diff --git a/arroyo-datastream/src/lib.rs b/arroyo-datastream/src/lib.rs
index dc90b76c5..18b827b0a 100644
--- a/arroyo-datastream/src/lib.rs
+++ b/arroyo-datastream/src/lib.rs
@@ -1363,7 +1363,7 @@ impl Program {
                             let gap = duration_to_syn_expr(*gap);
                             quote! {
                                 Box::new(SessionWindowFunc::<#in_k, #in_t, #out_t>::new(
-                                    #gap, #agg
+                                    #agg, #gap
                                 ))
                             }
                         }
diff --git a/arroyo-sql-testing/src/full_query_tests.rs b/arroyo-sql-testing/src/full_query_tests.rs
index cad747101..85e1a4fa5 100644
--- a/arroyo-sql-testing/src/full_query_tests.rs
+++ b/arroyo-sql-testing/src/full_query_tests.rs
@@ -135,8 +135,7 @@ full_pipeline_codegen! {"cast_bug",
 "SELECT CAST(1 as FLOAT)
 from nexmark; "}
 
-/* full_pipeline_codegen! {"session_window",
-"SELECT count(*), session(INTERVAL '2' SECOND, INTERVAL '10' SECOND) AS window
+full_pipeline_codegen! {"session_window",
+"SELECT count(*), session(INTERVAL '10' SECOND) AS window
 from nexmark
 group by window, auction.id; "}
- */
diff --git a/arroyo-sql/src/lib.rs b/arroyo-sql/src/lib.rs
index 9b9c708df..fbcb4e97a 100644
--- a/arroyo-sql/src/lib.rs
+++ b/arroyo-sql/src/lib.rs
@@ -90,6 +90,16 @@ impl ArroyoSchemaProvider {
             Arc::new(create_udf(
                 "tumble",
                 vec![DataType::Interval(datatypes::IntervalUnit::MonthDayNano)],
+                window_return_type.clone(),
+                Volatility::Volatile,
+                make_scalar_function(fn_impl),
+            )),
+        );
+        functions.insert(
+            "session".to_string(),
+            Arc::new(create_udf(
+                "session",
+                vec![DataType::Interval(datatypes::IntervalUnit::MonthDayNano)],
                 window_return_type,
                 Volatility::Volatile,
                 make_scalar_function(fn_impl),
diff --git a/arroyo-sql/src/pipeline.rs b/arroyo-sql/src/pipeline.rs
index 666f8eae6..f88dccf44 100644
--- a/arroyo-sql/src/pipeline.rs
+++ b/arroyo-sql/src/pipeline.rs
@@ -670,7 +670,7 @@ impl<'a> SqlPipelineBuilder<'a> {
     fn is_window(expression: &Expr) -> bool {
         match expression {
             Expr::ScalarUDF(ScalarUDF { fun, args: _ }) => {
-                matches!(fun.name.as_str(), "hop" | "tumble")
+                matches!(fun.name.as_str(), "hop" | "tumble" | "session")
             }
             Expr::Alias(datafusion_expr::expr::Alias { expr, name: _ }) => Self::is_window(expr),
             _ => false,
@@ -695,6 +695,13 @@ impl<'a> SqlPipelineBuilder<'a> {
                     let width = Self::get_duration(&args[0])?;
                     Ok(Some(WindowType::Tumbling { width }))
                 }
+                "session" => {
+                    if args.len() != 1 {
+                        unreachable!("wrong number of arguments for session(), expected one");
+                    }
+                    let gap = Self::get_duration(&args[0])?;
+                    Ok(Some(WindowType::Session { gap }))
+                }
                 _ => Ok(None),
             },
             Expr::Alias(datafusion_expr::expr::Alias { expr, name: _ }) => Self::find_window(expr),
diff --git a/arroyo-state/src/tables.rs b/arroyo-state/src/tables.rs
index 0dd4bc77c..7ae62baa3 100644
--- a/arroyo-state/src/tables.rs
+++ b/arroyo-state/src/tables.rs
@@ -502,10 +502,10 @@ impl<'a, K: Key, V: Data, S: BackingStore> KeyedState<'a, K, V, S> {
         self.cache.insert(key, wrapped.unwrap());
     }
 
-    pub async fn remove(&mut self, mut key: K) {
+    pub async fn remove(&mut self, key: &mut K) {
         self.cache.remove(&key);
         self.backing_state
-            .write_key_value::<K, Option<V>>(self.table, &mut key, &mut None)
+            .write_key_value::<K, Option<V>>(self.table, key, &mut None)
             .await;
     }
 
diff --git a/arroyo-types/src/lib.rs b/arroyo-types/src/lib.rs
index 5e34b0f72..2289244ef 100644
--- a/arroyo-types/src/lib.rs
+++ b/arroyo-types/src/lib.rs
@@ -32,7 +32,7 @@ impl Window {
     }
 
     pub fn contains(&self, t: SystemTime) -> bool {
-        self.start >= t && t < self.end
+        self.start <= t && t < self.end
     }
 }
 
