diff --git a/databuild/lib.rs b/databuild/lib.rs
index 5d669dc..ac9339c 100644
--- a/databuild/lib.rs
+++ b/databuild/lib.rs
@@ -8,6 +8,7 @@ mod build_state;
 mod event_transforms;
 mod data_deps;
 mod mock_job_run;
+mod want_state;
 
 // Include generated protobuf code
 include!("databuild.rs");
diff --git a/databuild/want_state.rs b/databuild/want_state.rs
new file mode 100644
index 0000000..32d01cb
--- /dev/null
+++ b/databuild/want_state.rs
@@ -0,0 +1,289 @@
+use crate::util::current_timestamp;
+use crate::{EventSource, PartitionRef, WantDetail, WantStatus, WantStatusCode};
+
+/// State: Want has been created and is ready to be scheduled
+#[derive(Debug, Clone)]
+pub struct IdleState {}
+
+/// State: Want is currently being built by one or more jobs
+#[derive(Debug, Clone)]
+pub struct BuildingState {
+    pub started_at: u64,
+}
+
+/// State: Want is waiting for upstream dependencies to be built
+#[derive(Debug, Clone)]
+pub struct UpstreamBuildingState {
+    pub upstream_want_ids: Vec<String>,
+}
+
+/// State: Want has been successfully completed (all partitions live)
+#[derive(Debug, Clone)]
+pub struct SuccessfulState {
+    pub completed_at: u64,
+}
+
+/// State: Want failed because a partition build failed
+#[derive(Debug, Clone)]
+pub struct FailedState {
+    pub failed_at: u64,
+    pub failed_partition_refs: Vec<PartitionRef>,
+    pub failure_reason: String,
+}
+
+/// State: Want failed because an upstream dependency failed
+#[derive(Debug, Clone)]
+pub struct UpstreamFailedState {
+    pub failed_at: u64,
+    pub failed_wants: Vec<String>, // wants that failed
+}
+
+/// State: Want has been explicitly canceled
+#[derive(Debug, Clone)]
+pub struct CanceledState {
+    pub canceled_at: u64,
+    pub canceled_by: Option<EventSource>,
+    pub comment: Option<String>,
+}
+
+#[derive(Debug, Clone)]
+pub struct WantInfo {
+    pub want_id: String,
+    pub partitions: Vec<PartitionRef>,
+    pub upstreams: Vec<PartitionRef>,
+    pub data_timestamp: u64,
+    pub ttl_seconds: u64,
+    pub sla_seconds: u64,
+    pub source: Option<EventSource>,
+    pub comment: Option<String>,
+    pub last_updated_at: u64,
+}
+
+impl WantInfo {
+    pub fn updated_timestamp(self) -> Self {
+        Self { last_updated_at: current_timestamp(), ..self }
+    }
+}
+
+/// Generic want struct parameterized by state
+#[derive(Debug, Clone)]
+pub struct WantWithState<S> {
+    pub want: WantInfo,
+    pub state: S,
+}
+
+/// Wrapper enum for storing wants in collections
+#[derive(Debug, Clone)]
+pub enum Want {
+    Idle(WantWithState<IdleState>),
+    Building(WantWithState<BuildingState>),
+    UpstreamBuilding(WantWithState<UpstreamBuildingState>),
+    Successful(WantWithState<SuccessfulState>),
+    Failed(WantWithState<FailedState>),
+    UpstreamFailed(WantWithState<UpstreamFailedState>),
+    Canceled(WantWithState<CanceledState>),
+}
+
+// Type-safe transition methods for IdleState
+impl WantWithState<IdleState> {
+    /// Transition from Idle to Building when a job starts building this want's partitions
+    pub fn start_building(
+        self,
+        started_at: u64,
+    ) -> WantWithState<BuildingState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: BuildingState { started_at },
+        }
+    }
+
+    /// Transition from Idle to Canceled when want is explicitly canceled
+    pub fn cancel(
+        self,
+        canceled_by: Option<EventSource>,
+        comment: Option<String>,
+    ) -> WantWithState<CanceledState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: CanceledState {
+                canceled_at: current_timestamp(),
+                canceled_by,
+                comment,
+            },
+        }
+    }
+}
+
+// Type-safe transition methods for BuildingState
+impl WantWithState<BuildingState> {
+    /// Transition from Building to Successful when all partitions are built
+    pub fn complete(self, job_run_id: String, timestamp: u64) -> WantWithState<SuccessfulState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: SuccessfulState { completed_at: timestamp },
+        }
+    }
+
+    /// Transition from Building to Failed when a partition build fails
+    pub fn fail(self, failed_partition_refs: Vec<PartitionRef>, reason: String) -> WantWithState<FailedState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: FailedState {
+                failed_at: current_timestamp(),
+                failed_partition_refs,
+                failure_reason: reason,
+            },
+        }
+    }
+
+    /// Transition from Building to UpstreamBuilding when missing dependencies are detected
+    pub fn detect_missing_deps(
+        self,
+        upstream_want_ids: Vec<String>,
+    ) -> WantWithState<UpstreamBuildingState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: UpstreamBuildingState { upstream_want_ids },
+        }
+    }
+
