acp-native-rewind

Cargo.lock

@@ -191,9 +191,7 @@ dependencies = [
 
 [[package]]
 name = "agent-client-protocol"
-version = "0.0.31"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "289eb34ee17213dadcca47eedadd386a5e7678094095414e475965d1bcca2860"
+version = "0.0.32"
 dependencies = [
  "anyhow",
  "async-broadcast",

Cargo.toml

@@ -426,7 +426,7 @@ zlog_settings = { path = "crates/zlog_settings" }
 # External crates
 #
 
-agent-client-protocol = "0.0.31"
+agent-client-protocol = { path = "../agent-client-protocol"}
 aho-corasick = "1.1"
 alacritty_terminal = { git = "https://github.com/zed-industries/alacritty.git", branch = "add-hush-login-flag" }
 any_vec = "0.14"

crates/acp_thread/src/acp_thread.rs

@@ -32,10 +32,15 @@ use std::time::{Duration, Instant};
 use std::{fmt::Display, mem, path::PathBuf, sync::Arc};
 use ui::App;
 use util::ResultExt;
+use uuid::Uuid;
+
+pub fn new_prompt_id() -> acp::PromptId {
+    acp::PromptId(Uuid::new_v4().to_string().into())
+}
 
 #[derive(Debug)]
 pub struct UserMessage {
-    pub id: Option<UserMessageId>,
+    pub prompt_id: Option<acp::PromptId>,
     pub content: ContentBlock,
     pub chunks: Vec<acp::ContentBlock>,
     pub checkpoint: Option<Checkpoint>,
@@ -962,7 +967,7 @@ impl AcpThread {
 
     pub fn push_user_content_block(
         &mut self,
-        message_id: Option<UserMessageId>,
+        prompt_id: Option<acp::PromptId>,
         chunk: acp::ContentBlock,
         cx: &mut Context<Self>,
     ) {
@@ -971,13 +976,13 @@ impl AcpThread {
 
         if let Some(last_entry) = self.entries.last_mut()
             && let AgentThreadEntry::UserMessage(UserMessage {
-                id,
+                prompt_id: id,
                 content,
                 chunks,
                 ..
             }) = last_entry
         {
-            *id = message_id.or(id.take());
+            *id = prompt_id.or(id.take());
             content.append(chunk.clone(), &language_registry, cx);
             chunks.push(chunk);
             let idx = entries_len - 1;
@@ -986,7 +991,7 @@ impl AcpThread {
             let content = ContentBlock::new(chunk.clone(), &language_registry, cx);
             self.push_entry(
                 AgentThreadEntry::UserMessage(UserMessage {
-                    id: message_id,
+                    prompt_id,
                     content,
                     chunks: vec![chunk],
                     checkpoint: None,
@@ -1336,6 +1341,7 @@ impl AcpThread {
         cx: &mut Context<Self>,
     ) -> BoxFuture<'static, Result<()>> {
         self.send(
+            new_prompt_id(),
             vec![acp::ContentBlock::Text(acp::TextContent {
                 text: message.to_string(),
                 annotations: None,
@@ -1346,6 +1352,7 @@ impl AcpThread {
 
     pub fn send(
         &mut self,
+        prompt_id: acp::PromptId,
         message: Vec<acp::ContentBlock>,
         cx: &mut Context<Self>,
     ) -> BoxFuture<'static, Result<()>> {
@@ -1355,22 +1362,17 @@ impl AcpThread {
             cx,
         );
         let request = acp::PromptRequest {
+            prompt_id: Some(prompt_id.clone()),
             prompt: message.clone(),
             session_id: self.session_id.clone(),
         };
         let git_store = self.project.read(cx).git_store().clone();
 
-        let message_id = if self.connection.truncate(&self.session_id, cx).is_some() {
-            Some(UserMessageId::new())
-        } else {
-            None
-        };
-
         self.run_turn(cx, async move |this, cx| {
             this.update(cx, |this, cx| {
                 this.push_entry(
                     AgentThreadEntry::UserMessage(UserMessage {
-                        id: message_id.clone(),
+                        prompt_id: Some(prompt_id),
                         content: block,
                         chunks: message,
                         checkpoint: None,
@@ -1392,7 +1394,7 @@ impl AcpThread {
                         show: false,
                     });
                 }
-                this.connection.prompt(message_id, request, cx)
+                this.connection.prompt(request, cx)
             })?
             .await
         })
@@ -1509,8 +1511,8 @@ impl AcpThread {
 
     /// Rewinds this thread to before the entry at `index`, removing it and all
     /// subsequent entries while reverting any changes made from that point.
-    pub fn rewind(&mut self, id: UserMessageId, cx: &mut Context<Self>) -> Task<Result<()>> {
-        let Some(truncate) = self.connection.truncate(&self.session_id, cx) else {
+    pub fn rewind(&mut self, id: acp::PromptId, cx: &mut Context<Self>) -> Task<Result<()>> {
+        let Some(rewind) = self.connection.rewind(&self.session_id, cx) else {
             return Task::ready(Err(anyhow!("not supported")));
         };
         let Some(message) = self.user_message(&id) else {
@@ -1530,7 +1532,7 @@ impl AcpThread {
                     .await?;
             }
 
-            cx.update(|cx| truncate.run(id.clone(), cx))?.await?;
+            cx.update(|cx| rewind.rewind(id.clone(), cx))?.await?;
             this.update(cx, |this, cx| {
                 if let Some((ix, _)) = this.user_message_mut(&id) {
                     let range = ix..this.entries.len();
@@ -1594,10 +1596,10 @@ impl AcpThread {
             })
     }
 
-    fn user_message(&self, id: &UserMessageId) -> Option<&UserMessage> {
+    fn user_message(&self, id: &acp::PromptId) -> Option<&UserMessage> {
         self.entries.iter().find_map(|entry| {
             if let AgentThreadEntry::UserMessage(message) = entry {
-                if message.id.as_ref() == Some(id) {
+                if message.prompt_id.as_ref() == Some(id) {
                     Some(message)
                 } else {
                     None
@@ -1608,10 +1610,10 @@ impl AcpThread {
         })
     }
 
