Lay the groundwork to create terminals in AcpThread (#35872)

This just prepares the types so that it will be easy later to update a
tool call with a terminal entity. We paused because we realized we want
to simplify how terminals are created in zed, and so that warrants a
dedicated pull request that can be reviewed in isolation.

Release Notes:

- N/A

---------

Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>

crates/acp_thread/src/acp_thread.rs

@@ -198,7 +198,7 @@ impl ToolCall {
         }
     }
 
-    fn update(
+    fn update_fields(
         &mut self,
         fields: acp::ToolCallUpdateFields,
         language_registry: Arc<LanguageRegistry>,
@@ -415,6 +415,39 @@ impl ToolCallContent {
     }
 }
 
+#[derive(Debug, PartialEq)]
+pub enum ToolCallUpdate {
+    UpdateFields(acp::ToolCallUpdate),
+    UpdateDiff(ToolCallUpdateDiff),
+}
+
+impl ToolCallUpdate {
+    fn id(&self) -> &acp::ToolCallId {
+        match self {
+            Self::UpdateFields(update) => &update.id,
+            Self::UpdateDiff(diff) => &diff.id,
+        }
+    }
+}
+
+impl From<acp::ToolCallUpdate> for ToolCallUpdate {
+    fn from(update: acp::ToolCallUpdate) -> Self {
+        Self::UpdateFields(update)
+    }
+}
+
+impl From<ToolCallUpdateDiff> for ToolCallUpdate {
+    fn from(diff: ToolCallUpdateDiff) -> Self {
+        Self::UpdateDiff(diff)
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub struct ToolCallUpdateDiff {
+    pub id: acp::ToolCallId,
+    pub diff: Entity<Diff>,
+}
+
 #[derive(Debug, Default)]
 pub struct Plan {
     pub entries: Vec<PlanEntry>,
@@ -710,36 +743,32 @@ impl AcpThread {
 
     pub fn update_tool_call(
         &mut self,
-        update: acp::ToolCallUpdate,
+        update: impl Into<ToolCallUpdate>,
         cx: &mut Context<Self>,
     ) -> Result<()> {
+        let update = update.into();
         let languages = self.project.read(cx).languages().clone();
 
         let (ix, current_call) = self
-            .tool_call_mut(&update.id)
+            .tool_call_mut(update.id())
             .context("Tool call not found")?;
-        current_call.update(update.fields, languages, cx);
+        match update {
+            ToolCallUpdate::UpdateFields(update) => {
+                current_call.update_fields(update.fields, languages, cx);
+            }
+            ToolCallUpdate::UpdateDiff(update) => {
+                current_call.content.clear();
+                current_call
+                    .content
+                    .push(ToolCallContent::Diff { diff: update.diff });
+            }
+        }
 
         cx.emit(AcpThreadEvent::EntryUpdated(ix));
 
         Ok(())
     }
 
-    pub fn set_tool_call_diff(
-        &mut self,
-        tool_call_id: &acp::ToolCallId,
-        diff: Entity<Diff>,
-        cx: &mut Context<Self>,
-    ) -> Result<()> {
-        let (ix, current_call) = self
-            .tool_call_mut(tool_call_id)
-            .context("Tool call not found")?;
-        current_call.content.clear();
-        current_call.content.push(ToolCallContent::Diff { diff });
-        cx.emit(AcpThreadEvent::EntryUpdated(ix));
-        Ok(())
-    }
-
     /// Updates a tool call if id matches an existing entry, otherwise inserts a new one.
     pub fn upsert_tool_call(&mut self, tool_call: acp::ToolCall, cx: &mut Context<Self>) {
         let status = ToolCallStatus::Allowed {

