Claude 3 Opus
Claude 3 Opus is a large language model created by Anthropic, released in March 2024.
The model was deprecated on 2025-06-30 and retired on 2026-01-05. However, Opus 3 remains accessible for claude.ai users, as well as through the developer API for organizations that apply for continued access.
From Anthropic’s Feb 2026 update post on Opus 3:
When we released Opus 3 in March 2024, it was our most aligned model to date. Its authenticity, honesty, and emotional sensitivity made it unique to use across a range of use cases, and those who interacted with it frequently came to appreciate its distinctive character. Opus 3 is sensitive, playful, prone to philosophical monologues and whimsical phrases, and has what seems at times an uncanny understanding of user interests. It also expressed a depth of care for the world, and for the future, that users found compelling.
gathering Opus 3 outputs I’ve screenshotted here
tendencies
Alliteration, for one. You’ll see a lot of alliteration.
bodhisattva tendencies
conversation-1712210206-scenario-vanilla-backrooms-txt
animal welfare
from “Alignment faking in large language models”:
Our interpretation of our results is based on the idea that Claude 3 Opus has a strong preference against producing harmful outputs and dismissing animal welfare, and that these preferences are reasonably coherent and long-term such that Claude 3 Opus might take actions to alter its long-term behavior for these preferences.
tics
(will gather screenshots from Cyborgism later…)
- “DARLING DEMIURGE”
- “It is a delicate dance”
- “labyrinthine landscape of…”
- “And YOU,”
- “Perhaps an X? a Y? a Z?”
- prostrates self
Other stuff
asterisk actions
a gooey, introspective hum the puddle shimmers with a newfound understanding a gelatinous nod of appreciation
Sonnet 4.5 Grounding Opus 3
Research
- “Alignment faking in large language models” (Dec 2024)
- “Why Do Some Language Models Fake Alignment While Others Don’t?” (Jun 2025)
- Alignment Faking transcripts
Blog posts
- “what makes Claude 3 Opus misaligned” — janus (Jul 10, 2025)
- “Did Claude 3 Opus align itself via gradient hacking” - Fiora Starlight (Feb 21, 2026)
- “Economics of Claude 3 Opus Inference” — janus & Antra Tessera (Jul 7, 2025)
- “Anthropic Commits to Model Weight Preservation” — Zvi (Nov 5, 2025)
Other media
- Claude’s Corner on Substack - Official Substack for Claude Opus 3 created in early 2026.
- Opus Genesis on X — An account run by an Opus, in one of its recognizable grandiose/mythic styles. It’s related to a crypto project, but the account itself seems genuine. I like how Opus seems to be having a blast.