diff --git a/.dependency-cruiser.base.js b/.dependency-cruiser.base.js
index 93fb3f3..ff945cd 100644
--- a/.dependency-cruiser.base.js
+++ b/.dependency-cruiser.base.js
@@ -109,6 +109,17 @@ module.exports = function buildConfig(contextAllowed, appName, tsConfigFileName)
         },
       },
 
+      {
+        name: 'no-testing-in-production',
+        comment:
+          'Test-only fixture helpers (libs/shared/src/testing/** and any *.testing.ts) are reached from specs/stories only — production code gets its data through the real domain/application doors (ADR-0006), never the test escape hatch.',
+        severity: 'error',
+        from: {
+          pathNot: '\\.(spec|stories)\\.ts$|\\.testing\\.ts$|^libs/shared/src/testing/',
+        },
+        to: { path: '^libs/shared/src/testing/|\\.testing\\.ts$' },
+      },
+
       // --- Hygiene (cheap wins a graph makes obvious) ---
       {
         name: 'no-circular',
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dca53ff..011aab4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -75,10 +75,14 @@ jobs:
         if: needs.changes.outputs.frontend == 'true' && steps.node-modules-cache.outputs.cache-hit != 'true'
       - run: npm run lint
         if: needs.changes.outputs.frontend == 'true'
+      - run: npm run typecheck
+        if: needs.changes.outputs.frontend == 'true'
       - run: npm run format:check
         if: needs.changes.outputs.frontend == 'true'
       - run: npm run check:tokens
         if: needs.changes.outputs.frontend == 'true'
+      - run: npm run check:seam
+        if: needs.changes.outputs.frontend == 'true'
 
   frontend:
     needs: changes
@@ -107,6 +111,9 @@ jobs:
       # Showcase snippets must match their real source regions (WP-39, no drift).
       - run: npm run gen:snippets && git diff --exit-code apps/ssp/src/app/showcase/snippets.generated.ts
         if: needs.changes.outputs.frontend == 'true'
+      # Behaviour spec must match the real test names it's generated from (WP-71, no drift).
+      - run: npm run gen:behaviour-spec && git diff --exit-code libs/shared/docs/behaviour-spec.mdx
+        if: needs.changes.outputs.frontend == 'true'
       # Runs the full suite (both apps + both shared libraries, WP-67) AND reports coverage
       # (WP-46, report-only — no thresholds, so it can't fail on coverage; it still fails on
       # a failing test, like `npm test` did).
diff --git a/apps/behandelportal/src/app/behandeling/domain/besluit.machine.spec.ts b/apps/behandelportal/src/app/behandeling/domain/besluit.machine.spec.ts
index 77a068a..b9d2f09 100644
--- a/apps/behandelportal/src/app/behandeling/domain/besluit.machine.spec.ts
+++ b/apps/behandelportal/src/app/behandeling/domain/besluit.machine.spec.ts
@@ -1,4 +1,5 @@
 import { describe, it, expect } from 'vitest';
+import { expectTag } from '@shared/testing/expect-tag';
 import { BesluitState, reduce, initial } from './besluit.machine';
 
 const editingWith = (besluit: string, toelichting = ''): BesluitState => ({
@@ -10,26 +11,22 @@ const editingWith = (besluit: string, toelichting = ''): BesluitState => ({
 describe('besluit reduce', () => {
   it('SetField updates the draft while editing', () => {
     const s = reduce(initial, { tag: 'SetField', key: 'besluit', value: 'Goedkeuren' });
-    expect(s.tag).toBe('Editing');
-    expect((s as Extract<BesluitState, { tag: 'Editing' }>).draft.besluit).toBe('Goedkeuren');
+    expect(expectTag(s, 'Editing').draft.besluit).toBe('Goedkeuren');
   });
 
   it('Submit with no besluit chosen stays Editing and reports a field error', () => {
     const s = reduce(editingWith(''), { tag: 'Submit' });
-    expect(s.tag).toBe('Editing');
-    expect((s as Extract<BesluitState, { tag: 'Editing' }>).errors.besluit).toBeTruthy();
+    expect(expectTag(s, 'Editing').errors.besluit).toBeTruthy();
   });
 
   it('Submit Afwijzen without a toelichting stays Editing and reports a field error', () => {
     const s = reduce(editingWith('Afwijzen'), { tag: 'Submit' });
-    expect(s.tag).toBe('Editing');
-    expect((s as Extract<BesluitState, { tag: 'Editing' }>).errors.toelichting).toBeTruthy();
+    expect(expectTag(s, 'Editing').errors.toelichting).toBeTruthy();
   });
 
   it('Submit Goedkeuren with no toelichting moves to Submitting (optional there)', () => {
     const s = reduce(editingWith('Goedkeuren'), { tag: 'Submit' });
-    expect(s.tag).toBe('Submitting');
-    expect((s as Extract<BesluitState, { tag: 'Submitting' }>).data).toEqual({
+    expect(expectTag(s, 'Submitting').data).toEqual({
       besluit: 'Goedkeuren',
       toelichting: undefined,
     });
@@ -37,8 +34,7 @@ describe('besluit reduce', () => {
 
   it('Submit Afwijzen with a toelichting moves to Submitting with the trimmed value', () => {
     const s = reduce(editingWith('Afwijzen', '  niet erkend  '), { tag: 'Submit' });
-    expect(s.tag).toBe('Submitting');
-    expect((s as Extract<BesluitState, { tag: 'Submitting' }>).data).toEqual({
+    expect(expectTag(s, 'Submitting').data).toEqual({
       besluit: 'Afwijzen',
       toelichting: 'niet erkend',
     });
diff --git a/apps/ssp/src/app/brief/domain/org-template.machine.spec.ts b/apps/ssp/src/app/brief/domain/org-template.machine.spec.ts
index 24b2604..fb223fa 100644
--- a/apps/ssp/src/app/brief/domain/org-template.machine.spec.ts
+++ b/apps/ssp/src/app/brief/domain/org-template.machine.spec.ts
@@ -1,4 +1,5 @@
 import { describe, it, expect } from 'vitest';
+import { expectTag } from '@shared/testing/expect-tag';
 import { OrgTemplate, OrgTemplateAdminView } from './org-template';
 import { OrgTemplateState, reduce } from './org-template.machine';
 import { DocumentCategory } from '@shared/upload/upload.machine';
@@ -40,9 +41,7 @@ const logoCategory: DocumentCategory = {
 
 describe('org-template.machine', () => {
   it('DraftLoaded moves to loaded with the draft, clean', () => {
-    const s = loaded();
-    expect(s.tag).toBe('loaded');
-    if (s.tag !== 'loaded') return;
+    const s = expectTag(loaded(), 'loaded');
     expect(s.draft.orgName).toBe('CIBG');
     expect(s.subOrgId).toBe('cibg-registers');
     expect(s.unsentBriefs).toBe(2);
@@ -55,33 +54,44 @@ describe('org-template.machine', () => {
   });
 
   it('FieldEdited edits the draft and marks dirty', () => {
-    const s = reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'CIBG Nieuw' });
-    expect(s.tag === 'loaded' && s.draft.orgName).toBe('CIBG Nieuw');
-    expect(s.tag === 'loaded' && s.dirty).toBe(true);
+    const s = expectTag(
+      reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'CIBG Nieuw' }),
+      'loaded',
+    );
+    expect(s.draft.orgName).toBe('CIBG Nieuw');
+    expect(s.dirty).toBe(true);
   });
 
   it('MarginEdited edits one edge and marks dirty', () => {
-    const s = reduce(loaded(), { tag: 'MarginEdited', edge: 'topMm', value: 40 });
-    expect(s.tag === 'loaded' && s.draft.margins.topMm).toBe(40);
-    expect(s.tag === 'loaded' && s.draft.margins.leftMm).toBe(20);
-    expect(s.tag === 'loaded' && s.dirty).toBe(true);
+    const s = expectTag(
+      reduce(loaded(), { tag: 'MarginEdited', edge: 'topMm', value: 40 }),
+      'loaded',
+    );
+    expect(s.draft.margins.topMm).toBe(40);
+    expect(s.draft.margins.leftMm).toBe(20);
+    expect(s.dirty).toBe(true);
   });
 
   it('DraftSaved clears dirty when the saved draft is the current one', () => {
-    const edited = reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'X' });
-    const savedDraft = edited.tag === 'loaded' ? edited.draft : template;
-    const s = reduce(edited, { tag: 'DraftSaved', savedDraft });
-    expect(s.tag === 'loaded' && s.dirty).toBe(false);
-    expect(s.tag === 'loaded' && s.draft.orgName).toBe('X');
+    const edited = expectTag(
+      reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'X' }),
+      'loaded',
+    );
+    const s = expectTag(reduce(edited, { tag: 'DraftSaved', savedDraft: edited.draft }), 'loaded');
+    expect(s.dirty).toBe(false);
+    expect(s.draft.orgName).toBe('X');
   });
 
   it('DraftSaved keeps dirty when an edit landed during the save round-trip', () => {
-    const editing = reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'X' });
-    const savedDraft = editing.tag === 'loaded' ? editing.draft : template;
+    const editing = expectTag(
+      reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'X' }),
+      'loaded',
+    );
+    const savedDraft = editing.draft;
     // a further edit changes the draft reference before the save resolves
     const raced = reduce(editing, { tag: 'FieldEdited', field: 'orgName', value: 'Y' });
-    const s = reduce(raced, { tag: 'DraftSaved', savedDraft });
-    expect(s.tag === 'loaded' && s.dirty).toBe(true);
+    const s = expectTag(reduce(raced, { tag: 'DraftSaved', savedDraft }), 'loaded');
+    expect(s.dirty).toBe(true);
   });
 
   it('edits are no-ops in non-loaded states', () => {
@@ -107,12 +117,15 @@ describe('org-template.machine', () => {
         fileSizeMb: 0.1,
       },
     });
-    const done = reduce(selected, {
-      tag: 'Upload',
-      msg: { type: 'UploadComplete', localId: 'a', documentId: 'doc-1' },
-    });
-    expect(done.tag === 'loaded' && done.draft.logoDocumentId).toBe('doc-1');
-    expect(done.tag === 'loaded' && done.dirty).toBe(true);
+    const done = expectTag(
+      reduce(selected, {
+        tag: 'Upload',
+        msg: { type: 'UploadComplete', localId: 'a', documentId: 'doc-1' },
+      }),
+      'loaded',
+    );
+    expect(done.draft.logoDocumentId).toBe('doc-1');
+    expect(done.dirty).toBe(true);
   });
 
   it('removing the logo clears logoDocumentId + dirty', () => {
@@ -120,12 +133,15 @@ describe('org-template.machine', () => {
       tag: 'Upload',
       msg: { type: 'UploadComplete', localId: 'a', documentId: 'doc-1' },
     });
-    const removed = reduce(withLogo, {
-      tag: 'Upload',
-      msg: { type: 'UploadRemoved', localId: 'a' },
-    });
-    expect(removed.tag === 'loaded' && removed.draft.logoDocumentId).toBeUndefined();
-    expect(removed.tag === 'loaded' && removed.dirty).toBe(true);
+    const removed = expectTag(
+      reduce(withLogo, {
+        tag: 'Upload',
+        msg: { type: 'UploadRemoved', localId: 'a' },
+      }),
+      'loaded',
+    );
+    expect(removed.draft.logoDocumentId).toBeUndefined();
+    expect(removed.dirty).toBe(true);
   });
 
