diff --git a/src/bin/topola-egui/activity.rs b/src/bin/topola-egui/activity.rs
index 00f1969..51f58b8 100644
--- a/src/bin/topola-egui/activity.rs
+++ b/src/bin/topola-egui/activity.rs
@@ -15,18 +15,16 @@ use topola::{
     stepper::{Abort, Step},
 };
 
+pub struct ActivityContext<'a> {
+    pub invoker: &'a mut Invoker<SpecctraMesadata>,
+}
+
 #[derive(Debug, Clone)]
 pub enum ActivityStatus {
     Running,
     Finished(String),
 }
 
-#[derive(Error, Debug, Clone)]
-pub enum ActivityError {
-    #[error(transparent)]
-    Invoker(#[from] InvokerError),
-}
-
 impl From<InvokerStatus> for ActivityStatus {
     fn from(status: InvokerStatus) -> Self {
         match status {
@@ -46,26 +44,29 @@ impl TryInto<()> for ActivityStatus {
     }
 }
 
+#[derive(Error, Debug, Clone)]
+pub enum ActivityError {
+    #[error(transparent)]
+    Invoker(#[from] InvokerError),
+}
+
 pub enum ActivityStepper {
     // There will be another variant for interactive activities here soon. (TODO)
     Execution(ExecutionStepper),
 }
 
-impl Step<Invoker<SpecctraMesadata>, ActivityStatus, ActivityError, ()> for ActivityStepper {
-    fn step(
-        &mut self,
-        invoker: &mut Invoker<SpecctraMesadata>,
-    ) -> Result<ActivityStatus, ActivityError> {
+impl Step<ActivityContext<'_>, ActivityStatus, ActivityError, ()> for ActivityStepper {
+    fn step(&mut self, context: &mut ActivityContext) -> Result<ActivityStatus, ActivityError> {
         match self {
-            ActivityStepper::Execution(execution) => Ok(execution.step(invoker)?.into()),
+            ActivityStepper::Execution(execution) => Ok(execution.step(context.invoker)?.into()),
         }
     }
 }
 
-impl Abort<Invoker<SpecctraMesadata>> for ActivityStepper {
-    fn abort(&mut self, invoker: &mut Invoker<SpecctraMesadata>) {
+impl Abort<ActivityContext<'_>> for ActivityStepper {
+    fn abort(&mut self, context: &mut ActivityContext) {
         match self {
-            ActivityStepper::Execution(execution) => execution.finish(invoker), // TODO.
+            ActivityStepper::Execution(execution) => execution.finish(context.invoker), // TODO.
         };
     }
 }
@@ -124,23 +125,18 @@ impl ActivityStepperWithStatus {
     }
 }
 
-impl Step<Invoker<SpecctraMesadata>, ActivityStatus, ActivityError, ()>
-    for ActivityStepperWithStatus
-{
-    fn step(
-        &mut self,
-        invoker: &mut Invoker<SpecctraMesadata>,
-    ) -> Result<ActivityStatus, ActivityError> {
-        let status = self.activity.step(invoker)?;
+impl Step<ActivityContext<'_>, ActivityStatus, ActivityError, ()> for ActivityStepperWithStatus {
+    fn step(&mut self, context: &mut ActivityContext) -> Result<ActivityStatus, ActivityError> {
+        let status = self.activity.step(context)?;
         self.maybe_status = Some(status.clone());
         Ok(status.into())
     }
 }
 
-impl Abort<Invoker<SpecctraMesadata>> for ActivityStepperWithStatus {
-    fn abort(&mut self, invoker: &mut Invoker<SpecctraMesadata>) {
+impl Abort<ActivityContext<'_>> for ActivityStepperWithStatus {
+    fn abort(&mut self, context: &mut ActivityContext) {
         self.maybe_status = Some(ActivityStatus::Finished(String::from("aborted")));
-        self.activity.abort(invoker);
+        self.activity.abort(context);
     }
 }
 
diff --git a/src/bin/topola-egui/app.rs b/src/bin/topola-egui/app.rs
index 7b19027..359ff3a 100644
--- a/src/bin/topola-egui/app.rs
+++ b/src/bin/topola-egui/app.rs
@@ -19,7 +19,7 @@ use topola::{
 };
 
 use crate::{
-    activity::{ActivityStatus, ActivityStepperWithStatus},
+    activity::{ActivityContext, ActivityStatus, ActivityStepperWithStatus},
     config::Config,
     error_dialog::ErrorDialog,
     layers::Layers,
@@ -170,7 +170,7 @@ impl App {
             }
 
             if let Some(ref mut activity) = self.maybe_activity {
-                return match activity.step(invoker) {
+                return match activity.step(&mut ActivityContext { invoker }) {
                     Ok(ActivityStatus::Running) => true,
                     Ok(ActivityStatus::Finished(..)) => false,
                     Err(err) => {
diff --git a/src/bin/topola-egui/menu_bar.rs b/src/bin/topola-egui/menu_bar.rs
index 470cb5d..f545197 100644
--- a/src/bin/topola-egui/menu_bar.rs
+++ b/src/bin/topola-egui/menu_bar.rs
@@ -20,7 +20,7 @@ use topola::{
 
 use crate::{
     action::{Action, Switch, Trigger},
-    activity::{ActivityStatus, ActivityStepperWithStatus},
+    activity::{ActivityContext, ActivityStatus, ActivityStepperWithStatus},
     app::{execute, handle_file},
     overlay::Overlay,
     translator::Translator,
@@ -331,7 +331,7 @@ impl MenuBar {
                 } else if abort.consume_key_triggered(ctx, ui) {
                     if let Some(activity) = maybe_activity {
                         if let Some(invoker) = arc_mutex_maybe_invoker.lock().unwrap().as_mut() {
-                            activity.abort(invoker);
+                            activity.abort(&mut ActivityContext { invoker });
                         }
                     }
                 } else if remove_bands.consume_key_triggered(ctx, ui) {