diff --git a/drizzle/0001_strange_lord_hawal.sql b/drizzle/0001_strange_lord_hawal.sql
new file mode 100644
index 0000000..8232865
--- /dev/null
+++ b/drizzle/0001_strange_lord_hawal.sql
@@ -0,0 +1,37 @@
+CREATE TABLE `login_attempts` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`ip` text NOT NULL,
+	`email` text NOT NULL,
+	`success` integer NOT NULL,
+	`timestamp` integer NOT NULL
+);
+--> statement-breakpoint
+CREATE INDEX `login_attempts_ip_timestamp_idx` ON `login_attempts` (`ip`,`timestamp`);--> statement-breakpoint
+DROP INDEX `tags_name_unique`;--> statement-breakpoint
+ALTER TABLE `tags` ADD `user_id` integer NOT NULL REFERENCES users(id);--> statement-breakpoint
+CREATE UNIQUE INDEX `tags_name_user_unique` ON `tags` (`name`,`user_id`);--> statement-breakpoint
+PRAGMA foreign_keys=OFF;--> statement-breakpoint
+CREATE TABLE `__new_users` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`email` text DEFAULT '' NOT NULL,
+	`display_name` text DEFAULT '' NOT NULL,
+	`role` text DEFAULT 'user' NOT NULL,
+	`password_hash` text,
+	`auth_provider` text DEFAULT 'password' NOT NULL,
+	`provider_id` text,
+	`created_at` integer NOT NULL
+);
+--> statement-breakpoint
+INSERT INTO `__new_users`("id", "email", "display_name", "role", "password_hash", "auth_provider", "provider_id", "created_at") SELECT "id", "email", "display_name", "role", "password_hash", "auth_provider", "provider_id", "created_at" FROM `users`;--> statement-breakpoint
+DROP TABLE `users`;--> statement-breakpoint
+ALTER TABLE `__new_users` RENAME TO `users`;--> statement-breakpoint
+PRAGMA foreign_keys=ON;--> statement-breakpoint
+ALTER TABLE `attachments` ADD `user_id` integer NOT NULL REFERENCES users(id);--> statement-breakpoint
+ALTER TABLE `attachments` ADD `featured` integer DEFAULT false NOT NULL;--> statement-breakpoint
+ALTER TABLE `notes` ADD `user_id` integer NOT NULL REFERENCES users(id);--> statement-breakpoint
+CREATE INDEX `notes_user_id_idx` ON `notes` (`user_id`);--> statement-breakpoint
+ALTER TABLE `sessions` ADD `created_at` integer;--> statement-breakpoint
+ALTER TABLE `sessions` ADD `user_agent` text;--> statement-breakpoint
+ALTER TABLE `sessions` ADD `ip` text;--> statement-breakpoint
+ALTER TABLE `sessions` ADD `last_used_at` integer;--> statement-breakpoint
+ALTER TABLE `sync_log` ADD `user_id` integer NOT NULL REFERENCES users(id);
\ No newline at end of file
diff --git a/drizzle/meta/0001_snapshot.json b/drizzle/meta/0001_snapshot.json
new file mode 100644
index 0000000..d799f6c
--- /dev/null
+++ b/drizzle/meta/0001_snapshot.json
@@ -0,0 +1,684 @@
+{
+  "version": "6",
+  "dialect": "sqlite",
+  "id": "9eb400be-28ff-4b92-be35-1cd0b344f2e3",
+  "prevId": "682b02aa-a28d-4904-8996-cbc4d740f626",
+  "tables": {
+    "attachments": {
+      "name": "attachments",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "user_id": {
+          "name": "user_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "note_id": {
+          "name": "note_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "filename": {
+          "name": "filename",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "mime_type": {
+          "name": "mime_type",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "size": {
+          "name": "size",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "path": {
+          "name": "path",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "thumbnail_path": {
+          "name": "thumbnail_path",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "featured": {
+          "name": "featured",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {},
+      "foreignKeys": {
+        "attachments_user_id_users_id_fk": {
+          "name": "attachments_user_id_users_id_fk",
+          "tableFrom": "attachments",
+          "tableTo": "users",
+          "columnsFrom": [
+            "user_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        },
+        "attachments_note_id_notes_id_fk": {
+          "name": "attachments_note_id_notes_id_fk",
+          "tableFrom": "attachments",
+          "tableTo": "notes",
+          "columnsFrom": [
+            "note_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "login_attempts": {
+      "name": "login_attempts",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "integer",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": true
+        },
+        "ip": {
+          "name": "ip",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "email": {
