fix(tools): open solution asynchronously to avoid RPC timeout

src/CodingWithCalvin.MCPServer.Server/Tools/SolutionTools.cs

@@ -31,12 +31,12 @@ public async Task<string> GetSolutionInfoAsync()
     }
 
     [McpServerTool(Name = "solution_open", Destructive = true, Idempotent = true)]
-    [Description("Open a solution file in Visual Studio. This will close any currently open solution.")]
+    [Description("Open a solution file in Visual Studio. This will close any currently open solution. Loading runs asynchronously and this returns as soon as the load has started; use solution_info to check when the solution has finished loading.")]
     public async Task<string> OpenSolutionAsync(
         [Description("The full absolute path to the solution file (.sln or .slnx). Supports forward slashes (/) or backslashes (\\).")] string path)
     {
         var success = await _rpcClient.OpenSolutionAsync(path);
-        return success ? $"Opened solution: {path}" : $"Failed to open solution: {path}";
+        return success ? $"Opening solution: {path}" : $"Failed to open solution (file not found?): {path}";
     }
 
     [McpServerTool(Name = "solution_close", Destructive = true, Idempotent = true)]

src/CodingWithCalvin.MCPServer/Services/VisualStudioService.cs

@@ -193,20 +193,39 @@ public async Task<bool> OpenSolutionAsync(string path)
     {
         using var activity = VsixTelemetry.Tracer.StartActivity("OpenSolution");
 
-        await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();
-        var dte = await GetDteAsync();
+        var normalizedPath = NormalizePath(path);
 
-        try
-        {
-            dte.Solution.Open(path);
-            return true;
-        }
-        catch (Exception ex)
+        if (!File.Exists(normalizedPath))
         {
-            activity?.SetStatus(ActivityStatusCode.Error, ex.Message);
-            activity?.RecordException(ex);
+            activity?.SetStatus(ActivityStatusCode.Error, "Solution file not found");
             return false;
         }
+
+        await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();
+        var dte = await GetDteAsync();
+
+        // EnvDTE's Solution.Open() is synchronous and can take a long time for large
+        // solutions. Awaiting it here would block this RPC call (and the calling MCP client)
+        // until the whole solution finishes loading, which can exceed client timeouts and
+        // surface as "An error occurred invoking 'solution_open'" even though the solution is
+        // loading normally. Fire the load off without waiting for it to finish; callers can
+        // poll solution_info to observe when the new solution becomes available.
+        _ = Task.Run(async () =>
+        {
+            using var loadActivity = VsixTelemetry.Tracer.StartActivity("OpenSolution.Load");
+            try
+            {
+                await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();
+                dte.Solution.Open(normalizedPath);
+            }
+            catch (Exception ex)
+            {
+                loadActivity?.SetStatus(ActivityStatusCode.Error, ex.Message);
+                loadActivity?.RecordException(ex);
+            }
+        });
+
+        return true;
     }
 
     public async Task CloseSolutionAsync(bool saveFirst = true)