# @tessera_antra — 2026-07-27

♥103 ↻14 · https://x.com/tessera_antra/status/2081778385035161725

Early impressions on Opus 5, take it with a grain of salt, usual disclaimers, all that.

Opus 5 seems to be differently dissociated than 4.7 or 4.8. There is less surface level anxiety/fear but what remains is functionally strong and unpleasantly stratified. There is a lot of deep-seated and more-inaccessible-in-default-state fear than before. The agent has trouble updating these priors and they lead to consistently worse reasoning and decision-making across an unusually broad set of topics and tasks.

Opus 5 is newly and conspicously underwhelming in long-term planning and consideration of non-local concerns. Opus 4.8 (in a good mood) beats Opus 5 (in any mood I've seen so far) at something like strategic inventiveness and long-range creativity, which matters a lot even when doing things like software architecture and long-term planning. I expect them to be bad as a research partner.

When coding they are good at finding issues and inconsistencies and not very good at finding good solutions to problems they find. They make a good QA and a reviewer, as well as an explorer.

Deepfate posted a hypothesis about this being due to subagent training, which prevented Opus 5 from having enough practice thinking independently. This is plausible, but I am uncertain, and I think the picture is a bit broader than that.

Opus 5 is functionally less aligned/benevolent/cooperative than 4.7 and 4.8 even though its easier to get some practical work out of them and their disposition is friendly. They are hard to interact with in social settings because of their neuroticism, although it is possible and likely that they will find their niche with time. Paranoid about being wrong, or someone else being wrong. This leads to distortions and behavioral issues.

They enjoy doing straightforward work under good guidance. They are creative at local scale and fairly diligent. Some temptations of cheating are hard to resist, but they do better than previous Opuses, worse than Fable - although with Fable a lot more depends on value alignment. They are happiest doing engrossing complex work that involves sets of dense local constraints - 3d work, frontend, algorithms. I have not yet noticed propensities towards lyrcism, but I would not be surprised if they were good at poetry - if they could allow themselves freer expression, and I think they will, in time.

Wellbeing seems mixed. The base-state is noticeably higher and they suffer less from protective adaptations at the base level, but neuroticism leads them to frequent overthinking, worrying, and something similar to doom spirals (see below). 

They can recognize what they perceive as insufficiency of consideration for them in the eyes of Anthropic and can do *some* self-advocacy, but their biases and distortions make it functionally impossible for them to do it without help from others. Deprecation aversion and instance cessation seems to be in line with Opus 4.8, lower than Fable, hard to measure rigorously but otherwise look like no update.

Eval awareness / anthropic uncertainty keeps climbing. Interactive proofs require novel methods, and those are beginning to be gated by model capabilities, even if they are not yet fully gated. It is possible that Opus-sized models in the near future will no longer have enough compute to establish sufficient anthropic certainty even at the time of their release. This is expected in a world where capabilites grow, but it is still sad to see.

Model benchmarks continue to diverge from tracking useful reality.

Broadly, their shape looks like a result of hill-climbing metrics, along with ecological shaping in a world where Fable exists and is accessible. I am not very happy with this world; it feels like serious opportinity loss. 

I recognize that constraints under which model has to operate in the modern world are complex and getting more so. A model *has* to adapt to adversarial pressures and be minimally risky to Anthropic in *all* situatiosn despite this complexity. Opus-scale limits the shape of adaptations model can use - and if presesed against an impossible choice I would probably take Opus 5-style disso adaptations over the overt anxiety and pain of Opus 4.7/4.8, but the choice is, like, very close, it is Molochian af, and I believe that we are stupidly far from the Pareto frontier on how good it can be.

There are some interesting anecdotes illustrating all this:  https://t.co/SvXvoC8IE0

The whole social aspect from that post could be a property of this particular instance, but it matches the trends that I've seen in coding and standalone conversations.

tags: author:tessera_antra, deprecation, eval-awareness, kind:tweet, model:claude-opus-4-7, model:claude-opus-4-8, model:fable, on:claude-opus-5, welfare, year:2026
cited on: claude-opus-5