Tutorials, deep dives and product notes — built for developers.
Claude Sonnet 5 vs Sonnet 4.6: every benchmark, every gain. +13.4 Terminal-Bench 2.1, +10.6 HLE tools, +5.1 SWE-bench Pro, +223 GDPval (beats Opus 4.8). Same $3/$15 list price. Tokenizer caveat explained. Full comparison with bar charts, radar, and gains chart — all sourced from Anthropic's Sonnet 5 System Card.
Anthropic's two best non-Mythos models face off. Claude Opus 4.8 ($25/1M, 69.2% Pro) leads Sonnet 4.6 ($15/1M) on all benchmarks by 1-13 pts. But Sonnet handles 1M context at standard pricing, costs 1.7x less, and was preferred by devs over Opus 4.5. Full sibling comparison.
Both $15/1M output. GPT-5.4 is faster (242.5 char/s vs 173.3 on CodingFleet) and stronger on benchmarks (SWE-bench Pro +14, Terminal-Bench +16). Sonnet 4.6 counters with 90% cache discounts, no long-context surcharge, and mature Claude Code ecosystem. The real verdict: use both.