refactor(registratie): extract the read half of createDraftSync (RB-21)

createDraftSync mixed a read path (findConcept, load, the read half of
resume) with its write path (ensureId, flush, submit, reset) in one
187-line function -- CQ-001's finding. Move findConcept and loadConcept
into a new application/find-concept.ts as free functions that take the
adapter, so they get a direct spec with no Angular TestBed.

createDraftSync keeps the closure state (id, ensuring, resumeGate) and
the whole write path unchanged -- this is a move, not a redesign. The
resumeGate coupling that lets the write path wait for the read path
stays exactly where it was.

createDraftSync shrinks from 187 to 169 lines. draft-sync.spec.ts is
unchanged -- it never called resume()/load() directly, and its 409
recovery test for submit() still exercises the extracted findConcept
through ensureId's catch branch.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

apps/ssp/src/app/registratie/application/draft-sync.ts

@@ -8,10 +8,8 @@ import type {
   SubmitApplicationResponse,
 } from '@shared/infrastructure/api-client';
 import { AanvraagType } from '@registratie/domain/aanvraag';
-import {
+import { ApplicationsAdapter } from '@registratie/infrastructure/applications.adapter';
-  ApplicationsAdapter,
+import { findConcept, loadConcept } from './find-concept';
-  parseApplications,
-} from '@registratie/infrastructure/applications.adapter';
 
 /** What a wizard persists per step: the opaque machine snapshot + progress + docs. */
 export interface DraftSnapshot {
@@ -70,7 +68,7 @@ export function createDraftSync(deps: DraftSyncDeps) {
       // server's guard (409) — recover by adopting the existing Concept instead of
       // erroring. Only recover when one actually exists; otherwise surface the failure.
       .catch(async (e) => {
-        const existing = await findConcept();
+        const existing = await findConcept(adapter, deps.type);
         if (existing) return existing;
         throw e;
       })
@@ -140,34 +138,16 @@ export function createDraftSync(deps: DraftSyncDeps) {
   // (submitted/gone) id is treated as fresh so it can't reopen as an editable draft.
   const load = (linked: string): Promise<void> => {
     id = linked;
-    return adapter
+    return loadConcept(adapter, linked).then((result) => {
-      .detail(linked)
+      if (result.tag === 'not-concept') {
-      .then((dto) => {
-        if (dto.status && dto.status.tag !== 'Concept') {
         id = undefined;
         applyResume(null);
         return;
       }
-        applyResume(dto.draft ?? null);
+      applyResume(result.draft);
-      })
-      .catch(() => {
-        id = undefined;
-        applyResume(null); // unknown/deleted id → start fresh
     });
   };
 
-  // Find the user's existing Concept of this type (at most one), if any.
-  const findConcept = async (): Promise<string | undefined> => {
-    try {
-      const parsed = parseApplications(await adapter.list());
-      return parsed.ok
-        ? parsed.value.find((a) => a.type === deps.type && a.status.tag === 'Concept')?.id
-        : undefined;
-    } catch {
-      return undefined;
-    }
-  };
-
   return {
     /** True while a debounced draft write is still pending (PendingSave). */
     hasPendingSave,
@@ -189,7 +169,7 @@ export function createDraftSync(deps: DraftSyncDeps) {
           await load(linked);
           return;
         }
-        const existing = await findConcept();
+        const existing = await findConcept(adapter, deps.type);
         if (existing) {
           await load(existing);
           // Stamp the id into the URL so a reload resumes the same Concept.

