Anthropic announced Claude Sonnet 5 on June 30, 2026, with promotional, time-bounded rates: input tokens cost $2 per million and output tokens cost $10 per million until August 31. Pricing will revert to $3 and $15 respectively on September 1. Analysts at Decrypt called the window "near-Opus performance at Sonnet fees." Sonnet 5 introduces a revised tokenizer that maps text to 1.0–1.35 times more tokens, potentially increasing invoices even before list prices rise. A legacy summarization pipeline producing 50,000 words daily previously translated to roughly 65,000 tokens under Sonnet 4.6, but the new tokenizer may register 85,000 tokens. Anthropic’s platform offers batch processing and prompt caching as mitigations: batch requests provide about 50 percent off both input and output units, while prompt cache hits discount repeated inputs by up to 90 percent. These levers can keep API costs flat even when headline rates escalate, but enterprise buyers often overlook integration work during proof-of-concept phases.