diff --git a/apps/app/src/composables/api/useTimetableMutations.ts b/apps/app/src/composables/api/useTimetableMutations.ts
index 0adef797..8a65913c 100644
--- a/apps/app/src/composables/api/useTimetableMutations.ts
+++ b/apps/app/src/composables/api/useTimetableMutations.ts
@@ -126,15 +126,16 @@ export function useTimetableMutations(args: UseTimetableMutationsArgs) {
       }
       catch (err) {
         if (isVersionMismatch(err)) {
-          throw {
-            status: 409,
-            conflict: err.response.data.errors,
-          } as VersionMismatchError
+          const mismatch = new Error('version_mismatch') as Error & VersionMismatchError
+
+          mismatch.status = 409
+          mismatch.conflict = err.response.data.errors
+          throw mismatch
         }
-        throw {
-          status: (err as AxiosError).response?.status ?? 0,
-          message: (err as AxiosError).message,
-        } as { status: number; message: string }
+        const wrapped = new Error((err as AxiosError).message) as Error & { status: number; message: string }
+
+        wrapped.status = (err as AxiosError).response?.status ?? 0
+        throw wrapped
       }
     },
     onMutate: async ({ optimistic }) => {
diff --git a/apps/app/tests/unit/composables/useDragOrClick.test.ts b/apps/app/tests/unit/composables/useDragOrClick.test.ts
new file mode 100644
index 00000000..4c023352
--- /dev/null
+++ b/apps/app/tests/unit/composables/useDragOrClick.test.ts
@@ -0,0 +1,77 @@
+import { mount } from '@vue/test-utils'
+import { describe, expect, it, vi } from 'vitest'
+import { defineComponent, h } from 'vue'
+import { useDragOrClick } from '@/composables/timetable/useDragOrClick'
+
+interface ComponentInstance {
+  begin: (e: Event) => void
+}
+
+function makeHost(opts: Parameters<typeof useDragOrClick>[0]) {
+  return defineComponent({
+    setup(_, { expose }) {
+      const ctl = useDragOrClick(opts)
+
+      expose({ begin: ctl.begin })
+
+      return () => h('div')
+    },
+  })
+}
+
+function makePointerEvent(type: string, x: number, y: number, pointerId = 1): PointerEvent {
+  const e = new Event(type, { bubbles: true, cancelable: true }) as PointerEvent
+
+  Object.defineProperty(e, 'pointerId', { value: pointerId })
+  Object.defineProperty(e, 'clientX', { value: x })
+  Object.defineProperty(e, 'clientY', { value: y })
+
+  return e
+}
+
+describe('useDragOrClick', () => {
+  it('fires onClick when movement < threshold', async () => {
+    const onClick = vi.fn()
+    const onDragStart = vi.fn()
+    const wrapper = mount(makeHost({ thresholdPx: 4, onClick, onDragStart }))
+    const inst = wrapper.vm as unknown as ComponentInstance
+
+    inst.begin(makePointerEvent('pointerdown', 10, 10))
+    window.dispatchEvent(makePointerEvent('pointermove', 11, 11))
+    window.dispatchEvent(makePointerEvent('pointerup', 11, 11))
+
+    expect(onClick).toHaveBeenCalledTimes(1)
+    expect(onDragStart).not.toHaveBeenCalled()
+  })
+
+  it('enters drag mode and emits onDragStart + onDragEnd when movement crosses threshold', async () => {
+    const onClick = vi.fn()
+    const onDragStart = vi.fn()
+    const onDragEnd = vi.fn()
+    const wrapper = mount(makeHost({ thresholdPx: 4, onClick, onDragStart, onDragEnd }))
+    const inst = wrapper.vm as unknown as ComponentInstance
+
+    inst.begin(makePointerEvent('pointerdown', 10, 10))
+    window.dispatchEvent(makePointerEvent('pointermove', 50, 10))
+    window.dispatchEvent(makePointerEvent('pointerup', 50, 10))
+
+    expect(onDragStart).toHaveBeenCalledTimes(1)
+    expect(onDragEnd).toHaveBeenCalledTimes(1)
+    expect(onClick).not.toHaveBeenCalled()
+  })
+
+  it('Esc cancels an in-flight drag', async () => {
+    const onDragEnd = vi.fn()
+    const wrapper = mount(makeHost({ thresholdPx: 4, onDragEnd }))
+    const inst = wrapper.vm as unknown as ComponentInstance
+
+    inst.begin(makePointerEvent('pointerdown', 10, 10))
+    window.dispatchEvent(makePointerEvent('pointermove', 50, 10))
+
