Anthropic releases system cards for Claude Fable 5 and Claude Mythos 5

Anthropic has published system cards for its Claude Fable 5 and Claude Mythos 5 large‑language models, giving engineers a single source for architecture, training data, and performance numbers [Anthropic PDF].

Details

The cards list each model’s parameter count, training‑data cutoff, and context window size. They also provide benchmark results on standard suites such as MMLU, GSM‑8K, and HumanEval, along with latency and throughput figures on typical hardware configurations. Safety mitigations, recommended prompting patterns, and known failure modes are spelled out, allowing product teams to assess risk and compliance before integration [Anthropic PDF].

Why it matters

Having the specs in a structured, publicly available format removes guesswork from model selection, speeds up integration testing, and lets developers compare Anthropic’s offerings against competing LLMs on equal footing. The transparency also gives auditors concrete data to verify that the models meet internal governance standards [Anthropic PDF].