GPT-5.6 vs Claude Sonnet 5

Claude Sonnet 5 is the cheaper of the two flagships here, at $2 input and $10 output per million tokens through August 2026, moving to $3 and $15 on September 1, 2026. GPT-5.6 Sol costs $5 input and $30 output per million tokens. Both are generally available now, so the real decision is price versus reasoning depth.

Anthropic released Claude Sonnet 5 on June 30, 2026, positioning it for frontier performance across coding, agents, and professional work at scale — Anthropic's mid-tier model built to handle enterprise-level, multi-agent workloads at a lower price than Opus-class models.

GPT-5.6 Sol targets the hardest coding and security work, adding max and ultra reasoning modes where ultra uses subagents for complex, multi-step problems. This page compares cost, access, agentic fit, and compliance so you can pick with confidence.

GPT-5.6 (Sol) vs. Claude Sonnet 5: Side-by-Side

Price: Sonnet 5 is the budget flagship

Claude Sonnet 5 is meaningfully cheaper than GPT-5.6 Sol at current intro pricing. Sonnet 5 costs $2 per million input tokens and $10 per million output tokens through August 2026. GPT-5.6 Sol costs $5 input and $30 output (OpenAI) — more than double on input and triple on output.

Anthropic's intro pricing is temporary: Sonnet 5 moves to $3 input and $15 output per million tokens on September 1, 2026. Even at that higher rate, it stays cheaper than Sol on both sides.

For teams that don't need Sol's deepest reasoning modes, Sonnet 5 is the more cost-efficient flagship-class option today, especially at high token volume.

• GPT-5.6 Sol: $5 input / $30 output per million tokens.
• Claude Sonnet 5: $2 / $10 through Aug 2026, then $3 / $15 from Sep 1, 2026.
• Sonnet 5 also caches input at $0.20 per million tokens.

→ Compare per-token pricing for every AI model

Best-fit work: reasoning depth vs multi-agent scale

GPT-5.6 Sol is built for the hardest individual problems. It adds max and ultra reasoning modes, with ultra using subagents to work through complex, multi-step tasks.

Claude Sonnet 5 is built differently: Anthropic positions it for frontier performance across coding, agents, and professional work at scale — tuned for enterprise-level, multi-agent workloads rather than single-thread depth.

If your workload is one hard problem at a time, Sol's reasoning modes are worth the premium. If it's many parallel agents doing production work, Sonnet 5's scale-oriented design and lower price are the better fit.

• Sol: deepest reasoning on single hard problems, with subagent-powered ultra mode.
• Sonnet 5: tuned for multi-agent, enterprise-scale professional work.

GPT-5.6 vs Claude Sonnet 5 benchmarks: what's actually published

Neither GPT-5.6's nor Claude Sonnet 5's maker has published a same-day, apples-to-apples benchmark suite pitting these two exact versions against each other, so treat any comparison here as directional rather than a verified head-to-head.

Vendors have not published a directly comparable, head-to-head SWE-bench Verified score for these exact current-generation versions as of this writing. The most recent published reference points are Claude Opus 4.8 at about 88.6%, GPT-5 at about 74%, Grok 4 at about 75%, and Gemini 2.5 Pro at about 71% (Google) — treat these as directional, not a same-generation apples-to-apples test.

Until both vendors publish a matched benchmark run, the more reliable signal is a short pilot on your own tasks — coding, drafting, or analysis representative of your real workload.

• Claude Opus 4.8: ~88.6% on SWE-bench Verified.
• GPT-5: ~74% on SWE-bench Verified.
• Grok 4: ~75% on SWE-bench Verified.
• Gemini 2.5 Pro: ~71% on SWE-bench Verified.

Compliance: both inherit their vendor's platform coverage

Both models inherit their vendor's standard compliance stack rather than shipping unique certifications of their own.

GPT-5.6 inherits OpenAI's SOC 2, ISO 27001, and HIPAA BAA coverage on the API and Enterprise plans. Claude Sonnet 5 inherits Anthropic's SOC 2, ISO 27001, and HIPAA BAA coverage on the same tiers.

Confirm the exact model name is listed in your BAA or enterprise agreement before sending regulated data to either model.

• GPT-5.6: OpenAI SOC 2, ISO 27001, HIPAA BAA.
• Claude Sonnet 5: Anthropic SOC 2, ISO 27001, HIPAA BAA.

How to choose for your business

Choose Claude Sonnet 5 if cost per token and multi-agent, production-scale work matter most. Choose GPT-5.6 Sol if you regularly hit problems hard enough to need max or ultra reasoning modes.

Run a short pilot on your actual workload before committing budget. Token cost differences compound fast at volume, so test both on representative tasks first.

• Cost-sensitive, high-volume, multi-agent work: Claude Sonnet 5.
• Hardest single-thread problems needing deep reasoning: GPT-5.6 Sol.

The Verdict

Both models are generally available today, so the choice comes down to price and workload shape rather than access. Claude Sonnet 5 costs 2-3x less per token and is built for multi-agent, enterprise-scale work; GPT-5.6 Sol costs more but adds max and ultra reasoning modes for the hardest individual problems.

For most cost-sensitive, high-volume production workloads, Claude Sonnet 5 is the stronger default. For workloads dominated by a handful of genuinely hard problems, GPT-5.6 Sol's reasoning modes can be worth the premium.