diff --git a/crates/acp_thread/src/acp_thread.rs b/crates/acp_thread/src/acp_thread.rs
index 36c9fb40c4a573e09da05618a29c1898cced60ad..7fb48c132f971fd3449d116b22bd4437c1ebf611 100644
--- a/crates/acp_thread/src/acp_thread.rs
+++ b/crates/acp_thread/src/acp_thread.rs
@@ -1393,7 +1393,17 @@ impl AcpThread {
     ) -> Result<(), acp::Error> {
         match update {
             acp::SessionUpdate::UserMessageChunk(acp::ContentChunk { content, .. }) => {
-                self.push_user_content_block(None, content, cx);
+                // We optimistically add the full user prompt before calling `prompt`.
+                // Some ACP servers echo user chunks back over updates. Skip the chunk if
+                // it's already present in the current user message to avoid duplicating content.
+                let already_in_user_message = self
+                    .entries
+                    .last()
+                    .and_then(|entry| entry.user_message())
+                    .is_some_and(|message| message.chunks.contains(&content));
+                if !already_in_user_message {
+                    self.push_user_content_block(None, content, cx);
+                }
             }
             acp::SessionUpdate::AgentMessageChunk(acp::ContentChunk { content, .. }) => {
                 self.push_assistant_content_block(content, false, cx);
@@ -3440,6 +3450,52 @@ mod tests {
         );
     }
 
+    #[gpui::test]
+    async fn test_ignore_echoed_user_message_chunks_during_active_turn(
+        cx: &mut gpui::TestAppContext,
+    ) {
+        init_test(cx);
+
+        let fs = FakeFs::new(cx.executor());
+        let project = Project::test(fs, [], cx).await;
+        let connection = Rc::new(FakeAgentConnection::new().on_user_message(
+            |request, thread, mut cx| {
+                async move {
+                    let prompt = request.prompt.first().cloned().unwrap_or_else(|| "".into());
+
+                    thread.update(&mut cx, |thread, cx| {
+                        thread
+                            .handle_session_update(
+                                acp::SessionUpdate::UserMessageChunk(acp::ContentChunk::new(
+                                    prompt,
+                                )),
+                                cx,
+                            )
+                            .unwrap();
+                    })?;
+
+                    Ok(acp::PromptResponse::new(acp::StopReason::EndTurn))
+                }
+                .boxed_local()
+            },
+        ));
+
+        let thread = cx
+            .update(|cx| {
+                connection.new_session(project, PathList::new(&[Path::new(path!("/test"))]), cx)
+            })
+            .await
+            .unwrap();
+
+        thread
+            .update(cx, |thread, cx| thread.send_raw("Hello from Zed!", cx))
+            .await
+            .unwrap();
+
+        let output = thread.read_with(cx, |thread, cx| thread.to_markdown(cx));
+        assert_eq!(output.matches("Hello from Zed!").count(), 1);
+    }
+
     #[gpui::test]
     async fn test_edits_concurrently_to_user(cx: &mut TestAppContext) {
         init_test(cx);