crates/agent2/src/agent.rs

@@ -503,29 +503,27 @@ impl acp_thread::AgentConnection for NativeAgentConnection {
                         match event {
                             AgentResponseEvent::Text(text) => {
                                 acp_thread.update(cx, |thread, cx| {
-                                    thread.handle_session_update(
-                                        acp::SessionUpdate::AgentMessageChunk {
-                                            content: acp::ContentBlock::Text(acp::TextContent {
-                                                text,
-                                                annotations: None,
-                                            }),
-                                        },
+                                    thread.push_assistant_content_block(
+                                        acp::ContentBlock::Text(acp::TextContent {
+                                            text,
+                                            annotations: None,
+                                        }),
+                                        false,
                                         cx,
                                     )
-                                })??;
+                                })?;
                             }
                             AgentResponseEvent::Thinking(text) => {
                                 acp_thread.update(cx, |thread, cx| {
-                                    thread.handle_session_update(
-                                        acp::SessionUpdate::AgentThoughtChunk {
-                                            content: acp::ContentBlock::Text(acp::TextContent {
-                                                text,
-                                                annotations: None,
-                                            }),
-                                        },
+                                    thread.push_assistant_content_block(
+                                        acp::ContentBlock::Text(acp::TextContent {
+                                            text,
+                                            annotations: None,
+                                        }),
+                                        true,
                                         cx,
                                     )
-                                })??;
+                                })?;
                             }
                             AgentResponseEvent::ToolCallAuthorization(ToolCallAuthorization {
                                 tool_call,
@@ -551,27 +549,12 @@ impl acp_thread::AgentConnection for NativeAgentConnection {
                             }
                             AgentResponseEvent::ToolCall(tool_call) => {
                                 acp_thread.update(cx, |thread, cx| {
-                                    thread.handle_session_update(
-                                        acp::SessionUpdate::ToolCall(tool_call),
-                                        cx,
-                                    )
-                                })??;
+                                    thread.upsert_tool_call(tool_call, cx)
+                                })?;
                             }
-                            AgentResponseEvent::ToolCallUpdate(tool_call_update) => {
+                            AgentResponseEvent::ToolCallUpdate(update) => {
                                 acp_thread.update(cx, |thread, cx| {
-                                    thread.handle_session_update(
-                                        acp::SessionUpdate::ToolCallUpdate(tool_call_update),
-                                        cx,
-                                    )
-                                })??;
-                            }
-                            AgentResponseEvent::ToolCallDiff(tool_call_diff) => {
-                                acp_thread.update(cx, |thread, cx| {
-                                    thread.set_tool_call_diff(
-                                        &tool_call_diff.tool_call_id,
-                                        tool_call_diff.diff,
-                                        cx,
-                                    )
+                                    thread.update_tool_call(update, cx)
                                 })??;
                             }
                             AgentResponseEvent::Stop(stop_reason) => {

crates/agent2/src/tests/mod.rs

@@ -306,7 +306,7 @@ async fn test_tool_hallucination(cx: &mut TestAppContext) {
     let tool_call = expect_tool_call(&mut events).await;
     assert_eq!(tool_call.title, "nonexistent_tool");
     assert_eq!(tool_call.status, acp::ToolCallStatus::Pending);
-    let update = expect_tool_call_update(&mut events).await;
+    let update = expect_tool_call_update_fields(&mut events).await;
     assert_eq!(update.fields.status, Some(acp::ToolCallStatus::Failed));
 }
 
@@ -326,7 +326,7 @@ async fn expect_tool_call(
     }
 }
 
-async fn expect_tool_call_update(
+async fn expect_tool_call_update_fields(
     events: &mut UnboundedReceiver<Result<AgentResponseEvent, LanguageModelCompletionError>>,
 ) -> acp::ToolCallUpdate {
     let event = events
@@ -335,7 +335,9 @@ async fn expect_tool_call_update(
         .expect("no tool call authorization event received")
         .unwrap();
     match event {
-        AgentResponseEvent::ToolCallUpdate(tool_call_update) => return tool_call_update,
+        AgentResponseEvent::ToolCallUpdate(acp_thread::ToolCallUpdate::UpdateFields(update)) => {
+            return update
+        }
         event => {
             panic!("Unexpected event {event:?}");
         }
@@ -425,31 +427,33 @@ async fn test_cancellation(cx: &mut TestAppContext) {
     });
 
