Claude Opus 5.5 vs GPT-6 Astra: price, access and limits compared

The short answer: it depends on token budget and which app you use

Choose Claude Opus 5.5 if API cost per token matters, since it lists $4 input and $20 output per million tokens, or if you want it in chat on a $20 plan. Choose GPT-6 Astra if you already work in ChatGPT Work or Codex, where Plus includes it. Astra lists $10 and $50 per million tokens, so a like-for-like workload costs more unless it uses fewer tokens.

Scope and evidence

Task: hard coding, research and agent work for one person or a small team, in the vendors' apps and APIs. Prices are in US dollars from Anthropic's Opus 5.5 overview and Claude pricing page and from OpenAI's GPT-6 Astra model page, ChatGPT pricing page and help center, checked on October 27, 2026.

No prompts were run for this comparison; it relies on Anthropic's and OpenAI's own documentation. Both vendors publish their own benchmarks; independent head-to-head results are not established here.

Compare the same criteria

Each criterion gives both models side by side from the vendors' own pages, then what the difference means in practice.

• Intended use. Opus 5.5: long-running agentic coding and knowledge work. Astra: OpenAI's most capable model, for complex reasoning, coding, computer use, research and document creation. What this means: both target demanding work.
• API price per million tokens. Opus 5.5: $4 input, $20 output, $0.20 cache read. Astra: $10 input, $50 output, $1 cached input, with 2x input and 1.5x output above 272K input tokens. What this means: Astra's list price is 2.5 times higher.
• Context and output. Opus 5.5: 1M tokens, 128K output. Astra: 1.05M tokens, 128K output. What this means: practically equal.
• Knowledge cutoff. Opus 5.5: June 2026. Astra: April 30, 2026. What this means: Opus has more recent built-in knowledge.
• Reasoning control. Opus 5.5: adaptive thinking always on, effort from low up to max, default medium. Astra: effort low, medium, high, xhigh and max; OpenAI's pages checked do not state a default. What this means: both reach max and neither can switch reasoning off.
• App access. Opus 5.5: Claude Pro and Max, not Free. Astra: Plus in Work and Codex only; GPT-6 Pro in Chat on Pro $100, Pro $200, Business and Enterprise. What this means: entry-level chat access to Opus is cheaper.
• Inputs. Both: text and images in, text out. What this means: no difference for screenshots or diagrams.

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Which fits your real work?

A large API batch of code reviews. Opus 5.5 fits on list price, at $4/$20 against $10/$50, both with 50% off in batch; measure tokens per task on both before deciding.

A Plus subscriber who codes in Codex. Astra fits because it is already included there, with OpenAI estimating 5 to 45 local messages per five-hour window.

A researcher who wants the hardest model in a chat window on a $20 plan. Opus 5.5 fits, since GPT-6 Pro in Chat starts at Pro $100.

Cost of getting the work done

API, per million tokens: Opus 5.5 is $4 input and $20 output; Astra is $10 input and $50 output. A job with 2 million input and 200,000 output tokens costs $12 on Opus and $30 on Astra before caching or batch discounts.

Apps, per month: Claude Pro is $20 billed monthly and includes Opus; ChatGPT Plus is $20 a month and includes Astra in Work and Codex, while ChatGPT Pro starts at $100 a month for GPT-6 Pro in Chat. Both vendors describe usage limits rather than fixed counts.

Try both on the same small task

A hands-on check you can run yourself: hand Opus 5.5 and Astra one research and writing job built on a fixed set of sources, set both to medium effort, and verify every line of what comes back.

• Every quote appears word for word on the cited page.
• Disagreements listed are real when you compare the quotes.
• Nothing comes from outside the three PDFs.
• Multiply the reported tokens by each list price to compare cost; treat a single attempt as a first impression and repeat it before drawing conclusions.

Decision checklist

Use the conditions that apply to you. Details are in our Claude Opus 5.5 profile and our GPT-6 Astra profile.

• If API list price drives the choice, start with Opus 5.5.
• If you already pay for ChatGPT Plus and code in Codex, try Astra there first.
• If you want the model in a chat window for $20 a month, Opus 5.5 is on Claude Pro.
• If you need the most recent built-in knowledge, Opus 5.5 lists June 2026.
• If you need prompts above 272K tokens on Astra, budget for the higher long-context rates.

Go a little further

Related reading

• Claude Opus 5.5 profile →
• GPT-6 Astra profile →