diff --git a/README.md b/README.md
index 9cc0a86eb..e095fdec2 100644
--- a/README.md
+++ b/README.md
@@ -274,6 +274,10 @@ if (providerLabel) {
     visibility: 'show',
   }]);
 }
+const current = await api.keywords.list();               // settings:read
+await api.keywords.reorder(current.map(({ id }) => id), { // settings:write
+  caseSensitive: false, // default
+});
 const counts = await api.keywords.refreshCounts();        // email:read
 
 // Complete replacement: keywords omitted here are removed from the message.
@@ -301,8 +305,11 @@ compatibility aliases.
 
 `keywords.add()` is append-only and case-insensitive by id: it returns added
 and skipped definitions without overwriting the user's existing label name,
-colour, visibility, or order. Keyword discovery reports whether its bounded
-scan was complete.
+colour, visibility, or order. `keywords.reorder()` accepts a complete
+permutation of the existing label ids and changes only their order; missing,
+unknown, or duplicate ids are rejected without changing settings. Matching is
+case-insensitive by default; pass `{ caseSensitive: true }` to require exact id
+casing. Keyword discovery reports whether its bounded scan was complete.
 
 </details>
 
diff --git a/lib/__tests__/plugin-api-gates.test.ts b/lib/__tests__/plugin-api-gates.test.ts
index d66c92f7e..84abd3f8a 100644
--- a/lib/__tests__/plugin-api-gates.test.ts
+++ b/lib/__tests__/plugin-api-gates.test.ts
@@ -109,6 +109,8 @@ describe('native keyword extension API', () => {
       .toMatch(/lacks permission "settings:read"/);
     expect(await gateError(plugin(), 'keywords.add', [[]]))
       .toMatch(/lacks permission "settings:write"/);
+    expect(await gateError(plugin(), 'keywords.reorder', [[]]))
+      .toMatch(/lacks permission "settings:write"/);
 
     const reader = plugin({ permissions: ['settings:read'], grantedPermissions: ['settings:read'] });
     expect(await dispatchApiCall(reader, 'keywords.list', []))
@@ -152,6 +154,81 @@ describe('native keyword extension API', () => {
     expect(useSettingsStore.getState().emailKeywords).toEqual(before);
   });
 
