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Head-to-head comparison

Claude Opus 5.5 vs GPT-6 Astra

Claude Opus 5.5 (Anthropic) and GPT-6 Astra (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 6 November 2026

As of 6 November 2026, Claude Opus 5.5 holds the stronger ModelCap Index position (#1 vs #13); and Claude Opus 5.5 is 2.5× cheaper per output token ($20.00/1M vs $50.00/1M).

Which should you choose?

Choose Claude Opus 5.5 if…

  • you want the stronger overall ModelCap Index position — #1 against #13 (87.7 vs 80.6 points).
  • API cost matters — $20.00/1M output tokens against $50.00/1M, about 2.5× cheaper.
  • your workload is prompt-heavy — input tokens cost $4.00/1M against $10.00/1M.
  • you want provider choice — 5 listed API providers against 3.
  • Arena text is your yardstick — 1509 against 1476.
  • Arena coding is your yardstick — 1551 against 1542.
  • LMArena Agent is your yardstick — 20.1% against 14.7%.
  • AA Intelligence Index is your yardstick — 59.1 against 56.9.
  • Terminal-Bench 4.0 is your yardstick — 64.9% against 58.2%.
  • you want the more recently listed model — Claude Opus 5.5 was listed 22 September 2026, GPT-6 Astra 4 September 2026.

Choose GPT-6 Astra if…

  • ARC-AGI-2 is your yardstick — 95.0% against 93.3%.

Claude Opus 5.5 vs GPT-6 Astra: specs, pricing and context

Specification comparison of Claude Opus 5.5 and GPT-6 Astra
FieldClaude Opus 5.5AnthropicGPT-6 AstraOpenAI
ModelCap Index position#1#13
Index score87.780.6
EvidenceMeasuredMeasured
Input price / 1M tokens$4.00$10.00
Output price / 1M tokens$20.00$50.00
Context window1M tokens1M tokens
Declared route output cap128K128K
API providers listed53
Weight accessNo linked weightsNo linked weights
Input modalitiesText, Image, FileFile, Image, Text
First listed22 September 20264 September 2026
PublisherAnthropicOpenAI

Evidence: 4 public benchmark observations across 4 boards · 5 public benchmark observations across 5 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Opus 5.5 vs GPT-6 Astra

Public benchmark boards where Claude Opus 5.5 or GPT-6 Astra has a published result
BoardClaude Opus 5.5GPT-6 AstraLeads
Arena textArena (LMArena)15091502–1515High14761470–1482MaxClaude Opus 5.5
Arena codingArena (LMArena)15511538–1563High15421532–1553MaxClaude Opus 5.5
LMArena AgentLMArena20.1%18.1%–22.2%Max14.7%12.6%–16.8%MaxClaude Opus 5.5
ARC-AGI-2ARC Prize Foundation93.3%High95.0%MaxGPT-6 Astra
ARC-AGI-3ARC Prize Foundation—62.7%MaxOnly one result
AA Intelligence IndexArtificial Analysis59.1Max56.9MaxClaude Opus 5.5
Terminal-Bench 4.0Terminal-Bench (Laude Institute)64.9%61.7%–68.0%Claude Code · Max58.2%55.4%–61.0%Codex · MaxClaude Opus 5.5

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Opus 5.5 vs GPT-6 Astra: common questions

Is Claude Opus 5.5 better than GPT-6 Astra?

Claude Opus 5.5 ranks higher on the ModelCap Index as of 6 November 2026: #1 against #13. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is Claude Opus 5.5 cheaper than GPT-6 Astra?

Claude Opus 5.5 is cheaper on output tokens: $20.00/1M against $50.00/1M. Input tokens are $4.00/1M for Claude Opus 5.5 and $10.00/1M for GPT-6 Astra. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $18.00 for Claude Opus 5.5 versus $45.00 for GPT-6 Astra. Claude Opus 5.5 costs 60.0% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

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

Both publish a 1M-token context window. OpenRouter catalogue or provider-endpoint declaration. Limits can vary by provider and prompt length; a model-wide maximum has not been independently verified.

Which is better for coding, Claude Opus 5.5 or GPT-6 Astra?

Arena coding: Claude Opus 5.5 1551, GPT-6 Astra 1542 — Claude Opus 5.5 leads. Terminal-Bench 4.0: Claude Opus 5.5 64.9%, GPT-6 Astra 58.2% — Claude Opus 5.5 leads.

Are Claude Opus 5.5 and GPT-6 Astra open-weight models?

Claude Opus 5.5: No linked weights. GPT-6 Astra: No linked weights. Open weights mean the checkpoint can be downloaded and self-hosted under its licence. A missing weight link does not identify every API or chat product that offers a model.

Where can I run Claude Opus 5.5 and GPT-6 Astra?

ModelCap currently lists 5 API providers for Claude Opus 5.5 and 3 for GPT-6 Astra, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Opus 5.5 vs GPT-6 Astra comparison?

Every figure and ModelCap Index position comes from the same published snapshot dated 6 November 2026. Publication and page updates happen separately; use the snapshot date shown on the page.

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