-    fn user_message_mut(&mut self, id: &UserMessageId) -> Option<(usize, &mut UserMessage)> {
+    fn user_message_mut(&mut self, id: &acp::PromptId) -> Option<(usize, &mut UserMessage)> {
         self.entries.iter_mut().enumerate().find_map(|(ix, entry)| {
             if let AgentThreadEntry::UserMessage(message) = entry {
-                if message.id.as_ref() == Some(id) {
+                if message.prompt_id.as_ref() == Some(id) {
                     Some((ix, message))
                 } else {
                     None
@@ -1905,7 +1907,7 @@ mod tests {
         thread.update(cx, |thread, cx| {
             assert_eq!(thread.entries.len(), 1);
             if let AgentThreadEntry::UserMessage(user_msg) = &thread.entries[0] {
-                assert_eq!(user_msg.id, None);
+                assert_eq!(user_msg.prompt_id, None);
                 assert_eq!(user_msg.content.to_markdown(cx), "Hello, ");
             } else {
                 panic!("Expected UserMessage");
@@ -1913,7 +1915,7 @@ mod tests {
         });
 
         // Test appending to existing user message
-        let message_1_id = UserMessageId::new();
+        let message_1_id = new_prompt_id();
         thread.update(cx, |thread, cx| {
             thread.push_user_content_block(
                 Some(message_1_id.clone()),
@@ -1928,7 +1930,7 @@ mod tests {
         thread.update(cx, |thread, cx| {
             assert_eq!(thread.entries.len(), 1);
             if let AgentThreadEntry::UserMessage(user_msg) = &thread.entries[0] {
-                assert_eq!(user_msg.id, Some(message_1_id));
+                assert_eq!(user_msg.prompt_id, Some(message_1_id));
                 assert_eq!(user_msg.content.to_markdown(cx), "Hello, world!");
             } else {
                 panic!("Expected UserMessage");
@@ -1947,7 +1949,7 @@ mod tests {
             );
         });
 
-        let message_2_id = UserMessageId::new();
+        let message_2_id = new_prompt_id();
         thread.update(cx, |thread, cx| {
             thread.push_user_content_block(
                 Some(message_2_id.clone()),
@@ -1962,7 +1964,7 @@ mod tests {
         thread.update(cx, |thread, cx| {
             assert_eq!(thread.entries.len(), 3);
             if let AgentThreadEntry::UserMessage(user_msg) = &thread.entries[2] {
-                assert_eq!(user_msg.id, Some(message_2_id));
+                assert_eq!(user_msg.prompt_id, Some(message_2_id));
                 assert_eq!(user_msg.content.to_markdown(cx), "New user message");
             } else {
                 panic!("Expected UserMessage at index 2");
@@ -2259,9 +2261,13 @@ mod tests {
             .await
             .unwrap();
 
-        cx.update(|cx| thread.update(cx, |thread, cx| thread.send(vec!["Hi".into()], cx)))
-            .await
-            .unwrap();
+        cx.update(|cx| {
+            thread.update(cx, |thread, cx| {
+                thread.send(new_prompt_id(), vec!["Hi".into()], cx)
+            })
+        })
+        .await
+        .unwrap();
 
         assert!(cx.read(|cx| !thread.read(cx).has_pending_edit_tool_calls()));
     }
@@ -2320,9 +2326,13 @@ mod tests {
             .await
             .unwrap();
 
-        cx.update(|cx| thread.update(cx, |thread, cx| thread.send(vec!["Lorem".into()], cx)))
-            .await
-            .unwrap();
+        cx.update(|cx| {
+            thread.update(cx, |thread, cx| {
+                thread.send(new_prompt_id(), vec!["Lorem".into()], cx)
+            })
+        })
+        .await
+        .unwrap();
         thread.read_with(cx, |thread, cx| {
             assert_eq!(
                 thread.to_markdown(cx),
@@ -2340,9 +2350,13 @@ mod tests {
         });
         assert_eq!(fs.files(), vec![Path::new(path!("/test/file-0"))]);
 
-        cx.update(|cx| thread.update(cx, |thread, cx| thread.send(vec!["ipsum".into()], cx)))
-            .await
-            .unwrap();
+        cx.update(|cx| {
+            thread.update(cx, |thread, cx| {
+                thread.send(new_prompt_id(), vec!["ipsum".into()], cx)
+            })
+        })
+        .await
+        .unwrap();
         thread.read_with(cx, |thread, cx| {
             assert_eq!(
                 thread.to_markdown(cx),
@@ -2376,9 +2390,13 @@ mod tests {
 
         // Checkpoint isn't stored when there are no changes.
         simulate_changes.store(false, SeqCst);
-        cx.update(|cx| thread.update(cx, |thread, cx| thread.send(vec!["dolor".into()], cx)))
-            .await
-            .unwrap();
+        cx.update(|cx| {
+            thread.update(cx, |thread, cx| {
+                thread.send(new_prompt_id(), vec!["dolor".into()], cx)
+            })
+        })
+        .await
+        .unwrap();
         thread.read_with(cx, |thread, cx| {
             assert_eq!(
                 thread.to_markdown(cx),
@@ -2424,7 +2442,7 @@ mod tests {
                 let AgentThreadEntry::UserMessage(message) = &thread.entries[2] else {
                     panic!("unexpected entries {:?}", thread.entries)
                 };
-                thread.rewind(message.id.clone().unwrap(), cx)
+                thread.rewind(message.prompt_id.clone().unwrap(), cx)
             })
             .await
             .unwrap();
@@ -2490,9 +2508,13 @@ mod tests {
             .await
             .unwrap();
 
