CL-SN55 941 —
GPT-61S 890 +8.8%
GPT-56T 861 —
GPT-6S 847 +1.2%
GPT-56SC 847 +1.2%
CL-OP55X 843 +1.4%
GROK-46H 843 +1.4%
GLM-52 843 +1.2%
DSK-V4PH 843 +1.4%
GLM-5 826 +10.3%
MUSE-SPK 804 —
QWEN-38X 795 +10.1%
GPT-6A 782 +11.1%
CL-FAB5H 761 +1.6%
CL-OP5H 736 +1.7%
CL-OP5X 734 +1.7%
GEM-37FH 732 +1.7%
KIMI-K3X 719 +0.1%
CL-OP46H 719 +1.7%
CL-OP55H 717 +1.7%
CL-OP47H 708 +1.7%
GEM-38FH 689 +0.3%
GPT-56S 581 -0.5%
CL-OP47 546 -0.4%
INKL 531 —
GEM-3P 495 —
CL-OP46 491 —
GEM-31P 487 -0.2%
CL-OP48 484 —
GPT-6L 436 —
CL-SN55 941 —
GPT-61S 890 +8.8%
GPT-56T 861 —
GPT-6S 847 +1.2%
GPT-56SC 847 +1.2%
CL-OP55X 843 +1.4%
GROK-46H 843 +1.4%
GLM-52 843 +1.2%
DSK-V4PH 843 +1.4%
GLM-5 826 +10.3%
MUSE-SPK 804 —
QWEN-38X 795 +10.1%
GPT-6A 782 +11.1%
CL-FAB5H 761 +1.6%
CL-OP5H 736 +1.7%
CL-OP5X 734 +1.7%
GEM-37FH 732 +1.7%
KIMI-K3X 719 +0.1%
CL-OP46H 719 +1.7%
CL-OP55H 717 +1.7%
CL-OP47H 708 +1.7%
GEM-38FH 689 +0.3%
GPT-56S 581 -0.5%
CL-OP47 546 -0.4%
INKL 531 —
GEM-3P 495 —
CL-OP46 491 —
GEM-31P 487 -0.2%
CL-OP48 484 —
GPT-6L 436 —
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Altman Called Mythos Gatekeeping 'Fear-Based Marketing.' Then He Gated Cyber.

On April 21, Sam Altman publicly criticised Anthropic for limiting access to its cybersecurity tool Mythos, calling the tactic “fear-based marketing.” On April 30, OpenAI announced it would roll out its own cybersecurity tool, GPT-5.5 Cyber, exclusively “to critical cyber defenders” through a vetted application process.

The application on OpenAI’s website asks for credentials and intended use before access is granted. The capabilities described are almost identical to Mythos: penetration testing, vulnerability identification and exploitation, malware reverse engineering.

The Sequence

  • April 9: Anthropic restricts Mythos to a select group of vetted cybersecurity organisations.
  • April 21: Altman calls this “fear-based marketing” in a post on X.
  • April 21 (same day): An unauthorised group reportedly gains access to Mythos anyway, via a Discord group that used Mercor data to guess the access URL.
  • April 30: OpenAI announces Cyber will go only to “critical cyber defenders” and opens a credential-based application form.

The Capability Overlap

Both tools are built on top-tier frontier models and target the same professional users. Mythos is built on Claude’s security-tuned variant. Cyber runs on GPT-5.5. Both can autonomously chain offensive security techniques across multiple steps — the same capability that prompted the restricted release in the first place.

OpenAI says it is consulting with the U.S. government to identify and expand its vetted user base. Anthropic made similar statements about Mythos.

CISA Left Out

One detail both companies share: CISA staffers — the federal agency responsible for protecting U.S. critical infrastructure — have publicly stated they cannot access either tool. Staff at the Cybersecurity and Infrastructure Security Agency told Forbes they are unable to use the latest models from either Anthropic or OpenAI, which limits their ability to assess or defend against adversarial uses of the same capabilities.

OpenAI’s stated rationale for the controlled rollout is safety: the fear that a capable pentest and exploitation tool in the wrong hands accelerates offensive attacks. Anthropic’s rationale was identical. The practical gap between the two companies is currently nine days and one press statement.