August 31, 2026: Sonnet 5 Reprices, GPT-5.4 Exits Codex, and Two Kimi Models Sunset on the Same Day
Three unrelated events landed on the same date. Claude Sonnet 5's API launch pricing expired, moving from $2 input and $10 output per million tokens to the standard $3 and $15. GPT-5.4 and GPT-5.4 mini stopped being offered to Codex users signed in with a ChatGPT account, replaced by GPT-5.6 Terra and Luna. Moonshot AI sunset kimi-k2.5 and moonshot-v1 on the same day, with kimi-k3 as the stated migration target. The layer most people miss is the second one: Sonnet 5 also changed tokenizer, so the same input now maps to 1.0x to 1.35x more tokens, which compounds with the rate change to a 65% to 100% real increase on coding workloads and close to 50% on plain text, while leaving Consumer subscriptions untouched. This piece splits the three events into sunset, replacement, and repricing, gives the urgency and response for each, and closes with a two-month expiry calendar: Claude Code limits on 2026-09-14, DashScope retiring 30-plus model IDs on 2026-10-10, deepseek-chat and deepseek-reasoner deprecated on 2026-10-24, OpenAI leaving Cursor on 2026-11-12, and the GPT-5.6 Sol promotion ending around 2026-11-21. Prices are a 2026-08-31 snapshot and source disagreements are flagged inline.