Verdict: in the Claude Sonnet 4.5 vs GPT-5 comparison, Claude Sonnet 4.5 wins on coding and agentic work, scoring 77.2% on SWE-bench Verified against GPT-5's 74.9% ( Anthropic , OpenAI ). GPT-5 wins on price, listing at $1.25 input and $10 output per million tokens versus $3 and $15 for Sonnet 4.5, and it leads on competition maths and multimodal understanding. Pick Sonnet 4.5 if your primary workload is writing and refactoring code inside an agent; pick GPT-5 if you are running high token vol...