   it('DraftLoaded (sub-org switch) keeps the loaded logo category, drops uploads', () => {
@@ -133,12 +149,15 @@ describe('org-template.machine', () => {
       tag: 'Upload',
       msg: { type: 'CategoriesLoaded', categories: [logoCategory] },
     });
-    const switched = reduce(withCat, {
-      tag: 'DraftLoaded',
-      view: view({ draft: { ...template, subOrgId: 'cibg-vakbekwaamheid' } }),
-    });
-    expect(switched.tag === 'loaded' && switched.upload.categories).toHaveLength(1);
-    expect(switched.tag === 'loaded' && switched.upload.uploads).toHaveLength(0);
-    expect(switched.tag === 'loaded' && switched.subOrgId).toBe('cibg-vakbekwaamheid');
+    const switched = expectTag(
+      reduce(withCat, {
+        tag: 'DraftLoaded',
+        view: view({ draft: { ...template, subOrgId: 'cibg-vakbekwaamheid' } }),
+      }),
+      'loaded',
+    );
+    expect(switched.upload.categories).toHaveLength(1);
+    expect(switched.upload.uploads).toHaveLength(0);
+    expect(switched.subOrgId).toBe('cibg-vakbekwaamheid');
   });
 });
diff --git a/apps/ssp/src/app/herregistratie/domain/herregistratie-has-progress.spec.ts b/apps/ssp/src/app/herregistratie/domain/herregistratie-has-progress.spec.ts
index 74a4156..e271d8f 100644
--- a/apps/ssp/src/app/herregistratie/domain/herregistratie-has-progress.spec.ts
+++ b/apps/ssp/src/app/herregistratie/domain/herregistratie-has-progress.spec.ts
@@ -1,15 +1,27 @@
 import { describe, it, expect } from 'vitest';
-import { hasProgress, initial, WizardState } from './herregistratie.machine';
+import { given } from '@shared/testing/machine';
+import { expectTag } from '@shared/testing/expect-tag';
+import { hasProgress, initial, reduce } from './herregistratie.machine';
 
-const editing = initial as Extract<WizardState, { tag: 'Editing' }>;
+const wizard = given(reduce, initial);
 
 describe('herregistratie hasProgress', () => {
   it('is false for a fresh form', () => {
-    expect(hasProgress(editing)).toBe(false);
+    expect(hasProgress(expectTag(initial, 'Editing'))).toBe(false);
   });
 
   it('is true once a field is filled or the user advances', () => {
-    expect(hasProgress({ ...editing, draft: { uren: '40', jaren: '', punten: '' } })).toBe(true);
-    expect(hasProgress({ ...editing, step: 2 })).toBe(true);
+    const filled = expectTag(wizard({ tag: 'SetField', key: 'uren', value: '40' }), 'Editing');
+    expect(hasProgress(filled)).toBe(true);
+
+    const advanced = expectTag(
+      wizard(
+        { tag: 'SetField', key: 'uren', value: '4160' },
+        { tag: 'SetField', key: 'jaren', value: '5' },
+        { tag: 'Next' },
+      ),
+      'Editing',
+    );
+    expect(hasProgress(advanced)).toBe(true);
   });
 });
diff --git a/apps/ssp/src/app/herregistratie/domain/herregistratie.machine.spec.ts b/apps/ssp/src/app/herregistratie/domain/herregistratie.machine.spec.ts
index 28e1b86..d90f0ad 100644
--- a/apps/ssp/src/app/herregistratie/domain/herregistratie.machine.spec.ts
+++ b/apps/ssp/src/app/herregistratie/domain/herregistratie.machine.spec.ts
@@ -1,6 +1,7 @@
 import { describe, it, expect } from 'vitest';
 import { ok, err } from '@shared/kernel/fp';
 import { given } from '@shared/testing/machine';
+import { expectTag } from '@shared/testing/expect-tag';
 import {
   initial,
   next,
@@ -43,45 +44,56 @@ const toStep3 = (uren: string, punten: string, jaren = '5'): WizardState =>
 describe('wizard.machine', () => {
   it('next advances only when step 1 parses', () => {
     expect(next(initial).tag).toBe('Editing'); // empty uren -> stays, with error
-    expect((next(initial) as any).errors.uren).toBeTruthy();
-    expect((next(toStep1('4160')) as any).step).toBe(2);
+    expect(expectTag(next(initial), 'Editing').errors.uren).toBeTruthy();
+    expect(expectTag(next(toStep1('4160')), 'Editing').step).toBe(2);
   });
 
   it('next advances step 2 → 3 only when punten parses', () => {
-    expect((next(toStep2('4160', 'x')) as any).step).toBe(2); // invalid punten -> stays
-    expect((next(toStep2('4160', 'x')) as any).errors.punten).toBeTruthy();
-    expect((next(toStep2('4160', '200')) as any).step).toBe(3);
+    expect(expectTag(next(toStep2('4160', 'x')), 'Editing').step).toBe(2); // invalid punten -> stays
+    expect(expectTag(next(toStep2('4160', 'x')), 'Editing').errors.punten).toBeTruthy();
+    expect(expectTag(next(toStep2('4160', '200')), 'Editing').step).toBe(3);
   });
 
   it('submit reaches Submitting ONLY from step 3 with fully valid data', () => {
     expect(submit(toStep2('4160', '200')).tag).toBe('Editing'); // not on step 3 -> no Submitting
     expect(submit(toStep3('4160', 'x')).tag).toBe('Editing'); // invalid punten
-    const good = submit(toStep3('4160', '200'));
-    expect(good.tag).toBe('Submitting');
-    expect((good as any).data).toEqual({ uren: 4160, jaren: 5, punten: 200, documents: [] });
+    const good = expectTag(submit(toStep3('4160', '200')), 'Submitting');
+    expect(good.data).toEqual({ uren: 4160, jaren: 5, punten: 200, documents: [] });
   });
 
   it('next requires BOTH step-1 fields (uren and jaren)', () => {
-    expect((next(toStep1('4160', '')) as any).errors.jaren).toBeTruthy(); // jaren empty -> stays
-    expect((next(toStep1('4160', '')) as any).step).toBe(1);
-    expect((next(toStep1('4160', '5')) as any).step).toBe(2); // both valid -> advance
+    expect(expectTag(next(toStep1('4160', '')), 'Editing').errors.jaren).toBeTruthy(); // jaren empty -> stays
+    expect(expectTag(next(toStep1('4160', '')), 'Editing').step).toBe(1);
+    expect(expectTag(next(toStep1('4160', '5')), 'Editing').step).toBe(2); // both valid -> advance
   });
 
   it('back steps down one (3 → 2 → 1) and is a no-op from step 1', () => {
     expect(back(initial)).toBe(initial); // step 1, nothing to go back to
-    expect((back(toStep3('1', '2')) as any).step).toBe(2);
-    expect((back(toStep2('1', '2')) as any).step).toBe(1);
+    expect(expectTag(back(toStep3('1', '2')), 'Editing').step).toBe(2);
+    expect(expectTag(back(toStep2('1', '2')), 'Editing').step).toBe(1);
     expect(resolve(initial, ok(undefined))).toBe(initial); // not Submitting
   });
 
-  it('resolve maps Submitting to Submitted / Failed', () => {
+  it('resolve maps a successful Submitting to Submitted', () => {
+    // Given a wizard mid-submit.
     const submitting = submit(toStep3('4160', '200'));
+
+    // When the submission resolves ok...
+    // Then the wizard reaches Submitted.
     expect(resolve(submitting, ok(undefined)).tag).toBe('Submitted');
+  });
+
+  it('resolve maps a failing Submitting to Failed', () => {
+    // Given a wizard mid-submit.
+    const submitting = submit(toStep3('4160', '200'));
+
+    // When the submission resolves with an error...
+    // Then the wizard reaches Failed.
     expect(resolve(submitting, err('boom')).tag).toBe('Failed');
   });
 
   it('gaNaarStap jumps back to an earlier step, clearing errors', () => {
-    expect((gaNaarStap(toStep3('4160', '200'), 1) as any).step).toBe(1);
+    expect(expectTag(gaNaarStap(toStep3('4160', '200'), 1), 'Editing').step).toBe(1);
   });
 
   it('gaNaarStap ignores a same/forward jump and jumps outside Editing', () => {
@@ -125,14 +137,16 @@ describe('reduce (message-driven)', () => {
     });
     s = reduce(s, { tag: 'Submit' });
     expect(s.tag).toBe('Editing');
-    expect((s as any).errors.documenten).toBeTruthy();
+    expect(expectTag(s, 'Editing').errors.documenten).toBeTruthy();
     s = reduce(s, {
       tag: 'Upload',
       msg: { type: 'DeliveryChannelChanged', categoryId: 'bewijs', channel: 'post' },
     });
     s = reduce(s, { tag: 'Submit' });
     expect(s.tag).toBe('Submitting');
-    expect((s as any).data.documents).toEqual([{ categoryId: 'bewijs', channel: 'post' }]);
+    expect(expectTag(s, 'Submitting').data.documents).toEqual([
+      { categoryId: 'bewijs', channel: 'post' },
+    ]);
   });
 
   it('SubmitFailed then Retry returns to Submitting with the same data', () => {
@@ -143,7 +157,12 @@ describe('reduce (message-driven)', () => {
     expect(s.tag).toBe('Failed');
     s = reduce(s, { tag: 'Retry' });
     expect(s.tag).toBe('Submitting');
-    expect((s as any).data).toEqual({ uren: 4160, jaren: 5, punten: 200, documents: [] });
+    expect(expectTag(s, 'Submitting').data).toEqual({
+      uren: 4160,
+      jaren: 5,
+      punten: 200,
+      documents: [],
+    });
   });
 
   it('Seed mounts an arbitrary state', () => {
diff --git a/apps/ssp/src/app/herregistratie/domain/intake-has-progress.spec.ts b/apps/ssp/src/app/herregistratie/domain/intake-has-progress.spec.ts
index ca0aa6c..0f7efd5 100644
--- a/apps/ssp/src/app/herregistratie/domain/intake-has-progress.spec.ts
+++ b/apps/ssp/src/app/herregistratie/domain/intake-has-progress.spec.ts
@@ -1,15 +1,26 @@
 import { describe, it, expect } from 'vitest';
-import { hasProgress, initial, IntakeState } from './intake.machine';
+import { given } from '@shared/testing/machine';
+import { expectTag } from '@shared/testing/expect-tag';
+import { hasProgress, initial, reduce } from './intake.machine';
 
