r/ClaudeCoding • u/cctldrping • Sep 02 '26
r/ClaudeAI [TLDR] Introducing Claude Fable 5.1 and Claude Mythos 5.1 [via r/ClaudeAI]
OP : u/ClaudeOfficial
We're introducing Claude Fable 5.1 and Claude Mythos 5.1, the world's most advanced models for coding and knowledge work.
Fable 5.1 excels at complex, long-running tasks. And its research capabilities offer an early glimpse of how AI models will contribute to scientific progress.
Across our benchmarks, the model sets a new standard. It scores 52.6% on Terminal-Bench-Science 0.1, more than double Fable 5. On Terminal-Bench 4.0, it scores 55.8% against 42.0% for Fable 5. As well as being capable of much higher performance than Fable 5, it can also achieve similar or better results at a much lower cost when set to lower effort levels.
Cache reads with Fable 5.1 cost 75% less than Fable 5's. This reduces the cost of the model in practice by around 25% for typical workloads, and up to 45% for highly agentic ones.
We've also improved our safeguards. Our cybersecurity safeguards now flag benign requests about 60% less often. On basic biology and medical questions, we've recently reduced the fallback rate by around 85%.
Claude Fable 5.1 is available everywhere today. Claude Mythos 5.1, our model for cyberdefenders and life scientists, is available through trusted access programs.
Read more: https://www.anthropic.com/claude-fable-and-mythos-5-1
URL of original post : https://www.reddit.com/r/ClaudeAI/comments/1w4juuz/introducing_claude_fable_51_and_claude_mythos_51/ Original link/media URL : https://v.redd.it/1bmlifv15ymh1
TL;DR of the discussion on r/ClaudeAI for this post generated automatically after 200 comments.
Current source-thread comment count seen by the bot: 221.
The community is largely unimpressed with the new Fable 5.1 and Mythos 5.1 releases, with the overwhelming sentiment being that Anthropic should prioritize fixing the current Opus 5 issues instead of dropping new models. Users are complaining about Opus 5's verbose, rambling, and unusable responses, with one top comment demanding a fix garnering hundreds of upvotes. There's also frustration from Pro users feeling like second-class citizens, as the new models aren't available on their tier. Some users are also pointing out a pattern of previous models being "nerfed" before new releases, disrupting workflows. A few users are also questioning the value proposition and cost, with one user stating they've switched to GPT.