diff --git a/modules/model/src/main/scala/gs/smolban/model/CreatedBy.scala b/modules/model/src/main/scala/gs/smolban/model/CreatedBy.scala
new file mode 100644
index 0000000..6e4f27e
--- /dev/null
+++ b/modules/model/src/main/scala/gs/smolban/model/CreatedBy.scala
@@ -0,0 +1,24 @@
+package gs.smolban.model
+
+import cats.Show
+import gs.smolban.model.users.User
+
+opaque type CreatedBy = User.Id
+
+object CreatedBy:
+
+  def apply(timestamp: User.Id): CreatedBy = timestamp
+
+  given CanEqual[CreatedBy, CreatedBy] = CanEqual.derived
+
+  given Show[CreatedBy] = _.toUserId().toUUID().withoutDashes()
+
+  extension (createdAt: CreatedBy)
+    /** Unwrap this value.
+      *
+      * @return
+      *   The underlying `User.Id` value.
+      */
+    def toUserId(): User.Id = createdAt
+
+end CreatedBy
diff --git a/modules/model/src/main/scala/gs/smolban/model/Group.scala b/modules/model/src/main/scala/gs/smolban/model/Group.scala
index 3b66350..31994b6 100644
--- a/modules/model/src/main/scala/gs/smolban/model/Group.scala
+++ b/modules/model/src/main/scala/gs/smolban/model/Group.scala
@@ -22,6 +22,8 @@ case class Group(
 
 object Group:
 
+  given CanEqual[Group, Group] = CanEqual.derived
+
   /** Unique identifier for a [[Group]]. This is an opaque type for a UUID.
     */
   opaque type Id = UUID
diff --git a/modules/model/src/main/scala/gs/smolban/model/Status.scala b/modules/model/src/main/scala/gs/smolban/model/Status.scala
new file mode 100644
index 0000000..f62918d
--- /dev/null
+++ b/modules/model/src/main/scala/gs/smolban/model/Status.scala
@@ -0,0 +1,38 @@
+package gs.smolban.model
+
+/** Enumeration that describes the status of a [[Ticket]] in Smolban. Smolban
+  * does not yet support custom status/workflow.
+  *
+  * @param value
+  *   The string value of the status.
+  */
+sealed abstract class Status(val value: String)
+
+object Status:
+
+  /** This ticket is new, and ready to be started. New tickets may be put into
+    * progress or canceled.
+    */
+  case object Ready extends Status("ready")
+
+  /** This ticket is being worked on actively. In progress tickets can be
+    * paused, completed, or canceled.
+    */
+  case object InProgress extends Status("in_progress")
+
+  /** This ticket was being worked on, but was temporarily stopped. Paused
+    * tickets may be put into progress or canceled.
+    */
+  case object Paused extends Status("paused")
+
+  /** This ticket was driven to completion. The work is done. Once in this
+    * state, the status may no longer change.
+    */
+  case object Complete extends Status("complete")
+
+  /** This ticket was canceled for some reason. Once in this state, the status
+    * may no longer change.
+    */
+  case object Canceled extends Status("canceled")
+
+end Status
diff --git a/modules/model/src/main/scala/gs/smolban/model/Tag.scala b/modules/model/src/main/scala/gs/smolban/model/Tag.scala
new file mode 100644
index 0000000..d836df2
--- /dev/null
+++ b/modules/model/src/main/scala/gs/smolban/model/Tag.scala
@@ -0,0 +1,21 @@
+package gs.smolban.model
+
+import cats.Show
+
+/** Opaque type for a String that represents a unique `Tag` in Smolban. Tags are
+  * just arbitrary non-empty strings which can be used to annotate [[Ticket]].
+  *
+  * Tags are defined _globally_ in Smolban.
+  */
+opaque type Tag = String
+
+object Tag:
+
+  def validate(candidate: String): Option[Tag] =
+    if candidate.isEmpty() then None else Some(candidate)
+
+  given CanEqual[Tag, Tag] = CanEqual.derived
+
+  given Show[Tag] = t => t
+
+end Tag
diff --git a/modules/model/src/main/scala/gs/smolban/model/Ticket.scala b/modules/model/src/main/scala/gs/smolban/model/Ticket.scala
index f373bef..c63de5b 100644
--- a/modules/model/src/main/scala/gs/smolban/model/Ticket.scala
+++ b/modules/model/src/main/scala/gs/smolban/model/Ticket.scala
@@ -3,9 +3,15 @@ package gs.smolban.model
 import cats.Show
 
