diff --git a/CHANGELOG.md b/CHANGELOG.md
index ebad69b4..e1cd9113 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -105,6 +105,13 @@ ADR-007 and ADR-002.
   the wrong code. The page index now travels with the page.
 - The back label's dotted preview outline outspecified the print reset and drew
   a dashed rule down the edge of every second card.
+- **The warranty list could not be searched by machine number.** The number was
+  in the payload and rendered in the table as a chip, but the search box looked
+  only at vendor, service level, service tag and asset number. That made the
+  identifier the feature was built around - a shopfloor PC is warranted as a PC
+  but found by the machine it drives - the one thing the box could not find.
+  Machine number and machine name are now searched too, and the placeholder
+  names them.
 - **`flask plugin upgrade-all` failed a plugin whose tables already existed**
   ("table securesendsecrets already exists" on the tools plugin). Every
   post-cutover baseline emitted a plain `op.create_table`, which is correct only
diff --git a/plugins/warranty/frontend/views/WarrantiesList.vue b/plugins/warranty/frontend/views/WarrantiesList.vue
index e208cc04..1913dd92 100644
--- a/plugins/warranty/frontend/views/WarrantiesList.vue
+++ b/plugins/warranty/frontend/views/WarrantiesList.vue
@@ -24,7 +24,7 @@
           <option value="unknown">Unknown</option>
         </select>
       </label>
-      <input v-model="search" type="text" class="form-control" placeholder="Search vendor, service level, tag, asset..." />
+      <input v-model="search" type="text" class="form-control" placeholder="Search vendor, service level, tag, asset number, machine..." />
       <span class="result-count">{{ filteredItems.length }} of {{ items.length }}</span>
     </div>
 
@@ -186,6 +186,7 @@ import api, { warrantyApi, assetsApi, vendorsApi } from '@/api'
 import { useToast } from '@/composables/toast'
 import { apiError } from '@/utils/apiError'
 import MachineMapChip from '../components/MachineMapChip.vue'
+import { matchesWarrantySearch } from './warrantySearch'
 
 const toast = useToast()
 const route = useRoute()
@@ -197,16 +198,11 @@ const search = ref('')
 const page = ref(1)
 const perPage = 25
 
-// Client-side search across vendor / service level / tag / linked asset numbers.
-const filteredItems = computed(() => {
-  const term = search.value.trim().toLowerCase()
-  if (!term) return items.value
-  return items.value.filter(w =>
-    (w.vendor || '').toLowerCase().includes(term) ||
-    (w.servicelevel || '').toLowerCase().includes(term) ||
-    (w.servicetag || '').toLowerCase().includes(term) ||
-    (w.assets || []).some(a => (a.assetnumber || '').toLowerCase().includes(term)))
-})
+// Client-side search. The field list lives in warrantySearch.js, where it is
+// covered by tests - the machine number was rendered in this table for a long
+// time before anything let you search for it.
+const filteredItems = computed(() =>
+  items.value.filter(w => matchesWarrantySearch(w, search.value)))
 const totalPages = computed(() => Math.max(1, Math.ceil(filteredItems.value.length / perPage)))
 const paginatedItems = computed(() => filteredItems.value.slice((page.value - 1) * perPage, page.value * perPage))
 