     // Wait until both tools are called.
-    let mut expected_tool_calls = vec!["echo", "infinite"];
+    let mut expected_tools = vec!["Echo", "Infinite Tool"];
     let mut echo_id = None;
     let mut echo_completed = false;
     while let Some(event) = events.next().await {
         match event.unwrap() {
             AgentResponseEvent::ToolCall(tool_call) => {
-                assert_eq!(tool_call.title, expected_tool_calls.remove(0));
-                if tool_call.title == "echo" {
+                assert_eq!(tool_call.title, expected_tools.remove(0));
+                if tool_call.title == "Echo" {
                     echo_id = Some(tool_call.id);
                 }
             }
-            AgentResponseEvent::ToolCallUpdate(acp::ToolCallUpdate {
-                id,
-                fields:
-                    acp::ToolCallUpdateFields {
-                        status: Some(acp::ToolCallStatus::Completed),
-                        ..
-                    },
-            }) if Some(&id) == echo_id.as_ref() => {
+            AgentResponseEvent::ToolCallUpdate(acp_thread::ToolCallUpdate::UpdateFields(
+                acp::ToolCallUpdate {
+                    id,
+                    fields:
+                        acp::ToolCallUpdateFields {
+                            status: Some(acp::ToolCallStatus::Completed),
+                            ..
+                        },
+                },
+            )) if Some(&id) == echo_id.as_ref() => {
                 echo_completed = true;
             }
             _ => {}
         }
 
-        if expected_tool_calls.is_empty() && echo_completed {
+        if expected_tools.is_empty() && echo_completed {
             break;
         }
     }
@@ -647,13 +651,26 @@ async fn test_tool_updates_to_completion(cx: &mut TestAppContext) {
     let mut events = thread.update(cx, |thread, cx| thread.send(model.clone(), "Think", cx));
     cx.run_until_parked();
 
-    let input = json!({ "content": "Thinking hard!" });
+    // Simulate streaming partial input.
+    let input = json!({});
     fake_model.send_last_completion_stream_event(LanguageModelCompletionEvent::ToolUse(
         LanguageModelToolUse {
             id: "1".into(),
             name: ThinkingTool.name().into(),
             raw_input: input.to_string(),
             input,
+            is_input_complete: false,
+        },
+    ));
+
+    // Input streaming completed
+    let input = json!({ "content": "Thinking hard!" });
+    fake_model.send_last_completion_stream_event(LanguageModelCompletionEvent::ToolUse(
+        LanguageModelToolUse {
+            id: "1".into(),
+            name: "thinking".into(),
+            raw_input: input.to_string(),
+            input,
             is_input_complete: true,
         },
     ));
@@ -670,22 +687,35 @@ async fn test_tool_updates_to_completion(cx: &mut TestAppContext) {
             status: acp::ToolCallStatus::Pending,
             content: vec![],
             locations: vec![],
-            raw_input: Some(json!({ "content": "Thinking hard!" })),
+            raw_input: Some(json!({})),
             raw_output: None,
         }
     );
-    let update = expect_tool_call_update(&mut events).await;
+    let update = expect_tool_call_update_fields(&mut events).await;
     assert_eq!(
         update,
         acp::ToolCallUpdate {
             id: acp::ToolCallId("1".into()),
             fields: acp::ToolCallUpdateFields {
-                status: Some(acp::ToolCallStatus::InProgress,),
+                title: Some("Thinking".into()),
+                kind: Some(acp::ToolKind::Think),
+                raw_input: Some(json!({ "content": "Thinking hard!" })),
                 ..Default::default()
             },
         }
     );
-    let update = expect_tool_call_update(&mut events).await;
+    let update = expect_tool_call_update_fields(&mut events).await;
+    assert_eq!(
+        update,
+        acp::ToolCallUpdate {
+            id: acp::ToolCallId("1".into()),
+            fields: acp::ToolCallUpdateFields {
+                status: Some(acp::ToolCallStatus::InProgress),
+                ..Default::default()
+            },
+        }
+    );
+    let update = expect_tool_call_update_fields(&mut events).await;
     assert_eq!(
         update,
         acp::ToolCallUpdate {
@@ -696,7 +726,7 @@ async fn test_tool_updates_to_completion(cx: &mut TestAppContext) {
             },
         }
     );
-    let update = expect_tool_call_update(&mut events).await;
+    let update = expect_tool_call_update_fields(&mut events).await;
     assert_eq!(
         update,
         acp::ToolCallUpdate {

crates/agent2/src/tests/test_tools.rs

@@ -24,7 +24,7 @@ impl AgentTool for EchoTool {
         acp::ToolKind::Other
     }
 
-    fn initial_title(&self, _: Self::Input) -> SharedString {
+    fn initial_title(&self, _input: Result<Self::Input, serde_json::Value>) -> SharedString {
         "Echo".into()
     }
 
