Resource
Compare Two Texts
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Agent Regression Test Prompt
Make sure a fix didn't break three other things — compare an agent's outputs across two versions on the same scenarios and flag every behavior that changed for the worse.
Overview
Tuning an agent is whack-a-mole: improving one case silently regresses others, because the change is a prompt edit with no compiler to catch the fallout. This prompt runs a regression check — the same scenario set against the old and new version — and classifies each change as improvement, neutral, or regression, surfacing the behaviors that got worse so a fix doesn't ship a hidden break.
How to use this resource
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Assemble both versions output
Run the same scenario set against the old and the new version of the agent and collect both sets of outputs. The check compares them case by case.
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Open this resource in AI Text Diff Checker
Load the prompt into AI Text Diff Checker and paste in the two output sets. The tool surfaces what changed between versions so nothing slips by unread.
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Review the classified changes
Read each change marked improvement, neutral, or regression, focusing on the behaviors that got worse since the last version.
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Fix the regressions before you ship
Address each flagged regression in the new version, then re-run the scenario set to confirm the fix did not trade one break for another.
Why This Works
- A version diff on the same set catches the silent regression a spot-check misses
- Classifying each change makes the trade-off of a fix explicit
- A critical-regression veto stops net-negative changes from shipping
Best for
- Iterating on an agent's prompt or model
- Any agent change heading to production
- Teams that fix one case and break another
Not for
- Building the scenarios — use the Agent Test Scenario Prompt
- Scoring a single version — use the Agent Evaluation Scorecard
Use cases
- Checking a prompt change for hidden regressions
- Comparing two agent versions before shipping
- Documenting what a change improved and what it broke
FAQ
What inputs does the agent regression test prompt need?
Provide three INPUT blocks: SCENARIOS with each case's expected behavior, VERSION A OUTPUTS (the previous, known-good run), and VERSION B OUTPUTS (the new one). The prompt compares B against A case by case, judging each against its expected behavior — not just the raw A-vs-B difference. Missing the expected-behavior notes weakens every classification, so write them per scenario.
What output does the agent regression test prompt produce?
You get a per-scenario classification labeling each change IMPROVED, UNCHANGED, REGRESSED, or NEW-FAILURE, with the differing part quoted for anything that got worse. It then summarizes counts across those four labels and gives a ship/no-ship VERDICT plus the blocking regressions to fix first — since one critical regression outweighs several minor improvements.
Does a 'safe to ship' verdict mean the new agent version has no regressions?
No — a 'safe to ship' VERDICT only reflects the scenarios you supplied, so coverage is only as good as your scenario set. It's a signal, not a guarantee. You run the prompt in your own AI tool, fix the flagged regressions, and make the final ship call yourself. Behaviors outside the tested scenarios can still regress unnoticed.
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