apps/ssp/src/app/registratie/application/find-concept.spec.ts

@@ -0,0 +1,108 @@
+import { describe, it, expect } from 'vitest';
+import { ApplicationsAdapter } from '@registratie/infrastructure/applications.adapter';
+import { findConcept, loadConcept } from './find-concept';
+
+// Free functions taking the adapter as a parameter (no inject()) — a plain fake
+// object is enough, no Angular TestBed needed.
+function fakeAdapter(overrides: Partial<ApplicationsAdapter>): ApplicationsAdapter {
+  return overrides as ApplicationsAdapter;
+}
+
+describe('findConcept', () => {
+  it('returns the id of the existing Concept of the given type', async () => {
+    const adapter = fakeAdapter({
+      list: async () => [
+        {
+          id: 'a1',
+          type: 'registratie',
+          status: { tag: 'Concept', stepIndex: 0, stepCount: 3 },
+          createdAt: '2026-01-01T00:00:00Z',
+          updatedAt: '2026-01-01T00:00:00Z',
+        },
+      ],
+    });
+
+    await expect(findConcept(adapter, 'registratie')).resolves.toBe('a1');
+  });
+
+  it('returns undefined when the list has no application of the given type', async () => {
+    const adapter = fakeAdapter({ list: async () => [] });
+
+    await expect(findConcept(adapter, 'registratie')).resolves.toBeUndefined();
+  });
+
+  it('returns undefined when the matching type is not a Concept', async () => {
+    const adapter = fakeAdapter({
+      list: async () => [
+        {
+          id: 'a1',
+          type: 'registratie',
+          status: { tag: 'Ingediend', referentie: 'R1' },
+          createdAt: '2026-01-01T00:00:00Z',
+          updatedAt: '2026-01-01T00:00:00Z',
+        },
+      ],
+    });
+
+    await expect(findConcept(adapter, 'registratie')).resolves.toBeUndefined();
+  });
+
+  it('returns undefined when adapter.list() resolves with an unparsable shape', async () => {
+    const adapter = fakeAdapter({ list: async () => 'not-an-array' as unknown as [] });
+
+    await expect(findConcept(adapter, 'registratie')).resolves.toBeUndefined();
+  });
+
+  it('returns undefined when adapter.list() rejects', async () => {
+    const adapter = fakeAdapter({
+      list: async () => {
+        throw new Error('network down');
+      },
+    });
+
+    await expect(findConcept(adapter, 'registratie')).resolves.toBeUndefined();
+  });
+});
+
+describe('loadConcept', () => {
+  it('reads the draft off a Concept', async () => {
+    const adapter = fakeAdapter({
+      detail: async () => ({
+        id: 'a1',
+        status: { tag: 'Concept', stepIndex: 1, stepCount: 3 },
+        draft: { step: 1 },
+      }),
+    });
+
+    await expect(loadConcept(adapter, 'a1')).resolves.toEqual({
+      tag: 'concept',
+      draft: { step: 1 },
+    });
+  });
+
+  it('reports a missing draft as null', async () => {
+    const adapter = fakeAdapter({
+      detail: async () => ({ id: 'a1', status: { tag: 'Concept', stepIndex: 0, stepCount: 3 } }),
+    });
+
+    await expect(loadConcept(adapter, 'a1')).resolves.toEqual({ tag: 'concept', draft: null });
+  });
+
+  it('reports not-concept when the id has moved past Concept (submitted)', async () => {
+    const adapter = fakeAdapter({
+      detail: async () => ({ id: 'a1', status: { tag: 'Ingediend', referentie: 'R1' } }),
+    });
+
+    await expect(loadConcept(adapter, 'a1')).resolves.toEqual({ tag: 'not-concept' });
+  });
+
+  it('reports not-concept when the id is unknown or deleted (detail rejects)', async () => {
+    const adapter = fakeAdapter({
+      detail: async () => {
+        throw new Error('404');
+      },
+    });
+
+    await expect(loadConcept(adapter, 'gone')).resolves.toEqual({ tag: 'not-concept' });
+  });
+});

apps/ssp/src/app/registratie/application/find-concept.ts

@@ -0,0 +1,48 @@
+import { AanvraagType } from '@registratie/domain/aanvraag';
+import {
+  ApplicationsAdapter,
+  parseApplications,
+} from '@registratie/infrastructure/applications.adapter';
+
+/**
+ * Read half of the Concept lookup that `createDraftSync` (`draft-sync.ts`) needs
+ * before it can start writing (RB-21 / CQ-001). Free functions that take the adapter
+ * as a parameter, not `inject()`, so they get a direct spec without Angular TestBed.
+ * `createDraftSync` keeps the closure state (`id`, `resumeGate`) and the write path;
+ * these two functions only read.
+ */
+
+/** Find the user's existing Concept of a given type (at most one), if any. */
+export async function findConcept(
+  adapter: ApplicationsAdapter,
+  type: AanvraagType,
+): Promise<string | undefined> {
+  try {
+    const parsed = parseApplications(await adapter.list());
+    return parsed.ok
+      ? parsed.value.find((a) => a.type === type && a.status.tag === 'Concept')?.id
+      : undefined;
+  } catch {
+    return undefined;
+  }
+}
+
+/** Outcome of loading one Concept by id: its draft (or null when it has none), or
+    `not-concept` when the id is not an editable Concept (submitted/gone) or the
+    lookup failed (unknown/deleted id) — the caller treats both the same way, as
+    "start fresh". */
+export type LoadedConcept = { tag: 'concept'; draft: unknown | null } | { tag: 'not-concept' };
+
+/** Load a specific Concept by id and report whether it is still editable. */
+export async function loadConcept(
+  adapter: ApplicationsAdapter,
+  id: string,
+): Promise<LoadedConcept> {
+  try {
+    const dto = await adapter.detail(id);
+    if (dto.status && dto.status.tag !== 'Concept') return { tag: 'not-concept' };
+    return { tag: 'concept', draft: dto.draft ?? null };
+  } catch {
+    return { tag: 'not-concept' };
+  }
+}