 case class Ticket(
-  id: Long,
+  id: Ticket.Id,
   group: Group.Id,
-  createdAt: CreatedAt
+  createdAt: CreatedAt,
+  createdBy: CreatedBy,
+  title: String,
+  description: String,
+  tags: List[Tag],
+  status: Status,
+  statusHistory: List[Status]
 )
 
 object Ticket:
diff --git a/modules/model/src/main/scala/gs/smolban/model/users/User.scala b/modules/model/src/main/scala/gs/smolban/model/users/User.scala
new file mode 100644
index 0000000..ab2073d
--- /dev/null
+++ b/modules/model/src/main/scala/gs/smolban/model/users/User.scala
@@ -0,0 +1,46 @@
+package gs.smolban.model.users
+
+import cats.Show
+import gs.smolban.model.CreatedAt
+import gs.uuid.v0.UUID
+
+case class User(
+  id: User.Id,
+  createdAt: CreatedAt,
+  username: Username
+)
+
+object User:
+
+  given CanEqual[User, User] = CanEqual.derived
+
+  /** Unique identifier for a [[User]]. This is an opaque type for a UUID.
+    */
+  opaque type Id = UUID
+
+  object Id:
+
+    /** Instantiate a new [[User.Id]].
+      *
+      * @param id
+      *   The underlying UUID.
+      * @return
+      *   The new [[User.Id]] instance.
+      */
+    def apply(id: UUID): Id = id
+
+    given CanEqual[Id, Id] = CanEqual.derived
+
+    given Show[Id] = _.toUUID().withoutDashes()
+
+    extension (id: Id)
+      /** Unwrap this User ID.
+        *
+        * @return
+        *   The underlying UUID value.
+        */
+      def toUUID(): UUID = id
+
+  end Id
+
+end User
diff --git a/modules/model/src/main/scala/gs/smolban/model/users/Username.scala b/modules/model/src/main/scala/gs/smolban/model/users/Username.scala
new file mode 100644
index 0000000..a14b137
--- /dev/null
+++ b/modules/model/src/main/scala/gs/smolban/model/users/Username.scala
@@ -0,0 +1,47 @@
+package gs.smolban.model.users
+
+import cats.Show
+
+/** Opaque type for String that represents a unique username in Smolban.
+  */
+opaque type Username = String
+
+object Username:
+
+  /** In Smolban, a [[Username]] must be at most 32 characters long.
+    */
+  val MaximumLength: Int = 32
+
+  /** In Smolban, a [[Username]] must be at least 3 characters long.
+    */
+  val MinimumLength: Int = 3
+
+  given CanEqual[Username, Username] = CanEqual.derived
+
+  /** Validate some candidate string, producing a [[Username]] if valid. Smolban
+    * usernames must be:
+    *
+    *   - At least 3 characters long.
+    *   - At most 32 characters long.
+    *   - Non-blank -- non-whitespace characters must be used.
+    *
+    * @param candidate
+    *   The candidate string to evaluate.
+    * @return
+    *   The [[Username]], or `None` if the candidate was invalid.
+    */
+  def validate(candidate: String): Option[Username] =
+    if isValid(candidate) then Some(candidate) else None
+
+  private def isValid(candidate: String): Boolean =
+    isValidSize(candidate) && isNonBlank(candidate)
+
+  private def isValidSize(candidate: String): Boolean =
+    candidate.length() >= MinimumLength && candidate.length() <= MaximumLength
+
+  private def isNonBlank(candidate: String): Boolean =
+    !candidate.isBlank()
+
+  given Show[Username] = u => u
+
+end Username