+    /// Transition from Building to Canceled when want is explicitly canceled
+    pub fn cancel(
+        self,
+        source: Option<EventSource>,
+        timestamp: u64,
+        comment: Option<String>,
+    ) -> WantWithState<CanceledState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: CanceledState {
+                canceled_at: timestamp,
+                canceled_by: source,
+                comment,
+            },
+        }
+    }
+}
+
+// Type-safe transition methods for UpstreamBuildingState
+impl WantWithState<UpstreamBuildingState> {
+    /// Transition from UpstreamBuilding back to Idle when upstreams are satisfied
+    pub fn upstreams_satisfied(self) -> WantWithState<IdleState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: IdleState {},
+        }
+    }
+
+    /// Transition from UpstreamBuilding to UpstreamFailed when an upstream dependency fails
+    pub fn upstream_failed(
+        self,
+        failed_upstreams: Vec<String>,
+        timestamp: u64,
+    ) -> WantWithState<UpstreamFailedState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: UpstreamFailedState { failed_at: timestamp, failed_wants: failed_upstreams },
+        }
+    }
+
+    /// Transition from UpstreamBuilding to Canceled when want is explicitly canceled
+    pub fn cancel(
+        self,
+        source: Option<EventSource>,
+        timestamp: u64,
+        comment: Option<String>,
+    ) -> WantWithState<CanceledState> {
+        WantWithState {
+            want: self.want.updated_timestamp(),
+            state: CanceledState {
+                canceled_at: timestamp,
+                canceled_by: source,
+                comment,
+            },
+        }
+    }
+}
+
+// Helper methods on the Want enum
+impl Want {
+    /// Create a new want in the Idle state
+    pub fn new(
+        want_id: String,
+        partitions: Vec<PartitionRef>,
+        data_timestamp: u64,
+        ttl_seconds: u64,
+        sla_seconds: u64,
+        source: Option<EventSource>,
+        comment: Option<String>,
+    ) -> Self {
+        Want::Idle(WantWithState {
+            want: WantInfo {
+                want_id,
+                partitions,
+                upstreams: vec![],
+                data_timestamp,
+                ttl_seconds,
+                sla_seconds,
+                source,
+                comment,
+                last_updated_at: current_timestamp(),
+            },
+            state: IdleState {},
+        })
+    }
+
+    /// Check if want is schedulable (Idle or UpstreamBuilding with satisfied upstreams)
+    pub fn is_schedulable(&self) -> bool {
+        match self {
+            Want::Idle(_) => true,
+            // Note: upstream building shouldn't return true ever, it should go back to idle to
+            // be explicit about upstreams completing, which then makes it schedulable
+            _ => false,
+        }
+    }
+
+    /// Check if want is in a terminal state (Successful, Failed, UpstreamFailed, or Canceled)
+    pub fn is_terminal(&self) -> bool {
+        matches!(
+            self,
+            Want::Successful(_) | Want::Failed(_) | Want::UpstreamFailed(_) | Want::Canceled(_)
+        )
+    }
+
+    pub fn want(&self) -> &WantInfo {
+        match self {
+            Want::Idle(w) => &w.want,
+            Want::Building(w) => &w.want,
+            Want::UpstreamBuilding(w) => &w.want,
+            Want::Successful(w) => &w.want,
+            Want::Failed(w) => &w.want,
+            Want::UpstreamFailed(w) => &w.want,
+            Want::Canceled(w) => &w.want,
+        }
+    }
+
+    /// Convert to WantDetail for API responses and queries
+    pub fn to_detail(&self) -> WantDetail {
+        WantDetail {
+            want_id: self.want().want_id.clone(),
+            partitions: self.want().partitions.clone(),
+            upstreams: self.want().upstreams.clone(),
+            data_timestamp: self.want().data_timestamp,
+            ttl_seconds: self.want().ttl_seconds,
+            sla_seconds: self.want().sla_seconds,
+            source: self.want().source.clone(),
+            comment: self.want().comment.clone(),
+            last_updated_timestamp: self.want().last_updated_at,
+            status: match self {
+                Want::Idle(_) => Some(WantStatusCode::WantIdle.into()),
+                Want::Building(_) => Some(WantStatusCode::WantBuilding.into()),
+                Want::UpstreamBuilding(_) => Some(WantStatusCode::WantUpstreamBuilding.into()),
+                Want::Successful(_) => Some(WantStatusCode::WantSuccessful.into()),
+                Want::Failed(_) => Some(WantStatusCode::WantFailed.into()),
+                Want::UpstreamFailed(_) => Some(WantStatusCode::WantUpstreamFailed.into()),
+                Want::Canceled(_) => Some(WantStatusCode::WantCanceled.into()),
+            },
+        }
+    }
+}