feasibility-probe

Feasibility probe

The highest-value thing an FDE does.

Why this exists

Everyone in the organization can write a spec. Almost nobody can tell you, in hours rather than weeks, what that spec means against the real code. That gap is where estimation failures come from — not from bad arithmetic, but from sizing work nobody had looked at.

The characteristic failure isn't the requirement that looks hard and is. It's the one that looks trivial: a field added to a response, which turns out to flow through a shared DTO used by four teams, a published contract with external consumers, and a batch job that parses the payload positionally. Nobody estimated that because nobody looked.

This skill looks. It is deliberately bounded — hours, not weeks — because its value is being fast enough to change the plan before the plan hardens.

When this applies

• A spec exists and someone is about to size it
• "How hard would it be to…?"
• A plan or a date feels optimistic and you can't yet say why
• Assessment engagements, where this plus a brief is the whole deliverable
• Before committing to anything in front of a stakeholder

When it doesn't

• Requirements aren't written yet — run requirements-to-spec first
• You already know the system deeply and the change is genuinely local
• You need the deep behavior of one flow — that's trace-the-flow, which this may tell you to run

Prerequisites

• .fde/03-requirements.md — you're probing these requirements
• .fde/02-system-map.md — you need to know where things are before asking whether they exist

Missing the system map, you'll re-derive it inline, badly and without citations. Run repo-recon first. If the engagement genuinely doesn't warrant it, say so in the Confidence line.

Procedure

Work requirement by requirement. Steps 1–5 per requirement, then 6–8 across the set.

1. Does this already exist?

Search before assuming absence. In a large enterprise system the capability frequently exists — partially, under a different name, disabled behind a flag, or built for a neighbouring use case two years ago.