diff --git a/OMICRON_VERSION b/OMICRON_VERSION
index bf2cdf03d..5d15d27be 100644
--- a/OMICRON_VERSION
+++ b/OMICRON_VERSION
@@ -1 +1 @@
-d7c3b00d743bcc9212b222a74ae27cc970b1ee2c
+254a0c51bc0beecb79c8a9dfccce8e7bc35b5ca4
diff --git a/app/api/__generated__/Api.ts b/app/api/__generated__/Api.ts
index b19107dde..5edbefb34 100644
--- a/app/api/__generated__/Api.ts
+++ b/app/api/__generated__/Api.ts
@@ -4626,13 +4626,15 @@ export type SubnetPoolSiloUpdate = {
 export type SubnetPoolUpdate = { description?: string | null; name?: Name | null }
 
 /**
- * Utilization information for a subnet pool
+ * Utilization of addresses in a subnet pool.
+ *
+ * Note that both the count of remaining addresses and the total capacity are integers, reported as floating point numbers. This accommodates allocations larger than a 64-bit integer, which is common with IPv6 address spaces. With very large subnet pools (> 2**53 addresses), integer precision will be lost, in exchange for representing the entire range. In such a case the pool still has many available addresses.
  */
 export type SubnetPoolUtilization = {
-  /** Number of addresses allocated from this pool */
-  allocated: number
-  /** Total capacity of this pool in addresses */
+  /** The total number of addresses in the pool. */
   capacity: number
+  /** The number of remaining addresses in the pool. */
+  remaining: number
 }
 
 export type SupportBundleCreate = {
@@ -7480,7 +7482,7 @@ export class Api {
    * Pulled from info.version in the OpenAPI schema. Sent in the
    * `api-version` header on all requests.
    */
-  apiVersion = '2026032400.0.0'
+  apiVersion = '2026032500.0.0'
 
   constructor({ host = '', baseParams = {}, token }: ApiConfig = {}) {
     this.host = host
diff --git a/app/api/__generated__/OMICRON_VERSION b/app/api/__generated__/OMICRON_VERSION
index 2b381dbd8..b8bd5a888 100644
--- a/app/api/__generated__/OMICRON_VERSION
+++ b/app/api/__generated__/OMICRON_VERSION
@@ -1,2 +1,2 @@
 # generated file. do not update manually. see docs/update-pinned-api.md
-d7c3b00d743bcc9212b222a74ae27cc970b1ee2c
+254a0c51bc0beecb79c8a9dfccce8e7bc35b5ca4
diff --git a/app/api/__generated__/validate.ts b/app/api/__generated__/validate.ts
index a36aad625..0c46dc8e5 100644
--- a/app/api/__generated__/validate.ts
+++ b/app/api/__generated__/validate.ts
@@ -4218,11 +4218,13 @@ export const SubnetPoolUpdate = z.preprocess(
 )
 
 /**
- * Utilization information for a subnet pool
+ * Utilization of addresses in a subnet pool.
+ *
+ * Note that both the count of remaining addresses and the total capacity are integers, reported as floating point numbers. This accommodates allocations larger than a 64-bit integer, which is common with IPv6 address spaces. With very large subnet pools (> 2**53 addresses), integer precision will be lost, in exchange for representing the entire range. In such a case the pool still has many available addresses.
  */
 export const SubnetPoolUtilization = z.preprocess(
   processResponseBody,
-  z.object({ allocated: z.number(), capacity: z.number() })
+  z.object({ capacity: z.number(), remaining: z.number() })
 )
 
