polyfill structuredclone on legacy browsers

Fixes APP-T4SK

package.json

@@ -155,6 +155,7 @@
     "@types/invariant": "^2.2.37",
     "@types/lodash.throttle": "^4.1.9",
     "@types/node": "^24.12.2",
+    "@ungap/structured-clone": "1.3.1",
     "array.prototype.findlast": "^1.2.3",
     "babel-plugin-transform-remove-console": "^6.9.4",
     "bcp-47": "^2.1.0",
@@ -284,6 +285,7 @@
     "@types/psl": "1.1.1",
     "@types/react": "^19.2.17",
     "@types/react-dom": "^19.2.3",
+    "@types/ungap__structured-clone": "1.2.0",
     "@typescript/native": "npm:typescript@^7.0.2",
     "babel-jest": "^29.7.0",
     "babel-plugin-module-resolver": "^5.0.2",

pnpm-lock.yaml

@@ -410,6 +410,9 @@ importers:
       '@types/node':
         specifier: ^24.12.2
         version: 24.12.4
+      '@ungap/structured-clone':
+        specifier: 1.3.1
+        version: 1.3.1
       array.prototype.findlast:
         specifier: ^1.2.3
         version: 1.2.5
@@ -792,6 +795,9 @@ importers:
       '@types/react-dom':
         specifier: ^19.2.3
         version: 19.2.4(@types/react@19.2.18)
+      '@types/ungap__structured-clone':
+        specifier: 1.2.0
+        version: 1.2.0
       '@typescript/native':
         specifier: npm:typescript@^7.0.2
         version: typescript@7.0.2
@@ -3945,6 +3951,9 @@ packages:
   '@types/tough-cookie@4.0.5':
     resolution: {integrity: sha512-/Ad8+nIOV7Rl++6f1BdKxFSMgmoqEoYbHRpPcx3JEfv8VRsQe9Z4mCXeJBzxs7mbHY/XOZZuXlRNfhpVPbs6ZA==}
 
+  '@types/ungap__structured-clone@1.2.0':
+    resolution: {integrity: sha512-ZoaihZNLeZSxESbk9PUAPZOlSpcKx81I1+4emtULDVmBLkYutTcMlCj2K9VNlf9EWODxdO6gkAqEaLorXwZQVA==}
+
   '@types/use-sync-external-store@0.0.6':
     resolution: {integrity: sha512-zFDAD+tlpf2r4asuHEj0XH6pY6i0g5NeAHPn+15wk3BV6JA69eERFXC1gyGThDkVa1zCyKr5jox1+2LbV/AMLg==}
 
@@ -13426,6 +13435,8 @@ snapshots:
 
   '@types/tough-cookie@4.0.5': {}
 
+  '@types/ungap__structured-clone@1.2.0': {}
+
   '@types/use-sync-external-store@0.0.6': {}
 
   '@types/ws@8.18.1':

src/platform/polyfills.web.test.ts

@@ -0,0 +1,29 @@
+import {RichText} from '@bsky/sdk/richtext'
+
+describe('web polyfills', () => {
+  const nativeStructuredClone = globalThis.structuredClone
+
+  afterEach(() => {
+    globalThis.structuredClone = nativeStructuredClone
+  })
+
+  it('supports rich text when structuredClone is unavailable', async () => {
+    Reflect.deleteProperty(globalThis, 'structuredClone')
+
+    let structuredCloneReady: Promise<void> | undefined
+    jest.isolateModules(() => {
+      const polyfills =
+        require('./polyfills.web') as typeof import('./polyfills.web')
+      structuredCloneReady = polyfills.structuredCloneReady
+    })
+    await structuredCloneReady
+
+    const richText = new RichText(
+      {text: 'hello\n\n\nworld'},
+      {cleanNewlines: true},
+    )
+
+    expect(richText.text).toBe('hello\n\nworld')
+    expect(richText.clone()).toEqual(richText)
+  })
+})

src/platform/polyfills.web.ts

@@ -1,6 +1,16 @@
 import 'array.prototype.findlast/auto'
 import 'setimmediate'
 
+export const structuredCloneReady: Promise<void> =
+  typeof globalThis.structuredClone === 'function'
+    ? Promise.resolve()
+    : import('@ungap/structured-clone').then(({default: structuredClone}) => {
+        if (typeof globalThis.structuredClone !== 'function') {
+          globalThis.structuredClone =
+            structuredClone as typeof globalThis.structuredClone
+        }
+      })
+
 if (process.env.NODE_ENV !== 'production') {
   // In development, react-native-web's <View> tries to validate that
   // text is wrapped into <Text>. It doesn't catch all cases but is useful.
@@ -30,5 +40,3 @@ if (process.env.NODE_ENV !== 'production') {
     }
   }
 }
-
-export {}