docs/project/refactor-backlog-setup/refactor-backlog/99-backlog.md

@@ -101,7 +101,7 @@ Every ticket tracing to a `BIO-` finding, plus every row on agent 07's authorita
 16-row "Compliance review required" list, carries it — regardless of priority.
 
 | ID        | Module                           | Category      | Description                                                                                             | Baseline metric improved                                                                                      | Effort | Risk     | Priority | CD batch # | Depends on | Compliance   | Status      |
-| --------- | -------------------------------- | ------------- | ------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------- | ------ | -------- | -------- | ---------- | ---------- | ------------ | -------- |
+| --------- | -------------------------------- | ------------- | ------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------- | ------ | -------- | -------- | ---------- | ---------- | ------------ | ----------- |
 | **RB-01** | backend/Program.cs + Data        | security      | Add an owner/capability check to `GET /uploads/{id}/content` and `/uploads/status`; 404 not 403         | §3c Data 75.5% branch vs 99.0% line (BL-005)                                                                  | S      | Low      | **P1**   | 1          | —          | **SIGN-OFF** | **done**    |
 | **RB-02** | backend/Program.cs + Data        | privacy       | Stop concatenating the BSN into `AuthzAudit.Resource`; assert on **values** in the test                 | §3c Data 75.5% branch (BL-005)                                                                                | S      | Low      | **P1**   | 1          | —          | **SIGN-OFF** | **done**    |
 | **RB-03** | backend/Contracts                | privacy       | `MaskTail(a.Owner, 3)` in `ToAdminSummaryDto` — both cross-owner lists inherit it                       | §3a bhp/behandeling 91.6%/81.5%; §7 Mapping row                                                               | S      | Low      | **P1**   | 1          | —          | **SIGN-OFF** | **done**    |
@@ -122,7 +122,7 @@ Every ticket tracing to a `BIO-` finding, plus every row on agent 07's authorita
 | **RB-18** | backend/Data                     | security      | Key `IdempotencyStore` on `{SubjectId}:{idemKey}`                                                       | §7 stores "Not behind any port"; agent 02's Data note (no TTL, no reset)                                      | S      | Low      | P2       | 3          | RB-17      | **SIGN-OFF** | open        |
 | **RB-19** | backend/Program.cs               | structure     | Reorder all 48 endpoints under read/write sub-banners; regroup admin-cases + org-template preview       | BL-003 (940 lines, file CC 78 vs next-highest 27)                                                             | S      | **High** | P2       | 4          | RB-12      | **SIGN-OFF** | open        |
 | **RB-20** | ssp/registratie                  | CQRS-light    | `ApplicationsStore.cancel` / `AdminCasesStore.delete` through `runSubmit`; surface the error            | BL-007; §7 "Command factories 3"                                                                              | S      | Low      | P2       | 4          | —          | **SIGN-OFF** | open        |
-| **RB-21** | ssp/registratie                  | CQRS-light    | Extract the read half of `createDraftSync` into `application/find-concept.ts`                           | §4a `createDraftSync` 143 lines — longest fn in the repo; §9 (>40)                                            | M      | Med      | P2       | 4          | —          | —            | open     |
+| **RB-21** | ssp/registratie                  | CQRS-light    | Extract the read half of `createDraftSync` into `application/find-concept.ts`                           | §4a `createDraftSync` 143 lines — longest fn in the repo; §9 (>40)                                            | M      | Med      | P2       | 4          | —          | —            | implemented |
 | **RB-22** | ssp/brief                        | CQRS-light    | _(expand)_ `BriefStore.load()` tolerates a 404 by calling the existing `reset()` once                   | BL-003; §7 Backend CQRS-light row                                                                             | S      | Low      | P2       | 4          | —          | **SIGN-OFF** | open        |
 | **RB-23** | backend/Program.cs + Data        | CQRS-light    | _(contract)_ `GET /brief` 404s when absent; `GetOrCreate` → `Get`                                       | BL-003; §7 Backend CQRS-light row                                                                             | S      | Med      | P2       | 4          | RB-22      | **SIGN-OFF** | open        |
 | **RB-24** | libs/shared/upload               | ADR conform.  | Move `upload/` into `infrastructure`/`domain`/`application`; **delete** the depcruise carve-out         | BL-010; §7 "+1 adapter outside `infrastructure/`", "8 of 9 machines in `domain/`"; §3b shared/domain 0% reach | M      | Med      | P2       | 5          | —          | **SIGN-OFF** | open        |