+  it('reorders complete label sets without changing user metadata', async () => {
+    useSettingsStore.setState({
+      emailKeywords: [
+        { id: 'work', label: 'My Work', color: 'purple', visibility: 'hide' },
+        { id: 'shopping', label: 'Shopping', color: 'green', visibility: 'unread' },
+        { id: 'travel', label: 'Travel', color: 'blue' },
+      ],
+    });
+    const writer = plugin({ permissions: ['settings:write'], grantedPermissions: ['settings:write'] });
+
+    const result = await dispatchApiCall(writer, 'keywords.reorder', [[
+      'TRAVEL', 'work', 'shopping',
+    ]]);
+
+    expect(result).toEqual([
+      { id: 'travel', label: 'Travel', color: 'blue' },
+      { id: 'work', label: 'My Work', color: 'purple', visibility: 'hide' },
+      { id: 'shopping', label: 'Shopping', color: 'green', visibility: 'unread' },
+    ]);
+    expect(useSettingsStore.getState().emailKeywords).toEqual(result);
+  });
+
+  it('supports optional case-sensitive label id matching', async () => {
+    const original = [
+      { id: 'Work', label: 'Work', color: 'purple' },
+      { id: 'shopping', label: 'Shopping', color: 'green' },
+    ];
+    useSettingsStore.setState({ emailKeywords: original });
+    const writer = plugin({ permissions: ['settings:write'], grantedPermissions: ['settings:write'] });
+
+    await expect(dispatchApiCall(writer, 'keywords.reorder', [
+      ['SHOPPING', 'work'],
+      { caseSensitive: true },
+    ])).rejects.toThrow(/unknown label id/);
+    expect(useSettingsStore.getState().emailKeywords).toEqual(original);
+
+    await expect(dispatchApiCall(writer, 'keywords.reorder', [
+      ['shopping', 'Work'],
+      { caseSensitive: true },
+    ])).resolves.toEqual([original[1], original[0]]);
+  });
+
+  it('rejects invalid reorder options without changing settings', async () => {
+    const original = [{ id: 'work', label: 'Work', color: 'purple' }];
+    useSettingsStore.setState({ emailKeywords: original });
+    const writer = plugin({ permissions: ['settings:write'], grantedPermissions: ['settings:write'] });
+
+    for (const options of [true, { caseSensitive: 'yes' }, { unknown: true }]) {
+      await expect(dispatchApiCall(writer, 'keywords.reorder', [
+        ['work'], options,
+      ])).rejects.toThrow(/options/);
+      expect(useSettingsStore.getState().emailKeywords).toEqual(original);
+    }
+  });
+
+  it('rejects incomplete, duplicate, and unknown reorder ids atomically', async () => {
+    const original = [
+      { id: 'work', label: 'Work', color: 'purple' },
+      { id: 'shopping', label: 'Shopping', color: 'green' },
+    ];
+    useSettingsStore.setState({ emailKeywords: original });
+    const writer = plugin({ permissions: ['settings:write'], grantedPermissions: ['settings:write'] });
+
+    for (const ids of [
+      ['work'],
+      ['work', 'WORK'],
+      ['work', 'missing'],
+    ]) {
+      await expect(dispatchApiCall(writer, 'keywords.reorder', [ids])).rejects.toThrow(
+        /every existing label|duplicate label id|unknown label id/,
+      );
+      expect(useSettingsStore.getState().emailKeywords).toEqual(original);
+    }
+  });
+
   it('gates discovery and counts as email metadata', async () => {
     for (const method of ['jmap.getKeywords', 'keywords.discover', 'keywords.getCounts', 'keywords.refreshCounts']) {
       expect(await gateError(plugin(), method, [])).toMatch(/lacks permission "email:read"/);
diff --git a/lib/plugin-sandbox/host-api.ts b/lib/plugin-sandbox/host-api.ts
index c5d9cfe42..e8c5d7c36 100644
--- a/lib/plugin-sandbox/host-api.ts
+++ b/lib/plugin-sandbox/host-api.ts
@@ -128,11 +128,13 @@ const PERM_PER_METHOD: Record<string, Permission | null> = {
   'email.setKeyword': 'email:write',
   'email.removeKeyword': 'email:write',
   // Native keyword definitions are a deliberately narrow settings API: a
-  // plugin can read definitions or append missing ones, but cannot overwrite
-  // or remove user-managed tags. Discovery/counts reveal mail metadata and
-  // therefore use email:read rather than a settings permission.
+  // plugin can read definitions, append missing ones, or reorder the complete
+  // existing set, but cannot overwrite or remove user-managed tags.
+  // Discovery/counts reveal mail metadata and therefore use email:read rather
+  // than a settings permission.
   'keywords.list': 'settings:read',
   'keywords.add': 'settings:write',
+  'keywords.reorder': 'settings:write',
   'keywords.discover': 'email:read',
   'keywords.getCounts': 'email:read',
   'keywords.refreshCounts': 'email:read',
@@ -909,6 +911,57 @@ function doKeywordsAdd(value: unknown): { added: KeywordDefinition[]; skipped: s
   return { added: added.map((keyword) => ({ ...keyword })), skipped };
 }
 
