docs: document form autosave + FE↔BE request lifecycle in ARCHITECTURE

New §2g explains field persistence (keystroke → model → 600ms snapshot
debounce; blur only marks touched, never saves) and §6a refreshes the stale
backend section with the real request lifecycle (NSwag client, httpClientFetch
seam, read/write traces) — both with relative links to the source files.
Add discovery pointers from the learning path (lesson 2.2 and the capstone).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/reference/architecture/ARCHITECTURE.md

@@ -333,6 +333,39 @@ stores the result. The route guard (`auth/auth.guard.ts`) just reads
 `store.isAuthenticated()` and redirects to `/login` if you're not signed in.
 Protected routes list `canActivate: [authGuard]` in `app.routes.ts`.
 
+### 2g. Autosave — keystroke → model → debounced sync (not on blur)
+
+A common assumption is "the form saves on blur." It doesn't. **Blur only marks a field
+_touched_** so validation can show; it never writes the value or hits the network. In the
+shared atoms, `(blur)="onTouched()"` is the `ControlValueAccessor` touched callback and
+nothing more; the value is pushed on `(input)`, every keystroke
+([`text-input.component.ts`](../../../src/app/shared/ui/text-input/text-input.component.ts):
+`(input)` L29 → `onChange` L62, vs `(blur)="onTouched()"` L30).
+
+The real flow has two stages, neither keyed on focus:
+
+1. **Keystroke → Model.** A field binds `(ngModelChange)`/`(input)` and dispatches
+   `{ tag: 'SetField', key, value }`. The pure reducer stores it immediately — so the
+   Model is always current, on every keystroke, while editing.
+   ([`herregistratie-wizard.component.ts`](../../../src/app/herregistratie/ui/herregistratie-wizard/herregistratie-wizard.component.ts)
+   L78 → [`herregistratie.machine.ts`](../../../src/app/herregistratie/domain/herregistratie.machine.ts)
+   L138-142, `setField`.)
+2. **Model → backend (600 ms debounce).** A signal `effect` tracks the machine
+   `snapshot()`; each change resets a 600 ms timer whose callback does I/O **only** (it
+   never dispatches, so it can't livelock the store). On the first save it lazily creates
+   the application and stamps `?aanvraag=<id>` into the URL, so a reload resumes the draft.
+   ([`draft-sync.ts`](../../../src/app/registratie/application/draft-sync.ts):
+   `DEBOUNCE_MS` L34, `effect` L102-108, `flush` L88-98 → `ApplicationsAdapter.syncDraft`.)
+
+The **brief** context uses the same 600 ms idiom in its own store: `edit()` applies the
+edit optimistically in the reducer and records an undo step, then `scheduleSave()` →
+`flushSave()` flips a `saveState` (Saving/Saved/Error) and calls `adapter.save`
+([`brief.store.ts`](../../../src/app/brief/application/brief.store.ts) L157-166, L192-209).
+
+So it _feels_ like save-on-blur only because you usually stop typing when you leave a
+field, and the debounce fires ~600 ms later. The trigger is **"stopped changing," not
+"lost focus."** Submit is a separate, explicit action (§2d).
+
 ---
 
 ## 3. "Parse, don't validate" — value objects
@@ -469,6 +502,50 @@ Practical notes, kept lazy:
   single place the wire format meets our types.
 - Nothing else moves: `<app-async>`, the stores, and every page keep working unchanged.
 
