refactor: add provider abstraction to sidecar host

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

sidecar/src/Aryx.AgentHost/Services/CopilotAgentProvider.cs

@@ -0,0 +1,288 @@
+using GitHub.Copilot.SDK;
+using GitHub.Copilot.SDK.Rpc;
+using Aryx.AgentHost.Contracts;
+
+namespace Aryx.AgentHost.Services;
+
+internal sealed class CopilotAgentProvider : IAgentProvider
+{
+    private const string AskUserToolName = "ask_user";
+    private static readonly HashSet<string> ExcludedRuntimeToolNames = new(StringComparer.OrdinalIgnoreCase)
+    {
+        AskUserToolName,
+        "report_intent",
+        "task_complete",
+    };
+
+    private static readonly string[] AuthenticationErrorIndicators =
+    [
+        "login",
+        "log in",
+        "sign in",
+        "authenticate",
+        "authentication",
+        "not signed in",
+        "not logged in",
+        "reauth",
+        "credential",
+    ];
+
+    public ITurnWorkflowRunner CreateWorkflowRunner(WorkflowValidator workflowValidator)
+    {
+        ArgumentNullException.ThrowIfNull(workflowValidator);
+        return new CopilotWorkflowRunner(workflowValidator);
+    }
+
+    public Task<SidecarCapabilitiesDto> GetCapabilitiesAsync(CancellationToken cancellationToken)
+    {
+        return BuildCapabilitiesAsync(cancellationToken);
+    }
+
+    public IProviderSessionManager CreateSessionManager()
+    {
+        return new CopilotSessionManager();
+    }
+
+    private static async Task<SidecarCapabilitiesDto> BuildCapabilitiesAsync(CancellationToken cancellationToken)
+    {
+        try
+        {
+            CopilotCliContext cliContext = CopilotCliPathResolver.ResolveCliContext();
+            CapabilityProbeResult probe = await ProbeCapabilitiesAsync(cliContext, cancellationToken).ConfigureAwait(false);
+            return CreateCapabilities(probe.Models, probe.RuntimeTools, probe.Connection);
+        }
+        catch (Exception exception)
+        {
+            SidecarConnectionDiagnosticsDto connection = CreateMissingCliDiagnostics(exception);
+            Console.Error.WriteLine($"[aryx sidecar] {connection.Summary} {exception.Message}");
+            return CreateCapabilities([], [], connection);
+        }
+    }
+
+    private static async Task<CapabilityProbeResult> ProbeCapabilitiesAsync(
+        CopilotCliContext cliContext,
+        CancellationToken cancellationToken)
+    {
+        IReadOnlyList<SidecarModelCapabilityDto> models = [];
+        IReadOnlyList<SidecarRuntimeToolDto> runtimeTools = [];
+        SidecarCopilotAccountDiagnosticsDto? account = null;
+        SidecarCopilotCliVersionDiagnosticsDto? cliVersion = null;
+        Task<SidecarCopilotCliVersionDiagnosticsDto> cliVersionTask =
+            CopilotConnectionMetadataResolver.GetCliVersionDiagnosticsAsync(cliContext, cancellationToken);
+
+        try
+        {
+            CopilotClientOptions clientOptions = CopilotCliPathResolver.CreateClientOptions(cliContext);
+
+            await using CopilotClient client = new(clientOptions);
+            await client.StartAsync(cancellationToken).ConfigureAwait(false);
+
+            GetAuthStatusResponse? authStatus =
+                await CopilotConnectionMetadataResolver.TryGetAuthStatusAsync(client, cancellationToken).ConfigureAwait(false);
+            account = await CopilotConnectionMetadataResolver.CreateAccountDiagnosticsAsync(
+                    authStatus,
+                    cliContext.Environment,
+                    cancellationToken)
+                .ConfigureAwait(false);
+
+            models = await ListAvailableModelsAsync(client, cancellationToken).ConfigureAwait(false);
+            runtimeTools = await TryListAvailableRuntimeToolsAsync(client, cancellationToken).ConfigureAwait(false);
+            cliVersion = await cliVersionTask.ConfigureAwait(false);
+
+            return new CapabilityProbeResult(
