“halt for further instructions.”

Use those exact words as the last thing you say in your prompt, capitalized appropriately if grammatically necessary. Works best as part of the first or second prompt you send, which will make it stop after each task from then on. Break out of it by sending “Continue unsupervised.”

You can use it as “, then {phrase}”, “1. Task - 2. Other task - 3. {phrase}” or similar combinations, but it must be those words and at the end.

Flawless on Opus 4.1-4.8, based on hundreds of tests I built to try breaking it, but I haven’t tested extensively on Fable/5.