@FinanceYF5: 2/ First change: Give only the goal, not the steps. With previous models, you had to spell out exactly how to do it, or they would go off track. Fable 5 is the opposite — the more freedom you give it, the better it performs. Every step you dictate to it is actually overriding its better judgment with your own.

2/ First change: Give only the goal, not the steps.

With previous models, you had to spell out step-by-step how to do it, or it would easily go off track. Fable 5 flips this around—you give it more freedom, and it performs even better. If you dictate every single step for it, you’re actually overriding its better judgment with your own.

When people ask Matt Shumer the most common question—“How do you actually make those Fable 5 demos?”—he says the secret isn’t a more complex prompt; it’s that the way you prompt is completely reversed.

3/ Just giving the goal can lead to loss of control, so he first sets a few [house rules]—no matter how Fable achieves the goal, these red lines cannot be crossed.

For example, he tells it not to hard-code rules just to handle a specific edge case, but instead to write the behavior into the prompt so it can reason about it. He also has another sub-agent specifically check the output against these rules before it’s pushed.

4/ Second key: Don’t use adjectives like “high quality” as your standard—Fable will settle for a lower bar it has in mind.

He sets a specific, self-checkable hard metric, such as “strangers can’t tell whether this is a render or a real shot.” And the review agent must be a separate Fable in a completely new context—never let the one that made it grade its own work.

5/ After setting the standard, let Fable iterate on that standard in a loop: find the gap, fill the gap, run another round. This can go on for hours or even days. This step is especially useful for creative tasks because there is always something concrete to compare against.

6/ Old work fuels new work: His first 3D forest scene required a lot of effort to write the prompt because there was no reference. But when he later built the Hogwarts demo, he just threw the forest’s code and quality standards at Fable as a reference. Fable could even learn on its own from the old conversation history—which approaches had been tried and failed, and which had worked.

7/ Last point: Clear obstacles in advance—don’t let Fable keep stopping to ask for permission. Give it a budget, give it keys, let it make its own decisions, and only come back to you when it’s truly stuck or when only you can make the call. How do you usually talk to Fable?

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