diff --git a/.american-spelling-allow b/.american-spelling-allow
new file mode 100644
index 0000000..9c285d2
--- /dev/null
+++ b/.american-spelling-allow
@@ -0,0 +1,4 @@
+# Words and paths the American-spelling check accepts (scripts/american_spelling.py in ericdahl-dev/.github).
+
+# Vendored Yarn release binary, checked in by `yarn set version`; not our code.
+path: .yarn/releases/
diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index bb7fb29..dd95d9a 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -30,7 +30,7 @@ app/
   api/
     ingress/[routeSlug]/    # Public webhook ingestion endpoint
     nodes/pull/             # Node event polling endpoint
-    nodes/ack/              # Node event acknowledgement endpoint
+    nodes/ack/              # Node event acknowledgment endpoint
     admin/                  # Admin API routes (events, nodes, routes)
     auth/                   # Auth-related API routes
     version/                # Version endpoint
diff --git a/app/dashboard/events/page.tsx b/app/dashboard/events/page.tsx
index b725d77..4cbe44d 100644
--- a/app/dashboard/events/page.tsx
+++ b/app/dashboard/events/page.tsx
@@ -48,7 +48,7 @@ export default async function DashboardEventsPage() {
       <DashboardPageHeader
         eyebrow="Events"
         title="Delivery events"
-        description="Inspect queued webhook deliveries, acknowledgements, and failures."
+        description="Inspect queued webhook deliveries, acknowledgments, and failures."
       />
 
       <EventsClient
diff --git a/tests/dashboard/routes-page.test.ts b/tests/dashboard/routes-page.test.ts
index 154c18f..483d0b8 100644
--- a/tests/dashboard/routes-page.test.ts
+++ b/tests/dashboard/routes-page.test.ts
@@ -51,7 +51,7 @@ describe('dashboard routes page', () => {
     mockDbRoutesOrderBy.mockResolvedValue([]);
     mockDbNodesOrderBy.mockReset();
     mockDbNodesOrderBy.mockResolvedValue([{ id: 'node-1', name: 'My Node' }]);
-    // Restore the routes/nodes alternating behaviour on from()
+    // Restore the routes/nodes alternating behavior on from()
     mockDbSelectFrom.mockReset();
     mockDbSelectFrom
       .mockReturnValueOnce({ leftJoin: mockDbRoutesLeftJoin })
diff --git a/tests/http/headers.test.ts b/tests/http/headers.test.ts
index d6abd0d..354c1a1 100644
--- a/tests/http/headers.test.ts
+++ b/tests/http/headers.test.ts
@@ -20,7 +20,7 @@ describe('headersToObject', () => {
     expect(result['x-custom-header']).toBe('value');
   });
 
-  test('normalises header names to lowercase', () => {
+  test('normalizes header names to lowercase', () => {
     const headers = new Headers();
     headers.append('X-Request-ID', 'abc-123');
 
diff --git a/tests/lib/ws/connection-manager.test.ts b/tests/lib/ws/connection-manager.test.ts
index ad86d5a..43db4e2 100644
--- a/tests/lib/ws/connection-manager.test.ts
+++ b/tests/lib/ws/connection-manager.test.ts
@@ -48,7 +48,7 @@ describe('connection-manager', () => {
     expect(isConnected('node-1')).toBe(false);
   });
 
-  test('pushEventToNode sends serialised data to the WebSocket', async () => {
+  test('pushEventToNode sends serialized data to the WebSocket', async () => {
     const { addConnection, pushEventToNode } = await import(
       '@/app/lib/ws/connection-manager'
     );
@@ -81,7 +81,7 @@ describe('connection-manager', () => {
     expect(mockSend).not.toHaveBeenCalled();
   });
 
-  test('global map is initialised on first import if not present', async () => {
+  test('global map is initialized on first import if not present', async () => {
     global.__clawproxyWsConnections = undefined;
     await import('@/app/lib/ws/connection-manager');
     expect(global.__clawproxyWsConnections).toBeInstanceOf(Map);