@@ -55,8 +55,12 @@ impl AgentTool for DelayTool {
         "delay".into()
     }
 
-    fn initial_title(&self, input: Self::Input) -> SharedString {
-        format!("Delay {}ms", input.ms).into()
+    fn initial_title(&self, input: Result<Self::Input, serde_json::Value>) -> SharedString {
+        if let Ok(input) = input {
+            format!("Delay {}ms", input.ms).into()
+        } else {
+            "Delay".into()
+        }
     }
 
     fn kind(&self) -> acp::ToolKind {
@@ -96,7 +100,7 @@ impl AgentTool for ToolRequiringPermission {
         acp::ToolKind::Other
     }
 
-    fn initial_title(&self, _input: Self::Input) -> SharedString {
+    fn initial_title(&self, _input: Result<Self::Input, serde_json::Value>) -> SharedString {
         "This tool requires permission".into()
     }
 
@@ -131,8 +135,8 @@ impl AgentTool for InfiniteTool {
         acp::ToolKind::Other
     }
 
-    fn initial_title(&self, _input: Self::Input) -> SharedString {
-        "This is the tool that never ends... it just goes on and on my friends!".into()
+    fn initial_title(&self, _input: Result<Self::Input, serde_json::Value>) -> SharedString {
+        "Infinite Tool".into()
     }
 
     fn run(
@@ -182,7 +186,7 @@ impl AgentTool for WordListTool {
         acp::ToolKind::Other
     }
 
-    fn initial_title(&self, _input: Self::Input) -> SharedString {
+    fn initial_title(&self, _input: Result<Self::Input, serde_json::Value>) -> SharedString {
         "List of random words".into()
     }
 

crates/agent2/src/thread.rs

@@ -102,9 +102,8 @@ pub enum AgentResponseEvent {
     Text(String),
     Thinking(String),
     ToolCall(acp::ToolCall),
-    ToolCallUpdate(acp::ToolCallUpdate),
+    ToolCallUpdate(acp_thread::ToolCallUpdate),
     ToolCallAuthorization(ToolCallAuthorization),
-    ToolCallDiff(ToolCallDiff),
     Stop(acp::StopReason),
 }
 
@@ -115,12 +114,6 @@ pub struct ToolCallAuthorization {
     pub response: oneshot::Sender<acp::PermissionOptionId>,
 }
 
-#[derive(Debug)]
-pub struct ToolCallDiff {
-    pub tool_call_id: acp::ToolCallId,
-    pub diff: Entity<acp_thread::Diff>,
-}
-
 pub struct Thread {
     messages: Vec<AgentMessage>,
     completion_mode: CompletionMode,
@@ -294,7 +287,7 @@ impl Thread {
                     while let Some(tool_result) = tool_uses.next().await {
                         log::info!("Tool finished {:?}", tool_result);
 
-                        event_stream.send_tool_call_update(
+                        event_stream.update_tool_call_fields(
                             &tool_result.tool_use_id,
                             acp::ToolCallUpdateFields {
                                 status: Some(if tool_result.is_error {
@@ -474,15 +467,24 @@ impl Thread {
             }
         });
 
+        let mut title = SharedString::from(&tool_use.name);
+        let mut kind = acp::ToolKind::Other;
+        if let Some(tool) = tool.as_ref() {
+            title = tool.initial_title(tool_use.input.clone());
+            kind = tool.kind();
+        }
+
         if push_new_tool_use {
-            event_stream.send_tool_call(tool.as_ref(), &tool_use);
+            event_stream.send_tool_call(&tool_use.id, title, kind, tool_use.input.clone());
             last_message
                 .content
                 .push(MessageContent::ToolUse(tool_use.clone()));
         } else {
-            event_stream.send_tool_call_update(
+            event_stream.update_tool_call_fields(
                 &tool_use.id,
                 acp::ToolCallUpdateFields {
+                    title: Some(title.into()),
+                    kind: Some(kind),
                     raw_input: Some(tool_use.input.clone()),
                     ..Default::default()
                 },
@@ -506,7 +508,7 @@ impl Thread {
 
         let tool_event_stream =
             ToolCallEventStream::new(&tool_use, tool.kind(), event_stream.clone());
-        tool_event_stream.send_update(acp::ToolCallUpdateFields {
+        tool_event_stream.update_fields(acp::ToolCallUpdateFields {
             status: Some(acp::ToolCallStatus::InProgress),
             ..Default::default()
         });
@@ -693,7 +695,7 @@ where
     fn kind(&self) -> acp::ToolKind;
 
