diff --git a/packages/shared-auth-stores/package.json b/packages/shared-auth-stores/package.json
new file mode 100644
index 000000000..831387c60
--- /dev/null
+++ b/packages/shared-auth-stores/package.json
@@ -0,0 +1,32 @@
+{
+  "name": "@manacore/shared-auth-stores",
+  "version": "0.0.1",
+  "type": "module",
+  "exports": {
+    ".": {
+      "types": "./src/index.ts",
+      "svelte": "./src/index.ts",
+      "default": "./src/index.ts"
+    }
+  },
+  "main": "./src/index.ts",
+  "types": "./src/index.ts",
+  "svelte": "./src/index.ts",
+  "files": [
+    "src"
+  ],
+  "scripts": {
+    "type-check": "svelte-check --tsconfig ./tsconfig.json"
+  },
+  "peerDependencies": {
+    "svelte": "^5.0.0"
+  },
+  "devDependencies": {
+    "svelte": "^5.0.0",
+    "svelte-check": "^4.0.0",
+    "typescript": "^5.0.0"
+  },
+  "dependencies": {
+    "@manacore/shared-types": "workspace:*"
+  }
+}
diff --git a/packages/shared-auth-stores/src/createAuthStore.svelte.ts b/packages/shared-auth-stores/src/createAuthStore.svelte.ts
new file mode 100644
index 000000000..ea8633bc5
--- /dev/null
+++ b/packages/shared-auth-stores/src/createAuthStore.svelte.ts
@@ -0,0 +1,186 @@
+/**
+ * Svelte 5 Auth Store Factory
+ *
+ * Creates a reactive auth store using Svelte 5 runes.
+ * Generic over user type to support app-specific user models.
+ *
+ * @example
+ * ```ts
+ * // In your app's auth store file
+ * import { createAuthStore } from '@manacore/shared-auth-stores';
+ * import { authService } from '$lib/auth';
+ * import type { AppUser } from '$lib/types';
+ *
+ * export const authStore = createAuthStore<AppUser>(authService);
+ * ```
+ */
+
+import type { AuthServiceAdapter, AuthResult, BaseUser } from './types';
+
+/**
+ * Create a Svelte 5 runes-based auth store
+ *
+ * @param authService - Auth service adapter implementing the AuthServiceAdapter interface
+ * @returns Reactive auth store with state and actions
+ */
+export function createAuthStore<TUser extends BaseUser>(authService: AuthServiceAdapter<TUser>) {
+	// Reactive state using Svelte 5 runes
+	let user = $state<TUser | null>(null);
+	let loading = $state(true);
+	let error = $state<string | null>(null);
+
+	return {
+		// Reactive getters
+		get user() {
+			return user;
+		},
+		get loading() {
+			return loading;
+		},
+		get error() {
+			return error;
+		},
+		get isAuthenticated() {
+			return !!user;
+		},
+
+		/**
+		 * Initialize auth state from stored tokens/session
+		 */
+		async initialize() {
+			loading = true;
+			error = null;
+			try {
+				const isAuth = await authService.isAuthenticated();
+				if (isAuth) {
+					user = await authService.getUserFromToken();
+				} else {
+					user = null;
+				}
+			} catch (e) {
+				console.error('Failed to initialize auth:', e);
+				error = e instanceof Error ? e.message : 'Failed to initialize authentication';
+				user = null;
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Set user manually (useful for SSR hydration)
+		 */
+		setUser(newUser: TUser | null) {
+			user = newUser;
+			error = null;
+		},
+
+		/**
+		 * Sign in with email and password
+		 */
+		async signIn(email: string, password: string): Promise<AuthResult<TUser>> {
+			loading = true;
+			error = null;
+			try {
+				const result = await authService.signIn(email, password);
+				if (result.success) {
+					user = await authService.getUserFromToken();
+				} else {
+					error = result.error || 'Sign in failed';
+				}
+				return result;
+			} catch (e) {
+				const errorMessage = e instanceof Error ? e.message : 'Sign in failed';
+				error = errorMessage;
+				return { success: false, error: errorMessage };
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Sign up with email and password
+		 */
+		async signUp(email: string, password: string): Promise<AuthResult<TUser>> {
+			loading = true;
+			error = null;
+			try {
+				const result = await authService.signUp(email, password);
+				if (result.success && !result.needsVerification) {
+					user = await authService.getUserFromToken();
+				} else if (!result.success) {
+					error = result.error || 'Sign up failed';
+				}
+				return result;
+			} catch (e) {
+				const errorMessage = e instanceof Error ? e.message : 'Sign up failed';
+				error = errorMessage;
+				return { success: false, error: errorMessage };
