Lock enforcement must be server-authoritative
Frontend checks are useful for UX, but they are not security controls. If the lock decision is made in the client, motivated users can bypass it.
Read and write paths must both enforce project lock state on the server and return stable, explicit errors.
Map behavior into predictable SDK errors
Lock state only helps operations when error behavior is predictable. SDK consumers should receive consistent codes they can map to clear UI states.
Ambiguous failures create support confusion during already tense invoice scenarios.
Include incident logging in the control design
Track lock toggles, denied operations, and unlock actions with backend event logging. This gives you evidence for review and helps identify abuse patterns.
Without this data, incidents become guesswork and policy decisions are harder to defend.
Define operating policy, not just implementation
A kill switch is a business control with legal and relationship implications. Teams should define who can trigger lock state, under what conditions, and how resolution is handled.
Technical safeguards work best when backed by clear contractual language and an escalation process.
Implementation takeaway
Treat lock controls as part security architecture, part operations design. Server-authoritative checks plus clear policy gives you protection without chaos.