Claude Sonnet 5 vs Opus 4.8: Is the Flagship Worth 2.5×?
Claude Opus 4.8 costs 2.5× Claude Sonnet 5's intro rate for a 3.4-point edge on SWE-bench Verified — 88.6 vs 85.2, as of July 2026. On most workloads that premium is wasted; on long-horizon agentic work with expensive retries, it pays for itself. After September 1 the multiple compresses to roughly 1.7×, which flips the math for borderline tasks. For PMs, the answer is a routing policy — Sonnet 5 by default, Opus 4.8 on logged escalation — not a single model choice.