Inconsistency in the typing of the custom property between fields and collections/globals

[jhb-dev]

Describe the Bug

I noticed an inconsistency in the typing of the custom property between fields and collections/globals which makes it hard to build well-typed plugins.

For fields, the custom property is nicely typeable via module augmentation:

declare module 'payload' {
  export interface FieldCustom {
       'plugin-import-export'?: {
           // plugin-specific field props...
       }
  }
}

This works because the field config uses the exported FieldCustom type:

payload/packages/payload/src/fields/config/types.ts

Line 511 in bd9f15f

custom?: FieldCustom

This is what the Import/Export plugin uses, for example.

However, for collection/global configs, the custom property is currently not typeable in the same way. It is defined as:

payload/packages/payload/src/globals/config/types.ts

Line 137 in bd9f15f

custom?: Record<string, any>

Because of this, plugins that require configuration on the collection/global level via custom cannot provide proper TypeScript types for these options. You lose type safety and auto-completion exactly where plugins often need structured configuration.

Something like the following currently has no effect on the types:

declare module 'payload' {
  export interface CollectionCustom {
       'plugin-import-export'?: {
           // plugin-specific collection props...
       }
  }
}

Link to the code that reproduces this issue

https://github.com/payloadcms/payload

Which area(s) are affected? (Select all that apply)

area: core

Environment Info

Binaries:
  Node: 24.3.0
  npm: 11.4.2
  Yarn: N/A
  pnpm: 10.12.4
Relevant Packages:
  payload: 3.64.0
  next: 15.5.6
  @payloadcms/db-mongodb: 3.64.0
  @payloadcms/db-sqlite: 3.64.0
  @payloadcms/drizzle: 3.64.0
  @payloadcms/graphql: 3.64.0
  @payloadcms/next/utilities: 3.64.0
  @payloadcms/plugin-multi-tenant: 3.64.0
  @payloadcms/translations: 3.64.0
  @payloadcms/ui/shared: 3.64.0
  react: 19.2.0
  react-dom: 19.2.0
Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:40 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6041
  Available memory (MB): 24576
  Available CPU cores: 14

[github-actions]

🚀 This is included in version v3.65.0