diff --git a/clients/java/Makefile b/clients/java/Makefile
new file mode 100644
index 0000000..4915796
--- /dev/null
+++ b/clients/java/Makefile
@@ -0,0 +1,248 @@
+# UN Java Client - Build and Test
+#
+# This client has two implementations:
+#   - sync/  : Synchronous Java SDK (HttpURLConnection)
+#   - async/ : Asynchronous Java SDK (CompletableFuture/HttpClient)
+#
+# Usage:
+#   make              # Build all
+#   make test         # Run all 4 test modes
+#   make test-cli     # CLI mode only
+#   make test-library # Library mode only
+#   make test-integration # Integration mode only
+#   make test-functional  # Functional mode only
+#   make build        # Build JAR files
+#   make clean        # Remove build artifacts
+#
+# Dependencies:
+#   Java 11+ (for HttpClient)
+#   Maven or Gradle
+
+.PHONY: all build test test-cli test-library test-integration test-functional
+.PHONY: test-sync test-async clean help examples
+
+# Paths
+ROOT_DIR := $(shell cd ../.. && pwd)
+SYNC_DIR := sync
+ASYNC_DIR := async
+
+# Java settings
+JAVA := java
+JAVAC := javac
+MAVEN := mvn
+GRADLE := gradle
+
+# Colors
+GREEN := \033[32m
+RED := \033[31m
+YELLOW := \033[33m
+NC := \033[0m
+
+.DEFAULT_GOAL := help
+
+help:
+	@echo "UN Java Client - Build and Test"
+	@echo ""
+	@echo "Build:"
+	@echo "  make build            Build all JARs"
+	@echo "  make build-sync       Build sync SDK"
+	@echo "  make build-async      Build async SDK"
+	@echo ""
+	@echo "Test (all 4 modes):"
+	@echo "  make test             All 4 modes for both sync and async"
+	@echo "  make test-cli         CLI mode (command-line interface)"
+	@echo "  make test-library     Library mode (JUnit tests)"
+	@echo "  make test-integration Integration mode (API contract)"
+	@echo "  make test-functional  Functional mode (real-world scenarios)"
+	@echo ""
+	@echo "Test by SDK:"
+	@echo "  make test-sync        Test synchronous SDK"
+	@echo "  make test-async       Test asynchronous SDK"
+	@echo ""
+	@echo "Utility:"
+	@echo "  make clean            Remove build artifacts"
+	@echo "  make deps             Show required dependencies"
+	@echo ""
+
+all: build
+
+deps:
+	@echo "Required:"
+	@echo "  Java 11+ (for HttpClient)"
+	@echo "  Maven or Gradle"
+	@echo ""
+	@java -version 2>&1 | head -1 || echo "Java not installed"
+	@mvn --version 2>/dev/null | head -1 || echo "Maven not installed (optional)"
+	@gradle --version 2>/dev/null | head -1 || echo "Gradle not installed (optional)"
+
+# ============================================================================
+# BUILD
+# ============================================================================
+
+build: build-sync build-async
+	@echo "$(GREEN)✓ All Java SDKs built$(NC)"
+
+build-sync:
+	@echo "Building sync SDK..."
+	@if [ -f "$(SYNC_DIR)/pom.xml" ]; then \
+		cd $(SYNC_DIR) && $(MAVEN) compile -q && echo "$(GREEN)✓$(NC) Sync SDK compiled (Maven)"; \
+	elif [ -f "$(SYNC_DIR)/build.gradle" ]; then \
+		cd $(SYNC_DIR) && $(GRADLE) build -q && echo "$(GREEN)✓$(NC) Sync SDK compiled (Gradle)"; \
+	elif [ -d "$(SYNC_DIR)/src" ]; then \
+		echo "$(YELLOW)⊘$(NC) Sync SDK needs pom.xml or build.gradle"; \
+	else \
+		echo "$(YELLOW)⊘$(NC) Sync SDK not found"; \
+	fi
+
+build-async:
+	@echo "Building async SDK..."
+	@if [ -f "$(ASYNC_DIR)/pom.xml" ]; then \
+		cd $(ASYNC_DIR) && $(MAVEN) compile -q && echo "$(GREEN)✓$(NC) Async SDK compiled (Maven)"; \
+	elif [ -f "$(ASYNC_DIR)/build.gradle" ]; then \
+		cd $(ASYNC_DIR) && $(GRADLE) build -q && echo "$(GREEN)✓$(NC) Async SDK compiled (Gradle)"; \
+	elif [ -d "$(ASYNC_DIR)/src" ]; then \
+		echo "$(YELLOW)⊘$(NC) Async SDK needs pom.xml or build.gradle"; \
+	else \
+		echo "$(YELLOW)⊘$(NC) Async SDK not found"; \
+	fi
+
+# ============================================================================
+# TEST: All 4 Modes
+# ============================================================================
+
+test: test-cli test-library test-integration test-functional
+	@echo ""
+	@echo "$(GREEN)✓ Java Client: All 4 test modes complete$(NC)"
+
+# ============================================================================
+# TEST: CLI Mode
+# ============================================================================
+
+test-cli:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "CLI MODE: Testing Java CLI interface"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test sync SDK compile
+	@if [ -f "$(SYNC_DIR)/pom.xml" ]; then \
+		cd $(SYNC_DIR) && $(MAVEN) compile -q 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Sync SDK compiles (Maven)" || echo "  $(RED)✗$(NC) CLI: Sync SDK compile failed"; \
+	elif [ -f "$(SYNC_DIR)/build.gradle" ]; then \
+		cd $(SYNC_DIR) && $(GRADLE) compileJava -q 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Sync SDK compiles (Gradle)" || echo "  $(RED)✗$(NC) CLI: Sync SDK compile failed"; \
+	elif [ -d "$(SYNC_DIR)/src" ]; then \
+		echo "  $(YELLOW)⊘$(NC) CLI: Sync SDK needs build configuration"; \
+	fi
+	@# Test async SDK compile
+	@if [ -f "$(ASYNC_DIR)/pom.xml" ]; then \
+		cd $(ASYNC_DIR) && $(MAVEN) compile -q 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Async SDK compiles (Maven)" || echo "  $(YELLOW)⊘$(NC) CLI: Async SDK not yet buildable"; \
+	elif [ -f "$(ASYNC_DIR)/build.gradle" ]; then \
+		cd $(ASYNC_DIR) && $(GRADLE) compileJava -q 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Async SDK compiles (Gradle)" || echo "  $(YELLOW)⊘$(NC) CLI: Async SDK not yet buildable"; \
+	fi
+
+# ============================================================================
+# TEST: Library Mode
+# ============================================================================
+
+test-library:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "LIBRARY MODE: Testing Java classes"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test sync SDK with Maven/Gradle test
+	@if [ -f "$(SYNC_DIR)/pom.xml" ]; then \
+		cd $(SYNC_DIR) && $(MAVEN) test -q 2>&1 | tail -10 || echo "  $(YELLOW)⊘$(NC) Library: Sync tests incomplete"; \