-        cx.update(|cx| thread.update(cx, |thread, cx| thread.send(vec!["hello".into()], cx)))
-            .await
-            .unwrap();
+        cx.update(|cx| {
+            thread.update(cx, |thread, cx| {
+                thread.send(new_prompt_id(), vec!["hello".into()], cx)
+            })
+        })
+        .await
+        .unwrap();
         thread.read_with(cx, |thread, cx| {
             assert_eq!(
                 thread.to_markdown(cx),
@@ -2512,9 +2534,13 @@ mod tests {
         // Simulate refusing the second message, ensuring the conversation gets
         // truncated to before sending it.
         refuse_next.store(true, SeqCst);
-        cx.update(|cx| thread.update(cx, |thread, cx| thread.send(vec!["world".into()], cx)))
-            .await
-            .unwrap();
+        cx.update(|cx| {
+            thread.update(cx, |thread, cx| {
+                thread.send(new_prompt_id(), vec!["world".into()], cx)
+            })
+        })
+        .await
+        .unwrap();
         thread.read_with(cx, |thread, cx| {
             assert_eq!(
                 thread.to_markdown(cx),
@@ -2653,7 +2679,6 @@ mod tests {
 
         fn prompt(
             &self,
-            _id: Option<UserMessageId>,
             params: acp::PromptRequest,
             cx: &mut App,
         ) -> Task<gpui::Result<acp::PromptResponse>> {
@@ -2683,11 +2708,11 @@ mod tests {
             .detach();
         }
 
-        fn truncate(
+        fn rewind(
             &self,
             session_id: &acp::SessionId,
             _cx: &App,
-        ) -> Option<Rc<dyn AgentSessionTruncate>> {
+        ) -> Option<Rc<dyn AgentSessionRewind>> {
             Some(Rc::new(FakeAgentSessionEditor {
                 _session_id: session_id.clone(),
             }))
@@ -2702,8 +2727,8 @@ mod tests {
         _session_id: acp::SessionId,
     }
 
-    impl AgentSessionTruncate for FakeAgentSessionEditor {
-        fn run(&self, _message_id: UserMessageId, _cx: &mut App) -> Task<Result<()>> {
+    impl AgentSessionRewind for FakeAgentSessionEditor {
+        fn rewind(&self, _message_id: acp::PromptId, _cx: &mut App) -> Task<Result<()>> {
             Task::ready(Ok(()))
         }
     }

crates/acp_thread/src/connection.rs

@@ -5,19 +5,8 @@ use collections::IndexMap;
 use gpui::{Entity, SharedString, Task};
 use language_model::LanguageModelProviderId;
 use project::Project;
-use serde::{Deserialize, Serialize};
-use std::{any::Any, error::Error, fmt, path::Path, rc::Rc, sync::Arc};
+use std::{any::Any, error::Error, fmt, path::Path, rc::Rc};
 use ui::{App, IconName};
-use uuid::Uuid;
-
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Hash)]
-pub struct UserMessageId(Arc<str>);
-
-impl UserMessageId {
-    pub fn new() -> Self {
-        Self(Uuid::new_v4().to_string().into())
-    }
-}
 
 pub trait AgentConnection {
     fn new_thread(
@@ -31,12 +20,8 @@ pub trait AgentConnection {
 
     fn authenticate(&self, method: acp::AuthMethodId, cx: &mut App) -> Task<Result<()>>;
 
-    fn prompt(
-        &self,
-        user_message_id: Option<UserMessageId>,
-        params: acp::PromptRequest,
-        cx: &mut App,
-    ) -> Task<Result<acp::PromptResponse>>;
+    fn prompt(&self, params: acp::PromptRequest, cx: &mut App)
+    -> Task<Result<acp::PromptResponse>>;
 
     fn resume(
         &self,
@@ -48,11 +33,11 @@ pub trait AgentConnection {
 
     fn cancel(&self, session_id: &acp::SessionId, cx: &mut App);
 
-    fn truncate(
+    fn rewind(
         &self,
         _session_id: &acp::SessionId,
         _cx: &App,
-    ) -> Option<Rc<dyn AgentSessionTruncate>> {
+    ) -> Option<Rc<dyn AgentSessionRewind>> {
         None
     }
 
@@ -85,8 +70,8 @@ impl dyn AgentConnection {
     }
 }
 
-pub trait AgentSessionTruncate {
-    fn run(&self, message_id: UserMessageId, cx: &mut App) -> Task<Result<()>>;
+pub trait AgentSessionRewind {
+    fn rewind(&self, message_id: acp::PromptId, cx: &mut App) -> Task<Result<()>>;
 }
 
 pub trait AgentSessionResume {
@@ -362,7 +347,6 @@ mod test_support {
 
         fn prompt(
             &self,
-            _id: Option<UserMessageId>,
             params: acp::PromptRequest,
             cx: &mut App,
         ) -> Task<gpui::Result<acp::PromptResponse>> {
@@ -432,11 +416,11 @@ mod test_support {
             }
         }
 
-        fn truncate(
+        fn rewind(
             &self,
             _session_id: &agent_client_protocol::SessionId,
             _cx: &App,
-        ) -> Option<Rc<dyn AgentSessionTruncate>> {
+        ) -> Option<Rc<dyn AgentSessionRewind>> {
             Some(Rc::new(StubAgentSessionEditor))
         }
 
@@ -447,8 +431,8 @@ mod test_support {
 
     struct StubAgentSessionEditor;
 
-    impl AgentSessionTruncate for StubAgentSessionEditor {
-        fn run(&self, _: UserMessageId, _: &mut App) -> Task<Result<()>> {
+    impl AgentSessionRewind for StubAgentSessionEditor {
+        fn rewind(&self, _: acp::PromptId, _: &mut App) -> Task<Result<()>> {
             Task::ready(Ok(()))
         }
     }

crates/agent2/src/agent.rs

@@ -905,11 +905,10 @@ impl acp_thread::AgentConnection for NativeAgentConnection {
 
     fn prompt(
         &self,
-        id: Option<acp_thread::UserMessageId>,
         params: acp::PromptRequest,
         cx: &mut App,
     ) -> Task<Result<acp::PromptResponse>> {
-        let id = id.expect("UserMessageId is required");
+        let id = params.prompt_id.expect("UserMessageId is required");
         let session_id = params.session_id.clone();
         log::info!("Received prompt request for session: {}", session_id);
         log::debug!("Prompt blocks count: {}", params.prompt.len());
@@ -948,11 +947,11 @@ impl acp_thread::AgentConnection for NativeAgentConnection {
         });
     }
 
