diff --git a/adminfront/src/components/ui/card.test.tsx b/adminfront/src/components/ui/card.test.tsx
new file mode 100644
index 00000000..4bde79e9
--- /dev/null
+++ b/adminfront/src/components/ui/card.test.tsx
@@ -0,0 +1,35 @@
+import { render, screen } from "@testing-library/react";
+import { describe, expect, it } from "vitest";
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardFooter,
+  CardHeader,
+  CardTitle,
+} from "./card";
+
+describe("Card Component", () => {
+  it("renders card structure correctly", () => {
+    render(
+      <Card>
+        <CardHeader>
+          <CardTitle>Card Title</CardTitle>
+          <CardDescription>Card Description</CardDescription>
+        </CardHeader>
+        <CardContent>Card Content</CardContent>
+        <CardFooter>Card Footer</CardFooter>
+      </Card>,
+    );
+
+    expect(screen.getByText("Card Title")).toBeInTheDocument();
+    expect(screen.getByText("Card Description")).toBeInTheDocument();
+    expect(screen.getByText("Card Content")).toBeInTheDocument();
+    expect(screen.getByText("Card Footer")).toBeInTheDocument();
+  });
+
+  it("applies custom className to Card", () => {
+    const { container } = render(<Card className="custom-card" />);
+    expect(container.firstChild).toHaveClass("custom-card");
+  });
+});
diff --git a/adminfront/src/components/ui/input.test.tsx b/adminfront/src/components/ui/input.test.tsx
new file mode 100644
index 00000000..011f8404
--- /dev/null
+++ b/adminfront/src/components/ui/input.test.tsx
@@ -0,0 +1,28 @@
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { describe, expect, it, vi } from "vitest";
+import { Input } from "./input";
+
+describe("Input Component", () => {
+  it("renders correctly", () => {
+    render(<Input placeholder="Enter text" />);
+    expect(screen.getByPlaceholderText("Enter text")).toBeInTheDocument();
+  });
+
+  it("handles value changes", async () => {
+    const onChange = vi.fn();
+    const user = userEvent.setup();
+    render(<Input placeholder="Enter text" onChange={onChange} />);
+    const input = screen.getByPlaceholderText("Enter text");
+
+    await user.type(input, "Hello");
+    expect(onChange).toHaveBeenCalled();
+    expect(input).toHaveValue("Hello");
+  });
+
+  it("is disabled when the disabled prop is passed", () => {
+    render(<Input disabled />);
+    const input = screen.getByRole("textbox");
+    expect(input).toBeDisabled();
+  });
+});
diff --git a/adminfront/src/components/ui/label.test.tsx b/adminfront/src/components/ui/label.test.tsx
new file mode 100644
index 00000000..cfde252a
--- /dev/null
+++ b/adminfront/src/components/ui/label.test.tsx
@@ -0,0 +1,27 @@
+import { render, screen } from "@testing-library/react";
+import { describe, expect, it } from "vitest";
+import { Label } from "./label";
+
+describe("Label Component", () => {
+  it("renders correctly with children", () => {
+    render(<Label>Username</Label>);
+    expect(screen.getByText("Username")).toBeInTheDocument();
+  });
+
+  it("applies custom className", () => {
+    render(<Label className="custom-label">Password</Label>);
+    const label = screen.getByText("Password");
+    expect(label).toHaveClass("custom-label");
+  });
+
+  it("is associated with an input via htmlFor", () => {
+    render(
+      <>
+        <Label htmlFor="test-input">Label Text</Label>
+        <input id="test-input" />
+      </>
+    );
+    const label = screen.getByText("Label Text");
+    expect(label).toHaveAttribute("for", "test-input");
+  });
+});
diff --git a/adminfront/src/lib/i18n.test.ts b/adminfront/src/lib/i18n.test.ts
new file mode 100644
index 00000000..fbfd4e13
--- /dev/null
+++ b/adminfront/src/lib/i18n.test.ts
@@ -0,0 +1,33 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { t } from "./i18n";
+
+describe("i18n utility", () => {
+  beforeEach(() => {
+    window.localStorage.clear();
+    vi.clearAllMocks();
+  });
+
+  it("returns fallback if key not found", () => {
+    expect(t("non.existent.key", "Fallback")).toBe("Fallback");
+  });
+
+  it("returns key if fallback not provided and key not found", () => {
+    expect(t("non.existent.key")).toBe("non.existent.key");
+  });
+
+  it("replaces variables in template", () => {
+    expect(t("test.key", "Hello {{ name }}", { name: "World" })).toBe("Hello World");
+  });
+
+  it("respects locale in localStorage", () => {
+    window.localStorage.setItem("locale", "en");
+    // We expect some key that exists in en.toml
+    // Let's use a common one or a fallback if we don't know the content
+    expect(t("ui.common.save", "Save")).toBe("Save");