 export const SupportBundleCreate = z.preprocess(
diff --git a/app/forms/subnet-pool-member-add.tsx b/app/forms/subnet-pool-member-add.tsx
index 7d15d5a4c..9327c9091 100644
--- a/app/forms/subnet-pool-member-add.tsx
+++ b/app/forms/subnet-pool-member-add.tsx
@@ -117,6 +117,7 @@ export default function SubnetPoolMemberAdd() {
   const addMember = useApiMutation(api.systemSubnetPoolMemberAdd, {
     onSuccess() {
       queryClient.invalidateEndpoint('systemSubnetPoolMemberList')
+      queryClient.invalidateEndpoint('systemSubnetPoolUtilizationView')
       addToast({ content: 'Member added' })
       onDismiss()
     },
diff --git a/app/pages/system/networking/IpPoolPage.tsx b/app/pages/system/networking/IpPoolPage.tsx
index 7c9bf6bb4..4177afbac 100644
--- a/app/pages/system/networking/IpPoolPage.tsx
+++ b/app/pages/system/networking/IpPoolPage.tsx
@@ -42,7 +42,7 @@ import { LinkCell } from '~/table/cells/LinkCell'
 import { useColsWithActions, type MenuAction } from '~/table/columns/action-col'
 import { Columns } from '~/table/columns/common'
 import { useQueryTable } from '~/table/QueryTable'
-import { BigNum } from '~/ui/lib/BigNum'
+import { UtilizationFraction } from '~/ui/lib/BigNum'
 import { toComboboxItems } from '~/ui/lib/Combobox'
 import { CreateButton, CreateLink } from '~/ui/lib/CreateButton'
 import * as Dropdown from '~/ui/lib/DropdownMenu'
@@ -209,9 +209,7 @@ function PoolProperties() {
       </PropertiesTable.Row>
       <PropertiesTable.Row label="IPs remaining">
         <span>
-          <BigNum className="text-raise" num={utilization.remaining} />
-          {' / '}
-          <BigNum className="text-secondary" num={utilization.capacity} />
+          <UtilizationFraction {...utilization} />
         </span>
       </PropertiesTable.Row>
       <PropertiesTable.DateRow date={pool.timeCreated} label="Created" />
diff --git a/app/pages/system/networking/IpPoolsPage.tsx b/app/pages/system/networking/IpPoolsPage.tsx
index 70c3be516..914a841ca 100644
--- a/app/pages/system/networking/IpPoolsPage.tsx
+++ b/app/pages/system/networking/IpPoolsPage.tsx
@@ -26,7 +26,7 @@ import { makeLinkCell } from '~/table/cells/LinkCell'
 import { useColsWithActions, type MenuAction } from '~/table/columns/action-col'
 import { Columns } from '~/table/columns/common'
 import { useQueryTable } from '~/table/QueryTable'
-import { BigNum } from '~/ui/lib/BigNum'
+import { UtilizationFraction } from '~/ui/lib/BigNum'
 import { CreateLink } from '~/ui/lib/CreateButton'
 import { EmptyMessage } from '~/ui/lib/EmptyMessage'
 import { PageHeader, PageTitle } from '~/ui/lib/PageHeader'
@@ -50,8 +50,7 @@ function UtilizationCell({ pool }: { pool: string }) {
   if (!data) return <SkeletonCell />
   return (
     <div>
-      <BigNum className="text-raise" num={data.remaining} /> /{' '}
-      <BigNum className="text-secondary" num={data.capacity} />
+      <UtilizationFraction {...data} />
     </div>
   )
 }
diff --git a/app/pages/system/networking/SubnetPoolPage.tsx b/app/pages/system/networking/SubnetPoolPage.tsx
index cc15b4fea..3403b133e 100644
--- a/app/pages/system/networking/SubnetPoolPage.tsx
+++ b/app/pages/system/networking/SubnetPoolPage.tsx
@@ -42,6 +42,7 @@ import { LinkCell } from '~/table/cells/LinkCell'
 import { useColsWithActions, type MenuAction } from '~/table/columns/action-col'
 import { Columns } from '~/table/columns/common'
 import { useQueryTable } from '~/table/QueryTable'
+import { UtilizationFraction } from '~/ui/lib/BigNum'
 import { toComboboxItems } from '~/ui/lib/Combobox'
 import { CreateButton, CreateLink } from '~/ui/lib/CreateButton'
 import * as Dropdown from '~/ui/lib/DropdownMenu'
@@ -65,6 +66,8 @@ const subnetPoolMemberList = ({ subnetPool }: PP.SubnetPool) =>
   getListQFn(api.systemSubnetPoolMemberList, { path: { pool: subnetPool } })
 const siloList = q(api.siloList, { query: { limit: ALL_ISH } })
 const siloView = ({ silo }: PP.Silo) => q(api.siloView, { path: { silo } })
+const subnetPoolUtilizationView = ({ subnetPool }: PP.SubnetPool) =>
+  q(api.systemSubnetPoolUtilizationView, { path: { pool: subnetPool } })
 const siloSubnetPoolList = (silo: string) =>
   q(api.siloSubnetPoolList, { path: { silo }, query: { limit: ALL_ISH } })
 