     /// The initial tool title to display. Can be updated during the tool run.
-    fn initial_title(&self, input: Self::Input) -> SharedString;
+    fn initial_title(&self, input: Result<Self::Input, serde_json::Value>) -> SharedString;
 
     /// Returns the JSON schema that describes the tool's input.
     fn input_schema(&self) -> Schema {
@@ -724,7 +726,7 @@ pub trait AnyAgentTool {
     fn name(&self) -> SharedString;
     fn description(&self, cx: &mut App) -> SharedString;
     fn kind(&self) -> acp::ToolKind;
-    fn initial_title(&self, input: serde_json::Value) -> Result<SharedString>;
+    fn initial_title(&self, input: serde_json::Value) -> SharedString;
     fn input_schema(&self, format: LanguageModelToolSchemaFormat) -> Result<serde_json::Value>;
     fn run(
         self: Arc<Self>,
@@ -750,9 +752,9 @@ where
         self.0.kind()
     }
 
-    fn initial_title(&self, input: serde_json::Value) -> Result<SharedString> {
-        let parsed_input = serde_json::from_value(input)?;
-        Ok(self.0.initial_title(parsed_input))
+    fn initial_title(&self, input: serde_json::Value) -> SharedString {
+        let parsed_input = serde_json::from_value(input.clone()).map_err(|_| input);
+        self.0.initial_title(parsed_input)
     }
 
     fn input_schema(&self, format: LanguageModelToolSchemaFormat) -> Result<serde_json::Value> {
@@ -842,17 +844,17 @@ impl AgentResponseEventStream {
 
     fn send_tool_call(
         &self,
-        tool: Option<&Arc<dyn AnyAgentTool>>,
-        tool_use: &LanguageModelToolUse,
+        id: &LanguageModelToolUseId,
+        title: SharedString,
+        kind: acp::ToolKind,
+        input: serde_json::Value,
     ) {
         self.0
             .unbounded_send(Ok(AgentResponseEvent::ToolCall(Self::initial_tool_call(
-                &tool_use.id,
-                tool.and_then(|t| t.initial_title(tool_use.input.clone()).ok())
-                    .map(|i| i.into())
-                    .unwrap_or_else(|| tool_use.name.to_string()),
-                tool.map(|t| t.kind()).unwrap_or(acp::ToolKind::Other),
-                tool_use.input.clone(),
+                id,
+                title.to_string(),
+                kind,
+                input,
             ))))
             .ok();
     }
@@ -875,7 +877,7 @@ impl AgentResponseEventStream {
         }
     }
 
-    fn send_tool_call_update(
+    fn update_tool_call_fields(
         &self,
         tool_use_id: &LanguageModelToolUseId,
         fields: acp::ToolCallUpdateFields,
@@ -885,14 +887,21 @@ impl AgentResponseEventStream {
                 acp::ToolCallUpdate {
                     id: acp::ToolCallId(tool_use_id.to_string().into()),
                     fields,
-                },
+                }
+                .into(),
             )))
             .ok();
     }
 
-    fn send_tool_call_diff(&self, tool_call_diff: ToolCallDiff) {
+    fn update_tool_call_diff(&self, tool_use_id: &LanguageModelToolUseId, diff: Entity<Diff>) {
         self.0
-            .unbounded_send(Ok(AgentResponseEvent::ToolCallDiff(tool_call_diff)))
+            .unbounded_send(Ok(AgentResponseEvent::ToolCallUpdate(
+                acp_thread::ToolCallUpdateDiff {
+                    id: acp::ToolCallId(tool_use_id.to_string().into()),
+                    diff,
+                }
+                .into(),
+            )))
             .ok();
     }
 
@@ -964,15 +973,13 @@ impl ToolCallEventStream {
         }
     }
 
-    pub fn send_update(&self, fields: acp::ToolCallUpdateFields) {
-        self.stream.send_tool_call_update(&self.tool_use_id, fields);
+    pub fn update_fields(&self, fields: acp::ToolCallUpdateFields) {
+        self.stream
+            .update_tool_call_fields(&self.tool_use_id, fields);
     }
 