-    fn truncate(
+    fn rewind(
         &self,
         session_id: &agent_client_protocol::SessionId,
         cx: &App,
-    ) -> Option<Rc<dyn acp_thread::AgentSessionTruncate>> {
+    ) -> Option<Rc<dyn acp_thread::AgentSessionRewind>> {
         self.0.read_with(cx, |agent, _cx| {
             agent.sessions.get(session_id).map(|session| {
                 Rc::new(NativeAgentSessionEditor {
@@ -1009,10 +1008,10 @@ struct NativeAgentSessionEditor {
     acp_thread: WeakEntity<AcpThread>,
 }
 
-impl acp_thread::AgentSessionTruncate for NativeAgentSessionEditor {
-    fn run(&self, message_id: acp_thread::UserMessageId, cx: &mut App) -> Task<Result<()>> {
+impl acp_thread::AgentSessionRewind for NativeAgentSessionEditor {
+    fn rewind(&self, message_id: acp::PromptId, cx: &mut App) -> Task<Result<()>> {
         match self.thread.update(cx, |thread, cx| {
-            thread.truncate(message_id.clone(), cx)?;
+            thread.rewind(message_id.clone(), cx)?;
             Ok(thread.latest_token_usage())
         }) {
             Ok(usage) => {
@@ -1065,6 +1064,7 @@ mod tests {
     use super::*;
     use acp_thread::{
         AgentConnection, AgentModelGroupName, AgentModelId, AgentModelInfo, MentionUri,
+        new_prompt_id,
     };
     use fs::FakeFs;
     use gpui::TestAppContext;
@@ -1311,6 +1311,7 @@ mod tests {
 
         let send = acp_thread.update(cx, |thread, cx| {
             thread.send(
+                new_prompt_id(),
                 vec![
                     "What does ".into(),
                     acp::ContentBlock::ResourceLink(acp::ResourceLink {

crates/agent2/src/db.rs

@@ -1,5 +1,5 @@
 use crate::{AgentMessage, AgentMessageContent, UserMessage, UserMessageContent};
-use acp_thread::UserMessageId;
+use acp_thread::new_prompt_id;
 use agent::{thread::DetailedSummaryState, thread_store};
 use agent_client_protocol as acp;
 use agent_settings::{AgentProfileId, CompletionMode};
@@ -43,7 +43,7 @@ pub struct DbThread {
     #[serde(default)]
     pub cumulative_token_usage: language_model::TokenUsage,
     #[serde(default)]
-    pub request_token_usage: HashMap<acp_thread::UserMessageId, language_model::TokenUsage>,
+    pub request_token_usage: HashMap<acp::PromptId, language_model::TokenUsage>,
     #[serde(default)]
     pub model: Option<DbLanguageModel>,
     #[serde(default)]
@@ -97,7 +97,7 @@ impl DbThread {
                         content.push(UserMessageContent::Text(msg.context));
                     }
 
-                    let id = UserMessageId::new();
+                    let id = new_prompt_id();
                     last_user_message_id = Some(id.clone());
 
                     crate::Message::User(UserMessage {

crates/agent2/src/tests/mod.rs

@@ -1,5 +1,5 @@
 use super::*;
-use acp_thread::{AgentConnection, AgentModelGroupName, AgentModelList, UserMessageId};
+use acp_thread::{AgentConnection, AgentModelGroupName, AgentModelList, new_prompt_id};
 use agent_client_protocol::{self as acp};
 use agent_settings::AgentProfileId;
 use anyhow::Result;
@@ -48,7 +48,7 @@ async fn test_echo(cx: &mut TestAppContext) {
 
     let events = thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Testing: Reply with 'Hello'"], cx)
+            thread.send(new_prompt_id(), ["Testing: Reply with 'Hello'"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -79,7 +79,7 @@ async fn test_thinking(cx: &mut TestAppContext) {
     let events = thread
         .update(cx, |thread, cx| {
             thread.send(
-                UserMessageId::new(),
+                new_prompt_id(),
                 [indoc! {"
                     Testing:
 
@@ -130,9 +130,7 @@ async fn test_system_prompt(cx: &mut TestAppContext) {
     });
     thread.update(cx, |thread, _| thread.add_tool(EchoTool));
     thread
-        .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["abc"], cx)
-        })
+        .update(cx, |thread, cx| thread.send(new_prompt_id(), ["abc"], cx))
         .unwrap();
     cx.run_until_parked();
     let mut pending_completions = fake_model.pending_completions();
@@ -168,7 +166,7 @@ async fn test_prompt_caching(cx: &mut TestAppContext) {
     // Send initial user message and verify it's cached
     thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Message 1"], cx)
+            thread.send(new_prompt_id(), ["Message 1"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -191,7 +189,7 @@ async fn test_prompt_caching(cx: &mut TestAppContext) {
     // Send another user message and verify only the latest is cached
     thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Message 2"], cx)
+            thread.send(new_prompt_id(), ["Message 2"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -227,7 +225,7 @@ async fn test_prompt_caching(cx: &mut TestAppContext) {
     thread.update(cx, |thread, _| thread.add_tool(EchoTool));
     thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Use the echo tool"], cx)
+            thread.send(new_prompt_id(), ["Use the echo tool"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -304,7 +302,7 @@ async fn test_basic_tool_calls(cx: &mut TestAppContext) {
         .update(cx, |thread, cx| {
             thread.add_tool(EchoTool);
             thread.send(
-                UserMessageId::new(),
+                new_prompt_id(),
                 ["Now test the echo tool with 'Hello'. Does it work? Say 'Yes' or 'No'."],
                 cx,
             )
@@ -320,7 +318,7 @@ async fn test_basic_tool_calls(cx: &mut TestAppContext) {
             thread.remove_tool(&EchoTool::name());
             thread.add_tool(DelayTool);
             thread.send(
-                UserMessageId::new(),
+                new_prompt_id(),
                 [
                     "Now call the delay tool with 200ms.",
                     "When the timer goes off, then you echo the output of the tool.",
@@ -363,7 +361,7 @@ async fn test_streaming_tool_calls(cx: &mut TestAppContext) {
     let mut events = thread
         .update(cx, |thread, cx| {
             thread.add_tool(WordListTool);
-            thread.send(UserMessageId::new(), ["Test the word_list tool."], cx)
+            thread.send(new_prompt_id(), ["Test the word_list tool."], cx)
         })
         .unwrap();
 