+                models,
+                runtimeTools,
+                CreateReadyConnectionDiagnostics(cliContext.CliPath, models.Count, cliVersion, account));
+        }
+        catch (Exception exception)
+        {
+            cliVersion = await cliVersionTask.ConfigureAwait(false);
+            Console.Error.WriteLine($"[aryx sidecar] Failed to list available Copilot models: {exception.Message}");
+
+            return new CapabilityProbeResult(
+                models,
+                runtimeTools,
+                CreateFailureConnectionDiagnostics(cliContext.CliPath, exception, cliVersion, account));
+        }
+    }
+
+    private static SidecarCapabilitiesDto CreateCapabilities(
+        IReadOnlyList<SidecarModelCapabilityDto> models,
+        IReadOnlyList<SidecarRuntimeToolDto> runtimeTools,
+        SidecarConnectionDiagnosticsDto connection)
+    {
+        return new SidecarCapabilitiesDto
+        {
+            Modes = BuildModeCapabilities(),
+            Models = models,
+            RuntimeTools = runtimeTools,
+            Connection = connection,
+        };
+    }
+
+    private static Dictionary<string, SidecarModeCapabilityDto> BuildModeCapabilities()
+    {
+        return new Dictionary<string, SidecarModeCapabilityDto>(StringComparer.OrdinalIgnoreCase)
+        {
+            ["single"] = new() { Available = true },
+            ["sequential"] = new() { Available = true },
+            ["concurrent"] = new() { Available = true },
+            ["handoff"] = new() { Available = true },
+            ["group-chat"] = new() { Available = true },
+            ["magentic"] = new()
+            {
+                Available = false,
+                Reason = "Microsoft Agent Framework currently documents Magentic orchestration as unsupported in C#.",
+            },
+        };
+    }
+
+    private static async Task<IReadOnlyList<SidecarModelCapabilityDto>> ListAvailableModelsAsync(
+        CopilotClient client,
+        CancellationToken cancellationToken)
+    {
+        List<ModelInfo> models = await client.ListModelsAsync(cancellationToken).ConfigureAwait(false);
+        return models
+            .Select(model => new SidecarModelCapabilityDto
+            {
+                Id = model.Id,
+                Name = model.Name,
+                SupportedReasoningEfforts = (model.SupportedReasoningEfforts ?? [])
+                    .Where(IsReasoningEffort)
+                    .Distinct(StringComparer.Ordinal)
+                    .ToList(),
+                DefaultReasoningEffort = IsReasoningEffort(model.DefaultReasoningEffort)
+                    ? model.DefaultReasoningEffort
+                    : null,
+            })
+            .OrderBy(model => model.Name, StringComparer.OrdinalIgnoreCase)
+            .ToList();
+    }
+
+    private static async Task<IReadOnlyList<SidecarRuntimeToolDto>> TryListAvailableRuntimeToolsAsync(
+        CopilotClient client,
+        CancellationToken cancellationToken)
+    {
+        try
+        {
+            return await ListAvailableRuntimeToolsAsync(client, cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception exception)
+        {
+            Console.Error.WriteLine($"[aryx sidecar] Failed to list available Copilot runtime tools: {exception.Message}");
+            return [];
+        }
+    }
+
+    private static async Task<IReadOnlyList<SidecarRuntimeToolDto>> ListAvailableRuntimeToolsAsync(
+        CopilotClient client,
+        CancellationToken cancellationToken)
+    {
+        ToolsListResult result = await client.Rpc.Tools.ListAsync(null!, cancellationToken).ConfigureAwait(false);
+        return MapRuntimeTools(result.Tools);
+    }
+
+    internal static IReadOnlyList<SidecarRuntimeToolDto> MapRuntimeTools(IEnumerable<Tool> tools)
+    {
+        return tools
+            .Where(ShouldIncludeRuntimeTool)
