Bug: Suspense components rendered by renderToReadableStream() cause render abort when served with Bun

[jmuzina]

React version: 19.0.0

Steps To Reproduce

1. Install Bun and Node
2. Clone my reproduction repo
3. Install dependencies with Bun: bun install
4. Run React server with Node: bun run ssr:node. Open the app and see that the suspended Button component resolves after 2 seconds and no errors are thrown in the serverside or clientside consoles.
5. Run React server with Bun; bun run ssr:bun. Open the app and see that the Button component remains suspended after 2 seconds, is resolved in the serverside console but not the clientside console, and the following error is thrown in the server console:

8169 |   try {
8170 |     var abortableTasks = request.abortableTasks;
8171 |     if (0 < abortableTasks.size) {
8172 |       var error =
8173 |         void 0 === reason
8174 |           ? Error("The render was aborted by the server without a reason.")
                   ^
error: The render was aborted by the server without a reason.
      at abort (/home/jmuzina/software/work/canonical/repos/react-repro/node_modules/react-dom/cjs/react-dom-server.bun.development.js:8174:13)
      at cancel (/home/jmuzina/software/work/canonical/repos/react-repro/node_modules/react-dom/cjs/react-dom-server.bun.development.js:8262:17)
      at close (3:17)

6. Cause an app re-render by clicking the "Increment" button. See that the lazy button is resolved after 2 seconds (the "click me" button is rendered and the clientside log reports the lazy component has been resolved).

Link to code example: https://github.com/jmuzina/react-repro

The current behavior

• Node can stream responses compatible with React.Suspense by using react-dom.renderToPipeableStream().
• Bun can stream responses with react-dom.renderToReadableStream(), but any Suspense boundaries are not resolved until after a re-render, and the first render of a Suspense boundary is aborted on the serverside with no reason.

The expected behavior

Node and Bun can both stream responses compatible with React.Suspense.