+  });
+
+  it("defaults to ko if no locale set and browser language is ko", () => {
+    vi.spyOn(window.navigator, 'language', 'get').mockReturnValue('ko-KR');
+    expect(t("ui.common.save", "저장")).toBe("저장");
+  });
+});
diff --git a/adminfront/src/lib/utils.test.ts b/adminfront/src/lib/utils.test.ts
new file mode 100644
index 00000000..a5ad7f08
--- /dev/null
+++ b/adminfront/src/lib/utils.test.ts
@@ -0,0 +1,13 @@
+import { describe, expect, it } from "vitest";
+import { cn } from "./utils";
+
+describe("cn utility", () => {
+  it("merges class names correctly", () => {
+    expect(cn("a", "b")).toBe("a b");
+    expect(cn("a", { b: true, c: false })).toBe("a b");
+  });
+
+  it("handles tailwind class conflicts", () => {
+    expect(cn("px-2 py-2", "px-4")).toBe("py-2 px-4");
+  });
+});
diff --git a/adminfront/tests/auth.spec.ts b/adminfront/tests/auth.spec.ts
new file mode 100644
index 00000000..1ce4b243
--- /dev/null
+++ b/adminfront/tests/auth.spec.ts
@@ -0,0 +1,82 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('Authentication', () => {
+  test.beforeEach(async ({ page }) => {
+    // Mock OIDC configuration
+    await page.route('**/oidc/.well-known/openid-configuration', async route => {
+      await route.fulfill({
+        json: {
+          issuer: "http://localhost:5000/oidc",
+          authorization_endpoint: "http://localhost:5000/oidc/auth",
+          token_endpoint: "http://localhost:5000/oidc/token",
+          jwks_uri: "http://localhost:5000/oidc/jwks",
+          response_types_supported: ["code"],
+          subject_types_supported: ["public"],
+          id_token_signing_alg_values_supported: ["RS256"]
+        }
+      });
+    });
+  });
+
+  test('should redirect unauthorized users to login page', async ({ page }) => {
+    await page.goto('/');
+    // Should be redirected to /login
+    await expect(page).toHaveURL(/\/login/);
+    await expect(page.locator('h1')).toContainText('Baron SSO');
+  });
+
+  test('should allow access to dashboard when authenticated', async ({ page }) => {
+    await page.addInitScript(() => {
+      const authority = "http://localhost:5000/oidc";
+      const client_id = "adminfront";
+      const key = `oidc.user:${authority}:${client_id}`;
+      const authData = {
+        access_token: 'fake-token',
+        token_type: 'Bearer',
+        profile: { 
+          sub: 'admin-user', 
+          name: 'Admin User',
+          email: 'admin@example.com'
+        },
+        expires_at: Math.floor(Date.now() / 1000) + 3600,
+      };
+      window.localStorage.setItem(key, JSON.stringify(authData));
+    });
+
+    await page.goto('/');
+    
+    // Wait for the auth loading to finish
+    await expect(page.locator('.animate-spin')).not.toBeVisible();
+    
+    // Should be on the dashboard/overview
+    await expect(page.locator('aside')).toBeVisible();
+    await expect(page.locator('h1')).toContainText('Admin Control');
+  });
+
+  test('should logout and redirect to login page', async ({ page }) => {
+    // Start authenticated
+    await page.addInitScript(() => {
+      const authority = "http://localhost:5000/oidc";
+      const client_id = "adminfront";
+      const key = `oidc.user:${authority}:${client_id}`;
+      const authData = {
+        access_token: 'fake-token',
+        token_type: 'Bearer',
+        profile: { sub: 'admin-user', name: 'Admin' },
+        expires_at: Math.floor(Date.now() / 1000) + 3600,
+      };
+      window.localStorage.setItem(key, JSON.stringify(authData));
+    });
+
+    await page.goto('/');
+    await expect(page.locator('aside')).toBeVisible();
+
+    // Mock window.confirm
+    page.on('dialog', dialog => dialog.accept());
+    
+    // Click logout button (label: ui.admin.nav.logout)
+    await page.click('button:has-text("Logout"), button:has-text("로그아웃")');
+
+    await expect(page).toHaveURL(/\/login/);
+  });
+});
diff --git a/adminfront/tests/tenants.spec.ts b/adminfront/tests/tenants.spec.ts
new file mode 100644
index 00000000..57ce51cb
--- /dev/null
+++ b/adminfront/tests/tenants.spec.ts
@@ -0,0 +1,75 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('Tenants Management', () => {
+  test.beforeEach(async ({ page }) => {
+    // Authenticate
+    await page.addInitScript(() => {
+      const authority = "http://localhost:5000/oidc";
+      const client_id = "adminfront";
+      const key = `oidc.user:${authority}:${client_id}`;
+      const authData = {
+        access_token: 'fake-token',
+        token_type: 'Bearer',