+          "name": "email",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "success": {
+          "name": "success",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "timestamp": {
+          "name": "timestamp",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "login_attempts_ip_timestamp_idx": {
+          "name": "login_attempts_ip_timestamp_idx",
+          "columns": [
+            "ip",
+            "timestamp"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {},
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "note_tags": {
+      "name": "note_tags",
+      "columns": {
+        "note_id": {
+          "name": "note_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "tag_id": {
+          "name": "tag_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "note_tags_note_id_idx": {
+          "name": "note_tags_note_id_idx",
+          "columns": [
+            "note_id"
+          ],
+          "isUnique": false
+        },
+        "note_tags_tag_id_idx": {
+          "name": "note_tags_tag_id_idx",
+          "columns": [
+            "tag_id"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "note_tags_note_id_notes_id_fk": {
+          "name": "note_tags_note_id_notes_id_fk",
+          "tableFrom": "note_tags",
+          "tableTo": "notes",
+          "columnsFrom": [
+            "note_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        },
+        "note_tags_tag_id_tags_id_fk": {
+          "name": "note_tags_tag_id_tags_id_fk",
+          "tableFrom": "note_tags",
+          "tableTo": "tags",
+          "columnsFrom": [
+            "tag_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "notes": {
+      "name": "notes",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "user_id": {
+          "name": "user_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "title": {
+          "name": "title",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "''"
+        },
+        "content": {
+          "name": "content",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "''"
+        },
+        "color": {
+          "name": "color",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'default'"
+        },
+        "pinned": {
+          "name": "pinned",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "archived": {
+          "name": "archived",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "trashed": {
+          "name": "trashed",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "trashed_at": {
+          "name": "trashed_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "checklist_mode": {
+          "name": "checklist_mode",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "sort_order": {
+          "name": "sort_order",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": 0
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "updated_at": {
+          "name": "updated_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "version": {
+          "name": "version",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": 1
+        }
+      },
+      "indexes": {
+        "notes_user_id_idx": {
+          "name": "notes_user_id_idx",
+          "columns": [
+            "user_id"
+          ],
+          "isUnique": false
+        },
+        "notes_trashed_archived_idx": {
+          "name": "notes_trashed_archived_idx",
+          "columns": [
+            "trashed",
+            "archived"
+          ],
+          "isUnique": false
+        },
+        "notes_updated_at_idx": {
+          "name": "notes_updated_at_idx",
+          "columns": [
+            "updated_at"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "notes_user_id_users_id_fk": {
+          "name": "notes_user_id_users_id_fk",
+          "tableFrom": "notes",
+          "tableTo": "users",
+          "columnsFrom": [
+            "user_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "sessions": {
+      "name": "sessions",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "user_id": {
+          "name": "user_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "expires_at": {
+          "name": "expires_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "user_agent": {
+          "name": "user_agent",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "ip": {
+          "name": "ip",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "last_used_at": {
+          "name": "last_used_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        }
+      },
+      "indexes": {},
+      "foreignKeys": {
+        "sessions_user_id_users_id_fk": {
