diff --git a/internal/check-poster-browser-equiv.mjs b/internal/check-poster-browser-equiv.mjs
index 4bfd5dff4..2b8d8688f 100644
--- a/internal/check-poster-browser-equiv.mjs
+++ b/internal/check-poster-browser-equiv.mjs
@@ -121,7 +121,13 @@ const results = []
   const series = { totalGroups: tier.reduce((a, x) => a + (x.count || 0), 0), totalLists: tier.length, index: tier.indexOf(c) + 1 }
   results.push({ what: `${c.id} (3x3 poster, generateCountrySheet)`,
     browser: await generateCountrySheet({ country: c, records: recs, assetsBase, ISO3_NAME, format: '3x3', series, date: DATE }),
-    node: nodeSheet({ COUNTRIES: '1', FORMAT: '3x3', SHEET: '3x3', ONLY: c.id }, `${c.id}.html`) })
+    // SPARSE on the Node side because a POSTER is generated with SPARSE=1 -- that is how the `posters`
+    // script builds every stored thumbnail, and how the browser now draws a poster at the click. This
+    // gate used to compare the dense layout with the dense layout, so it passed while every stored
+    // thumbnail showed the SPARSE header and every print showed the dense one: a check that agreed
+    // with itself and with nothing a reader saw. The packet case above stays dense on both sides,
+    // because packet pages are built without SPARSE.
+    node: nodeSheet({ COUNTRIES: '1', FORMAT: '3x3', SHEET: '3x3', SPARSE: '1', ONLY: c.id }, `${c.id}.html`) })
 }
 
 for (const r of results) {
diff --git a/library/packet/posterSheets.js b/library/packet/posterSheets.js
index a56c99667..44c22b30e 100644
--- a/library/packet/posterSheets.js
+++ b/library/packet/posterSheets.js
@@ -130,7 +130,15 @@ export async function generateSheet({
   // pinned the FIRST caller's data — its boundaries, its name table — onto every later sheet: a caller
   // without adm0 poisoned the cache for one with it. The inputs are the caller's, every time.
   const gen = createPosterGenerator({
-    env: { FORMAT: format, ...(date ? { POSTER_DATE: date } : {}) },
+    // ★ SPARSE FOR POSTERS, NEVER FOR THE PACKET -- exactly the split the two build scripts make.
+    // `posters` generates with SPARSE=1 (the "thumbnail-worthy" layout: the bold facts row with the
+    // UPG count and population set large, a bigger map, and the two vision columns dropped), and
+    // `packets` does not. This env used to carry FORMAT and POSTER_DATE only, so EVERY sheet drawn
+    // at the click -- UPG-100 and country alike -- fell back to the small facts table, while the
+    // stored UPG-100 thumbnails showed the bold row. A reader saw one header on the card and got
+    // another on the print. 'packet' is the one packet format (FORMATS: 3x4, 3x3, letter, packet),
+    // so it alone keeps the full layout its packet pages were designed around.
+    env: { FORMAT: format, ...(format !== 'packet' ? { SPARSE: '1' } : {}), ...(date ? { POSTER_DATE: date } : {}) },
     SERIES_DEF, ISO3_NAME, adm0, adm1Ind, adm1Chn, nePlaces: places, series: { totalGroups: 0, totalLists: 0, index: 1, ...series },
   })
   const fc = zoneFC || { type: 'FeatureCollection', features: [] }