@@ -78,6 +81,7 @@ export async function clientLoader({ params }: LoaderFunctionArgs) {
       }
     }),
     queryClient.prefetchQuery(subnetPoolMemberList(selector).optionsFn()),
+    queryClient.prefetchQuery(subnetPoolUtilizationView(selector)),
     queryClient.fetchQuery(siloList).then((silos) => {
       for (const silo of silos.items) {
         queryClient.setQueryData(siloView({ silo: silo.id }).queryKey, silo)
@@ -154,6 +158,7 @@ export default function SubnetPoolPage() {
 function PoolProperties() {
   const poolSelector = useSubnetPoolSelector()
   const { data: pool } = usePrefetchedQuery(subnetPoolView(poolSelector))
+  const { data: utilization } = usePrefetchedQuery(subnetPoolUtilizationView(poolSelector))
 
   return (
     <PropertiesTable columns={2} className="-mt-8 mb-8">
@@ -162,9 +167,13 @@ function PoolProperties() {
       <PropertiesTable.Row label="IP version">
         <IpVersionBadge ipVersion={pool.ipVersion} />
       </PropertiesTable.Row>
-      {/* TODO: add utilization row once Nexus endpoint is implemented
-          https://github.com/oxidecomputer/omicron/issues/10109 */}
+      <PropertiesTable.Row label="Addresses remaining">
+        <span>
+          <UtilizationFraction {...utilization} />
+        </span>
+      </PropertiesTable.Row>
       <PropertiesTable.DateRow date={pool.timeCreated} label="Created" />
+      <PropertiesTable.DateRow date={pool.timeModified} label="Last Modified" />
     </PropertiesTable>
   )
 }
@@ -183,6 +192,7 @@ function MembersTable() {
   const { mutateAsync: removeMember } = useApiMutation(api.systemSubnetPoolMemberRemove, {
     onSuccess() {
       queryClient.invalidateEndpoint('systemSubnetPoolMemberList')
+      queryClient.invalidateEndpoint('systemSubnetPoolUtilizationView')
     },
   })
   const emptyState = (
diff --git a/app/pages/system/networking/SubnetPoolsPage.tsx b/app/pages/system/networking/SubnetPoolsPage.tsx
index 5a299167b..20cb35a81 100644
--- a/app/pages/system/networking/SubnetPoolsPage.tsx
+++ b/app/pages/system/networking/SubnetPoolsPage.tsx
@@ -27,10 +27,12 @@ import { IpVersionBadge } from '~/components/IpVersionBadge'
 import { useQuickActions } from '~/hooks/use-quick-actions'
 import { confirmDelete } from '~/stores/confirm-delete'
 import { addToast } from '~/stores/toast'
+import { SkeletonCell } from '~/table/cells/EmptyCell'
 import { makeLinkCell } from '~/table/cells/LinkCell'
 import { useColsWithActions, type MenuAction } from '~/table/columns/action-col'
 import { Columns } from '~/table/columns/common'
 import { useQueryTable } from '~/table/QueryTable'
+import { UtilizationFraction } from '~/ui/lib/BigNum'
 import { CreateLink } from '~/ui/lib/CreateButton'
 import { EmptyMessage } from '~/ui/lib/EmptyMessage'
 import { PageHeader, PageTitle } from '~/ui/lib/PageHeader'
@@ -49,10 +51,18 @@ const EmptyState = () => (
   />
 )
 
