Anthropic's Claude Sonnet 5, released in late June 2026, has introduced a tokenizer that inflates developer API costs. While marketed at $2.00 (KES 262) per million input tokens, an audit by Playcode found the tokenizer consumes up to 73 percent more tokens than OpenAI’s GPT-5.x family for identical code files. Anthropic acknowledged the updated architecture maps text to roughly 1.0 to 1.35 times more tokens, but independent tests show a steeper penalty: processing identical TypeScript files generated 1.73 times more tokens than OpenAI's tokenizer, and a 90,000-line C++ repository resulted in 2.2 million tokens on Claude versus 1.12 million on GPT. Sonnet 5’s $2.00/M input rate effectively behaves closer to a $3.46/M rate for coding environments. On September 1, 2026, Sonnet 5’s input price increases to $3.00/M, compounding the financial impact. The tokenizer was also deployed with Opus 4.8 and Fable 5 models.