Anthropic's Claude model for demanding reasoning and long-horizon agentic work, released as the successor to Fable 5.1. It costs less than 5.1 on input, output and cache, at the same context window; Anthropic points most workloads to the cheaper Opus 5.5.
pick it if
Opus 5.5 at higher effort still falls short on your evals
you run Fable 5.1 today and want lower rates on the same window
you run long agent sessions; cache hits bill at 2.5% of input
skip it if
Opus 5.5 covers your workload at half the per-token price
your code forces tool use, prefills replies, sets temperature or edits earlier turns; all return errors
Anthropic's Opus-tier Claude model, built for long-running agentic coding and knowledge work. it replaced Opus 5 at a lower $4 / $20 rate with the same 1M-token context, and sits between Sonnet 5.5 and Fable 5.1.
pick it if
you want Opus-tier Claude at 20% below Opus 5's per-token rates
you resend long prompts; cache hits bill at 5% of input
you run long agentic coding sessions across a 1M-token window
skip it if
Sonnet 5.5 at half the per-token price covers your workload
your code forces tool use or turns thinking off; both are unsupported
faq
which is better, Claude Fable 5.2 or Claude Opus 5.5?
on Humanity's Last Exam (with tools), as each maker reports it, Claude Fable 5.2 scores 74.2% and Claude Opus 5.5 67.7%. these are each maker's own numbers, not a controlled head-to-head; the spec table lists every benchmark both publish.
which is cheaper, Claude Fable 5.2 or Claude Opus 5.5?
Claude Opus 5.5 lists lower input and output prices. on a coding-agent session (2M tokens in, 60,000 out) Claude Fable 5.2 costs $18.40 and Claude Opus 5.5 $9.20.
can i switch between Claude Fable 5.2 and Claude Opus 5.5 mid-task?
yes. in an octomind session, /model octohub:claude-fable-5-2 and /model octohub:claude-opus-5-5 switch models without losing the conversation, so you can draft on one and review on the other.
try either model
switch between models inside the same octomind session.