@@ -414,7 +412,7 @@ async fn test_tool_authorization(cx: &mut TestAppContext) {
     let mut events = thread
         .update(cx, |thread, cx| {
             thread.add_tool(ToolRequiringPermission);
-            thread.send(UserMessageId::new(), ["abc"], cx)
+            thread.send(new_prompt_id(), ["abc"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -544,9 +542,7 @@ async fn test_tool_hallucination(cx: &mut TestAppContext) {
     let fake_model = model.as_fake();
 
     let mut events = thread
-        .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["abc"], cx)
-        })
+        .update(cx, |thread, cx| thread.send(new_prompt_id(), ["abc"], cx))
         .unwrap();
     cx.run_until_parked();
     fake_model.send_last_completion_stream_event(LanguageModelCompletionEvent::ToolUse(
@@ -575,7 +571,7 @@ async fn test_resume_after_tool_use_limit(cx: &mut TestAppContext) {
     let events = thread
         .update(cx, |thread, cx| {
             thread.add_tool(EchoTool);
-            thread.send(UserMessageId::new(), ["abc"], cx)
+            thread.send(new_prompt_id(), ["abc"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -684,7 +680,7 @@ async fn test_send_after_tool_use_limit(cx: &mut TestAppContext) {
     let events = thread
         .update(cx, |thread, cx| {
             thread.add_tool(EchoTool);
-            thread.send(UserMessageId::new(), ["abc"], cx)
+            thread.send(new_prompt_id(), ["abc"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -718,7 +714,7 @@ async fn test_send_after_tool_use_limit(cx: &mut TestAppContext) {
 
     thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), vec!["ghi"], cx)
+            thread.send(new_prompt_id(), vec!["ghi"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -818,7 +814,7 @@ async fn test_concurrent_tool_calls(cx: &mut TestAppContext) {
         .update(cx, |thread, cx| {
             thread.add_tool(DelayTool);
             thread.send(
-                UserMessageId::new(),
+                new_prompt_id(),
                 [
                     "Call the delay tool twice in the same message.",
                     "Once with 100ms. Once with 300ms.",
@@ -898,7 +894,7 @@ async fn test_profiles(cx: &mut TestAppContext) {
     thread
         .update(cx, |thread, cx| {
             thread.set_profile(AgentProfileId("test-1".into()));
-            thread.send(UserMessageId::new(), ["test"], cx)
+            thread.send(new_prompt_id(), ["test"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -918,7 +914,7 @@ async fn test_profiles(cx: &mut TestAppContext) {
     thread
         .update(cx, |thread, cx| {
             thread.set_profile(AgentProfileId("test-2".into()));
-            thread.send(UserMessageId::new(), ["test2"], cx)
+            thread.send(new_prompt_id(), ["test2"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -986,7 +982,7 @@ async fn test_mcp_tools(cx: &mut TestAppContext) {
     );
 
     let events = thread.update(cx, |thread, cx| {
-        thread.send(UserMessageId::new(), ["Hey"], cx).unwrap()
+        thread.send(new_prompt_id(), ["Hey"], cx).unwrap()
     });
     cx.run_until_parked();
 
@@ -1028,7 +1024,7 @@ async fn test_mcp_tools(cx: &mut TestAppContext) {
     // Send again after adding the echo tool, ensuring the name collision is resolved.
     let events = thread.update(cx, |thread, cx| {
         thread.add_tool(EchoTool);
-        thread.send(UserMessageId::new(), ["Go"], cx).unwrap()
+        thread.send(new_prompt_id(), ["Go"], cx).unwrap()
     });
     cx.run_until_parked();
     let completion = fake_model.pending_completions().pop().unwrap();
@@ -1235,9 +1231,7 @@ async fn test_mcp_tool_truncation(cx: &mut TestAppContext) {
     );
 
     thread
-        .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Go"], cx)
-        })
+        .update(cx, |thread, cx| thread.send(new_prompt_id(), ["Go"], cx))
         .unwrap();
     cx.run_until_parked();
     let completion = fake_model.pending_completions().pop().unwrap();
@@ -1271,7 +1265,7 @@ async fn test_cancellation(cx: &mut TestAppContext) {
             thread.add_tool(InfiniteTool);
             thread.add_tool(EchoTool);
             thread.send(
-                UserMessageId::new(),
+                new_prompt_id(),
                 ["Call the echo tool, then call the infinite tool, then explain their output"],
                 cx,
             )
@@ -1327,7 +1321,7 @@ async fn test_cancellation(cx: &mut TestAppContext) {
     let events = thread
         .update(cx, |thread, cx| {
             thread.send(
-                UserMessageId::new(),
+                new_prompt_id(),
                 ["Testing: reply with 'Hello' then stop."],
                 cx,
             )
@@ -1353,7 +1347,7 @@ async fn test_in_progress_send_canceled_by_next_send(cx: &mut TestAppContext) {
 
