release aidev BREAKING SIG 3/5

Claude Code 2.1.217: nested subagents off by default, concurrency cap, budget now halts background agents

Subagents no longer spawn nested subagents unless CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH is set, and concurrent subagents are capped at 20 by default — both change existing multi-agent fan-out setups. --max-budget-usd now denies new spawns and halts running background agents once the cap is hit.

PUBLISHED2026-07-21
OBSERVED2026-08-11
AGE21d
SOURCES1
  • Subagents no longer spawn nested subagents by default; raise with CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH
  • Concurrent subagents capped at 20 by default (CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS)
  • --max-budget-usd now denies new spawns and halts running background agents at the cap
  • Emoji shortcode autocomplete in the prompt input (:heart:); disable via emojiCompletionEnabled
  • Warnings when transcript writes fail (e.g. disk full) or session saving is off from an inherited env var, instead of silent loss
  • Fixed a memory leak retaining the full untruncated result of truncated MCP tool outputs for the session
  • Fixed Windows auto-update failures that could leave claude.exe missing; failed updates restore the preserved executable
  • Fixed background session isolation not canonicalizing symlinked working directories, letting sessions escape their workspace folder
  • Fixed auto-compact never triggering for Claude Opus 4.8 on Bedrock, and /compact failing once over the limit
  • Fixed corporate mTLS, TLS-verify, OAuth scope, and proxy settings ignored in Claude Desktop sessions
  • Fixed CLAUDE.md/SKILL.md paths frontmatter with many brace groups OOM-killing or stalling startup; brace expansion is now budget-bounded
  • Fixed --resume/--continue and /resume throwing a TypeError on a malformed transcript attachment
  • Fixed managed OTEL_EXPORTER_OTLP_ENDPOINT being overridden by lower-scope signal-specific settings
  • Screen reader mode: fixed the truncated startup announcement and the constantly re-rendering thinking row
  • Login-expiry warning moves from 5 days to 3 days before expiry
breakingfeaturefixsecuritycapability

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