Claude Opus 5.5 vs Claude Fable 5.1

A reversal worth knowing about: Anthropic's newest reasoning model now costs less than half its writing specialist, where the deepest model used to be the dearest.

What the numbers say

• Claude Opus 5.5 is about 2.5x cheaper on output tokens (240 vs 600 credits per 1M).
• Both take the same 1M-token context window.
• Claude Opus 5.5 is the newer release (September 2026 vs September 2026).

Derived from the live registry Zeplik routes and bills against. Credits: 1 credit = $0.10, computed from the raw provider rate with a 1.20x margin.

Side by side

Try both on Zeplik

The honest answer to most model debates is to run your own prompt on both. Zeplik puts Claude Opus 5.5 and Claude Fable 5.1 in the same chat, so you can switch mid-conversation and compare answers on the work you actually do.

Frequently asked questions

What is the difference between Claude Opus 5.5 and Claude Fable 5.1?

Claude Opus 5.5 is about 2.5x cheaper on output tokens (240 vs 600 credits per 1M). Both take the same 1M-token context window. Claude Opus 5.5 is the newer release (September 2026 vs September 2026).

Is Claude Opus 5.5 or Claude Fable 5.1 cheaper?

Claude Opus 5.5 is cheaper: 240 credits per million output tokens against 600. 1 credit = $0.10, computed from the raw provider rate with a 1.20x margin.

Which has the larger context window, Claude Opus 5.5 or Claude Fable 5.1?

Neither: both take 1M tokens.

Can I use both Claude Opus 5.5 and Claude Fable 5.1 on Zeplik?

Yes. Zeplik is a multi-model chat, so both sit behind one account and you can switch between them mid-conversation to compare answers on your own prompt.

Do Claude Opus 5.5 and Claude Fable 5.1 need a paid plan?

Both need a paid plan (Plus or above). Usage is then billed in credits from your monthly allowance.

Related comparisons

• Claude Opus 5.5 vs Claude Opus 5The rare upgrade with nothing to weigh: Opus 5.5 is newer than Opus 5 and twenty percent cheaper on both input and output, at the same million-token window.
• GPT-6 Astra vs Claude Fable 5.1Two models priced identically at $10 in and $50 out, aimed at opposite ends of the work: Astra's long-horizon engineering against Fable's literary voice.
• Claude Opus 5.5 vs GPT-6 AstraAnthropic's and OpenAI's deep-reasoning flagships, eighteen days apart -- and Astra asks two and a half times Opus 5.5's price for a window only five percent larger.
• Claude Opus 5.5 vs GPT-6 SolBoth shipped on the same day at adjacent tiers: whether Opus 5.5's depth is worth double GPT-6 Sol's price when their context windows are within five percent of each other.
• Claude Opus 5.5 vs Claude Sonnet 5The current Anthropic tier decision: Opus 5.5 costs twice Sonnet 5 for an identical million-token window, so the question is entirely about depth per turn.
• Claude Opus 5.5 vs Grok 4.7The two newest flagships in the catalogue, a day apart: Opus 5.5 doubles Grok 4.7's context and asks roughly four times as much per output token.