Claude Sonnet 5 matches Opus 4.8 performance but token inflation spikes effective cost
Anthropic’s Claude Sonnet 5 hits Opus 4.8‑level quality at a lower headline price, but a new tokenizer inflates token counts by 30%‑40%, effectively raising per‑token cost. The API drops temperature, top_p, top_k, adds a 1 M token context, and enables adaptive thinking by default.