diff --git a/backend/src/models.rs b/backend/src/models.rs
index 2618982..ce3c8b1 100644
--- a/backend/src/models.rs
+++ b/backend/src/models.rs
@@ -1 +1,67 @@
-// models — populated in Task 3
+use serde::{Deserialize, Serialize};
+
+// --- DB rows ---
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Course { pub id: i64, pub name: String, pub semester: String }
+
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Tutor { pub id: i64, pub name: String, pub email: String }
+
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Student { pub id: i64, pub course_id: i64, pub name: String }
+
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Room { pub id: i64, pub name: String, pub layout_json: String }
+
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Session {
+    pub id: i64, pub course_id: i64,
+    pub week_nr: i64, pub date: String,
+}
+
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Slot {
+    pub id: i64, pub session_id: i64,
+    pub room_id: Option<i64>, pub tutor_id: i64,
+    pub start_time: String, pub end_time: String,
+    pub status: String, pub code: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Attendance {
+    pub id: i64, pub slot_id: i64, pub student_id: i64,
+    pub seat_id: Option<String>, pub checked_in_at: String,
+}
+
+#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
+pub struct Note {
+    pub id: i64, pub slot_id: i64, pub student_id: i64,
+    pub tutor_id: i64, pub content: String, pub updated_at: String,
+}
+
+// --- Layout element (nested in Room) ---
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct LayoutElement {
+    pub id: String, pub label: String,
+    pub x: f64, pub y: f64,
+    pub width: f64, pub height: f64,
+    #[serde(rename = "type")]
+    pub kind: String,  // "seat" | "table" | "gap" | "door"
+}
+
+// --- Request types ---
+#[derive(Deserialize)] pub struct CreateCourse { pub name: String, pub semester: String }
+#[derive(Deserialize)] pub struct CreateStudent { pub name: String }
+#[derive(Deserialize)] pub struct CreateRoom { pub name: String, pub layout: Vec<LayoutElement> }
+#[derive(Deserialize)] pub struct CreateSession { pub course_id: i64, pub week_nr: i64, pub date: String }
+#[derive(Deserialize)] pub struct CreateSlot {
+    pub session_id: i64, pub room_id: Option<i64>, pub tutor_id: i64,
+    pub start_time: String, pub end_time: String,
+}
+#[derive(Deserialize)] pub struct UpsertNote { pub content: String }
+#[derive(Deserialize)] pub struct ManualAttendance { pub student_id: i64 }
+#[derive(Deserialize)] pub struct CheckinRequest {
+    pub code: String,
+    pub student_id: i64,
+    pub seat_id: Option<String>,
+}