diff --git a/e2e/playwright/point-click-assemblies.spec.ts b/e2e/playwright/point-click-assemblies.spec.ts
index b579518b5..88da75ada 100644
--- a/e2e/playwright/point-click-assemblies.spec.ts
+++ b/e2e/playwright/point-click-assemblies.spec.ts
@@ -143,28 +143,45 @@ test.describe('Point-and-click assemblies tests', () => {
         await scene.settled(cmdBar)
       })
 
-      await test.step('Insert a second time and expect error', async () => {
-        // TODO: revisit once we have clone with #6209
-        await insertPartIntoAssembly(
-          'bracket.kcl',
-          'bracket',
-          toolbar,
-          cmdBar,
-          page
-        )
+      await test.step('Insert a second time with the same name and expect error', async () => {
+        await toolbar.insertButton.click()
+        await cmdBar.selectOption({ name: 'bracket.kcl' }).click()
+        await cmdBar.expectState({
+          stage: 'arguments',
+          currentArgKey: 'localName',
+          currentArgValue: '',
+          headerArguments: { Path: 'bracket.kcl', LocalName: '' },
+          highlightedHeaderArg: 'localName',
+          commandName: 'Insert',
+        })
+        await page.keyboard.insertText('bracket')
+        await cmdBar.progressCmdBar()
+        await expect(
+          page.getByText('This variable name is already in use')
+        ).toBeVisible()
+      })
+
+      await test.step('Insert a second time with a different name and expect error', async () => {
+        await page.keyboard.insertText('2')
+        await cmdBar.progressCmdBar()
+        await cmdBar.expectState({
+          stage: 'review',
+          headerArguments: { Path: 'bracket.kcl', LocalName: 'bracket2' },
+          commandName: 'Insert',
+        })
+        await cmdBar.progressCmdBar()
         await editor.expectEditor.toContain(
           `
         import "cylinder.kcl" as cylinder
         import "bracket.kcl" as bracket
-        import "bracket.kcl" as bracket
+        import "bracket.kcl" as bracket2
         cylinder
         bracket
-        bracket
+        bracket2
       `,
           { shouldNormalise: true }
         )
-        await scene.settled(cmdBar)
-        await expect(page.locator('.cm-lint-marker-error')).toBeVisible()
+        // TODO: update once we have clone() with #6209
       })
     }
   )
diff --git a/src/lib/commandTypes.ts b/src/lib/commandTypes.ts
index e895dde18..b726a0cc9 100644
--- a/src/lib/commandTypes.ts
+++ b/src/lib/commandTypes.ts
@@ -220,6 +220,13 @@ export type CommandArgumentConfig<
             machineContext?: C
           ) => OutputType)
       defaultValueFromContext?: (context: C) => OutputType
+      validation?: ({
+        data,
+        context,
+      }: {
+        data: any
+        context: CommandBarContext
+      }) => Promise<boolean | string>
     }
   | {
       inputType: 'text'
@@ -343,6 +350,13 @@ export type CommandArgument<
             commandBarContext: ContextFrom<typeof commandBarMachine>,
             machineContext?: ContextFrom<T>
           ) => OutputType)
+      validation?: ({
+        data,
+        context,
+      }: {
+        data: any
+        context: CommandBarContext
+      }) => Promise<boolean | string>
     }
   | {
       inputType: 'path'
diff --git a/src/lib/createMachineCommand.ts b/src/lib/createMachineCommand.ts
index 4a8504940..969135840 100644
--- a/src/lib/createMachineCommand.ts
+++ b/src/lib/createMachineCommand.ts
@@ -211,6 +211,15 @@ export function buildCommandArgument<
       defaultValue: arg.defaultValue,
       ...baseCommandArgument,
     } satisfies CommandArgument<O, T> & { inputType: 'kcl' }
+  } else if (arg.inputType === 'string') {
+    return {
+      inputType: arg.inputType,
+      defaultValue: arg.defaultValueFromContext
+        ? arg.defaultValueFromContext(context)
+        : arg.defaultValue,
+      validation: arg.validation,
+      ...baseCommandArgument,
+    } satisfies CommandArgument<O, T> & { inputType: 'string' }
   } else {
     return {
       inputType: arg.inputType,
diff --git a/src/lib/kclCommands.ts b/src/lib/kclCommands.ts
index 004c36913..151310b46 100644
--- a/src/lib/kclCommands.ts
+++ b/src/lib/kclCommands.ts
@@ -133,6 +133,14 @@ export function kclCommands(commandProps: KclCommandConfig): Command[] {
             const path = context.argumentsToSubmit['path'] as string
             return getPathFilenameInVariableCase(path)
           },
+          validation: async ({ data, context }) => {
+            const variableExists = kclManager.variables[data.localName]
+            if (variableExists) {
+              return 'This variable name is already in use.'
+            }
+
+            return true
+          },
         },
       },
       onSubmit: (data) => {
diff --git a/src/machines/commandBarMachine.ts b/src/machines/commandBarMachine.ts
index fb45c2f81..6149c7d55 100644
--- a/src/machines/commandBarMachine.ts
+++ b/src/machines/commandBarMachine.ts
@@ -307,6 +307,7 @@ export const commandBarMachine = setup({
             context.currentArgument &&
             context.selectedCommand &&
             (argConfig?.inputType === 'selection' ||
+              argConfig?.inputType === 'string' ||
               argConfig?.inputType === 'selectionMixed') &&
             argConfig?.validation
           ) {