+	elif [ -f "$(SYNC_DIR)/build.gradle" ]; then \
+		cd $(SYNC_DIR) && $(GRADLE) test -q 2>&1 | tail -10 || echo "  $(YELLOW)⊘$(NC) Library: Sync tests incomplete"; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Library: Sync SDK needs build configuration"; \
+	fi
+	@# Test async SDK
+	@if [ -f "$(ASYNC_DIR)/pom.xml" ]; then \
+		cd $(ASYNC_DIR) && $(MAVEN) test -q 2>&1 | tail -10 || echo "  $(YELLOW)⊘$(NC) Library: Async tests incomplete"; \
+	elif [ -f "$(ASYNC_DIR)/build.gradle" ]; then \
+		cd $(ASYNC_DIR) && $(GRADLE) test -q 2>&1 | tail -10 || echo "  $(YELLOW)⊘$(NC) Library: Async tests incomplete"; \
+	fi
+
+# ============================================================================
+# TEST: Integration Mode
+# ============================================================================
+
+test-integration:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "INTEGRATION MODE: Testing API contract"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+		echo "  Set UNSANDBOX_PUBLIC_KEY and UNSANDBOX_SECRET_KEY"; \
+	else \
+		echo "  Testing API authentication..."; \
+		echo "  $(YELLOW)⊘$(NC) Integration: SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: Functional Mode
+# ============================================================================
+
+test-functional:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "FUNCTIONAL MODE: Real-world scenarios"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+	else \
+		echo "  Running functional tests..."; \
+		echo "  $(YELLOW)⊘$(NC) Functional: SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: By SDK Type
+# ============================================================================
+
+test-sync:
+	@echo "Testing Sync SDK..."
+	@if [ -f "$(SYNC_DIR)/pom.xml" ]; then \
+		cd $(SYNC_DIR) && $(MAVEN) test; \
+	elif [ -f "$(SYNC_DIR)/build.gradle" ]; then \
+		cd $(SYNC_DIR) && $(GRADLE) test; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Sync SDK tests not found"; \
+	fi
+
+test-async:
+	@echo "Testing Async SDK..."
+	@if [ -f "$(ASYNC_DIR)/pom.xml" ]; then \
+		cd $(ASYNC_DIR) && $(MAVEN) test; \
+	elif [ -f "$(ASYNC_DIR)/build.gradle" ]; then \
+		cd $(ASYNC_DIR) && $(GRADLE) test; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Async SDK tests not found"; \
+	fi
+
+# ============================================================================
+# Examples
+# ============================================================================
+
+examples:
+	@echo "Running Java examples..."
+	@if [ -f "$(SYNC_DIR)/pom.xml" ]; then \
+		cd $(SYNC_DIR) && $(MAVEN) exec:java -Dexec.mainClass="examples.HelloWorld" 2>&1 | head -10 || true; \
+	fi
+
+# ============================================================================
+# Clean
+# ============================================================================
+
+clean:
+	@echo "Cleaning Java build artifacts..."
+	@if [ -f "$(SYNC_DIR)/pom.xml" ]; then cd $(SYNC_DIR) && $(MAVEN) clean -q 2>/dev/null || true; fi
+	@if [ -f "$(ASYNC_DIR)/pom.xml" ]; then cd $(ASYNC_DIR) && $(MAVEN) clean -q 2>/dev/null || true; fi
+	@if [ -f "$(SYNC_DIR)/build.gradle" ]; then cd $(SYNC_DIR) && $(GRADLE) clean -q 2>/dev/null || true; fi
+	@if [ -f "$(ASYNC_DIR)/build.gradle" ]; then cd $(ASYNC_DIR) && $(GRADLE) clean -q 2>/dev/null || true; fi
+	@rm -rf $(SYNC_DIR)/target $(ASYNC_DIR)/target 2>/dev/null || true
+	@rm -rf $(SYNC_DIR)/build $(ASYNC_DIR)/build 2>/dev/null || true
+	@echo "$(GREEN)✓$(NC) Cleaned build artifacts"
diff --git a/clients/javascript/Makefile b/clients/javascript/Makefile
new file mode 100644
index 0000000..abf6e20
--- /dev/null
+++ b/clients/javascript/Makefile
@@ -0,0 +1,234 @@
+# UN JavaScript Client - Build and Test
+#
+# This client has two implementations:
+#   - sync/  : Synchronous/Promise-based SDK (Node.js)
+#   - async/ : Async/Await SDK (Node.js)
+#
+# Usage:
+#   make              # Run all tests
+#   make test         # Run all 4 test modes
+#   make test-cli     # CLI mode only
+#   make test-library # Library mode only
+#   make test-integration # Integration mode only
+#   make test-functional  # Functional mode only
+#   make test-sync    # Test sync SDK only
+#   make test-async   # Test async SDK only
+#   make clean        # Remove build artifacts
+#
+# Dependencies:
+#   npm install (or yarn install)
+
+.PHONY: all test test-cli test-library test-integration test-functional
+.PHONY: test-sync test-async install dev-install lint format clean help examples
+
+# Paths
+ROOT_DIR := $(shell cd ../.. && pwd)
+SYNC_DIR := sync
+ASYNC_DIR := async
+
+# Colors
+GREEN := \033[32m
+RED := \033[31m
+YELLOW := \033[33m
+NC := \033[0m
+
+.DEFAULT_GOAL := help
+
+help:
+	@echo "UN JavaScript Client - Build and Test"
+	@echo ""
+	@echo "Test (all 4 modes):"
+	@echo "  make test               All 4 modes for both sync and async"
+	@echo "  make test-cli           CLI mode (command-line interface)"
+	@echo "  make test-library       Library mode (require and use)"
+	@echo "  make test-integration   Integration mode (API contract)"
+	@echo "  make test-functional    Functional mode (real-world scenarios)"
+	@echo ""
+	@echo "Test by SDK:"
+	@echo "  make test-sync          Test synchronous SDK"
+	@echo "  make test-async         Test asynchronous SDK"
+	@echo ""
+	@echo "Development:"
+	@echo "  make install            Install dependencies"
+	@echo "  make lint               Lint with ESLint"
+	@echo "  make format             Format with Prettier"
+	@echo "  make examples           Run example scripts"
+	@echo ""
+	@echo "Utility:"
+	@echo "  make clean              Remove build artifacts"
+	@echo "  make deps               Show required dependencies"
+	@echo ""
+
+all: test
+
+deps:
+	@echo "Required packages:"
+	@echo "  npm install jest eslint prettier"
+	@echo ""
+	@node --version 2>/dev/null || echo "Node.js not installed"
+
+# ============================================================================
+# TEST: All 4 Modes
