Claude Code 2.1.252

• [changed] Subagent use is more tightly constrained: spawn only when the user explicitly asks for a subagent or names an agent type. Multi-part or “thorough” tasks are handled inline instead of by defaulting to new agents (each spawn starts cold and re-derives context).
• [changed] Background subagent guidance is clearer — agents stay in the background by default so the user can interject; foreground (run_in_background: false) only when the very next step depends on the result. Pending agent results must not be fabricated or predicted.
• [removed] The alt+r keybinding has been removed.
• [changed] Focus-mode behaviour is reinforced: when focus mode is on, only the final text of each response is shown — intermediate tool narration is skipped and anything the user needs goes in that final message.
• [changed] Correction handling pushes durable memory writes in the same turn as the fix or diagnosis, rather than deferring them until later in the conversation.
• [changed] Connector discovery/resolve tooling copy and related “talking to the user” / SendUserMessage guidance are tightened (when to message, attachments, normal vs proactive status).
• [changed] Permission-denied and safety-classifier wording is tightened (err on the side of blocking; structured <block> responses where applicable).
• [changed] Chrome/browser tool loading still batches deferred tools into a single ToolSearch call; data-exfiltration and secret-sharing cautions remain explicit.

Models & prompts

• Built-in system and tool prompts push harder on not spawning agents unless asked, on honest background-agent status, and on putting user-visible answers in the right channel (final message in focus mode; SendUserMessage when that path applies).
• Conversation-summary prompts distinguish summarizing only the recent tail (earlier context retained) from full-session summaries used to seed a continuing session.
• Guidance on refusals vs ordinary sensitive-sounding work, autonomous/brief execution styles, scratchpad use, and thread resolve/reply behaviour is carried forward with wording cleanups.

Under the hood

• Agent-brief related configuration replaces earlier agent-parse flags (CLAUDE_AGENTBRIEF_* in place of CLAUDE_AGENTPARSE_*), including enforcement hooks for brief/proactive sections — groundwork for brief-style agent turns, not a separate user-facing mode by itself.
• SDK compatibility metadata no longer lists older tested wrapper versions 0.3.212, 0.3.214, and 0.3.215 (current range starts at 0.3.216).
• Package/version metadata and platform binaries updated for 2.1.252.

Upgrade notes

• If you used alt+r, rebind that action; the default is gone in this build.
• Expect fewer unsolicited subagent spawns on multi-step requests unless you explicitly ask for one.