diff --git a/frontend/src/components/concept/ConceptResultMap.tsx b/frontend/src/components/concept/ConceptResultMap.tsx
index 0d50990e..e4563827 100644
--- a/frontend/src/components/concept/ConceptResultMap.tsx
+++ b/frontend/src/components/concept/ConceptResultMap.tsx
@@ -97,15 +97,17 @@ export function ConceptResultMap({
           url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
         />
 
-        {/* Parcel boundary — outline only so buildings read on top. */}
+        {/* Parcel boundary — accent-soft fill + accent outline (#2179) so the
+            lot reads at a glance; buildings (opacity 0.55) still read on top of
+            the lighter 0.35 parcel fill. Colours mirror --accent / --accent-soft. */}
         <GeoJSON
           key={`parcel-${variantKey}`}
           data={parcel}
           style={{
-            color: "#D1D5DB",
+            color: "#1D4ED8", // --accent
             weight: 2,
-            dashArray: "6 4",
-            fillOpacity: 0,
+            fillColor: "#DBEAFE", // --accent-soft
+            fillOpacity: 0.35,
           }}
         />
 
diff --git a/frontend/src/components/concept/Massing3DScene.tsx b/frontend/src/components/concept/Massing3DScene.tsx
index 48bcea65..21596f31 100644
--- a/frontend/src/components/concept/Massing3DScene.tsx
+++ b/frontend/src/components/concept/Massing3DScene.tsx
@@ -50,7 +50,8 @@ const FALLBACK_FLOORS = 12;
 const COLOR_BG = 0xf6f7f9; // --bg-app
 const COLOR_SLATE = 0x33424f; // building body
 const COLOR_ACCENT = 0x1d4ed8; // --accent (edge lines)
-const COLOR_OUTLINE = 0xd1d5db; // --border-strong (parcel outline)
+const COLOR_PARCEL_OUTLINE = 0x1d4ed8; // --accent (parcel outline — accent, #2179)
+const COLOR_PARCEL_FILL = 0xdbeafe; // --accent-soft (parcel fill — #2179)
 const COLOR_GROUND_FALLBACK = 0xfafbfc; // --bg-card-alt
 const COLOR_GRID = 0xe6e8ec; // --border-card
 
@@ -165,8 +166,11 @@ function buildModel(
     floorHeightM,
   );
 
+  // Pad the ground tile generously (0.7 = +70% context each side, #2179) so the
+  // OSM substrate extends well beyond the parcel; the 4×4 tile cap below keeps it
+  // sharp at the same zoom.
   const rawBounds = ringBounds(parcelRingWgs);
-  const groundBounds = rawBounds ? padBounds(rawBounds, 0.3) : null;
+  const groundBounds = rawBounds ? padBounds(rawBounds, 0.7) : null;
 
   return {
     buildings,
@@ -271,18 +275,61 @@ function buildBuildingsGroup(model: MassingModel): THREE.Group {
   return group;
 }
 