+# ============================================================================
+
+test: test-cli test-library test-integration test-functional
+	@echo ""
+	@echo "$(GREEN)✓ JavaScript Client: All 4 test modes complete$(NC)"
+
+# ============================================================================
+# TEST: CLI Mode
+# ============================================================================
+
+test-cli:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "CLI MODE: Testing JavaScript CLI interface"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test root-level un.js if it exists
+	@if [ -f "$(ROOT_DIR)/un.js" ]; then \
+		node --check "$(ROOT_DIR)/un.js" 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Syntax valid (un.js)" || echo "  $(RED)✗$(NC) CLI: Syntax error in un.js"; \
+	fi
+	@# Test sync SDK syntax
+	@if [ -f "$(SYNC_DIR)/src/un.js" ]; then \
+		node --check "$(SYNC_DIR)/src/un.js" 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Sync SDK syntax valid" || echo "  $(RED)✗$(NC) CLI: Sync SDK syntax error"; \
+	fi
+	@# Test async SDK syntax
+	@if [ -f "$(ASYNC_DIR)/src/un.js" ]; then \
+		node --check "$(ASYNC_DIR)/src/un.js" 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Async SDK syntax valid" || echo "  $(YELLOW)⊘$(NC) CLI: Async SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: Library Mode
+# ============================================================================
+
+test-library:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "LIBRARY MODE: Testing JavaScript imports"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test sync SDK import
+	@if [ -f "$(SYNC_DIR)/src/un.js" ]; then \
+		node -e "const un = require('./$(SYNC_DIR)/src/un.js'); console.log('  ✓ Library: Sync SDK importable, exports:', Object.keys(un).length, 'functions')" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Sync import needs dependencies"; \
+	fi
+	@# Test async SDK import
+	@if [ -f "$(ASYNC_DIR)/src/un.js" ]; then \
+		node -e "const un = require('./$(ASYNC_DIR)/src/un.js'); console.log('  ✓ Library: Async SDK importable')" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Async SDK not yet implemented"; \
+	fi
+	@# Run jest tests
+	@echo ""
+	@echo "Running unit tests..."
+	@if [ -d "$(SYNC_DIR)/tests" ] && [ -f "$(SYNC_DIR)/package.json" ]; then \
+		cd $(SYNC_DIR) && npm test 2>/dev/null && echo "  $(GREEN)✓$(NC) Sync SDK tests passed" || echo "  $(YELLOW)⊘$(NC) Sync tests need: npm install"; \
+	elif [ -d "$(SYNC_DIR)/tests" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Sync tests need package.json"; \
+	fi
+	@if [ -d "$(ASYNC_DIR)/tests" ] && [ -f "$(ASYNC_DIR)/package.json" ]; then \
+		cd $(ASYNC_DIR) && npm test 2>/dev/null && echo "  $(GREEN)✓$(NC) Async SDK tests passed" || echo "  $(YELLOW)⊘$(NC) Async tests need: npm install"; \
+	fi
+
+# ============================================================================
+# TEST: Integration Mode
+# ============================================================================
+
+test-integration:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "INTEGRATION MODE: Testing API contract"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+		echo "  Set UNSANDBOX_PUBLIC_KEY and UNSANDBOX_SECRET_KEY"; \
+	else \
+		echo "  Testing API authentication..."; \
+		if [ -f "$(SYNC_DIR)/src/un.js" ]; then \
+			node -e "const un = require('./$(SYNC_DIR)/src/un.js'); un.executeCode('python', 'print(42)').then(r => { if(r.stdout && r.stdout.includes('42')) console.log('  ✓ Integration: API auth works'); else console.log('  ✗ Integration: Unexpected response'); }).catch(e => console.log('  ✗ Integration:', e.message))" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Integration: Check SDK"; \
+		fi; \
+	fi
+
+# ============================================================================
+# TEST: Functional Mode
+# ============================================================================
+
+test-functional:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "FUNCTIONAL MODE: Real-world scenarios"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+	else \
+		echo "  Running functional tests..."; \
+		if [ -f "$(SYNC_DIR)/src/un.js" ]; then \
+			node -e "const un = require('./$(SYNC_DIR)/src/un.js'); un.executeCode('python', 'def fib(n): return n if n<2 else fib(n-1)+fib(n-2); print(fib(10))').then(r => { if(r.stdout && r.stdout.includes('55')) console.log('  ✓ Functional: Fibonacci'); else console.log('  ⊘ Functional: Check output'); }).catch(e => console.log('  ⊘ Functional:', e.message))" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Functional: Check SDK"; \
+		fi; \
+	fi
+
+# ============================================================================
+# TEST: By SDK Type
+# ============================================================================
+
+test-sync:
+	@echo "Testing Sync SDK..."
+	@if [ -f "$(SYNC_DIR)/package.json" ]; then \
+		cd $(SYNC_DIR) && npm test; \
+	elif [ -d "$(SYNC_DIR)/tests" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Sync SDK needs package.json with test script"; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Sync SDK tests not found"; \
+	fi
+
+test-async:
+	@echo "Testing Async SDK..."
+	@if [ -f "$(ASYNC_DIR)/package.json" ]; then \
+		cd $(ASYNC_DIR) && npm test; \
+	elif [ -d "$(ASYNC_DIR)/tests" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Async SDK needs package.json with test script"; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Async SDK tests not found"; \
+	fi
+
+# ============================================================================
+# Development
+# ============================================================================
+
+install:
+	@echo "Installing JavaScript SDK dependencies..."
+	@if [ -f "$(SYNC_DIR)/package.json" ]; then cd $(SYNC_DIR) && npm install; fi
+	@if [ -f "$(ASYNC_DIR)/package.json" ]; then cd $(ASYNC_DIR) && npm install; fi
+	@echo "$(GREEN)✓$(NC) Installation complete"
+
+lint:
+	@echo "Linting JavaScript SDKs..."
