atomic-design-poc/docs/project/backlog/WP-75-fe-be-seam-closure.md

WP-75 — Close the remaining FE/BE seams

Status: done (6fa27d1) Phase: 12 — DDD hardening

Why

WP-71 added scripts/check-seam.sh guarding one literal pair (the scholing threshold) and documented three further FE/BE duplications that nothing tested across the seam. This closes them — two by deletion, one by a guard, one by an actual fix.

Decisions (pre-made)

1. Dead reference impls get deleted, and CLAUDE.md is amended. This overturns the documented policy that server-owned rules "stay in domain/*.policy.ts as reference impl + unit test". That policy is precisely what kept dead code alive. Blast radius is small: registration.policy.ts is the only *.policy.ts in the repo.
2. Guard the Besluit tag list by extending check-seam.sh, not adding a second script.
3. The phone seam gets a contract test, not a grep check — see below.

Acceptance criteria

• isHerregistratieEligible deleted (uncalled; dead by its own doc-comment) along with isStatusConsistent (also uncalled — WP-71 had added a spec for it the session before). The three live exports (statusLabel, statusColor, herregistratieDeadline) stay, and herregistratieDeadline gained direct coverage it previously only had transitively.
• CLAUDE.md amended: server-owned rules live only on the server; the FE may mirror a server-supplied value (a threshold, a bound) for instant feedback, but never reimplements the algorithm. ADR-0001's matching claim aligned.
• check-seam.sh guards the Besluit tag list, proven to fail when a fourth member is added to the C# enum only, naming both files and both lists. Anchored on the full declaration so it avoids the "greps all matches" trap WP-69 documented.
• Phone contract test added and green; backend stripping fixed.

The phone divergence was real, not latent

WP-71 recorded this as latent because the Angular app normalises before sending — true of that path. The contract test proved the two sides genuinely disagreed: the backend returned 422 for +31612345678 and (06) 12345678, both of which the FE's own parseTelefoonnummer accepts. Any non-Angular client, crafted POST, or future FE change would have hit it.

SubmissionRules.RejectPhoneChange now strips exactly what the FE strips ([\s\-()], then a leading +31 → 0) before applying the shared ^0\d{9}$. The FE value object was not touched — it is the more permissive and correct side.

Why a contract test rather than a grep check: both sides carry the identical ^0\d{9}$ literal, so a drift check would have compared them, found them equal, and reported all clear. The divergence was in the normalisation before the regex — invisible to text comparison. Worth remembering when choosing between the two guard styles: grep checks catch drifting constants, contract tests catch drifting behaviour.

Verification

npm run check:seam    # both checks OK
npm run ci
cd backend && dotnet test BigRegister.slnx --filter "Category!=Integration"

Follow-ups

• Making Besluit flow through the generated client as an enum rather than a string would remove that seam entirely rather than guarding it — a wire change, so not done here.
• The herregistratie-eligibility seam is closed by deletion; if a FE mirror is ever reintroduced, the disjoint-fixture problem returns and would need a contract test, not a grep check.