[rush] pnpm 11: allow supportedArchitectures setting

[nlochschmidt]

I have looked through the docs and related issues but didn't find anything that quite matches this issue.

Summary

Until pnpm 10 we could use the unsupportedPackageJsonSettings.pnpm.* in the pnpm-config.json to specify supportedArchitectures, but under pnpm 11, it no longer has an effect. Rush still copies it into the pnpm field of common/temp/package.json, but pnpm 11 no longer reads it. pnpm only prints a warning (see below) and rush install succeeds but the native dependencies are not installed.

Repro steps

1. rushVersion 5.179.0, pnpmVersion 11.26.0, useWorkspaces: true.

2. In common/config/rush/pnpm-config.json:

   "unsupportedPackageJsonSettings": {
     "pnpm": { "supportedArchitectures": { "libc": ["current", "musl"] } }
   }

3. Add a dependency with native extensions such as @statsig/statsig-node-core

4. rush install

Expected result: pnpm applies supportedArchitectures as it did with pnpm 10. Failing that, Rush should warn or fail because the setting cannot take effect.

Actual result: rush install runs successfully, and pnpm prints:

[WARN] The "pnpm" field in package.json is no longer read by pnpm. The following keys were ignored: "pnpm.supportedArchitectures". See https://pnpm.io/settings for the new home of each setting.

Details

environmentVariables in pnpm-config.json cannot be used for this either. pnpm 11 does not parse an object setting from pnpm_config_supported_architectures or npm_config_supported_architectures, so pnpm config get supported-architectures returns undefined. It only reads the setting from pnpm-workspace.yaml.

Proposed solutions:

1. Add a sibling escape hatch like unsupportedPackageJsonSettings but for pnpm-workspace.yaml.
2. Add a first-class supportedArchitectures field to pnpm-config.json.
3. Separately, warn loudly when unsupportedPackageJsonSettings.pnpm is non-empty under pnpm >= 11.

As a workaround, we use a local Rush plugin that appends the key to common/temp/pnpm-workspace.yaml in beforeInstall. However it does not apply to the installs that rush add/rush remove run, because those installs do not fire plugin hooks (see: #5168).

Standard questions

Question	Answer
@microsoft/rush globally installed version?	5.179.0
rushVersion from rush.json?	5.179.0
pnpmVersion, npmVersion, or yarnVersion from rush.json?	pnpm@11.26.0
(if pnpm) useWorkspaces from pnpm-config.json?	true
Operating system?	Mac and Linux
Would you consider contributing a PR?	Yes
Node.js version (node -v)?	24.20.0