Refactor setModel to be thin wrappers around session.Rpc.Model.SwitchTo()

Co-authored-by: SteveSandersonMS <1101362+SteveSandersonMS@users.noreply.github.com>

Author: Copilot

dotnet/src/Session.cs

@@ -553,8 +553,7 @@ await InvokeRpcAsync<object>(
     /// </example>
     public async Task SetModelAsync(string model, CancellationToken cancellationToken = default)
     {
-        await InvokeRpcAsync<object>(
-            "session.setModel", [new SetModelRequest { SessionId = SessionId, Model = model }], cancellationToken);
+        await Rpc.Model.SwitchToAsync(model, cancellationToken);
     }
 
     /// <summary>
@@ -655,12 +654,6 @@ internal record SessionDestroyRequest
         public string SessionId { get; init; } = string.Empty;
     }
 
-    internal record SetModelRequest
-    {
-        public string SessionId { get; init; } = string.Empty;
-        public string Model { get; init; } = string.Empty;
-    }
-
     [JsonSourceGenerationOptions(
         JsonSerializerDefaults.Web,
         AllowOutOfOrderMetadataProperties = true,
@@ -673,7 +666,6 @@ internal record SetModelRequest
     [JsonSerializable(typeof(SendMessageResponse))]
     [JsonSerializable(typeof(SessionAbortRequest))]
     [JsonSerializable(typeof(SessionDestroyRequest))]
-    [JsonSerializable(typeof(SetModelRequest))]
     [JsonSerializable(typeof(UserMessageDataAttachmentsItem))]
     [JsonSerializable(typeof(PreToolUseHookInput))]
     [JsonSerializable(typeof(PreToolUseHookOutput))]

go/client_test.go

@@ -448,26 +448,6 @@ func TestResumeSessionRequest_ClientName(t *testing.T) {
 	})
 }
 
-func TestSetModelRequest(t *testing.T) {
-	t.Run("includes sessionId and model in JSON", func(t *testing.T) {
-		req := sessionSetModelRequest{SessionID: "s1", Model: "gpt-4.1"}
-		data, err := json.Marshal(req)
-		if err != nil {
-			t.Fatalf("Failed to marshal: %v", err)
-		}
-		var m map[string]any
-		if err := json.Unmarshal(data, &m); err != nil {
-			t.Fatalf("Failed to unmarshal: %v", err)
-		}
-		if m["sessionId"] != "s1" {
-			t.Errorf("Expected sessionId 's1', got %v", m["sessionId"])
-		}
-		if m["model"] != "gpt-4.1" {
-			t.Errorf("Expected model 'gpt-4.1', got %v", m["model"])
-		}
-	})
-}
-
 func TestClient_CreateSession_RequiresPermissionHandler(t *testing.T) {
 	t.Run("returns error when config is nil", func(t *testing.T) {
 		client := NewClient(nil)

go/session.go

@@ -586,10 +586,7 @@ func (s *Session) Abort(ctx context.Context) error {
 //	    log.Printf("Failed to set model: %v", err)
 //	}
 func (s *Session) SetModel(ctx context.Context, model string) error {
-	_, err := s.client.Request("session.setModel", sessionSetModelRequest{
-		SessionID: s.SessionID,
-		Model:     model,
-	})
+	_, err := s.RPC.Model.SwitchTo(ctx, &rpc.SessionModelSwitchToParams{ModelID: model})
 	if err != nil {
 		return fmt.Errorf("failed to set model: %w", err)
 	}

go/types.go

@@ -828,12 +828,6 @@ type sessionAbortRequest struct {
 	SessionID string `json:"sessionId"`
 }
 
-// sessionSetModelRequest is the request for session.setModel
-type sessionSetModelRequest struct {
-	SessionID string `json:"sessionId"`
-	Model     string `json:"model"`
-}
-
 type sessionSendRequest struct {
 	SessionID   string       `json:"sessionId"`
 	Prompt      string       `json:"prompt"`

nodejs/src/session.ts

@@ -562,9 +562,6 @@ export class CopilotSession {
      * ```
      */
     async setModel(model: string): Promise<void> {
-        await this.connection.sendRequest("session.setModel", {
-            sessionId: this.sessionId,
-            model,
-        });
+        await this.rpc.model.switchTo({ modelId: model });
     }
 }

nodejs/test/client.test.ts

@@ -80,7 +80,7 @@ describe("CopilotClient", () => {
         );
     });
 
-    it("sends session.setModel RPC with correct params", async () => {
+    it("sends session.model.switchTo RPC with correct params", async () => {
         const client = new CopilotClient();
         await client.start();
         onTestFinished(() => client.forceStop());
@@ -90,16 +90,16 @@ describe("CopilotClient", () => {
         // Mock sendRequest to capture the call without hitting the runtime
         const spy = vi.spyOn((client as any).connection!, "sendRequest")
             .mockImplementation(async (method: string, params: any) => {
-                if (method === "session.setModel") return {};
+                if (method === "session.model.switchTo") return {};
                 // Fall through for other methods (shouldn't be called)
                 throw new Error(`Unexpected method: ${method}`);
             });
 
         await session.setModel("gpt-4.1");
 
         expect(spy).toHaveBeenCalledWith(
-            "session.setModel",
-            { sessionId: session.sessionId, model: "gpt-4.1" }
+            "session.model.switchTo",
+            { sessionId: session.sessionId, modelId: "gpt-4.1" }
         );
 
         spy.mockRestore();

python/copilot/session.py

@@ -11,7 +11,7 @@
 from collections.abc import Callable
 from typing import Any, cast
 
-from .generated.rpc import SessionRpc
+from .generated.rpc import SessionModelSwitchToParams, SessionRpc
 from .generated.session_events import SessionEvent, SessionEventType, session_event_from_dict
 from .types import (
     MessageOptions,
@@ -537,7 +537,4 @@ async def set_model(self, model: str) -> None:
         Example:
             >>> await session.set_model("gpt-4.1")
         """
-        await self._client.request(
-            "session.setModel",
-            {"sessionId": self.session_id, "model": model},
-        )
+        await self.rpc.model.switch_to(SessionModelSwitchToParams(model_id=model))

python/test_client.py

@@ -242,13 +242,13 @@ async def test_set_model_sends_correct_rpc(self):
 
             async def mock_request(method, params):
                 captured[method] = params
-                if method == "session.setModel":
+                if method == "session.model.switchTo":
                     return {}
                 return await original_request(method, params)
 
             client._client.request = mock_request
             await session.set_model("gpt-4.1")
-            assert captured["session.setModel"]["sessionId"] == session.session_id
-            assert captured["session.setModel"]["model"] == "gpt-4.1"
+            assert captured["session.model.switchTo"]["sessionId"] == session.session_id
+            assert captured["session.model.switchTo"]["modelId"] == "gpt-4.1"
         finally:
             await client.force_stop()