+function UtilizationCell({ pool }: { pool: string }) {
+  const { data } = useQuery(q(api.systemSubnetPoolUtilizationView, { path: { pool } }))
+  if (!data) return <SkeletonCell />
+  return (
+    <div>
+      <UtilizationFraction {...data} />
+    </div>
+  )
+}
+
 const colHelper = createColumnHelper<SubnetPool>()
 
-// TODO: add utilization column once Nexus endpoint is implemented
-// https://github.com/oxidecomputer/omicron/issues/10109
 const staticColumns = [
   colHelper.accessor('name', {
     cell: makeLinkCell((pool) => pb.subnetPool({ subnetPool: pool })),
@@ -62,6 +72,10 @@ const staticColumns = [
     header: 'Version',
     cell: (info) => <IpVersionBadge ipVersion={info.getValue()} />,
   }),
+  colHelper.display({
+    header: 'Addresses remaining',
+    cell: (info) => <UtilizationCell pool={info.row.original.name} />,
+  }),
   colHelper.accessor('timeCreated', Columns.timeCreated),
 ]
 
diff --git a/app/ui/lib/BigNum.tsx b/app/ui/lib/BigNum.tsx
index ffd2f782b..ea78494e2 100644
--- a/app/ui/lib/BigNum.tsx
+++ b/app/ui/lib/BigNum.tsx
@@ -23,3 +23,20 @@ export function BigNum({ num, className }: { num: number | bigint; className?: s
 
   return <Tooltip content={num.toLocaleString()}>{inner}</Tooltip>
 }
+
+/** Display `remaining / capacity` with BigNum formatting. */
+export function UtilizationFraction({
+  remaining,
+  capacity,
+}: {
+  remaining: number | bigint
+  capacity: number | bigint
+}) {
+  return (
+    <>
+      <BigNum className="text-raise" num={remaining} />
+      {' / '}
+      <BigNum className="text-secondary" num={capacity} />
+    </>
+  )
+}
diff --git a/mock-api/msw/handlers.ts b/mock-api/msw/handlers.ts
index ff3199ca1..cbda97ede 100644
--- a/mock-api/msw/handlers.ts
+++ b/mock-api/msw/handlers.ts
@@ -2511,25 +2511,31 @@ export const handlers = makeHandlers({
   systemSubnetPoolUtilizationView({ path, cookies }) {
     requireFleetViewer(cookies)
     const pool = lookup.subnetPool({ subnetPool: path.pool })
+    const bits = pool.ip_version === 'v4' ? 32 : 128
+
+    // Unlike IP pool utilization (which uses bigint arithmetic because IP
+    // ranges have arbitrary sizes), subnet sizes are always powers of 2, which
+    // are exactly representable as f64 up to 2^1023. So Math.pow is exact for
+    // each term and we don't need bigint intermediate arithmetic.
+    const subnetSize = (cidr: string) => {
+      const parsed = parseIpNet(cidr)
+      // mock data is always valid, so this is just for the type narrowing
+      if (parsed.type === 'error') return 0
+      return Math.pow(2, bits - parsed.width)
+    }
+
+    const capacity = R.pipe(
+      db.subnetPoolMembers,
+      R.filter((m) => m.subnet_pool_id === pool.id),
+      R.sumBy((m) => subnetSize(m.subnet))
+    )
+    const allocated = R.pipe(
+      db.externalSubnets,
+      R.filter((s) => s.subnet_pool_id === pool.id),
+      R.sumBy((s) => subnetSize(s.subnet))
+    )
 
