agent-workflows
What changed in Claude Code during September 2026?
September 2026 added Opus 5.5, Sonnet 5.5, server-side auto-mode checks, AGENTS.md fallback, and tighter subagent controls.
September 2026 added Opus 5.5, Sonnet 5.5, server-side auto-mode checks, AGENTS.md fallback, and tighter subagent controls.