diff --git a/plugins/warranty/frontend/views/warrantySearch.js b/plugins/warranty/frontend/views/warrantySearch.js
new file mode 100644
index 00000000..8579e299
--- /dev/null
+++ b/plugins/warranty/frontend/views/warrantySearch.js
@@ -0,0 +1,44 @@
+// What the warranty list's search box matches against.
+//
+// Pulled out of WarrantiesList.vue so the field list is somewhere a test can
+// see it. It went wrong the way a field list usually does: silently, by a
+// column being added to the table and not to the filter.
+//
+// THE MACHINE NUMBER IS THE POINT. _related_machine in the warranty API exists
+// precisely because "a shopfloor PC is bought, warranted and replaced as a PC,
+// but it is FOUND by the machine it drives - nobody walks the floor looking for
+// an asset number". The payload carries it, the table renders it in a chip, and
+// the filter did not look at it - so the one identifier the feature was built
+// around was the one thing the search box could not find.
+
+/**
+ * Does this warranty match the search term?
+ *
+ * @param {object} warranty - a row from GET /api/warranties
+ * @param {string} term - the raw search box contents
+ * @returns {boolean} true when the term is empty or any searched field contains it
+ */
+export function matchesWarrantySearch(warranty, term) {
+  const needle = (term || '').trim().toLowerCase()
+  if (!needle) return true
+  if (!warranty) return false
+
+  const has = (value) => String(value ?? '').toLowerCase().includes(needle)
+
+  if (has(warranty.vendor) || has(warranty.servicelevel) || has(warranty.servicetag)) {
+    return true
+  }
+
+  return (warranty.assets || []).some((asset) => {
+    if (has(asset?.assetnumber)) return true
+    // The related machine is optional: a warranty on something that drives no
+    // machine has none, and a machine that was never linked leaves it null.
+    const machine = asset?.machine
+    return !!machine && (has(machine.machinenumber) || has(machine.name))
+  })
+}
+
+/** The fields above, in the order the placeholder should name them. */
+export const WARRANTY_SEARCH_FIELDS = [
+  'vendor', 'service level', 'tag', 'asset number', 'machine',
+]
diff --git a/plugins/warranty/frontend/views/warrantySearch.spec.js b/plugins/warranty/frontend/views/warrantySearch.spec.js
new file mode 100644
index 00000000..fc2e17cd
--- /dev/null
+++ b/plugins/warranty/frontend/views/warrantySearch.spec.js
@@ -0,0 +1,79 @@
+import { describe, it, expect } from 'vitest'
+
+import { matchesWarrantySearch } from './warrantySearch'
+
+// Reported: the warranty page could not be searched by machine number.
+//
+// The number was in the payload (_related_machine puts it there) and rendered
+// in the table as a chip, but the filter looked only at vendor, service level,
+// service tag and asset number. So the identifier the feature was built around
+// - a PC is warranted as a PC but FOUND by the machine it drives - was the one
+// thing the box could not find.
+
+function warranty(overrides = {}) {
+  return {
+    vendor: 'Dell',
+    servicelevel: 'ProSupport',
+    servicetag: 'ABC1234',
+    assets: [{
+      assetnumber: 'PC-00912',
+      name: 'Bay 3105 workstation',
+      machine: { machinenumber: '3016', name: 'Makino a61nx' },
+    }],
+    ...overrides,
+  }
+}
+
+describe('matchesWarrantySearch', () => {
+  it('matches on the machine number', () => {
+    // The reported case.
+    expect(matchesWarrantySearch(warranty(), '3016')).toBe(true)
+  })
+
+  it('matches on the machine name', () => {
+    expect(matchesWarrantySearch(warranty(), 'makino')).toBe(true)
+  })
+
+  it('still matches the fields it always did', () => {
+    expect(matchesWarrantySearch(warranty(), 'dell')).toBe(true)
+    expect(matchesWarrantySearch(warranty(), 'prosupport')).toBe(true)
+    expect(matchesWarrantySearch(warranty(), 'abc1234')).toBe(true)
+    expect(matchesWarrantySearch(warranty(), 'pc-00912')).toBe(true)
+  })
+
+  it('is case insensitive and ignores surrounding space', () => {
+    expect(matchesWarrantySearch(warranty(), '  MAKINO  ')).toBe(true)
+  })
+
+  it('does not match an unrelated term', () => {
+    expect(matchesWarrantySearch(warranty(), '9999')).toBe(false)
+  })
+
+  it('keeps every row when the term is empty', () => {
+    expect(matchesWarrantySearch(warranty(), '')).toBe(true)
+    expect(matchesWarrantySearch(warranty(), '   ')).toBe(true)
+    expect(matchesWarrantySearch(warranty(), undefined)).toBe(true)
+  })
+
+  it('handles a warranty whose asset drives no machine', () => {
+    // machine is null whenever the covered asset has no controls link - a
+    // printer, or a PC nobody linked yet. It must not throw.
+    const row = warranty({ assets: [{ assetnumber: 'PR-42', machine: null }] })
+    expect(matchesWarrantySearch(row, 'PR-42')).toBe(true)
+    expect(matchesWarrantySearch(row, '3016')).toBe(false)
+  })
+
+  it('handles a warranty with no linked assets at all', () => {
+    const row = warranty({ assets: [] })
+    expect(matchesWarrantySearch(row, 'dell')).toBe(true)
+    expect(matchesWarrantySearch(row, '3016')).toBe(false)
+  })
+
+  it('tolerates missing fields rather than matching everything', () => {
+    // String(undefined) is 'undefined', which would make a search for 'und'
+    // match every row with an empty field.
+    const row = { vendor: null, servicelevel: undefined, assets: null }
+    expect(matchesWarrantySearch(row, 'und')).toBe(false)
+    expect(matchesWarrantySearch(row, 'null')).toBe(false)
+  })
+})