Chapter BIterate: bad to betterPage 2 of 8

Iterate: bad to better

Run one-change loops

Change one meaningful variable, preserve the rest, and compare the result against the same goal.

~13 minCore mental model

Before you start

Why this matters

When a draft misses the mark, it is tempting to rewrite the whole prompt: add a role, three examples, a new format, a stronger tone instruction, and extra context all at once. The next answer may improve, but you will not know why. It may also regress in a way hidden by the many simultaneous changes.

A one-change loop treats prompting like a small experiment. Keep the task and evidence stable, adjust one meaningful instruction, observe the effect, and decide whether to keep it. This is not a scientific experiment with perfect control—model outputs vary—but it creates enough discipline to learn from each round.

1Learn the idea

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Define the stable core

Before round one, write the parts that should not move:

  • the user’s actual goal;
  • the source material and known facts;
  • the intended audience;
  • non-negotiable safety or privacy boundaries;
  • the required decision or action;
  • the success criteria.

Copy this core forward or explicitly say, “Keep the facts, audience, and constraints from the previous version.” Do not assume the assistant will perfectly preserve every detail. Review the result against the core after each revision.

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Choose one dial

Useful dials include scope, structure, length, reading level, tone, evidence handling, uncertainty, and level of detail. Change one dial with an observable instruction:

  • “Keep all facts, but put the decision and owner in the first two lines.”
  • “Keep the structure, but replace specialist terms with language a new employee can understand.”
  • “Keep the content, but distinguish confirmed facts from assumptions in separate lists.”
  • “Keep the recommendation, but add one credible alternative and its tradeoff.”

These are stronger than “be clearer” because you can inspect whether the requested change occurred.

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Use a repeatable cycle

Run five steps:

  1. Observe: Identify the highest-impact gap.
  2. Predict: State what one prompt change should improve.
  3. Revise: Ask for that change while preserving the stable core.
  4. Compare: Put the old and new outputs against the same criteria.
  5. Decide: Keep, reject, or modify the change.

Write down a short result such as “Moving the decision first improved scanability but removed the reason; keep the new order and restore one evidence sentence.” Your next round now has a focused job.

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Control the conversation

Long chats accumulate instructions, examples, and corrections. Later directions may conflict with earlier ones. After several rounds, restate the current specification in one clean prompt or begin a fresh conversation with the selected source material. This reduces accidental dependence on obsolete feedback.

Version labels help:

  • V1: original draft;
  • V2: decision first;
  • V3: decision first plus evidence sentence;
  • V4: shortened to 120 words.

Do not overwrite the only copy. A later version can sound smoother while losing a crucial fact from V2.

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Account for variation

The same prompt can produce different wording across runs. Do not conclude that a prompt edit caused improvement from one lucky output. For an important reusable prompt, test it on several representative inputs. A support-summary prompt that works only on neat tickets is not robust.

Hold the test cases stable and include difficult examples: missing dates, contradictory notes, emotional language, or unusually long input. The goal is not identical prose. The goal is consistently satisfying the requirements.

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Know when multiple changes are justified

One-change loops are a learning method, not a rigid law. If an answer leaks personal information or fundamentally misunderstands the task, stop and rewrite the specification. Safety and correctness take priority over preserving experimental purity. Record that you changed several things because the baseline was unusable.

For routine low-risk work, speed may matter more than diagnosis. You can make a combined edit when the repairs are independent and obvious. The discipline still helps: name what changed so you can inspect it.

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