+            .Where(tool => !string.IsNullOrWhiteSpace(tool.Name))
+            .Select(tool => new SidecarRuntimeToolDto
+            {
+                Id = tool.Name.Trim(),
+                Label = tool.Name.Trim(),
+                Description = string.IsNullOrWhiteSpace(tool.Description) ? null : tool.Description.Trim(),
+            })
+            .DistinctBy(tool => tool.Id, StringComparer.OrdinalIgnoreCase)
+            .OrderBy(tool => tool.Label, StringComparer.OrdinalIgnoreCase)
+            .ToList();
+    }
+
+    private static bool ShouldIncludeRuntimeTool(Tool tool)
+    {
+        string? toolName = string.IsNullOrWhiteSpace(tool.Name) ? null : tool.Name.Trim();
+        return toolName is not null
+            && !ExcludedRuntimeToolNames.Contains(toolName);
+    }
+
+    private static bool IsReasoningEffort(string? value)
+    {
+        return value is "low" or "medium" or "high" or "xhigh";
+    }
+
+    internal static SidecarConnectionDiagnosticsDto CreateMissingCliDiagnostics(Exception exception)
+    {
+        return new SidecarConnectionDiagnosticsDto
+        {
+            Status = "copilot-cli-missing",
+            Summary = "GitHub Copilot CLI is not installed or is not available on PATH.",
+            Detail = exception.Message,
+            CheckedAt = DateTimeOffset.UtcNow.ToString("O"),
+        };
+    }
+
+    internal static SidecarConnectionDiagnosticsDto CreateReadyConnectionDiagnostics(
+        string cliPath,
+        int modelCount,
+        SidecarCopilotCliVersionDiagnosticsDto? cliVersion = null,
+        SidecarCopilotAccountDiagnosticsDto? account = null)
+    {
+        string summary = modelCount switch
+        {
+            0 => "Connected to GitHub Copilot, but no models were reported.",
+            1 => "Connected to GitHub Copilot. 1 model is available.",
+            _ => $"Connected to GitHub Copilot. {modelCount} models are available.",
+        };
+
+        return new SidecarConnectionDiagnosticsDto
+        {
+            Status = "ready",
+            Summary = summary,
+            Detail = $"Using Copilot CLI at {cliPath}.",
+            CopilotCliPath = cliPath,
+            CopilotCliVersion = cliVersion,
+            Account = account,
+            CheckedAt = DateTimeOffset.UtcNow.ToString("O"),
+        };
+    }
+
+    internal static SidecarConnectionDiagnosticsDto CreateFailureConnectionDiagnostics(
+        string? cliPath,
+        Exception exception,
+        SidecarCopilotCliVersionDiagnosticsDto? cliVersion = null,
+        SidecarCopilotAccountDiagnosticsDto? account = null)
+    {
+        string status = ClassifyConnectionStatus(exception);
+        string summary = status == "copilot-auth-required"
+            ? "GitHub Copilot requires authentication before Aryx can load models."
+            : "GitHub Copilot was found, but Aryx could not load its model list.";
+
+        return new SidecarConnectionDiagnosticsDto
+        {
+            Status = status,
+            Summary = summary,
+            Detail = exception.Message,
+            CopilotCliPath = cliPath,
+            CopilotCliVersion = cliVersion,
+            Account = account,
+            CheckedAt = DateTimeOffset.UtcNow.ToString("O"),
+        };
+    }
+
+    internal static string ClassifyConnectionStatus(Exception exception)
+    {
+        string message = exception.Message;
+        if (AuthenticationErrorIndicators.Any(indicator =>
+            message.Contains(indicator, StringComparison.OrdinalIgnoreCase)))
+        {
+            return "copilot-auth-required";
+        }
+
+        return "copilot-error";
+    }
+
+    private sealed record CapabilityProbeResult(
+        IReadOnlyList<SidecarModelCapabilityDto> Models,
+        IReadOnlyList<SidecarRuntimeToolDto> RuntimeTools,
+        SidecarConnectionDiagnosticsDto Connection);
+}

