Assumption inventory

Assumption Inventory

Before a long run, the cheapest bug to fix is a wrong premise. This skill is a preflight: surface the assumptions the next stretch of work rests on, separate what you can cite from what you are guessing, and confirm the load-bearing guesses before the work starts — not after the diff lands.

The mechanism is one distinction held strictly: a fact is something on disk or stated by the user (it gets a citation); an assumption is everything else (it does not). The danger is an uncited assumption quietly becoming load-bearing — the work builds on it, and the divergence only surfaces hours later. This skill drags those assumptions into the open and gates the load-bearing ones on evidence or confirmation.

This is the front end of the triad: assumption-inventory (before), reground (mid-drift), fresh-eyes (after). Run it in order; do not skip to step 4.

1. Decide whether to run

Run this when the work ahead is long, expensive, hard to reverse, or multi-step and the target is not already crisply pinned. Skip it for a one-line change with an explicit target — the ceremony is not free. When in doubt on a big task, run it.

2. Draft the inventory

Fill every slot. For each, tag the basis: [cited: file:line / user said X] for a fact, [assumption] for a guess. Do not leave a slot blank — "unknown" is a valid, important answer.

• Goal — what outcome am I trying to produce, in one sentence? Why now?
• Root / scope — which repo, directory, or workspace is this rooted in? Is it workspace-wide or one repo? What platform(s) must it run on?
• May edit — which files / areas am I allowed to change?
• Must not touch — what is off-limits (generated files, other repos, prod config, contracts other code depends on)?
• Done means — what concrete, checkable state counts as complete? How will I know?
• Open questions — what do I not know yet that could change the above?

3. Stress the assumptions

For each [assumption], ask: what is the cheapest evidence that would settle this, and have I looked? Then look. Read the file, run pwd / git remote -v, check for a CLAUDE.md or ADR, grep for the symbol. Cheap checks turn guesses into citations now, before they cost anything. See REFERENCE.md for the catalog of assumptions that are silently wrong most often (platform, scope, auth, volatile contracts) — check those by default even when they feel obvious.

4. Classify and gate

Sort every surviving [assumption] by whether it is load-bearing — would the work be wrong, wasted, or harmful if it turned out false?

• Load-bearing and unconfirmed → blocking. List it as an open question and ask the user before proceeding. This is the whole point of the skill.
• Not load-bearing → state it explicitly as a stated assumption and proceed; the user can correct it cheaply because it is visible.

Pressure-test the acceptance criteria specifically. The plan usually carries the "done means" criteria — but this is the moment to test them, not inherit them. Flag any criterion that is either weak (vague, unmeasurable, or untestable — "works well", "is fast", "handles errors") or built on an unproven assumption (it presumes a behavior, contract, schema, or file that step 3 could not cite). A criterion no one could objectively mark true or false, or one resting on a guess, is a blocking item — the plan looked done but its bar is soft. Surface these alongside the load-bearing assumptions; they are often the most valuable thing this preflight catches.

5. Ask the blocking questions, then proceed

Show the user the filled inventory as the written report (template in REFERENCE.md) — that technical record stays. But for the blocking items, do not just list them in prose: ask them with the AskUserQuestion tool. A structured question forces a decision and makes the boundary explicit, where a prose note is easy to skim past. Reach for it whenever the uncertainty is about what to do or where the edge of the task is — the things the plan should have settled but didn't. Typical questions worth raising:

• Boundary — "Is X in scope or out?" / "Does this stop at the API, or include the UI?"
• Interpretation — "The goal could mean A or B — which?"
• Acceptance criteria — "This criterion is unmeasurable / rests on an unproven assumption — how should 'done' actually be judged here?"

Offer concrete options (e.g. in scope / out of scope / defer) so the answer is a click, and recommend the one the evidence favors. Keep it tight — only genuinely load-bearing uncertainties become questions; the do not over-ask guardrail still holds, and if nothing is truly uncertain, say so and skip straight to proceeding. Stated non-blocking assumptions need no sign-off — they proceed unless corrected. Once the blocking questions are answered, the inventory (plus those answers) is the brief for the run; carry it forward and check work against it.

Guardrails

• Never silently upgrade an assumption to a fact. If you did not cite it, it is still a guess, no matter how confident it feels.
• Default to portable, not this-machine-first. "Works on my OS / with my logins / in this repo" is an assumption, not the goal — surface it, do not bake it in. See REFERENCE.md.
• Do not over-ask. Only load-bearing, unconfirmed assumptions block. Burying the user in confirmable trivia is its own failure mode — check the cheap ones yourself first.
• This skill plans, it does not build. Its output is the confirmed inventory, not a started implementation. Begin the work only after step 5.