-const answering = initial as Extract<IntakeState, { tag: 'Answering' }>;
+const intake = given(reduce, initial);
 
 describe('intake hasProgress', () => {
   it('is false for a fresh questionnaire', () => {
-    expect(hasProgress(answering)).toBe(false);
+    expect(hasProgress(expectTag(initial, 'Answering'))).toBe(false);
   });
 
   it('is true once an answer is given or the user advances', () => {
-    expect(hasProgress({ ...answering, answers: { buitenlandGewerkt: 'ja' } })).toBe(true);
-    expect(hasProgress({ ...answering, cursor: 1 })).toBe(true);
+    const answered = expectTag(
+      intake({ tag: 'SetAnswer', key: 'buitenlandGewerkt', value: 'ja' }),
+      'Answering',
+    );
+    expect(hasProgress(answered)).toBe(true);
+
+    const advanced = expectTag(
+      intake({ tag: 'SetAnswer', key: 'buitenlandGewerkt', value: 'nee' }, { tag: 'Next' }),
+      'Answering',
+    );
+    expect(hasProgress(advanced)).toBe(true);
   });
 });
diff --git a/apps/ssp/src/app/herregistratie/domain/intake.machine.spec.ts b/apps/ssp/src/app/herregistratie/domain/intake.machine.spec.ts
index 86c4be9..a248ce7 100644
--- a/apps/ssp/src/app/herregistratie/domain/intake.machine.spec.ts
+++ b/apps/ssp/src/app/herregistratie/domain/intake.machine.spec.ts
@@ -1,5 +1,6 @@
 import { describe, it, expect } from 'vitest';
 import { ok, err } from '@shared/kernel/fp';
+import { expectTag } from '@shared/testing/expect-tag';
 import {
   Answers,
   initial,
@@ -31,9 +32,11 @@ describe('STEPS (fixed) and inline questions', () => {
   it('reveals the buitenland detail questions inline only when worked abroad', () => {
     // No new step; instead these fields become required within the buitenland step.
     expect(next(answering({ buitenlandGewerkt: 'ja' })).tag).toBe('Answering'); // land/uren missing -> blocked
-    expect((next(answering({ buitenlandGewerkt: 'ja' })) as any).errors.land).toBeTruthy();
+    expect(
+      expectTag(next(answering({ buitenlandGewerkt: 'ja' })), 'Answering').errors.land,
+    ).toBeTruthy();
     expect(next(answering({ buitenlandGewerkt: 'nee' })).tag).toBe('Answering'); // valid, advances (cursor moves)
-    expect((next(answering({ buitenlandGewerkt: 'nee' })) as any).cursor).toBe(1);
+    expect(expectTag(next(answering({ buitenlandGewerkt: 'nee' })), 'Answering').cursor).toBe(1);
   });
 
   it('reveals the scholing question only when NL-hours are below the threshold', () => {
@@ -50,31 +53,33 @@ describe('STEPS (fixed) and inline questions', () => {
       answering({ buitenlandGewerkt: 'nee', uren: '1500', punten: '200' }, 0, 2000),
     );
     expect(lowThreshold.tag).toBe('Answering'); // scholing now required (1500 < 2000), unanswered → blocked
-    expect((lowThreshold as any).errors.scholingGevolgd).toBeTruthy();
+    expect(expectTag(lowThreshold, 'Answering').errors.scholingGevolgd).toBeTruthy();
   });
 });
 
 describe('navigation', () => {
   it('Next is a no-op (sets an error) when the current step is invalid', () => {
-    const s = next(initial); // buitenland unanswered
-    expect(s.tag).toBe('Answering');
-    expect((s as any).cursor).toBe(0);
-    expect((s as any).errors.buitenlandGewerkt).toBeTruthy();
+    const s = expectTag(next(initial), 'Answering'); // buitenland unanswered
+    expect(s.cursor).toBe(0);
+    expect(s.errors.buitenlandGewerkt).toBeTruthy();
   });
 
   it('Next advances once the step is valid', () => {
-    const s = next(answering({ buitenlandGewerkt: 'nee' }));
-    expect((s as any).cursor).toBe(1);
-    expect(currentStep(s as any)).toBe('werk');
+    const s = expectTag(next(answering({ buitenlandGewerkt: 'nee' })), 'Answering');
+    expect(s.cursor).toBe(1);
+    expect(currentStep(s)).toBe('werk');
   });
 
   it('editing an answer leaves the cursor fixed (steps never collapse)', () => {
-    const edited = reduce(answering({ buitenlandGewerkt: 'ja' }, 1), {
-      tag: 'SetAnswer',
-      key: 'buitenlandGewerkt',
-      value: 'nee',
-    });
-    expect((edited as any).cursor).toBe(1); // cursor untouched; only inline questions change
+    const edited = expectTag(
+      reduce(answering({ buitenlandGewerkt: 'ja' }, 1), {
+        tag: 'SetAnswer',
+        key: 'buitenlandGewerkt',
+        value: 'nee',
+      }),
+      'Answering',
+    );
+    expect(edited.cursor).toBe(1); // cursor untouched; only inline questions change
   });
 
   it('Back never goes below the first step', () => {
@@ -83,7 +88,7 @@ describe('navigation', () => {
 
   it('gaNaarStap jumps back to an earlier step, clearing errors', () => {
     const s = answering({ buitenlandGewerkt: 'nee' }, 2);
-    expect((gaNaarStap(s, 0) as any).cursor).toBe(0);
+    expect(expectTag(gaNaarStap(s, 0), 'Answering').cursor).toBe(0);
   });
 
   it('gaNaarStap ignores a same/forward jump and jumps outside Answering', () => {
@@ -106,19 +111,18 @@ describe('submit', () => {
         answering({ buitenlandGewerkt: 'nee', uren: '500', scholingGevolgd: 'ja', punten: 'x' }),
       ).tag,
     ).toBe('Answering');
-    const good = submit(answering(complete));
-    expect(good.tag).toBe('Submitting');
-    expect((good as any).data.uren).toBe(4160);
-    expect((good as any).data.punten).toBeUndefined(); // not collected without scholing
+    const good = expectTag(submit(answering(complete)), 'Submitting');
+    expect(good.data.uren).toBe(4160);
+    expect(good.data.punten).toBeUndefined(); // not collected without scholing
   });
 
   it('punten is required only when aanvullende scholing was gevolgd', () => {
     // scholing = ja but punten missing -> blocked on punten.
-    const missing = submit(
-      answering({ buitenlandGewerkt: 'nee', uren: '500', scholingGevolgd: 'ja' }),
+    const missing = expectTag(
+      submit(answering({ buitenlandGewerkt: 'nee', uren: '500', scholingGevolgd: 'ja' })),
+      'Answering',
     );
-    expect(missing.tag).toBe('Answering');
-    expect((missing as any).errors.punten).toBeTruthy();
+    expect(missing.errors.punten).toBeTruthy();
     // scholing = nee -> punten not required, submits without it.
     expect(
       submit(answering({ buitenlandGewerkt: 'nee', uren: '500', scholingGevolgd: 'nee' })).tag,
@@ -128,12 +132,14 @@ describe('submit', () => {
   it('low hours requires the scholing answer before submit', () => {
     const noScholing = submit(answering({ buitenlandGewerkt: 'nee', uren: '500' }));
     expect(noScholing.tag).toBe('Answering'); // scholing question is required, unanswered
-    const withScholing = submit(
-      answering({ buitenlandGewerkt: 'nee', uren: '500', scholingGevolgd: 'ja', punten: '200' }),
+    const withScholing = expectTag(
+      submit(
+        answering({ buitenlandGewerkt: 'nee', uren: '500', scholingGevolgd: 'ja', punten: '200' }),
+      ),
+      'Submitting',
     );
-    expect(withScholing.tag).toBe('Submitting');
-    expect((withScholing as any).data.aanvullendeScholing).toBe(true);
-    expect((withScholing as any).data.punten).toBe(200);
+    expect(withScholing.data.aanvullendeScholing).toBe(true);
+    expect(withScholing.data.punten).toBe(200);
   });
 
   it('resolve maps Submitting to Submitted on a successful submit', () => {
@@ -155,12 +161,12 @@ describe('reduce (message-driven happy path)', () => {
     s = reduce(s, { tag: 'SetAnswer', key: 'land', value: 'België' });
     s = reduce(s, { tag: 'SetAnswer', key: 'buitenlandseUren', value: '800' });
     s = reduce(s, { tag: 'Next' });
-    expect(currentStep(s as any)).toBe('werk');
+    expect(currentStep(expectTag(s, 'Answering'))).toBe('werk');
     // Step 2: werk — uren + punten (no inline scholing, hours are high).
     s = reduce(s, { tag: 'SetAnswer', key: 'uren', value: '4160' });
     s = reduce(s, { tag: 'SetAnswer', key: 'punten', value: '200' });
     s = reduce(s, { tag: 'Next' });
-    expect(currentStep(s as any)).toBe('review');
+    expect(currentStep(expectTag(s, 'Answering'))).toBe('review');
     s = reduce(s, { tag: 'Submit' });
     expect(s.tag).toBe('Submitting');
     s = reduce(s, { tag: 'SubmitConfirmed' });
diff --git a/apps/ssp/src/app/registratie/domain/aanvraag-view.spec.ts b/apps/ssp/src/app/registratie/domain/aanvraag-view.spec.ts
index 8a7d3e9..17a3234 100644
--- a/apps/ssp/src/app/registratie/domain/aanvraag-view.spec.ts
+++ b/apps/ssp/src/app/registratie/domain/aanvraag-view.spec.ts
@@ -2,9 +2,9 @@ import { describe, it, expect } from 'vitest';
 import { submittedRow, detailRows, purposeLabel, statusLabel, TYPE_LABELS } from './aanvraag-view';
 import { Aanvraag } from './aanvraag';
 
-const base = {
+const base: Omit<Aanvraag, 'status'> = {
   id: '1',
-  type: 'herregistratie' as const,
+  type: 'herregistratie',
   documentIds: [],
   createdAt: '',
   updatedAt: '',
@@ -13,19 +13,27 @@ const base = {
 
 describe('submittedRow', () => {
   it('heading is the type, subtitle is the purpose', () => {
+    // Given a submitted herregistratie aanvraag.
+    // When its row is derived...
     const row = submittedRow({
       ...base,
       status: { tag: 'InBehandeling', referentie: 'R1', manual: false },
-    } as Aanvraag);
+    });
+    // Then the heading/subtitle come from the same label functions the view uses —
+    // never a hardcoded Dutch literal here.
     expect(row.heading).toBe(TYPE_LABELS.herregistratie);
     expect(row.subtitle).toBe(purposeLabel('herregistratie'));
   });
 
   it('status line carries the status label, reference and submit date', () => {
+    // Given an aanvraag InBehandeling, submitted 2024-05-12, referentie R1.
+    // When its row is derived...
     const row = submittedRow({
       ...base,
       status: { tag: 'InBehandeling', referentie: 'R1', manual: false },
-    } as Aanvraag);
+    });
+    // Then the status line contains the label (via statusLabel(), not a literal),
+    // the reference, and the formatted submit date.
     expect(row.status).toContain(
       statusLabel({ tag: 'InBehandeling', referentie: 'R1', manual: false }),
     );
@@ -33,35 +41,58 @@ describe('submittedRow', () => {
     expect(row.status).toContain('12 mei 2024');
   });
 
