GPT-6.1 vs Claude Opus 5.5: Price, Benchmarks, Which to Use
Updated 2026-10-06
Short answer: Claude Opus 5.5 scores higher on most shared benchmarks, while GPT-6.1 Sol costs half as much per token. Opus 5.5 (Anthropic, released September 22, 2026) is priced at $4 per million input tokens and $20 per million output tokens. GPT-6.1 Sol (OpenAI, released September 29, 2026) is $2 and $10. Both handle about a million tokens of input and up to 128K tokens of output. If quality on hard reasoning, agent and computer-use tasks matters most, start with Opus 5.5; if you run many coding-agent tasks and cost per task matters, test GPT-6.1 Sol first.
When people search "GPT 6.1", they almost always mean GPT-6.1 Sol, the GPT-6.1 model OpenAI launched at DevDay. For background on it, see what GPT-6.1 Sol is and how to use it.
GPT-6.1 Sol vs Claude Opus 5.5 at a glance
| GPT-6.1 Sol | Claude Opus 5.5 | |
|---|---|---|
| Maker | OpenAI | Anthropic |
| Released | September 29, 2026 | September 22, 2026 |
| API price (input / output per 1M tokens) | $2 / $10 | $4 / $20 |
| Cached input | $0.10 per 1M | See Anthropic's pricing page |
| Input context | 1,050,000 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Knowledge cutoff | April 30, 2026 | June 2026 |
| Tier in its family | Mid-high tier (below GPT-6 Astra) | Top tier (above Sonnet 5.5) |
Prices and limits are list figures reported at launch and by model trackers in early October 2026; check each vendor's pricing page before budgeting.
Benchmarks: who wins where
The two models are rarely tested on the same benchmarks yet, so treat any single number with care. What the public trackers show so far:
- Overall: the LLM Stats composite score puts Opus 5.5 ahead, 60.3 vs 52.0, and Artificial Analysis scores Opus 5.5 at 58 on its Intelligence Index, ahead of OpenAI's flagship GPT-6 Astra at 53. Opus also leads the reasoning, coding and agent indexes on LLM Stats.
- Shared benchmarks: of five benchmarks reported for both models, Opus 5.5 wins four – HealthBench, HealthBench Professional, OSWorld 2.0 (computer use) and Terminal-Bench Science.
- Where GPT-6.1 Sol wins: DeepSWE 1.1, a software-engineering benchmark, at 75.2% versus 74.2% for Opus 5.5 – essentially a tie.
- Vendor claims: OpenAI positions 6.1 Sol as close to its flagship GPT-6 Astra on coding at about a fifth of Astra's price.
Benchmarks use different harnesses and settings, and the vendors report many of them themselves. The reliable test is your own: run both on 20–50 real tasks and compare pass rate and total cost.
Price: what the 2x gap means per task
GPT-6.1 Sol is exactly half the per-token price of Opus 5.5, for both input and output. A worked example – a coding task that sends 200,000 input tokens and gets 20,000 back:
- GPT-6.1 Sol: 0.2 × $2 + 0.02 × $10 = $0.60
- Claude Opus 5.5: 0.2 × $4 + 0.02 × $20 = $1.20
Per-token price isn't the whole story. Reasoning tokens are billed as output, agents make many calls, and a model that fails and retries costs more in the end. If Opus solves a task in one pass that Sol needs three attempts for, Opus is cheaper for that task. Caching long, repeated context lowers both bills.
Which should you use?
Choose Claude Opus 5.5 if:
- You need the strongest results on hard reasoning, research or planning.
- Your agent operates a computer or terminal (Opus leads OSWorld 2.0 and Terminal-Bench Science).
- Mistakes are expensive – security review, production debugging, legal or medical drafting with expert review.
- You want a more recent knowledge cutoff (June 2026 vs April 2026).
Choose GPT-6.1 Sol if:
- You run coding agents at volume and cost per task decides – it's 2x cheaper per token and ties Opus on DeepSWE.
- You already work in OpenAI's Codex, where 6.1 Sol is the default model, or in ChatGPT Work.
- You need the slightly larger input window for very large codebases or document sets.
Use both: a common setup is to route most tasks to the cheaper model and escalate failures or the hardest tickets to the stronger one. If budget is the main constraint on the Anthropic side, Claude Sonnet 5.5 is the cheaper Claude option – see Opus vs Sonnet.
How to test GPT-6.1 vs Opus 5.5 yourself
- Pick real tasks – bugs from your tracker, documents you actually process – not toy prompts.
- Use the same prompt and tools for both; record pass/fail, tokens and wall-clock time.
- Compute cost per solved task, not per token.
- Check failure modes – which model invents APIs, skips tests or stops early.
- Re-test after updates – both vendors ship point releases often.
FAQ
Is GPT-6.1 better than Claude Opus 5.5?
Not overall on current public benchmarks: Opus 5.5 leads most shared results and composite scores. GPT-6.1 Sol matches it on the DeepSWE coding benchmark and costs half as much per token, so for high-volume coding it can be the better value.
Which is cheaper, GPT-6.1 Sol or Opus 5.5?
GPT-6.1 Sol: $2 input and $10 output per million tokens. Claude Opus 5.5: $4 and $20. Sol is 2x cheaper per token.
Which has the bigger context window?
They are close: GPT-6.1 Sol accepts about 1.05 million input tokens, Opus 5.5 about 1 million. Both can return up to 128,000 tokens in one response.
Which is better for coding?
It depends on the work. On DeepSWE 1.1 they are within one point (Sol 75.2%, Opus 74.2%). Opus leads terminal and computer-use agent benchmarks. Test both on your codebase; Sol's lower price makes it attractive for large volumes of routine tickets.
Is there a GPT-6.1 model other than Sol?
GPT-6.1 Sol is the GPT-6.1 model OpenAI launched at DevDay on September 29, 2026. OpenAI's other GPT-6 tiers are GPT-6 Astra (flagship) and GPT-6 Luna (fast and cheap).
Independent comparison; GeneratorNest is not affiliated with OpenAI or Anthropic. Benchmark figures are from public trackers (LLM Stats, Artificial Analysis) and vendor reports as of October 6, 2026.