esm-unsupported: Required ESM sandbox capabilities are unavailable

Cause

The browser failed the ESM sandbox's dynamic multiple-import-map check. In a separate same-origin iframe, qiankun injects an import map and executes a module, then adds a second map and executes another module. A module loading failure in either step produces this error.

The check runs before fetching, rewriting, or executing the micro-app's ESM modules. Its result is reused within the host document. Classic scripts do not trigger the check.

Troubleshooting

1. Check Browser support for the native ESM requirements. Support for ES modules or a single import map is insufficient.
2. Inspect the console for CSP violations. Enforced CSP restrictions normally produce esm-capability-check-failed, but this code does not replace a full CSP investigation.
3. Catch microApp.mountPromise and inspect error instanceof QiankunError and error.code instead of matching browser error messages.

Resolution

Use a supported browser, or provide a Classic build entry for the host to select. qiankun 3.0 provides no ESM sandbox fallback. Disabling the sandbox does not preserve isolation as a compatibility fallback. Do not require users to change experimental browser preferences.

If the check cannot finish, qiankun reports esm-capability-check-failed: ESM capability check could not complete.

Related

• Browser support
• Error codes and solutions
• esm-unsupported：ESM 沙箱所需能力不可用