sidecar/src/Aryx.AgentHost/Services/IAgentProvider.cs

@@ -0,0 +1,12 @@
+using Aryx.AgentHost.Contracts;
+
+namespace Aryx.AgentHost.Services;
+
+internal interface IAgentProvider
+{
+    ITurnWorkflowRunner CreateWorkflowRunner(WorkflowValidator workflowValidator);
+
+    Task<SidecarCapabilitiesDto> GetCapabilitiesAsync(CancellationToken cancellationToken);
+
+    IProviderSessionManager CreateSessionManager();
+}

sidecar/src/Aryx.AgentHost/Services/ICopilotSessionManager.cs

@@ -2,7 +2,7 @@ using Aryx.AgentHost.Contracts;
 
 namespace Aryx.AgentHost.Services;
 
-public interface ICopilotSessionManager
+public interface IProviderSessionManager
 {
     Task<IReadOnlyList<CopilotSessionInfoDto>> ListSessionsAsync(
         CopilotSessionListFilterDto? filter,
@@ -17,3 +17,5 @@ public interface ICopilotSessionManager
         CancellationToken cancellationToken);
 }
 
+public interface ICopilotSessionManager : IProviderSessionManager;
+

sidecar/src/Aryx.AgentHost/Services/SidecarProtocolHost.cs

@@ -1,8 +1,6 @@
 using System.Collections.Concurrent;
 using System.Text.Json;
 using System.Text.Json.Serialization;
-using GitHub.Copilot.SDK;
-using GitHub.Copilot.SDK.Rpc;
 using Aryx.AgentHost.Contracts;
 
 namespace Aryx.AgentHost.Services;
@@ -19,31 +17,11 @@ public sealed class SidecarProtocolHost
     private const string DeleteSessionCommandType = "delete-session";
     private const string DisconnectSessionCommandType = "disconnect-session";
     private const string GetQuotaCommandType = "get-quota";
-    private const string AskUserToolName = "ask_user";
-    private static readonly HashSet<string> ExcludedRuntimeToolNames = new(StringComparer.OrdinalIgnoreCase)
-    {
-        AskUserToolName,
-        "report_intent",
-        "task_complete",
-    };
-
-    private static readonly string[] AuthenticationErrorIndicators =
-    [
-        "login",
-        "log in",
-        "sign in",
-        "authenticate",
-        "authentication",
-        "not signed in",
-        "not logged in",
-        "reauth",
-        "credential",
-    ];
 
     private readonly Func<CancellationToken, Task<SidecarCapabilitiesDto>> _capabilitiesProvider;
     private readonly WorkflowValidator _workflowValidator;
     private readonly ITurnWorkflowRunner _workflowRunner;
-    private readonly ICopilotSessionManager _sessionManager;
+    private readonly IProviderSessionManager _sessionManager;
     private readonly JsonSerializerOptions _jsonOptions;
     private readonly IReadOnlyDictionary<string, Func<CommandContext, Task>> _commandHandlers;
     private readonly SemaphoreSlim _writeLock = new(1, 1);
@@ -60,7 +38,7 @@ public sealed class SidecarProtocolHost
     public SidecarProtocolHost(
         ITurnWorkflowRunner? workflowRunner = null,
         Func<CancellationToken, Task<SidecarCapabilitiesDto>>? capabilitiesProvider = null,
-        ICopilotSessionManager? sessionManager = null)
+        IProviderSessionManager? sessionManager = null)
         : this(new WorkflowValidator(), workflowRunner, capabilitiesProvider, sessionManager)
     {
     }
@@ -69,12 +47,25 @@ public sealed class SidecarProtocolHost
         WorkflowValidator workflowValidator,
         ITurnWorkflowRunner? workflowRunner = null,
         Func<CancellationToken, Task<SidecarCapabilitiesDto>>? capabilitiesProvider = null,
-        ICopilotSessionManager? sessionManager = null)
+        IProviderSessionManager? sessionManager = null)
+        : this(workflowValidator, new CopilotAgentProvider(), workflowRunner, capabilitiesProvider, sessionManager)
     {
+    }
+
+    internal SidecarProtocolHost(
+        WorkflowValidator workflowValidator,
+        IAgentProvider agentProvider,
+        ITurnWorkflowRunner? workflowRunner = null,
+        Func<CancellationToken, Task<SidecarCapabilitiesDto>>? capabilitiesProvider = null,
+        IProviderSessionManager? sessionManager = null)
+    {
+        ArgumentNullException.ThrowIfNull(workflowValidator);
+        ArgumentNullException.ThrowIfNull(agentProvider);
+
         _workflowValidator = workflowValidator;
-        _workflowRunner = workflowRunner ?? new CopilotWorkflowRunner(_workflowValidator);
-        _capabilitiesProvider = capabilitiesProvider ?? BuildCapabilitiesAsync;
-        _sessionManager = sessionManager ?? new CopilotSessionManager();
+        _workflowRunner = workflowRunner ?? agentProvider.CreateWorkflowRunner(_workflowValidator);
+        _capabilitiesProvider = capabilitiesProvider ?? agentProvider.GetCapabilitiesAsync;
+        _sessionManager = sessionManager ?? agentProvider.CreateSessionManager();
         _jsonOptions = JsonSerialization.CreateWebOptions();
         _jsonOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
         _jsonOptions.PropertyNameCaseInsensitive = true;
@@ -459,252 +450,9 @@ public sealed class SidecarProtocolHost
         return cancelledRequestIds;
     }
 
