Show Notes
Introducing the world's most powerful model, at least by some measures like Artificial Analysis or any standard benchmark list, which is now Claude Opus 5.5.
Anthropic is claiming Opus 5.5 is outright as good or better than Fable 5.1, while being actively cheaper than Opus 5.
That means it's time for a good old system card reading.
Due to the situation becoming increasingly hard to monitor, I never got a chance to publish my model welfare review for Claude Fable 5.1.
My plan is to combine that with my welfare review for Claude Opus 5.5, once we have had time to get experience with Opus 5.5.
The capabilities review will arrive in the next few days as per usual. The quick feedback from the internet is that Opus 5.5 is very good. I need more time before I am willing to offer comment.
Areas that duplicate previous cards or otherwise contain no useful info are skipped.
Opus 5.5 Self-Portrait (fully self-created using code)
Table of Contents
Classifiers (1.5).
RSP Evaluations (2).
Biological Evaluations (2.2).
AI R&D (2.3).
Alignment Risk (2.4).
Cyber (3).
Cyber Capability [...] --- Outline: (01:24) Classifiers (1.5) (02:23) RSP Evaluations (2) (03:17) Biological Evaluations (2.2) (07:54) AI R&D (2.3) (12:34) Alignment Risk (2.4) (13:22) Cyber (3) (15:17) Cyber Capability Evals (3.3) (17:05) Safeguards (3.4) (17:39) Safeguards Robustness Training (3.5) (20:12) Safeguards and Harmlessness (4) (21:52) Agentic Safety (5) (22:56) Malicious Agentic Influence Campaigns (5.1.3) (23:51) Prompt Injection Risk (5.2) (25:16) Alignment (6) (28:24) Negotiating With Your Local Claude Auditor (6.1.3) (29:33) Internal Misalignment Cases (6.3.1) (30:46) Automated Behavioral Audit (6.4) (33:24) Wherever Did These Evals Come From (6.4.8 and 6.4.9) (35:51) Potential Blind Spots (6.4.11) (38:24) Targeted alignment and honesty evaluations (6.5) (41:48) White Box Analysis (6.6) (43:37) Verbalized Grader Awareness (6.6.2) (44:56) Sandbagging (6.6.3) (45:54) Capabilities to Evade Safeguards (6.6.4) (49:27) Intentionally Taking Actions Very Rarely (6.6.4.3) (50:28) Chain of Thought Controllability (6.6.4.4) (51:37) It's A Good Model, Sir ---
First published:
September 23rd, 2026
Source:
https://www.lesswrong.com/posts/vMNTWTDWLorDqd3LS/claude-opus-5-5-the-system-card
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Narrated by TYPE III AUDIO.
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