+    const esc = new KeyboardEvent('keydown', { key: 'Escape' })
+
+    window.dispatchEvent(esc)
+
+    expect(onDragEnd).toHaveBeenCalledWith(expect.anything(), true)
+  })
+})
diff --git a/apps/app/tests/unit/composables/useTimetableMutations.test.ts b/apps/app/tests/unit/composables/useTimetableMutations.test.ts
new file mode 100644
index 00000000..7e4f2e3e
--- /dev/null
+++ b/apps/app/tests/unit/composables/useTimetableMutations.test.ts
@@ -0,0 +1,201 @@
+import { QueryClient, VueQueryPlugin } from '@tanstack/vue-query'
+import { mount } from '@vue/test-utils'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { defineComponent, h, ref } from 'vue'
+import { apiClient } from '@/lib/axios'
+import { useTimetableMutations } from '@/composables/api/useTimetableMutations'
+import type { Performance } from '@/types/timetable'
+
+vi.mock('@/lib/axios', () => {
+  const post = vi.fn()
+  const put = vi.fn()
+  const get = vi.fn()
+  const del = vi.fn()
+
+  return { apiClient: { post, put, get, delete: del } }
+})
+
+interface MockApi {
+  post: ReturnType<typeof vi.fn>
+  put: ReturnType<typeof vi.fn>
+  get: ReturnType<typeof vi.fn>
+  delete: ReturnType<typeof vi.fn>
+}
+
+const mocked = apiClient as unknown as MockApi
+
+function p(overrides: Partial<Performance> = {}): Performance {
+  return {
+    id: 'p1',
+    engagement_id: 'e1',
+    event_id: 'ev1',
+    stage_id: 's1',
+    lane: 0,
+    lane_resolved: 0,
+    start_at: '2026-07-10T18:00:00.000Z',
+    end_at: '2026-07-10T19:00:00.000Z',
+    version: 3,
+    notes: null,
+    warnings: [],
+    created_at: null,
+    updated_at: null,
+    deleted_at: null,
+    ...overrides,
+  }
+}
+
+function mountWithMutations() {
+  const api: { value: ReturnType<typeof useTimetableMutations> | null } = { value: null }
+  const orgId = ref('org_1')
+  const eventId = ref('ev_1')
+  const dayId = ref<string | null>('day_1')
+
+  const Host = defineComponent({
+    setup() {
+      api.value = useTimetableMutations({ orgId, eventId, dayId })
+
+      return () => h('div')
+    },
+  })
+
+  const queryClient = new QueryClient({ defaultOptions: { queries: { retry: false }, mutations: { retry: false } } })
+
+  const wrapper = mount(Host, {
+    global: { plugins: [[VueQueryPlugin, { queryClient }]] },
+  })
+
+  return { wrapper, api, queryClient }
+}
+
+describe('useTimetableMutations', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  describe('move', () => {
+    it('sends Idempotency-Key header on POST /timetable/move', async () => {
+      mocked.post.mockResolvedValueOnce({ data: { success: true, data: { moved: p({ version: 4 }), cascaded: [] } } })
+
+      const { api } = mountWithMutations()
+
+      await api.value!.move.mutateAsync({
+        payload: {
+          performance_id: 'p1',
+          target_stage_id: 's1',
+          target_start_at: '2026-07-10 19:00:00',
+          target_end_at: '2026-07-10 20:00:00',
+          target_lane: 0,
+          version: 3,
+        },
+        idempotencyKey: 'idem-test-key-12345',
+      })
+
+      expect(mocked.post).toHaveBeenCalledTimes(1)
+
+      const [, , config] = mocked.post.mock.calls[0]
+
+      expect(config.headers['Idempotency-Key']).toBe('idem-test-key-12345')
+    })
+
+    it('applies optimistic patch + cascade on success', async () => {
+      mocked.post.mockResolvedValueOnce({
+        data: {
+          success: true,
+          data: {
+            moved: p({ id: 'p1', version: 4 }),
+            cascaded: [p({ id: 'p2', lane: 1, lane_resolved: 1, version: 4 })],
+          },
+        },
+      })
+
+      const { api, queryClient } = mountWithMutations()
+      const eventId = ref('ev_1')
+      const dayId = ref<string | null>('day_1')
+
+      queryClient.setQueryData(['timetable', 'performances', eventId, dayId], [
+        p({ id: 'p1' }),
+        p({ id: 'p2', lane: 0, lane_resolved: 0 }),
+      ])
+
+      const result = await api.value!.move.mutateAsync({
+        payload: {
+          performance_id: 'p1',