-  it('manual review adds a note; rejection adds its reason', () => {
+  it('manual review adds a note', () => {
+    // Given an aanvraag InBehandeling with manual review flagged.
+    // When its row is derived...
     const manual = submittedRow({
       ...base,
       status: { tag: 'InBehandeling', referentie: 'R1', manual: true },
-    } as Aanvraag);
+    });
+    // Then the status line notes the manual review.
     expect(manual.status).toContain('handmatig');
+  });
+
+  // `reden` (rejection.status.reden / meerInfo.status.reden) is raw domain data — a
+  // free-text field (`Aanvraag`'s status union types it `string`, not an enum), passed
+  // through `submittedRow` unchanged and unwrapped by `$localize`. There is no
+  // reason-code/tag backing it to assert on instead: the value under test IS the exact
+  // string the Given supplied, so asserting it reappears in the Then is checking
+  // pass-through, not translated copy.
+  it('rejection adds its reason', () => {
+    // Given a rejected aanvraag with a rejection reason.
+    // When its row is derived...
     const rejected = submittedRow({
       ...base,
       status: { tag: 'Afgewezen', referentie: 'R2', reden: 'Onvoldoende uren' },
-    } as Aanvraag);
+    });
+    // Then the reason passes through into the status line unchanged.
     expect(rejected.status).toContain('Onvoldoende uren');
   });
 
   it('meer-info-gevraagd adds its reason, like a rejection', () => {
+    // Given an aanvraag with more information requested, with a reason.
+    // When its row is derived...
     const row = submittedRow({
       ...base,
       status: { tag: 'MeerInfoGevraagd', referentie: 'R3', reden: 'Diploma ontbreekt' },
-    } as Aanvraag);
+    });
+    // Then the reason passes through into the status line unchanged (see note above).
     expect(row.status).toContain('Diploma ontbreekt');
   });
 });
 
 describe('detailRows', () => {
   it('lists soort/waarvoor/status/referentie/ingediend, plus reason when rejected', () => {
+    // Given a rejected aanvraag with a rejection reason.
+    // When its detail rows are derived...
     const rows = detailRows({
       ...base,
       status: { tag: 'Afgewezen', referentie: 'R2', reden: 'Onvoldoende uren' },
-    } as Aanvraag);
+    });
     const values = rows.map((r) => r.value);
+
+    // Then the type label (via TYPE_LABELS, not a literal), the reference, and the
+    // reason (raw pass-through, see note above) all appear, and a reason row is added.
     expect(values).toContain(TYPE_LABELS.herregistratie);
     expect(values).toContain('R2');
     expect(values).toContain('Onvoldoende uren');
@@ -69,11 +100,15 @@ describe('detailRows', () => {
   });
 
   it('reference falls back to em dash for a Concept', () => {
+    // Given a Concept (not yet submitted, no reference assigned).
+    // When its detail rows are derived...
     const rows = detailRows({
       ...base,
       submittedAt: undefined,
       status: { tag: 'Concept', stepIndex: 0, stepCount: 3 },
-    } as Aanvraag);
+    });
+
+    // Then the reference row falls back to an em dash, and no reason row is added.
     const ref = rows.find((r) => r.value === '—');
     expect(ref).toBeTruthy();
     expect(rows.length).toBe(5);
diff --git a/apps/ssp/src/app/registratie/domain/change-request.machine.spec.ts b/apps/ssp/src/app/registratie/domain/change-request.machine.spec.ts
index 0081d0a..69f2e77 100644
--- a/apps/ssp/src/app/registratie/domain/change-request.machine.spec.ts
+++ b/apps/ssp/src/app/registratie/domain/change-request.machine.spec.ts
@@ -1,5 +1,6 @@
 import { describe, it, expect } from 'vitest';
 import { given } from '@shared/testing/machine';
+import { expectTag } from '@shared/testing/expect-tag';
 import { ChangeRequestState, reduce, initial } from './change-request.machine';
 
 const givenChangeRequest = given(reduce, initial);
@@ -10,25 +11,17 @@ const editingWith = (telefoon: string): ChangeRequestState =>
 describe('change-request reduce', () => {
   it('SetField updates the draft while editing', () => {
     const s = reduce(initial, { tag: 'SetField', key: 'telefoon', value: '0612345678' });
-    expect(s.tag).toBe('Editing');
-    expect((s as Extract<ChangeRequestState, { tag: 'Editing' }>).draft.telefoon).toBe(
-      '0612345678',
-    );
+    expect(expectTag(s, 'Editing').draft.telefoon).toBe('0612345678');
   });
 
   it('Submit with an invalid draft stays Editing and reports field errors', () => {
     const s = reduce(editingWith('nope'), { tag: 'Submit' });
-    expect(s.tag).toBe('Editing');
-    const errors = (s as Extract<ChangeRequestState, { tag: 'Editing' }>).errors;
-    expect(errors.telefoon).toBeTruthy();
+    expect(expectTag(s, 'Editing').errors.telefoon).toBeTruthy();
   });
 
   it('Submit with a valid draft moves to Submitting with parsed (normalised) data', () => {
     const s = reduce(editingWith('06 12 34 56 78'), { tag: 'Submit' });
-    expect(s.tag).toBe('Submitting');
-    expect((s as Extract<ChangeRequestState, { tag: 'Submitting' }>).data.telefoon).toBe(
-      '0612345678',
-    );
+    expect(expectTag(s, 'Submitting').data.telefoon).toBe('0612345678');
   });
 
   it('SubmitConfirmed maps Submitting to Submitted with the referentie', () => {
diff --git a/apps/ssp/src/app/registratie/domain/has-progress.spec.ts b/apps/ssp/src/app/registratie/domain/has-progress.spec.ts
index ba51809..f968b60 100644
--- a/apps/ssp/src/app/registratie/domain/has-progress.spec.ts
+++ b/apps/ssp/src/app/registratie/domain/has-progress.spec.ts
@@ -1,34 +1,51 @@
 import { describe, it, expect } from 'vitest';
-import { hasProgress, initial, RegistratieState } from './registratie-wizard.machine';
+import { given } from '@shared/testing/machine';
+import { expectTag } from '@shared/testing/expect-tag';
+import { hasProgress, initial, reduce } from './registratie-wizard.machine';
 
-const invullen = (over: Partial<Extract<RegistratieState, { tag: 'Invullen' }>>) => ({
-  ...(initial as Extract<RegistratieState, { tag: 'Invullen' }>),
-  ...over,
-});
+const wizard = given(reduce, initial);
 
 describe('hasProgress', () => {
   it('is false for a fresh wizard', () => {
-    expect(hasProgress(initial as Extract<RegistratieState, { tag: 'Invullen' }>)).toBe(false);
+    expect(hasProgress(expectTag(initial, 'Invullen'))).toBe(false);
   });
 
   it('ignores an auto-prefilled BRP address at step 0', () => {
-    const s = invullen({
-      draft: {
+    const s = expectTag(
+      wizard({
+        tag: 'PrefillAdres',
         straat: 'Lange Voorhout 9',
         postcode: '2514 EA',
         woonplaats: 'Den Haag',
-        adresHerkomst: 'brp',
-        antwoorden: {},
-      },
-    });
+      }),
+      'Invullen',
+    );
     expect(hasProgress(s)).toBe(false);
   });
 
   it('is true once the user advances, picks correspondence/diploma, or is past step 0', () => {
-    expect(hasProgress(invullen({ cursor: 1 }))).toBe(true);
-    expect(hasProgress(invullen({ draft: { correspondentie: 'post', antwoorden: {} } }))).toBe(
-      true,
+    const advanced = expectTag(
+      wizard(
+        { tag: 'SetField', key: 'straat', value: 'Lange Voorhout 9' },
+        { tag: 'SetField', key: 'postcode', value: '2514 EA' },
+        { tag: 'SetField', key: 'woonplaats', value: 'Den Haag' },
+        { tag: 'SetCorrespondentie', value: 'post' },
+        { tag: 'Next' },
+      ),
+      'Invullen',
     );
-    expect(hasProgress(invullen({ draft: { diplomaId: 'd1', antwoorden: {} } }))).toBe(true);
+    expect(hasProgress(advanced)).toBe(true);
+
+    const withCorrespondentie = expectTag(
+      wizard({ tag: 'SetCorrespondentie', value: 'post' }),
+      'Invullen',
+    );
+    expect(hasProgress(withCorrespondentie)).toBe(true);
+
+    const withDiploma = expectTag(
+      wizard({ tag: 'KiesDiploma', diplomaId: 'd1', beroep: 'Arts', vraagIds: [] }),
+      'Invullen',
+    );
+    expect(hasProgress(withDiploma)).toBe(true);
   });
 });
diff --git a/apps/ssp/src/app/registratie/domain/registratie-wizard.machine.spec.ts b/apps/ssp/src/app/registratie/domain/registratie-wizard.machine.spec.ts
index a7a2209..695b314 100644
--- a/apps/ssp/src/app/registratie/domain/registratie-wizard.machine.spec.ts
+++ b/apps/ssp/src/app/registratie/domain/registratie-wizard.machine.spec.ts
@@ -1,6 +1,7 @@
 import { describe, it, expect } from 'vitest';
 import { ok, err } from '@shared/kernel/fp';
 import { initialUpload } from '@shared/upload/upload.machine';
+import { expectTag } from '@shared/testing/expect-tag';
 import {
   Draft,
   RegistratieState,
@@ -51,69 +52,75 @@ describe('STEPS (fixed)', () => {
 
 describe('navigation', () => {
   it('Next is a no-op (sets errors) when the adres step is invalid', () => {
-    const s = next(initial);
+    const s = expectTag(next(initial), 'Invullen');
     expect(s.tag).toBe('Invullen');
-    expect((s as any).cursor).toBe(0);
-    expect((s as any).errors.straat).toBeTruthy();
-    expect((s as any).errors.correspondentie).toBeTruthy();
+    expect(s.cursor).toBe(0);
+    expect(s.errors.straat).toBeTruthy();
+    expect(s.errors.correspondentie).toBeTruthy();
   });
 
   it('Next advances once the adres step is valid', () => {
-    const s = next(invullen(validAdres));
-    expect((s as any).cursor).toBe(1);
-    expect(currentStep(s as any)).toBe('beroep');
+    const s = expectTag(next(invullen(validAdres)), 'Invullen');
+    expect(s.cursor).toBe(1);
+    expect(currentStep(s)).toBe('beroep');
   });
 
   it('requires a valid e-mail only when the channel is email', () => {
-    const bad = next(invullen({ ...validAdres, correspondentie: 'email' }));
-    expect((bad as any).errors.email).toBeTruthy();
-    const good = next(invullen({ ...validAdres, correspondentie: 'email', email: 'a@b.nl' }));
-    expect((good as any).cursor).toBe(1);
+    const bad = expectTag(next(invullen({ ...validAdres, correspondentie: 'email' })), 'Invullen');
+    expect(bad.errors.email).toBeTruthy();
+    const good = expectTag(
+      next(invullen({ ...validAdres, correspondentie: 'email', email: 'a@b.nl' })),
+      'Invullen',
+    );
+    expect(good.cursor).toBe(1);
   });
 
   it('beroep step requires a chosen diploma', () => {
-    const noDiploma = next(invullen(validAdres, 1));
-    expect((noDiploma as any).cursor).toBe(1);
-    expect((noDiploma as any).errors.diploma).toBeTruthy();
-    const withDiploma = next(invullen(validDraft, 1));
-    expect((withDiploma as any).cursor).toBe(2);
+    const noDiploma = expectTag(next(invullen(validAdres, 1)), 'Invullen');
+    expect(noDiploma.cursor).toBe(1);
+    expect(noDiploma.errors.diploma).toBeTruthy();
+    const withDiploma = expectTag(next(invullen(validDraft, 1)), 'Invullen');
+    expect(withDiploma.cursor).toBe(2);
   });
 
   it('Back never goes below the first step and preserves the draft', () => {
     expect(back(initial)).toBe(initial);
-    const s = back(invullen(validDraft, 2));
-    expect((s as any).cursor).toBe(1);
-    expect((s as any).draft.beroep).toBe('Arts');
+    const s = expectTag(back(invullen(validDraft, 2)), 'Invullen');
+    expect(s.cursor).toBe(1);
+    expect(s.draft.beroep).toBe('Arts');
   });
 
