Upgrading to @types/react@v19+ and @types/react-dom@v19+ cannot find namespace 'JSX'

[chris-dura]

I have a boilerplate project setup using tsup and react@v19...

  "dependencies": {
    "react": "^19.0.0",
    "react-dom": "^19.0.0"
  },
  "devDependencies": {
    "@repo/eslint-config": "*",
    "@repo/release-it-config": "*",
    "@repo/typescript-config": "*",
    "@types/react": "18.3.14",
    "@types/react-dom": "18.3.2",
    "eslint": "^9.18.0",
    "tsup": "^8.3.5",
    "typescript": "^5.7.3"
  },

But, when I try to upgrade the @types/react and @types/react-dom, tsup throws a TS2503: Cannot find namespace 'JSX' error.

...
DTS Build start
│ src/button.tsx(6,62): error TS2503: Cannot find namespace 'JSX'.
│ 
│ Error: error occurred in dts build
│     at Worker.<anonymous> (/Users/code/my-project/node_modules/tsup/dist/index.js:1541:26)
│     at Worker.emit (node:events:524:28)
│     at MessagePort.<anonymous> (node:internal/worker:267:53)
│     at [nodejs.internal.kHybridDispatch] (node:internal/event_target:827:20)
│     at MessagePort.<anonymous> (node:internal/per_context/messageport:23:28)
│ DTS Build error
│ npm error Lifecycle script `build` failed with error:
│ npm error code 1
│ npm error path /Users/code/my-project/packages/lib
│ npm error workspace [email protected]
│ npm error location /Users/code/my-project/packages/lib
│ npm error command failed
│ npm error command sh -c tsup
│ 
│ command finished with error: command (/Users/code/my-project/packages/lib) /Users/P2185561/.nvm/versions/node/v22.13.1/bin/npm run build exited (1)