diff --git a/__tests__/equipment-logic.test.ts b/__tests__/equipment-logic.test.ts
new file mode 100644
index 0000000..e209ec2
--- /dev/null
+++ b/__tests__/equipment-logic.test.ts
@@ -0,0 +1,63 @@
+import { describe, it, expect } from 'vitest'
+import {
+  intervalsOverlap,
+  hasConflict,
+  reservationEligibility,
+} from '@/lib/equipment-logic'
+
+describe('intervalsOverlap', () => {
+  it('detects overlap and treats touching as non-overlap', () => {
+    expect(intervalsOverlap('2026-01-01T10:00Z', '2026-01-01T12:00Z', '2026-01-01T11:00Z', '2026-01-01T13:00Z')).toBe(true)
+    expect(intervalsOverlap('2026-01-01T10:00Z', '2026-01-01T12:00Z', '2026-01-01T12:00Z', '2026-01-01T13:00Z')).toBe(false)
+    expect(intervalsOverlap('2026-01-01T10:00Z', '2026-01-01T12:00Z', '2026-01-01T08:00Z', '2026-01-01T09:00Z')).toBe(false)
+  })
+  it('is false on unparseable input', () => {
+    expect(intervalsOverlap('x', 'y', 'a', 'b')).toBe(false)
+  })
+})
+
+describe('hasConflict', () => {
+  const req = ['2026-02-01T10:00Z', '2026-02-01T12:00Z'] as const
+  it('only reserved rows block', () => {
+    expect(hasConflict(req[0], req[1], [{ starts_at: '2026-02-01T11:00Z', ends_at: '2026-02-01T13:00Z', status: 'reserved' }])).toBe(true)
+    expect(hasConflict(req[0], req[1], [{ starts_at: '2026-02-01T11:00Z', ends_at: '2026-02-01T13:00Z', status: 'cancelled' }])).toBe(false)
+    expect(hasConflict(req[0], req[1], [{ starts_at: '2026-02-01T11:00Z', ends_at: '2026-02-01T13:00Z', status: 'completed' }])).toBe(false)
+  })
+  it('no conflict when disjoint', () => {
+    expect(hasConflict(req[0], req[1], [{ starts_at: '2026-02-01T12:00Z', ends_at: '2026-02-01T14:00Z', status: 'reserved' }])).toBe(false)
+  })
+})
+
+describe('reservationEligibility', () => {
+  const base = {
+    equipmentStatus: 'available',
+    equipmentActive: true,
+    startsAt: '2026-06-01T10:00:00Z',
+    endsAt: '2026-06-01T12:00:00Z',
+    now: '2026-05-16T00:00:00Z',
+    conflict: false,
+    requiresCert: false,
+    memberHasCert: false,
+    managerOverride: false,
+  }
+  it('allows a clean future reservation', () => {
+    expect(reservationEligibility(base).ok).toBe(true)
+  })
+  it('blocks archived/retired/maintenance', () => {
+    expect(reservationEligibility({ ...base, equipmentActive: false }).ok).toBe(false)
+    expect(reservationEligibility({ ...base, equipmentStatus: 'retired' }).ok).toBe(false)
+    expect(reservationEligibility({ ...base, equipmentStatus: 'maintenance' }).ok).toBe(false)
+  })
+  it('blocks past start and end<=start', () => {
+    expect(reservationEligibility({ ...base, startsAt: '2026-05-01T10:00:00Z' }).ok).toBe(false)
+    expect(reservationEligibility({ ...base, endsAt: '2026-06-01T10:00:00Z' }).ok).toBe(false)
+  })
+  it('blocks on conflict', () => {
+    expect(reservationEligibility({ ...base, conflict: true }).ok).toBe(false)
+  })
+  it('enforces the cert gate with manager override', () => {
+    expect(reservationEligibility({ ...base, requiresCert: true, memberHasCert: false }).ok).toBe(false)
+    expect(reservationEligibility({ ...base, requiresCert: true, memberHasCert: true }).ok).toBe(true)
+    expect(reservationEligibility({ ...base, requiresCert: true, memberHasCert: false, managerOverride: true }).ok).toBe(true)
+  })
+})
diff --git a/lib/equipment-logic.ts b/lib/equipment-logic.ts
new file mode 100644
index 0000000..9f37c16
--- /dev/null
+++ b/lib/equipment-logic.ts
@@ -0,0 +1,91 @@
+// Pure, dependency-free decision logic for the equipment feature. No
+// Supabase, no React, no Next. Unit-tested directly so the overlap and
+// reservation-eligibility rules cannot silently drift.
+
+function ms(value: string): number | null {
+  const t = new Date(value).getTime()
+  return Number.isNaN(t) ? null : t
+}
+
+// Half-open [start, end): two windows overlap iff each starts before the
+// other ends. Touching end-to-start (a.end === b.start) does NOT overlap.
+export function intervalsOverlap(
+  aStart: string,
+  aEnd: string,
+  bStart: string,
+  bEnd: string,
+): boolean {
+  const as = ms(aStart)
+  const ae = ms(aEnd)
+  const bs = ms(bStart)
+  const be = ms(bEnd)
+  if (as == null || ae == null || bs == null || be == null) return false
+  return as < be && bs < ae
+}
+
+// Does a requested window conflict with any blocking reservation? Only
+// 'reserved' rows block; 'cancelled' and 'completed' never do.