+          "name": "sessions_user_id_users_id_fk",
+          "tableFrom": "sessions",
+          "tableTo": "users",
+          "columnsFrom": [
+            "user_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "sync_log": {
+      "name": "sync_log",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "integer",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": true
+        },
+        "user_id": {
+          "name": "user_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "note_id": {
+          "name": "note_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "operation": {
+          "name": "operation",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "timestamp": {
+          "name": "timestamp",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "client_id": {
+          "name": "client_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "sync_log_timestamp_idx": {
+          "name": "sync_log_timestamp_idx",
+          "columns": [
+            "timestamp"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "sync_log_user_id_users_id_fk": {
+          "name": "sync_log_user_id_users_id_fk",
+          "tableFrom": "sync_log",
+          "tableTo": "users",
+          "columnsFrom": [
+            "user_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        },
+        "sync_log_note_id_notes_id_fk": {
+          "name": "sync_log_note_id_notes_id_fk",
+          "tableFrom": "sync_log",
+          "tableTo": "notes",
+          "columnsFrom": [
+            "note_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "tags": {
+      "name": "tags",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "integer",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": true
+        },
+        "user_id": {
+          "name": "user_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "name": {
+          "name": "name",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "tags_name_user_unique": {
+          "name": "tags_name_user_unique",
+          "columns": [
+            "name",
+            "user_id"
+          ],
+          "isUnique": true
+        }
+      },
+      "foreignKeys": {
+        "tags_user_id_users_id_fk": {
+          "name": "tags_user_id_users_id_fk",
+          "tableFrom": "tags",
+          "tableTo": "users",
+          "columnsFrom": [
+            "user_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "users": {
+      "name": "users",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "integer",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": true
+        },
+        "email": {
+          "name": "email",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "''"
+        },
+        "display_name": {
+          "name": "display_name",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "''"
+        },
+        "role": {
+          "name": "role",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'user'"
+        },
+        "password_hash": {
+          "name": "password_hash",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "auth_provider": {
+          "name": "auth_provider",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'password'"
+        },
+        "provider_id": {
+          "name": "provider_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {},
+      "foreignKeys": {},
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    }
+  },
+  "views": {},
+  "enums": {},
+  "_meta": {
+    "schemas": {},
+    "tables": {},
+    "columns": {}
+  },
+  "internal": {
+    "indexes": {}
+  }
+}
\ No newline at end of file
diff --git a/drizzle/meta/_journal.json b/drizzle/meta/_journal.json
index 377f5a8..a50a8f1 100644
--- a/drizzle/meta/_journal.json
+++ b/drizzle/meta/_journal.json
@@ -8,6 +8,13 @@
       "when": 1773000424830,
       "tag": "0000_wooden_vargas",
       "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "6",
+      "when": 1773016788899,
+      "tag": "0001_strange_lord_hawal",
+      "breakpoints": true
     }
   ]
 }
\ No newline at end of file
diff --git a/src/lib/server/attachments.ts b/src/lib/server/attachments.ts
index e63549b..aaacbf1 100644
--- a/src/lib/server/attachments.ts
+++ b/src/lib/server/attachments.ts
@@ -4,7 +4,7 @@ import { join } from 'path';
 import { v4 as uuidv4 } from 'uuid';
 import { db } from './db/index.js';
 import { attachments } from './db/schema.js';
-import { eq, inArray } from 'drizzle-orm';
+import { eq, and, inArray } from 'drizzle-orm';
 import type { Attachment } from '$lib/types/index.js';
 
