diff --git a/server/src/nest/tours/tour-gpx-export.helpers.ts b/server/src/nest/tours/tour-gpx-export.helpers.ts
new file mode 100644
index 000000000..4fa9e4ba1
--- /dev/null
+++ b/server/src/nest/tours/tour-gpx-export.helpers.ts
@@ -0,0 +1,25 @@
+import type { BikeProfile, PaddleBoatType } from '@trek/shared';
+
+/** What GPX calls the activity in a track's <type>; a paddle tour says what it is paddled in. */
+const PADDLE_ACTIVITY: Record<PaddleBoatType, string> = {
+  kayak: 'kayaking',
+  canoe: 'canoeing',
+  sup: 'stand_up_paddling',
+  other: 'paddling',
+};
+
+/** A bike tour says what it is ridden on, in the words Garmin and Strava read. */
+const BIKE_ACTIVITY: Record<BikeProfile, string> = {
+  touring: 'cycling',
+  road: 'road_biking',
+  gravel: 'gravel_cycling',
+  mtb: 'mountain_biking',
+};
+
+/** The activity a tour's track names in GPX: a paddle tour its boat, a bike tour its profile, a hike hiking; whatever is missing falls back to the plainest. */
+export function gpxActivityOf(tour: { tour_type: string; boat_type?: string | null; bike_profile?: string | null }): string {
+  const { tour_type: type, boat_type: boat, bike_profile: bike } = tour;
+  if (type === 'kayak') return PADDLE_ACTIVITY[(boat ?? 'other') as PaddleBoatType] ?? PADDLE_ACTIVITY.other;
+  if (type === 'bike') return BIKE_ACTIVITY[(bike ?? 'touring') as BikeProfile] ?? BIKE_ACTIVITY.touring;
+  return type === 'hike' ? 'hiking' : type;
+}
diff --git a/server/src/nest/tours/tour-gpx-export.service.ts b/server/src/nest/tours/tour-gpx-export.service.ts
index a25551447..0b4902ca2 100644
--- a/server/src/nest/tours/tour-gpx-export.service.ts
+++ b/server/src/nest/tours/tour-gpx-export.service.ts
@@ -7,32 +7,9 @@ import type { ToursRepository } from '../../db/repositories/Tours.repository';
 import { DomainError } from '../common/domain-error';
 import { toRowId } from '../common/row-id';
 import { PlaceImportService } from '../place-import/place-import.service';
+import { gpxActivityOf } from './tour-gpx-export.helpers';
 import { InjectRepository } from '@mikro-orm/nestjs';
 import { Injectable, NotFoundException } from '@nestjs/common';
-import type { BikeProfile, PaddleBoatType } from '@trek/shared';
-
-/** What GPX calls the activity in a track's <type>; a paddle tour says what it is paddled in. */
-const PADDLE_ACTIVITY: Record<PaddleBoatType, string> = {
-  kayak: 'kayaking',
-  canoe: 'canoeing',
-  sup: 'stand_up_paddling',
-  other: 'paddling',
-};
-
-/** A bike tour says what it is ridden on, in the words Garmin and Strava read. */
-const BIKE_ACTIVITY: Record<BikeProfile, string> = {
-  touring: 'cycling',
-  road: 'road_biking',
-  gravel: 'gravel_cycling',
-  mtb: 'mountain_biking',
-};
-
-function gpxActivityOf(tour: { tour_type: string; boat_type?: string | null; bike_profile?: string | null }): string {
-  const { tour_type: type, boat_type: boat, bike_profile: bike } = tour;
-  if (type === 'kayak') return PADDLE_ACTIVITY[(boat ?? 'other') as PaddleBoatType] ?? PADDLE_ACTIVITY.other;
-  if (type === 'bike') return BIKE_ACTIVITY[(bike ?? 'touring') as BikeProfile] ?? BIKE_ACTIVITY.touring;
-  return type === 'hike' ? 'hiking' : type;
-}
 