docs/project/refactor-backlog-setup/refactor-backlog/implementation/rb-21.md

@@ -0,0 +1,119 @@
+# RB-21 — extract the read half of `createDraftSync` into `find-concept.ts`
+
+Status: **implemented** · 2026-08-27 · Source finding: `04-cqrs-light.md` CQ-001 ·
+`00-baseline.md` §4a (`createDraftSync` 143 lines, the largest function in the repo), §9
+(`fn > 40` threshold) · `99-backlog.md` RB-21
+
+## What was wrong
+
+`createDraftSync` (`apps/ssp/src/app/registratie/application/draft-sync.ts`) was registered
+as a command factory but owned three read paths (`load`, `findConcept`, and the read half of
+`resume`) mixed into the same function as the write path (`ensureId`, `flush`, `submit`,
+`reset`). CQ-001 named three pieces of shared mutable closure state — `id`, `ensuring`,
+`resumeGate` — as load-bearing: `resumeGate` exists only so the write path (`ensureId`) can
+wait for the read path (`resume`) to finish. That coupling is genuine and stays in place.
+
+## What changed
+
+CQ-001's proposal, applied as a pure move, no redesign.
+
+| File                                                                  | Change                                                                                                                                                                                                                                                                                      |
+| --------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `apps/ssp/src/app/registratie/application/find-concept.ts` (new)      | `findConcept(adapter, type)` and `loadConcept(adapter, id)` — free functions taking `ApplicationsAdapter`, no `inject()`. `loadConcept` returns a `LoadedConcept` union (`{tag:'concept', draft}` \| `{tag:'not-concept'}`) instead of the boolean-shaped branching the inline version had. |
+| `apps/ssp/src/app/registratie/application/find-concept.spec.ts` (new) | Direct spec, no TestBed — a fake `ApplicationsAdapter` object passed straight to the functions.                                                                                                                                                                                             |
+| `apps/ssp/src/app/registratie/application/draft-sync.ts`              | Removed the inline `findConcept` closure and the body of `load`; both now call the free functions. `createDraftSync` keeps `id`, `ensuring`, `resumeGate`, and the whole write path, unchanged.                                                                                             |
+| `libs/shared/docs/behaviour-spec.mdx`                                 | Regenerated (`npm run gen:behaviour-spec`) — picks up the new `find-concept.spec.ts` describe blocks.                                                                                                                                                                                       |
+
+`createDraftSync` shrank from 187 lines (`export function createDraftSync` to its closing
+brace, HEAD~1) to 169 lines. The whole file went from 236 to 216 lines.
+
+The two call sites that used the old inline `findConcept()` now pass the adapter and type
+explicitly:
+
+```ts
+// ensureId's 409-recovery catch (WP-35)
+const existing = await findConcept(adapter, deps.type);
+```
+
+```ts
+// resume(), no ?aanvraag in the URL
+const existing = await findConcept(adapter, deps.type);
+```
+
+`load` keeps setting the closure `id` and calling `applyResume` (both closure-dependent), but
+delegates the actual read to `loadConcept`:
+
+```ts
+const load = (linked: string): Promise<void> => {
+  id = linked;
+  return loadConcept(adapter, linked).then((result) => {
+    if (result.tag === 'not-concept') {
+      id = undefined;
+      applyResume(null);
+      return;
+    }
+    applyResume(result.draft);
+  });
+};
+```
+
+## `draft-sync.spec.ts` — unchanged
+
+`draft-sync.spec.ts` was not edited. It never called `resume()`/`load()` directly — its
+coverage is the debounce, `submit()` (including the 409-recovery path, which exercises the
+extracted `findConcept` indirectly through `ensureId`'s catch), and `flushPending`. All of
+that stayed in `createDraftSync`, so the spec is unchanged and still exercises the wiring
+between `createDraftSync` and the two new free functions (the 409-recovery test would fail if
+that wiring were wrong). It passed unchanged, 8/8.
+
+## The new spec, and its verified red
+
+`find-concept.spec.ts` covers the branches CQ-001 named:
+
+- `findConcept`: match found → id returned; no match of that type → `undefined`; match found
+  but not `Concept` status → `undefined`; `adapter.list()` resolves to an unparsable shape
+  (`parseApplications` fails) → `undefined`; `adapter.list()` rejects → `undefined`.
+- `loadConcept`: `Concept` with a draft → `{tag:'concept', draft}`; `Concept` with no draft →
+  `{tag:'concept', draft:null}`; a non-`Concept` status (e.g. `Ingediend`, submitted) →
+  `{tag:'not-concept'}`; `adapter.detail()` rejects (unknown/deleted id) →
+  `{tag:'not-concept'}`.
+
+**Verified red without the fix.** Used `Edit` (not `git checkout`) to invert one condition in
+`loadConcept` — `dto.status.tag !== 'Concept'` → `dto.status.tag === 'Concept'` — reran `ng
+test ssp --include find-concept.spec.ts`. Result: 3 of 9 tests failed —
+
+```
+loadConcept > reads the draft off a Concept
+  AssertionError: expected { tag: 'not-concept' } to deeply equal { tag: 'concept', draft: { step: 1 } }
+loadConcept > reports a missing draft as null
+  AssertionError: expected { tag: 'not-concept' } to deeply equal { tag: 'concept', draft: null }
+loadConcept > reports not-concept when the id has moved past Concept (submitted)
+  AssertionError: expected { tag: 'concept', draft: null } to deeply equal { tag: 'not-concept' }
+```
+
+Then used `Edit` again to flip the condition back to `!==`, reran the same command: 9/9
+green. `findConcept`'s and `loadConcept`'s other branches were not separately mutated — the
+inverted condition alone was enough to prove the spec is sensitive to the extraction being
+correct, and re-verifying full green after the revert confirmed no collateral change was left
+in the file.
+
+## Scope held
+
+- No restructuring of the write path (`ensureId`, `flush`, `submit`, `reset`) — untouched
+  beyond the two call-site updates shown above.
+- `applications.adapter.ts` was not split (CQ-002's "Not filed" note rules that out for this
+  design; out of scope here regardless).
+- `resume()`'s semantics (URL-param precedence, the `resumeGate` release-in-`finally`, the
+  navigate-to-stamp-the-id side effect) are unchanged — only its two `findConcept()`/`load()`
+  calls now go through the free functions.
+- No wire change, no DTO change, no behaviour change.
+
+## Verification
+
+`npm run ci` (foreground): **green** — lint, typecheck, `dep:check`, `format:check`,
+`check:tokens`, `check:seam`, tests (ssp includes `find-concept.spec.ts` 9/9 new,
+`draft-sync.spec.ts` 8/8 unchanged), `ng build --localize` (both apps), `npm audit`, backend
+`dotnet test` (the known `OpenZaakIntegrationTests.Admin_cases_…` container-dependent failure
+is expected and outside `npm run ci`'s scope), `gen:snippets` drift clean, `gen:behaviour-spec`
+drift clean once the regenerated file is committed alongside the code. Full counts are in the
+commit's `npm run ci` run — see the session note for the exact step-by-step output.

