packageManager definition

When I do a pnpm install on my laptop, I have the following error and package.json is automatically updated ( "packageManager": "pnpm@9.9.0+sha512.60c18acd138bff695d339be6ad13f7e936eea6745660d4cc4a776d5247c540d0edee1a563695c183a66eb917ef88f2b4feb1fc25f32a7adcadc7aaf3438e99c1"):

! The local project doesn't define a 'packageManager' field. Corepack will now add one referencing pnpm@9.9.0+sha512.60c18acd138bff695d339be6ad13f7e936eea6745660d4cc4a776d5247c540d0edee1a563695c183a66eb917ef88f2b4feb1fc25f32a7adcadc7aaf3438e99c1.
! For more details about this field, consult the documentation at https://nodejs.org/api/packages.html#packagemanager

It seems that Corepack automatically detects that my project is missing the packageManager field.