+export function hasConflict(
+  reqStart: string,
+  reqEnd: string,
+  existing: Array<{ starts_at: string; ends_at: string; status: string }>,
+): boolean {
+  return existing.some(
+    r =>
+      r.status === 'reserved' &&
+      intervalsOverlap(reqStart, reqEnd, r.starts_at, r.ends_at),
+  )
+}
+
+export type ReservationEligibility = { ok: true } | { ok: false; reason: string }
+
+// Whether a reservation may be created. managerOverride bypasses only the
+// required-certification gate (and is also how a manager books on someone
+// else's behalf); it does NOT override an operational status block.
+export function reservationEligibility(input: {
+  equipmentStatus: string
+  equipmentActive: boolean
+  startsAt: string
+  endsAt: string
+  now?: Date | string
+  conflict: boolean
+  requiresCert: boolean
+  memberHasCert: boolean
+  managerOverride: boolean
+}): ReservationEligibility {
+  if (!input.equipmentActive) return { ok: false, reason: 'This equipment is archived.' }
+  if (input.equipmentStatus === 'retired') return { ok: false, reason: 'This equipment is retired.' }
+  if (input.equipmentStatus === 'maintenance') {
+    return { ok: false, reason: 'This equipment is under maintenance and cannot be reserved.' }
+  }
+  if (input.equipmentStatus !== 'available') {
+    return { ok: false, reason: 'This equipment is not available.' }
+  }
+
+  const start = ms(input.startsAt)
+  const end = ms(input.endsAt)
+  if (start == null || end == null) return { ok: false, reason: 'Invalid reservation time.' }
+  if (end <= start) return { ok: false, reason: 'The end time must be after the start time.' }
+  const t = input.now == null ? Date.now() : new Date(input.now).getTime()
+  if (start < t) return { ok: false, reason: 'The reservation cannot start in the past.' }
+
+  if (input.conflict) {
+    return { ok: false, reason: 'That time overlaps an existing reservation for this equipment.' }
+  }
+  if (input.requiresCert && !input.memberHasCert && !input.managerOverride) {
+    return { ok: false, reason: 'You are not certified to reserve this equipment.' }
+  }
+  return { ok: true }
+}
+
+export const EQUIPMENT_STATUS_LABEL: Record<string, string> = {
+  available: 'Available',
+  maintenance: 'Under maintenance',
+  retired: 'Retired',
+}
+
+export const RESERVATION_STATUS_LABEL: Record<string, string> = {
+  reserved: 'Reserved',
+  cancelled: 'Cancelled',
+  completed: 'Completed',
+}
diff --git a/lib/validations.ts b/lib/validations.ts
index 9b57461..34853cf 100644
--- a/lib/validations.ts
+++ b/lib/validations.ts
@@ -829,6 +829,51 @@ export const listSessionSignupsSchema = z.object({
   sessionId: z.string().uuid('Invalid session ID'),
 })
 
+// ─── Equipment ───────────────────────────────────────────────────────────────
+
+const equipmentStatus = z.enum(['available', 'maintenance', 'retired'])
+
+export const createEquipmentSchema = z.object({
+  name: z.string().min(1, 'Name is required').max(200),
+  description: z.string().max(5000).optional().nullable(),
+  location: z.string().max(300).optional().nullable(),
+  status: equipmentStatus.optional().default('available'),
+  required_certification_id: z.string().uuid('Invalid certification ID').optional().nullable(),
+  asset_tag: z.string().max(120).optional().nullable(),
+})
+
+export const updateEquipmentSchema = z.object({
+  equipmentId: z.string().uuid('Invalid equipment ID'),
+  name: z.string().min(1).max(200).optional(),
+  description: z.string().max(5000).optional().nullable(),
+  location: z.string().max(300).optional().nullable(),
+  status: equipmentStatus.optional(),
+  required_certification_id: z.string().uuid('Invalid certification ID').optional().nullable(),
+  asset_tag: z.string().max(120).optional().nullable(),
+  is_active: z.boolean().optional(),
+})
+
+export const equipmentIdSchema = z.object({
+  equipmentId: z.string().uuid('Invalid equipment ID'),
+})
+
+export const reserveEquipmentSchema = z.object({
+  equipmentId: z.string().uuid('Invalid equipment ID'),
+  starts_at: z.string().min(1, 'A start time is required').max(40),
+  ends_at: z.string().min(1, 'An end time is required').max(40),
+  notes: z.string().max(2000).optional().nullable(),
+  // Manager-only: book on another member's behalf. Ignored for non-managers.
+  memberId: z.string().uuid('Invalid member ID').optional().nullable(),
+})
+
+export const cancelReservationSchema = z.object({
+  reservationId: z.string().uuid('Invalid reservation ID'),
+})
+
+export const listEquipmentReservationsSchema = z.object({
+  equipmentId: z.string().uuid('Invalid equipment ID'),
+})
+
 // ─── Generic ID schemas ──────────────────────────────────────────────────────
 
 export const uuidSchema = z.string().uuid('Invalid ID format')