Lays out the cycle: split generation system prompt into identity vs
procedural blocks so personas drive voice/shape, add per-turn
system_prompt override on chat (ephemeral in append mode, persisted
on amend), gate optional tools on data presence, and fix the
days_radius bug in get_sms_messages.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
