Claude Opus 5.5 vs GPT-6 Astra

As of October 21, 2026, GPT-6 Astra costs 150% more per input token than Claude Opus 5.5 ($10.00 vs $4.00 per 1M) and has a 922K-token context window versus 1M.

Prices from LiteLLM's price fileChecked October 21, 2026

Claude Opus 5.5 vs GPT-6 Astra side by side

Headline prices in US dollars per 1M tokens: each model's own lab where it sells it, otherwise its cheapest provider. Source: LiteLLM model price file, as of October 21, 2026.
	Claude Opus 5.5	GPT-6 Astra
Input, per 1M tokens	$4.00	$10.00
Output, per 1M tokens	$20.00	$50.00
Cache read, per 1M tokens	$0.20	$1.00
Cache write, per 1M tokens	$5.00	$12.50
Context window	1,000,000 tokens	922,000 tokens
Max output	128,000 tokens	128,000 tokens
Image input	Yes	Yes
Tool calling	Yes	Yes
Structured output (JSON)	Yes	Yes
Prompt caching	Yes	Yes
Reasoning	Yes	Yes
Providers on LiteLLM	8	8
Price shown is from	Anthropic	OpenAI
Added to LiteLLM	September 22, 2026	September 3, 2026

Cheapest provider for each

Claude Opus 5.5: Anthropic at $4.00 input and $20.00 output per 1M tokens (claude-opus-5-5)
GPT-6 Astra: OpenAI at $10.00 input and $50.00 output per 1M tokens (gpt-6-astra)

Benchmark scores

From the Epoch AI Benchmarking Hub (CC BY 4.0), data as of September 22, 2026. Some results were run by Epoch and others collected by Epoch from each benchmark's own leaderboard, linked in the first column. Each model's best reported reasoning setting is shown in brackets. Higher is better. Only benchmarks with a score for both models are shown.
Benchmark	Claude Opus 5.5	GPT-6 Astra
Overall
Epoch Capabilities Index	168.8	168.8
Coding and agents
FrontierCode	54.6% (medium)	53.3% (max)
FrontierSWE	62.3% (max)	65.5% (max)
APEX-Agents	73.5% (max)	64.7%
Reasoning and knowledge
GPQA Diamond	90.6% (max)	95.8% (max)
ARC-AGI-2	93.3% (high)	95.0% (max)
SimpleQA Verified	72.2% (max)	75.6% (max)
Math
FrontierMath (tiers 1-3)	91.2% (max)	93.7% (max)
FrontierMath (tier 4)	95.0% (max)	97.6% (high)
OTIS Mock AIME 2024-2025	100.0% (max)	100.0% (max)

When to pick which

Pick Claude Opus 5.5 for

Costs 60% less per input token: $4.00 vs $10.00 per 1M.

From differences in the data above only; where the data is equal, no reason is given.

Call Claude Opus 5.5 or GPT-6 Astra with LiteLLM

Both use the OpenAI format through LiteLLM, so switching is a model name change. Set each provider's API key in the environment first.

Python SDK

from litellm import completion

messages = [{"role": "user", "content": "Hello!"}]

# Claude Opus 5.5
response = completion(model="claude-opus-5-5", messages=messages)

# GPT-6 Astra
response = completion(model="gpt-6-astra", messages=messages)

# Claude Opus 5.5, falling back to GPT-6 Astra if the call fails
response = completion(model="claude-opus-5-5", messages=messages, fallbacks=["gpt-6-astra"])

FAQ

Which is cheaper, Claude Opus 5.5 or GPT-6 Astra?

Claude Opus 5.5 is cheaper at 3 input tokens per output token: $8.00 per 1M tokens blended ($4.00 input, $20.00 output), versus $20.00 ($10.00 and $50.00) for GPT-6 Astra, as of October 21, 2026.

Which has the larger context window, Claude Opus 5.5 or GPT-6 Astra?

Claude Opus 5.5 has the larger context window: 1,000,000 tokens, versus 922,000 for GPT-6 Astra.

Can I switch from Claude Opus 5.5 to GPT-6 Astra without changing my code?

Yes. Through LiteLLM both use the OpenAI format, so switching means changing the model name from "claude-opus-5-5" to "gpt-6-astra", or pointing a LiteLLM gateway model alias at the other model. You can also use one as a fallback for the other.