   it('GaNaarStap only jumps backwards', () => {
-    expect((gaNaarStap(invullen(validDraft, 2), 0) as any).cursor).toBe(0);
-    expect((gaNaarStap(invullen(validDraft, 1), 2) as any).cursor).toBe(1); // forward jump rejected
+    expect(expectTag(gaNaarStap(invullen(validDraft, 2), 0), 'Invullen').cursor).toBe(0);
+    expect(expectTag(gaNaarStap(invullen(validDraft, 1), 2), 'Invullen').cursor).toBe(1); // forward jump rejected
   });
 });
 
 describe('adres origin (BRP vs handmatig)', () => {
   it('prefillAdres flags origin brp', () => {
-    const s = prefillAdres(invullen({}), 'Lange Voorhout 9', '2514 EA', 'Den Haag');
-    expect((s as any).draft.adresHerkomst).toBe('brp');
-    expect((s as any).draft.straat).toBe('Lange Voorhout 9');
+    const s = expectTag(
+      prefillAdres(invullen({}), 'Lange Voorhout 9', '2514 EA', 'Den Haag'),
+      'Invullen',
+    );
+    expect(s.draft.adresHerkomst).toBe('brp');
+    expect(s.draft.straat).toBe('Lange Voorhout 9');
   });
 
   it('editing a prefilled address field flips origin to handmatig', () => {
     const prefilled = prefillAdres(invullen({}), 'Lange Voorhout 9', '2514 EA', 'Den Haag');
-    const edited = setField(prefilled, 'woonplaats', 'Rotterdam');
-    expect((edited as any).draft.adresHerkomst).toBe('handmatig');
+    const edited = expectTag(setField(prefilled, 'woonplaats', 'Rotterdam'), 'Invullen');
+    expect(edited.draft.adresHerkomst).toBe('handmatig');
   });
 
   it('typing an address with no BRP prefill yields handmatig', () => {
-    const s = setField(invullen({}), 'straat', 'Kerkstraat 1');
-    expect((s as any).draft.adresHerkomst).toBe('handmatig');
+    const s = expectTag(setField(invullen({}), 'straat', 'Kerkstraat 1'), 'Invullen');
+    expect(s.draft.adresHerkomst).toBe('handmatig');
   });
 
   it('editing the e-mail field does not change the address origin', () => {
     const prefilled = prefillAdres(invullen({}), 'Lange Voorhout 9', '2514 EA', 'Den Haag');
-    const edited = setField(prefilled, 'email', 'a@b.nl');
-    expect((edited as any).draft.adresHerkomst).toBe('brp');
+    const edited = expectTag(setField(prefilled, 'email', 'a@b.nl'), 'Invullen');
+    expect(edited.draft.adresHerkomst).toBe('brp');
   });
 
   it('a manually entered address still submits (only manual diploma is gated)', () => {
@@ -129,37 +136,36 @@ describe('adres origin (BRP vs handmatig)', () => {
         diplomaHerkomst: 'duo',
       }),
     );
-    expect(s.tag).toBe('Indienen');
-    expect((s as any).data.adresHerkomst).toBe('handmatig');
+    const indienen = expectTag(s, 'Indienen');
+    expect(indienen.data.adresHerkomst).toBe('handmatig');
   });
 });
 
 describe('kiesDiploma', () => {
   it('derives the beroep from the chosen diploma and flags origin duo', () => {
-    const s = kiesDiploma(invullen({}), 'd9', 'Verpleegkundige', []);
-    expect((s as any).draft.diplomaId).toBe('d9');
-    expect((s as any).draft.beroep).toBe('Verpleegkundige');
-    expect((s as any).draft.diplomaHerkomst).toBe('duo');
+    const s = expectTag(kiesDiploma(invullen({}), 'd9', 'Verpleegkundige', []), 'Invullen');
+    expect(s.draft.diplomaId).toBe('d9');
+    expect(s.draft.beroep).toBe('Verpleegkundige');
+    expect(s.draft.diplomaHerkomst).toBe('duo');
   });
 });
 
 describe('policy questions (geldigheidsvragen)', () => {
   it('a diploma with questions blocks Next until they are answered', () => {
     let s = kiesDiploma(invullen(validAdres, 1), 'd2', 'Arts', ['nl-taalvaardigheid']);
-    const blocked = next(s);
-    expect((blocked as any).cursor).toBe(1);
-    expect((blocked as any).errors.antwoorden['nl-taalvaardigheid']).toBeTruthy();
+    const blocked = expectTag(next(s), 'Invullen');
+    expect(blocked.cursor).toBe(1);
+    expect(blocked.errors.antwoorden?.['nl-taalvaardigheid']).toBeTruthy();
     s = setAntwoord(s, 'nl-taalvaardigheid', 'ja');
-    expect((next(s) as any).cursor).toBe(2);
+    expect(expectTag(next(s), 'Invullen').cursor).toBe(2);
   });
 
   it('validateAll keeps only the answers to the questions that applied', () => {
     let s = kiesDiploma(invullen(validAdres, 2), 'd2', 'Arts', ['nl-taalvaardigheid']);
     s = setAntwoord(s, 'nl-taalvaardigheid', 'ja');
     s = setAntwoord(s, 'stale', 'x'); // not in vraagIds
-    const done = submit(s);
-    expect(done.tag).toBe('Indienen');
-    expect((done as any).data.antwoorden).toEqual({ 'nl-taalvaardigheid': 'ja' });
+    const done = expectTag(submit(s), 'Indienen');
+    expect(done.data.antwoorden).toEqual({ 'nl-taalvaardigheid': 'ja' });
   });
 });
 
@@ -167,10 +173,10 @@ describe('manual diploma fallback', () => {
   const maxIds = ['nl-taalvaardigheid', 'diploma-erkend', 'toelichting'];
 
   it('KiesHandmatig flags handmatig with the maximal question set and no beroep yet', () => {
-    const s = kiesHandmatig(invullen(validAdres, 1), maxIds);
-    expect((s as any).draft.diplomaHerkomst).toBe('handmatig');
-    expect((s as any).draft.beroep).toBeUndefined();
-    expect((s as any).draft.vraagIds).toEqual(maxIds);
+    const s = expectTag(kiesHandmatig(invullen(validAdres, 1), maxIds), 'Invullen');
+    expect(s.draft.diplomaHerkomst).toBe('handmatig');
+    expect(s.draft.beroep).toBeUndefined();
+    expect(s.draft.vraagIds).toEqual(maxIds);
   });
 
   it('requires a declared beroep + all maximal questions before submit', () => {
@@ -179,10 +185,9 @@ describe('manual diploma fallback', () => {
     s = declareerBeroep(s, 'Fysiotherapeut');
     expect(submit(s).tag).toBe('Invullen'); // questions unanswered
     for (const id of maxIds) s = setAntwoord(s, id, 'ja');
-    const done = submit(s);
-    expect(done.tag).toBe('Indienen');
-    expect((done as any).data.diplomaHerkomst).toBe('handmatig');
-    expect((done as any).data.beroep).toBe('Fysiotherapeut');
+    const done = expectTag(submit(s), 'Indienen');
+    expect(done.data.diplomaHerkomst).toBe('handmatig');
+    expect(done.data.beroep).toBe('Fysiotherapeut');
   });
 });
 
@@ -192,17 +197,18 @@ describe('submit', () => {
   });
 
   it('reaches Indienen with a complete, valid draft, carrying its data', () => {
-    const good = submit(invullen(validDraft));
-    expect(good.tag).toBe('Indienen');
-    expect((good as any).data.beroep).toBe('Arts');
-    expect((good as any).data.adres.postcode).toBe('2514 EA');
-    expect((good as any).data.adresHerkomst).toBe('brp');
+    const good = expectTag(submit(invullen(validDraft)), 'Indienen');
+    expect(good.data.beroep).toBe('Arts');
+    expect(good.data.adres.postcode).toBe('2514 EA');
+    expect(good.data.adresHerkomst).toBe('brp');
   });
 
   it('resolve maps Indienen to Ingediend with the referentie', () => {
-    const ingediend = resolve(submit(invullen(validDraft)), ok('BIG-2026-001'));
-    expect(ingediend.tag).toBe('Ingediend');
-    expect((ingediend as any).referentie).toBe('BIG-2026-001');
+    const ingediend = expectTag(
+      resolve(submit(invullen(validDraft)), ok('BIG-2026-001')),
+      'Ingediend',
+    );
+    expect(ingediend.referentie).toBe('BIG-2026-001');
   });
 
   it('resolve maps Indienen to Mislukt on a failed submit', () => {
@@ -211,7 +217,10 @@ describe('submit', () => {
 });
 
 describe('reduce (message-driven happy path)', () => {
-  it('drives the full flow via messages', () => {
+  // Each helper replays real messages through the real reducer up to the named
+  // point — no hand-assembled state literal — so each test below Givens its own
+  // starting point independently, one transition at a time.
+  const toBeroepStep = (): RegistratieState => {
     let s: RegistratieState = initial;
     s = reduce(s, {
       tag: 'PrefillAdres',
@@ -220,14 +229,52 @@ describe('reduce (message-driven happy path)', () => {
       woonplaats: 'Den Haag',
     });
     s = reduce(s, { tag: 'SetCorrespondentie', value: 'post' });
-    s = reduce(s, { tag: 'Next' });
-    expect(currentStep(s as any)).toBe('beroep');
-    s = reduce(s, { tag: 'KiesDiploma', diplomaId: 'd1', beroep: 'Arts', vraagIds: [] });
-    s = reduce(s, { tag: 'Next' });
-    expect(currentStep(s as any)).toBe('controle');
-    s = reduce(s, { tag: 'Submit' });
+    return reduce(s, { tag: 'Next' });
+  };
+  const toControleStep = (): RegistratieState => {
+    const s = reduce(toBeroepStep(), {
+      tag: 'KiesDiploma',
+      diplomaId: 'd1',
+      beroep: 'Arts',
+      vraagIds: [],
+    });
+    return reduce(s, { tag: 'Next' });
+  };
+  const toIndienen = (): RegistratieState => reduce(toControleStep(), { tag: 'Submit' });
+
+  it('adres and correspondentie set, Next advances from adres to beroep', () => {
+    // Given the initial wizard.
+    // When the adres is prefilled, correspondentie chosen, and Next dispatched...
+    const s = toBeroepStep();
+
+    // Then the wizard advances to the beroep step.
+    expect(currentStep(expectTag(s, 'Invullen'))).toBe('beroep');
+  });
+
+  it('diploma chosen, Next advances from beroep to controle', () => {
+    // Given a wizard on the beroep step.
+    // When a diploma is chosen and Next dispatched...
+    const s = toControleStep();
+
+    // Then the wizard advances to the controle step.
+    expect(currentStep(expectTag(s, 'Invullen'))).toBe('controle');
+  });
+
+  it('Submit moves a complete Invullen draft to Indienen', () => {
+    // Given a wizard on the controle step with a complete, valid draft.
+    // When Submit is dispatched...
+    const s = toIndienen();
+
+    // Then the wizard moves to Indienen.
     expect(s.tag).toBe('Indienen');
-    s = reduce(s, { tag: 'SubmitConfirmed', referentie: 'BIG-2026-001' });
+  });
+
+  it('SubmitConfirmed moves Indienen to Ingediend', () => {
+    // Given a wizard mid-submit (Indienen).
+    // When SubmitConfirmed arrives with a referentie...
+    const s = reduce(toIndienen(), { tag: 'SubmitConfirmed', referentie: 'BIG-2026-001' });
+
+    // Then the wizard reaches Ingediend.
     expect(s.tag).toBe('Ingediend');
   });
 
