diff --git a/docs/requirements.md b/docs/requirements.md
index 9a06987..44b5224 100644
--- a/docs/requirements.md
+++ b/docs/requirements.md
@@ -198,6 +198,7 @@ The screen is divided into three vertical sections:
 
 - REQ-UI-EMPTY-SELECTION: When no building is selected, the panel is empty.
 - REQ-UI-SINGLE-SELECTION: When one building is selected, the panel shows: building name, current recipe or blueprint selection, input buffer contents, and output buffer contents. Buffer counts are displayed as `a/b` where `a` is the current item count and `b` is the per-cycle amount (items consumed per run for inputs; items produced per run for outputs).
+- REQ-UI-PRODUCTION-PROGRESS: For buildings that produce items or ships (miner, smelter, assembler, reprocessing plant, shipyard), the selected building panel also shows: (a) the cycle time of the currently selected recipe or blueprint in seconds, and (b) the completion percentage of the active production cycle as an integer (e.g. `42%`), or the text `idle` when no production cycle is active. When no recipe or blueprint is selected, neither the cycle time nor the progress indicator is shown.
 - REQ-UI-MULTI-SELECT: The player selects multiple buildings by box-drag or by Ctrl+clicking individual buildings to add or remove them from the selection.
 - REQ-UI-MULTI-SELECTION: When multiple buildings are selected, the panel shows how many of each building type are selected. No per-building detail is shown.
 - REQ-UI-CONFIG-INLINE: Recipe, blueprint, ship stance, and target priority configuration for a selected building is shown and changed inline within this panel.