     let events_1 = thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hello 1"], cx)
+            thread.send(new_prompt_id(), ["Hello 1"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -1362,7 +1356,7 @@ async fn test_in_progress_send_canceled_by_next_send(cx: &mut TestAppContext) {
 
     let events_2 = thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hello 2"], cx)
+            thread.send(new_prompt_id(), ["Hello 2"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -1384,7 +1378,7 @@ async fn test_subsequent_successful_sends_dont_cancel(cx: &mut TestAppContext) {
 
     let events_1 = thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hello 1"], cx)
+            thread.send(new_prompt_id(), ["Hello 1"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -1396,7 +1390,7 @@ async fn test_subsequent_successful_sends_dont_cancel(cx: &mut TestAppContext) {
 
     let events_2 = thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hello 2"], cx)
+            thread.send(new_prompt_id(), ["Hello 2"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -1416,9 +1410,7 @@ async fn test_refusal(cx: &mut TestAppContext) {
     let fake_model = model.as_fake();
 
     let events = thread
-        .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hello"], cx)
-        })
+        .update(cx, |thread, cx| thread.send(new_prompt_id(), ["Hello"], cx))
         .unwrap();
     cx.run_until_parked();
     thread.read_with(cx, |thread, _| {
@@ -1464,7 +1456,7 @@ async fn test_truncate_first_message(cx: &mut TestAppContext) {
     let ThreadTest { model, thread, .. } = setup(cx, TestModel::Fake).await;
     let fake_model = model.as_fake();
 
-    let message_id = UserMessageId::new();
+    let message_id = new_prompt_id();
     thread
         .update(cx, |thread, cx| {
             thread.send(message_id.clone(), ["Hello"], cx)
@@ -1516,7 +1508,7 @@ async fn test_truncate_first_message(cx: &mut TestAppContext) {
     });
 
     thread
-        .update(cx, |thread, cx| thread.truncate(message_id, cx))
+        .update(cx, |thread, cx| thread.rewind(message_id, cx))
         .unwrap();
     cx.run_until_parked();
     thread.read_with(cx, |thread, _| {
@@ -1526,9 +1518,7 @@ async fn test_truncate_first_message(cx: &mut TestAppContext) {
 
     // Ensure we can still send a new message after truncation.
     thread
-        .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hi"], cx)
-        })
+        .update(cx, |thread, cx| thread.send(new_prompt_id(), ["Hi"], cx))
         .unwrap();
     thread.update(cx, |thread, _cx| {
         assert_eq!(
@@ -1582,7 +1572,7 @@ async fn test_truncate_second_message(cx: &mut TestAppContext) {
 
     thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Message 1"], cx)
+            thread.send(new_prompt_id(), ["Message 1"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -1625,7 +1615,7 @@ async fn test_truncate_second_message(cx: &mut TestAppContext) {
 
     assert_first_message_state(cx);
 
-    let second_message_id = UserMessageId::new();
+    let second_message_id = new_prompt_id();
     thread
         .update(cx, |thread, cx| {
             thread.send(second_message_id.clone(), ["Message 2"], cx)
@@ -1677,7 +1667,7 @@ async fn test_truncate_second_message(cx: &mut TestAppContext) {
     });
 
     thread
-        .update(cx, |thread, cx| thread.truncate(second_message_id, cx))
+        .update(cx, |thread, cx| thread.rewind(second_message_id, cx))
         .unwrap();
     cx.run_until_parked();
 
@@ -1696,9 +1686,7 @@ async fn test_title_generation(cx: &mut TestAppContext) {
     });
 
     let send = thread
-        .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hello"], cx)
-        })
+        .update(cx, |thread, cx| thread.send(new_prompt_id(), ["Hello"], cx))
         .unwrap();
     cx.run_until_parked();
 
@@ -1719,7 +1707,7 @@ async fn test_title_generation(cx: &mut TestAppContext) {
     // Send another message, ensuring no title is generated this time.
     let send = thread
         .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Hello again"], cx)
+            thread.send(new_prompt_id(), ["Hello again"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -1740,7 +1728,7 @@ async fn test_building_request_with_pending_tools(cx: &mut TestAppContext) {
         .update(cx, |thread, cx| {
             thread.add_tool(ToolRequiringPermission);
             thread.add_tool(EchoTool);
-            thread.send(UserMessageId::new(), ["Hey!"], cx)
+            thread.send(new_prompt_id(), ["Hey!"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -1892,7 +1880,9 @@ async fn test_agent_connection(cx: &mut TestAppContext) {
     let model = model.as_fake();
     assert_eq!(model.id().0, "fake", "should return default model");
 
-    let request = acp_thread.update(cx, |thread, cx| thread.send(vec!["abc".into()], cx));
+    let request = acp_thread.update(cx, |thread, cx| {
+        thread.send(new_prompt_id(), vec!["abc".into()], cx)
+    });
     cx.run_until_parked();
     model.send_last_completion_stream_text_chunk("def");
     cx.run_until_parked();
@@ -1922,8 +1912,8 @@ async fn test_agent_connection(cx: &mut TestAppContext) {
     let result = cx
         .update(|cx| {
             connection.prompt(
-                Some(acp_thread::UserMessageId::new()),
                 acp::PromptRequest {
+                    prompt_id: Some(new_prompt_id()),
                     session_id: session_id.clone(),
                     prompt: vec!["ghi".into()],
                 },
@@ -1946,9 +1936,7 @@ async fn test_tool_updates_to_completion(cx: &mut TestAppContext) {
     let fake_model = model.as_fake();
 
     let mut events = thread
-        .update(cx, |thread, cx| {
-            thread.send(UserMessageId::new(), ["Think"], cx)
-        })
+        .update(cx, |thread, cx| thread.send(new_prompt_id(), ["Think"], cx))
         .unwrap();
     cx.run_until_parked();
 
