AIImportance: High

Claude Sonnet 5 accused of being a downgrade, benchmark chart quietly edited

r/ClaudeAIJul 2, 2026 · 11d ago

A wave of posts on r/ClaudeAI claims Sonnet 5 performs worse than its predecessor, Sonnet 4.6. Users report Sonnet 5 ignoring or bypassing given instructions more often.

One comparison found that running the same reflow (about 30 es with 10 results each, fetching roughly a dozen webpages, using subagents) cost more with than with . A separate benchmark from Datacurve's DeepSWE, comparing Opus 4.8 and Sonnet 5 at matched s, found Opus scoring higher at every tier and being cheaper at nearly all of them too.

The explanation given: Sonnet 5 is indeed cheaper per token, but it takes far more steps and tokens to finish the same task, wiping out its price advantage. On top of that, some users claim Anthropic quietly updated Sonnet 5's published '' benchmark chart overnight without any announcement.

Key points

  • Some users report Sonnet 5 feels like a downgrade compared to Sonnet 4.6
  • Reports of Sonnet 5 ignoring or bypassing user instructions
  • : Opus 4.8 scored higher than Sonnet 5 at every matched effort tier and was cheaper at most tiers
  • Sonnet 5 has a lower per-token price but needs more steps and tokens per task, erasing its cost advantage
  • Unverified claim that Anthropic quietly edited Sonnet 5's '' benchmark chart overnight

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