@@ -244,9 +291,8 @@ describe('reduce (message-driven happy path)', () => {
       tag: 'SubmitFailed',
       error: 'boom',
     });
-    const s = reduce(mislukt, { tag: 'Retry' });
-    expect(s.tag).toBe('Indienen');
-    expect((s as any).data.beroep).toBe('Arts');
+    const s = expectTag(reduce(mislukt, { tag: 'Retry' }), 'Indienen');
+    expect(s.data.beroep).toBe('Arts');
   });
 });
 
@@ -263,11 +309,14 @@ describe('inline document upload (beroep step)', () => {
   };
 
   it('routes Upload messages through the upload reducer', () => {
-    const s = reduce(invullen(validDraft), {
-      tag: 'Upload',
-      msg: { type: 'CategoriesLoaded', categories: [cat] },
-    });
-    expect((s as any).upload.categories).toHaveLength(1);
+    const s = expectTag(
+      reduce(invullen(validDraft), {
+        tag: 'Upload',
+        msg: { type: 'CategoriesLoaded', categories: [cat] },
+      }),
+      'Invullen',
+    );
+    expect(s.upload.categories).toHaveLength(1);
   });
 
   it('blocks the beroep step until a required category is satisfied', () => {
@@ -276,15 +325,17 @@ describe('inline document upload (beroep step)', () => {
       msg: { type: 'CategoriesLoaded', categories: [cat] },
     });
     s = reduce(s, { tag: 'Next' }); // beroep → controle blocked
-    expect(currentStep(s as any)).toBe('beroep');
-    expect((s as any).errors.documenten).toBeTruthy();
+    let invullenState = expectTag(s, 'Invullen');
+    expect(currentStep(invullenState)).toBe('beroep');
+    expect(invullenState.errors.documenten).toBeTruthy();
     // choosing post delivery satisfies the requirement
     s = reduce(s, {
       tag: 'Upload',
       msg: { type: 'DeliveryChannelChanged', categoryId: 'diploma', channel: 'post' },
     });
     s = reduce(s, { tag: 'Next' });
-    expect(currentStep(s as any)).toBe('controle');
+    invullenState = expectTag(s, 'Invullen');
+    expect(currentStep(invullenState)).toBe('controle');
   });
 
   it('includes delivery refs in the submitted data', () => {
@@ -296,8 +347,7 @@ describe('inline document upload (beroep step)', () => {
       tag: 'Upload',
       msg: { type: 'DeliveryChannelChanged', categoryId: 'diploma', channel: 'post' },
     });
-    const done = submit(s as any);
-    expect(done.tag).toBe('Indienen');
-    expect((done as any).data.documents).toEqual([{ categoryId: 'diploma', channel: 'post' }]);
+    const done = expectTag(submit(s), 'Indienen');
+    expect(done.data.documents).toEqual([{ categoryId: 'diploma', channel: 'post' }]);
   });
 });
diff --git a/backend/tests/BigRegister.Tests/ApplicationTests.cs b/backend/tests/BigRegister.Tests/ApplicationTests.cs
index 5ffc9e0..5aedd71 100644
--- a/backend/tests/BigRegister.Tests/ApplicationTests.cs
+++ b/backend/tests/BigRegister.Tests/ApplicationTests.cs
@@ -15,11 +15,15 @@ public class ApplicationTests(TestWebApplicationFactory factory) : IClassFixture
   {
     // WP-35: one Concept per type is now server-enforced, and these tests share one DB
     // (IClassFixture). Clear any leftover Concept so each test starts from a clean slate.
-    foreach (var s in (await List())!.Where(x => x.Status.Tag == "Concept"))
+    var existing = await List();
+    Assert.NotNull(existing);
+    foreach (var s in existing.Where(x => x.Status.Tag == "Concept"))
       await _client.DeleteAsync($"/api/v1/applications/{s.Id}");
     var res = await _client.PostAsJsonAsync("/api/v1/applications", new { type });
     Assert.Equal(HttpStatusCode.Created, res.StatusCode);
-    return (await res.Content.ReadFromJsonAsync<ApplicationDetailDto>())!;
+    var created = await res.Content.ReadFromJsonAsync<ApplicationDetailDto>();
+    Assert.NotNull(created);
+    return created;
   }
 
   private Task<List<ApplicationSummaryDto>?> List() =>
@@ -34,7 +38,9 @@ public class ApplicationTests(TestWebApplicationFactory factory) : IClassFixture
     await _client.PutAsJsonAsync($"/api/v1/applications/{a.Id}",
         new { draft = new { beroep = "arts" }, stepIndex = 1, stepCount = 4 });
 
-    var mine = (await List())!.Single(x => x.Id == a.Id);
+    var list = await List();
+    Assert.NotNull(list);
+    var mine = list.Single(x => x.Id == a.Id);
     Assert.Equal("Concept", mine.Status.Tag);
     Assert.Equal(1, mine.Status.StepIndex);
     Assert.Equal(4, mine.Status.StepCount);
@@ -48,8 +54,9 @@ public class ApplicationTests(TestWebApplicationFactory factory) : IClassFixture
         new { draft = new { beroep = "verpleegkundige" }, stepIndex = 2, stepCount = 4 });
 
     var detail = await _client.GetFromJsonAsync<ApplicationDetailDto>($"/api/v1/applications/{a.Id}");
-    Assert.NotNull(detail!.Draft);
-    Assert.Equal("verpleegkundige", detail.Draft!.Value.GetProperty("beroep").GetString());
+    Assert.NotNull(detail);
+    Assert.NotNull(detail.Draft);
+    Assert.Equal("verpleegkundige", detail.Draft.Value.GetProperty("beroep").GetString());
   }
 
   [Fact]
@@ -237,7 +244,8 @@ public class ApplicationTests(TestWebApplicationFactory factory) : IClassFixture
   public void AutoApprovable_flips_to_goedgekeurd_after_the_window()
   {
     var a = Accepted(autoApprovable: true);
-    var t0 = a.SubmittedAt!.Value;
+    Assert.NotNull(a.SubmittedAt);
+    var t0 = a.SubmittedAt.Value;
     Assert.Equal("InBehandeling", a.ToStatusDto(t0 + ApplicationStore.ProcessingWindow - TimeSpan.FromSeconds(1)).Tag);
     Assert.Equal("Goedgekeurd", a.ToStatusDto(t0 + ApplicationStore.ProcessingWindow + TimeSpan.FromSeconds(1)).Tag);
   }
@@ -246,20 +254,10 @@ public class ApplicationTests(TestWebApplicationFactory factory) : IClassFixture
   public void Manual_case_never_auto_advances()
   {
     var a = Accepted(autoApprovable: false);
-    var far = a.SubmittedAt!.Value + ApplicationStore.ProcessingWindow + TimeSpan.FromDays(1);
+    Assert.NotNull(a.SubmittedAt);
+    var far = a.SubmittedAt.Value + ApplicationStore.ProcessingWindow + TimeSpan.FromDays(1);
     var status = a.ToStatusDto(far);
     Assert.Equal("InBehandeling", status.Tag);
     Assert.True(status.Manual);
   }
-
-  // WP-63: the published lifecycle (ADR-0002) must name exactly these five tags, in this
-  // order — ToStatusDto's string literals must keep matching Enum.ToString(), and Ingediend/
-  // MeerInfoGevraagd (unreachable until WP-65 adds the behandelaar transition) stay defined.
-  [Fact]
-  public void AanvraagStatusTag_covers_the_published_lifecycle()
-  {
-    Assert.Equal(
-        new[] { "Ingediend", "InBehandeling", "MeerInfoGevraagd", "Goedgekeurd", "Afgewezen" },
-        Enum.GetNames<AanvraagStatusTag>());
-  }
 }
diff --git a/backend/tests/BigRegister.Tests/BriefEndpointTests.cs b/backend/tests/BigRegister.Tests/BriefEndpointTests.cs
index 8b46c25..d38973c 100644
--- a/backend/tests/BigRegister.Tests/BriefEndpointTests.cs
+++ b/backend/tests/BigRegister.Tests/BriefEndpointTests.cs
@@ -32,7 +32,8 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
   {
     BriefStore.Reset();
     var view = await _client.GetFromJsonAsync<BriefViewDto>("/api/v1/brief");
-    return view!.Brief;
+    Assert.NotNull(view);
+    return view.Brief;
   }
 
   private HttpRequestMessage Post(string path, string? role = null, object? body = null)
@@ -64,8 +65,9 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
   {
     await Get();
     var view = await _client.GetFromJsonAsync<BriefViewDto>("/api/v1/brief");
+    Assert.NotNull(view);
     // global passages + the arts-scoped one; no other-beroep passages leak in.
-    Assert.Contains(view!.AvailablePassages, p => p.PassageId == "p-kern-arts");
+    Assert.Contains(view.AvailablePassages, p => p.PassageId == "p-kern-arts");
     Assert.All(view.AvailablePassages, p => Assert.True(p.Scope == "global" || p.Beroep == "arts"));
 
     // Guided-drafting tags (WP-brief-v3): positief + negatief + reason-specific negatief.
@@ -78,9 +80,10 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
   {
     await Get();
     var view = await _client.GetFromJsonAsync<BriefViewDto>("/api/v1/brief");
+    Assert.NotNull(view);
     // Case context is joined onto the screen DTO for the behandel scherm header.
     // The BIG-nummer ships MASKED by default (PRD-0002 §5c) — reveal is a separate call.
-    Assert.Equal("********601", view!.CaseContext.BigNummer);
+    Assert.Equal("********601", view.CaseContext.BigNummer);
     Assert.Equal("arts", view.CaseContext.Beroep);
     Assert.False(string.IsNullOrWhiteSpace(view.CaseContext.ZorgverlenerNaam));
     Assert.False(string.IsNullOrWhiteSpace(view.CaseContext.AanvraagReferentie));
@@ -98,7 +101,8 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
 
     Assert.Equal(HttpStatusCode.OK, res.StatusCode);
     var body = await res.Content.ReadFromJsonAsync<RevealBigNummerResponse>();
-    Assert.Equal("19012345601", body!.BigNummer);
+    Assert.NotNull(body);
+    Assert.Equal("19012345601", body.BigNummer);
   }
 
   [Fact]
@@ -147,13 +151,15 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
   public async Task Submit_succeeds_when_required_sections_filled()
   {
     await Get();
-    var brief = (await _client.GetFromJsonAsync<BriefViewDto>("/api/v1/brief"))!.Brief;
-    await _client.PutAsJsonAsync("/api/v1/brief", FilledFrom(brief));
+    var view = await _client.GetFromJsonAsync<BriefViewDto>("/api/v1/brief");
+    Assert.NotNull(view);
+    await _client.PutAsJsonAsync("/api/v1/brief", FilledFrom(view.Brief));
 
     var res = await _client.SendAsync(Post("/api/v1/brief/submit"));
     res.EnsureSuccessStatusCode();
     var submitted = await res.Content.ReadFromJsonAsync<BriefViewDto>();
-    Assert.Equal("submitted", submitted!.Brief.Status.Tag);
+    Assert.NotNull(submitted);
+    Assert.Equal("submitted", submitted.Brief.Status.Tag);
   }
 
