Opus 5.5 vs Astra
Claude Opus 5.5 vs GPT-6 Astra
Overview
Opus 5.5 is Anthropic’s current Opus ($4 / $20, 1M context). GPT-6 Astra is OpenAI’s most capable GPT-6 SKU ($10 / $50 standard; 2×/1.5× if input exceeds 272K). Same output sticker as Fable 5.1, 2.5× Opus on tokens. Pick by ecosystem (Claude vs ChatGPT/Codex/API) and whether the task needs Astra’s top tier.
Standard API (per million tokens)
| Opus 5.5 | GPT-6 Astra | |
|---|---|---|
| Input / output | $4 / $20 | $10 / $50 |
| Cached input | $0.20 | $1.00 |
| Vendor | Anthropic | OpenAI |
| Long prompt surcharge | See Anthropic card | >272K in: 2× in/cache, 1.5× out |
| Batch | 50% off | 50% off (Batch/Flex) |
Capabilities
- Opus 5.5Claude agents, prompt cache at 5% of input, Fast mode (premium) on first-party API where offered.
- GPT-6 AstraOpenAI’s highest GPT-6 for hard reasoning, coding, computer use, and docs. Effort levels include xhigh and max.
- CostAstra list is Fable-class money. If you only need “better than Sonnet,” Opus 5.5 or GPT-6 Sol ($2 / $10) is usually enough.
Context Window
Opus 5.5: 1M class on Anthropic’s card. Astra: watch the 272K input threshold—crossing it reprices the whole request.
- Keep Astra prompts under 272K unless you intend to pay long-context rates.
- Opus: still trim; $4 / MTok × a bloated repo is real money.
Pricing
List prices from Anthropic and OpenAI. Tool calls (search, computer use) may add fees on OpenAI.
- Opus 5.5
- $4 / $20 · cache write 5m $5 · 1h $8
- GPT-6 Astra (short)
- $10 / $50 · cached in $1 · cache write $12.50
- Astra long context
- $20 / $75 in-out class when input >272K
- OpenAI Fast mode is 2×. Batch/Flex 50% off.
- Do not compare invoices 1:1—tokenizers and tool fees differ.
How to Use
- Stay in one stackClaude Code / Anthropic API → Opus; ChatGPT / Codex / OpenAI API → Astra (or Sol first).
- Try Sol or Sonnet firstBoth vendors’ $2 / $10 mid-tier covers most coding.
- Escalate onceOne flagship pass, then return to the cheap SKU.