diff --git a/ui/src/views/Forecast.jsx b/ui/src/views/Forecast.jsx
index 7caa0c5..d59b030 100644
--- a/ui/src/views/Forecast.jsx
+++ b/ui/src/views/Forecast.jsx
@@ -1007,7 +1007,23 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
   // survives adding measures or rearranging the pivot, unlike hiding by position.
   // The rule has to live inside the plugin's shadow root; a document stylesheet
   // cannot reach it.
-  const HIDE_SPLIT_TOTAL_CSS = `
+  const GRID_CSS = `
+    /* Let headers and row labels size their own column.
+     *
+     * Auto-fit measures cells with getBoundingClientRect() and sets each column's
+     * min-width from the result — but the datagrid's own CSS wraps and clips
+     * header text, so a clipped th measures at the width it was *allotted*, not
+     * the width of its content. The column can therefore never grow to fit its
+     * own heading, which is why the values fit and the headings did not. Row
+     * labels are th elements in tbody and clip for the same reason.
+     *
+     * nowrap alone: no width or overflow is touched, so the measurement sees the
+     * full text and the existing sizing logic does the rest. */
+    thead th,
+    tbody th {
+      white-space: nowrap !important;
+    }
+
     th.psp-split-total:not(.psp-split-subtotal),
     td.psp-split-total:not(.psp-split-subtotal) {
       visibility: hidden !important;
@@ -1045,10 +1061,10 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
     // Retried from the config-update handler, and once on a short delay.
     if (!grid) return false
     const root = grid.getRootNode()
-    if (!root || root.querySelector?.('#pf-hide-split-total')) return true
+    if (!root || root.querySelector?.('#pf-grid-css')) return true
     const style = document.createElement('style')
-    style.id = 'pf-hide-split-total'
-    style.textContent = HIDE_SPLIT_TOTAL_CSS
+    style.id = 'pf-grid-css'
+    style.textContent = GRID_CSS
     ;(root.appendChild ? root : document.head).appendChild(style)
     return true
   }