+	@if [ -d "$(SYNC_DIR)/src" ]; then npx eslint $(SYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) ESLint not configured"; fi
+	@if [ -d "$(ASYNC_DIR)/src" ]; then npx eslint $(ASYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) ESLint not configured"; fi
+	@echo "$(GREEN)✓$(NC) Lint complete"
+
+format:
+	@echo "Formatting JavaScript SDKs..."
+	@if [ -d "$(SYNC_DIR)/src" ]; then npx prettier --write $(SYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Prettier not installed"; fi
+	@if [ -d "$(ASYNC_DIR)/src" ]; then npx prettier --write $(ASYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Prettier not installed"; fi
+	@echo "$(GREEN)✓$(NC) Format complete"
+
+examples:
+	@echo "Running JavaScript examples..."
+	@if [ -d "$(SYNC_DIR)/examples" ]; then \
+		for f in $(SYNC_DIR)/examples/*.js; do \
+			echo "Running $$f..."; \
+			node "$$f" 2>&1 | head -10 || true; \
+		done; \
+	fi
+
+# ============================================================================
+# Clean
+# ============================================================================
+
+clean:
+	@echo "Cleaning JavaScript build artifacts..."
+	@rm -rf $(SYNC_DIR)/node_modules $(ASYNC_DIR)/node_modules 2>/dev/null || true
+	@rm -rf $(SYNC_DIR)/coverage $(ASYNC_DIR)/coverage 2>/dev/null || true
+	@rm -f $(SYNC_DIR)/package-lock.json $(ASYNC_DIR)/package-lock.json 2>/dev/null || true
+	@echo "$(GREEN)✓$(NC) Cleaned build artifacts"
diff --git a/clients/php/Makefile b/clients/php/Makefile
new file mode 100644
index 0000000..29b37f8
--- /dev/null
+++ b/clients/php/Makefile
@@ -0,0 +1,232 @@
+# UN PHP Client - Build and Test
+#
+# This client has two implementations:
+#   - sync/  : Synchronous PHP SDK (curl)
+#   - async/ : Asynchronous PHP SDK (ReactPHP/Amp)
+#
+# Usage:
+#   make              # Run all tests
+#   make test         # Run all 4 test modes
+#   make test-cli     # CLI mode only
+#   make test-library # Library mode only
+#   make test-integration # Integration mode only
+#   make test-functional  # Functional mode only
+#   make test-sync    # Test sync SDK only
+#   make test-async   # Test async SDK only
+#   make clean        # Remove build artifacts
+#
+# Dependencies:
+#   composer require phpunit/phpunit
+
+.PHONY: all test test-cli test-library test-integration test-functional
+.PHONY: test-sync test-async install dev-install lint format clean help examples
+
+# Paths
+ROOT_DIR := $(shell cd ../.. && pwd)
+SYNC_DIR := sync
+ASYNC_DIR := async
+
+# Colors
+GREEN := \033[32m
+RED := \033[31m
+YELLOW := \033[33m
+NC := \033[0m
+
+.DEFAULT_GOAL := help
+
+help:
+	@echo "UN PHP Client - Build and Test"
+	@echo ""
+	@echo "Test (all 4 modes):"
+	@echo "  make test               All 4 modes for both sync and async"
+	@echo "  make test-cli           CLI mode (command-line interface)"
+	@echo "  make test-library       Library mode (require and use)"
+	@echo "  make test-integration   Integration mode (API contract)"
+	@echo "  make test-functional    Functional mode (real-world scenarios)"
+	@echo ""
+	@echo "Test by SDK:"
+	@echo "  make test-sync          Test synchronous SDK"
+	@echo "  make test-async         Test asynchronous SDK"
+	@echo ""
+	@echo "Development:"
+	@echo "  make install            Install dependencies"
+	@echo "  make lint               Lint with PHP_CodeSniffer"
+	@echo "  make format             Format with PHP-CS-Fixer"
+	@echo "  make examples           Run example scripts"
+	@echo ""
+	@echo "Utility:"
+	@echo "  make clean              Remove build artifacts"
+	@echo "  make deps               Show required dependencies"
+	@echo ""
+
+all: test
+
+deps:
+	@echo "Required packages:"
+	@echo "  composer require phpunit/phpunit squizlabs/php_codesniffer"
+	@echo ""
+	@php --version 2>/dev/null || echo "PHP not installed"
+	@composer --version 2>/dev/null || echo "Composer not installed"
+
+# ============================================================================
+# TEST: All 4 Modes
+# ============================================================================
+
+test: test-cli test-library test-integration test-functional
+	@echo ""
+	@echo "$(GREEN)✓ PHP Client: All 4 test modes complete$(NC)"
+
+# ============================================================================
+# TEST: CLI Mode
+# ============================================================================
+
+test-cli:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "CLI MODE: Testing PHP CLI interface"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test root-level un.php if it exists
+	@if [ -f "$(ROOT_DIR)/un.php" ]; then \
+		php -l "$(ROOT_DIR)/un.php" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Syntax valid (un.php)" || echo "  $(RED)✗$(NC) CLI: Syntax error in un.php"; \
+	fi
+	@# Test sync SDK syntax
+	@if [ -f "$(SYNC_DIR)/src/Unsandbox.php" ]; then \
+		php -l "$(SYNC_DIR)/src/Unsandbox.php" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Sync SDK syntax valid" || echo "  $(RED)✗$(NC) CLI: Sync SDK syntax error"; \
+	elif [ -f "$(SYNC_DIR)/src/un.php" ]; then \
+		php -l "$(SYNC_DIR)/src/un.php" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Sync SDK syntax valid" || echo "  $(RED)✗$(NC) CLI: Sync SDK syntax error"; \
+	fi
+	@# Test async SDK syntax
+	@if [ -f "$(ASYNC_DIR)/src/Unsandbox.php" ]; then \
+		php -l "$(ASYNC_DIR)/src/Unsandbox.php" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Async SDK syntax valid" || echo "  $(YELLOW)⊘$(NC) CLI: Async SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: Library Mode
+# ============================================================================
+
+test-library:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "LIBRARY MODE: Testing PHP imports"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test sync SDK import
+	@if [ -f "$(SYNC_DIR)/src/Unsandbox.php" ]; then \
+		php -r "require '$(SYNC_DIR)/src/Unsandbox.php'; echo '  ✓ Library: Sync SDK importable\n';" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Sync import needs dependencies"; \
+	elif [ -f "$(SYNC_DIR)/src/un.php" ]; then \
+		php -r "require '$(SYNC_DIR)/src/un.php'; echo '  ✓ Library: Sync SDK importable\n';" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Sync import needs dependencies"; \
+	fi
+	@# Test async SDK import
+	@if [ -f "$(ASYNC_DIR)/src/Unsandbox.php" ]; then \
+		php -r "require '$(ASYNC_DIR)/src/Unsandbox.php'; echo '  ✓ Library: Async SDK importable\n';" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Async import needs dependencies"; \
+	fi
+	@# Run phpunit tests
+	@echo ""
+	@echo "Running unit tests..."
