diff --git a/crates/agent/src/active_thread.rs b/crates/agent/src/active_thread.rs
index e704a4630f054ae340f5b6d9df6a118a4e6362df..0454a2772d758fe1bfd928027a5f760636088081 100644
--- a/crates/agent/src/active_thread.rs
+++ b/crates/agent/src/active_thread.rs
@@ -1241,6 +1241,9 @@ impl ActiveThread {
             return;
         };
 
+        // Cancel any ongoing streaming when user starts editing a previous message
+        self.cancel_last_completion(window, cx);
+
         let editor = crate::message_editor::create_editor(
             self.workspace.clone(),
             self.context_store.downgrade(),
@@ -3464,3 +3467,146 @@ fn open_editor_at_position(
         }
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use assistant_tool::{ToolRegistry, ToolWorkingSet};
+    use context_server::ContextServerSettings;
+    use editor::EditorSettings;
+    use fs::FakeFs;
+    use gpui::{TestAppContext, VisualTestContext};
+    use language_model::{LanguageModel, fake_provider::FakeLanguageModel};
+    use project::Project;
+    use prompt_store::PromptBuilder;
+    use serde_json::json;
+    use settings::SettingsStore;
+    use util::path;
+
+    use crate::{ContextLoadResult, thread_store};
+
+    use super::*;
+
+    #[gpui::test]
+    async fn test_current_completion_cancelled_when_message_edited(cx: &mut TestAppContext) {
+        init_test_settings(cx);
+
+        let project = create_test_project(
+            cx,
+            json!({"code.rs": "fn main() {\n    println!(\"Hello, world!\");\n}"}),
+        )
+        .await;
+
+        let (cx, active_thread, thread, model) = setup_test_environment(cx, project.clone()).await;
+
+        // Insert user message without any context (empty context vector)
+        let message = thread.update(cx, |thread, cx| {
+            let message_id = thread.insert_user_message(
+                "What is the best way to learn Rust?",
+                ContextLoadResult::default(),
+                None,
+                vec![],
+                cx,
+            );
+            thread
+                .message(message_id)
+                .expect("message should exist")
+                .clone()
+        });
+
+        // Stream response to user message
+        thread.update(cx, |thread, cx| {
+            let request = thread.to_completion_request(model.clone(), cx);
+            thread.stream_completion(request, model, cx.active_window(), cx)
+        });
+        let generating = thread.update(cx, |thread, _cx| thread.is_generating());
+        assert!(generating, "There should be one pending completion");
+
+        // Edit the previous message
+        active_thread.update_in(cx, |active_thread, window, cx| {
+            active_thread.start_editing_message(message.id, &message.segments, window, cx);
+        });
+
+        // Check that the stream was cancelled
+        let generating = thread.update(cx, |thread, _cx| thread.is_generating());
+        assert!(!generating, "The completion should have been cancelled");
+    }
+
+    fn init_test_settings(cx: &mut TestAppContext) {
+        cx.update(|cx| {
+            let settings_store = SettingsStore::test(cx);
+            cx.set_global(settings_store);
+            language::init(cx);
+            Project::init_settings(cx);
+            AssistantSettings::register(cx);
+            prompt_store::init(cx);
+            thread_store::init(cx);
+            workspace::init_settings(cx);
+            language_model::init_settings(cx);
+            ThemeSettings::register(cx);
+            ContextServerSettings::register(cx);
+            EditorSettings::register(cx);
+            ToolRegistry::default_global(cx);
+        });
+    }
+
+    // Helper to create a test project with test files
+    async fn create_test_project(
+        cx: &mut TestAppContext,
+        files: serde_json::Value,
+    ) -> Entity<Project> {
+        let fs = FakeFs::new(cx.executor());
+        fs.insert_tree(path!("/test"), files).await;
+        Project::test(fs, [path!("/test").as_ref()], cx).await
+    }
+
+    async fn setup_test_environment(
+        cx: &mut TestAppContext,
+        project: Entity<Project>,
+    ) -> (
+        &mut VisualTestContext,
+        Entity<ActiveThread>,
+        Entity<Thread>,
+        Arc<dyn LanguageModel>,
+    ) {
+        let (workspace, cx) =
+            cx.add_window_view(|window, cx| Workspace::test_new(project.clone(), window, cx));
+
+        let thread_store = cx
+            .update(|_, cx| {
+                ThreadStore::load(
+                    project.clone(),
+                    cx.new(|_| ToolWorkingSet::default()),
+                    None,
+                    Arc::new(PromptBuilder::new(None).unwrap()),
+                    cx,
+                )
+            })
+            .await
+            .unwrap();
+
+        let thread = thread_store.update(cx, |store, cx| store.create_thread(cx));
+        let context_store = cx.new(|_cx| ContextStore::new(project.downgrade(), None));
+
+        let model = FakeLanguageModel::default();
+        let model: Arc<dyn LanguageModel> = Arc::new(model);
+
+        let language_registry = LanguageRegistry::new(cx.executor());
+        let language_registry = Arc::new(language_registry);
+
+        let active_thread = cx.update(|window, cx| {
+            cx.new(|cx| {
+                ActiveThread::new(
+                    thread.clone(),
+                    thread_store.clone(),
+                    context_store.clone(),
+                    language_registry.clone(),
+                    workspace.downgrade(),
+                    window,
+                    cx,
+                )
+            })
+        });
+
+        (cx, active_thread, thread, model)
+    }
+}