diff --git a/crates/agent_ui/src/acp/message_history.rs b/crates/agent_ui/src/acp/message_history.rs
index d0fb1f09908f5505f94777b68b59e18df715c2c4..c6106c7578230e60576cdeb48318012b52e76e46 100644
--- a/crates/agent_ui/src/acp/message_history.rs
+++ b/crates/agent_ui/src/acp/message_history.rs
@@ -45,6 +45,11 @@ impl<T> MessageHistory<T> {
             None
         })
     }
+
+    #[cfg(test)]
+    pub fn items(&self) -> &[T] {
+        &self.items
+    }
 }
 #[cfg(test)]
 mod tests {
diff --git a/crates/agent_ui/src/acp/thread_view.rs b/crates/agent_ui/src/acp/thread_view.rs
index 5c6ae091cd6ff85375005176ac5ff4fd07d3bdbd..ff6da432994e4e57a51c2713bb834bedad0b1673 100644
--- a/crates/agent_ui/src/acp/thread_view.rs
+++ b/crates/agent_ui/src/acp/thread_view.rs
@@ -381,6 +381,11 @@ impl AcpThreadView {
             editor.display_map.update(cx, |map, cx| {
                 let snapshot = map.snapshot(cx);
                 for (crease_id, crease) in snapshot.crease_snapshot.creases() {
+                    // Skip creases that have been edited out of the message buffer.
+                    if !crease.range().start.is_valid(&snapshot.buffer_snapshot) {
+                        continue;
+                    }
+
                     if let Some(project_path) =
                         self.mention_set.lock().path_for_crease_id(crease_id)
                     {
@@ -2898,8 +2903,12 @@ mod tests {
     use fs::FakeFs;
     use futures::future::try_join_all;
     use gpui::{SemanticVersion, TestAppContext, VisualTestContext};
+    use lsp::{CompletionContext, CompletionTriggerKind};
+    use project::CompletionIntent;
     use rand::Rng;
+    use serde_json::json;
     use settings::SettingsStore;
+    use util::path;
 
     use super::*;
 
@@ -3011,6 +3020,109 @@ mod tests {
         );
     }
 
+    #[gpui::test]
+    async fn test_crease_removal(cx: &mut TestAppContext) {
+        init_test(cx);
+
+        let fs = FakeFs::new(cx.executor());
+        fs.insert_tree("/project", json!({"file": ""})).await;
+        let project = Project::test(fs, [Path::new(path!("/project"))], cx).await;
+        let agent = StubAgentServer::default();
+        let (workspace, cx) =
+            cx.add_window_view(|window, cx| Workspace::test_new(project.clone(), window, cx));
+        let thread_view = cx.update(|window, cx| {
+            cx.new(|cx| {
+                AcpThreadView::new(
+                    Rc::new(agent),
+                    workspace.downgrade(),
+                    project,
+                    Rc::new(RefCell::new(MessageHistory::default())),
+                    1,
+                    None,
+                    window,
+                    cx,
+                )
+            })
+        });
+
+        cx.run_until_parked();
+
+        let message_editor = cx.read(|cx| thread_view.read(cx).message_editor.clone());
+        let excerpt_id = message_editor.update(cx, |editor, cx| {
+            editor
+                .buffer()
+                .read(cx)
+                .excerpt_ids()
+                .into_iter()
+                .next()
+                .unwrap()
+        });
+        let completions = message_editor.update_in(cx, |editor, window, cx| {
+            editor.set_text("Hello @", window, cx);
+            let buffer = editor.buffer().read(cx).as_singleton().unwrap();
+            let completion_provider = editor.completion_provider().unwrap();
+            completion_provider.completions(
+                excerpt_id,
+                &buffer,
+                Anchor::MAX,
+                CompletionContext {
+                    trigger_kind: CompletionTriggerKind::TRIGGER_CHARACTER,
+                    trigger_character: Some("@".into()),
+                },
+                window,
+                cx,
+            )
+        });
+        let [_, completion]: [_; 2] = completions
+            .await
+            .unwrap()
+            .into_iter()
+            .flat_map(|response| response.completions)
+            .collect::<Vec<_>>()
+            .try_into()
+            .unwrap();
+
+        message_editor.update_in(cx, |editor, window, cx| {
+            let snapshot = editor.buffer().read(cx).snapshot(cx);
+            let start = snapshot
+                .anchor_in_excerpt(excerpt_id, completion.replace_range.start)
+                .unwrap();
+            let end = snapshot
+                .anchor_in_excerpt(excerpt_id, completion.replace_range.end)
+                .unwrap();
+            editor.edit([(start..end, completion.new_text)], cx);
+            (completion.confirm.unwrap())(CompletionIntent::Complete, window, cx);
+        });
+
+        cx.run_until_parked();
+
+        // Backspace over the inserted crease (and the following space).
+        message_editor.update_in(cx, |editor, window, cx| {
+            editor.backspace(&Default::default(), window, cx);
+            editor.backspace(&Default::default(), window, cx);
+        });
+
+        thread_view.update_in(cx, |thread_view, window, cx| {
+            thread_view.chat(&Chat, window, cx);
+        });
+
+        cx.run_until_parked();
+
+        let content = thread_view.update_in(cx, |thread_view, _window, _cx| {
+            thread_view
+                .message_history
+                .borrow()
+                .items()
+                .iter()
+                .flatten()
+                .cloned()
+                .collect::<Vec<_>>()
+        });
+
+        // We don't send a resource link for the deleted crease.
+        pretty_assertions::assert_matches!(content.as_slice(), [acp::ContentBlock::Text { .. }]);
+    }
+
     async fn setup_thread_view(
         agent: impl AgentServer + 'static,
         cx: &mut TestAppContext,
diff --git a/crates/editor/src/editor.rs b/crates/editor/src/editor.rs
index 677acd9fd8f0a0592652f5a31f226fd2339bdc31..bd7963a2e2ee448e876a59ba8948182cf8a2ca48 100644
--- a/crates/editor/src/editor.rs
+++ b/crates/editor/src/editor.rs
@@ -2705,6 +2705,11 @@ impl Editor {
         self.completion_provider = provider;
     }
 
+    #[cfg(any(test, feature = "test-support"))]
+    pub fn completion_provider(&self) -> Option<Rc<dyn CompletionProvider>> {
+        self.completion_provider.clone()
+    }
+
     pub fn semantics_provider(&self) -> Option<Rc<dyn SemanticsProvider>> {
         self.semantics_provider.clone()
     }