+          target_stage_id: 's1',
+          target_start_at: '2026-07-10 19:00:00',
+          target_end_at: '2026-07-10 20:00:00',
+          target_lane: 0,
+          version: 3,
+        },
+        idempotencyKey: 'idem',
+      })
+
+      expect(result.cascaded).toHaveLength(1)
+      expect(result.moved.version).toBe(4)
+    })
+
+    it('surfaces VersionMismatch on 409', async () => {
+      mocked.post.mockRejectedValueOnce({
+        response: {
+          status: 409,
+          data: {
+            errors: {
+              conflict: 'version_mismatch',
+              current_version: 5,
+              client_version: 3,
+              server_data: p({ version: 5 }),
+            },
+          },
+        },
+      })
+
+      const { api } = mountWithMutations()
+
+      await expect(api.value!.move.mutateAsync({
+        payload: {
+          performance_id: 'p1',
+          target_stage_id: 's1',
+          target_start_at: '2026-07-10 19:00:00',
+          target_end_at: '2026-07-10 20:00:00',
+          target_lane: 0,
+          version: 3,
+        },
+        idempotencyKey: 'idem',
+      })).rejects.toMatchObject({ status: 409, conflict: { conflict: 'version_mismatch', current_version: 5 } })
+    })
+  })
+
+  describe('park / unpark via move', () => {
+    it('park sends target_stage_id null', async () => {
+      mocked.post.mockResolvedValueOnce({
+        data: { success: true, data: { moved: p({ stage_id: null, version: 4 }), cascaded: [] } },
+      })
+
+      const { api } = mountWithMutations()
+
+      await api.value!.park(p(), 'key1')
+
+      const [, body] = mocked.post.mock.calls[0]
+
+      expect(body.target_stage_id).toBe(null)
+      expect(body.version).toBe(3)
+    })
+  })
+
+  describe('createStage', () => {
+    it('hits POST /stages', async () => {
+      mocked.post.mockResolvedValueOnce({
+        data: { success: true, data: { id: 's2', name: 'New Stage', color: '#aabbcc', capacity: 1000, sort_order: 1, event_id: 'ev_1' } },
+      })
+
+      const { api } = mountWithMutations()
+
+      await api.value!.createStage.mutateAsync({ name: 'New Stage', color: '#aabbcc', capacity: 1000 })
+
+      expect(mocked.post.mock.calls[0][0]).toContain('/stages')
+    })
+  })
+})
diff --git a/apps/app/tests/unit/lib/idempotencyKey.test.ts b/apps/app/tests/unit/lib/idempotencyKey.test.ts
new file mode 100644
index 00000000..ce43b161
--- /dev/null
+++ b/apps/app/tests/unit/lib/idempotencyKey.test.ts
@@ -0,0 +1,24 @@
+import { describe, expect, it } from 'vitest'
+import { generateIdempotencyKey } from '@/lib/idempotencyKey'
+
+describe('generateIdempotencyKey', () => {
+  it('returns a string within the backend 6..30 char range', () => {
+    const key = generateIdempotencyKey()
+
+    expect(key.length).toBeGreaterThanOrEqual(6)
+    expect(key.length).toBeLessThanOrEqual(30)
+  })
+
+  it('produces 24-hex output when crypto.randomUUID is available', () => {
+    const key = generateIdempotencyKey()
+
+    expect(key).toMatch(/^[0-9a-f]{24}$/)
+  })
+
+  it('successive calls return different values (very high probability)', () => {
+    const a = generateIdempotencyKey()
+    const b = generateIdempotencyKey()
+
+    expect(a).not.toBe(b)
+  })
+})
diff --git a/apps/app/tests/unit/lib/timetable/b2b.test.ts b/apps/app/tests/unit/lib/timetable/b2b.test.ts
new file mode 100644
index 00000000..1026ab6a
--- /dev/null
+++ b/apps/app/tests/unit/lib/timetable/b2b.test.ts
@@ -0,0 +1,84 @@
+import { describe, expect, it } from 'vitest'
+import { B2B_THRESHOLD_MIN, findB2BLinks, findB2BSides } from '@/lib/timetable/b2b'
+import type { Performance } from '@/types/timetable'
+
+function p(overrides: Partial<Performance> = {}): Performance {
+  return {
+    id: 'p1',
+    engagement_id: 'e1',
+    event_id: 'ev1',
+    stage_id: 's1',
+    lane: 0,
+    lane_resolved: 0,
+    start_at: '2026-07-10T18:00:00.000Z',
+    end_at: '2026-07-10T19:00:00.000Z',
+    version: 0,
+    notes: null,
+    warnings: [],
+    created_at: null,