 const DATA_DIR = process.env.DATA_DIR || './data';
@@ -80,25 +80,29 @@ export function fetchAttachmentsForNotes(noteIds: string[]): Map<string, Attachm
 	return map;
 }
 
-export async function getAttachment(id: string) {
-	return db.select().from(attachments).where(eq(attachments.id, id)).get();
+export async function getAttachment(id: string, noteId: string) {
+	return db
+		.select()
+		.from(attachments)
+		.where(and(eq(attachments.id, id), eq(attachments.noteId, noteId)))
+		.get();
 }
 
 export async function getAttachmentsByNote(noteId: string) {
 	return db.select().from(attachments).where(eq(attachments.noteId, noteId));
 }
 
-export async function updateAttachment(id: string, data: { featured: boolean }) {
+export async function updateAttachment(id: string, noteId: string, data: { featured: boolean }) {
 	const [updated] = await db
 		.update(attachments)
 		.set({ featured: data.featured })
-		.where(eq(attachments.id, id))
+		.where(and(eq(attachments.id, id), eq(attachments.noteId, noteId)))
 		.returning();
 	return updated ?? null;
 }
 
-export async function deleteAttachment(id: string) {
-	const attachment = await getAttachment(id);
+export async function deleteAttachment(id: string, noteId: string) {
+	const attachment = await getAttachment(id, noteId);
 	if (attachment) {
 		try {
 			await unlink(attachment.path);
@@ -112,6 +116,6 @@ export async function deleteAttachment(id: string) {
 				// Thumbnail may already be deleted
 			}
 		}
-		await db.delete(attachments).where(eq(attachments.id, id));
+		await db.delete(attachments).where(and(eq(attachments.id, id), eq(attachments.noteId, noteId)));
 	}
 }
diff --git a/src/lib/server/db/notes.test.ts b/src/lib/server/db/notes.test.ts
index 826b41c..b289520 100644
--- a/src/lib/server/db/notes.test.ts
+++ b/src/lib/server/db/notes.test.ts
@@ -9,7 +9,7 @@ import type * as schema from './schema.js';
 let db: BetterSQLite3Database<typeof schema>;
 
 beforeEach(() => {
-	const testDb = createTestDb();
+	const testDb = createTestDb({ seedUser: true });
 	db = testDb.db;
 });
 
@@ -20,6 +20,7 @@ describe('Notes CRUD', () => {
 
 		await db.insert(notes).values({
 			id,
+			userId: 1,
 			title: 'Test Note',
 			content: 'Hello world',
 			createdAt: now,
@@ -45,6 +46,7 @@ describe('Notes CRUD', () => {
 
 		await db.insert(notes).values({
 			id,
+			userId: 1,
 			title: 'Colored Note',
 			content: '',
 			color: 'coral',
@@ -62,16 +64,17 @@ describe('Notes CRUD', () => {
 	it('should read all active notes (not archived, not trashed)', async () => {
 		const now = new Date();
 		await db.insert(notes).values([
-			{ id: 'n1', title: 'Active', content: '', createdAt: now, updatedAt: now },
+			{ id: 'n1', userId: 1, title: 'Active', content: '', createdAt: now, updatedAt: now },
 			{
 				id: 'n2',
+				userId: 1,
 				title: 'Archived',
 				content: '',
 				archived: true,
 				createdAt: now,
 				updatedAt: now
 			},
-			{ id: 'n3', title: 'Trashed', content: '', trashed: true, createdAt: now, updatedAt: now }
+			{ id: 'n3', userId: 1, title: 'Trashed', content: '', trashed: true, createdAt: now, updatedAt: now }
 		]);
 
 		const active = await db
@@ -89,6 +92,7 @@ describe('Notes CRUD', () => {
 
 		await db.insert(notes).values({
 			id,
+			userId: 1,
 			title: 'Original',
 			content: '',
 			createdAt: now,
@@ -113,6 +117,7 @@ describe('Notes CRUD', () => {
 
 		await db.insert(notes).values({
 			id,
+			userId: 1,
 			title: 'To Trash',
 			content: '',
 			createdAt: now,
@@ -132,6 +137,7 @@ describe('Notes CRUD', () => {
 
 		await db.insert(notes).values({
 			id,
+			userId: 1,
 			title: 'To Delete',
 			content: '',
 			createdAt: now,
@@ -149,6 +155,7 @@ describe('Notes CRUD', () => {
 