 /**
  * PR1-06A: one saved tour as a GPX file, its whole saved line with the heights
diff --git a/server/src/nest/tours/tour-trail-grade.service.ts b/server/src/nest/tours/tour-trail-grade.service.ts
index 3591373a9..575f9e9b8 100644
--- a/server/src/nest/tours/tour-trail-grade.service.ts
+++ b/server/src/nest/tours/tour-trail-grade.service.ts
@@ -21,7 +21,7 @@ const wayElementSchema = z.object({
 function step(value: string | undefined, top: number, signed: boolean): string | null {
   const match = /^\s*S?([0-9])([+-])?\s*$/i.exec(value ?? '');
   if (!match || Number(match[1]) > top) return null;
-  return signed ? `${match[1]}${match[2] ?? ''}` : (match[1] ?? null);
+  return signed ? `${match[1]}${match[2] ?? ''}` : match[1];
 }
 
 function gradeOf(id: number, tags: Record<string, string> = {}): TourTrailGrade | null {
diff --git a/server/tests/unit/nest/tour-gpx-export.helpers.test.ts b/server/tests/unit/nest/tour-gpx-export.helpers.test.ts
new file mode 100644
index 000000000..d49286c01
--- /dev/null
+++ b/server/tests/unit/nest/tour-gpx-export.helpers.test.ts
@@ -0,0 +1,24 @@
+import { gpxActivityOf } from '../../../src/nest/tours/tour-gpx-export.helpers';
+
+import { describe, expect, it } from 'vitest';
+
+// TOUR-GPX-ACTIVITY-001 to TOUR-GPX-ACTIVITY-003
+
+describe('gpxActivityOf (PR1-06A, BIK-01)', () => {
+  it('TOUR-GPX-ACTIVITY-001: a bike tour names its profile, and the plainest riding without a known one', () => {
+    expect(gpxActivityOf({ tour_type: 'bike', bike_profile: 'mtb' })).toBe('mountain_biking');
+    expect(gpxActivityOf({ tour_type: 'bike', bike_profile: null })).toBe('cycling');
+    expect(gpxActivityOf({ tour_type: 'bike', bike_profile: 'unicycle' })).toBe('cycling');
+  });
+
+  it('TOUR-GPX-ACTIVITY-002: a paddle tour names its boat, and paddling without a known one', () => {
+    expect(gpxActivityOf({ tour_type: 'kayak', boat_type: 'canoe' })).toBe('canoeing');
+    expect(gpxActivityOf({ tour_type: 'kayak', boat_type: null })).toBe('paddling');
+    expect(gpxActivityOf({ tour_type: 'kayak', boat_type: 'raft' })).toBe('paddling');
+  });
+
+  it('TOUR-GPX-ACTIVITY-003: a hike is hiking, any other type its own key', () => {
+    expect(gpxActivityOf({ tour_type: 'hike' })).toBe('hiking');
+    expect(gpxActivityOf({ tour_type: 'walk' })).toBe('walk');
+  });
+});
diff --git a/server/tests/unit/nest/tour-trail-grade.service.test.ts b/server/tests/unit/nest/tour-trail-grade.service.test.ts
index 28eac0982..ac787db3e 100644
--- a/server/tests/unit/nest/tour-trail-grade.service.test.ts
+++ b/server/tests/unit/nest/tour-trail-grade.service.test.ts
@@ -4,7 +4,7 @@ import { Test } from '@nestjs/testing';
 
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 
-// TOUR-GRADE-001 to TOUR-GRADE-005
+// TOUR-GRADE-001 to TOUR-GRADE-006
 
 const query = vi.fn<(q: string, caller: string) => Promise<unknown[]>>();
 let service: TourTrailGradeService;
@@ -75,4 +75,19 @@ describe('TourTrailGradeService (BIK-05)', () => {
     query.mockResolvedValue([{ type: 'node', id: 1, tags: { 'mtb:scale': '1' } }, { nonsense: true }]);
     expect(await service.grades({ way_ids: [1] })).toEqual({ ways: [], unanswered: [] });
   });
+
+  it('TOUR-GRADE-006: keeps at most fifty thousand ways, forgetting the longest kept first', async () => {
+    query.mockResolvedValue([]);
+    for (let part = 0; part < 26; part += 1) {
+      const ids = Array.from({ length: 2000 }, (_, index) => part * 2000 + index + 1);
+      await service.grades({ way_ids: ids });
+    }
+    query.mockClear();
+    // The first way was forgotten, so it is asked about again; the last one is still kept.
+    await service.grades({ way_ids: [1] });
+    expect(query).toHaveBeenCalledTimes(1);
+    query.mockClear();
+    await service.grades({ way_ids: [52_000] });
+    expect(query).not.toHaveBeenCalled();
+  });
 });