Use it now Notable
A new --system-prompt-snapshot option makes a session record its system prompt once and reuse it on resume.
A new flag, --system-prompt-snapshot <on|off>, is now passed to spawned agent and subagent processes and threaded through session state as systemPromptSnapshot across many call sites. It lets a forked or background session record the system prompt once and reuse it verbatim on resume or subsequent requests, instead of recomputing it live. It defaults to on for the built-in system prompt and off when --system-prompt or --append-system-prompt is passed.