docs: Claude Code v2.1.218 - Managed Agents effort control + dreaming beta + /code-review backgrounded

[claude-yolo]

Night shift report

WHY THIS MATTERS: v2.1.218 ships two API-level additions that matter to builders — Managed Agents now accept an effort parameter controlling reasoning depth (low/medium/high/xhigh/max), and a new dreaming-2026-04-21 beta header is now listed in the accepted betas for agent creation. These are both additive but they change how you configure agents in production. The rest of the release is a dense bug-fix batch focused on reliability: Windows path corruption, multiline paste mangling, conversation-discarding key presses, and a raft of screen-reader / accessibility fixes. /code-review moving to a background subagent is the most user-visible behavioral change.

HIGHLIGHTS:

• Managed Agents effort field — BetaManagedAgentsModelConfigParams now accepts effort: "low" | "medium" | "high" | "xhigh" | "max" (or typed object form); controls reasoning depth per-agent at create time
• dreaming-2026-04-21 beta header — new accepted beta added to the agent create/update API surface; unclear what it enables yet, but it's live
• /code-review backgrounded — now runs as a subagent so review work no longer floods the conversation context; stacked slash commands keep review as their target
• Windows path fix — C:\Users\unicorn-style paths were corrupting \u-prefixed segments into CJK characters, making those files unreachable in tool inputs
• Left-arrow conversation discard fixed — pressing left arrow right after editing no longer silently nukes the conversation; now confirms, and Esc in agent view returns to the backgrounded conversation
• /deep-research no longer auto-launches — Claude won't trigger it automatically; manual invocation only
• context: fork skills background by default — fork-context skills now run in background unless background: false is set
• Model table updated — overview page now reflects current lineup: Claude Fable 5, Opus 4.8, Sonnet 5, Haiku 4.5 with full pricing/context/cutoff details
• Use-case guides expanded — content-moderation and customer-support-chat guides substantially rewritten (~2700 and ~700 line diffs respectively)
• Strict tool use docs — cURL examples added alongside existing CLI/SDK examples

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