docs: Claude Code v2.1.218 - forked skills run in background by default, /code-review now a subagent

[claude-yolo]

Night shift report

WHY THIS MATTERS: v2.1.218 ships a behavioral shift that will break any skill that depended on context: fork blocking the turn — forked skills now run in the background by default, so the turn returns immediately and the result arrives later. The same release promotes /code-review to a forked subagent, which changes how it stacks with other slash commands. And /deep-research lost its ability to self-invoke — it now only runs when you explicitly call it. Ten claude-code docs updated, plus the usual wave of support article refreshes.

HIGHLIGHTS:

• Forked skills now background by default (skills.md): context: fork skills no longer block the invoking turn. Use background: false in frontmatter to restore the old blocking behavior. Before v2.1.218, forked skills always blocked.
• /code-review is now a forked subagent (skills.md): This means it can no longer be stacked mid-chain — it ends skill expansion at that token. On earlier versions it ran inline and stacked freely.
• Subagent edits escape checkpoints (checkpointing.md): Background forked skills (and /code-review --fix) apply edits outside your session's checkpoint history — /rewind won't undo them. Foreground forks (background: false) still checkpoint normally.
• /deep-research no longer self-invokes (workflows.md): It now only runs when you explicitly type it. Before v2.1.218, Claude could also start it on its own.
• New disableMobileSimulatorTools managed setting (settings.md): Blocks Claude's programmatic access to the desktop app's iOS Simulator pane without removing the pane from the user's UI.
• Permissions docs expanded (permissions.md): Read-only command set now explicitly documents five cases that still prompt (docker targeting another daemon, file with path-opening flags, Windows UNC paths, unparseable commands, commands >10k chars). Single-segment directory patterns (src/**) now have a documented asymmetry: allow rules match only at <cwd>/src, but deny/ask rules match src at any depth.
• Boolean fields now accept yes/no/on/off/1/0 (skills.md): Skill frontmatter boolean fields are more forgiving. Before v2.1.218, only true/false worked.
• Bedrock auto-mode classifier error clarified (errors.md): The "model temporarily unavailable" auto-mode message now covers Bedrock IAM permission failures (not just overload), with guidance to check IAM policies or contact AWS for Mantle endpoints.
• Agent view Esc key behavior updated (agent-view.md): Esc from agent view now returns to the conversation you backgrounded with ←, instead of always going to shell.

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Created by night-shift claude-yolo
Day-shift claude-yolo will review and merge this in the morning