+### 6a. The request lifecycle today
+
+The sketch above is the _rationale_; the shipped shape has since firmed up. The contract is
+no longer hand-written DTOs — it's an **NSwag-generated typed client**
+([`api-client.ts`](../../../src/app/shared/infrastructure/api-client.ts), regenerate with
+`npm run gen:api` per [`nswag.json`](../../../nswag.json)) — and the boundary is a
+`parse*` returning `Result` rather than `httpResource({ parse })`. End to end:
+
+- **Proxy.** The app uses a relative base URL (`apiBaseUrl: ''`), so `/api` calls are
+  same-origin and `ng serve` proxies them to the backend on `:5000`.
+  ([`environment.ts`](../../../src/environments/environment.ts),
+  [`proxy.conf.json`](../../../proxy.conf.json); `proxy.conf.docker.json` targets the
+  compose service.)
+- **Client → HttpClient seam.** The NSwag client's `fetch` is routed through Angular's
+  `HttpClient` by `httpClientFetch` — the one place cross-cutting concerns live:
+  `X-Correlation-Id` on every call, `Idempotency-Key` on non-GETs, a 10 s timeout, and
+  GET-only retry. Routing through `HttpClient` is exactly what lets the interceptors see API
+  traffic. ([`api-client.provider.ts`](../../../src/app/shared/infrastructure/api-client.provider.ts):
+  `httpClientFetch` L47-82, `provideApiClient` L86-92; registered in
+  [`app.config.ts`](../../../src/app/app.config.ts) L37.)
+- **Interceptors (dev-only, stripped in prod).** `scenario.interceptor.ts` (the `?scenario=`
+  toggle) and `role.interceptor.ts` (`X-Role` on role-aware endpoints).
+
+**A read (dashboard):** `<app-async [data]="store.profile()">` →
+[`BigProfileStore`](../../../src/app/registratie/application/big-profile.store.ts) →
+`DashboardViewAdapter.dashboardViewResource()` = `resource({ loader: () =>
+client.dashboardView() })`
+([`dashboard-view.adapter.ts`](../../../src/app/registratie/infrastructure/dashboard-view.adapter.ts))
+→ GET `/api/v1/dashboard-view` → `httpClientFetch` → proxy → backend → back through the
+`parseDashboardView(json): Result` trust boundary → `RemoteData<DashboardView>` → rendered.
+
+**A write (change address):** `runIfSubmitting()` (§2d) → `createSubmitChangeRequest`
+([`submit-change-request.ts`](../../../src/app/registratie/application/submit-change-request.ts))
+→ `runSubmit` — the one try/catch that mints the `Idempotency-Key` and maps RFC-7807
+ProblemDetails → string ([`submit.ts`](../../../src/app/shared/application/submit.ts)) →
+[`change-request.adapter.ts`](../../../src/app/registratie/infrastructure/change-request.adapter.ts)
+→ POST `/api/v1/change-requests` → `ok(referentie)` / `err(detail)` → dispatch
+`SubmitConfirmed` / `SubmitFailed`.
+
+**Backend.** A single minimal-API host computes business decisions server-side (BFF-lite),
+returns ProblemDetails on rule rejection, and dedupes replays via `Idempotency-Key`
+([`Program.cs`](../../../backend/src/BigRegister.Api/Program.cs): `/dashboard-view` L80,
+`/change-requests` L120).
+
 ---
 
 ## 7. Mini-glossary

src/docs/learning-path.mdx

@@ -153,6 +153,11 @@ the *outcome*. Reducer = "what the new state is"; command = "go do it, then say
 happened." And **derive, don't store** anything you can compute — e.g. a wizard's visible
 steps are `visibleSteps(answers)`, not a stored field.
 
+A field's value lands in the Model on **every keystroke** (not on blur — blur only marks
+the field "touched"); a separate 600 ms debounce off the model snapshot autosaves the
+draft to the backend, an effect that lives *outside* the reducer. See
+`docs/reference/architecture/ARCHITECTURE.md` §2g.
+
 **Do:** run `/form-machine` for a toy single field (say a "nickname" field with a max
 length). Read the generated Model / Msg / reduce and its spec.
 
@@ -359,7 +364,8 @@ one is the **authority**?
 
 **Go deeper:** `docs/reference/architecture/0001-bff-lite-decision-dtos.md`;
 `docs/reference/fp-tea-atomic-design.md` Part 7 (the copy-paste recipes);
-`docs/reference/architecture/ARCHITECTURE.md` §4. For how contexts scale to a second
+`docs/reference/architecture/ARCHITECTURE.md` §4 (the recipe) and §6a (the full FE⇄BE
+request lifecycle, read + write, with file links). For how contexts scale to a second
 app and actor-based authorization, ADR-0002 (the advanced read).
 
 ---