diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index bd3630fdf..6ed841d9b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -458,7 +458,10 @@ jobs:
         # tsconfig.strict.json is the same program with strictNullChecks and
         # noImplicitAny; its errors per file may not rise above
         # scripts/strict-baseline.json, and a file without an entry, every new
-        # one included, has to be clean (scripts/strict-lint.mjs).
+        # one included, has to be clean (scripts/strict-lint.mjs). It holds the
+        # whole program with strict checks, past Node's default ~4 GB heap.
+        env:
+          NODE_OPTIONS: --max-old-space-size=8192
         run: cd client && npm run lint:strict
 
       - name: Page pattern check
diff --git a/client/src/api/mailIngest.test.ts b/client/src/api/mailIngest.test.ts
new file mode 100644
index 000000000..425b3997e
--- /dev/null
+++ b/client/src/api/mailIngest.test.ts
@@ -0,0 +1,21 @@
+// FE-MAILINGEST-API-001
+import { describe, expect, it, vi } from 'vitest';
+
+vi.mock('./client', () => ({
+  default: { get: vi.fn(), post: vi.fn(), patch: vi.fn(), put: vi.fn(), delete: vi.fn() },
+  postMultipart: vi.fn(async () => ({ duplicate: false })),
+}));
+
+import apiClient, { postMultipart } from './client';
+import { mailIngestApi } from './mailIngest';
+
+describe('mailIngestApi.upload', () => {
+  it('FE-MAILINGEST-API-001: sends the .eml as a multipart form, never through the JSON post', async () => {
+    const file = new File(['From: a@b.c\r\n\r\nhi'], 'booking.eml', { type: 'message/rfc822' });
+    expect(await mailIngestApi.upload(file)).toEqual({ duplicate: false });
+    const [url, form] = vi.mocked(postMultipart).mock.calls[0];
+    expect(url).toBe('/mail-ingest/upload');
+    expect((form as FormData).get('file')).toBe(file);
+    expect(apiClient.post).not.toHaveBeenCalled();
+  });
+});
diff --git a/client/src/api/mailIngest.ts b/client/src/api/mailIngest.ts
index 321ba22df..92787e3ac 100644
--- a/client/src/api/mailIngest.ts
+++ b/client/src/api/mailIngest.ts
@@ -1,4 +1,4 @@
-import apiClient from './client';
+import apiClient, { postMultipart } from './client';
 
 /**
  * The booking mail import (server nest/mail-ingest): the person's settings and
@@ -43,6 +43,7 @@ export const mailIngestApi = {
   upload: (file: File): Promise<unknown> => {
     const form = new FormData();
     form.append('file', file);
-    return apiClient.post('/mail-ingest/upload', form).then(data);
+    // As multipart: under the client's default JSON content type the form went as JSON, without the file.
+    return postMultipart('/mail-ingest/upload', form);
   },
 };
diff --git a/server/src/nest/booking-import/booking-import.service.ts b/server/src/nest/booking-import/booking-import.service.ts
index f8205563f..089340dfe 100644
--- a/server/src/nest/booking-import/booking-import.service.ts
+++ b/server/src/nest/booking-import/booking-import.service.ts
@@ -14,7 +14,7 @@ import { McpToolGuardsService } from '../mcp-shared/mcp-tool-guards.service';
 import { PlaceOriginsService } from '../places/place-origins.service';
 import { PlacesService } from '../places/places.service';
 import { RealtimeService } from '../realtime/realtime.service';
-import { withoutOrigin } from '../reservations/reservation-origin';
+import { withoutOrigin } from '../reservations/reservation-origin.contract';
 import { ReservationsService, type CreateAccommodation } from '../reservations/reservations.service';
 import { IMPORT_SOURCE, importExternalId } from './booking-origin';
 import { KitineraryExtractorService } from './kitinerary-extractor.service';
diff --git a/server/src/nest/reservations/reservation-inputs.ts b/server/src/nest/reservations/reservation-inputs.ts
index 3244ebf23..6b480103e 100644
--- a/server/src/nest/reservations/reservation-inputs.ts
+++ b/server/src/nest/reservations/reservation-inputs.ts
@@ -1,4 +1,4 @@
-import type { ReservationOrigin } from './reservation-origin';
+import type { ReservationOrigin } from './reservation-origin.contract';
 
