Claude Opus 5.5 vs GPT-6.1 Sol
Specs and prices below are quoted from official vendor documentation (Anthropic, OpenAI), checked on 2026-10-16. Prices are the vendors’ list prices, not byesu’s; on byesu you are billed per token and see the actual price in the model list after you sign in.
At a Glance
| Item | Claude Opus 5.5 | GPT-6.1 Sol |
|---|---|---|
| Vendor | Anthropic | OpenAI |
| Official positioning | Long-running agentic coding and knowledge work; Anthropic’s recommended starting point | “Near-Astra performance for complex work at a lower cost” |
| Model ID on byesu | claude-opus-5-5 | gpt-6.1-sol |
| Context window | 1M | 1.05M |
| Max output | 128K | 128K |
| Knowledge cutoff | Jun 2026 | Apr 30, 2026 |
| Reasoning control | Adaptive thinking, always on; default effort medium | low / medium (default) / high / xhigh / max |
| Official list price (input / output per 1M tokens) | $4 / $20 | $2 / $10 |
| Official cached-input price (per 1M) | $0.20 | $0.10 |
| Official cost of 1M input + 200K output | $8 | $4 |
Key Differences
- Price: at list price GPT-6.1 Sol costs half as much per token as Claude Opus 5.5 ($2/$10 vs $4/$20). Cached input is $0.10 vs $0.20 per million.
- Context: both take about a million tokens (1M for Opus 5.5, 1.05M for GPT-6.1 Sol, whose max input is 922K) and both return up to 128K tokens per request.
- Reasoning control: Opus 5.5 always thinks adaptively and you steer it with
effort(defaultmedium); GPT-6.1 Sol usesreasoning.effortfromlowup tomax(defaultmedium). - API surface: GPT-6.1 Sol supports tool calling only on the Responses API; Chat Completions works without tools. Opus 5.5 is native to the Anthropic Messages API, and byesu also serves it through the OpenAI-compatible endpoint.
- Knowledge: Opus 5.5’s reliable knowledge cutoff is June 2026; GPT-6.1 Sol’s is April 30, 2026.
Which One Should You Pick?
- Long agentic coding sessions, especially in Claude Code: start with Opus 5.5 — that is the workload Anthropic positions it for.
- Cost-sensitive or high-volume work with tools, or Codex: GPT-6.1 Sol — half the list price, and Codex uses the Responses API it is built around.
- Not sure: run the same 20–50 real tasks through both (see below) and compare quality, latency and the charges in your console.
Use Both With One Key
Both models are on byesu with the default auto-group token. To compare them on your own workload, keep the base URL and token and change only the model ID:
from openai import OpenAI
client = OpenAI(api_key="sk-YOUR_TOKEN", base_url="https://byesu.com/v1")
for model in ["claude-opus-5-5", "gpt-6.1-sol"]:
resp = client.chat.completions.create(
model=model,
messages=[{"role": "user", "content": "Summarize this repository’s architecture"}],
)
print(model, resp.usage, resp.choices[0].message.content[:200])FAQ
Is GPT-6.1 Sol cheaper than Claude Opus 5.5?
Yes, at list price. GPT-6.1 Sol is $2 per million input tokens and $10 per million output tokens; Claude Opus 5.5 is $4 and $20. On byesu both are billed per token, and the actual price is shown in the model list after you sign in.
Which has the bigger context window?
They are close: Claude Opus 5.5 has a 1M-token context window and GPT-6.1 Sol 1.05M (922K max input). Both return up to 128K output tokens per request.
Can I call both with one API key?
Yes. With a byesu token in the default auto group, call either model through https://byesu.com/v1 and change only the model ID (claude-opus-5-5 or gpt-6.1-sol).