Rule

Long-running operations must show real progress, not fake animation.

Why

A progress bar that freezes at 80% loses user trust faster than showing no progress at all.

Must

• Use a determinate progress bar when completion percentage is known.
• Use an indeterminate spinner only when duration is truly unknown.
• Show an estimated time remaining if the operation exceeds 5 seconds.
• Provide a cancel action for operations that take more than 10 seconds.
• Surface a clear success or failure state at completion.

Should

• Break large jobs into stages and name each stage.
• Persist progress state so a page refresh does not restart long jobs.

Anti-patterns

• Fake progress animation that does not reflect server state.
• No cancel option for unbounded operations.
• Silent failure that looks identical to success.

Test Cases

• Cancelled job surfaces clean cancellation feedback.
• Failed job distinguishes itself from success visually.

Telemetry

• long_operation_started
• long_operation_cancelled
• long_operation_completed
• long_operation_failed