User Reports Sonnet 4.6 Outperforms Opus 4.6 for Practical Coding Tasks

A developer shared their experience switching from Claude Opus 4.6 to Sonnet 4.6 after encountering issues with over-engineering and incomplete work. The user had been using Opus 4.5 and 4.6 through the API, initially impressed but later discovering problems.

Key Issues with Opus 4.6

The developer reported that Opus 4.6 would mark work as "complete" when it was actually half-done. In one specific example, when asked to ensure a copytrade app used default risk settings to override scraped Telegram signals, Opus implemented a fix that worked but introduced a 500ms lag to the broker API. The lag occurred because Opus added code that checked risk settings twice, significantly slowing down the copy trader.

Sonnet 4.6 Performance

After switching to Sonnet 4.6, the developer observed:

• Huge drop in token burn (reduced API costs)
• More careful and thoughtful work output
• Sonnet identified and fixed the lag issue in 2 seconds
• Traced the performance problem directly to Opus's "fix"

The developer characterized Opus's approach as "over engineered without a thought to the result of the actual process," while finding Sonnet superior for practical implementation tasks.