Claude Opus 5.5 users say reverse-engineering prompts now get cut off

Users of Claude Opus 5.5 say Anthropic’s flagship model now cuts itself off when asked to reverse-engineer software, the same skill many credit for the recent flood of AI-assisted game decompilations and recompilations. The complaints surfaced on r/Claude on 21 October, and Kotaku reports that Anthropic hasn’t announced or released a new version of Opus 5.5. Nothing has been confirmed, so for now this is a pattern of user reports rather than a documented change.

What users are describing

In the Reddit thread, users say Claude begins researching a target normally, then stops partway through. According to Kotaku, several users report that reverse-engineering prompts “trigger a safety guardrail mid sentence.” In one example, Claude told the user a safety check had stopped its response and that it couldn’t produce the write-up again, even reworded.

Not everyone agrees something changed. One commenter argued that reverse-engineering requests were always hit-and-miss because the classifier is “twitchy”, and Kotaku says the doubters are in the overwhelming minority. A post on X describing the same behaviour carries its own caveat: a refusal doesn’t necessarily mean the model has been deliberately made less capable. The same post also cites another account saying that some users are seeing performance shifts in Opus 5.5, though Anthropic hasn’t confirmed anything official.

Why this model is under the microscope

Opus 5.5 is the centrepiece of the recent decompilation craze. Many have attributed the wave of vibe-coded decompilations and recompilations of games to the model, which Anthropic released on 22 September. In a Kotaku interview published on 15 October, the outlet tied browser ports, mash-up mods, Switch-to-PC ports and recent PlayStation jailbreaking advances back to the release. It also reported that GitHub’s DMCA logs are filling up with takedown notices from publishers. One example is a 7 October request from Mega Crit, which says a repository held unreleased Slay the Spire II source code.

Publishers aren’t the only ones taking notice. In that interview, Dr Luke Dicken, Take-Two’s former head of AI, called the decompile-and-port trend something developers and publishers need to take seriously. He expects it to push the industry towards more invasive DRM and streaming. Kotaku also notes that Xbox CEO Asha Sharma addressed the browser ports in an Xbox Wire post.

What Anthropic has said about safeguards

Anthropic’s Opus 5.5 launch post says the model ships with the safeguards it developed for its most capable systems. Because Opus 5.5 is comparable to Claude Mythos 5.1 in biology and cybersecurity, it deploys with safeguards similar to those on Claude Fable 5.1. The company added that it will expand its Cyber Verification Program in the coming weeks so verified security practitioners can use the model. The post’s benchmark footnotes also say that when those safeguards intervened in testing, cybersecurity tasks were completed by the older Claude Opus 4.8. Reverse engineering overlaps with security research, one of the areas those safeguards cover, but the launch post says nothing specific about game decompilation.

The same post pitched Opus 5.5 against OpenAI’s GPT-6 Astra on coding benchmarks, so the model’s coding strength is central to how Anthropic sells it. Meanwhile, Claude keeps spreading into everyday tools, including Google Docs, Sheets and Slides. That makes how consistently its guardrails behave a practical concern for ordinary users, not just game hackers.

The speculation about why

Kotaku’s writer offers a guess at the motive, which is his own and not Anthropic’s. He says users on X linked the supposed change to people modding Samsung TVs’ “always-on” microphones through Claude. He doubts that was the trigger, and suggests the browser-based game ports and the open-sourcing of programs such as Adobe and Microsoft Office may have weighed more. The outlet also argues that Anthropic has a record of changing Claude’s behaviour without announcing it, which is why it thinks a quiet tweak is plausible. Anthropic hasn’t commented on any of this.

If your workflow depends on Opus 5.5 handling binary analysis or software teardown, we recommend treating the behaviour as unconfirmed but real enough to plan around. Keep a fallback, and check Anthropic’s release notes and support pages for any change to its safeguards.