Two weeks apart, the two biggest labs drew opposite battle lines. GPT-6 Astra is OpenAI’s most capable, and most expensive, model ever, the first it calls “AGI era.” Claude Opus 5.5 answered with near-equal capability at roughly 40% less cost, and a claim to beat Astra on agentic coding. So which should you actually pay for?
The 20-second answer
- Absolute peak capability, cost no object: GPT-6 Astra.
- Best value, and better for agents: Claude Opus 5.5.
- For most real work, especially agents → Opus 5.5.
Side by side
| GPT-6 Astra | Claude Opus 5.5 | |
|---|---|---|
| Maker | OpenAI | Anthropic |
| Input / output (per 1M) | $10 / $50 | $4 / $20 |
| Cached input | $1 | $0.20 |
| Context window | 1.05M | 1M (class) |
| Peak reasoning | Saturates FrontierMath / ARC-AGI | Fable-5.1 level |
| Agentic coding (Terminal-Bench 4.0) | 57.9%* | 66.4% |
| Best for | Hardest reasoning / research | Agents, coding, everyday value |
*Astra’s Terminal-Bench figure as cited by Anthropic. Vendor benchmarks favour the vendor, treat as directional, and pricing changes fast.
GPT-6 Astra, the capability ceiling
Astrais the most capable model available, full stop. It effectively saturates the hardest public reasoning benchmarks, 97.6% on FrontierMath Tier 4, 99.9% on ARC-AGI-3, and sets a new bar on computer-and-browser use (72.6% on OSWorld 2.0). If your problem is genuinely at the edge of what models can do, frontier research, the hardest math and reasoning, it’s the one to reach for. The catch is price: at $10 / $50 per million tokens it’s the most expensive model OpenAI has ever sold, and only heavy caching makes it affordable at scale.
Claude Opus 5.5, the value frontier
Opus 5.5 takes the opposite bet: not the highest ceiling, but the best capability per dollar. Anthropic says it performs at its Fable 5.1 flagship’s level on most work while costing ~40% less to run than Opus 5 and generating output 30% faster. Crucially, on Terminal-Bench 4.0, long, multi-step coding-agent work, it posts 66.4%, ahead of Astra’s cited 57.9%. For anyone running coding agents (in Claude Code or elsewhere), higher agentic accuracy at a quarter of Astra’s output price is decisive.
How to decide
- Frontier research / the hardest reasoning → GPT-6 Astra.
- Coding agents and long autonomous work → Opus 5.5.
- High token volume where cost matters → Opus 5.5.
- You want the single most capable model, budget aside → GPT-6 Astra.
- Everyday production work → Opus 5.5 (and keep a cheaper tier for the easy stuff).
The bottom line
This is the clearest the two labs’ strategies have ever been: OpenAI sells the ceiling at a premium; Anthropic sells near-equal capability at a discount and wins on agents. Unless your work genuinely lives at the frontier of reasoning, Opus 5.5 is the smarter default, cheaper, faster, and better where most of the money is actually spent. See the full field on our best AI models ranking and the which AI model should you use guide.
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Tests AI tools against real work and writes the verdicts on ConsistencyAI. No paid placements.