diff --git a/ZB.MOM.WW.LocalDb/Directory.Build.props b/ZB.MOM.WW.LocalDb/Directory.Build.props
new file mode 100644
index 0000000..98cc6fa
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/Directory.Build.props
@@ -0,0 +1,24 @@
+<Project>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <LangVersion>latest</LangVersion>
+    <Version>0.1.0</Version>
+    <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <!-- NU1510 (package-pruning advice): the Replication and Tests projects carry a
+         Microsoft.AspNetCore.App FrameworkReference AND explicit PackageReferences to
+         in-framework packages (Hosting/Logging/DI/Configuration), as required by the
+         library layout. The advice is benign; keep the explicit refs and silence it. -->
+    <NoWarn>$(NoWarn);NU1510</NoWarn>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
+  </PropertyGroup>
+
+  <!-- Embed the repo README in each packable nupkg (ignored by non-packable projects). -->
+  <ItemGroup Condition="'$(IsPackable)' == 'true'">
+    <None Include="$(MSBuildThisFileDirectory)README.md" Pack="true" PackagePath="\" Visible="false" />
+  </ItemGroup>
+
+</Project>
diff --git a/ZB.MOM.WW.LocalDb/Directory.Packages.props b/ZB.MOM.WW.LocalDb/Directory.Packages.props
new file mode 100644
index 0000000..fa64b47
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/Directory.Packages.props
@@ -0,0 +1,32 @@
+<Project>
+  <PropertyGroup>
+    <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
+    <!-- Enable transitive pinning so the security override below (SQLitePCLRaw native lib) takes effect. -->
+    <CentralPackageTransitivePinningEnabled>true</CentralPackageTransitivePinningEnabled>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageVersion Include="Microsoft.Data.Sqlite" Version="10.0.7" />
+    <!-- Transitive security pin: Microsoft.Data.Sqlite 10.0.7 pulls SQLitePCLRaw.lib.e_sqlite3 2.1.11,
+         which carries advisory GHSA-2m69-gcr7-jv3q (NU1903). Pin the patched 2.1.12 native lib. -->
+    <PackageVersion Include="SQLitePCLRaw.lib.e_sqlite3" Version="2.1.12" />
+    <PackageVersion Include="Microsoft.Extensions.Options" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.Configuration" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.Configuration.Abstractions" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.Hosting.Abstractions" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.Hosting" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.7" />
+    <PackageVersion Include="Google.Protobuf" Version="3.34.1" />
+    <PackageVersion Include="Grpc.Core.Api" Version="2.76.0" />
+    <PackageVersion Include="Grpc.Tools" Version="2.76.0" />
+    <PackageVersion Include="Grpc.AspNetCore" Version="2.76.0" />
+    <PackageVersion Include="Grpc.Net.Client" Version="2.76.0" />
+    <PackageVersion Include="Microsoft.AspNetCore.TestHost" Version="10.0.7" />
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageVersion Include="xunit" Version="2.9.3" />
+    <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.4" />
+    <PackageVersion Include="coverlet.collector" Version="6.0.4" />
+  </ItemGroup>
+</Project>
diff --git a/ZB.MOM.WW.LocalDb/README.md b/ZB.MOM.WW.LocalDb/README.md
new file mode 100644
index 0000000..6e847ab
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/README.md
@@ -0,0 +1,8 @@
+# ZB.MOM.WW.LocalDb
+
+An embedded SQLite local cache with optional bidirectional async 2-node replication
+over gRPC, for the ZB.MOM.WW SCADA / OT family. It gives an application a fast,
+crash-safe local store that can optionally keep a second node in sync asynchronously,
+without requiring a central database on the hot path.
+
+See the design doc: [`docs/plans/2026-07-17-localdb-design.md`](../docs/plans/2026-07-17-localdb-design.md).
diff --git a/ZB.MOM.WW.LocalDb/ZB.MOM.WW.LocalDb.slnx b/ZB.MOM.WW.LocalDb/ZB.MOM.WW.LocalDb.slnx
new file mode 100644
index 0000000..eccb24c
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/ZB.MOM.WW.LocalDb.slnx
@@ -0,0 +1,10 @@
+<Solution>
+  <Folder Name="/src/">
+    <Project Path="src/ZB.MOM.WW.LocalDb/ZB.MOM.WW.LocalDb.csproj" />
+    <Project Path="src/ZB.MOM.WW.LocalDb.Contracts/ZB.MOM.WW.LocalDb.Contracts.csproj" />
+    <Project Path="src/ZB.MOM.WW.LocalDb.Replication/ZB.MOM.WW.LocalDb.Replication.csproj" />
+  </Folder>
+  <Folder Name="/tests/">
+    <Project Path="tests/ZB.MOM.WW.LocalDb.Tests/ZB.MOM.WW.LocalDb.Tests.csproj" />
+  </Folder>
+</Solution>
diff --git a/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Contracts/Protos/localdb_sync.proto b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Contracts/Protos/localdb_sync.proto
new file mode 100644
index 0000000..562e030
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Contracts/Protos/localdb_sync.proto
@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+package localdb_sync.v1;
+
+option csharp_namespace = "ZB.MOM.WW.LocalDb.Contracts";
+
+// Placeholder service. The real replication contract is defined in a later task.