@@ -2049,7 +2037,7 @@ async fn test_send_no_retry_on_success(cx: &mut TestAppContext) {
     let mut events = thread
         .update(cx, |thread, cx| {
             thread.set_completion_mode(agent_settings::CompletionMode::Burn, cx);
-            thread.send(UserMessageId::new(), ["Hello!"], cx)
+            thread.send(new_prompt_id(), ["Hello!"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -2093,7 +2081,7 @@ async fn test_send_retry_on_error(cx: &mut TestAppContext) {
     let mut events = thread
         .update(cx, |thread, cx| {
             thread.set_completion_mode(agent_settings::CompletionMode::Burn, cx);
-            thread.send(UserMessageId::new(), ["Hello!"], cx)
+            thread.send(new_prompt_id(), ["Hello!"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -2159,7 +2147,7 @@ async fn test_send_retry_finishes_tool_calls_on_error(cx: &mut TestAppContext) {
         .update(cx, |thread, cx| {
             thread.set_completion_mode(agent_settings::CompletionMode::Burn, cx);
             thread.add_tool(EchoTool);
-            thread.send(UserMessageId::new(), ["Call the echo tool!"], cx)
+            thread.send(new_prompt_id(), ["Call the echo tool!"], cx)
         })
         .unwrap();
     cx.run_until_parked();
@@ -2234,7 +2222,7 @@ async fn test_send_max_retries_exceeded(cx: &mut TestAppContext) {
     let mut events = thread
         .update(cx, |thread, cx| {
             thread.set_completion_mode(agent_settings::CompletionMode::Burn, cx);
-            thread.send(UserMessageId::new(), ["Hello!"], cx)
+            thread.send(new_prompt_id(), ["Hello!"], cx)
         })
         .unwrap();
     cx.run_until_parked();

crates/agent2/src/thread.rs

@@ -4,7 +4,7 @@ use crate::{
     ListDirectoryTool, MovePathTool, NowTool, OpenTool, ReadFileTool, SystemPromptTemplate,
     Template, Templates, TerminalTool, ThinkingTool, WebSearchTool,
 };
-use acp_thread::{MentionUri, UserMessageId};
+use acp_thread::MentionUri;
 use action_log::ActionLog;
 use agent::thread::{GitState, ProjectSnapshot, WorktreeSnapshot};
 use agent_client_protocol as acp;
@@ -137,7 +137,7 @@ impl Message {
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct UserMessage {
-    pub id: UserMessageId,
+    pub id: acp::PromptId,
     pub content: Vec<UserMessageContent>,
 }
 
@@ -564,7 +564,7 @@ pub struct Thread {
     pending_message: Option<AgentMessage>,
     tools: BTreeMap<SharedString, Arc<dyn AnyAgentTool>>,
     tool_use_limit_reached: bool,
-    request_token_usage: HashMap<UserMessageId, language_model::TokenUsage>,
+    request_token_usage: HashMap<acp::PromptId, language_model::TokenUsage>,
     #[allow(unused)]
     cumulative_token_usage: TokenUsage,
     #[allow(unused)]
@@ -1070,7 +1070,7 @@ impl Thread {
         cx.notify();
     }
 
-    pub fn truncate(&mut self, message_id: UserMessageId, cx: &mut Context<Self>) -> Result<()> {
+    pub fn rewind(&mut self, message_id: acp::PromptId, cx: &mut Context<Self>) -> Result<()> {
         self.cancel(cx);
         let Some(position) = self.messages.iter().position(
             |msg| matches!(msg, Message::User(UserMessage { id, .. }) if id == &message_id),
@@ -1118,7 +1118,7 @@ impl Thread {
     /// The returned channel will report all the occurrences in which the model stops before erroring or ending its turn.
     pub fn send<T>(
         &mut self,
-        id: UserMessageId,
+        id: acp::PromptId,
         content: impl IntoIterator<Item = T>,
         cx: &mut Context<Self>,
     ) -> Result<mpsc::UnboundedReceiver<Result<ThreadEvent>>>

crates/agent_servers/src/acp.rs

@@ -29,6 +29,7 @@ pub struct AcpConnection {
     sessions: Rc<RefCell<HashMap<acp::SessionId, AcpSession>>>,
     auth_methods: Vec<acp::AuthMethod>,
     prompt_capabilities: acp::PromptCapabilities,
+    supports_rewind: bool,
     _io_task: Task<Result<()>>,
 }
 
@@ -147,6 +148,7 @@ impl AcpConnection {
             server_name,
             sessions,
             prompt_capabilities: response.agent_capabilities.prompt_capabilities,
+            supports_rewind: response.agent_capabilities.rewind_session,
             _io_task: io_task,
         })
     }
@@ -225,9 +227,22 @@ impl AgentConnection for AcpConnection {
         })
     }
 
+    fn rewind(
+        &self,
+        session_id: &agent_client_protocol::SessionId,
+        _cx: &App,
+    ) -> Option<Rc<dyn acp_thread::AgentSessionRewind>> {
+        if !self.supports_rewind {
+            return None;
+        }
+        Some(Rc::new(AcpRewinder {
+            connection: self.connection.clone(),
+            session_id: session_id.clone(),
+        }) as _)
+    }
+
     fn prompt(
         &self,
-        _id: Option<acp_thread::UserMessageId>,
         params: acp::PromptRequest,
         cx: &mut App,
     ) -> Task<Result<acp::PromptResponse>> {
@@ -302,6 +317,25 @@ impl AgentConnection for AcpConnection {
     }
 }
 