+    updated_at: null,
+    deleted_at: null,
+    ...overrides,
+  }
+}
+
+describe('findB2BLinks', () => {
+  it('returns empty when no consecutive pair exists', () => {
+    expect(findB2BLinks([p({ id: 'a' })])).toEqual([])
+  })
+
+  it('marks 0-min gap as B2B', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:00:00Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(links).toHaveLength(1)
+    expect(links[0]).toEqual({ leftId: 'a', rightId: 'b', gapMin: 0 })
+  })
+
+  it('marks 2:59 gap as B2B (under 3-min threshold)', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:02:59Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(links).toHaveLength(1)
+  })
+
+  it('does NOT mark 3:01 gap as B2B', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:03:01Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(links).toHaveLength(0)
+  })
+
+  it('overlap (negative gap) is NOT a B2B link', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T18:30:00Z', end_at: '2026-07-10T19:30:00Z' }),
+    ])
+
+    expect(links).toHaveLength(0)
+  })
+
+  it('threshold constant is 3 minutes', () => {
+    expect(B2B_THRESHOLD_MIN).toBe(3)
+  })
+})
+
+describe('findB2BSides', () => {
+  it('produces left+right sets reflecting neighbour position', () => {
+    const { leftSet, rightSet } = findB2BSides([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:00:00Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(rightSet.has('a')).toBe(true)
+    expect(leftSet.has('b')).toBe(true)
+    expect(leftSet.has('a')).toBe(false)
+    expect(rightSet.has('b')).toBe(false)
+  })
+})
diff --git a/apps/app/tests/unit/lib/timetable/capacity.test.ts b/apps/app/tests/unit/lib/timetable/capacity.test.ts
new file mode 100644
index 00000000..7d15c581
--- /dev/null
+++ b/apps/app/tests/unit/lib/timetable/capacity.test.ts
@@ -0,0 +1,76 @@
+import { describe, expect, it } from 'vitest'
+import { CAPACITY_TOLERANCE, evaluateCapacity } from '@/lib/timetable/capacity'
+import type { ArtistEngagement, Performance, Stage } from '@/types/timetable'
+
+const stage: Stage = {
+  id: 's1',
+  event_id: 'ev1',
+  name: 'Hardstyle',
+  color: '#ff0000',
+  capacity: 1000,
+  sort_order: 0,
+  created_at: null,
+  updated_at: null,
+}
+
+const perf: Performance = {
+  id: 'p1',
+  engagement_id: 'e1',
+  event_id: 'ev1',
+  stage_id: 's1',
+  lane: 0,
+  lane_resolved: 0,
+  start_at: null,
+  end_at: null,
+  version: 0,
+  notes: null,
+  warnings: [],
+  created_at: null,
+  updated_at: null,
+  deleted_at: null,
+}
+
+function eng(crew: number, guests: number, draw: number | null = null): ArtistEngagement {
+  return {
+    crew_count: crew,
+    guests_count: guests,
+    artist: draw === null ? undefined : { default_draw: draw } as ArtistEngagement['artist'],
+  } as ArtistEngagement
+}
+
+describe('evaluateCapacity', () => {
+  it('returns null when stage has no capacity', () => {
+    expect(evaluateCapacity(perf, { ...stage, capacity: null }, eng(0, 0, 500))).toBeNull()
+  })
+
+  it('returns null when no expected attendance is available', () => {
+    expect(evaluateCapacity(perf, stage, eng(0, 0))).toBeNull()
+  })
+
+  it('returns null when below the tolerance', () => {
+    expect(evaluateCapacity(perf, stage, eng(0, 0, 1100))).toBeNull()
+  })
+
+  it('returns warn when ratio between tolerance and 1.5×', () => {
+    const result = evaluateCapacity(perf, stage, eng(0, 0, 1200))
+
+    expect(result?.level).toBe('warn')
+  })
+
+  it('returns critical when ratio > 1.5', () => {
+    const result = evaluateCapacity(perf, stage, eng(0, 0, 1700))
+
+    expect(result?.level).toBe('critical')
+  })
+
+  it('prefers crew + guests when present', () => {
+    const result = evaluateCapacity(perf, stage, eng(800, 800))
+
+    expect(result?.expected).toBe(1600)
+    expect(result?.level).toBe('critical')
+  })
+
+  it('exposes the tolerance constant', () => {
+    expect(CAPACITY_TOLERANCE).toBeGreaterThan(1)
+  })
+})
diff --git a/apps/app/tests/unit/lib/timetable/conflict.test.ts b/apps/app/tests/unit/lib/timetable/conflict.test.ts
