Claude Platform Release NotesLaunchClaude Watch
Claude platform release notes: September 28, 2026
This is a planned refresh across the deployment surface, which means Anthropic is confident enough in stability to push changes everywhere at once. The breaking changes matter: if you're on Claude Sonnet 5, you're on a deprecation clock. What changed: thinking mode control shifted, forced tool use now errors, system prompts have new constraints. Update your integrations this week before the downstream bugs pile up. This also signals that Anthropic is competing on release velocity in the speed tier, not just at the top.