-/** Parcel outline as a LineLoop at y=0.05 in world space. */
-function buildParcelOutline(model: MassingModel): THREE.Line {
-  const pts: number[] = [];
-  for (const p of model.parcelRing) {
-    pts.push(p.x, 0.05, p.z);
+/**
+ * Parcel highlight (#2179): a translucent accent-soft FILL just above the ground
+ * plane plus a prominent accent OUTLINE. Returns a Group so the caller adds one
+ * object. WebGL ignores LineBasicMaterial.linewidth, so the outline is doubled at
+ * two heights (y=0.05, y=0.10) to read thick from any camera angle without a new
+ * dependency.
+ */
+function buildParcelHighlight(model: MassingModel): THREE.Group {
+  const group = new THREE.Group();
+  group.name = "parcel";
+
+  // Fill: THREE.Shape from the parcel ring → ShapeGeometry, laid into the ground
+  // plane (rotate −π/2 about X so the XY shape sits on the XZ world plane) and
+  // lifted to y≈0.03 (above the ground substrate at y=−0.02, under the outline).
+  if (model.parcelRing.length >= 3) {
+    const shape = new THREE.Shape();
+    shape.moveTo(model.parcelRing[0].x, model.parcelRing[0].z);
+    for (let i = 1; i < model.parcelRing.length; i++) {
+      shape.lineTo(model.parcelRing[i].x, model.parcelRing[i].z);
+    }
+    shape.closePath();
+    const fillGeo = new THREE.ShapeGeometry(shape);
+    const fill = new THREE.Mesh(
+      fillGeo,
+      new THREE.MeshBasicMaterial({
+        color: COLOR_PARCEL_FILL, // --accent-soft
+        transparent: true,
+        opacity: 0.35,
+        depthWrite: false,
+        side: THREE.DoubleSide,
+      }),
+    );
+    // Shape is built in XY; rotate to lie in the ground (XZ) plane. After the
+    // −π/2 X-rotation shape.y (= parcel z) maps to +z, so no mirroring.
+    fill.rotation.x = -Math.PI / 2;
+    fill.position.y = 0.03;
+    group.add(fill);
   }
-  const geo = new THREE.BufferGeometry();
-  geo.setAttribute("position", new THREE.Float32BufferAttribute(pts, 3));
-  return new THREE.Line(
-    geo,
-    new THREE.LineBasicMaterial({ color: COLOR_OUTLINE }),
-  );
+
+  // Outline: accent LineLoop, doubled at y=0.05 and y=0.10 (linewidth is a no-op
+  // in WebGL) so the parcel edge reads prominently.
+  const outlineMat = new THREE.LineBasicMaterial({
+    color: COLOR_PARCEL_OUTLINE,
+  });
+  for (const y of [0.05, 0.1]) {
+    const pts: number[] = [];
+    for (const p of model.parcelRing) {
+      pts.push(p.x, y, p.z);
+    }
+    const geo = new THREE.BufferGeometry();
+    geo.setAttribute("position", new THREE.Float32BufferAttribute(pts, 3));
+    group.add(new THREE.LineLoop(geo, outlineMat));
+  }
+
+  return group;
 }
 
 // ── OSM ground tile (fetch + stitch + CanvasTexture) ──────────────────────────
@@ -317,7 +364,9 @@ async function loadGroundTexture(
   signal: { cancelled: boolean },
 ): Promise<GroundTexResult | null> {
   if (!model.groundBounds) return null;
-  const range = osmTileRangeForBbox(model.groundBounds);
+  // Allow up to a 4×4 (16-tile) block (#2179): a larger extent WITHOUT dropping
+  // zoom, so the substrate stays sharp while covering more surroundings.
+  const range = osmTileRangeForBbox(model.groundBounds, { maxTiles: 16 });
 
   const canvas = document.createElement("canvas");
   canvas.width = 256 * range.cols;
@@ -503,9 +552,9 @@ export default function Massing3DScene({
     gridMat.transparent = true;
     scene.add(grid);
 
-    // parcel outline
-    const outline = buildParcelOutline(model);
-    scene.add(outline);
+    // parcel highlight (accent-soft fill + accent outline, #2179)
+    const parcel = buildParcelHighlight(model);
+    scene.add(parcel);
 
     // buildings
     const buildings = buildBuildingsGroup(model);
diff --git a/frontend/src/components/site-finder/analysis/Section7Concept.tsx b/frontend/src/components/site-finder/analysis/Section7Concept.tsx
index c2993e5d..7824c007 100644
--- a/frontend/src/components/site-finder/analysis/Section7Concept.tsx
+++ b/frontend/src/components/site-finder/analysis/Section7Concept.tsx
@@ -23,9 +23,10 @@
  *   • land_cost_rub   ← egrn.cadastral_value_rub
  * Falls back to comfort / mid_rise when those are null.
  *
- * The section defaults to collapsed (above-the-fold rule). On first expand it
- * auto-runs once with the default program (count = 3) so the user lands on a
- * result, not an empty form.
+ * The section is OPEN by default (Anton feedback 2026-07-02, issue #2179): the
+ * concept is the report's key deliverable. It auto-runs once on mount with the
+ * default program (count = 3) so the user lands on a result, not an empty form.
+ * The <details> can still be collapsed via its summary.
  *
  * СЗЗ / financial_estimate === null is NOT a dead end: /concepts only needs a
  * polygon + form inputs (independent of the financial_estimate regulatory gate),
@@ -205,7 +206,11 @@ export function Section7Concept({ analysis }: Props) {
   // when it becomes ready (still only once, still only after first open). The
   // <details onToggle> flips `expanded`, which (re)triggers the effect.
   const autoRanRef = useRef(false);
-  const [expanded, setExpanded] = useState(false);
+  // §7 «Концепция» is OPEN by default (Anton feedback 2026-07-02, issue #2179):
+  // the concept is the report's key deliverable, so the auto-run fires on mount
+  // instead of waiting for a first expand. The user can still collapse the
+  // <details> via the summary; onToggle keeps `expanded` in sync when reopened.
+  const [expanded, setExpanded] = useState(true);
 
