Reproduction link or steps

A repository-style minimal reproduction (mirrors the test added in #9329):

.
├── entry.js
├── route.js
├── child.js
└── node_modules/react/
    ├── package.json
    ├── index.js
    ├── jsx-runtime.js
    └── cjs/
        ├── react.production.js
        └── react-jsx-runtime.production.js

entry.js:

import React from 'react';
import { jsx } from 'react/jsx-runtime';

console.log('entry', React.version, jsx('main', {}));
import('./route.js');

route.js:

import React from 'react';
import { jsx } from 'react/jsx-runtime';

console.log('route', React.version, jsx('route', {}));
import('./child.js');

child.js:

import { jsx } from 'react/jsx-runtime';

console.log('child', jsx('child', {}));

node_modules/react/package.json:

{
  "name": "react",
  "main": "./index.js",
  "exports": {
    ".": "./index.js",
    "./jsx-runtime": "./jsx-runtime.js"
  }
}

node_modules/react/index.js:

'use strict'
module.exports = require('./cjs/react.production.js')

node_modules/react/jsx-runtime.js:

'use strict'
module.exports = require('./cjs/react-jsx-runtime.production.js')

node_modules/react/cjs/react.production.js:

'use strict'
exports.version = '19'

node_modules/react/cjs/react-jsx-runtime.production.js:

'use strict'
exports.jsx = (type) => ({ type })
exports.jsxs = exports.jsx
exports.Fragment = Symbol.for('react.fragment')

Build with a single user entry (entry.js).

What is expected?

All consumers of react/jsx-runtime (entry, route, child) are reachable through the same user entry, so its modules should merge into entry.js. Output should be 3 chunks:

- child.js (dynamic entry)
- entry.js (user entry, contains react + jsx-runtime modules)
- route.js (dynamic entry)

What is actually happening?

A separate jsx-runtime.js common chunk is emitted, even though there is no other user entry that could share it:

- child.js                  (dynamic entry)
- entry.js                  (user entry)
- jsx-runtime.js            (common chunk, exports ["n", "r", "t"])  <-- unexpected
- route.js                  (dynamic entry)

Root cause (per #9329): when multiple pending common chunks should all merge into the same target entry, the optimizer's would_create_circular_dependency check treats sibling pending merges as still external, so they appear to form a transient cycle and get split into a standalone common chunk.

System Info

rolldown: 1.0.0-rc.18 (also reproducible on current main @ d3ae8ba2f)
OS: Windows 11

Any additional comments?

• Surfaces with React's CJS react/jsx-runtime facade (module.exports = require('./cjs/...')) when combined with nested dynamic imports.
• Fix proposed in fix: Fix same-target common chunk merge cycle check #9329 — expands the cycle check to treat all same-target pending merges as already collapsed into the target.
• Related prior fix: fix: reduce false positives in chunk optimizer circular dependency detection #9049 / Chunk optimizer circular dependency detection blocks too many legitimate merges since #8371 #9093.