diff --git a/ui/src/views/Forecast.jsx b/ui/src/views/Forecast.jsx
index 901a60a..d0f2d9b 100644
--- a/ui/src/views/Forecast.jsx
+++ b/ui/src/views/Forecast.jsx
@@ -942,6 +942,11 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
   // data that only the cell metadata knows. The listener runs on every draw, so
   // it survives scrolling and virtualisation -- a stylesheet cannot, since the
   // DOM cells are recycled across columns as you scroll.
+  // Blank for this purpose means "no value at this level", which Perspective
+  // writes as a zero-width space rather than an empty string.
+  const notBlank = (v) =>
+    v != null && String(v).replace(/[\s\u200b-\u200d\ufeff]/g, '') !== ''
+
   function applyGroupRules() {
     const grid = gridRef.current
     const table = grid?.regular_table
@@ -967,6 +972,11 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
       const body = table.querySelectorAll('tbody td')
       // The deepest column path is a leaf; anything shorter is an aggregate of
       // the levels below it, which is what makes a subtotal a subtotal.
+      //
+      // The empty levels are not empty strings. Perspective pads a subtotal's
+      // path with zero-width spaces -- ['04 - Forecast', '\u200b', 'sales_usd']
+      // -- so every path is the same length and a naive `!== ''` test finds no
+      // subtotals at all.
       let depth = 0
       const metas = []
       for (const td of body) {
@@ -974,7 +984,7 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
         try { meta = table.getMeta(td) } catch { meta = null }
         metas.push([td, meta])
         const path = meta?.column_header
-        if (Array.isArray(path)) depth = Math.max(depth, path.filter(v => v != null && v !== '').length)
+        if (Array.isArray(path)) depth = Math.max(depth, path.filter(notBlank).length)
       }
 
       let prevGroup = null
@@ -982,7 +992,7 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
         td.classList.remove('pf-group-start', 'pf-subtotal')
         const path = meta?.column_header
         if (!Array.isArray(path) || !path.length) { prevGroup = null; continue }
-        const named = path.filter(v => v != null && v !== '')
+        const named = path.filter(notBlank)
         const group = named[0]
         if (group !== prevGroup) { td.classList.add('pf-group-start'); prevGroup = group }
         if (named.length < depth) td.classList.add('pf-subtotal')