diff --git a/src/components/FileMachineProvider.tsx b/src/components/FileMachineProvider.tsx
index b72027df7..4389f5c6d 100644
--- a/src/components/FileMachineProvider.tsx
+++ b/src/components/FileMachineProvider.tsx
@@ -34,7 +34,8 @@ import { settingsActor, useSettings } from 'machines/appMachine'
 import { createRouteCommands } from 'lib/commandBarConfigs/routeCommandConfig'
 import { useToken } from 'machines/appMachine'
 import { createNamedViewsCommand } from 'lib/commandBarConfigs/namedViewsConfig'
-import { reportRejection } from 'lib/trap'
+import { err, reportRejection } from 'lib/trap'
+import { newKclFile } from 'lang/project'
 
 type MachineContext<T extends AnyStateMachine> = {
   state: StateFrom<T>
@@ -248,7 +249,12 @@ export const FileMachineProvider = ({
                 createdPath
               )
             } else {
-              await window.electron.writeFile(createdPath, input.content ?? '')
+              const codeToWrite = newKclFile(
+                input.content ?? '',
+                settings.modeling.defaultUnit.current
+              )
+              if (err(codeToWrite)) return Promise.reject(codeToWrite)
+              await window.electron.writeFile(createdPath, codeToWrite)
             }
           }
 
@@ -277,7 +283,12 @@ export const FileMachineProvider = ({
             })
             createdName = name
             createdPath = path
-            await window.electron.writeFile(createdPath, input.content ?? '')
+            const codeToWrite = newKclFile(
+              input.content ?? '',
+              settings.modeling.defaultUnit.current
+            )
+            if (err(codeToWrite)) return Promise.reject(codeToWrite)
+            await window.electron.writeFile(createdPath, codeToWrite)
           }
 
           return {
diff --git a/src/components/ProjectsContextProvider.tsx b/src/components/ProjectsContextProvider.tsx
index f1d1448ef..1f59ec545 100644
--- a/src/components/ProjectsContextProvider.tsx
+++ b/src/components/ProjectsContextProvider.tsx
@@ -32,6 +32,8 @@ import {
 } from 'lib/constants'
 import { codeManager, kclManager } from 'lib/singletons'
 import { Project } from 'lib/project'
+import { newKclFile } from 'lang/project'
+import { err } from 'lib/trap'
 
 type MachineContext<T extends AnyStateMachine> = {
   state?: StateFrom<T>
@@ -120,7 +122,13 @@ const ProjectsContextWeb = ({ children }: { children: React.ReactNode }) => {
         createFile: fromPromise(async ({ input }) => {
           // Browser version doesn't navigate, just overwrites the current file
           clearImportSearchParams()
-          codeManager.updateCodeStateEditor(input.code || '')
+
+          const codeToWrite = newKclFile(
+            input.code ?? '',
+            settings.modeling.defaultUnit.current
+          )
+          if (err(codeToWrite)) return Promise.reject(codeToWrite)
+          codeManager.updateCodeStateEditor(codeToWrite)
           await codeManager.writeToFile()
           await kclManager.executeCode(true)
 
@@ -412,7 +420,12 @@ const ProjectsContextDesktop = ({
           })
 
           fileName = name
-          await window.electron.writeFile(path, input.code || '')
+          const codeToWrite = newKclFile(
+            input.code ?? '',
+            settings.modeling.defaultUnit.current
+          )
+          if (err(codeToWrite)) return Promise.reject(codeToWrite)
+          await window.electron.writeFile(path, codeToWrite)
 
           return {
             message,
diff --git a/src/lang/project.ts b/src/lang/project.ts
new file mode 100644
index 000000000..08be8b7c1
--- /dev/null
+++ b/src/lang/project.ts
@@ -0,0 +1,28 @@
+import { UnitLength } from '@rust/kcl-lib/bindings/ModelingCmd'
+import {
+  changeKclSettings,
+  DEFAULT_DEFAULT_ANGLE_UNIT,
+  unitAngleToUnitAng,
+  unitLengthToUnitLen,
+} from './wasm'
+import { DEFAULT_DEFAULT_LENGTH_UNIT } from 'lib/settings/settingsTypes'
+
+/**
+ * Create a new KCL file with the given initial content and default length unit.
+ */
+export function newKclFile(
+  initialContent: string,
+  defaultLengthUnit: UnitLength
+): string | Error {
+  // If the default length unit is the same as the default default length unit,
+  // there's no need to add the attribute.
+  if (defaultLengthUnit === DEFAULT_DEFAULT_LENGTH_UNIT) {
+    return initialContent
+  }
+
+  return changeKclSettings(initialContent, {
+    defaultLengthUnits: unitLengthToUnitLen(defaultLengthUnit),
+    defaultAngleUnits: unitAngleToUnitAng(DEFAULT_DEFAULT_ANGLE_UNIT),
+    stdPath: null,
+  })
+}