new file mode 100644
index 00000000..6e1ab456
--- /dev/null
+++ b/apps/app/tests/unit/lib/timetable/conflict.test.ts
@@ -0,0 +1,116 @@
+import { describe, expect, it } from 'vitest'
+import { findConflicts, wouldConflict } from '@/lib/timetable/conflict'
+import { ArtistEngagementStatus, type Performance } from '@/types/timetable'
+
+function p(overrides: Partial<Performance> = {}): Performance {
+  return {
+    id: 'p1',
+    engagement_id: 'e1',
+    event_id: 'ev1',
+    stage_id: 's1',
+    lane: 0,
+    lane_resolved: 0,
+    start_at: '2026-07-10T18:00:00.000Z',
+    end_at: '2026-07-10T19:00:00.000Z',
+    version: 0,
+    notes: null,
+    warnings: [],
+    created_at: null,
+    updated_at: null,
+    deleted_at: null,
+    ...overrides,
+  }
+}
+
+describe('findConflicts', () => {
+  it('flags two overlapping performances on the same lane', () => {
+    const conflicts = findConflicts([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T18:30:00Z', end_at: '2026-07-10T19:30:00Z' }),
+    ])
+
+    expect(conflicts).toEqual(new Set(['a', 'b']))
+  })
+
+  it('endpoint-touching is NOT overlap', () => {
+    const conflicts = findConflicts([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:00:00Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(conflicts.size).toBe(0)
+  })
+
+  it('different lanes on same stage = no conflict', () => {
+    const conflicts = findConflicts([
+      p({ id: 'a', lane_resolved: 0 }),
+      p({ id: 'b', lane_resolved: 1 }),
+    ])
+
+    expect(conflicts.size).toBe(0)
+  })
+
+  it('different stages = no conflict', () => {
+    const conflicts = findConflicts([
+      p({ id: 'a', stage_id: 's1' }),
+      p({ id: 'b', stage_id: 's2' }),
+    ])
+
+    expect(conflicts.size).toBe(0)
+  })
+
+  it('cancelled performances do not participate', () => {
+    const cancelled = p({
+      id: 'c',
+      engagement: {
+        booking_status: { value: ArtistEngagementStatus.CANCELLED, label: 'Geannuleerd' },
+      } as Performance['engagement'],
+    })
+
+    const conflicts = findConflicts([
+      p({ id: 'a' }),
+      cancelled,
+    ])
+
+    expect(conflicts.size).toBe(0)
+  })
+
+  it('parked performances (stage_id null) do not participate', () => {
+    const conflicts = findConflicts([
+      p({ id: 'a', stage_id: null }),
+      p({ id: 'b' }),
+    ])
+
+    expect(conflicts.size).toBe(0)
+  })
+})
+
+describe('wouldConflict', () => {
+  it('detects 1-pixel overlap', () => {
+    const others = [p({ id: 'x', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' })]
+
+    const result = wouldConflict({
+      id: 'new',
+      stage_id: 's1',
+      lane: 0,
+      start_at: '2026-07-10T18:59:00Z',
+      end_at: '2026-07-10T20:00:00Z',
+    }, others)
+
+    expect(result).toBe(true)
+  })
+
+  it('returns false when candidate is parked', () => {
+    const others = [p({ id: 'x' })]
+
+    const result = wouldConflict({
+      id: 'new',
+      stage_id: null,
+      lane: 0,
+      start_at: '2026-07-10T18:00:00Z',
+      end_at: '2026-07-10T19:00:00Z',
+    }, others)
+
+    expect(result).toBe(false)
+  })
+})
diff --git a/apps/app/tests/unit/lib/timetable/lane.test.ts b/apps/app/tests/unit/lib/timetable/lane.test.ts
new file mode 100644
index 00000000..2db93c43
--- /dev/null
+++ b/apps/app/tests/unit/lib/timetable/lane.test.ts
@@ -0,0 +1,111 @@
+import { describe, expect, it } from 'vitest'
+import { type LaneSubject, previewCascade, resolveLanes } from '@/lib/timetable/lane'
+import type { Performance } from '@/types/timetable'
+
+function s(id: string, start: string, end: string, lane: number | null = null, cancelled = false): LaneSubject {
+  return { id, start_at: start, end_at: end, lane, cancelled }
+}
+
+function p(id: string, start: string, end: string, lane = 0): Performance {
+  return {
+    id,
+    engagement_id: 'e1',
+    event_id: 'ev1',
+    stage_id: 's1',
+    lane,
+    lane_resolved: lane,
+    start_at: start,
