Summary
Claude Code v2.1.212 (released July 6–17, 2026) introduced a suite of agent lifecycle and safety improvements: an automatic diagnosis-and-fix command (/doctor), background session forking (/fork), session-wide usage caps for web search and subagents, automatic backgrounding of long MCP tool calls, a resurrectable session picker (/resume), and several security hardening measures. The release also added an in-app browser on desktop, an EndConversation tool, and screen reader mode, with Sonnet 5 as the default model offering 1M-token native context.
Additionally, three security‑relevant bug fixes were documented: worktree‑isolation escape, prompt‑only mode enforcement, and symlink‑based directory traversal. These bug classes are transferable to other agent frameworks and were verified present in the competing agent yoyo. Simultaneous competitor updates (Cursor 3.11, Codex July refresh, yoyo) tracked similar patterns: side channels, hook events, worktrees, parallel execution, and session caps.
Key Points
/doctor(aliased/checkup) becomes a full setup diagnostic that both finds and fixes problems — unused skills/MCP servers/plugins, deduplicatedCLAUDE.mdfiles, derivable content trimming, slow hooks — with confirmation before applying changes./forkcopies a conversation into a new background session, keeping the current session active; the old in-session subagent command was renamed/subtask.- Session-wide rate caps introduced:
CLAUDE_CODE_MAX_WEB_SEARCHES_PER_SESSION(200) and a 200-subagent spawn limit;/clearresets the budget. - MCP tool calls exceeding two minutes automatically move to background (controlled by
CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS). /resumeopens a picker of past sessions (including deleted ones) and resumes the selected one as a background session.- Auto mode now blocks transcript tampering and prompts before
rm -rfon unresolved variables. - Bash permission hardening: fd-redirect forms fail closed, commands over 10k characters always prompt, subscripts in prompt, and previously auto-approved help/man holes are closed.