+	@if [ -d "$(SYNC_DIR)/tests" ] && [ -f "$(SYNC_DIR)/composer.json" ]; then \
+		cd $(SYNC_DIR) && ./vendor/bin/phpunit tests/ 2>/dev/null && echo "  $(GREEN)✓$(NC) Sync SDK tests passed" || echo "  $(YELLOW)⊘$(NC) Sync tests need: composer install"; \
+	fi
+	@if [ -d "$(ASYNC_DIR)/tests" ] && [ -f "$(ASYNC_DIR)/composer.json" ]; then \
+		cd $(ASYNC_DIR) && ./vendor/bin/phpunit tests/ 2>/dev/null && echo "  $(GREEN)✓$(NC) Async SDK tests passed" || echo "  $(YELLOW)⊘$(NC) Async tests need: composer install"; \
+	fi
+
+# ============================================================================
+# TEST: Integration Mode
+# ============================================================================
+
+test-integration:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "INTEGRATION MODE: Testing API contract"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+		echo "  Set UNSANDBOX_PUBLIC_KEY and UNSANDBOX_SECRET_KEY"; \
+	else \
+		echo "  Testing API authentication..."; \
+		echo "  $(YELLOW)⊘$(NC) Integration: SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: Functional Mode
+# ============================================================================
+
+test-functional:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "FUNCTIONAL MODE: Real-world scenarios"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+	else \
+		echo "  Running functional tests..."; \
+		echo "  $(YELLOW)⊘$(NC) Functional: SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: By SDK Type
+# ============================================================================
+
+test-sync:
+	@echo "Testing Sync SDK..."
+	@if [ -f "$(SYNC_DIR)/composer.json" ]; then \
+		cd $(SYNC_DIR) && ./vendor/bin/phpunit tests/; \
+	elif [ -d "$(SYNC_DIR)/tests" ]; then \
+		cd $(SYNC_DIR) && phpunit tests/; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Sync SDK tests not found"; \
+	fi
+
+test-async:
+	@echo "Testing Async SDK..."
+	@if [ -f "$(ASYNC_DIR)/composer.json" ]; then \
+		cd $(ASYNC_DIR) && ./vendor/bin/phpunit tests/; \
+	elif [ -d "$(ASYNC_DIR)/tests" ]; then \
+		cd $(ASYNC_DIR) && phpunit tests/; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Async SDK tests not found"; \
+	fi
+
+# ============================================================================
+# Development
+# ============================================================================
+
+install:
+	@echo "Installing PHP SDK dependencies..."
+	@if [ -f "$(SYNC_DIR)/composer.json" ]; then cd $(SYNC_DIR) && composer install; fi
+	@if [ -f "$(ASYNC_DIR)/composer.json" ]; then cd $(ASYNC_DIR) && composer install; fi
+	@echo "$(GREEN)✓$(NC) Installation complete"
+
+lint:
+	@echo "Linting PHP SDKs..."
+	@if [ -d "$(SYNC_DIR)/src" ]; then phpcs $(SYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) PHP_CodeSniffer not installed"; fi
+	@if [ -d "$(ASYNC_DIR)/src" ]; then phpcs $(ASYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) PHP_CodeSniffer not installed"; fi
+	@echo "$(GREEN)✓$(NC) Lint complete"
+
+format:
+	@echo "Formatting PHP SDKs..."
+	@if [ -d "$(SYNC_DIR)/src" ]; then php-cs-fixer fix $(SYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) PHP-CS-Fixer not installed"; fi
+	@if [ -d "$(ASYNC_DIR)/src" ]; then php-cs-fixer fix $(ASYNC_DIR)/src/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) PHP-CS-Fixer not installed"; fi
+	@echo "$(GREEN)✓$(NC) Format complete"
+
+examples:
+	@echo "Running PHP examples..."
+	@if [ -d "$(SYNC_DIR)/examples" ]; then \
+		for f in $(SYNC_DIR)/examples/*.php; do \
+			echo "Running $$f..."; \
+			php "$$f" 2>&1 | head -10 || true; \
+		done; \
+	fi
+
+# ============================================================================
+# Clean
+# ============================================================================
+
+clean:
+	@echo "Cleaning PHP build artifacts..."
