Collection
Anthropic released Claude Fable 5.1 and invite-only Mythos 5.1
Anthropic released Claude Fable 5.1 (generally available) and Claude Mythos 5.1 (invite-only trusted access for vetted cybersecurity and life-sciences work). Anthropic says they are the same model with different safeguards. Matthew Berman's capability rankings are his recap, not independently verified.
Share this article
Fable 5.1 scored 52.6 percent on Terminal-Bench-Science, up from 24.7 percent on Fable 5
Read sourceAnthropic's launch video and official table put Terminal-Bench-Science 0.1 at 52.6 percent for Fable 5.1 versus 24.7 percent for Fable 5. Terminal-Bench 4.0 is 55.8 percent on Fable and 60.9 percent on Mythos. CursorBench 3.2.0 is 73.4 percent.
The headline discount is API token billing, not a cheaper max-effort task
Read sourceBetter Stack flagged that Artificial Analysis found Fable 5.1 on max effort more expensive per task than Fable 5. The 75 percent cache-read cut is the API story. Cognition is moving Devin traffic to Fable 5.1 on launch day, per Anthropic's partner quotes.
Anthropic released Claude Fable 5.1 and invite-only Mythos 5.1
Read sourceMatthew Berman recaps Anthropic's September 1, 2026 drop of Claude Fable 5.1 and Claude Mythos 5.1. Anthropic says they are the same model with different safeguards: Fable 5.1 is generally available, and Mythos 5.1 is limited to trusted-access programs for vetted cybersecurity and life-sciences work. Berman's title and capability rankings are his, not a lab scoreboard this desk verified.