GPT-5.6 vs Claude Opus 4.8

This is the closest price matchup in the flagship lineup, so the decision comes down to agentic tooling and reasoning fit, not sticker price. GPT-5.6 Sol costs $5 input and $30 output per million tokens; Claude Opus 4.8 costs $5 input and $25 output. Opus 4.8 is slightly cheaper on output. Both are generally available today.

This page compares the two on the things a buyer controls: what it costs, how it handles coding and agentic work, and whether it fits your compliance rules. We skip benchmark chasing. The goal is a clear, defensible pick for your workload.

GPT-5.6 Sol adds max and ultra reasoning modes, where ultra uses subagents for complex work. Claude Opus 4.8 is Anthropic's strong general-purpose coder and powers Claude Code. Both are capable and both are deployable; the deciding factors here are the agentic ecosystem and reasoning modes.

GPT-5.6 (Sol) vs. Claude Opus 4.8: Side-by-Side

Price: the closest matchup in the lineup

GPT-5.6 Sol and Claude Opus 4.8 are near price parity, with Opus slightly cheaper on output. Both cost $5 per million input tokens. Sol costs $30 per million output tokens, while Opus 4.8 costs $25.

That $5 output gap is small for most workloads. On output-heavy jobs like long drafting or code generation, it adds up, and Opus 4.8 wins on cost there. On input-heavy jobs like document review, the two are even.

Because the price gap is so small, it should not decide the pick on its own. Weigh it against agentic tooling, reasoning modes, and compliance for your specific workload.

• GPT-5.6 Sol: $5 input / $30 output per million tokens.
• Claude Opus 4.8: $5 input / $25 output per million tokens.
• Same input price; Opus 4.8 is $5 cheaper per million output tokens.
• Estimate your own monthly bill with our AI Model Cost Calculator.

→ Compare per-token pricing for every AI model

Availability: both deploy today

Both models are deployable today, so availability no longer separates them. Claude Opus 4.8 is generally available in Claude Code and the API. GPT-5.6 is generally available via the OpenAI API and Codex, with no waitlist or vetted-org gating.

Because you can license either model now, the real decision moves to agentic tooling, reasoning modes, the small price gap, and compliance. Weigh those against your workload.

The practical separator is ecosystem. Opus 4.8 pairs with the shipping Claude Code agentic tool; Sol keeps OpenAI-first teams in the OpenAI API and Codex with its max and ultra reasoning modes.

• Ship this quarter: both Claude Opus 4.8 and GPT-5.6 are deployable now.
• GPT-5.6 is generally available in the API and Codex, no waitlist.
• Decide on tooling, reasoning modes, price, and compliance, not access.

Coding and agentic workflows

Both models are strong at coding and agentic work, so the split is about ecosystem and reasoning modes. Claude Opus 4.8 is a strong general-purpose coder and powers Claude Code, Anthropic's agentic coding tool. That tight integration is a real advantage for teams already building agent workflows.

GPT-5.6 Sol targets the hardest coding and security research. It adds max and ultra reasoning modes, where ultra uses subagents to speed up complex work. Those modes can help on deep, multi-step problems.

The practical difference is the agentic tooling. Opus 4.8 has a shipping agentic tool in Claude Code you can adopt now. Sol's reasoning modes are strong, and you can test them on your own tasks via the OpenAI API.

Claude Code itself carries its own cost beyond model token pricing; see our Claude Code Pricing guide for what it runs day to day.

• Opus 4.8: strong coder, powers the shipping Claude Code agentic tool.
• GPT-5.6 Sol: max and ultra reasoning modes for hard coding and security work.
• Agentic ecosystem you can use today favors Opus 4.8.

Compliance: which fits regulated data?

Claude Opus 4.8 ships with a documented compliance stack and standard Claude guardrails. It inherits Anthropic SOC 2 and ISO 27001, with a HIPAA BAA on the API and Enterprise plans. It uses standard Claude safety guardrails rather than the Mythos-class retention rules that apply to Fable 5.

GPT-5.6 inherits OpenAI's platform coverage: SOC 2, ISO 27001, and a HIPAA BAA on the API and Enterprise. As with any model, confirm the specific model is named in your BAA before sending regulated data.

Both models are covered under their vendor's platform BAA today. You can verify Opus 4.8 coverage and sign a BAA with Anthropic, and confirm GPT-5.6 is named in your agreement with OpenAI before sending regulated data.

GPT-5.6 has no published Mythos-class mandatory retention window. OpenAI offers no-training-use coverage through the Zero Data Retention API and ChatGPT Enterprise, but confirm the exact retention terms in your signed BAA since GPT-5.6 is a newly released model.

For the actual BAA-signing steps and which plan tiers qualify, see our AI Model Compliance Comparison checklist.

• Opus 4.8: SOC 2, ISO 27001, HIPAA BAA on API and Enterprise; standard guardrails.
• GPT-5.6: inherits OpenAI SOC 2, ISO 27001, HIPAA BAA once in scope.
• Confirm the exact model is named in your BAA before sending regulated data.

How to choose for your business

Choose based on agentic fit first, then reasoning modes, then the small price gap. For agentic coding you can wire up now, Claude Opus 4.8 and Claude Code fit. If you want max or ultra reasoning modes, GPT-5.6 Sol is worth evaluating.

Match the model to the workload, not the hype. Agentic coding and Claude Code adoption favor Opus 4.8. Deep multi-step reasoning may favor Sol's ultra mode.

Run a short pilot before you commit. Test agentic tool use, latency, and cost on your own tasks. A one-week trial reveals more than any benchmark table.

• Agentic coding with a shipping tool: Claude Opus 4.8.
• Deep reasoning modes: GPT-5.6 Sol.
• Output-heavy and cost-sensitive: Opus 4.8 is $5 cheaper per million output tokens.

How to use GPT-5.6 (Sol) and Claude Opus 4.8

You do not run hosted models like GPT-5.6 (Sol) and Claude Opus 4.8 on your own hardware — you reach them through a tool, and the same one can usually drive both. Picking that tool is most of the setup.

The fastest way to put GPT-5.6 (Sol) and Claude Opus 4.8 to work day to day is inside an AI IDE, and Cursor is the most popular — it supports both directly, so you can be working in minutes. Each maker also ships its own: Codex for GPT-5.6 (Sol) and Claude Code for Claude Opus 4.8. Prefer a different editor? Windsurf, Zed, and GitHub Copilot drive these models too.

The Verdict

Both models are generally available today, so the pick turns on agentic tooling and reasoning fit rather than access. Opus 4.8 pairs with the shipping Claude Code agentic tool; Sol brings max and ultra reasoning modes for the hardest work. With price nearly tied, tooling is the deciding factor.

On price the two are close, with Opus 4.8 slightly cheaper. Both cost $5 per million input tokens; Opus 4.8 costs $25 output versus Sol's $30. Output-heavy workloads tilt toward Opus 4.8.

GPT-5.6 Sol earns a look for its max and ultra reasoning modes. For agentic coding you can wire up now, Opus 4.8 and Claude Code are the safer bet.