Models & prompts
System prompt updates clarify when to spawn subagents, emphasize handling multi-angle work inline rather than delegating, and adjust guidance on parallelism, plan mode, focus mode, and context management. Rejection and interruption messages were also revised for consistency.
Under the hood
Added support for the CLAUDE_CODE_TOTAL_TOKENS_REMINDER, CLAUDE_IN_CHROME_DOMAIN_RULE_TOOL, CLAUDE_IN_CHROME_MCP_SERVER_NAME, and CLAUDE_IN environment variables. Several new internal feature gates were introduced related to background execution, Chrome auto-enable flows, MCP first-party authentication, and related subsystems.
Upgrade notes
No manual steps required.