diff --git a/web/src/features/namespace/add-namespace-member-dialog.tsx b/web/src/features/namespace/add-namespace-member-dialog.tsx
index 11279d55..4dd077d2 100644
--- a/web/src/features/namespace/add-namespace-member-dialog.tsx
+++ b/web/src/features/namespace/add-namespace-member-dialog.tsx
@@ -224,10 +224,10 @@ export function AddNamespaceMemberDialog({ slug, children }: AddNamespaceMemberD
         ) : null}
 
         <DialogFooter className="sm:justify-center sm:space-x-3">
-          <Button variant="outline" onClick={() => handleOpenChange(false)}>
+          <Button type="button" variant="outline" onClick={() => handleOpenChange(false)}>
             {t('dialog.cancel')}
           </Button>
-          <Button onClick={handleAddMember} disabled={addMemberMutation.isPending}>
+          <Button type="button" onClick={handleAddMember} disabled={addMemberMutation.isPending}>
             {addMemberMutation.isPending ? t('members.addingMember') : t('members.addMember')}
           </Button>
         </DialogFooter>
diff --git a/web/src/pages/dashboard/namespace-members.tsx b/web/src/pages/dashboard/namespace-members.tsx
index d2e92bd0..42a9510b 100644
--- a/web/src/pages/dashboard/namespace-members.tsx
+++ b/web/src/pages/dashboard/namespace-members.tsx
@@ -197,6 +197,7 @@ export function NamespaceMembersPage() {
                                 <option value="ADMIN">{t('members.roleAdmin')}</option>
                               </Select>
                               <Button
+                                type="button"
                                 variant="outline"
                                 size="sm"
                                 disabled={roleValue === member.role || isSavingRole}
@@ -220,6 +221,7 @@ export function NamespaceMembersPage() {
                         </td>
                         <td className="p-4 text-right">
                           <Button
+                            type="button"
                             variant="destructive"
                             size="sm"
                             disabled={!canManageMembers || isOwner || isRemoving}
diff --git a/web/src/shared/hooks/use-skill-queries.ts b/web/src/shared/hooks/use-skill-queries.ts
index a04c704f..11d238c7 100644
--- a/web/src/shared/hooks/use-skill-queries.ts
+++ b/web/src/shared/hooks/use-skill-queries.ts
@@ -1,6 +1,7 @@
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
 import type { SkillSummary, SkillDetail, SkillVersion, SkillVersionDetail, SkillFile, SearchParams, PagedResponse, PublishResult, Namespace, NamespaceMember, ManagedNamespace, CreateNamespaceRequest, NamespaceCandidateUser, NamespaceRole } from '@/api/types'
 import { fetchJson, fetchText, getCsrfHeaders, meApi, namespaceApi, promotionApi, skillLifecycleApi, WEB_API_PREFIX } from '@/api/client'
+import { appendNamespaceMember, replaceNamespaceMemberRole } from '@/shared/lib/namespace-member-cache'
 import { normalizeSearchQuery } from '@/shared/lib/search-query'
 
 const PUBLISH_REQUEST_TIMEOUT_MS = 60_000
@@ -268,7 +269,11 @@ export function useAddNamespaceMember() {
 
   return useMutation({
     mutationFn: addNamespaceMember,
-    onSuccess: (_data, variables) => {
+    onSuccess: (member, variables) => {
+      queryClient.setQueryData<NamespaceMember[]>(
+        ['namespaces', variables.slug, 'members'],
+        (currentMembers) => appendNamespaceMember(currentMembers, member),
+      )
       invalidateNamespaceQueries(queryClient, variables.slug)
     },
   })
@@ -279,7 +284,11 @@ export function useUpdateNamespaceMemberRole() {
 
   return useMutation({
     mutationFn: updateNamespaceMemberRole,
-    onSuccess: (_data, variables) => {
+    onSuccess: (member, variables) => {
+      queryClient.setQueryData<NamespaceMember[]>(
+        ['namespaces', variables.slug, 'members'],
+        (currentMembers) => replaceNamespaceMemberRole(currentMembers, variables.userId, member.role),
+      )
       invalidateNamespaceQueries(queryClient, variables.slug)
     },
   })
diff --git a/web/src/shared/lib/namespace-member-cache.test.ts b/web/src/shared/lib/namespace-member-cache.test.ts
new file mode 100644
index 00000000..5ef85cb8
--- /dev/null
+++ b/web/src/shared/lib/namespace-member-cache.test.ts
@@ -0,0 +1,41 @@
+import { describe, expect, it } from 'vitest'
+import { appendNamespaceMember, replaceNamespaceMemberRole } from './namespace-member-cache'
+import type { NamespaceMember } from '@/api/types'
+
+const baseMember = (overrides: Partial<NamespaceMember>): NamespaceMember => ({
+  id: 1,
+  userId: 'user-1',
+  role: 'MEMBER',
+  createdAt: '2026-03-17T00:00:00',
+  ...overrides,
+})
+
+describe('appendNamespaceMember', () => {
+  it('appends a newly added member with the returned role', () => {
+    const members = [baseMember({})]
+    const addedMember = baseMember({ id: 2, userId: 'user-2', role: 'ADMIN' })
+
+    expect(appendNamespaceMember(members, addedMember)).toEqual([
+      members[0],
+      addedMember,
+    ])
+  })
+
+  it('replaces the existing member when the same user is returned again', () => {
+    const members = [baseMember({ role: 'MEMBER' })]
+    const updatedMember = baseMember({ role: 'ADMIN' })
+
+    expect(appendNamespaceMember(members, updatedMember)).toEqual([updatedMember])
+  })
+})
+
+describe('replaceNamespaceMemberRole', () => {
+  it('updates the member role in the current list', () => {
+    const members = [baseMember({}), baseMember({ id: 2, userId: 'user-2', role: 'MEMBER' })]
+
+    expect(replaceNamespaceMemberRole(members, 'user-2', 'ADMIN')).toEqual([
+      members[0],
+      { ...members[1], role: 'ADMIN' },
+    ])
+  })
+})
diff --git a/web/src/shared/lib/namespace-member-cache.ts b/web/src/shared/lib/namespace-member-cache.ts
new file mode 100644
index 00000000..917cd5a1
--- /dev/null
+++ b/web/src/shared/lib/namespace-member-cache.ts
@@ -0,0 +1,30 @@
+import type { NamespaceMember } from '@/api/types'
+
+export function appendNamespaceMember(
+  currentMembers: NamespaceMember[] | undefined,
+  nextMember: NamespaceMember,
+) {
+  const members = currentMembers ?? []
+  const existingIndex = members.findIndex((member) => member.userId === nextMember.userId)
+
+  if (existingIndex === -1) {
+    return [...members, nextMember]
+  }
+
+  return members.map((member, index) => (index === existingIndex ? nextMember : member))
+}
+
+export function replaceNamespaceMemberRole(
+  currentMembers: NamespaceMember[] | undefined,
+  userId: string,
+  role: string,
+) {
+  return (currentMembers ?? []).map((member) => (
+    member.userId === userId
+      ? {
+          ...member,
+          role,
+        }
+      : member
+  ))
+}