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Send password reset email
+		 */
+		async forgotPassword(email: string): Promise<{ success: boolean; error?: string }> {
+			loading = true;
+			error = null;
+			try {
+				const result = await authService.forgotPassword(email);
+				if (!result.success) {
+					error = result.error || 'Password reset failed';
+				}
+				return result;
+			} catch (e) {
+				const errorMessage = e instanceof Error ? e.message : 'Password reset failed';
+				error = errorMessage;
+				return { success: false, error: errorMessage };
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Sign out user
+		 */
+		async signOut() {
+			loading = true;
+			error = null;
+			try {
+				await authService.signOut();
+				user = null;
+			} catch (e) {
+				console.error('Sign out failed:', e);
+				error = e instanceof Error ? e.message : 'Sign out failed';
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Check authentication status
+		 */
+		async checkAuth(): Promise<boolean> {
+			try {
+				const isAuth = await authService.isAuthenticated();
+				if (!isAuth) {
+					user = null;
+					return false;
+				}
+				return true;
+			} catch (e) {
+				console.error('Auth check failed:', e);
+				user = null;
+				return false;
+			}
+		},
+
+		/**
+		 * Clear error state
+		 */
+		clearError() {
+			error = null;
+		}
+	};
+}
diff --git a/packages/shared-auth-stores/src/createSupabaseAuthStore.svelte.ts b/packages/shared-auth-stores/src/createSupabaseAuthStore.svelte.ts
new file mode 100644
index 000000000..f972ba205
--- /dev/null
+++ b/packages/shared-auth-stores/src/createSupabaseAuthStore.svelte.ts
@@ -0,0 +1,271 @@
+/**
+ * Supabase Auth Store Factory
+ *
+ * Creates a reactive auth store that works directly with Supabase client.
+ * Useful for apps that use Supabase directly without middleware.
+ *
+ * @example
+ * ```ts
+ * import { createSupabaseAuthStore } from '@manacore/shared-auth-stores';
+ * import { createBrowserClient } from '@supabase/ssr';
+ *
+ * const supabase = createBrowserClient(url, key);
+ * export const authStore = createSupabaseAuthStore(supabase);
+ * ```
+ */
+
+import type { BaseUser, AuthResult } from './types';
+
+/**
+ * Minimal Supabase client interface
+ * Only requires the auth methods we use
+ */
+interface SupabaseClientLike {
+	auth: {
+		getSession(): Promise<{ data: { session: { user: { id: string; email?: string } } | null } }>;
+		signInWithPassword(credentials: {
+			email: string;
+			password: string;
+		}): Promise<{ error: { message: string } | null }>;
+		signUp(credentials: {
+			email: string;
+			password: string;
+		}): Promise<{ data: { session: unknown }; error: { message: string } | null }>;
+		resetPasswordForEmail(
+			email: string,
+			options?: { redirectTo?: string }
+		): Promise<{ error: { message: string } | null }>;
+		signOut(): Promise<{ error: { message: string } | null }>;
+	};
+}
+
+/**
+ * Options for creating a Supabase auth store
+ */
+export interface CreateSupabaseAuthStoreOptions {
+	/** URL to redirect to after password reset */
+	passwordResetRedirectUrl?: string;
+}
+
+/**
+ * Default user type for Supabase auth
+ */
+export interface SupabaseUser extends BaseUser {
+	id: string;
+	email: string;
+}
+
+/**
+ * Create a Svelte 5 runes-based auth store for Supabase
+ *
+ * @param getSupabaseClient - Function that returns a Supabase client
+ * @param options - Configuration options
+ * @returns Reactive auth store with state and actions
+ */
+export function createSupabaseAuthStore(
+	getSupabaseClient: () => SupabaseClientLike,
+	options: CreateSupabaseAuthStoreOptions = {}
+) {
+	// Reactive state using Svelte 5 runes
+	let user = $state<SupabaseUser | null>(null);
+	let loading = $state(true);
+	let error = $state<string | null>(null);
+
+	/**
+	 * Get user from current session
+	 */
+	async function getUserFromSession(): Promise<SupabaseUser | null> {
+		const supabase = getSupabaseClient();
+		const {
+			data: { session }
+		} = await supabase.auth.getSession();
+		if (!session?.user) return null;
+		return {
+			id: session.user.id,
+			email: session.user.email || ''
+		};
+	}
+
+	return {
+		// Reactive getters
+		get user() {
+			return user;
+		},
+		get loading() {
+			return loading;
+		},
+		get error() {
