Claude Opus 5.5 vs GPT-6 Astra

Anthropic'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.

What the numbers say

• Claude Opus 5.5 is about 2.5x cheaper on output tokens (240 vs 600 credits per 1M).
• 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 GPT-6 Astra 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 GPT-6 Astra?

Claude Opus 5.5 is about 2.5x cheaper on output tokens (240 vs 600 credits per 1M). Claude Opus 5.5 is the newer release (September 2026 vs September 2026).

Is Claude Opus 5.5 or GPT-6 Astra 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 GPT-6 Astra?

GPT-6 Astra, at 1.1M tokens against 1M.

Can I use both Claude Opus 5.5 and GPT-6 Astra 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 GPT-6 Astra 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 Sol vs GPT-6 AstraThe upgrade decision inside the GPT-6 line: Astra costs five times Sol for the same 1,050,000-token window, so the question is which work is hard enough to need it.
• 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.
• GPT-6 Astra vs GPT-5.6 SolThe upgrade decision almost every OpenAI user is actually making: GPT-6 Astra costs five times Sol per token for the same 1,050,000-token window, so the question is which work is hard enough to need it.
• 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.
• GPT-6 Astra vs Claude Opus 5The new top-tier head-to-head: OpenAI's GPT-6 flagship against Anthropic's deepest model, which asks half the price for a comparable million-token window.