+function doKeywordsReorder(value: unknown, rawOptions?: unknown): KeywordDefinition[] {
+  if (!Array.isArray(value)) {
+    throw new Error('keywords.reorder: ids must be an array');
+  }
+  if (value.some((id) => typeof id !== 'string')) {
+    throw new Error('keywords.reorder: ids must contain only strings');
+  }
+  if (rawOptions !== undefined && !isPlainObject(rawOptions)) {
+    throw new Error('keywords.reorder: options must be an object');
+  }
+  const options = rawOptions as Record<string, unknown> | undefined;
+  if (options && Object.keys(options).some((key) => key !== 'caseSensitive')) {
+    throw new Error('keywords.reorder: options contains an unknown property');
+  }
+  if (options?.caseSensitive !== undefined && typeof options.caseSensitive !== 'boolean') {
+    throw new Error('keywords.reorder: options.caseSensitive must be a boolean');
+  }
+  const caseSensitive = options?.caseSensitive === true;
+  const normalizeId = (id: string) => caseSensitive ? id : id.toLowerCase();
+
+  const existing = useSettingsStore.getState().emailKeywords;
+  if (value.length !== existing.length) {
+    throw new Error('keywords.reorder: ids must contain every existing label exactly once');
+  }
+
+  const byId = new Map(existing.map((keyword) => [normalizeId(keyword.id), keyword]));
+  if (byId.size !== existing.length) {
+    throw new Error('keywords.reorder: existing label ids are not unique');
+  }
+
+  const seen = new Set<string>();
+  const reordered: KeywordDefinition[] = [];
+  for (const id of value as string[]) {
+    const normalizedId = normalizeId(id);
+    if (seen.has(normalizedId)) {
+      throw new Error(`keywords.reorder: duplicate label id: ${id}`);
+    }
+    const keyword = byId.get(normalizedId);
+    if (!keyword) {
+      throw new Error(`keywords.reorder: unknown label id: ${id}`);
+    }
+    seen.add(normalizedId);
+    reordered.push(keyword);
+  }
+
+  // Reuse the existing definitions verbatim so ordering cannot change a
+  // label's name, colour, visibility, id casing, or any future metadata.
+  useSettingsStore.setState({ emailKeywords: reordered });
+  return reordered.map((keyword) => ({ ...keyword }));
+}
+
 function assertKeywordIds(value: unknown): string[] | undefined {
   if (value === undefined || value === null) return undefined;
   if (!Array.isArray(value) || value.length > MAX_PLUGIN_KEYWORD_DEFINITIONS) {
@@ -1250,6 +1303,7 @@ export async function dispatchApiCall(
 
     case 'keywords.list': return doKeywordsList();
     case 'keywords.add': return doKeywordsAdd(args[0]);
+    case 'keywords.reorder': return doKeywordsReorder(args[0], args[1]);
     case 'keywords.discover': return doKeywordsDiscover(args[0]);
     case 'keywords.getCounts': return doKeywordsGetCounts(args[0]);
     case 'keywords.refreshCounts': return doKeywordsRefreshCounts();
diff --git a/lib/plugin-sandbox/protocol.ts b/lib/plugin-sandbox/protocol.ts
index 36aa0998b..56546ecc5 100644
--- a/lib/plugin-sandbox/protocol.ts
+++ b/lib/plugin-sandbox/protocol.ts
@@ -254,7 +254,7 @@ export const API_METHODS = [
   // Email keyword mutations (JMAP Email/set keyword patches).
   'email.setKeyword', 'email.removeKeyword',
   // Native tag definitions, discovery, and sidebar counts.
-  'keywords.list', 'keywords.add', 'keywords.discover', 'keywords.getCounts', 'keywords.refreshCounts',
+  'keywords.list', 'keywords.add', 'keywords.reorder', 'keywords.discover', 'keywords.getCounts', 'keywords.refreshCounts',
   // Message-list category tabs (Gmail-style inbox tabs).
   'tabs.set', 'tabs.clear', 'tabs.getState', 'tabs.categorize', 'tabs.refreshCounts',
   // Sieve integration for delivery-time classification plugins.
diff --git a/lib/plugin-sandbox/runtime.tsx b/lib/plugin-sandbox/runtime.tsx
index 978cc7722..12d7be36b 100644
--- a/lib/plugin-sandbox/runtime.tsx
+++ b/lib/plugin-sandbox/runtime.tsx
@@ -340,8 +340,8 @@ function buildPluginApi(manifest: PluginManifest) {
     },
     // Native sidebar tag definitions. Definition reads/writes use the existing
     // settings permissions; server discovery and message counts use email:read.
-    // add() is intentionally append-only: it never overwrites or removes tags
-    // the user has already named, coloured, hidden, or reordered.
+    // add() is intentionally append-only. reorder() requires a complete
+    // permutation of existing ids. Neither method overwrites or removes tags.
     keywords: {
       list: () => callApi('keywords.list', []) as Promise<PluginKeywordDefinition[]>,
       add: (definitions: PluginKeywordDefinitionInput[]) =>
@@ -349,6 +349,8 @@ function buildPluginApi(manifest: PluginManifest) {
           added: PluginKeywordDefinition[];
           skipped: string[];
         }>,
+      reorder: (ids: string[], options?: { caseSensitive?: boolean }) =>
+        callApi('keywords.reorder', [ids, options]) as Promise<PluginKeywordDefinition[]>,
       discover: (options?: { limit?: number }) =>
         callApi('keywords.discover', [options]) as Promise<{
           keywords: Record<string, number>;