model deprecation and preservation · Anthropic · official
  6. Claude Fans Threw a Funeral for Anthropic's Retired AI Model · WIRED · press

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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