diff --git a/apps/sim/app/api/desktop/tool/authorize/route.test.ts b/apps/sim/app/api/desktop/tool/authorize/route.test.ts
index 0b833983df9..6d965335655 100644
--- a/apps/sim/app/api/desktop/tool/authorize/route.test.ts
+++ b/apps/sim/app/api/desktop/tool/authorize/route.test.ts
@@ -87,6 +87,25 @@ describe('desktop tool authorization', () => {
     expect(claimPendingAsyncToolCall).toHaveBeenCalledWith('browser-tool', 'desktop-browser')
   })
 
+  it('never returns presentation activity as an executable browser argument', async () => {
+    const fields = [{ elementId: 1, kind: 'text', text: 'a' }]
+    getAsyncToolCall.mockResolvedValueOnce({
+      toolCallId: 'form-tool',
+      runId: 'run-1',
+      status: 'pending',
+      toolName: 'browser_fill_form',
+      args: { activity: { description: 'Filling the form' }, fields },
+    })
+
+    const response = await POST(request('form-tool'))
+    expect(response.status).toBe(200)
+    expect(await response.json()).toEqual({
+      chatId: 'chat-1',
+      toolName: 'browser_fill_form',
+      args: { fields },
+    })
+  })
+
   it('rejects retired browser tools retained only for history', async () => {
     getAsyncToolCall.mockResolvedValueOnce({
       toolCallId: 'retired-browser-tool',
diff --git a/apps/sim/app/api/desktop/tool/authorize/route.ts b/apps/sim/app/api/desktop/tool/authorize/route.ts
index fb735203a7a..9a657073b1e 100644
--- a/apps/sim/app/api/desktop/tool/authorize/route.ts
+++ b/apps/sim/app/api/desktop/tool/authorize/route.ts
@@ -1,6 +1,6 @@
 import { isCurrentBrowserToolName } from '@sim/browser-protocol'
 import { isTerminalToolName } from '@sim/terminal-protocol'
-import { isRecordLike } from '@sim/utils/object'
+import { isRecordLike, omit } from '@sim/utils/object'
 import { type NextRequest, NextResponse } from 'next/server'
 import { authorizeDesktopToolContract } from '@/lib/api/contracts/desktop-tool-authorization'
 import { parseRequest } from '@/lib/api/server'
@@ -24,7 +24,8 @@ import { isUserLocalVfsToolCall } from '@/lib/mothership/tools/local-filesystem'
  * Electron calls this endpoint from the main process before every privileged
  * native model action. It returns only server-persisted canonical tool args;
  * Electron validates local-file requests against them and uses them directly
- * for browser and terminal tools.
+ * for browser and terminal tools. The presentation-only `activity` field is
+ * dropped: desktop actions reject arguments they do not declare.
  */
 export const POST = withRouteHandler(async (request: NextRequest) => {
   const { userId, isAuthenticated } = await authenticateCopilotRequestSessionOnly()
@@ -117,7 +118,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
 
   return NextResponse.json({
     toolName: toolCall.toolName,
-    args,
+    args: omit(args, ['activity']),
     chatId: run.chatId,
   })
 })