   useEffect(() => {
     if (autoRanRef.current || !expanded) return;
@@ -242,9 +247,10 @@ export function Section7Concept({ analysis }: Props) {
         subtitle="Единая программа застройки: задайте число корпусов, этажность и класс — движок разложит ровно эту программу и посчитает ТЭП и финмодель по геометрии участка."
       />
 
-      {/* Collapsed by default (above-the-fold rule). Auto-runs once on first
-          expand so the user lands on a result, not an empty form. */}
-      <details style={{ marginTop: 12 }} onToggle={handleToggle}>
+      {/* Open by default (Anton feedback 2026-07-02, issue #2179): концепция —
+          ключевой deliverable отчёта, поэтому §7 раскрыт и авторасчёт стартует
+          сразу на маунте. Пользователь может свернуть блок через summary. */}
+      <details open style={{ marginTop: 12 }} onToggle={handleToggle}>
         <summary
           style={{
             cursor: "pointer",
diff --git a/frontend/src/lib/__tests__/geo-local.test.ts b/frontend/src/lib/__tests__/geo-local.test.ts
index 39a20171..2e61d688 100644
--- a/frontend/src/lib/__tests__/geo-local.test.ts
+++ b/frontend/src/lib/__tests__/geo-local.test.ts
@@ -135,4 +135,24 @@ describe("osmTileRangeForBbox", () => {
     expect(r.northLat).toBeGreaterThanOrEqual(bbox.maxLat);
     expect(r.southLat).toBeLessThanOrEqual(bbox.minLat);
   });
+
+  it("honours a 4×4 (16-tile) cap and holds a higher zoom than the 2×2 cap (#2179)", () => {
+    // A wider ~700 m-padded bbox around EKB centre (mirrors padBounds(_, 0.7)).
+    const bbox = {
+      minLon: LON0 - 0.006,
+      maxLon: LON0 + 0.006,
+      minLat: LAT0 - 0.004,
+      maxLat: LAT0 + 0.004,
+    };
+    const r16 = osmTileRangeForBbox(bbox, { maxTiles: 16 });
+    const r4 = osmTileRangeForBbox(bbox, { maxTiles: 4 });
+    expect(r16.cols * r16.rows).toBeLessThanOrEqual(16);
+    // A larger tile budget keeps a zoom ≥ the 2×2 cap (never sharper-losing).
+    expect(r16.z).toBeGreaterThanOrEqual(r4.z);
+    // The stitched block must still fully contain the bbox.
+    expect(r16.westLon).toBeLessThanOrEqual(bbox.minLon);
+    expect(r16.eastLon).toBeGreaterThanOrEqual(bbox.maxLon);
+    expect(r16.northLat).toBeGreaterThanOrEqual(bbox.maxLat);
+    expect(r16.southLat).toBeLessThanOrEqual(bbox.minLat);
+  });
 });
diff --git a/frontend/src/lib/geo-local.ts b/frontend/src/lib/geo-local.ts
index bb83b781..6ba06e61 100644
--- a/frontend/src/lib/geo-local.ts
+++ b/frontend/src/lib/geo-local.ts
@@ -130,9 +130,10 @@ export interface TileRange {
 }
 
 /**
- * Pick the OSM zoom for a bbox such that the stitched tile block stays ≤ maxTiles
- * (default 4 → a 2×2 cap), clamped to [minZ, maxZ]. Starts at maxZ and steps the
- * zoom down until the tile count fits.
+ * Pick the OSM zoom for a bbox such that the stitched tile block stays ≤ maxTiles,
+ * clamped to [minZ, maxZ]. Starts at maxZ and steps the zoom down until the tile
+ * count fits. `maxTiles` defaults to 4 (a 2×2 cap); the massing scene passes 16
+ * (a 4×4 cap, #2179) so a larger surrounding extent renders WITHOUT dropping zoom.
  *
  * Returns the integer tile range plus the EXACT WGS84 corners of the stitched
  * block (tile2lon/lat of the inclusive range), which the scene projects with the