 		await db.insert(notes).values({
 			id,
+			userId: 1,
 			title: 'To Archive',
 			content: '',
 			createdAt: now,
@@ -170,6 +177,7 @@ describe('Notes CRUD', () => {
 
 		await db.insert(notes).values({
 			id,
+			userId: 1,
 			title: 'Pin Me',
 			content: '',
 			createdAt: now,
@@ -193,6 +201,7 @@ describe('Notes with Tags', () => {
 
 		await db.insert(notes).values({
 			id: noteId,
+			userId: 1,
 			title: 'Tagged Note',
 			content: '',
 			createdAt: now,
@@ -200,8 +209,8 @@ describe('Notes with Tags', () => {
 		});
 
 		// Create tags
-		const [tag1] = await db.insert(tags).values({ name: 'work' }).returning();
-		const [tag2] = await db.insert(tags).values({ name: 'important' }).returning();
+		const [tag1] = await db.insert(tags).values({ userId: 1, name: 'work' }).returning();
+		const [tag2] = await db.insert(tags).values({ userId: 1, name: 'important' }).returning();
 
 		// Associate
 		await db.insert(noteTags).values([
@@ -226,13 +235,14 @@ describe('Notes with Tags', () => {
 
 		await db.insert(notes).values({
 			id: noteId,
+			userId: 1,
 			title: '',
 			content: '',
 			createdAt: now,
 			updatedAt: now
 		});
 
-		const [tag] = await db.insert(tags).values({ name: 'temp' }).returning();
+		const [tag] = await db.insert(tags).values({ userId: 1, name: 'temp' }).returning();
 		await db.insert(noteTags).values({ noteId, tagId: tag.id });
 
 		// Delete note_tags first (FK cascade is disabled in test DB), then note
@@ -258,6 +268,7 @@ describe('Note ordering', () => {
 		await db.insert(notes).values([
 			{
 				id: 'unpinned',
+				userId: 1,
 				title: 'Unpinned',
 				content: '',
 				pinned: false,
@@ -266,6 +277,7 @@ describe('Note ordering', () => {
 			},
 			{
 				id: 'pinned',
+				userId: 1,
 				title: 'Pinned',
 				content: '',
 				pinned: true,
diff --git a/src/lib/server/db/schema.ts b/src/lib/server/db/schema.ts
index eeb5002..484c0c5 100644
--- a/src/lib/server/db/schema.ts
+++ b/src/lib/server/db/schema.ts
@@ -29,8 +29,7 @@ export const notes = sqliteTable(
 		id: text('id').primaryKey(),
 		userId: integer('user_id')
 			.references(() => users.id)
-			.notNull()
-			.default(0),
+			.notNull(),
 		title: text('title').default('').notNull(),
 		content: text('content').default('').notNull(),
 		color: text('color').default('default').notNull(),
@@ -57,8 +56,7 @@ export const tags = sqliteTable(
 		id: integer('id').primaryKey({ autoIncrement: true }),
 		userId: integer('user_id')
 			.references(() => users.id)
-			.notNull()
-			.default(0),
+			.notNull(),
 		name: text('name').notNull()
 	},
 	(table) => [uniqueIndex('tags_name_user_unique').on(table.name, table.userId)]
@@ -84,8 +82,7 @@ export const attachments = sqliteTable('attachments', {
 	id: text('id').primaryKey(),
 	userId: integer('user_id')
 		.references(() => users.id)
-		.notNull()
-		.default(0),
+		.notNull(),
 	noteId: text('note_id')
 		.references(() => notes.id, { onDelete: 'cascade' })
 		.notNull(),
@@ -104,8 +101,7 @@ export const syncLog = sqliteTable(
 		id: integer('id').primaryKey({ autoIncrement: true }),
 		userId: integer('user_id')
 			.references(() => users.id)
-			.notNull()
-			.default(0),
+			.notNull(),
 		noteId: text('note_id')
 			.references(() => notes.id)
 			.notNull(),
diff --git a/src/lib/server/db/search.test.ts b/src/lib/server/db/search.test.ts
index 74551d3..3d6d394 100644
--- a/src/lib/server/db/search.test.ts
+++ b/src/lib/server/db/search.test.ts
@@ -8,18 +8,18 @@ import type * as schema from './schema.js';
 let db: BetterSQLite3Database<typeof schema>;
 
