Anthropic’s Claude Sonnet 5 is now the default model for Free and Pro plans, offering stronger agentic abilities than Sonnet 4.6 while staying cheaper than Opus 4.8. For many teams the main challenge is deciding when to use Sonnet 5 versus the more expensive Opus model, especially as effort levels affect both quality and cost. Sonnet 5 introduces low, medium, high and xhigh effort settings; higher effort improves reasoning but raises token usage and price. At low and medium effort Sonnet 5 delivers quality that previously required Opus pricing, making it a cost‑effective choice for routine agentic coding, bug investigation, and multi‑step workflows. However, at xhigh effort the cost can exceed Opus 4.8 for comparable results, so pushing Sonnet 5 to its maximum setting may erase its price advantage. Another practical concern is the updated tokenizer, which can increase token counts by up to 35 % compared with older models, affecting budget estimates if not accounted for. Teams should therefore map their tasks to effort levels: use Sonnet 5 at low or medium effort for most software engineering, data exploration, and business automation tasks; reserve Opus 4.8 for accuracy‑critical work where even small errors are costly; keep Haiku 4.5 for high‑volume, latency‑sensitive calls. By matching effort level to task difficulty and monitoring token usage with the new tokenizer, developers can reap Sonnet 5’s gains in tool use and context retention without unexpected cost overruns. #AI #Product #DevTools #ClaudeSonnet5 #AIModels #CostEffective