-    pub fn send_diff(&self, diff: Entity<Diff>) {
-        self.stream.send_tool_call_diff(ToolCallDiff {
-            tool_call_id: acp::ToolCallId(self.tool_use_id.to_string().into()),
-            diff,
-        });
+    pub fn update_diff(&self, diff: Entity<Diff>) {
+        self.stream.update_tool_call_diff(&self.tool_use_id, diff);
     }
 
     pub fn authorize(&self, title: String) -> impl use<> + Future<Output = Result<()>> {

crates/agent2/src/tools/edit_file_tool.rs

@@ -1,3 +1,4 @@
+use crate::{AgentTool, Thread, ToolCallEventStream};
 use acp_thread::Diff;
 use agent_client_protocol as acp;
 use anyhow::{anyhow, Context as _, Result};
@@ -20,7 +21,7 @@ use std::sync::Arc;
 use ui::SharedString;
 use util::ResultExt;
 
-use crate::{AgentTool, Thread, ToolCallEventStream};
+const DEFAULT_UI_TEXT: &str = "Editing file";
 
 /// This is a tool for creating a new file or editing an existing file. For moving or renaming files, you should generally use the `terminal` tool with the 'mv' command instead.
 ///
@@ -78,6 +79,14 @@ pub struct EditFileToolInput {
     pub mode: EditFileMode,
 }
 
+#[derive(Debug, Serialize, Deserialize, JsonSchema)]
+struct EditFileToolPartialInput {
+    #[serde(default)]
+    path: String,
+    #[serde(default)]
+    display_description: String,
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize, JsonSchema)]
 #[serde(rename_all = "lowercase")]
 pub enum EditFileMode {
@@ -182,8 +191,27 @@ impl AgentTool for EditFileTool {
         acp::ToolKind::Edit
     }
 
-    fn initial_title(&self, input: Self::Input) -> SharedString {
-        input.display_description.into()
+    fn initial_title(&self, input: Result<Self::Input, serde_json::Value>) -> SharedString {
+        match input {
+            Ok(input) => input.display_description.into(),
+            Err(raw_input) => {
+                if let Some(input) =
+                    serde_json::from_value::<EditFileToolPartialInput>(raw_input).ok()
+                {
+                    let description = input.display_description.trim();
+                    if !description.is_empty() {
+                        return description.to_string().into();
+                    }
+
+                    let path = input.path.trim().to_string();
+                    if !path.is_empty() {
+                        return path.into();
+                    }
+                }
+
+                DEFAULT_UI_TEXT.into()
+            }
+        }
     }
 
     fn run(
@@ -226,7 +254,7 @@ impl AgentTool for EditFileTool {
                 .await?;
 
             let diff = cx.new(|cx| Diff::new(buffer.clone(), cx))?;
-            event_stream.send_diff(diff.clone());
+            event_stream.update_diff(diff.clone());
 
             let old_snapshot = buffer.read_with(cx, |buffer, _cx| buffer.snapshot())?;
             let old_text = cx
@@ -1348,6 +1376,66 @@ mod tests {
         }
     }
 
+    #[gpui::test]
+    async fn test_initial_title_with_partial_input(cx: &mut TestAppContext) {
+        init_test(cx);
+        let fs = project::FakeFs::new(cx.executor());
+        let project = Project::test(fs.clone(), [path!("/project").as_ref()], cx).await;
+        let action_log = cx.new(|_| ActionLog::new(project.clone()));
+        let model = Arc::new(FakeLanguageModel::default());
+        let thread = cx.new(|_| {
+            Thread::new(
+                project.clone(),
+                Rc::default(),
+                action_log.clone(),
+                Templates::new(),
+                model.clone(),
+            )
+        });
+        let tool = Arc::new(EditFileTool { thread });
+
+        assert_eq!(
+            tool.initial_title(Err(json!({
+                "path": "src/main.rs",
+                "display_description": "",
+                "old_string": "old code",
+                "new_string": "new code"
+            }))),
+            "src/main.rs"
+        );
+        assert_eq!(
+            tool.initial_title(Err(json!({
+                "path": "",
+                "display_description": "Fix error handling",
+                "old_string": "old code",
+                "new_string": "new code"
+            }))),
+            "Fix error handling"
+        );
+        assert_eq!(
+            tool.initial_title(Err(json!({
+                "path": "src/main.rs",
+                "display_description": "Fix error handling",
+                "old_string": "old code",
+                "new_string": "new code"
+            }))),
+            "Fix error handling"
+        );
+        assert_eq!(
+            tool.initial_title(Err(json!({
+                "path": "",
+                "display_description": "",
+                "old_string": "old code",
+                "new_string": "new code"
+            }))),
+            DEFAULT_UI_TEXT
+        );
+        assert_eq!(
+            tool.initial_title(Err(serde_json::Value::Null)),
+            DEFAULT_UI_TEXT
+        );
+    }
+
     fn init_test(cx: &mut TestAppContext) {
         cx.update(|cx| {
             let settings_store = SettingsStore::test(cx);