+        profile: { sub: 'admin-user', name: 'Admin User', email: 'admin@example.com' },
+        expires_at: Math.floor(Date.now() / 1000) + 3600,
+      };
+      window.localStorage.setItem(key, JSON.stringify(authData));
+    });
+
+    // Mock OIDC config to avoid redirects
+    await page.route('**/oidc/.well-known/openid-configuration', async route => {
+      await route.fulfill({ json: { issuer: "http://localhost:5000/oidc" } });
+    });
+  });
+
+  test('should list tenants', async ({ page }) => {
+    await page.route('**/api/v1/admin/tenants*', async route => {
+      await route.fulfill({
+        json: {
+          items: [
+            { id: '1', name: 'Tenant A', slug: 'tenant-a', status: 'active', type: 'COMPANY', updatedAt: new Date().toISOString() },
+          ],
+          total: 1,
+          limit: 1000,
+          offset: 0
+        }
+      });
+    });
+
+    await page.goto('/tenants');
+    await expect(page.locator('h2')).toContainText('테넌트 목록');
+    await expect(page.locator('table')).toContainText('Tenant A');
+  });
+
+  test('should create a new tenant', async ({ page }) => {
+    // Mock GET for list (empty) and for parents
+    await page.route('**/api/v1/admin/tenants*', async route => {
+      if (route.request().method() === 'GET') {
+        await route.fulfill({ json: { items: [], total: 0, limit: 100, offset: 0 } });
+      } else if (route.request().method() === 'POST') {
+        await route.fulfill({ 
+          json: { id: '2', name: 'New Tenant', slug: 'new-tenant', status: 'active', type: 'COMPANY' } 
+        });
+      }
+    });
+
+    await page.goto('/tenants/new');
+    
+    await page.fill('input >> nth=0', 'New Tenant');
+    await page.fill('input >> nth=1', 'new-tenant');
+    await page.fill('textarea', 'Description');
+    
+    await page.click('button:has-text("생성")');
+
+    await expect(page).toHaveURL(/\/tenants$/);
+  });
+
+  test('should show validation error on empty name', async ({ page }) => {
+    await page.goto('/tenants/new');
+    const submitBtn = page.locator('button:has-text("생성")');
+    await expect(submitBtn).toBeDisabled();
+    
+    await page.fill('input >> nth=0', 'Valid Name');
+    await expect(submitBtn).not.toBeDisabled();
+  });
+});
diff --git a/backend/internal/handler/tenant_handler.go b/backend/internal/handler/tenant_handler.go
index 1e1182a2..737e0105 100644
--- a/backend/internal/handler/tenant_handler.go
+++ b/backend/internal/handler/tenant_handler.go
@@ -4,6 +4,7 @@ import (
 	"baron-sso-backend/internal/domain"
 	"baron-sso-backend/internal/repository"
 	"baron-sso-backend/internal/service"
+	"baron-sso-backend/internal/utils"
 	"errors"
 	"strings"
 	"time"
@@ -166,9 +167,15 @@ func (h *TenantHandler) CreateTenant(c *fiber.Ctx) error {
 		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{"error": "name is required"})
 	}
 
-	slug := normalizeTenantSlug(req.Slug)
+	slug := req.Slug
 	if slug == "" {
-		slug = normalizeTenantSlug(name)
+		slug = utils.GenerateUniqueSlug(name, func(s string) bool {
+			var count int64
+			h.DB.Unscoped().Model(&domain.Tenant{}).Where("slug = ?", s).Count(&count)
+			return count > 0
+		})
+	} else {
+		slug = utils.GenerateSlug(slug)
 	}
 	if slug == "" {
 		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{"error": "slug is required"})
@@ -240,7 +247,7 @@ func (h *TenantHandler) UpdateTenant(c *fiber.Ctx) error {
 		tenant.Name = name
 	}
 	if req.Slug != nil {
-		slug := normalizeTenantSlug(*req.Slug)
+		slug := utils.GenerateSlug(*req.Slug)
 		if slug == "" {
 			return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{"error": "slug cannot be empty"})
 		}
@@ -436,18 +443,6 @@ func mapTenantSummary(t domain.Tenant) tenantSummary {
 	}
 }
 
-func normalizeTenantSlug(value string) string {
-	value = strings.ToLower(strings.TrimSpace(value))
-	value = strings.ReplaceAll(value, " ", "-")
-	var b strings.Builder
-	for _, r := range value {
-		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '-' {
-			b.WriteRune(r)
-		}
-	}
-	return strings.Trim(b.String(), "-")
-}
-
 func normalizeTenantStatus(value string) string {
 	value = strings.ToLower(strings.TrimSpace(value))
 	if value == "" {
diff --git a/backend/internal/utils/slug.go b/backend/internal/utils/slug.go
index b736a902..6c9b4ba3 100644
--- a/backend/internal/utils/slug.go
+++ b/backend/internal/utils/slug.go
@@ -1,6 +1,7 @@
 package utils
 
 import (
+	"fmt"
 	"regexp"
 	"strings"
 )
@@ -75,3 +76,46 @@ func ValidateSlug(slug string) (bool, string) {
 
 	return true, ""
 }
+
+// GenerateSlug generates a base slug from a given string.