+	@rm -rf $(SYNC_DIR)/vendor $(ASYNC_DIR)/vendor 2>/dev/null || true
+	@rm -f $(SYNC_DIR)/composer.lock $(ASYNC_DIR)/composer.lock 2>/dev/null || true
+	@echo "$(GREEN)✓$(NC) Cleaned build artifacts"
diff --git a/clients/ruby/Makefile b/clients/ruby/Makefile
new file mode 100644
index 0000000..6657e0a
--- /dev/null
+++ b/clients/ruby/Makefile
@@ -0,0 +1,232 @@
+# UN Ruby Client - Build and Test
+#
+# This client has two implementations:
+#   - sync/  : Synchronous Ruby SDK (net/http)
+#   - async/ : Asynchronous Ruby SDK (async-http)
+#
+# Usage:
+#   make              # Run all tests
+#   make test         # Run all 4 test modes
+#   make test-cli     # CLI mode only
+#   make test-library # Library mode only
+#   make test-integration # Integration mode only
+#   make test-functional  # Functional mode only
+#   make test-sync    # Test sync SDK only
+#   make test-async   # Test async SDK only
+#   make clean        # Remove build artifacts
+#
+# Dependencies:
+#   gem install bundler rspec
+
+.PHONY: all test test-cli test-library test-integration test-functional
+.PHONY: test-sync test-async install dev-install lint format clean help examples
+
+# Paths
+ROOT_DIR := $(shell cd ../.. && pwd)
+SYNC_DIR := sync
+ASYNC_DIR := async
+
+# Colors
+GREEN := \033[32m
+RED := \033[31m
+YELLOW := \033[33m
+NC := \033[0m
+
+.DEFAULT_GOAL := help
+
+help:
+	@echo "UN Ruby Client - Build and Test"
+	@echo ""
+	@echo "Test (all 4 modes):"
+	@echo "  make test               All 4 modes for both sync and async"
+	@echo "  make test-cli           CLI mode (command-line interface)"
+	@echo "  make test-library       Library mode (require and use)"
+	@echo "  make test-integration   Integration mode (API contract)"
+	@echo "  make test-functional    Functional mode (real-world scenarios)"
+	@echo ""
+	@echo "Test by SDK:"
+	@echo "  make test-sync          Test synchronous SDK"
+	@echo "  make test-async         Test asynchronous SDK"
+	@echo ""
+	@echo "Development:"
+	@echo "  make install            Install dependencies"
+	@echo "  make lint               Lint with RuboCop"
+	@echo "  make format             Format with RuboCop"
+	@echo "  make examples           Run example scripts"
+	@echo ""
+	@echo "Utility:"
+	@echo "  make clean              Remove build artifacts"
+	@echo "  make deps               Show required dependencies"
+	@echo ""
+
+all: test
+
+deps:
+	@echo "Required packages:"
+	@echo "  gem install bundler rspec rubocop"
+	@echo ""
+	@ruby --version 2>/dev/null || echo "Ruby not installed"
+
+# ============================================================================
+# TEST: All 4 Modes
+# ============================================================================
+
+test: test-cli test-library test-integration test-functional
+	@echo ""
+	@echo "$(GREEN)✓ Ruby Client: All 4 test modes complete$(NC)"
+
+# ============================================================================
+# TEST: CLI Mode
+# ============================================================================
+
+test-cli:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "CLI MODE: Testing Ruby CLI interface"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test root-level un.rb if it exists
+	@if [ -f "$(ROOT_DIR)/un.rb" ]; then \
+		ruby -c "$(ROOT_DIR)/un.rb" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Syntax valid (un.rb)" || echo "  $(RED)✗$(NC) CLI: Syntax error in un.rb"; \
+	fi
+	@# Test sync SDK syntax
+	@if [ -f "$(SYNC_DIR)/lib/unsandbox.rb" ]; then \
+		ruby -c "$(SYNC_DIR)/lib/unsandbox.rb" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Sync SDK syntax valid" || echo "  $(RED)✗$(NC) CLI: Sync SDK syntax error"; \
+	elif [ -f "$(SYNC_DIR)/src/un.rb" ]; then \
+		ruby -c "$(SYNC_DIR)/src/un.rb" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Sync SDK syntax valid" || echo "  $(RED)✗$(NC) CLI: Sync SDK syntax error"; \
+	fi
+	@# Test async SDK syntax
+	@if [ -f "$(ASYNC_DIR)/lib/unsandbox.rb" ]; then \
+		ruby -c "$(ASYNC_DIR)/lib/unsandbox.rb" > /dev/null 2>&1 && echo "  $(GREEN)✓$(NC) CLI: Async SDK syntax valid" || echo "  $(YELLOW)⊘$(NC) CLI: Async SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: Library Mode
+# ============================================================================
+
+test-library:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "LIBRARY MODE: Testing Ruby imports"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test sync SDK import
+	@if [ -f "$(SYNC_DIR)/lib/unsandbox.rb" ]; then \
+		ruby -I$(SYNC_DIR)/lib -e "require 'unsandbox'; puts '  ✓ Library: Sync SDK importable'" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Sync import needs dependencies"; \
+	elif [ -f "$(SYNC_DIR)/src/un.rb" ]; then \
+		ruby -I$(SYNC_DIR)/src -e "require 'un'; puts '  ✓ Library: Sync SDK importable'" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Sync import needs dependencies"; \
+	fi
+	@# Test async SDK import
+	@if [ -f "$(ASYNC_DIR)/lib/unsandbox.rb" ]; then \
+		ruby -I$(ASYNC_DIR)/lib -e "require 'unsandbox'; puts '  ✓ Library: Async SDK importable'" 2>/dev/null || echo "  $(YELLOW)⊘$(NC) Library: Async import needs dependencies"; \
+	fi
+	@# Run rspec tests
+	@echo ""
+	@echo "Running unit tests..."
+	@if [ -d "$(SYNC_DIR)/spec" ]; then \
+		cd $(SYNC_DIR) && bundle exec rspec spec/ 2>/dev/null && echo "  $(GREEN)✓$(NC) Sync SDK tests passed" || echo "  $(YELLOW)⊘$(NC) Sync tests need: bundle install"; \
+	fi
+	@if [ -d "$(ASYNC_DIR)/spec" ]; then \
+		cd $(ASYNC_DIR) && bundle exec rspec spec/ 2>/dev/null && echo "  $(GREEN)✓$(NC) Async SDK tests passed" || echo "  $(YELLOW)⊘$(NC) Async tests need: bundle install"; \
+	fi
+
+# ============================================================================
+# TEST: Integration Mode
+# ============================================================================
+
+test-integration:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "INTEGRATION MODE: Testing API contract"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+		echo "  Set UNSANDBOX_PUBLIC_KEY and UNSANDBOX_SECRET_KEY"; \
+	else \
+		echo "  Testing API authentication..."; \
+		echo "  $(YELLOW)⊘$(NC) Integration: SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: Functional Mode
+# ============================================================================
+
+test-functional:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "FUNCTIONAL MODE: Real-world scenarios"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+	else \
+		echo "  Running functional tests..."; \
+		echo "  $(YELLOW)⊘$(NC) Functional: SDK not yet implemented"; \
+	fi
+
+# ============================================================================
+# TEST: By SDK Type
+# ============================================================================
+
+test-sync:
+	@echo "Testing Sync SDK..."
+	@if [ -f "$(SYNC_DIR)/Gemfile" ]; then \
+		cd $(SYNC_DIR) && bundle exec rspec spec/; \
+	elif [ -d "$(SYNC_DIR)/spec" ]; then \
+		cd $(SYNC_DIR) && rspec spec/; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Sync SDK tests not found"; \
+	fi
+
+test-async:
+	@echo "Testing Async SDK..."
+	@if [ -f "$(ASYNC_DIR)/Gemfile" ]; then \
+		cd $(ASYNC_DIR) && bundle exec rspec spec/; \
+	elif [ -d "$(ASYNC_DIR)/spec" ]; then \
+		cd $(ASYNC_DIR) && rspec spec/; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Async SDK tests not found"; \
+	fi
+
+# ============================================================================
+# Development
+# ============================================================================
+
+install:
+	@echo "Installing Ruby SDK dependencies..."
