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Claude Opus 5.5 vs GPT-6.1 Sol: Which Model Fits You?
Claude Opus 5.5 is Anthropic's main frontier model, released September 22, 2026, and its recommended default for most work. GPT-6.1 Sol is OpenAI's mid-tier model, released September 29, 2026, aiming for near-Astra results at a lower price. Both take text and images and output text, with about 1M tokens of context.
The short answer
Pick Claude Opus 5.5 if you want Anthropic's default model for long agentic coding and knowledge work, with access in the Claude apps. Pick GPT-6.1 Sol if token cost matters most, since its API prices are half of Opus 5.5's, and you work in the Responses API or Codex.
Side by sideClaude Opus 5.5 vs GPT-6.1 Sol
| Claude Opus 5.5 | GPT-6.1 Sol | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Released | Sep 22, 2026 | Sep 29, 2026 |
| Context window | 1M | 1.05M |
| API price | $4 / input MTok, $20 / output MTok | $2 / 1M input tokens, $0.10 / 1M cached input tokens, $10 / 1M output tokens |
| Open weights | No | No |
| Consumer access | Claude Pro, Max, Team and Enterprise; not on Free | ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu at launch (not initially in the standard Chat mode) |
| Best for | Long-running agentic coding and knowledge work; Anthropic's recommended default for most workloads. | Complex coding, computer use and professional tasks you want near-Astra quality on at about one-fifth of Astra's token price. |
Facts in this table come from the verified profile of each product.
Key differences
$4 / input MTok, $20 / output MTok.
$2 / 1M input tokens, $0.10 / 1M cached input, $10 / 1M output tokens.
1M tokens, 128K max output.
1.05M tokens (922K max input, 128K max output).
Anthropic's main frontier model; about Fable 5.1 level on most tasks at under half its token price.
OpenAI's mid-tier model; OpenAI says it nearly matches GPT-6 Astra on agentic coding and computer use.
Terminal-Bench 4.0 66.4%, OSWorld 2.1 (partial) 81.8%, HLE with tools 67.7% (Anthropic-reported).
DeepSWE v1.1 75.2%, OSWorld 2.0 offline 71.4%, AutomationBench 31.7% (OpenAI-reported).
Claude Pro, Max, Team and Enterprise; not on Free.
ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu at launch.
Fast mode (up to 2.5x speed) in Claude Code and the Claude Platform.
Ultrafast tier since 2026-10-08 in API, Codex and ChatGPT Work.
Thinking cannot be turned off; most cybersecurity tasks are rerouted to Opus 4.8.
Tool calling needs the Responses API; no 'none' or 'minimal' reasoning effort.
Choose Claude Opus 5.5 if…
- You want Anthropic's recommended default for long agentic coding work.
- You use Claude apps on Pro, Max, Team or Enterprise.
- You want fast mode inside Claude Code.
- Terminal-Bench and GDPval-AA results matter to your use case.
Choose GPT-6.1 Sol if…
- You want lower token prices and $0.10 cached input.
- You build on the Responses API or Codex.
- You need the larger 922K input limit.
- You want near-Astra coding results at a lower cost.
Frequently asked questions
Which is cheaper, Claude Opus 5.5 or GPT-6.1 Sol?
GPT-6.1 Sol costs $2 per 1M input tokens and $10 per 1M output tokens, with cached input at $0.10. Claude Opus 5.5 costs $4 per input MTok and $20 per output MTok.
Can their benchmark scores be compared directly?
Not directly. Both sets are vendor-reported and mostly use different tests or versions, such as OSWorld 2.1 (partial) for Opus 5.5 and OSWorld 2.0 offline for GPT-6.1 Sol. Treat them as signals, not a head-to-head ranking.
Where can I use each model without the API?
Claude Opus 5.5 is available on Claude Pro, Max, Team and Enterprise, not on Free. GPT-6.1 Sol launched in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu, not initially in standard Chat mode.
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