Better Models, Worse Tools: Claude tool calls regress on Sonnet 5 and Opus 4.8
Armin Ronacher's controlled tests show Claude Opus 4.8 and Sonnet 5 produce ~20% malformed tool calls against Pi's edit tool; older models are clean.
Sonnet 5 launches at $2/$10, nears Opus 4.8
Anthropic's Claude Sonnet 5 launches 2026-06-30 with intro pricing $2/$10 per MTok (→$3/$15 on Sep 1), a new effort-level API dial, and a near-Opus cost-performance curve.