Claude Code 2.1.215

• [changed] Subagent use is more conservative. Claude is instructed not to spawn agents unless you ask (or name a specific agent type), and not to treat “thorough,” “multiple angles,” or multi-part tasks as an automatic reason to fan out.
• [changed] Clearer rules for when not to delegate: small bounded sub-tasks stay inline; no spawning just to review or double-check work that fits in the main loop; no parallel subagents for one modest job.
• [changed] When work is delegated, Claude is told to commit to it — avoid redoing the subagent’s searches while it runs, and avoid re-deriving findings after it reports.
• [changed] Agent-tool guidance stresses matching specialized agents to the task description and not duplicating research a subagent is already doing.
• [changed] Plan/verification wording continues to push an end-to-end verification section (run the code, MCP tools, tests) when outlining work.
• [fix] SDK compatibility list now includes 0.3.199.

Models & prompts

• Built-in agent prompts emphasize cost and context: each spawn starts cold and re-derives context you already have, so inline tools are preferred unless you explicitly request a subagent.
• Background-subagent messaging is clarified (notifications on completion; don’t invent pending results). Availability of run_in_background / name / remote isolation still depends on the runtime mode (e.g. teammates can’t spawn teammates).
• Worktree isolation copy remains explicit: changes in a separate working copy do not affect the main working directory.

Under the hood

• Internal flags and gates for workflow size warnings (agents/tokens), policy-skills disable, launch composer, voice interim forwarding, and related experiments.
• OAuth / host auth refresh path refreshed (timeout knobs, token-cleared events, older refresh-lock and invalid-grant gates removed or replaced).
• Assorted experimental env toggles added or retired (e.g. cold compact, native cursor, force bridge, session attribution suppress, nonstreaming fallback).

Upgrade notes

• Expect fewer unsolicited subagent launches on ordinary multi-step requests; say so explicitly (or name an agent type) when you want fan-out.
• No migration steps required for typical CLI use; optional native package resolution picks up 2.1.215 automatically.