libs/shared/docs/behaviour-spec.mdx

@@ -20,7 +20,7 @@ tested where._
 
 Every bullet below is a real test name from the suite — an `it()` title (frontend) or a test
 method name (backend), read as a sentence. Nothing here is hand-written prose: this page
-**is** the suite, reshaped for a business reader. 451 frontend behaviours across
+**is** the suite, reshaped for a business reader. 460 frontend behaviours across
 9 contexts; 236 backend behaviours across 41 test
 classes.
 
@@ -470,6 +470,14 @@ classes.
 - lists soort/waarvoor/status/referentie/ingediend, plus reason when rejected
 - reference falls back to em dash for a Concept
 
+#### findConcept
+
+- returns the id of the existing Concept of the given type
+- returns undefined when the list has no application of the given type
+- returns undefined when the matching type is not a Concept
+- returns undefined when adapter.list() resolves with an unparsable shape
+- returns undefined when adapter.list() rejects
+
 #### hasProgress
 
 - is false for a fresh wizard
@@ -486,6 +494,13 @@ classes.
 
 - derives the beroep from the chosen diploma and flags origin duo
 
+#### loadConcept
+
+- reads the draft off a Concept
+- reports a missing draft as null
+- reports not-concept when the id has moved past Concept (submitted)
+- reports not-concept when the id is unknown or deleted (detail rejects)
+
 #### manual diploma fallback
 
 - KiesHandmatig flags handmatig with the maximal question set and no beroep yet