Flagship is a company-relative label, distinct from frontier model, which is an industry-relative claim about being near the overall capability leading edge. A company's flagship (e.g. Claude Mythos 5 for Anthropic, GPT-5.6 Sol for OpenAI) is usually also positioned as frontier, but the terms answer different questions: 'is this the best we make' versus 'is this near the best anyone has made.'