FIELD NOTE / X
Type-safe is not decision-safe.
The short film, the complete written thought, and the evidence behind it.
Type-safe is not decision-safe.
Video caption
Type-safe is not decision-safe. The wrong refund route is still a legal option value. Let types remove format errors; let outcomes earn trust. #EricFieldNotes
Full written post / accessible read
Jev's typed choice interface is a real engineering improvement when software needs a bounded judgment. Your code gets an enum instead of a paragraph to parse. But a valid enum can still select the wrong business branch with perfect schema compliance.
Imagine a refund decision returns 'approve' from an allowed list. The parser succeeds, but the account is outside the policy window. TypeSafe's own Jev 1.13 notes list difficulty with date comparisons, counting and indirection. That is a documented limitation, not a measured failure in this hypothetical refund case.
Build a held-out set with expired windows, missing evidence, adversarial state and the actual downstream records. Rename option labels while keeping written criteria fixed. A new preprint reports answer changes under option-name swaps in its tested decision heads; your integration still needs its own measured baseline.
Use Jev where a bounded semantic choice helps. Keep arithmetic and hard policy in code, provide a safe escape route, and require independently adjudicated cases before a decision can move money or access. Do this because a type system can close the answer space without proving the selected answer is right.
#EricFieldNotes
Evidence and boundary
On-screen label: VENDOR DOC + NEW PREPRINT. Illustrative cases are not measured incidents. Research papers and vendor documents support the stated mechanism only within their studied or documented scope.