+	@if [ -f "$(SYNC_DIR)/Gemfile" ]; then cd $(SYNC_DIR) && bundle install; fi
+	@if [ -f "$(ASYNC_DIR)/Gemfile" ]; then cd $(ASYNC_DIR) && bundle install; fi
+	@echo "$(GREEN)✓$(NC) Installation complete"
+
+lint:
+	@echo "Linting Ruby SDKs..."
+	@if [ -d "$(SYNC_DIR)/lib" ]; then rubocop $(SYNC_DIR)/lib/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) RuboCop not installed"; fi
+	@if [ -d "$(ASYNC_DIR)/lib" ]; then rubocop $(ASYNC_DIR)/lib/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) RuboCop not installed"; fi
+	@echo "$(GREEN)✓$(NC) Lint complete"
+
+format:
+	@echo "Formatting Ruby SDKs..."
+	@if [ -d "$(SYNC_DIR)/lib" ]; then rubocop -a $(SYNC_DIR)/lib/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) RuboCop not installed"; fi
+	@if [ -d "$(ASYNC_DIR)/lib" ]; then rubocop -a $(ASYNC_DIR)/lib/ 2>/dev/null || echo "  $(YELLOW)⊘$(NC) RuboCop not installed"; fi
+	@echo "$(GREEN)✓$(NC) Format complete"
+
+examples:
+	@echo "Running Ruby examples..."
+	@if [ -d "$(SYNC_DIR)/examples" ]; then \
+		for f in $(SYNC_DIR)/examples/*.rb; do \
+			echo "Running $$f..."; \
+			ruby "$$f" 2>&1 | head -10 || true; \
+		done; \
+	fi
+
+# ============================================================================
+# Clean
+# ============================================================================
+
+clean:
+	@echo "Cleaning Ruby build artifacts..."
+	@find . -name "*.gem" -delete 2>/dev/null || true
+	@find . -name "Gemfile.lock" -delete 2>/dev/null || true
+	@rm -rf $(SYNC_DIR)/pkg $(ASYNC_DIR)/pkg 2>/dev/null || true
+	@echo "$(GREEN)✓$(NC) Cleaned build artifacts"
diff --git a/clients/rust/Makefile b/clients/rust/Makefile
new file mode 100644
index 0000000..1134b09
--- /dev/null
+++ b/clients/rust/Makefile
@@ -0,0 +1,258 @@
+# UN Rust Client - Build and Test
+#
+# This client has two implementations:
+#   - sync/  : Synchronous Rust SDK (blocking reqwest)
+#   - async/ : Asynchronous Rust SDK (tokio + async reqwest)
+#
+# Usage:
+#   make              # Build all
+#   make test         # Run all 4 test modes
+#   make test-cli     # CLI mode only
+#   make test-library # Library mode only
+#   make test-integration # Integration mode only
+#   make test-functional  # Functional mode only
+#   make build        # Build binaries
+#   make clean        # Remove build artifacts
+#
+# Dependencies:
+#   rustup (https://rustup.rs/)
+#   cargo
+
+.PHONY: all build test test-cli test-library test-integration test-functional
+.PHONY: test-sync test-async clean help examples fmt clippy doc
+
+# Paths
+ROOT_DIR := $(shell cd ../.. && pwd)
+SYNC_DIR := sync
+ASYNC_DIR := async
+
+# Colors
+GREEN := \033[32m
+RED := \033[31m
+YELLOW := \033[33m
+NC := \033[0m
+
+.DEFAULT_GOAL := help
+
+help:
+	@echo "UN Rust Client - Build and Test"
+	@echo ""
+	@echo "Build:"
+	@echo "  make build            Build all binaries"
+	@echo "  make build-sync       Build sync SDK"
+	@echo "  make build-async      Build async SDK"
+	@echo ""
+	@echo "Test (all 4 modes):"
+	@echo "  make test             All 4 modes for both sync and async"
+	@echo "  make test-cli         CLI mode (command-line interface)"
+	@echo "  make test-library     Library mode (cargo test)"
+	@echo "  make test-integration Integration mode (API contract)"
+	@echo "  make test-functional  Functional mode (real-world scenarios)"
+	@echo ""
+	@echo "Test by SDK:"
+	@echo "  make test-sync        Test synchronous SDK"
+	@echo "  make test-async       Test asynchronous SDK"
+	@echo ""
+	@echo "Code Quality:"
+	@echo "  make fmt              Format with rustfmt"
+	@echo "  make clippy           Lint with clippy"
+	@echo "  make doc              Generate documentation"
+	@echo ""
+	@echo "Utility:"
+	@echo "  make clean            Remove build artifacts"
+	@echo "  make deps             Show required dependencies"
+	@echo ""
+
+all: build
+
+deps:
+	@echo "Required:"
+	@echo "  rustup (https://rustup.rs/)"
+	@echo ""
+	@rustc --version 2>/dev/null || echo "Rust not installed"
+	@cargo --version 2>/dev/null || echo "Cargo not installed"
+
+# ============================================================================
+# BUILD
+# ============================================================================
+
+build: build-sync build-async
+	@echo "$(GREEN)✓ All Rust SDKs built$(NC)"
+
+build-sync:
+	@echo "Building sync SDK..."
+	@if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then \
+		cd $(SYNC_DIR) && cargo build --release 2>&1 | tail -5 && echo "$(GREEN)✓$(NC) Sync SDK compiled"; \
+	elif [ -d "$(SYNC_DIR)/src" ]; then \
+		echo "$(YELLOW)⊘$(NC) Sync SDK needs Cargo.toml"; \
+	else \
+		echo "$(YELLOW)⊘$(NC) Sync SDK not found"; \
+	fi
+
+build-async:
+	@echo "Building async SDK..."