+service LocalDbSync {
+}
diff --git a/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Contracts/ZB.MOM.WW.LocalDb.Contracts.csproj b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Contracts/ZB.MOM.WW.LocalDb.Contracts.csproj
new file mode 100644
index 0000000..bd1da0b
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Contracts/ZB.MOM.WW.LocalDb.Contracts.csproj
@@ -0,0 +1,31 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <IsPackable>true</IsPackable>
+    <PackageId>ZB.MOM.WW.LocalDb.Contracts</PackageId>
+    <Authors>ZB.MOM.WW</Authors>
+    <Description>localdb_sync.v1 gRPC wire contract for ZB.MOM.WW.LocalDb replication.</Description>
+    <PackageProjectUrl>https://gitea.dohertylan.com/dohertj2/zb-mom-ww-localdb</PackageProjectUrl>
+    <RepositoryUrl>https://gitea.dohertylan.com/dohertj2/zb-mom-ww-localdb</RepositoryUrl>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Protobuf Include="Protos\*.proto" GrpcServices="Both" ProtoRoot="Protos" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Google.Protobuf" />
+    <PackageReference Include="Grpc.Core.Api" />
+    <PackageReference Include="Grpc.Tools">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+</Project>
diff --git a/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Replication/ZB.MOM.WW.LocalDb.Replication.csproj b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Replication/ZB.MOM.WW.LocalDb.Replication.csproj
new file mode 100644
index 0000000..f074e9e
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Replication/ZB.MOM.WW.LocalDb.Replication.csproj
@@ -0,0 +1,38 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <IsPackable>true</IsPackable>
+    <PackageId>ZB.MOM.WW.LocalDb.Replication</PackageId>
+    <Authors>ZB.MOM.WW</Authors>
+    <Description>Bidirectional async 2-node gRPC sync engine for ZB.MOM.WW.LocalDb.</Description>
+    <PackageProjectUrl>https://gitea.dohertylan.com/dohertj2/zb-mom-ww-localdb</PackageProjectUrl>
+    <RepositoryUrl>https://gitea.dohertylan.com/dohertj2/zb-mom-ww-localdb</RepositoryUrl>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\ZB.MOM.WW.LocalDb\ZB.MOM.WW.LocalDb.csproj" />
+    <ProjectReference Include="..\ZB.MOM.WW.LocalDb.Contracts\ZB.MOM.WW.LocalDb.Contracts.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Grpc.AspNetCore" />
+    <PackageReference Include="Grpc.Net.Client" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="ZB.MOM.WW.LocalDb.Tests" />
+  </ItemGroup>
+
+</Project>
diff --git a/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb/ZB.MOM.WW.LocalDb.csproj b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb/ZB.MOM.WW.LocalDb.csproj
new file mode 100644
index 0000000..a16d144
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb/ZB.MOM.WW.LocalDb.csproj
@@ -0,0 +1,32 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <IsPackable>true</IsPackable>
+    <PackageId>ZB.MOM.WW.LocalDb</PackageId>
+    <Authors>ZB.MOM.WW</Authors>
+    <Description>Embedded SQLite local cache with optional bidirectional async 2-node gRPC replication for the ZB.MOM.WW SCADA family.</Description>
+    <PackageProjectUrl>https://gitea.dohertylan.com/dohertj2/zb-mom-ww-localdb</PackageProjectUrl>
+    <RepositoryUrl>https://gitea.dohertylan.com/dohertj2/zb-mom-ww-localdb</RepositoryUrl>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Data.Sqlite" />
+    <PackageReference Include="Microsoft.Extensions.Options" />
+    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="ZB.MOM.WW.LocalDb.Tests" />
+  </ItemGroup>
+
+</Project>
diff --git a/ZB.MOM.WW.LocalDb/tests/ZB.MOM.WW.LocalDb.Tests/ZB.MOM.WW.LocalDb.Tests.csproj b/ZB.MOM.WW.LocalDb/tests/ZB.MOM.WW.LocalDb.Tests/ZB.MOM.WW.LocalDb.Tests.csproj
new file mode 100644
index 0000000..f7dbf21
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/tests/ZB.MOM.WW.LocalDb.Tests/ZB.MOM.WW.LocalDb.Tests.csproj
@@ -0,0 +1,35 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="xunit" />
+    <PackageReference Include="xunit.runner.visualstudio" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
+    <PackageReference Include="Microsoft.Extensions.Configuration" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+    <PackageReference Include="Microsoft.AspNetCore.TestHost" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\ZB.MOM.WW.LocalDb\ZB.MOM.WW.LocalDb.csproj" />
+    <ProjectReference Include="..\..\src\ZB.MOM.WW.LocalDb.Contracts\ZB.MOM.WW.LocalDb.Contracts.csproj" />
+    <ProjectReference Include="..\..\src\ZB.MOM.WW.LocalDb.Replication\ZB.MOM.WW.LocalDb.Replication.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+</Project>