Claude 5.1 Costs Rise 20% Despite Cache Cuts Due to Bloat and Watermarks

op7418 · x · 2026-09-02

Anthropic released Fable 5.1 and Mythos 5.1 with a 75% cache price cut, but real-world tests by Artificial Analysis show a 20% cost increase for tasks due to 1.7x higher token output. Users report rapid quota depletion and critical issues: lack of forced tool choice, broken model switching (legacy models can't read thinking blocks), and intrusive invisible text watermarks degrading output quality.

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