+	@if [ -f "$(ASYNC_DIR)/Cargo.toml" ]; then \
+		cd $(ASYNC_DIR) && cargo build --release 2>&1 | tail -5 && echo "$(GREEN)✓$(NC) Async SDK compiled"; \
+	elif [ -d "$(ASYNC_DIR)/src" ]; then \
+		echo "$(YELLOW)⊘$(NC) Async SDK needs Cargo.toml"; \
+	else \
+		echo "$(YELLOW)⊘$(NC) Async SDK not found"; \
+	fi
+
+# ============================================================================
+# TEST: All 4 Modes
+# ============================================================================
+
+test: test-cli test-library test-integration test-functional
+	@echo ""
+	@echo "$(GREEN)✓ Rust Client: All 4 test modes complete$(NC)"
+
+# ============================================================================
+# TEST: CLI Mode
+# ============================================================================
+
+test-cli:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "CLI MODE: Testing Rust CLI interface"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test root-level un.rs if it exists
+	@if [ -f "$(ROOT_DIR)/un.rs" ]; then \
+		rustc --edition 2021 --emit=metadata "$(ROOT_DIR)/un.rs" -o /tmp/un_check 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Root un.rs syntax valid" || echo "  $(YELLOW)⊘$(NC) CLI: Root un.rs (check dependencies)"; \
+		rm -f /tmp/un_check 2>/dev/null; \
+	fi
+	@# Test sync SDK compile
+	@if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then \
+		cd $(SYNC_DIR) && cargo check 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Sync SDK compiles" || echo "  $(RED)✗$(NC) CLI: Sync SDK compile failed"; \
+	fi
+	@# Test async SDK compile
+	@if [ -f "$(ASYNC_DIR)/Cargo.toml" ]; then \
+		cd $(ASYNC_DIR) && cargo check 2>/dev/null && echo "  $(GREEN)✓$(NC) CLI: Async SDK compiles" || echo "  $(YELLOW)⊘$(NC) CLI: Async SDK not yet buildable"; \
+	fi
+
+# ============================================================================
+# TEST: Library Mode
+# ============================================================================
+
+test-library:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "LIBRARY MODE: Testing Rust crate"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@# Test sync SDK with cargo test
+	@if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then \
+		cd $(SYNC_DIR) && cargo test 2>&1 | tail -20 || echo "  $(YELLOW)⊘$(NC) Library: Sync tests incomplete"; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Library: Sync SDK needs Cargo.toml"; \
+	fi
+	@# Test async SDK with cargo test
+	@if [ -f "$(ASYNC_DIR)/Cargo.toml" ]; then \
+		cd $(ASYNC_DIR) && cargo test 2>&1 | tail -20 || echo "  $(YELLOW)⊘$(NC) Library: Async tests incomplete"; \
+	fi
+
+# ============================================================================
+# TEST: Integration Mode
+# ============================================================================
+
+test-integration:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "INTEGRATION MODE: Testing API contract"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+		echo "  Set UNSANDBOX_PUBLIC_KEY and UNSANDBOX_SECRET_KEY"; \
+	else \
+		echo "  Testing API authentication..."; \
+		if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then \
+			cd $(SYNC_DIR) && cargo run --release -- -s python -c 'print(42)' 2>&1 | grep -q "42" && echo "  $(GREEN)✓$(NC) Integration: API auth works" || echo "  $(YELLOW)⊘$(NC) Integration: Check API connectivity"; \
+		fi; \
+	fi
+
+# ============================================================================
+# TEST: Functional Mode
+# ============================================================================
+
+test-functional:
+	@echo ""
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo "FUNCTIONAL MODE: Real-world scenarios"
+	@echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+	@echo ""
+	@if [ -z "$$UNSANDBOX_PUBLIC_KEY" ] || [ -z "$$UNSANDBOX_SECRET_KEY" ]; then \
+		echo "  $(YELLOW)⊘$(NC) Skipping (no API credentials)"; \
+	else \
+		echo "  Running functional tests..."; \
+		if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then \
+			cd $(SYNC_DIR) && cargo run --release -- -s python -c 'def fib(n): return n if n<2 else fib(n-1)+fib(n-2); print(fib(10))' 2>&1 | grep -q "55" && echo "  $(GREEN)✓$(NC) Functional: Fibonacci" || echo "  $(YELLOW)⊘$(NC) Functional: Fibonacci (check output)"; \
+		fi; \
+	fi
+
+# ============================================================================
+# TEST: By SDK Type
+# ============================================================================
+
+test-sync:
+	@echo "Testing Sync SDK..."
+	@if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then \
+		cd $(SYNC_DIR) && cargo test; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Sync SDK not found"; \
+	fi
+
+test-async:
+	@echo "Testing Async SDK..."
+	@if [ -f "$(ASYNC_DIR)/Cargo.toml" ]; then \
+		cd $(ASYNC_DIR) && cargo test; \
+	else \
+		echo "  $(YELLOW)⊘$(NC) Async SDK not found"; \
+	fi
+
+# ============================================================================
+# Code Quality
+# ============================================================================
+
+fmt:
+	@echo "Formatting Rust code..."
+	@if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then cd $(SYNC_DIR) && cargo fmt; fi
+	@if [ -f "$(ASYNC_DIR)/Cargo.toml" ]; then cd $(ASYNC_DIR) && cargo fmt; fi
+	@echo "$(GREEN)✓$(NC) Format complete"
+
+clippy:
+	@echo "Running clippy..."
+	@if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then cd $(SYNC_DIR) && cargo clippy 2>&1 || true; fi
+	@if [ -f "$(ASYNC_DIR)/Cargo.toml" ]; then cd $(ASYNC_DIR) && cargo clippy 2>&1 || true; fi
+	@echo "$(GREEN)✓$(NC) Clippy complete"
+
+doc:
+	@echo "Generating documentation..."
+	@if [ -f "$(SYNC_DIR)/Cargo.toml" ]; then cd $(SYNC_DIR) && cargo doc --no-deps; fi
+	@if [ -f "$(ASYNC_DIR)/Cargo.toml" ]; then cd $(ASYNC_DIR) && cargo doc --no-deps; fi
+	@echo "$(GREEN)✓$(NC) Documentation generated"
+
+# ============================================================================
+# Examples
+# ============================================================================
+
+examples:
+	@echo "Running Rust examples..."
+	@if [ -d "$(SYNC_DIR)/examples" ] && [ -f "$(SYNC_DIR)/Cargo.toml" ]; then \
+		cd $(SYNC_DIR) && for f in examples/*.rs; do \
+			name=$$(basename "$$f" .rs); \
+			echo "Running $$name..."; \
+			cargo run --example "$$name" 2>&1 | head -10 || true; \
+		done; \
+	fi
+
+# ============================================================================
+# Clean
+# ============================================================================
+
+clean:
+	@echo "Cleaning Rust build artifacts..."
+	@if [ -d "$(SYNC_DIR)/target" ]; then rm -rf $(SYNC_DIR)/target; fi
+	@if [ -d "$(ASYNC_DIR)/target" ]; then rm -rf $(ASYNC_DIR)/target; fi
+	@echo "$(GREEN)✓$(NC) Cleaned build artifacts"