+			return error;
+		},
+		get isAuthenticated() {
+			return !!user;
+		},
+
+		/**
+		 * Initialize auth state from Supabase session
+		 */
+		async initialize() {
+			loading = true;
+			error = null;
+			try {
+				user = await getUserFromSession();
+			} catch (e) {
+				console.error('Failed to initialize auth:', e);
+				error = e instanceof Error ? e.message : 'Failed to initialize authentication';
+				user = null;
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Set user manually
+		 */
+		setUser(newUser: SupabaseUser | null) {
+			user = newUser;
+			error = null;
+		},
+
+		/**
+		 * Sign in with email and password
+		 */
+		async signIn(email: string, password: string): Promise<AuthResult<SupabaseUser>> {
+			loading = true;
+			error = null;
+			try {
+				const supabase = getSupabaseClient();
+				const { error: authError } = await supabase.auth.signInWithPassword({
+					email,
+					password
+				});
+
+				if (authError) {
+					error = authError.message;
+					return { success: false, error: authError.message };
+				}
+
+				user = await getUserFromSession();
+				return { success: true, user: user || undefined };
+			} catch (e) {
+				const errorMessage = e instanceof Error ? e.message : 'Sign in failed';
+				error = errorMessage;
+				return { success: false, error: errorMessage };
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Sign up with email and password
+		 */
+		async signUp(email: string, password: string): Promise<AuthResult<SupabaseUser>> {
+			loading = true;
+			error = null;
+			try {
+				const supabase = getSupabaseClient();
+				const { data, error: authError } = await supabase.auth.signUp({
+					email,
+					password
+				});
+
+				if (authError) {
+					error = authError.message;
+					return { success: false, error: authError.message };
+				}
+
+				// Check if email confirmation is required
+				const needsVerification = !data.session;
+
+				if (!needsVerification) {
+					user = await getUserFromSession();
+				}
+
+				return {
+					success: true,
+					needsVerification,
+					user: user || undefined
+				};
+			} catch (e) {
+				const errorMessage = e instanceof Error ? e.message : 'Sign up failed';
+				error = errorMessage;
+				return { success: false, error: errorMessage };
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Send password reset email
+		 */
+		async forgotPassword(email: string): Promise<{ success: boolean; error?: string }> {
+			loading = true;
+			error = null;
+			try {
+				const supabase = getSupabaseClient();
+				const redirectTo =
+					options.passwordResetRedirectUrl || `${window.location.origin}/reset-password`;
+
+				const { error: authError } = await supabase.auth.resetPasswordForEmail(email, {
+					redirectTo
+				});
+
+				if (authError) {
+					error = authError.message;
+					return { success: false, error: authError.message };
+				}
+
+				return { success: true };
+			} catch (e) {
+				const errorMessage = e instanceof Error ? e.message : 'Password reset failed';
+				error = errorMessage;
+				return { success: false, error: errorMessage };
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Sign out user
+		 */
+		async signOut() {
+			loading = true;
+			error = null;
+			try {
+				const supabase = getSupabaseClient();
+				await supabase.auth.signOut();
+				user = null;
+			} catch (e) {
+				console.error('Sign out failed:', e);
+				error = e instanceof Error ? e.message : 'Sign out failed';
+			} finally {
+				loading = false;
+			}
+		},
+
+		/**
+		 * Check authentication status
+		 */
+		async checkAuth(): Promise<boolean> {
+			try {
+				const sessionUser = await getUserFromSession();
+				if (!sessionUser) {
+					user = null;
+					return false;
+				}
+				user = sessionUser;
+				return true;
+			} catch (e) {
+				console.error('Auth check failed:', e);
+				user = null;
+				return false;
+			}
+		},
+
+		/**
+		 * Clear error state
+		 */
+		clearError() {
+			error = null;
+		}
+	};
+}
diff --git a/packages/shared-auth-stores/src/index.ts b/packages/shared-auth-stores/src/index.ts
new file mode 100644
index 000000000..380de57ad
--- /dev/null
+++ b/packages/shared-auth-stores/src/index.ts
@@ -0,0 +1,42 @@
+/**
+ * @manacore/shared-auth-stores
+ *
+ * Svelte 5 auth store factories for the ManaCore monorepo.