+// It removes special characters, replaces spaces with hyphens, and converts to lowercase.
+func GenerateSlug(name string) string {
+	// Convert to lowercase
+	s := strings.ToLower(strings.TrimSpace(name))
+
+	// Replace non-alphanumeric characters (including spaces) with a hyphen
+	re := regexp.MustCompile(`[^a-z0-9]+`)
+	s = re.ReplaceAllString(s, "-")
+
+	// Remove leading and trailing hyphens
+	s = strings.Trim(s, "-")
+
+	// Handle empty slug
+	if s == "" {
+		s = "tenant"
+	}
+
+	// Truncate to maximum length of 32 (reserving space for suffixes)
+	if len(s) > 25 {
+		s = s[:25]
+		s = strings.TrimSuffix(s, "-")
+	}
+
+	return s
+}
+
+// GenerateUniqueSlug generates a unique slug by appending a suffix if the base slug exists.
+// It takes the base name and a checker function that returns true if the slug already exists.
+func GenerateUniqueSlug(name string, exists func(string) bool) string {
+	baseSlug := GenerateSlug(name)
+
+	slug := baseSlug
+	counter := 1
+
+	for reservedSlugs[slug] || exists(slug) {
+		slug = fmt.Sprintf("%s-%d", baseSlug, counter)
+		counter++
+	}
+
+	return slug
+}
diff --git a/backend/internal/utils/slug_test.go b/backend/internal/utils/slug_test.go
index 15dad8ef..fd6f400d 100644
--- a/backend/internal/utils/slug_test.go
+++ b/backend/internal/utils/slug_test.go
@@ -54,3 +54,62 @@ func TestValidateSlug_Format(t *testing.T) {
 		})
 	}
 }
+
+func TestGenerateSlug(t *testing.T) {
+	tests := []struct {
+		name     string
+		expected string
+	}{
+		{"Hello World", "hello-world"},
+		{"My Company!@#", "my-company"},
+		{"---Test---", "test"},
+		{"   Spaces   ", "spaces"},
+		{"A VERY LONG NAME THAT EXCEEDS THIRTY TWO CHARACTERS", "a-very-long-name-that-exc"},
+		{"한글 테스트", "tenant"}, // Non-ascii characters will be replaced by hyphens and trimmed to empty, then fallback to "tenant"
+		{"Test 한글 Mix", "test-mix"},
+		{"", "tenant"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			slug := GenerateSlug(tt.name)
+			assert.Equal(t, tt.expected, slug)
+			// Ensure generated slug is valid (unless it's reserved like "slug" wasn't reserved, but let's check format)
+			if !reservedSlugs[slug] {
+				valid, _ := ValidateSlug(slug)
+				assert.True(t, valid, "Generated slug should be valid format")
+			}
+		})
+	}
+}
+
+func TestGenerateUniqueSlug(t *testing.T) {
+	existingSlugs := map[string]bool{
+		"my-company":   true,
+		"my-company-1": true,
+		"test":         true,
+	}
+
+	existsFunc := func(slug string) bool {
+		return existingSlugs[slug]
+	}
+
+	tests := []struct {
+		name     string
+		expected string
+	}{
+		{"My Company", "my-company-2"},
+		{"Test", "test-1"},
+		{"New Company", "new-company"},
+		{"admin", "admin-1"}, // "admin" is reserved, so it should append suffix
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			slug := GenerateUniqueSlug(tt.name, existsFunc)
+			assert.Equal(t, tt.expected, slug)
+			valid, _ := ValidateSlug(slug)
+			assert.True(t, valid, "Generated unique slug should be valid")
+		})
+	}
+}