Reuse conversation cache when streaming edits (#30245)

Release Notes:

- Improved latency when the agent applies edits.

crates/language_model/src/fake_provider.rs

@@ -2,6 +2,7 @@ use crate::{
     AuthenticateError, LanguageModel, LanguageModelCompletionError, LanguageModelCompletionEvent,
     LanguageModelId, LanguageModelName, LanguageModelProvider, LanguageModelProviderId,
     LanguageModelProviderName, LanguageModelProviderState, LanguageModelRequest,
+    LanguageModelToolChoice,
 };
 use futures::{FutureExt, StreamExt, channel::mpsc, future::BoxFuture, stream::BoxStream};
 use gpui::{AnyView, App, AsyncApp, Entity, Task, Window};
@@ -152,6 +153,10 @@ impl LanguageModel for FakeLanguageModel {
         false
     }
 
+    fn supports_tool_choice(&self, _choice: LanguageModelToolChoice) -> bool {
+        false
+    }
+
     fn telemetry_id(&self) -> String {
         "fake".to_string()
     }

crates/language_model/src/language_model.rs

@@ -246,6 +246,9 @@ pub trait LanguageModel: Send + Sync {
     /// Whether this model supports tools.
     fn supports_tools(&self) -> bool;
 
+    /// Whether this model supports choosing which tool to use.
+    fn supports_tool_choice(&self, choice: LanguageModelToolChoice) -> bool;
+
     /// Returns whether this model supports "max mode";
     fn supports_max_mode(&self) -> bool {
         if self.provider_id().0 != ZED_CLOUD_PROVIDER_ID {

crates/language_model/src/request.rs

@@ -203,6 +203,13 @@ pub struct LanguageModelRequestTool {
     pub input_schema: serde_json::Value,
 }
 
+#[derive(Debug, PartialEq, Hash, Clone, Serialize, Deserialize)]
+pub enum LanguageModelToolChoice {
+    Auto,
+    Any,
+    None,
+}
+
 #[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq)]
 pub struct LanguageModelRequest {
     pub thread_id: Option<String>,
@@ -210,6 +217,7 @@ pub struct LanguageModelRequest {
     pub mode: Option<CompletionMode>,
     pub messages: Vec<LanguageModelRequestMessage>,
     pub tools: Vec<LanguageModelRequestTool>,
+    pub tool_choice: Option<LanguageModelToolChoice>,
     pub stop: Vec<String>,
     pub temperature: Option<f32>,
 }