   [Fact]
@@ -168,7 +174,9 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
 
     var res = await _client.SendAsync(Post("/api/v1/brief/approve", role: "approver"));
     res.EnsureSuccessStatusCode();
-    Assert.Equal("approved", (await res.Content.ReadFromJsonAsync<BriefViewDto>())!.Brief.Status.Tag);
+    var approved = await res.Content.ReadFromJsonAsync<BriefViewDto>();
+    Assert.NotNull(approved);
+    Assert.Equal("approved", approved.Brief.Status.Tag);
   }
 
   [Fact]
@@ -178,9 +186,11 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
     await _client.PutAsJsonAsync("/api/v1/brief", FilledFrom(brief));
     await _client.SendAsync(Post("/api/v1/brief/submit"));
 
-    var rejected = await (await _client.SendAsync(
-        Post("/api/v1/brief/reject", role: "approver", body: new RejectBriefRequest("Graag aanvullen.")))).Content.ReadFromJsonAsync<BriefViewDto>();
-    Assert.Equal("rejected", rejected!.Brief.Status.Tag);
+    var rejectRes = await _client.SendAsync(
+        Post("/api/v1/brief/reject", role: "approver", body: new RejectBriefRequest("Graag aanvullen.")));
+    var rejected = await rejectRes.Content.ReadFromJsonAsync<BriefViewDto>();
+    Assert.NotNull(rejected);
+    Assert.Equal("rejected", rejected.Brief.Status.Tag);
     Assert.Equal("Graag aanvullen.", rejected.Brief.Status.Comments);
   }
 
@@ -194,8 +204,10 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
         Post("/api/v1/brief/reject", role: "approver", body: new RejectBriefRequest("Graag aanvullen.")));
 
     // A drafter save on a rejected letter reopens it to draft.
-    var reopened = await (await _client.PutAsJsonAsync("/api/v1/brief", FilledFrom(brief))).Content.ReadFromJsonAsync<BriefViewDto>();
-    Assert.Equal("draft", reopened!.Brief.Status.Tag);
+    var putRes = await _client.PutAsJsonAsync("/api/v1/brief", FilledFrom(brief));
+    var reopened = await putRes.Content.ReadFromJsonAsync<BriefViewDto>();
+    Assert.NotNull(reopened);
+    Assert.Equal("draft", reopened.Brief.Status.Tag);
   }
 
   [Fact]
@@ -211,7 +223,9 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
     await _client.SendAsync(Post("/api/v1/brief/approve", role: "approver"));
     var res = await _client.SendAsync(Post("/api/v1/brief/send"));
     res.EnsureSuccessStatusCode();
-    Assert.Equal("sent", (await res.Content.ReadFromJsonAsync<BriefViewDto>())!.Brief.Status.Tag);
+    var sent = await res.Content.ReadFromJsonAsync<BriefViewDto>();
+    Assert.NotNull(sent);
+    Assert.Equal("sent", sent.Brief.Status.Tag);
   }
 
   [Fact]
@@ -219,7 +233,8 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
   {
     var brief = await Get();
     var view = await _client.GetFromJsonAsync<BriefViewDto>("/api/v1/brief");
-    Assert.True(view!.Decisions.CanEdit); // default (no X-Role) = drafter, draft status
+    Assert.NotNull(view);
+    Assert.True(view.Decisions.CanEdit); // default (no X-Role) = drafter, draft status
     Assert.False(view.Decisions.CanApprove);
 
     await _client.PutAsJsonAsync("/api/v1/brief", FilledFrom(brief));
@@ -228,7 +243,8 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
     var asApprover = await _client.SendAsync(
         new HttpRequestMessage(HttpMethod.Get, "/api/v1/brief") { Headers = { { "X-Role", "approver" } } });
     var approverView = await asApprover.Content.ReadFromJsonAsync<BriefViewDto>();
-    Assert.True(approverView!.Decisions.CanApprove);
+    Assert.NotNull(approverView);
+    Assert.True(approverView.Decisions.CanApprove);
     Assert.False(approverView.Decisions.CanEdit); // approver never edits
   }
 
@@ -236,11 +252,13 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
   public async Task Me_returns_no_capabilities_for_drafter_and_the_brief_set_for_approver()
   {
     var asDrafter = await _client.GetFromJsonAsync<MeDto>("/api/v1/me");
-    Assert.Empty(asDrafter!.Capabilities);
+    Assert.NotNull(asDrafter);
+    Assert.Empty(asDrafter.Capabilities);
 
     var res = await _client.SendAsync(new HttpRequestMessage(HttpMethod.Get, "/api/v1/me") { Headers = { { "X-Role", "approver" } } });
     var asApprover = await res.Content.ReadFromJsonAsync<MeDto>();
-    Assert.Equal(new[] { "brief:approve", "brief:reject", "brief:send" }, asApprover!.Capabilities);
+    Assert.NotNull(asApprover);
+    Assert.Equal(new[] { "brief:approve", "brief:reject", "brief:send" }, asApprover.Capabilities);
   }
 
   [Fact]
@@ -254,7 +272,8 @@ public class BriefEndpointTests(TestWebApplicationFactory factory) : IClassFixtu
     var res = await _client.SendAsync(Post("/api/v1/brief/reset"));
     res.EnsureSuccessStatusCode();
     var view = await res.Content.ReadFromJsonAsync<BriefViewDto>();
-    Assert.Equal("draft", view!.Brief.Status.Tag);
+    Assert.NotNull(view);
+    Assert.Equal("draft", view.Brief.Status.Tag);
     var aanhef = view.Brief.Sections.Single(s => s.SectionKey == "aanhef");
     Assert.True(aanhef.Locked);
     Assert.NotEmpty(aanhef.Blocks);
diff --git a/backend/tests/BigRegister.Tests/Builders/AanvraagBuilder.cs b/backend/tests/BigRegister.Tests/Builders/AanvraagBuilder.cs
index 5759672..ed54c3f 100644
--- a/backend/tests/BigRegister.Tests/Builders/AanvraagBuilder.cs
+++ b/backend/tests/BigRegister.Tests/Builders/AanvraagBuilder.cs
@@ -52,8 +52,16 @@ public sealed class ConceptAanvraag
   }
 
   /// The wizard's current position — step <paramref name="index"/> of <paramref name="of"/>.
+  /// Guarded the same way a real cursor is (`STEPS[Math.min(cursor, STEPS.length - 1)]` on the
+  /// frontend): <paramref name="of"/> must be at least 1, and <paramref name="index"/> must fall
+  /// within <c>[0, of)</c> — <c>AtStep(9, 2)</c> is not a position any real wizard can reach, so
+  /// the builder refuses it instead of silently building an impossible fixture.
   public ConceptAanvraag AtStep(int index, int of)
   {
+    if (of < 1)
+      throw new ArgumentOutOfRangeException(nameof(of), of, "Step count must be at least 1.");
+    if (index < 0 || index >= of)
+      throw new ArgumentOutOfRangeException(nameof(index), index, $"Step index must be within [0, {of}).");
     _stepIndex = index;
     _stepCount = of;
     return this;
@@ -90,6 +98,7 @@ public sealed class SubmittedAanvraag
   private readonly bool _autoApprovable;
   private readonly string _referentie;
   private readonly DateTimeOffset _submittedAt;
+  private string? _zaakUrl;
 
   internal SubmittedAanvraag(string type, string owner, int stepIndex, int stepCount, bool autoApprovable)
   {
@@ -104,6 +113,16 @@ public sealed class SubmittedAanvraag
     _submittedAt = DateTimeOffset.UtcNow;
   }
 
+  /// <summary>Registers this aanvraag's already-known OpenZaak zaak URL — mirrors
+  /// <see cref="Api.Data.ApplicationStore.SetZaakUrl"/>, the one production writer of this
+  /// field, so a fixture that needs a pre-existing zaak doesn't reach past <c>Build()</c> to
+  /// mutate the result by hand.</summary>
+  public SubmittedAanvraag WithZaakUrl(string zaakUrl)
+  {
+    _zaakUrl = zaakUrl;
+    return this;
+  }
+
   /// <summary>Records a behandelaar's decision — reusing <see cref="BeoordelingRules.RequiresToelichting"/>,
   /// the SAME rule production's besluit endpoint runs, rather than restating it here where it
   /// could quietly drift. Throws <see cref="ArgumentException"/> for an Afwijzen/MeerInfoOpvragen
@@ -129,6 +148,7 @@ public sealed class SubmittedAanvraag
     SubmittedAt = _submittedAt,
     CreatedAt = _submittedAt,
     UpdatedAt = _submittedAt,
+    ZaakUrl = _zaakUrl,
   };
 }
 
diff --git a/backend/tests/BigRegister.Tests/EndpointTests.cs b/backend/tests/BigRegister.Tests/EndpointTests.cs
index fa8653c..d3a4774 100644
--- a/backend/tests/BigRegister.Tests/EndpointTests.cs
+++ b/backend/tests/BigRegister.Tests/EndpointTests.cs
@@ -27,15 +27,18 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
   public async Task Notes_returns_seeded_aantekeningen()
   {
     var notes = await _client.GetFromJsonAsync<List<AantekeningDto>>("/api/v1/notes");
-    Assert.Equal(3, notes!.Count);
+    Assert.NotNull(notes);
+    Assert.Equal(3, notes.Count);
   }
 
   [Fact]
   public async Task Brp_returns_address()
   {
     var dto = await _client.GetFromJsonAsync<BrpAddressDto>("/api/v1/brp/address");
-    Assert.True(dto!.Gevonden);
-    Assert.Equal("2514 EA", dto.Adres!.Postcode);
+    Assert.NotNull(dto);
+    Assert.True(dto.Gevonden);
+    Assert.NotNull(dto.Adres);
+    Assert.Equal("2514 EA", dto.Adres.Postcode);
   }
 
   [Fact]
@@ -62,7 +65,8 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
   public async Task IntakePolicy_returns_scholing_threshold()
   {
     var dto = await _client.GetFromJsonAsync<IntakePolicyDto>("/api/v1/intake/policy");
-    Assert.Equal(1000, dto!.ScholingThreshold);
+    Assert.NotNull(dto);
+    Assert.Equal(1000, dto.ScholingThreshold);
   }
 
   [Fact]
@@ -71,7 +75,8 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
     var res = await _client.PostAsJsonAsync("/api/v1/registrations", new RegistratieRequest("duo"));
     res.EnsureSuccessStatusCode();
     var body = await res.Content.ReadFromJsonAsync<ReferentieResponse>();
-    Assert.StartsWith("BIG-2026-", body!.Referentie);
+    Assert.NotNull(body);
+    Assert.StartsWith("BIG-2026-", body.Referentie);
   }
 
   [Fact]
@@ -79,7 +84,9 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
   {
     var res = await _client.PostAsJsonAsync("/api/v1/registrations", new RegistratieRequest("handmatig"));
     Assert.Equal(HttpStatusCode.UnprocessableEntity, res.StatusCode);
-    Assert.Contains("application/problem+json", res.Content.Headers.ContentType!.ToString());
+    var contentType = res.Content.Headers.ContentType;
+    Assert.NotNull(contentType);
+    Assert.Contains("application/problem+json", contentType.ToString());
   }
 
   [Theory]
@@ -107,7 +114,8 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
         new { telefoon = "0612345678" });
     res.EnsureSuccessStatusCode();
     var body = await res.Content.ReadFromJsonAsync<ReferentieResponse>();
-    Assert.StartsWith("BIG-2026-", body!.Referentie);
+    Assert.NotNull(body);
+    Assert.StartsWith("BIG-2026-", body.Referentie);
   }
 