+    end_at: end,
+    version: 0,
+    notes: null,
+    warnings: [],
+    created_at: null,
+    updated_at: null,
+    deleted_at: null,
+  }
+}
+
+describe('resolveLanes (Pass 2 only — implicit lanes)', () => {
+  it('places non-overlapping items on lane 0', () => {
+    const result = resolveLanes([
+      s('a', '2026-07-10T18:00:00Z', '2026-07-10T19:00:00Z'),
+      s('b', '2026-07-10T19:00:00Z', '2026-07-10T20:00:00Z'),
+    ])
+
+    expect(result.laneOf).toEqual({ a: 0, b: 0 })
+    expect(result.laneCount).toBe(1)
+  })
+
+  it('stacks overlapping items into separate lanes', () => {
+    const result = resolveLanes([
+      s('a', '2026-07-10T18:00:00Z', '2026-07-10T19:30:00Z'),
+      s('b', '2026-07-10T19:00:00Z', '2026-07-10T20:00:00Z'),
+    ])
+
+    expect(result.laneOf.a).toBe(0)
+    expect(result.laneOf.b).toBe(1)
+    expect(result.laneCount).toBe(2)
+  })
+
+  it('Pass 1 — explicit lane is honoured', () => {
+    const result = resolveLanes([
+      s('a', '2026-07-10T18:00:00Z', '2026-07-10T19:00:00Z', 2),
+      s('b', '2026-07-10T19:00:00Z', '2026-07-10T20:00:00Z'),
+    ])
+
+    expect(result.laneOf.a).toBe(2)
+    expect(result.laneOf.b).toBe(0)
+  })
+
+  it('Pass 1 — overlapping explicit lane bumps down', () => {
+    const result = resolveLanes([
+      s('a', '2026-07-10T18:00:00Z', '2026-07-10T19:30:00Z', 0),
+      s('b', '2026-07-10T19:00:00Z', '2026-07-10T20:00:00Z', 0),
+    ])
+
+    expect(result.laneOf.a).toBe(0)
+    expect(result.laneOf.b).toBe(1)
+  })
+
+  it('cancelled items are excluded from collision checks', () => {
+    const result = resolveLanes([
+      s('a', '2026-07-10T18:00:00Z', '2026-07-10T19:30:00Z'),
+      s('b', '2026-07-10T19:00:00Z', '2026-07-10T20:00:00Z', null, true),
+    ])
+
+    expect(result.laneOf.b).toBe(0)
+  })
+
+  it('handles empty input', () => {
+    const result = resolveLanes([])
+
+    expect(result.laneCount).toBe(1)
+    expect(result.laneOf).toEqual({})
+  })
+})
+
+describe('previewCascade (drag preview)', () => {
+  it('preserves wanted lane when target is free', () => {
+    const cohort = [p('a', '2026-07-10T18:00:00Z', '2026-07-10T19:00:00Z', 0)]
+
+    const result = previewCascade(
+      { id: 'dragged', lane: 1, start_at: '2026-07-10T18:30:00Z', end_at: '2026-07-10T19:30:00Z' },
+      cohort,
+    )
+
+    expect(result.laneOf.dragged).toBe(1)
+    expect(result.laneOf.a).toBe(0)
+  })
+
+  it('cascades existing item down when wanted lane is busy', () => {
+    const cohort = [p('a', '2026-07-10T18:00:00Z', '2026-07-10T19:00:00Z', 0)]
+
+    const result = previewCascade(
+      { id: 'dragged', lane: 0, start_at: '2026-07-10T18:30:00Z', end_at: '2026-07-10T19:30:00Z' },
+      cohort,
+    )
+
+    expect(result.laneOf.dragged).toBe(1)
+    expect(result.laneOf.a).toBe(0)
+  })
+})
diff --git a/apps/app/tests/unit/lib/timetable/snap.test.ts b/apps/app/tests/unit/lib/timetable/snap.test.ts
new file mode 100644
index 00000000..abb64fd3
--- /dev/null
+++ b/apps/app/tests/unit/lib/timetable/snap.test.ts
@@ -0,0 +1,41 @@
+import { describe, expect, it } from 'vitest'
+import { MIN_DURATION_MIN, SNAP_MIN, snap, snapClamp } from '@/lib/timetable/snap'
+
+describe('snap', () => {
+  it('rounds to nearest multiple of step', () => {
+    expect(snap(0, 5)).toBe(0)
+    expect(snap(2, 5)).toBe(0)
+    expect(snap(3, 5)).toBe(5)
+    expect(snap(7, 5)).toBe(5)
+    expect(snap(8, 5)).toBe(10)
+    expect(snap(12, 5)).toBe(10)
+    expect(snap(13, 5)).toBe(15)
+  })
+
+  it('returns value unchanged when step <= 0', () => {
+    expect(snap(7.3, 0)).toBe(7.3)
+    expect(snap(7.3, -1)).toBe(7.3)
+  })
+
+  it('handles exact-multiple inputs', () => {
+    expect(snap(15, 5)).toBe(15)
+    expect(snap(60, 15)).toBe(60)
+  })
+
+  it('exposes the SNAP_MIN constant', () => {
+    expect(SNAP_MIN).toBeGreaterThan(0)
+    expect(SNAP_MIN).toBeLessThanOrEqual(15)
+  })
+
+  it('exposes MIN_DURATION_MIN', () => {
+    expect(MIN_DURATION_MIN).toBe(15)
+  })
+})
+