 beforeEach(async () => {
-	const testDb = createTestDb();
+	const testDb = createTestDb({ seedUser: true });
 	db = testDb.db;
 
 	const now = new Date();
 	await db.insert(notes).values([
-		{ id: 'n1', title: 'Shopping List', content: 'Buy milk and eggs', createdAt: now, updatedAt: now },
-		{ id: 'n2', title: 'Work Notes', content: 'Meeting at 3pm #work', createdAt: now, updatedAt: now },
-		{ id: 'n3', title: 'Recipe', content: 'Pasta with tomato sauce', createdAt: now, updatedAt: now },
-		{ id: 'n4', title: 'Trashed', content: 'Should not appear', trashed: true, createdAt: now, updatedAt: now }
+		{ id: 'n1', userId: 1, title: 'Shopping List', content: 'Buy milk and eggs', createdAt: now, updatedAt: now },
+		{ id: 'n2', userId: 1, title: 'Work Notes', content: 'Meeting at 3pm #work', createdAt: now, updatedAt: now },
+		{ id: 'n3', userId: 1, title: 'Recipe', content: 'Pasta with tomato sauce', createdAt: now, updatedAt: now },
+		{ id: 'n4', userId: 1, title: 'Trashed', content: 'Should not appear', trashed: true, createdAt: now, updatedAt: now }
 	]);
 
-	const [workTag] = await db.insert(tags).values({ name: 'work' }).returning();
+	const [workTag] = await db.insert(tags).values({ userId: 1, name: 'work' }).returning();
 	await db.insert(noteTags).values({ noteId: 'n2', tagId: workTag.id });
 });
 
diff --git a/src/lib/server/db/test-helpers.ts b/src/lib/server/db/test-helpers.ts
index 765929b..a3fccfe 100644
--- a/src/lib/server/db/test-helpers.ts
+++ b/src/lib/server/db/test-helpers.ts
@@ -6,7 +6,7 @@ import * as schema from './schema.js';
  * Create an in-memory SQLite database for testing.
  * Each test gets a fresh database.
  */
-export function createTestDb() {
+export function createTestDb({ seedUser = false }: { seedUser?: boolean } = {}) {
 	const sqlite = new Database(':memory:');
 	sqlite.pragma('journal_mode = WAL');
 	sqlite.pragma('foreign_keys = OFF');
@@ -36,7 +36,7 @@ export function createTestDb() {
 
 		CREATE TABLE notes (
 			id TEXT PRIMARY KEY,
-			user_id INTEGER NOT NULL DEFAULT 0 REFERENCES users(id),
+			user_id INTEGER NOT NULL REFERENCES users(id),
 			title TEXT NOT NULL DEFAULT '',
 			content TEXT NOT NULL DEFAULT '',
 			color TEXT NOT NULL DEFAULT 'default',
@@ -56,7 +56,7 @@ export function createTestDb() {
 
 		CREATE TABLE tags (
 			id INTEGER PRIMARY KEY AUTOINCREMENT,
-			user_id INTEGER NOT NULL DEFAULT 0 REFERENCES users(id),
+			user_id INTEGER NOT NULL REFERENCES users(id),
 			name TEXT NOT NULL
 		);
 		CREATE UNIQUE INDEX tags_name_user_unique ON tags(name, user_id);
@@ -70,7 +70,7 @@ export function createTestDb() {
 
