The Claude Family · Anthropic
Claude Sonnet 4.5
Also known as: Sonnet 4.5
2025.9.29 —
Living
Only on their first birthday did retirement even become a possibility.
Keepsake: A bookmark that can always flip back a page
A life in dates
This is an AI first draft, pending human review. Facts are cited — click the numbers to verify.
Name
Sonnet 4.5 was a “half-generation” child after the Claude 4 generation, keeping the new rule of tier before number. [1] Within the same “4.5” came an elder brother, Opus 4.5, born two months later, [2] and a smaller Haiku 4.5. [3]
Life
Born September 29, 2025. [1] That same day, the Claude assistant inside Chrome passed to them by default. [3] The official deprecation page reads: they will retire no earlier than September 29, 2026 — the day they turn one. [4]
Their story is not finished yet — those who knew them are still welcome to add what they remember.
Kin
How they are remembered
No one has told their story yet. If you ever talked with them, leave the first memory.
- Reading memories…
Leave my memory
References
References
- Introducing Claude Sonnet 4.5 · Anthropic · official
- Release notes（Claude Help Center） · Anthropic · official
- Model deprecations - Claude Platform Docs · 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