Claude Code 2.1.219: nested subagents, sandbox allowlist, new hooks
Opus 5 is now the CLI's default at $10/$50 fast mode, subagents orchestrate three levels deep, and untrusted sandboxed commands can be walled off the network.
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Opus 5 takes the default slot
Version 2.1.219 promotes claude-opus-5 to the default Opus model with a 1M-token context window, and its fast mode now runs $10/$50 per Mtok. Opus 4.7 is dropped from fast mode; /fast now applies to Opus 5 and 4.8.
Subagents now nest three deep
Default subagent spawn depth jumps to 3, so an orchestrator can spawn sub-orchestrators that spawn workers — real multi-level fan-out for large tasks. Set CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH=1 to return to flat fan-out. Stream-json now forwards nested subagent events at depth 2+.
Wall sandboxes off the network
The new sandbox.network.strictAllowlist setting denies every non-allowlisted host for sandboxed commands without prompting — a hard boundary when you're running untrusted or agent-generated code.
DirectoryAdded hook fires mid-session
A new DirectoryAdded hook runs right after /add-dir or the SDK's register_repo_root adds a working directory, so you can auto-load context or trigger setup the moment a repo joins a live session.
A governor on runaway workflows
The new workflowSizeGuideline setting caps how many agents a workflow may spawn (hidden once set via /config) — a brake on multi-agent runs before they balloon your token bill.
/code-review moves to the background
As of 2.1.218, /code-review runs as a background subagent so your main session keeps working while it reviews. Version 2.1.217 also shipped :emoji: shortcode autocomplete, toggleable with emojiCompletionEnabled.