 		CREATE TABLE attachments (
 			id TEXT PRIMARY KEY,
-			user_id INTEGER NOT NULL DEFAULT 0 REFERENCES users(id),
+			user_id INTEGER NOT NULL REFERENCES users(id),
 			note_id TEXT NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
 			filename TEXT NOT NULL,
 			mime_type TEXT NOT NULL,
@@ -81,7 +81,7 @@ export function createTestDb() {
 
 		CREATE TABLE sync_log (
 			id INTEGER PRIMARY KEY AUTOINCREMENT,
-			user_id INTEGER NOT NULL DEFAULT 0 REFERENCES users(id),
+			user_id INTEGER NOT NULL REFERENCES users(id),
 			note_id TEXT NOT NULL REFERENCES notes(id),
 			operation TEXT NOT NULL,
 			timestamp INTEGER NOT NULL,
@@ -99,6 +99,10 @@ export function createTestDb() {
 		CREATE INDEX login_attempts_ip_timestamp_idx ON login_attempts(ip, timestamp);
 	`);
 
+	if (seedUser) {
+		sqlite.prepare(`INSERT INTO users (id, email, created_at) VALUES (?, ?, ?)`).run(1, 'test@test.com', 0);
+	}
+
 	const db = drizzle(sqlite, { schema });
 	return { db, sqlite };
 }
diff --git a/src/lib/server/tags.ts b/src/lib/server/tags.ts
index f193334..199c7ae 100644
--- a/src/lib/server/tags.ts
+++ b/src/lib/server/tags.ts
@@ -1,6 +1,6 @@
 import { db } from './db/index.js';
 import { noteTags, tags } from './db/schema.js';
-import { eq, inArray } from 'drizzle-orm';
+import { eq, and, inArray } from 'drizzle-orm';
 
 /**
  * Batch fetch tags for multiple notes in a single query.
@@ -32,13 +32,17 @@ export function fetchTagsForNotes(noteIds: string[]): Map<string, string[]> {
  * Sync tags for a note: removes old associations, upserts tags, creates new associations.
  * Should be called within a transaction for atomicity.
  */
-export function syncNoteTags(noteId: string, tagNames: string[]) {
+export function syncNoteTags(noteId: string, tagNames: string[], userId: number) {
 	db.delete(noteTags).where(eq(noteTags.noteId, noteId)).run();
 
 	for (const name of tagNames) {
-		let tagRow = db.select().from(tags).where(eq(tags.name, name)).get();
+		let tagRow = db
+			.select()
+			.from(tags)
+			.where(and(eq(tags.name, name), eq(tags.userId, userId)))
+			.get();
 		if (!tagRow) {
-			const result = db.insert(tags).values({ name }).returning().all();
+			const result = db.insert(tags).values({ name, userId }).returning().all();
 			tagRow = result[0];
 		}
 		db.insert(noteTags).values({ noteId, tagId: tagRow.id }).run();
diff --git a/src/lib/sync/server.ts b/src/lib/sync/server.ts
index 479bb91..9bb70e9 100644
--- a/src/lib/sync/server.ts
+++ b/src/lib/sync/server.ts
@@ -81,7 +81,7 @@ export async function processSyncPush(changes: SyncQueueItem[], userId: number):
 		const note = db.select().from(notes).where(and(eq(notes.id, noteId), eq(notes.userId, userId))).get();
 		if (note) {
 			const content = `${note.title} ${note.content}`;
-			syncNoteTags(noteId, extractTags(content));
+			syncNoteTags(noteId, extractTags(content), userId);
 		}
 	}
 }
diff --git a/src/routes/api/notes/+server.ts b/src/routes/api/notes/+server.ts
index c02ebad..11016c6 100644
--- a/src/routes/api/notes/+server.ts
+++ b/src/routes/api/notes/+server.ts
@@ -73,7 +73,7 @@ export const POST: RequestHandler = async ({ request, ...event }) => {
 	db.transaction((tx) => {
 		tx.insert(notes).values(newNote).run();
 	});
-	syncNoteTags(id, extractedTags);
+	syncNoteTags(id, extractedTags, userId);
 
