diff --git a/.dockerignore b/.dockerignore
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index 0000000..6dc6bf7
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,36 @@
+# Git
+.git
+.gitignore
+.gitattributes
+
+# Build outputs
+bin/
+obj/
+*.dll
+*.exe
+*.pdb
+
+# IDE
+.vs/
+.vscode/
+*.user
+*.sln.iml
+.idea/
+
+# CI/CD
+.github/
+Jenkinsfile
+
+# Package managers
+*.lock
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Documentation
+*.md
+LICENSE
+
+# Test results
+TestResults/
diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
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--- /dev/null
+++ b/.github/copilot-instructions.md
@@ -0,0 +1,109 @@
+# Copilot Instructions for MyNumber.NET
+
+## Project Overview
+MyNumber.NET is a .NET 8.0 library for validating and generating Japanese My Number (Social Security/Tax ID). The solution contains four projects:
+- **MyNumberNET**: Core validation/generation library
+- **MyNumberNET_ApiServer**: ASP.NET Core REST API wrapper
+- **MyNumberNET_CLI**: Command-line interface with NLog logging
+- **MyNumberNET_Test**: xUnit unit tests
+
+## Architecture & Key Patterns
+
+### Core Validation Logic
+The `MyNumber` static class in [MyNumberNET/MyNumber.cs](MyNumberNET/MyNumber.cs) implements the My Number algorithm:
+- **VerifyNumber()**: Validates 12-digit arrays using check digit algorithm (positions 1-6 use weight 2-7, positions 7-11 use weight 1-6)
+- **CalculateCheckDigits()**: Computes 12th digit from first 11 (modulo 11 formula: if sum%11 ≤ 1, checkdigit=0; else checkdigit=11-sum%11)
+- Throws `MyNumberMalformedException` for invalid input (null, wrong length, non-digits)
+
+### MyNumberValue - Type-Safe Wrapper
+`MyNumberValue` readonly struct (in [MyNumberNET/MyNumber.cs](MyNumberNET/MyNumber.cs)) wraps validated numbers:
+- Immutable and always valid on construction
+- Multiple constructors: from int[], from 12 individual digits, or `FromFirstElevenDigits()` (auto-calculates check digit)
+- `TryParse(string)` handles separator formats (spaces, hyphens, underscores)
+- `ToString(format)` supports: "N" (plain), "S" (spaced), "H" (hyphenated), "G" (grouped)
+
+### API Layer Pattern
+[MyNumberNET_ApiServer/Controllers/MyNumberController.cs](MyNumberNET_ApiServer/Controllers/MyNumberController.cs) duplicates input validation before calling business logic - this is intentional to prevent malformed requests from reaching the library.
+
+## Critical Workflows
+
+### Building & Testing
+```powershell
+dotnet build                              # Build solution
+dotnet test MyNumberNET_Test              # Run tests
+dotnet run --project MyNumberNET_ApiServer # Start API on port 5000+
+dotnet run --project MyNumberNET_CLI -- generate 10  # CLI with args
+```
+
+### CLI Commands
+Located in [MyNumberNET_CLI/Program.cs](MyNumberNET_CLI/Program.cs) switch statement:
+- `generate [count]` - Random valid My Numbers
+- `check [number]` - Validate single number
+- `complete [11digits]` - Calculate check digit
+- `rangen [min] [max]` - Numerical range generation
+- `ranges [min] [max]` - Sequential range generation
+
+### Version Management
+All versions defined in [Directory.Build.props](Directory.Build.props):
+- Update `MyNumberNETVersion`, `MyNumberNETCliVersion`, `MyNumberNETTestVersion` for releases
+- Target framework: .NET 8.0 (specified in [global.json](global.json))
+
+## Integration Points & Dependencies
+
+### Exception Hierarchy
+- Base: `MyNumber.MyNumberException(message)`
+- Specific: `MyNumber.MyNumberMalformedException(message)` - thrown on validation failure
+- API returns `BadRequest` + error message on exceptions; never propagates exceptions
+
+### NLog Configuration
+CLI project uses [MyNumberNET_CLI/nlog.config](MyNumberNET_CLI/nlog.config) for logging. Logger accessed via `LogManager.GetCurrentClassLogger()`.
+
+### No External Dependencies
+Core library only uses System.* namespaces - no NuGet dependencies. Keep it minimal.
+
+## Code Patterns
+
+### Error Handling
+1. Validate inputs early (null, length, digit range)
+2. Throw `MyNumberMalformedException` with descriptive messages
+3. In API: catch exceptions and return `BadRequest(ex.Message)`
+
+### Digit Array Conventions
+- 12-digit arrays: indices 0-10 are data, 11 is check digit
+- Use `Truncate()` private method to extract first 11 digits
+- Always clone arrays when storing (immutability)
+
+### Testing Strategy
+Test files: [MyNumberNET_Test/MyNumberValueTests.cs](MyNumberNET_Test/MyNumberValueTests.cs), [MyNumberNET_Test/MyNumberControllerTests.cs](MyNumberNET_Test/MyNumberControllerTests.cs)
+- Test both valid and malformed inputs
+- Verify exception messages and types
+- Test all format options for ToString()## Containerization & Deployment
+
+### Docker
+[MyNumberNET_ApiServer/Dockerfile](MyNumberNET_ApiServer/Dockerfile) uses multi-stage build:
+1. **Build stage**: Restores, builds, and publishes using .NET 8.0 SDK
+2. **Runtime stage**: Runs on .NET 8.0 ASP.NET Core runtime (smaller image)
+3. **Port**: Exposes 5000 (configurable via `ASPNETCORE_URLS` env var)
+4. **Health check**: Built-in liveness probe every 30 seconds
+
+Local Docker usage:
+```bash
+docker build -f MyNumberNET_ApiServer/Dockerfile -t mynumberapi:latest .
