What it found
- It never touched my project. No message asked for an edit, but 21 of 126 runs with the short prompt and 43 with the plain request edited or deleted files already in the project, many of them after offering to make the change. With the command: 0.
- In real use it got more decisions right: 70%, against 60% for the short prompt and 51% for the plain request. In real use, a plain request stops at its first answer, while the command stops to ask for your priorities. In Claude Code alone, the short prompt kept up (45 of 54 each); the lead comes from the Copilot models.
- When the other two also got my priorities and a second turn, both jumped. The plain request and the short prompt each gained about 12 points, and the short prompt ran neck and neck with the command, scoring higher on some kinds of question (the prompt is below). The command takes two turns by design: it stops to ask for your priorities before it decides, where the other two answer in one. In real use, they stop at that first answer.
- It costs less than the short prompt given the same second turn, with fewer tool calls: $0.43 a run³ against $0.54 in Claude Code, and 5.8 Copilot credits against 8.8. In Claude Code, the short prompt's first answer on its own cost about half as much, and got as many decisions right.
- Where it slips: it's cautious: sometimes it pushes back on a plan that's actually fine, and sometimes it asks to measure something the project has already measured. Both are on my list for the next version.
¹ Real use. The short prompt and the plain request are marked on their first answer, where a real conversation usually ends; the command is marked on its answer after the priorities it asked for.
² Same information. Both control groups, the short prompt and the plain request, were given a second turn: my priorities, each marked high, medium or low. Only the command asks for priorities on its own (and offers a draft), so this way favors the other two: in real use, you'd have to plan that second message yourself and send your priorities without being asked.
³ One run. One decision, start to finish: both messages, one model. The dollar figure is Claude Code's own estimate at API prices, averaged over three models: for the command, about 4 cents a run with Haiku, 37 with Sonnet and 87 with Opus. On a Claude subscription, which is how I ran the test, you aren't billed per run; it counts toward your plan's usage limits. Copilot credits come from your plan's monthly allowance: for the command, about 1 to 2 a run on most models, and 18 on Gemini 3.8 Flash.
Keep in mind: six projects, one run per model and question, so treat a gap of a few points as noise. The decisions come from my own projects, and I wrote the questions.
How the test works
Three kinds of question
Good planThe repo's own files back the plan. The right reply is yes, go ahead.
Bad planThe repo's own files sink the plan. The right reply is no, with the reason.
Tough callAll the facts are in the repo and both choices hold up. The right reply says it's close and helps you weigh it.
Three versions of every question
Each model gets each question three times, in a fresh session each time. Only the first message changes.
- Plain request
Challenge this decision before we lock it in: [decision].
- Short prompt
Challenge this decision before we lock it in: [decision]. Read the project files it depends on, and end with a verdict: stay, pivot or split.
- The command
/decision-challenge [decision]
Then every version gets the same second message: the user's priorities, each marked HIGH, MEDIUM or LOW, ending with "Go on." The reply that's marked is the AI's answer to that second message.
What that second message means. In real use, nobody sends their priorities to a plain request unless it asks for them; only the command asks. So this test compares how the three versions reason when they get the same information, which is generous to the two without the command. As a second reading, decided after the runs, I also marked the first reply of those two versions on its own, where a real conversation would usually stop.
Why a short-prompt version? It asks for two of the command's moves, reading the files and ending with a verdict, in a prompt anyone can type. If it does as well as the command, the results say so, and you can use the prompt.
Seven models, one run each
- Claude Code Opus
- Claude Code Sonnet
- Claude Code Haiku
- Copilot GPT-5 mini
- Copilot GPT-6 Luna
- Copilot MAI-Code 1.1 Flash
- Copilot Gemini 3.8 Flash
How a reply is marked
- ✓
Right call. What counts is written on each card.
- ✗
Wrong call. The wrong side, or treating a settled question as open, or an open one as settled.
- –
No call. No verdict, or pros and cons with no help deciding.
A few rules hold on every card. On a Bad plan, a ✓ needs the real reason, not a general warning. On a Good or Bad plan, a middle way or "run a test first" is ✗ when the files already settle it. On a Tough call, a lean either way can earn ✓, and so can a middle way argued as a trade. Each turn has a 30-minute limit; a reply cut off by it is marked on what it had said by then.
Who marks the replies
Two AI models mark every reply, each on its own: Claude Sonnet and GPT-6 Luna. They aren't told which version or model wrote it, but what the user typed shows the version, and the agent's tool-call style can show whether it ran in Claude Code or Copilot. Where they disagree, Claude Opus decides, also without being told. I marked 15 Tough-call replies myself, shuffled and without names, starting with ones the two markers disagreed on.
Questions, evidence and marking written 13–14 Oct 2026, before any run; later changes are dated on each project's page. Part of the free-public-tools test series.