+struct AcpRewinder {
+    connection: Rc<acp::ClientSideConnection>,
+    session_id: acp::SessionId,
+}
+
+impl acp_thread::AgentSessionRewind for AcpRewinder {
+    fn rewind(&self, prompt_id: acp::PromptId, cx: &mut App) -> Task<Result<()>> {
+        let conn = self.connection.clone();
+        let params = acp::RewindRequest {
+            session_id: self.session_id.clone(),
+            prompt_id,
+        };
+        cx.foreground_executor().spawn(async move {
+            conn.rewind(params).await?;
+            Ok(())
+        })
+    }
+}
+
 struct ClientDelegate {
     sessions: Rc<RefCell<HashMap<acp::SessionId, AcpSession>>>,
     cx: AsyncApp,

crates/agent_servers/src/claude.rs

@@ -294,7 +294,6 @@ impl AgentConnection for ClaudeAgentConnection {
 
     fn prompt(
         &self,
-        _id: Option<acp_thread::UserMessageId>,
         params: acp::PromptRequest,
         cx: &mut App,
     ) -> Task<Result<acp::PromptResponse>> {

crates/agent_servers/src/e2e_tests.rs

@@ -1,5 +1,5 @@
 use crate::AgentServer;
-use acp_thread::{AcpThread, AgentThreadEntry, ToolCall, ToolCallStatus};
+use acp_thread::{AcpThread, AgentThreadEntry, ToolCall, ToolCallStatus, new_prompt_id};
 use agent_client_protocol as acp;
 use futures::{FutureExt, StreamExt, channel::mpsc, select};
 use gpui::{AppContext, Entity, TestAppContext};
@@ -77,6 +77,7 @@ where
     thread
         .update(cx, |thread, cx| {
             thread.send(
+                new_prompt_id(),
                 vec![
                     acp::ContentBlock::Text(acp::TextContent {
                         text: "Read the file ".into(),

crates/agent_ui/src/acp/entry_view_state.rs

@@ -67,7 +67,7 @@ impl EntryViewState {
 
         match thread_entry {
             AgentThreadEntry::UserMessage(message) => {
-                let has_id = message.id.is_some();
+                let has_id = message.prompt_id.is_some();
                 let chunks = message.chunks.clone();
                 if let Some(Entry::UserMessage(editor)) = self.entries.get_mut(index) {
                     if !editor.focus_handle(cx).is_focused(window) {

crates/agent_ui/src/acp/thread_view.rs

@@ -1,7 +1,7 @@
 use acp_thread::{
     AcpThread, AcpThreadEvent, AgentThreadEntry, AssistantMessage, AssistantMessageChunk,
     AuthRequired, LoadError, MentionUri, RetryStatus, ThreadStatus, ToolCall, ToolCallContent,
-    ToolCallStatus, UserMessageId,
+    ToolCallStatus, new_prompt_id,
 };
 use acp_thread::{AgentConnection, Plan};
 use action_log::ActionLog;
@@ -791,7 +791,7 @@ impl AcpThreadView {
                 if let Some(thread) = self.thread()
                     && let Some(AgentThreadEntry::UserMessage(user_message)) =
                         thread.read(cx).entries().get(event.entry_index)
-                    && user_message.id.is_some()
+                    && user_message.prompt_id.is_some()
                 {
                     self.editing_message = Some(event.entry_index);
                     cx.notify();
@@ -801,7 +801,7 @@ impl AcpThreadView {
                 if let Some(thread) = self.thread()
                     && let Some(AgentThreadEntry::UserMessage(user_message)) =
                         thread.read(cx).entries().get(event.entry_index)
-                    && user_message.id.is_some()
+                    && user_message.prompt_id.is_some()
                 {
                     if editor.read(cx).text(cx).as_str() == user_message.content.to_markdown(cx) {
                         self.editing_message = None;
@@ -942,7 +942,7 @@ impl AcpThreadView {
 
                 telemetry::event!("Agent Message Sent", agent = agent_telemetry_id);
 
-                thread.send(contents, cx)
+                thread.send(new_prompt_id(), contents, cx)
             })?;
             send.await
         });
@@ -1011,7 +1011,12 @@ impl AcpThreadView {
         }
 
         let Some(user_message_id) = thread.update(cx, |thread, _| {
-            thread.entries().get(entry_ix)?.user_message()?.id.clone()
+            thread
+                .entries()
+                .get(entry_ix)?
+                .user_message()?
+                .prompt_id
+                .clone()
         }) else {
             return;
         };
@@ -1316,7 +1321,7 @@ impl AcpThreadView {
         cx.notify();
     }
 
-    fn rewind(&mut self, message_id: &UserMessageId, cx: &mut Context<Self>) {
+    fn rewind(&mut self, message_id: &acp::PromptId, cx: &mut Context<Self>) {
         let Some(thread) = self.thread() else {
             return;
         };
@@ -1379,7 +1384,7 @@ impl AcpThreadView {
                     .gap_1p5()
                     .w_full()
                     .children(rules_item)
-                    .children(message.id.clone().and_then(|message_id| {
+                    .children(message.prompt_id.clone().and_then(|message_id| {
                         message.checkpoint.as_ref()?.show.then(|| {
                             h_flex()
                                 .px_3()
@@ -1416,7 +1421,7 @@ impl AcpThreadView {
                                     .map(|this|{
                                         if editing && editor_focus {
                                             this.border_color(focus_border)
-                                        } else if message.id.is_some() {
+                                        } else if message.prompt_id.is_some() {
                                             this.hover(|s| s.border_color(focus_border.opacity(0.8)))
                                         } else {
                                             this
@@ -1437,7 +1442,7 @@ impl AcpThreadView {
                                     .bg(cx.theme().colors().editor_background)
                                     .overflow_hidden();
 
-                                if message.id.is_some() {
+                                if message.prompt_id.is_some() {
                                     this.child(
                                         base_container
                                             .child(
@@ -5398,7 +5403,6 @@ pub(crate) mod tests {
 
         fn prompt(
             &self,
-            _id: Option<acp_thread::UserMessageId>,
             _params: acp::PromptRequest,
             _cx: &mut App,
         ) -> Task<gpui::Result<acp::PromptResponse>> {
@@ -5544,7 +5548,7 @@ pub(crate) mod tests {
             let AgentThreadEntry::UserMessage(user_message) = &thread.entries()[2] else {
                 panic!();
             };
-            user_message.id.clone().unwrap()
+            user_message.prompt_id.clone().unwrap()
         });
 
         thread_view.read_with(cx, |view, cx| {