Searches for "Opus 5.5 vs GPT-6" usually mean one of two matchups. Opus 5.5 against GPT-6 Sol is flagship against workhorse: Sol lists at half Opus’s price. Opus 5.5 against GPT-6 Astra is the closer contest on capability, with Astra listing at two and a half times Opus. Each lab publishes its own benchmark suite, so like-for-like numbers are scarce; treat any single leaderboard as a starting point.
All figures are the vendors’ published list prices and specs; the apimodels.app row is what we charge today, billed per token with failed calls free.
| Claude Opus 5.5 | GPT-6 Sol | GPT-6 Astra | |
|---|---|---|---|
| Vendor list, input / output per 1M | $4 / $20 | $2 / $10 | $10 / $50 |
| apimodels.app, input / output | $2.40 / $12 | $1.00 / $5.00 | $2.40 / $12 |
| Context / max output | 1M / 128K | 1.05M / 128K | — |
| Reasoning control | effort low–max, default medium, cannot disable | reasoning_effort none–max, default medium | reasoning_effort |
| Released | 22 Sep 2026 | 22 Sep 2026 | — |
On Anthropic’s published agentic-coding suite Opus 5.5 posts 66.4% on Terminal-Bench 4.0 and 57.8% on CursorBench 4.0; OpenAI publishes a different set for GPT-6, so there is no clean head-to-head from the labs themselves. Independent aggregators disagree on both quality ranking and cost per task, largely because Opus 5.5 always thinks while Sol can run with reasoning off.
A practical rule: for high-volume calls where speed and cost dominate, start with GPT-6 Sol with low reasoning effort. For long agentic coding sessions, review and careful writing, start with Opus 5.5. For the hardest problems where you would otherwise pay for Fable 5.1, compare Opus 5.5 at high effort with GPT-6 Astra. On apimodels.app switching is one string, so measure on twenty of your own prompts rather than trusting a leaderboard.
OpenAI released GPT-6.1 Sol on 29 September 2026 (API id gpt-6.1-sol) at $2 input / $10 output per million tokens, cached input $0.10 — the same list price as GPT-6 Sol. OpenAI claims it nearly matches GPT-6 Astra on agentic coding at about a fifth of the cost and scores 2.2 points above Opus 5.5 on AutomationBench. There is no GPT-6.1 Astra: a planned October launch was cancelled, so searches for "GPT-6.1 Astra" have no model behind them yet.
GPT-6.1 Sol is not on apimodels.app yet; GPT-6 Sol ($1 / $5) and GPT-6 Astra ($2.40 / $12) are. If you are choosing today between Opus 5.5 and OpenAI’s mid tier, the comparison above still applies, with GPT-6.1 Sol as the stronger version of Sol at the same list price.
cURL
curl https://api.apimodels.app/v1/messages \
-H "x-api-key: $APIMODELS_API_KEY" \
-H "anthropic-version: 2023-06-01" \
-H "Content-Type: application/json" \
-d '{
"model": "claude-opus-5-5",
"max_tokens": 16000,
"messages": [{"role": "user", "content": "Review this function for race conditions: ..."}]
}'Python
from openai import OpenAI
client = OpenAI(base_url="https://api.apimodels.app/v1", api_key="YOUR_APIMODELS_KEY")
# Same prompt, two models, one key: compare them on your own task before you commit.
for model in ["claude-opus-5-5", "gpt-6-sol"]:
r = client.chat.completions.create(
model=model,
messages=[{"role": "user", "content": "Refactor this module and explain the risky parts: ..."}],
)
print(model, r.usage.prompt_tokens, r.usage.completion_tokens)
print(r.choices[0].message.content[:400])It depends on which GPT-6 and which task. Against GPT-6 Sol, Opus 5.5 is the higher tier at twice the list price and is generally stronger on agentic coding and judgment-heavy work; Sol is cheaper and faster for volume. Against GPT-6 Astra the capability gap is smaller and Astra lists at 2.5x Opus. The labs publish different benchmark suites, so test on your own prompts.
GPT-6 Sol: $2 / $10 list against $4 / $20. On apimodels.app it is $1 / $5 against $2.40 / $12. Sol can also run with reasoning off, while Opus 5.5 always thinks, which widens the gap on short tasks.
No. OpenAI released only GPT-6.1 Sol on 29 September 2026 ($2 / $10 per million tokens); the planned October GPT-6.1 Astra launch was cancelled. GPT-6 Astra ($10 / $50 list) remains OpenAI’s top model.
Yes. On apimodels.app Opus 5.5, GPT-6 Sol and GPT-6 Astra are all available on one key through the OpenAI-compatible /v1/chat/completions; Opus 5.5 is also on the native /v1/messages. Change the model string to switch.
