Field note · 19 March 2026
Lead-time buffers that do not hide waste
Extra days feel like prudence until the terminal invoice arrives. Label them, or they will be celebrated as skill.
The Inventory Signal Workshop exists because planners are often punished for stockouts and quietly rewarded for bloated yards. A buffer that is never named as a buffer becomes “on-time performance.” In Pingtung we watched a frozen-food exporter treat two extra days of reefer dwell as a quality hold. The temperature need was real for part of the dwell. The rest was habit: gate-in early so nobody would miss a string.
Our marking rule is dull on purpose. Write the scientific or contractual reason on the same line as the days. If the reason is “we are afraid of the planner two buildings over,” that is still a reason—just not a quality reason. Finance can then price the fear.
Safety stock on a component should show the service level assumption. If nobody can name the service level, the stock is a rumor with a bin location. The lab does not install forecasting software. We make the rumor visible.
Typhoon season is the exception people cite to keep every extra day. Fair. Then isolate a typhoon overlay as a dated policy, not a year-round fog. When the season ends, the overlay should have an expiry, the way a berth window does.