diff --git a/.changeset/sequelize-declare-attributes.md b/.changeset/sequelize-declare-attributes.md
new file mode 100644
index 0000000..d5de7f2
--- /dev/null
+++ b/.changeset/sequelize-declare-attributes.md
@@ -0,0 +1,20 @@
+---
+"seamless-templates": patch
+---
+
+fix(templates): declare Sequelize model attributes instead of using public class fields
+
+The `User` model in both API starters (`express` and `fastify`) declared its
+attributes as `public id!: string`. Sequelize installs its attribute getters and
+setters on the prototype, and a public class field is emitted as an own property
+initialised to undefined, which shadows them: `user.id` reads undefined while
+`user.get("id")` returns the row's value. Sequelize warns about this at model
+init. `declare` emits no field at all, so the accessors survive.
+
+Whether the field is emitted depends on `useDefineForClassFields`, which follows
+`target`. Both starters compile at `target: ES2020`, where the field is erased
+and the shadowing does not occur, so this is a guard rather than a repair of
+behaviour anyone is seeing today. It matters because the guard is what keeps a
+later `target` bump from silently breaking every model: at ES2022 the same code
+returns undefined for every attribute, and the first symptom is a query built
+with an undefined parameter on a handler that filters by `req.appUser.id`.
diff --git a/templates/api/express/models/user.ts b/templates/api/express/models/user.ts
index 425901d..e4ec9e0 100644
--- a/templates/api/express/models/user.ts
+++ b/templates/api/express/models/user.ts
@@ -10,11 +10,11 @@ export interface UserAttributes {
 }
 
 export class User extends Model<UserAttributes> implements UserAttributes {
-  public id!: string;
-  public email!: string | null;
-  public phone!: string | null;
-  public readonly created_at!: Date;
-  public readonly updated_at!: Date;
+  declare id: string;
+  declare email: string | null;
+  declare phone: string | null;
+  declare readonly created_at: Date;
+  declare readonly updated_at: Date;
 }
 
 const initializeUserModel = (sequelize: Sequelize) => {
diff --git a/templates/api/fastify/models/user.ts b/templates/api/fastify/models/user.ts
index 425901d..e4ec9e0 100644
--- a/templates/api/fastify/models/user.ts
+++ b/templates/api/fastify/models/user.ts
@@ -10,11 +10,11 @@ export interface UserAttributes {
 }
 
 export class User extends Model<UserAttributes> implements UserAttributes {
-  public id!: string;
-  public email!: string | null;
-  public phone!: string | null;
-  public readonly created_at!: Date;
-  public readonly updated_at!: Date;
+  declare id: string;
+  declare email: string | null;
+  declare phone: string | null;
+  declare readonly created_at: Date;
+  declare readonly updated_at: Date;
 }
 
 const initializeUserModel = (sequelize: Sequelize) => {