If you wired the experimental prompt-tools endpoints into anything — `/v1/experimental/generate_prompt`, `improve_prompt`, or `templatize_prompt` — today's the day they stop answering. Anthropic flagged this back in July, and the cutover is now here: after removal those routes return an error instead of a completion. The legacy Workbench console goes dark on the same date. The fix is boring but real. Grep your codebase for the three paths before something in production trips over them. Anything you stashed in the old Workbench — saved prompts, variables, evals — needs exporting today too, from the in-app banner or your Organizational Settings, or it's gone. Never touched the experimental prompt APIs? Then this one's a no-op — move on.