feat: enable scratchpad tooling backend

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

sidecar/src/Eryx.AgentHost/Services/CopilotAgentBundle.cs

@@ -28,8 +28,7 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
         List<IAsyncDisposable> disposables = [];
         List<AIAgent> agents = [];
         CopilotClientOptions clientOptions = CopilotCliPathResolver.CreateClientOptions();
-        bool isScratchpad = string.Equals(command.WorkspaceKind, "scratchpad", StringComparison.OrdinalIgnoreCase);
-        SessionToolingBundle? toolingBundle = isScratchpad
+        SessionToolingBundle? toolingBundle = command.Tooling is null
             ? null
             : await SessionToolingBundle.CreateAsync(command.Tooling, command.ProjectPath, cancellationToken)
                 .ConfigureAwait(false);
@@ -58,22 +57,7 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
                 Streaming = true,
             };
 
-            if (isScratchpad)
-            {
-                sessionConfig.AvailableTools = [];
-            }
-            else if (toolingBundle is not null)
-            {
-                if (toolingBundle.McpServers.Count > 0)
-                {
-                    sessionConfig.McpServers = toolingBundle.McpServers;
-                }
-
-                if (toolingBundle.Tools.Count > 0)
-                {
-                    sessionConfig.Tools = toolingBundle.Tools.ToList();
-                }
-            }
+            ApplySessionTooling(sessionConfig, toolingBundle?.McpServers, toolingBundle?.Tools);
 
             GitHubCopilotAgent agent = new(
                 client,
@@ -92,6 +76,22 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
         return bundle;
     }
 
+    internal static void ApplySessionTooling(
+        SessionConfig sessionConfig,
+        Dictionary<string, object>? mcpServers,
+        IReadOnlyList<AIFunction>? tools)
+    {
+        if (mcpServers is { Count: > 0 })
+        {
+            sessionConfig.McpServers = mcpServers;
+        }
+
+        if (tools is { Count: > 0 })
+        {
+            sessionConfig.Tools = tools.ToList();
+        }
+    }
+
     public Workflow BuildWorkflow(PatternDefinitionDto pattern)
     {
         return pattern.Mode switch

sidecar/tests/Eryx.AgentHost.Tests/CopilotAgentBundleTests.cs

@@ -0,0 +1,73 @@
+using System.Reflection;
+using Eryx.AgentHost.Services;
+using GitHub.Copilot.SDK;
+using Microsoft.Extensions.AI;
+
+namespace Eryx.AgentHost.Tests;
+
+public sealed class CopilotAgentBundleTests
+{
+    [Fact]
+    public void ApplySessionTooling_MapsMcpServersAndToolsOntoTheSessionConfig()
+    {
+        SessionConfig sessionConfig = new()
+        {
+            AvailableTools = ["glob"],
+        };
+        Dictionary<string, object> mcpServers = new(StringComparer.OrdinalIgnoreCase)
+        {
+            ["Git MCP"] = new McpLocalServerConfig
+            {
+                Type = "local",
+                Command = "node",
+                Args = ["server.js"],
+                Tools = ["git.status"],
+            },
+        };
+        AIFunction tool = CreateTool();
+
+        CopilotAgentBundle.ApplySessionTooling(sessionConfig, mcpServers, [tool]);
+
+        Assert.Same(mcpServers, sessionConfig.McpServers);
+        Assert.NotNull(sessionConfig.Tools);
+        AIFunction configuredTool = Assert.Single(sessionConfig.Tools);
+        Assert.Same(tool, configuredTool);
+        Assert.Equal(["glob"], sessionConfig.AvailableTools);
+    }
+
+    [Fact]
+    public void ApplySessionTooling_LeavesSessionConfigUnsetWhenNoToolingIsProvided()
+    {
+        SessionConfig sessionConfig = new()
+        {
+            AvailableTools = ["glob", "view"],
+        };
+
+        CopilotAgentBundle.ApplySessionTooling(sessionConfig, null, []);
+
+        Assert.Null(sessionConfig.McpServers);
+        Assert.Null(sessionConfig.Tools);
+        Assert.Equal(["glob", "view"], sessionConfig.AvailableTools);
+    }
+
+    private static AIFunction CreateTool()
+    {
+        ToolTarget target = new();
+        MethodInfo method = typeof(ToolTarget).GetMethod(nameof(ToolTarget.Echo))
+            ?? throw new InvalidOperationException("Expected test method to exist.");
+
+        return AIFunctionFactory.Create(
+            method,
+            target,
+            new AIFunctionFactoryOptions
+            {
+                Name = "echo",
+                Description = "Echo test tool",
+            });
+    }
+
+    private sealed class ToolTarget
+    {
+        public string Echo() => "ok";
+    }
+}