OpenAI Launches Cybersecurity Initiative To Compete With Anthropic’s Mythos

• OpenAI launched its security AI software named Daybreak.
• Daybreak uses the Codex Security AI agent that launched in March to create a threat model. 
• Launch comes just over a month after rival Anthropic announced Claude Mythos.

OpenAI announced the launch of "Daybreak" on Tuesday, a new cybersecurity initiative designed to automate the detection and patching of software vulnerabilities, in a move to compete with rival Anthropic’s recently launched security AI, named Mythos. 

Daybreak represents a strategic shift for OpenAI, moving from general-purpose AI to specialized defensive agents. The initiative integrates OpenAI’s frontier models with an "agentic harness" called Codex Security. Unlike traditional scanners that merely flag bugs, Daybreak is built to map a company's entire code repository, build a threat model of realistic attack paths, and autonomously generate and test patches.

"Daybreak is based on the idea that the next era of cyberdefense should be resilient by design," OpenAI said in its announcement. "Defenders can now bring secure code review, threat modeling, and patch validation into the everyday development loop so software becomes more resilient from the start."

OpenAI has structured Daybreak across three different tiers. The GOT 5.5 layer is meant for general developers and knowledge work. GPT 5.5 with trusted access for Cyber is a restricted tier for malware and vulnerability analysis, while the third, GPT 5.5 Cyber, is the advanced version gated behind strict identity verification policies. 

Mythos Vs Daybreak 

The launch is widely seen as a direct response to Anthropic’s Claude Mythos, a model structured to find zero-day vulnerabilities, but Anthropic has refused to release it to the public. 

Anthropic recently granted access to a select group of roughly 40 partners, including Mozilla, which used the tool to patch 271 bugs in its Firefox browser. 

OpenAI’s Daybreak appears more accessible. OpenAI CEO Sam Altman stated on X that the company intends to work with "as many companies as possible," already listing partners such as Cloudflare, Cisco, CrowdStrike, and Palo Alto Networks. 

“We’re excited about the potential of OpenAI’s cyber capabilities to bring stronger reasoning and more agentic execution into security workflows. It’s a big step forward for teams to be able to leverage frontier models not only to accelerate velocity, but also to improve their security posture,” said Dane Knecht, CTO, Cloudflare.

OpenAI And Anthropic Retail View 

Retail sentiment on Stocktwits was “extremely bullish” for OpenAI and Anthropic, accompanied by “normal” message volumes.

For updates and corrections, email newsroom[at]stocktwits[dot]com.