Both Sonnet 4 and Opus 4 will stop accepting requests on June 15 — not soft-deprecated, fully offline. The successors are Sonnet 4.6 and Opus 4.7+; any hardcoded model string pointing to the old versions will start returning errors that day. This is a separate action from the billing pool split also landing June 15. One is a config change in your billing settings; this is a code change in every place you specify a model ID. If you haven't audited your model strings yet, the deadline is the same but the fix is different.