Claude Opus 5.5 from Anthropic and GPT-6 Sol from OpenAI both went live on GetVibe API on September 23, 2026. Both are flagship models that people put behind coding agents. This comparison uses only what our catalog publishes for each model. There are no benchmark scores here, because we have not measured any. Test both on your own repository before you choose.
Spec sheet
| Claude Opus 5.5 | GPT-6 Sol | |
|---|---|---|
| Maker | Anthropic | OpenAI |
| Model ID | claude-opus-5.5 | gpt-6-sol |
| Context window | 1,000,000 tokens | 272,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Input | text and images | text and images |
| Reasoning control | extended thinking with a token budget | reasoning_effort from minimal to max |
| Tool calling | yes | yes |
| JSON mode | yes | yes |
Anthropic Messages format (/v1/messages) | yes | no |
| Price | $0.2027 input · $1.0134 output per 1M tokens | $0.1096 input · $0.548 output per 1M tokens |
Prices are pulled live from the catalog, so they are current whenever you read this. In both models, reasoning tokens are billed as output.
Context: the biggest practical difference
Claude Opus 5.5 accepts a 1,000,000-token window. We tested it before we published it: a 732,379-token request was answered with details from both ends of the prompt. GPT-6 Sol has a 272,000-token window. For an agent, the window sets how much code, tool output and history fit before the tool has to summarize or drop context. If your agent regularly loads large parts of a monorepo, that difference matters more than any other line in the table.
Reasoning: two different controls
GPT-6 Sol takes the OpenAI reasoning_effort parameter with six levels: minimal, low, medium, high, xhigh, max. You can set a low level for simple edits and raise it for hard debugging on the same model.
Claude Opus 5.5 uses Anthropic's extended thinking: a thinking object with budget_tokens, sent to /v1/messages. Do not treat the chat reasoning_effort field as the same thing for Claude. Our article reasoning_effort explained covers both controls.
Which agents each one plugs into
- Claude Code and other Anthropic-format tools: Claude Opus 5.5 works directly. GPT-6 Sol does not, because it is not served in the Messages format. Setup: Claude Code with a custom endpoint.
- Codex CLI: it uses the Responses API. See the Codex CLI setup.
- OpenAI-compatible tools (Cline, Cursor, Roo Code, Aider and others): both models work through
/v1/chat/completionswith the same key. See the integrations list.
How to decide
- Pick Claude Opus 5.5 when the agent needs very long context, or when your tool speaks only the Anthropic format.
- Pick GPT-6 Sol when 272K is enough and you want to tune reasoning per request with a single parameter.
- Compare the live prices above against your own token mix. Agents are input-heavy, and both models publish a cached-input price on their model pages. Our prompt caching guide shows how to use it.
A cheap way to settle it: run the same task list through both models via the same endpoint, then compare the pass rate and the spend in your dashboard. Only the model string changes.
curl https://getvibeapi.com/v1/chat/completions \
-H "Authorization: Bearer $GETVIBE_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model": "gpt-6-sol", "reasoning_effort": "high",
"messages": [{"role": "user", "content": "Find the bug in this function: ..."}]}'Next steps
Open the model pages for Claude Opus 5.5 and GPT-6 Sol, read about the rest of the GPT-6 family and the Opus 5.5 1M context, or browse everything on the Models page.