diff --git a/Package.swift b/Package.swift
index dae3352..e0a3ef9 100644
--- a/Package.swift
+++ b/Package.swift
@@ -15,10 +15,13 @@ import Foundation
 // Prefer a local sibling checkout (../<name>) when present, else the published URL — so the whole
 // OCCT ecosystem SHARES the single OCCTSwift/Libraries/OCCT.xcframework instead of each repo
 // extracting its own 1.3 GB copy. CI / fresh clones (no sibling) use the URL pin. `#filePath`-relative
-// so it's independent of build CWD.
+// so it's independent of build CWD. Guarded against SwiftPM's own checkout layout: a transitively-
+// resolved checkout under a consumer's .build/ must never be treated as a local dev sibling
+// (ecosystem issue OCCTSwiftScripts#69 / #70).
 func occtDep(_ name: String, from version: String) -> Package.Dependency {
     let manifestDir = URL(fileURLWithPath: #filePath).deletingLastPathComponent().path
-    if FileManager.default.fileExists(atPath: manifestDir + "/../\(name)/Package.swift") {
+    if !manifestDir.contains("/.build/"),
+       FileManager.default.fileExists(atPath: manifestDir + "/../\(name)/Package.swift") {
         return .package(path: "../\(name)")
     }
     return .package(url: "https://github.com/SecondMouseAU/\(name).git", from: Version(version)!)
@@ -27,9 +30,11 @@ func occtDep(_ name: String, from version: String) -> Package.Dependency {
 // As occtDep, but pins to the package's minor line (`.upToNextMinor`) instead of
 // the major. Used to cap a transitive dependency whose newer minors pull deps we
 // don't want in the graph — see the OCCTSwiftIO note in `dependencies` below.
+// Same checkout-layout guard as occtDep (ecosystem issue OCCTSwiftScripts#69 / #70).
 func occtDepUpToNextMinor(_ name: String, from version: String) -> Package.Dependency {
     let manifestDir = URL(fileURLWithPath: #filePath).deletingLastPathComponent().path
-    if FileManager.default.fileExists(atPath: manifestDir + "/../\(name)/Package.swift") {
+    if !manifestDir.contains("/.build/"),
+       FileManager.default.fileExists(atPath: manifestDir + "/../\(name)/Package.swift") {
         return .package(path: "../\(name)")
     }
     return .package(url: "https://github.com/SecondMouseAU/\(name).git", .upToNextMinor(from: Version(version)!))
diff --git a/Sources/OCCTMCPCore/Tools/HeatmapTools.swift b/Sources/OCCTMCPCore/Tools/HeatmapTools.swift
index 9fcaa81..ae3024c 100644
--- a/Sources/OCCTMCPCore/Tools/HeatmapTools.swift
+++ b/Sources/OCCTMCPCore/Tools/HeatmapTools.swift
@@ -135,9 +135,19 @@ public enum HeatmapTools {
                 let base = UInt32(indices.count)
                 indices.append(base); indices.append(base + 1); indices.append(base + 2)
             }
-            bodies.append(ViewportBody.directMesh(
+            // ViewportBody.directMesh (positions/normals as separate arrays) no longer exists —
+            // ViewportBody's init takes a single interleaved vertexData ([px,py,pz,nx,ny,nz,...],
+            // stride 6), so zip the two flat per-vertex arrays together here (same idiom the
+            // OCCTSwiftViewport primitive factories, e.g. .box, use internally).
+            var vertexData: [Float] = []
+            vertexData.reserveCapacity(positions.count * 2)
+            for i in stride(from: 0, to: positions.count, by: 3) {
+                vertexData.append(positions[i]); vertexData.append(positions[i + 1]); vertexData.append(positions[i + 2])
+                vertexData.append(bnormals[i]); vertexData.append(bnormals[i + 1]); vertexData.append(bnormals[i + 2])
+            }
+            bodies.append(ViewportBody(
                 id: "\(fromBodyId)#band\(b)",
-                positions: positions, normals: bnormals, indices: indices, color: color
+                vertexData: vertexData, indices: indices, edges: [], color: color
             ))
         }
         guard !bodies.isEmpty else { return .init("No coloured surface produced.", isError: true) }