Where the client field holds a plain-text name, clientId holds a machine-friendly identifier for the same party — for example a key from a CRM or a shared client directory. Storing it on the Project lets Relic tie this archaeological project to the client's record elsewhere, so the two systems can be cross-referenced or kept in sync. It is optional and independent of the text client name: you might record just the readable name, just the identifier, or both. Because it is a reference value rather than a label, it does not affect catalog numbering, uniqueness, or how the Project is displayed.
Technical section
Data model, API, and internals — visible to developers.