+ *
+ * Provides two approaches:
+ * 1. createAuthStore - Generic factory that works with any auth service adapter
+ * 2. createSupabaseAuthStore - Direct Supabase integration for simpler setups
+ *
+ * @example Generic auth store with custom adapter
+ * ```ts
+ * import { createAuthStore } from '@manacore/shared-auth-stores';
+ * import { authService } from '$lib/auth';
+ * import type { AppUser } from '$lib/types';
+ *
+ * export const authStore = createAuthStore<AppUser>(authService);
+ * ```
+ *
+ * @example Supabase auth store
+ * ```ts
+ * import { createSupabaseAuthStore } from '@manacore/shared-auth-stores';
+ * import { createBrowserClient } from '@supabase/ssr';
+ *
+ * const getClient = () => createBrowserClient(url, key);
+ * export const authStore = createSupabaseAuthStore(getClient);
+ * ```
+ */
+
+// Factory functions
+export { createAuthStore } from './createAuthStore.svelte';
+export { createSupabaseAuthStore } from './createSupabaseAuthStore.svelte';
+export type { CreateSupabaseAuthStoreOptions, SupabaseUser } from './createSupabaseAuthStore.svelte';
+
+// Types
+export type {
+	BaseUser,
+	AuthResult,
+	AuthServiceAdapter,
+	AuthStoreState,
+	AuthStoreActions,
+	AuthStore
+} from './types';
diff --git a/packages/shared-auth-stores/src/types.ts b/packages/shared-auth-stores/src/types.ts
new file mode 100644
index 000000000..f88a3f3d9
--- /dev/null
+++ b/packages/shared-auth-stores/src/types.ts
@@ -0,0 +1,94 @@
+/**
+ * Shared Auth Store Types
+ * Generic types for creating auth stores with custom user types
+ */
+
+import type { AuthResult as BaseAuthResult } from '@manacore/shared-types';
+
+/**
+ * Base user interface that all app-specific user types must extend
+ */
+export interface BaseUser {
+	id: string;
+	email: string;
+}
+
+/**
+ * Auth operation result with typed user
+ */
+export interface AuthResult<TUser extends BaseUser = BaseUser> {
+	success: boolean;
+	error?: string;
+	needsVerification?: boolean;
+	user?: TUser;
+}
+
+/**
+ * Auth service interface that auth stores expect
+ * Apps implement this to integrate with their auth backend
+ */
+export interface AuthServiceAdapter<TUser extends BaseUser = BaseUser> {
+	/** Check if user is authenticated */
+	isAuthenticated(): Promise<boolean>;
+
+	/** Get user data from stored token/session */
+	getUserFromToken(): Promise<TUser | null>;
+
+	/** Sign in with email and password */
+	signIn(email: string, password: string): Promise<AuthResult<TUser>>;
+
+	/** Sign up with email and password */
+	signUp(email: string, password: string): Promise<AuthResult<TUser>>;
+
+	/** Send password reset email */
+	forgotPassword(email: string): Promise<{ success: boolean; error?: string }>;
+
+	/** Sign out user */
+	signOut(): Promise<void>;
+}
+
+/**
+ * Auth store state interface
+ */
+export interface AuthStoreState<TUser extends BaseUser = BaseUser> {
+	user: TUser | null;
+	loading: boolean;
+	error: string | null;
+	isAuthenticated: boolean;
+}
+
+/**
+ * Auth store actions interface
+ */
+export interface AuthStoreActions<TUser extends BaseUser = BaseUser> {
+	/** Initialize auth state from stored tokens */
+	initialize(): Promise<void>;
+
+	/** Set user manually */
+	setUser(user: TUser | null): void;
+
+	/** Sign in with email and password */
+	signIn(email: string, password: string): Promise<AuthResult<TUser>>;
+
+	/** Sign up with email and password */
+	signUp(email: string, password: string): Promise<AuthResult<TUser>>;
+
+	/** Send password reset email */
+	forgotPassword(email: string): Promise<{ success: boolean; error?: string }>;
+
+	/** Sign out user */
+	signOut(): Promise<void>;
+
+	/** Check authentication status */