 /*
  * The shapes the reservations service takes in: a booking's endpoints, the
diff --git a/server/src/nest/reservations/reservation-origin.ts b/server/src/nest/reservations/reservation-origin.contract.ts
similarity index 86%
rename from server/src/nest/reservations/reservation-origin.ts
rename to server/src/nest/reservations/reservation-origin.contract.ts
index 7c198c29c..dcd80da4a 100644
--- a/server/src/nest/reservations/reservation-origin.ts
+++ b/server/src/nest/reservations/reservation-origin.contract.ts
@@ -1,3 +1,9 @@
+/*
+ * The origin an imported booking carries, published by the reservations
+ * domain: the importers (booking import, mail import) set it, and every other
+ * write path strips it from what a client sends.
+ */
+
 /**
  * Where an imported booking came from (`import`, `mail`) and its key there,
  * unique per trip. Both or neither; without them the row is a hand-made
diff --git a/server/src/nest/reservations/reservations.controller.ts b/server/src/nest/reservations/reservations.controller.ts
index 3ff8c240e..63a09784f 100644
--- a/server/src/nest/reservations/reservations.controller.ts
+++ b/server/src/nest/reservations/reservations.controller.ts
@@ -2,7 +2,7 @@ import type { User } from '../../types';
 import { CurrentUser } from '../auth-core/current-user.decorator';
 import { JwtAuthGuard } from '../auth-core/jwt-auth.guard';
 import { RequirePermission, TripAccessGuard } from '../permissions/trip-access.guard';
-import { withoutOrigin } from './reservation-origin';
+import { withoutOrigin } from './reservation-origin.contract';
 import { ReservationWritesService } from './reservation-writes.service';
 import {
   ReservationCreateDto,
diff --git a/server/src/nest/reservations/reservations.rpc.ts b/server/src/nest/reservations/reservations.rpc.ts
index fcec9cb3b..a6506a242 100644
--- a/server/src/nest/reservations/reservations.rpc.ts
+++ b/server/src/nest/reservations/reservations.rpc.ts
@@ -4,7 +4,7 @@ import { PluginController, PluginMethod } from '../../nest-rpc/rpc-kit/decorator
 import type { PluginRpcContext } from '../../nest-rpc/rpc-kit/types';
 import { num, schemaMessage } from '../../nest-rpc/rpc-params';
 import { RealtimeService } from '../realtime/realtime.service';
-import { withoutOrigin } from './reservation-origin';
+import { withoutOrigin } from './reservation-origin.contract';
 import { ReservationsService } from './reservations.service';
 import {
   reservationCreateRequestSchema,
diff --git a/server/src/nest/reservations/reservations.service.ts b/server/src/nest/reservations/reservations.service.ts
index e6ed8f2a7..e3cf0205c 100644
--- a/server/src/nest/reservations/reservations.service.ts
+++ b/server/src/nest/reservations/reservations.service.ts
@@ -1,4 +1,4 @@
-import { originColumns } from './reservation-origin';
+import { originColumns } from './reservation-origin.contract';
 import type { CreateAccommodation, CreateReservationData, EndpointInput, ReservationEndpoint, UpdateReservationData } from './reservation-inputs';
 export type { CreateAccommodation, CreateReservationData, EndpointInput, ReservationEndpoint, UpdateReservationData } from './reservation-inputs';
 import { BadRequestException, Injectable } from '@nestjs/common';
diff --git a/server/tests/unit/nest/reservations.service.test.ts b/server/tests/unit/nest/reservations.service.test.ts
index af6c62379..15e5fb370 100644
--- a/server/tests/unit/nest/reservations.service.test.ts
+++ b/server/tests/unit/nest/reservations.service.test.ts
@@ -33,7 +33,7 @@ import { HttpException } from '@nestjs/common';
 import { resetTestDb } from '../../helpers/test-db';
 import { createUser, createTrip, createReservation, createBudgetItem, createPlace, createDay, createDayAccommodation, createDayAssignment, addTripMember } from '../../helpers/factories';
 import type { PermissionsService } from '../../../src/nest/permissions/permissions.service';
-import { withoutOrigin } from '../../../src/nest/reservations/reservation-origin';
+import { withoutOrigin } from '../../../src/nest/reservations/reservation-origin.contract';
 import { ReservationsService, type UpdateReservationData } from '../../../src/nest/reservations/reservations.service';
 import { ReservationsReadService } from '../../../src/nest/reservations/reservations-read.service';
 import type { BudgetService } from '../../../src/nest/budget/budget.service';