diff --git a/docker-dev/Dockerfile b/docker-dev/Dockerfile
index 15ec7781..e7c06897 100644
--- a/docker-dev/Dockerfile
+++ b/docker-dev/Dockerfile
@@ -3,7 +3,12 @@
 # Compose drives OTOPCUA_ROLES + Cluster:* env per container to differentiate them.
 # A separate `migrator` stage (below) applies EF migrations once on bring-up.
 
-FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+# Build stage is PINNED to linux/amd64. Per-cluster mesh Phase 3 added an in-repo .proto compiled by
+# Grpc.Tools, whose bundled linux_arm64 `protoc` segfaults (exit 139) on Apple-Silicon Docker — so a
+# native-arm64 build stage cannot generate the gRPC stubs. `dotnet publish` here is framework-dependent
+# (portable IL + every RID's native assets), so the amd64-built output runs unchanged on the native
+# runtime image below; only this one-time build is emulated, runtime stays native/fast.
+FROM --platform=linux/amd64 mcr.microsoft.com/dotnet/sdk:10.0 AS build
 WORKDIR /src
 COPY . .
 RUN dotnet restore ZB.MOM.WW.OtOpcUa.slnx