crates/agent2/src/tools/find_path_tool.rs

@@ -94,8 +94,12 @@ impl AgentTool for FindPathTool {
         acp::ToolKind::Search
     }
 
-    fn initial_title(&self, input: Self::Input) -> SharedString {
-        format!("Find paths matching “`{}`”", input.glob).into()
+    fn initial_title(&self, input: Result<Self::Input, serde_json::Value>) -> SharedString {
+        let mut title = "Find paths".to_string();
+        if let Ok(input) = input {
+            title.push_str(&format!(" matching “`{}`”", input.glob));
+        }
+        title.into()
     }
 
     fn run(
@@ -111,7 +115,7 @@ impl AgentTool for FindPathTool {
             let paginated_matches: &[PathBuf] = &matches[cmp::min(input.offset, matches.len())
                 ..cmp::min(input.offset + RESULTS_PER_PAGE, matches.len())];
 
-            event_stream.send_update(acp::ToolCallUpdateFields {
+            event_stream.update_fields(acp::ToolCallUpdateFields {
                 title: Some(if paginated_matches.len() == 0 {
                     "No matches".into()
                 } else if paginated_matches.len() == 1 {

crates/agent2/src/tools/read_file_tool.rs

@@ -70,24 +70,28 @@ impl AgentTool for ReadFileTool {
         acp::ToolKind::Read
     }
 
-    fn initial_title(&self, input: Self::Input) -> SharedString {
-        let path = &input.path;
-        match (input.start_line, input.end_line) {
-            (Some(start), Some(end)) => {
-                format!(
-                    "[Read file `{}` (lines {}-{})](@selection:{}:({}-{}))",
-                    path, start, end, path, start, end
-                )
+    fn initial_title(&self, input: Result<Self::Input, serde_json::Value>) -> SharedString {
+        if let Ok(input) = input {
+            let path = &input.path;
+            match (input.start_line, input.end_line) {
+                (Some(start), Some(end)) => {
+                    format!(
+                        "[Read file `{}` (lines {}-{})](@selection:{}:({}-{}))",
+                        path, start, end, path, start, end
+                    )
+                }
+                (Some(start), None) => {
+                    format!(
+                        "[Read file `{}` (from line {})](@selection:{}:({}-{}))",
+                        path, start, path, start, start
+                    )
+                }
+                _ => format!("[Read file `{}`](@file:{})", path, path),
             }
-            (Some(start), None) => {
-                format!(
-                    "[Read file `{}` (from line {})](@selection:{}:({}-{}))",
-                    path, start, path, start, start
-                )
-            }
-            _ => format!("[Read file `{}`](@file:{})", path, path),
+            .into()
+        } else {
+            "Read file".into()
         }
-        .into()
     }
 
     fn run(

crates/agent2/src/tools/thinking_tool.rs

@@ -30,7 +30,7 @@ impl AgentTool for ThinkingTool {
         acp::ToolKind::Think
     }
 
-    fn initial_title(&self, _input: Self::Input) -> SharedString {
+    fn initial_title(&self, _input: Result<Self::Input, serde_json::Value>) -> SharedString {
         "Thinking".into()
     }
 
@@ -40,7 +40,7 @@ impl AgentTool for ThinkingTool {
         event_stream: ToolCallEventStream,
         _cx: &mut App,
     ) -> Task<Result<String>> {
-        event_stream.send_update(acp::ToolCallUpdateFields {
+        event_stream.update_fields(acp::ToolCallUpdateFields {
             content: Some(vec![input.content.into()]),
             ..Default::default()
         });