+docker run -p 5000:5000 mynumberapi:latest
+```
+
+### GitHub Container Registry
+Images pushed to `ghcr.io/hsaito/mynumberapi` on main branch pushes and tags (v* releases).
+Tags: branch name, semantic version (v1.0.0), git SHA.
+
+## CI/CD
+
+### GitHub Actions Workflows
+- **[.github/workflows/dotnet-ci.yml](.github/workflows/dotnet-ci.yml)**: Cross-platform build/test (Windows, Linux, macOS)
+- **[.github/workflows/docker-build.yml](.github/workflows/docker-build.yml)**: Docker image build and push to ghcr.io
+  - Automatically tags releases (semantic versioning supported)
+  - PR builds test image without pushing
+  - Uses Buildx for efficient multi-stage builds
+
+### Legacy CI
+[Jenkinsfile](Jenkinsfile) provides additional build/test/package orchestration. Deterministic builds enabled via [Directory.Build.props](Directory.Build.props) for reproducible artifacts.
diff --git a/.github/workflows/docker-build.yml b/.github/workflows/docker-build.yml
new file mode 100644
index 0000000..b3d1748
--- /dev/null
+++ b/.github/workflows/docker-build.yml
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+name: Docker Build & Push
+
+permissions:
+  contents: read
+  packages: write
+
+on:
+  push:
+    branches: [ "main" ]
+    tags: [ "v*" ]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}/mynumberapi
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Container Registry
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=sha
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: ./MyNumberNET_ApiServer/Dockerfile
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+  test-docker-image:
+    needs: build-and-push
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: ./MyNumberNET_ApiServer/Dockerfile
+          push: false
+          cache-from: type=gha
diff --git a/Jenkinsfile b/Jenkinsfile
deleted file mode 100644
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--- a/Jenkinsfile
+++ /dev/null
@@ -1,30 +0,0 @@
-pipeline {
-    agent any
-
-    stages {
-        stage('Build') {
-            steps {
-                echo 'Building..'
-                                powershell label: '', script: '''dotnet restore; dotnet build'''
-            }
-        }
-
-	stage('Test') {
-	    steps {
-		echo 'Testing..'
-		powershell label: '', script: '''dotnet restore; dotnet test -c Release'''
-            }
-	}
-        stage('Deploy') {
-            steps {
-                echo 'Deploying..'
-                powershell label: '', script: '''dotnet restore; dotnet publish -c Release'''
-		powershell label: '', script: '''dotnet pack -c Release'''
-                archiveArtifacts artifacts: 'MyNumberNET/bin/Release/netstandard2.0/publish/**'
-		archiveArtifacts artifacts: 'MyNumberNET/bin/Release/*.nupkg'
-		archiveArtifacts artifacts: 'MyNumberNET_CLI/bin/Release/netcoreapp2.1/publish/'
-            }
-        }
-
-    }
-}
diff --git a/MyNumberNET_ApiServer/Dockerfile b/MyNumberNET_ApiServer/Dockerfile
new file mode 100644
index 0000000..1012b1c
--- /dev/null
+++ b/MyNumberNET_ApiServer/Dockerfile
@@ -0,0 +1,43 @@
+# Build stage
+FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
+WORKDIR /src
+
+# Copy project files
+COPY ["MyNumberNET/MyNumberNET.csproj", "MyNumberNET/"]
+COPY ["MyNumberNET_ApiServer/MyNumberNET_ApiServer.csproj", "MyNumberNET_ApiServer/"]
+COPY ["Directory.Build.props", "."]
+COPY ["global.json", "."]
+
+# Restore dependencies
+RUN dotnet restore "MyNumberNET_ApiServer/MyNumberNET_ApiServer.csproj"
+
+# Copy source files
+COPY ["MyNumberNET/", "MyNumberNET/"]
+COPY ["MyNumberNET_ApiServer/", "MyNumberNET_ApiServer/"]
+
+# Build application
+RUN dotnet build "MyNumberNET_ApiServer/MyNumberNET_ApiServer.csproj" -c Release --no-restore
+
+# Publish application
+RUN dotnet publish "MyNumberNET_ApiServer/MyNumberNET_ApiServer.csproj" -c Release -o /app/publish --no-build
+
+# Runtime stage
+FROM mcr.microsoft.com/dotnet/aspnet:8.0
+WORKDIR /app
+
+# Copy published application from build stage
+COPY --from=build /app/publish .
+
+# Set environment variables for ASP.NET Core
+ENV ASPNETCORE_URLS=http://+:5000
+ENV ASPNETCORE_ENVIRONMENT=Production
+
+# Expose port
+EXPOSE 5000
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+  CMD dotnet /app/MyNumberNET_ApiServer.dll || exit 1
+
+# Start application
+ENTRYPOINT ["dotnet", "MyNumberNET_ApiServer.dll"]