diff --git a/arroyo-worker/src/operators/mod.rs b/arroyo-worker/src/operators/mod.rs
index cf71b6bc6..29a3e9fc7 100644
--- a/arroyo-worker/src/operators/mod.rs
+++ b/arroyo-worker/src/operators/mod.rs
@@ -221,7 +221,10 @@ impl<K: Key, D: Data> PeriodicWatermarkGenerator<K, D> {
     async fn handle_tick(&mut self, _: u64, ctx: &mut Context<K, D>) {
         if let Some(idle_time) = self.idle_time {
             if self.last_event.elapsed().unwrap_or(Duration::ZERO) > idle_time && !self.idle {
-                info!("Setting partition {} to idle", ctx.task_info.task_index);
+                info!(
+                    "Setting partition {} to idle after {:?}",
+                    ctx.task_info.task_index, idle_time
+                );
                 ctx.broadcast(Message::Watermark(Watermark::Idle)).await;
                 self.idle = true;
             }
diff --git a/arroyo-worker/src/operators/updating_aggregate.rs b/arroyo-worker/src/operators/updating_aggregate.rs
index 51fcf73dc..bff0d24f3 100644
--- a/arroyo-worker/src/operators/updating_aggregate.rs
+++ b/arroyo-worker/src/operators/updating_aggregate.rs
@@ -130,7 +130,7 @@ impl<K: Key, T: Data, BinA: Data, OutT: Data> UpdatingAggregateOperator<K, T, Bi
                         .await;
                 }
                 StateOp::Delete => {
-                    aggregating_map.remove(mut_key).await;
+                    aggregating_map.remove(&mut mut_key).await;
                 }
                 StateOp::Update { new, old: _ } => {
                     aggregating_map.insert(record.timestamp, mut_key, new).await;
diff --git a/arroyo-worker/src/operators/windows.rs b/arroyo-worker/src/operators/windows.rs
index 82a591744..46196eed8 100644
--- a/arroyo-worker/src/operators/windows.rs
+++ b/arroyo-worker/src/operators/windows.rs
@@ -205,7 +205,7 @@ impl<K: Key, T: Data, OutT: Data> SessionWindowFunc<K, T, OutT> {
         "SessionWindow".to_string()
     }
 
-    pub async fn new(operation: WindowOperation<K, T, OutT>, gap_size: Duration) -> Self {
+    pub fn new(operation: WindowOperation<K, T, OutT>, gap_size: Duration) -> Self {
         Self {
             operation,
             gap_size,
@@ -299,10 +299,10 @@ impl<K: Key, T: Data, OutT: Data> SessionWindowFunc<K, T, OutT> {
         };
 
         if let Some(remove) = remove {
-            let _: Option<SystemTime> = ctx.cancel_timer(&mut key, remove).await;
+            let _: Option<Window> = ctx.cancel_timer(&mut key, remove).await;
         }
         if let Some(add) = add {
-            // we use UNIX_EPOCH as the start of our windows to aovid having to update them when we extend
+            // we use UNIX_EPOCH as the start of our windows to avoid having to update them when we extend
             // the beginning; this works because windows are always handled in order
             ctx.schedule_timer(&mut key, add, Window::new(SystemTime::UNIX_EPOCH, add))
                 .await;
@@ -326,6 +326,33 @@ impl<K: Key, T: Data, OutT: Data> SessionWindowFunc<K, T, OutT> {
     }
 
     async fn handle_timer(&mut self, mut key: K, window: Window, ctx: &mut Context<K, OutT>) {
+        println!("Handling timer for {:?}, {:?}", key, window);
+        let window = {
+            // get the actual window (as the timer one doesn't have the actual start time)
+            let mut t: KeyedState<'_, K, Vec<Window>, _> = ctx.state.get_key_state('s').await;
+            let mut windows: Vec<Window> = t
+                .get(&key)
+                .map(|t| t.iter().map(|w| *w).collect())
+                .expect("there must be a window for this key in state");
+
+            let window = *windows
+                .iter()
+                .find(|w| w.end == window.end)
+                .expect("this window must be in state");
+
+            windows.retain(|w| w.end != window.end);
+
+            if windows.is_empty() {
+                t.remove(&mut key).await;
+            } else {
+                let key = key.clone();
+                t.insert(windows.iter().map(|w| w.end).max().unwrap(), key, windows)
+                    .await;
+            }
+
+            window
+        };
+
         self.operation.operate(&mut key, window, 'w', ctx).await;
 
         // clear this window and everything before it -- we're guaranteed that windows are executed in order and are
@@ -335,20 +362,5 @@ impl<K: Key, T: Data, OutT: Data> SessionWindowFunc<K, T, OutT> {
         state
             .clear_time_range(&mut key, window.start, window.end)
             .await;
-
-        let mut t: KeyedState<'_, K, Vec<Window>, _> = ctx.state.get_key_state('s').await;
-        let mut windows: Vec<Window> = t
-            .get(&key)
-            .map(|t| t.iter().map(|w| *w).collect())
-            .expect("there must be a window for this key in state");
-
-        windows.retain(|w| w.end != window.end);
-
-        if windows.is_empty() {
-            t.remove(key).await;
-        } else {
-            t.insert(windows.iter().map(|w| w.end).max().unwrap(), key, windows)
-                .await;
-        }
     }
 }