These are the two heavyweight reasoning models of 2026. GPT-5.2 ships in Instant, Thinking and Pro tiers and is OpenAI's strongest model for long-horizon reasoning, agentic tool-calling and professional artifact work like spreadsheets and slides. Its Codex sibling is purpose-built for large refactors and migrations.
Claude Opus 4.5 is Anthropic's flagship for complex reasoning and agentic coding, posting class-leading SWE-bench scores and excelling in long autonomous agent runs with excellent instruction adherence. In practice, GPT-5.2 tends to edge agentic tool orchestration and document generation, while Opus 4.5 is prized for the cleanest, most reliable code and careful reasoning. Both are premium-priced, so most teams route everyday work to cheaper tiers (GPT-5.1, Claude Sonnet 4.5) and escalate the hardest steps to these two.
Which should you choose?
GPT-5.2
GPT-5.2 · 400K context
Pick it if
agentic tool use, multimodal tasks and polished documents matter most.
Claude Opus 4.5
Claude Opus 4.5 · 200K context
Pick it if
you want the cleanest code and most reliable autonomous agents.
GPT-5.2 leads on agentic tooling and document work; Claude Opus 4.5 leads on raw coding quality and steerable reasoning. Both are frontier: test them on your hardest real tasks.
Questions
Which scores higher on SWE-bench?
Claude Opus 4.5 posts class-leading SWE-bench Verified scores; GPT-5.2-Codex is very competitive, so the gap is narrow and depends on the task setup.
Are they similarly priced?
Both sit in the premium frontier band. GPT-5.2 is roughly $1.75 in / $14 out per million tokens; Opus is Anthropic's most expensive tier.