diff --git a/lib/src/action.rs b/lib/src/action.rs
index d263a40..e828df0 100644
--- a/lib/src/action.rs
+++ b/lib/src/action.rs
@@ -1,28 +1,53 @@
 //! Processor responsible for receiving events, filtering them, and scheduling actions in response.
 
-use std::time::{Duration, Instant};
+use std::{
+	fmt,
+	sync::Arc,
+	time::{Duration, Instant},
+};
 
-use tokio::{sync::{mpsc, watch}, time::timeout};
+use atomic_take::AtomicTake;
+use tokio::{
+	sync::{mpsc, watch},
+	time::timeout,
+};
+use tracing::{debug, trace};
 
 use crate::{
 	error::{CriticalError, RuntimeError},
 	event::Event,
+	handler::{rte, Handler},
 };
 
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 #[non_exhaustive]
 pub struct WorkingData {
 	pub throttle: Duration,
+	pub action_handler: Arc<AtomicTake<Box<dyn Handler<Action> + Send>>>,
+}
+
+impl fmt::Debug for WorkingData {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		f.debug_struct("WorkingData")
+			.field("throttle", &self.throttle)
+			.finish_non_exhaustive()
+	}
 }
 
 impl Default for WorkingData {
 	fn default() -> Self {
 		Self {
 			throttle: Duration::from_millis(100),
+			action_handler: Arc::new(AtomicTake::new(Box::new(()) as _)),
 		}
 	}
 }
 
+#[derive(Clone, Debug)]
+pub struct Action {
+	pub events: Vec<Event>,
+}
+
 pub async fn worker(
 	working: watch::Receiver<WorkingData>,
 	errors: mpsc::Sender<RuntimeError>,
@@ -30,11 +55,13 @@ pub async fn worker(
 ) -> Result<(), CriticalError> {
 	let mut last = Instant::now();
 	let mut set = Vec::new();
+	let mut handler =
+		{ working.borrow().action_handler.take() }.ok_or(CriticalError::MissingHandler)?;
 
 	loop {
 		let maxtime = working.borrow().throttle;
 		match timeout(maxtime, events.recv()).await {
-			Err(_timeout) => {},
+			Err(_timeout) => {}
 			Ok(None) => break,
 			Ok(Some(event)) => {
 				set.push(event);
@@ -46,7 +73,21 @@ pub async fn worker(
 		}
 
 		last = Instant::now();
-		set.drain(..); // TODO: do action with the set
+
+		let action = Action {
+			events: set.drain(..).collect(),
+		};
+		debug!(?action, "action constructed");
+
+		if let Some(h) = working.borrow().action_handler.take() {
+			trace!("action handler updated");
+			handler = h;
+		}
+
+		let err = handler.handle(action).map_err(|e| rte("action worker", e));
+		if let Err(err) = err {
+			errors.send(err).await?;
+		}
 	}
 	Ok(())
 }
diff --git a/lib/src/error.rs b/lib/src/error.rs
index d3a247d..4150c70 100644
--- a/lib/src/error.rs
+++ b/lib/src/error.rs
@@ -33,6 +33,13 @@ pub enum CriticalError {
 	#[error("main task join: {0}")]
 	#[diagnostic(code(watchexec::critical::main_task_join))]
 	MainTaskJoin(#[source] JoinError),
+
+	/// Error received when a handler is missing on initialisation.
+	///
+	/// This is a critical bug and unlikely to be recoverable in any way.
+	#[error("internal: missing handler on init")]
+	#[diagnostic(code(watchexec::critical::internal::missing_handler))]
+	MissingHandler,
 }
 
 /// Errors which _may_ be recoverable, transient, or only affect a part of the operation, and should
@@ -112,15 +119,6 @@ pub enum RuntimeError {
 	Handler { ctx: &'static str, err: String },
 }
 
-impl RuntimeError {
-	pub(crate) fn from_handler(ctx: &'static str, err: impl std::error::Error) -> Self {
-		Self::Handler {
-			ctx,
-			err: err.to_string(),
-		}
-	}
-}
-
 /// Errors occurring from reconfigs.
 #[derive(Debug, Diagnostic, Error)]
 #[non_exhaustive]
diff --git a/lib/src/handler.rs b/lib/src/handler.rs
index 7d8ff68..a3ec39f 100644
--- a/lib/src/handler.rs
+++ b/lib/src/handler.rs
@@ -88,12 +88,21 @@ use std::{error::Error, future::Future, io::Write, marker::PhantomData};
 
 use tokio::runtime::Handle;
 
+use crate::error::RuntimeError;
+
 /// A callable that can be used to hook into watchexec.
 pub trait Handler<T> {
 	/// Call the handler with the given data.
 	fn handle(&mut self, _data: T) -> Result<(), Box<dyn Error>>;
 }
 
+pub(crate) fn rte(ctx: &'static str, err: Box<dyn Error>) -> RuntimeError {
+	RuntimeError::Handler {
+		ctx,
+		err: err.to_string(),
+	}
+}
+
 /// Wrapper for [`Handler`]s that are non-future [`FnMut`]s.
 ///
 /// Construct using [`Into::into`]:
diff --git a/lib/src/watchexec.rs b/lib/src/watchexec.rs
index 6586bf1..9ce5626 100644
--- a/lib/src/watchexec.rs
+++ b/lib/src/watchexec.rs
@@ -19,7 +19,7 @@ use crate::{
 	config::{InitConfig, RuntimeConfig},
 	error::{CriticalError, ReconfigError, RuntimeError},
 	fs,
-	handler::Handler,
+	handler::{rte, Handler},
 	signal,
 };
 
@@ -130,10 +130,7 @@ async fn error_hook(
 		if let Err(err) = handler.handle(err) {
 			error!(%err, "error while handling error");
 			handler
-				.handle(RuntimeError::Handler {
-					ctx: "error hook",
-					err: err.to_string(),
-				})
+				.handle(rte("error hook", err))
 				.unwrap_or_else(|err| {
 					error!(%err, "error while handling error of handling error");
 				});