+	checkAuth(): Promise<boolean>;
+
+	/** Clear error state */
+	clearError(): void;
+}
+
+/**
+ * Complete auth store interface
+ */
+export interface AuthStore<TUser extends BaseUser = BaseUser>
+	extends AuthStoreState<TUser>,
+		AuthStoreActions<TUser> {}
diff --git a/packages/shared-auth-stores/tsconfig.json b/packages/shared-auth-stores/tsconfig.json
new file mode 100644
index 000000000..96d56cbb1
--- /dev/null
+++ b/packages/shared-auth-stores/tsconfig.json
@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "isolatedModules": true,
+    "verbatimModuleSyntax": true,
+    "noEmit": true
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules"]
+}
diff --git a/packages/shared-types/src/auth.ts b/packages/shared-types/src/auth.ts
index 31658b70e..1f844fe1f 100644
--- a/packages/shared-types/src/auth.ts
+++ b/packages/shared-types/src/auth.ts
@@ -7,6 +7,65 @@
  */
 export type AuthState = 'loading' | 'authenticated' | 'unauthenticated';
 
+/**
+ * Standard authentication error codes
+ */
+export type AuthErrorCode =
+	| 'INVALID_CREDENTIALS'
+	| 'EMAIL_NOT_CONFIRMED'
+	| 'USER_NOT_FOUND'
+	| 'EMAIL_ALREADY_EXISTS'
+	| 'WEAK_PASSWORD'
+	| 'INVALID_EMAIL'
+	| 'RATE_LIMITED'
+	| 'TOKEN_EXPIRED'
+	| 'TOKEN_INVALID'
+	| 'NETWORK_ERROR'
+	| 'SERVER_ERROR'
+	| 'UNKNOWN_ERROR';
+
+/**
+ * Structured authentication error
+ */
+export interface AuthError {
+	code: AuthErrorCode;
+	message: string;
+	originalError?: unknown;
+}
+
+/**
+ * Map common Supabase error messages to AuthErrorCode
+ */
+export function mapSupabaseErrorToCode(message: string): AuthErrorCode {
+	const lowerMessage = message.toLowerCase();
+
+	if (lowerMessage.includes('invalid login credentials')) return 'INVALID_CREDENTIALS';
+	if (lowerMessage.includes('email not confirmed')) return 'EMAIL_NOT_CONFIRMED';
+	if (lowerMessage.includes('user not found')) return 'USER_NOT_FOUND';
+	if (lowerMessage.includes('already registered') || lowerMessage.includes('already exists'))
+		return 'EMAIL_ALREADY_EXISTS';
+	if (lowerMessage.includes('password') && lowerMessage.includes('weak')) return 'WEAK_PASSWORD';
+	if (lowerMessage.includes('invalid email')) return 'INVALID_EMAIL';
+	if (lowerMessage.includes('rate') || lowerMessage.includes('too many')) return 'RATE_LIMITED';
+	if (lowerMessage.includes('token') && lowerMessage.includes('expired')) return 'TOKEN_EXPIRED';
+	if (lowerMessage.includes('token') && lowerMessage.includes('invalid')) return 'TOKEN_INVALID';
+	if (lowerMessage.includes('network') || lowerMessage.includes('fetch')) return 'NETWORK_ERROR';
+	if (lowerMessage.includes('server') || lowerMessage.includes('500')) return 'SERVER_ERROR';
+
+	return 'UNKNOWN_ERROR';
+}
+
+/**
+ * Create an AuthError from a Supabase error message
+ */
+export function createAuthError(message: string, originalError?: unknown): AuthError {
+	return {
+		code: mapSupabaseErrorToCode(message),
+		message,
+		originalError
+	};
+}
+
 /**
  * User session
  */
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index d4c5fdeb2..9a21ddd34 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1576,6 +1576,22 @@ importers:
         specifier: ^5.9.3
         version: 5.9.3
 
+  packages/shared-auth-stores:
+    dependencies:
+      '@manacore/shared-types':
+        specifier: workspace:*
+        version: link:../shared-types
+    devDependencies:
+      svelte:
+        specifier: ^5.0.0
+        version: 5.43.14
+      svelte-check:
+        specifier: ^4.0.0
+        version: 4.3.4(picomatch@4.0.3)(svelte@5.43.14)(typescript@5.9.3)
+      typescript:
+        specifier: ^5.0.0
+        version: 5.9.3
+
   packages/shared-auth-ui:
     dependencies:
       '@manacore/shared-auth':