Last verified: August 20, 2026 TL;DR: For pure coding benchmark performance, GPT-5.5 and Claude Opus 4.8 are virtually tied (~88.7% SWE-bench Verified). However, on the harder, contamination-resistant SWE-bench Pro benchmark, Claude Opus 4.8 leads decisively (69.2% vs 58.6% for GPT-5.5). Gemini 3.1 Pro trails in Verified (80.6%) but offers a 1M-token context window and native multimodal input, making it ideal for agentic workflows that ingest large codebases, diagrams, or video. Beyond benc...