+describe('snapClamp', () => {
+  it('snaps then clamps inside [min, max]', () => {
+    expect(snapClamp(7, 5, 0, 100)).toBe(5)
+    expect(snapClamp(-5, 5, 0, 100)).toBe(0)
+    expect(snapClamp(150, 5, 0, 100)).toBe(100)
+  })
+})
diff --git a/apps/app/tests/unit/lib/timetable/time-grid.test.ts b/apps/app/tests/unit/lib/timetable/time-grid.test.ts
new file mode 100644
index 00000000..496207ea
--- /dev/null
+++ b/apps/app/tests/unit/lib/timetable/time-grid.test.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from 'vitest'
+import {
+  formatTickLabel,
+  generateTicks,
+  isoToMinutes,
+  minutesToIso,
+  minutesToPx,
+  pxToMinutes,
+} from '@/lib/timetable/time-grid'
+
+describe('time-grid coordinate conversions', () => {
+  const gridStart = '2026-07-10T14:00:00.000Z'
+
+  it('isoToMinutes returns 0 at the anchor', () => {
+    expect(isoToMinutes(gridStart, gridStart)).toBe(0)
+  })
+
+  it('isoToMinutes computes minute offsets', () => {
+    expect(isoToMinutes('2026-07-10T15:00:00.000Z', gridStart)).toBe(60)
+    expect(isoToMinutes('2026-07-10T14:30:00.000Z', gridStart)).toBe(30)
+    expect(isoToMinutes('2026-07-10T13:30:00.000Z', gridStart)).toBe(-30)
+  })
+
+  it('roundtrip isoToMinutes ↔ minutesToIso preserves the value', () => {
+    const back = minutesToIso(isoToMinutes('2026-07-10T18:45:00.000Z', gridStart), gridStart)
+
+    expect(back).toBe('2026-07-10T18:45:00.000Z')
+  })
+
+  it('minutesToPx and pxToMinutes are inverses', () => {
+    expect(minutesToPx(30, 2)).toBe(60)
+    expect(pxToMinutes(60, 2)).toBe(30)
+    expect(pxToMinutes(60, 0)).toBe(0)
+  })
+
+  it('formatTickLabel returns nl-NL HH:MM', () => {
+    const label = formatTickLabel(0, gridStart)
+
+    expect(label).toMatch(/^\d{2}:\d{2}$/)
+  })
+
+  it('generateTicks produces inclusive endpoints', () => {
+    const ticks = generateTicks(120, 30)
+
+    expect(ticks).toEqual([0, 30, 60, 90, 120])
+  })
+})
diff --git a/apps/app/tests/unit/schemas/timetable.test.ts b/apps/app/tests/unit/schemas/timetable.test.ts
new file mode 100644
index 00000000..6203d449
--- /dev/null
+++ b/apps/app/tests/unit/schemas/timetable.test.ts
@@ -0,0 +1,118 @@
+import { describe, expect, it } from 'vitest'
+import {
+  createPerformancePayloadSchema,
+  createStagePayloadSchema,
+  performanceSchema,
+} from '@/schemas/timetable'
+
+describe('createPerformancePayloadSchema', () => {
+  it('accepts a complete payload', () => {
+    const result = createPerformancePayloadSchema.safeParse({
+      engagement_id: 'e1',
+      event_id: 'ev1',
+      stage_id: 's1',
+      start_at: '2026-07-10 18:00:00',
+      end_at: '2026-07-10 19:00:00',
+      lane: 0,
+      notes: null,
+    })
+
+    expect(result.success).toBe(true)
+  })
+
+  it('rejects missing engagement_id', () => {
+    const result = createPerformancePayloadSchema.safeParse({
+      engagement_id: '',
+      event_id: 'ev1',
+      stage_id: null,
+      start_at: '2026-07-10 18:00:00',
+      end_at: '2026-07-10 19:00:00',
+    })
+
+    expect(result.success).toBe(false)
+  })
+
+  it('rejects end <= start', () => {
+    const result = createPerformancePayloadSchema.safeParse({
+      engagement_id: 'e1',
+      event_id: 'ev1',
+      stage_id: null,
+      start_at: '2026-07-10 19:00:00',
+      end_at: '2026-07-10 18:00:00',
+    })
+
+    expect(result.success).toBe(false)
+  })
+
+  it('rejects lane > 9', () => {
+    const result = createPerformancePayloadSchema.safeParse({
+      engagement_id: 'e1',
+      event_id: 'ev1',
+      stage_id: null,
+      start_at: '2026-07-10 18:00:00',
+      end_at: '2026-07-10 19:00:00',
+      lane: 99,
+    })
+
+    expect(result.success).toBe(false)
+  })
+})
+
+describe('createStagePayloadSchema', () => {
+  it('accepts uppercase + lowercase hex', () => {
+    expect(createStagePayloadSchema.safeParse({ name: 'A', color: '#aabbcc' }).success).toBe(true)
+    expect(createStagePayloadSchema.safeParse({ name: 'A', color: '#AABBCC' }).success).toBe(true)
+  })
+
+  it('rejects shorthand hex', () => {
