GPT-5.2 vs Claude Opus 4.5: The December 2025 Showdown

OpenAI's "Code Red" GPT-5.2 arrived December 11. Can it dethrone Claude Opus 4.5, the reigning coding champion?

OpenAI declared "code red" after Google's Gemini 3 release. Their response: GPT-5.2, released 3 days ahead of schedule. But Claude Opus 4.5 still holds the SWE-bench crown.

We've tested both extensively. Here's the definitive comparison.

Quick Verdict

Coding: Claude Opus 4.5 Dominates

The numbers don't lie. On SWE-bench Verified—real GitHub issues that require reading code, understanding context, and writing fixes:

• Claude Opus 4.5: 80.9% (first to break 80%)
• GPT-5.2 Thinking: 76.3%
• Gemini 3 Pro: 76.2%

That 4.6 percentage point gap matters. In real-world coding, Opus 4.5 solves problems others can't. The "effort" parameter lets you dial up thoroughness for complex bugs.

Professional Tasks: GPT-5.2 Edges Ahead

OpenAI introduced GDPval—a benchmark measuring knowledge work across 44 occupations. GPT-5.2 Thinking scores 70.9%, beating or tying top industry professionals on 70.9% of comparisons.

For lawyers reviewing contracts, doctors analyzing symptoms, or consultants building presentations—GPT-5.2 has the edge.

Hallucinations: GPT-5.2 Improves

OpenAI claims 30% fewer hallucinations than GPT-5.1. In our testing, this holds up. GPT-5.2 is more likely to say "I don't know" instead of confidently making things up.

Claude has always been more conservative, but GPT-5.2 narrows the gap significantly.

Pricing Comparison

Bottom Line

Choose Claude Opus 4.5 if: You write code professionally, need autonomous agents, or value safety and reliability above all else.

Choose GPT-5.2 if: You need the latest knowledge, do professional knowledge work, or want the fastest responses at a lower cost.

For most developers, Claude Opus 4.5 remains the better choice. For everyone else, GPT-5.2 is now very competitive.