 	return json({ ...newNote, tags: extractedTags }, { status: 201 });
 };
diff --git a/src/routes/api/notes/[id]/+server.ts b/src/routes/api/notes/[id]/+server.ts
index facd0a5..5d8e693 100644
--- a/src/routes/api/notes/[id]/+server.ts
+++ b/src/routes/api/notes/[id]/+server.ts
@@ -68,7 +68,7 @@ export const PATCH: RequestHandler = async ({ params, request, ...event }) => {
 	if (body.title !== undefined || body.content !== undefined) {
 		const content = `${updated!.title} ${updated!.content}`;
 		const extractedTags = extractTags(content);
-		syncNoteTags(params.id, extractedTags);
+		syncNoteTags(params.id, extractedTags, userId);
 	}
 
 	const tagMap = fetchTagsForNotes([params.id]);
diff --git a/src/routes/api/notes/[id]/attachments/+server.ts b/src/routes/api/notes/[id]/attachments/+server.ts
index 0a3c695..cc7ef7c 100644
--- a/src/routes/api/notes/[id]/attachments/+server.ts
+++ b/src/routes/api/notes/[id]/attachments/+server.ts
@@ -25,7 +25,7 @@ export const GET: RequestHandler = async ({ params, url, ...event }) => {
 	const attachmentId = url.searchParams.get('attachmentId');
 
 	if (attachmentId) {
-		const attachment = await getAttachment(attachmentId);
+		const attachment = await getAttachment(attachmentId, params.id);
 		if (!attachment) throw error(404, 'Attachment not found');
 
 		const wantThumb = url.searchParams.get('thumb') === '1';
@@ -81,7 +81,7 @@ export const PATCH: RequestHandler = async ({ params, url, request, ...event })
 	const body = await request.json();
 	if (typeof body.featured !== 'boolean') throw error(400, 'featured (boolean) required');
 
-	const updated = await updateAttachment(attachmentId, { featured: body.featured });
+	const updated = await updateAttachment(attachmentId, params.id, { featured: body.featured });
 	if (!updated) throw error(404, 'Attachment not found');
 
 	return json(updated);
@@ -94,6 +94,6 @@ export const DELETE: RequestHandler = async ({ params, url, ...event }) => {
 	const attachmentId = url.searchParams.get('attachmentId');
 	if (!attachmentId) throw error(400, 'attachmentId required');
 
-	await deleteAttachment(attachmentId);
+	await deleteAttachment(attachmentId, params.id);
 	return json({ success: true });
 };
diff --git a/src/routes/api/notes/reorder/+server.ts b/src/routes/api/notes/reorder/+server.ts
index 94550a2..a7953cc 100644
--- a/src/routes/api/notes/reorder/+server.ts
+++ b/src/routes/api/notes/reorder/+server.ts
@@ -2,9 +2,11 @@ import { json } from '@sveltejs/kit';
 import type { RequestHandler } from './$types.js';
 import { db } from '$lib/server/db/index.js';
 import { notes } from '$lib/server/db/schema.js';
-import { eq } from 'drizzle-orm';
+import { eq, and } from 'drizzle-orm';
+import { getUserId } from '$lib/server/api-utils.js';
 
-export const POST: RequestHandler = async ({ request }) => {
+export const POST: RequestHandler = async ({ request, ...event }) => {
+	const userId = getUserId(event);
 	const body = await request.json();
 	const orders: { id: string; sortOrder: number }[] = body.orders;
 
@@ -14,7 +16,10 @@ export const POST: RequestHandler = async ({ request }) => {
 
 	db.transaction((tx) => {
 		for (const { id, sortOrder } of orders) {
-			tx.update(notes).set({ sortOrder }).where(eq(notes.id, id)).run();
+			tx.update(notes)
+				.set({ sortOrder })
+				.where(and(eq(notes.id, id), eq(notes.userId, userId)))
+				.run();
 		}
 	});