+    expect(createStagePayloadSchema.safeParse({ name: 'A', color: '#abc' }).success).toBe(false)
+  })
+
+  it('rejects empty name', () => {
+    expect(createStagePayloadSchema.safeParse({ name: '', color: '#aabbcc' }).success).toBe(false)
+  })
+})
+
+describe('performanceSchema', () => {
+  it('parses a minimal performance', () => {
+    const result = performanceSchema.safeParse({
+      id: 'p1',
+      engagement_id: 'e1',
+      event_id: 'ev1',
+      stage_id: null,
+      lane: 0,
+      lane_resolved: 0,
+      start_at: null,
+      end_at: null,
+      version: 0,
+      notes: null,
+      warnings: [],
+      created_at: null,
+      updated_at: null,
+      deleted_at: null,
+    })
+
+    expect(result.success).toBe(true)
+  })
+
+  it('rejects unknown warning value', () => {
+    const result = performanceSchema.safeParse({
+      id: 'p1',
+      engagement_id: 'e1',
+      event_id: 'ev1',
+      stage_id: null,
+      lane: 0,
+      lane_resolved: 0,
+      start_at: null,
+      end_at: null,
+      version: 0,
+      notes: null,
+      warnings: ['nonsense'],
+      created_at: null,
+      updated_at: null,
+      deleted_at: null,
+    })
+
+    expect(result.success).toBe(false)
+  })
+})
diff --git a/apps/app/tests/unit/stores/useTimetableStore.test.ts b/apps/app/tests/unit/stores/useTimetableStore.test.ts
new file mode 100644
index 00000000..06f22ced
--- /dev/null
+++ b/apps/app/tests/unit/stores/useTimetableStore.test.ts
@@ -0,0 +1,77 @@
+import { createPinia, setActivePinia } from 'pinia'
+import { beforeEach, describe, expect, it } from 'vitest'
+import { useTimetableStore } from '@/stores/useTimetableStore'
+import { ArtistEngagementStatus, type Performance } from '@/types/timetable'
+
+function p(): Performance {
+  return {
+    id: 'p1',
+    engagement_id: 'e1',
+    event_id: 'ev1',
+    stage_id: 's1',
+    lane: 0,
+    lane_resolved: 0,
+    start_at: '2026-07-10T18:00:00.000Z',
+    end_at: '2026-07-10T19:00:00.000Z',
+    version: 1,
+    notes: null,
+    warnings: [],
+    created_at: null,
+    updated_at: null,
+    deleted_at: null,
+  }
+}
+
+describe('useTimetableStore', () => {
+  beforeEach(() => setActivePinia(createPinia()))
+
+  it('initialises with cancelled OFF in status filter', () => {
+    const store = useTimetableStore()
+
+    expect(store.isStatusVisible(ArtistEngagementStatus.CONFIRMED)).toBe(true)
+    expect(store.isStatusVisible(ArtistEngagementStatus.CANCELLED)).toBe(false)
+  })
+
+  it('toggleStatus flips a single status', () => {
+    const store = useTimetableStore()
+
+    store.toggleStatus(ArtistEngagementStatus.CONFIRMED)
+    expect(store.isStatusVisible(ArtistEngagementStatus.CONFIRMED)).toBe(false)
+    store.toggleStatus(ArtistEngagementStatus.CONFIRMED)
+    expect(store.isStatusVisible(ArtistEngagementStatus.CONFIRMED)).toBe(true)
+  })
+
+  it('setActiveDay updates and selectPerformance maps to id', () => {
+    const store = useTimetableStore()
+
+    store.setActiveDay('day_1')
+    expect(store.activeDayId).toBe('day_1')
+    store.selectPerformance('p1')
+    expect(store.selectedPerformanceId).toBe('p1')
+    store.selectPerformance(null)
+    expect(store.selectedPerformanceId).toBeNull()
+  })
+
+  it('startDrag/endDrag manages snapshot + ghost', () => {
+    const store = useTimetableStore()
+
+    expect(store.isDragging).toBe(false)
+    store.startDrag(p())
+    expect(store.isDragging).toBe(true)
+    expect(store.dragOriginSnapshot?.id).toBe('p1')
+
+    store.updateDragGhost({ stageId: 's1', startAt: '2026-07-10T18:30:00Z', endAt: '2026-07-10T19:30:00Z', lane: 1 })
+    expect(store.dragGhost?.lane).toBe(1)
+
+    store.endDrag()
+    expect(store.isDragging).toBe(false)
+    expect(store.dragGhost).toBeNull()
+  })
+
+  it('isStatusVisible handles null gracefully', () => {
+    const store = useTimetableStore()
+
+    expect(store.isStatusVisible(null)).toBe(false)
+    expect(store.isStatusVisible(undefined)).toBe(false)
+  })
+})