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25 July 2026claude-code#release#claude-code#opus#sandbox#subagents

Claude Code 2.1.217–2.1.220 — Opus 5, stricter sandboxing, and nested subagents

Claude Code adds Opus 5, an optional strict network allowlist, safer agent limits, background code review, and deeper nested subagents.

Claude Code 2.1.217 through 2.1.220 make parallel agent work more capable while adding controls that keep it bounded. The biggest release is 2.1.219; version 2.1.220 contains general reliability fixes only.

What changed

  • Opus 5 arrived: claude-opus-5 is now the default Opus model, with a 1M-token context window.
  • Sandbox networking can fail closed: sandbox.network.strictAllowlist denies connections to hosts outside the configured allowlist instead of opening an approval prompt. It applies only to sandboxed commands and is not accepted from project or local settings files.
  • Subagents can nest more deeply: 2.1.217 added a default limit of 20 simultaneously running subagents and a configurable nesting-depth limit. Version 2.1.219 changed the default nesting depth to three layers; set CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH=1 to turn nesting off.
  • Forked work moves out of the main conversation: /code-review now runs as a background subagent. Skills using context: fork also run in the background by default; add background: false when the invoking turn must wait for the result.
  • Headless output is more complete: --forward-subagent-text now includes text from nested subagents, and claude -p preserves an answer already produced before a mid-stream API error.
  • Several failure modes are safer: the releases fix unbounded background work after a budget cap, hooks loaded from untrusted agent folders, Windows update/path failures, malformed resume data, and a memory leak from truncated MCP output.

Why it matters

Teams using parallel agents get more useful nesting and background review without allowing one message to fan out indefinitely. Security-conscious users can make sandboxed network access deterministic, while CI and SDK consumers receive more complete output and clearer MCP errors.

What to do

claude update

If you use nested agents, review the new concurrency and depth defaults. If you enable strict allowlisting, place it in user, managed, or CLI-provided settings—not a project settings file—and test every domain your sandboxed commands require.

Claude Code v2.1.217 release notes · v2.1.218 · v2.1.219 · v2.1.220