-    // TODO: figure out why subnet pool utilization can't list remaining
-    // addresses like IP pools do and make this mock match omicron's behavior.
-    // Also, Math.pow(2, bits - prefix) overflows to Infinity for IPv6.
-    const members = db.subnetPoolMembers.filter((m) => m.subnet_pool_id === pool.id)
-
-    let capacity = 0
-    for (const member of members) {
-      const prefixMatch = member.subnet.match(/\/(\d+)$/)
-      const prefix = prefixMatch ? Number(prefixMatch[1]) : 0
-      const bits = pool.ip_version === 'v4' ? 32 : 128
-      capacity += Math.pow(2, bits - prefix)
-    }
-
-    const allocated = db.externalSubnets.filter(
-      (es) => es.subnet_pool_id === pool.id
-    ).length
-
-    return { allocated, capacity }
+    return { capacity, remaining: capacity - allocated }
   },
   siloSubnetPoolList({ path, query, cookies }) {
     requireFleetViewer(cookies)
diff --git a/test/e2e/subnet-pools.e2e.ts b/test/e2e/subnet-pools.e2e.ts
index e64b62916..d7a95a08e 100644
--- a/test/e2e/subnet-pools.e2e.ts
+++ b/test/e2e/subnet-pools.e2e.ts
@@ -25,10 +25,22 @@ test('Subnet pool list', async ({ page }) => {
   const table = page.getByRole('table')
   await expect(table.getByRole('row')).toHaveCount(5) // header + 4 pools
 
-  await expectRowVisible(table, { name: 'default-v4-subnet-pool' })
-  await expectRowVisible(table, { name: 'ipv6-subnet-pool' })
-  await expectRowVisible(table, { name: 'myriad-v4-subnet-pool' })
-  await expectRowVisible(table, { name: 'secondary-v4-subnet-pool' })
+  await expectRowVisible(table, {
+    name: 'default-v4-subnet-pool',
+    'Addresses remaining': '65,008 / 65,536',
+  })
+  await expectRowVisible(table, {
+    name: 'ipv6-subnet-pool',
+    'Addresses remaining': '79.2e27 / 79.2e27',
+  })
+  await expectRowVisible(table, {
+    name: 'myriad-v4-subnet-pool',
+    'Addresses remaining': '65,536 / 65,536',
+  })
+  await expectRowVisible(table, {
+    name: 'secondary-v4-subnet-pool',
+    'Addresses remaining': '65,536 / 65,536',
+  })
 })
 
 test('Subnet pool create', async ({ page }) => {
@@ -55,12 +67,27 @@ test('Subnet pool detail and members', async ({ page }) => {
 
   // Check properties table
   await expect(page.getByText('Default IPv4 subnet pool')).toBeVisible()
+  await expect(page.getByText('65,008 / 65,536')).toBeVisible()
 
   // Members tab should show existing member
   const membersTable = page.getByRole('table')
   await expectRowVisible(membersTable, { Subnet: '10.128.0.0/16' })
 })
 
+test('Addresses remaining in properties table', async ({ page }) => {
+  // pool with no allocations shows full capacity
+  await page.goto('/system/networking/subnet-pools/secondary-v4-subnet-pool')
+  await expect(page.getByText('65,536 / 65,536')).toBeVisible()
+
+  // pool with allocations shows remaining / capacity
+  await page.goto('/system/networking/subnet-pools/default-v4-subnet-pool')
+  await expect(page.getByText('65,008 / 65,536')).toBeVisible()
+
+  // large IPv6 pool shows abbreviated bignum
+  await page.goto('/system/networking/subnet-pools/ipv6-subnet-pool')
+  await expect(page.getByText('79.2e27 / 79.2e27')).toBeVisible()
+})
+
 test('Subnet pool add member', async ({ page }) => {
   await page.goto('/system/networking/subnet-pools/default-v4-subnet-pool')
 
@@ -76,6 +103,9 @@ test('Subnet pool add member', async ({ page }) => {
 
   await expectToast(page, 'Member added')
 
+  // utilization updates: /12 adds 2^20 = 1,048,576 addresses, pushing totals over 1M
+  await expect(page.getByText('1.1M / 1.1M')).toBeVisible()
+
   const table = page.getByRole('table')
   await expectRowVisible(table, { Subnet: '172.16.0.0/12' })
 })
@@ -90,6 +120,9 @@ test('Subnet pool remove member', async ({ page }) => {
 
   // The row should be gone
   await expect(page.getByRole('cell', { name: '172.20.0.0/16' })).toBeHidden()
+
+  // utilization drops to 0 / 0 after removing only member
+  await expect(page.getByText('0 / 0')).toBeVisible()
 })
 
 test('Subnet pool linked silos', async ({ page }) => {