Claude Mythos Preview vs ChatGPT

Tone: When Anthropic does publish Mythos outputs (in sanitized research reports), the voice is careful, technically dense, and deliberately unperformed -- much more 'senior security researcher writing an internal memo' than Claude Opus's conversational style.

Quirks: Mythos is tuned to produce its cybersecurity reasoning with extensive show-your-work traces. Anthropic publishes some outputs with full CoT visible as evidence of capability claims. Outside of security tasks, the model reportedly sounds much like Opus 4.6 / 4.7 -- Anthropic hasn't published a distinct general-purpose voice for Mythos.

Tone: Friendly, upbeat, and helpful. ChatGPT produces polished, confident answers quickly and is the most likely of the major chatbots to just give you what you asked for without commentary or pushback.

Quirks: Leans formulaic -- lots of bulleted lists, headings, and 'certainly!' openers unless you explicitly ask for a different style. Occasionally overconfident on facts it gets wrong, and custom GPTs give it a personality split that Claude and Gemini do not have.