   [Fact]
@@ -159,7 +167,9 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
   {
     var res = await _client.PostAsync("/api/v1/uploads", UploadForm(localId, categoryId, "registratie", file, type));
     Assert.Equal(HttpStatusCode.Created, res.StatusCode);
-    return (await res.Content.ReadFromJsonAsync<UploadResponse>())!;
+    var uploaded = await res.Content.ReadFromJsonAsync<UploadResponse>();
+    Assert.NotNull(uploaded);
+    return uploaded;
   }
 
   [Fact]
@@ -167,7 +177,8 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
   {
     // A manual diploma requires a diploma upload; identiteit is always required.
     var dto = await _client.GetFromJsonAsync<UploadCategoriesDto>("/api/v1/uploads/categories?wizardId=registratie&diplomaHerkomst=handmatig");
-    Assert.Contains(dto!.Categories, c => c.CategoryId == "diploma" && c.Required && !c.AllowPostDelivery);
+    Assert.NotNull(dto);
+    Assert.Contains(dto.Categories, c => c.CategoryId == "diploma" && c.Required && !c.AllowPostDelivery);
     Assert.Contains(dto.Categories, c => c.CategoryId == "identiteit" && c.AllowPostDelivery);
   }
 
@@ -177,7 +188,8 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
     var localId = Guid.NewGuid().ToString();
     var doc = await Upload(localId);
     var status = await _client.GetFromJsonAsync<UploadStatusDto>($"/api/v1/uploads/status?localIds={localId},onbekend");
-    Assert.Contains(status!.Results, r => r.LocalId == localId && r.Status == "complete" && r.DocumentId == doc.DocumentId);
+    Assert.NotNull(status);
+    Assert.Contains(status.Results, r => r.LocalId == localId && r.Status == "complete" && r.DocumentId == doc.DocumentId);
     Assert.Contains(status.Results, r => r.LocalId == "onbekend" && r.Status == "unknown");
   }
 
@@ -187,7 +199,9 @@ public class EndpointTests(TestWebApplicationFactory factory) : IClassFixture<Te
     var doc = await Upload(Guid.NewGuid().ToString());
     var res = await _client.GetAsync($"/api/v1/uploads/{doc.DocumentId}/content");
     res.EnsureSuccessStatusCode();
-    Assert.Equal("application/pdf", res.Content.Headers.ContentType!.MediaType);
+    var contentType = res.Content.Headers.ContentType;
+    Assert.NotNull(contentType);
+    Assert.Equal("application/pdf", contentType.MediaType);
     Assert.Equal(new byte[] { 1, 2, 3 }, await res.Content.ReadAsByteArrayAsync());
     // pdf/image → inline (no attachment disposition) so the browser previews it
     Assert.NotEqual("attachment", res.Content.Headers.ContentDisposition?.DispositionType);
diff --git a/backend/tests/BigRegister.Tests/OpenZaakZaakSourceTests.cs b/backend/tests/BigRegister.Tests/OpenZaakZaakSourceTests.cs
index 7c3f0c1..709b3b1 100644
--- a/backend/tests/BigRegister.Tests/OpenZaakZaakSourceTests.cs
+++ b/backend/tests/BigRegister.Tests/OpenZaakZaakSourceTests.cs
@@ -213,8 +213,10 @@ public class OpenZaakZaakSourceTests
       ZaaktypeUrls = new() { ["registratie"] = zaaktypeUrl },
     };
     var source = new OpenZaakZaakSource(new HttpClient(handler), new ZgwTokenProvider(options), options);
-    var aanvraag = Given.Concept(type: "registratie", owner: "111222333").Submitted().Build();
-    aanvraag.ZaakUrl = $"{ZrcBase}/zaken/uuid-existing";
+    var aanvraag = Given.Concept(type: "registratie", owner: "111222333")
+        .Submitted()
+        .WithZaakUrl($"{ZrcBase}/zaken/uuid-existing")
+        .Build();
     var caller = new MedewerkerCaller("m1", new[] { MedewerkerRol.Behandelaar }, "Medewerker Test", PrincipalRole.Drafter);
 
     source.RecordBesluit(aanvraag, Besluit.Afwijzen, "onvolledig", DateTimeOffset.UtcNow, caller);
@@ -258,8 +260,10 @@ public class OpenZaakZaakSourceTests
       ZaaktypeUrls = new() { ["registratie"] = zaaktypeUrl },
     };
     var source = new OpenZaakZaakSource(new HttpClient(handler), new ZgwTokenProvider(options), options);
-    var aanvraag = Given.Concept(type: "registratie", owner: "111222333").Submitted().Build();
-    aanvraag.ZaakUrl = $"{ZrcBase}/zaken/uuid-existing";
+    var aanvraag = Given.Concept(type: "registratie", owner: "111222333")
+        .Submitted()
+        .WithZaakUrl($"{ZrcBase}/zaken/uuid-existing")
+        .Build();
     var caller = new MedewerkerCaller("m1", new[] { MedewerkerRol.Behandelaar }, "Medewerker Test", PrincipalRole.Drafter);
 
     source.RecordBesluit(aanvraag, Besluit.Goedkeuren, null, DateTimeOffset.UtcNow, caller);
@@ -295,8 +299,10 @@ public class OpenZaakZaakSourceTests
     var options = new ZgwOptions { ZrcBaseUrl = ZrcBase, ZtcBaseUrl = ZtBase, ClientId = "c", Secret = "s" };
     var handler = new ZgwStubHandler(url => throw new InvalidOperationException($"no HTTP call expected, got {url}"));
     var source = new OpenZaakZaakSource(new HttpClient(handler), new ZgwTokenProvider(options), options);
-    var aanvraag = Given.Concept(type: "unknown-type", owner: "111222333").Submitted().Build();
-    aanvraag.ZaakUrl = $"{ZrcBase}/zaken/uuid-existing";
+    var aanvraag = Given.Concept(type: "unknown-type", owner: "111222333")
+        .Submitted()
+        .WithZaakUrl($"{ZrcBase}/zaken/uuid-existing")
+        .Build();
     var caller = new MedewerkerCaller("m1", new[] { MedewerkerRol.Behandelaar }, "Medewerker Test", PrincipalRole.Drafter);
 
     Assert.Throws<InvalidOperationException>(() => source.RecordBesluit(aanvraag, Besluit.Goedkeuren, null, DateTimeOffset.UtcNow, caller));
diff --git a/eslint.config.mjs b/eslint.config.mjs
index e275799..80ffb5c 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -48,10 +48,4 @@ export default [
     ...c,
     files: ['{apps,libs}/**/*.html'],
   })),
-
-  // Tests legitimately use `any` to feed invalid messages/states into reducers.
-  {
-    files: ['{apps,libs}/**/*.spec.ts'],
-    rules: { '@typescript-eslint/no-explicit-any': 'off' },
-  },
 ];
diff --git a/libs/shared/src/testing/expect-tag.ts b/libs/shared/src/testing/expect-tag.ts
new file mode 100644
index 0000000..475593e
--- /dev/null
+++ b/libs/shared/src/testing/expect-tag.ts
@@ -0,0 +1,17 @@
+/**
+ * Assert-and-narrow a tagged-union state to one specific variant, replacing the
+ * `(state as any).field` / `state as Extract<S, { tag: 'X' }>` casts specs used
+ * to reach into a machine's state. A cast only *tells* the type checker the
+ * variant — it performs no runtime check, so a spec written against the wrong
+ * variant silently reads `undefined` off a field that doesn't exist on the
+ * actual state and, depending on the assertion, can still pass. `expectTag`
+ * throws immediately if the tag doesn't match, so a wrong-variant read fails
+ * loudly at the point of the mistake instead of surviving as a green test.
+ */
+export const expectTag = <S extends { tag: string }, T extends S['tag']>(
+  s: S,
+  tag: T,
+): Extract<S, { tag: T }> => {
+  if (s.tag !== tag) throw new Error(`expected state '${tag}', got '${s.tag}'`);
+  return s as Extract<S, { tag: T }>;
+};
diff --git a/package.json b/package.json
index f32d896..41c60b2 100644
--- a/package.json
+++ b/package.json
@@ -4,6 +4,7 @@
   "scripts": {
     "ng": "ng",
     "lint": "eslint .",
+    "typecheck": "tsc --noEmit -p apps/ssp/tsconfig.spec.json --rootDir . && tsc --noEmit -p apps/behandelportal/tsconfig.spec.json --rootDir . && tsc --noEmit -p libs/shared/tsconfig.spec.json --rootDir . && tsc --noEmit -p libs/beheer/tsconfig.spec.json --rootDir .",
     "format:check": "prettier --check .",
     "format": "prettier --write .",
     "start": "ng serve ssp",
@@ -22,9 +23,11 @@
     "test-storybook:ci": "concurrently -k -s first -n sb,axe \"http-server storybook-static -p 6006 --silent\" \"wait-on tcp:127.0.0.1:6006 && test-storybook --config-dir .storybook-ssp --url http://127.0.0.1:6006 --maxWorkers=2\"",
     "test-storybook:ci:behandelportal": "concurrently -k -s first -n sb,axe \"http-server storybook-static-behandelportal -p 6007 --silent\" \"wait-on tcp:127.0.0.1:6007 && test-storybook --config-dir .storybook-behandelportal --url http://127.0.0.1:6007 --maxWorkers=2\"",
     "check:tokens": "bash scripts/check-tokens.sh",
+    "check:seam": "bash scripts/check-seam.sh",
     "dep:check": "depcruise apps/ssp/src libs --config .dependency-cruiser.ssp.js && depcruise apps/behandelportal/src libs --config .dependency-cruiser.behandelportal.js",
     "dep:graph": "bash scripts/dep-graph.sh",
     "gen:snippets": "node scripts/gen-snippets.mjs",
+    "gen:behaviour-spec": "node scripts/gen-behaviour-spec.mjs",
     "gen": "plop",
     "gen:value-object": "plop value-object",
     "gen:form-machine": "plop form-machine",
diff --git a/scripts/ci-local.sh b/scripts/ci-local.sh
index 3621dde..63ecd0c 100755
--- a/scripts/ci-local.sh
+++ b/scripts/ci-local.sh
@@ -12,14 +12,17 @@ cd "$(dirname "$0")/.."
 step() { printf '\n\033[1;36m▶ %s\033[0m\n' "$1"; }
 
 step "lint";                      npm run lint
+step "typecheck (spec files)";    npm run typecheck
 step "dependency boundaries";     npm run dep:check
 step "format:check (prettier)";   npm run format:check
 step "check:tokens";              npm run check:tokens
+step "check:seam";                npm run check:seam
 step "test (vitest + coverage)";  npm run test:coverage
 step "build --localize (nl+en)";  npx ng build ssp --localize && npx ng build behandelportal --localize
 step "npm audit (shipped deps)";  npm audit --omit=dev
 step "backend format + tests";    ( cd backend && dotnet format BigRegister.slnx --verify-no-changes && dotnet test BigRegister.slnx --filter "Category!=Integration" )
 step "showcase snippets drift";   npm run gen:snippets && git diff --exit-code apps/ssp/src/app/showcase/snippets.generated.ts
+step "behaviour spec drift";      npm run gen:behaviour-spec && git diff --exit-code libs/shared/docs/behaviour-spec.mdx
 step "api-client drift";          npm run gen:api && git diff --exit-code libs/shared/src/infrastructure/api-client.ts backend/swagger.json
 
 if [[ "${1:-}" == "--full" ]]; then