-    private static async Task<SidecarCapabilitiesDto> BuildCapabilitiesAsync(CancellationToken cancellationToken)
-    {
-        try
-        {
-            CopilotCliContext cliContext = CopilotCliPathResolver.ResolveCliContext();
-            CapabilityProbeResult probe = await ProbeCapabilitiesAsync(cliContext, cancellationToken).ConfigureAwait(false);
-            return CreateCapabilities(probe.Models, probe.RuntimeTools, probe.Connection);
-        }
-        catch (Exception exception)
-        {
-            SidecarConnectionDiagnosticsDto connection = CreateMissingCliDiagnostics(exception);
-            Console.Error.WriteLine($"[aryx sidecar] {connection.Summary} {exception.Message}");
-            return CreateCapabilities([], [], connection);
-        }
-    }
-
-    private static async Task<CapabilityProbeResult> ProbeCapabilitiesAsync(
-        CopilotCliContext cliContext,
-        CancellationToken cancellationToken)
-    {
-        IReadOnlyList<SidecarModelCapabilityDto> models = [];
-        IReadOnlyList<SidecarRuntimeToolDto> runtimeTools = [];
-        SidecarCopilotAccountDiagnosticsDto? account = null;
-        SidecarCopilotCliVersionDiagnosticsDto? cliVersion = null;
-        Task<SidecarCopilotCliVersionDiagnosticsDto> cliVersionTask =
-            CopilotConnectionMetadataResolver.GetCliVersionDiagnosticsAsync(cliContext, cancellationToken);
-
-        try
-        {
-            CopilotClientOptions clientOptions = CopilotCliPathResolver.CreateClientOptions(cliContext);
-
-            await using CopilotClient client = new(clientOptions);
-            await client.StartAsync(cancellationToken).ConfigureAwait(false);
-
-            GetAuthStatusResponse? authStatus =
-                await CopilotConnectionMetadataResolver.TryGetAuthStatusAsync(client, cancellationToken).ConfigureAwait(false);
-            account = await CopilotConnectionMetadataResolver.CreateAccountDiagnosticsAsync(
-                    authStatus,
-                    cliContext.Environment,
-                    cancellationToken)
-                .ConfigureAwait(false);
-
-            models = await ListAvailableModelsAsync(client, cancellationToken).ConfigureAwait(false);
-            runtimeTools = await TryListAvailableRuntimeToolsAsync(client, cancellationToken).ConfigureAwait(false);
-            cliVersion = await cliVersionTask.ConfigureAwait(false);
-
-            return new CapabilityProbeResult(
-                models,
-                runtimeTools,
-                CreateReadyConnectionDiagnostics(cliContext.CliPath, models.Count, cliVersion, account));
-        }
-        catch (Exception exception)
-        {
-            cliVersion = await cliVersionTask.ConfigureAwait(false);
-            Console.Error.WriteLine($"[aryx sidecar] Failed to list available Copilot models: {exception.Message}");
-
-            return new CapabilityProbeResult(
-                models,
-                runtimeTools,
-                CreateFailureConnectionDiagnostics(cliContext.CliPath, exception, cliVersion, account));
-        }
-    }
-
-    private static SidecarCapabilitiesDto CreateCapabilities(
-        IReadOnlyList<SidecarModelCapabilityDto> models,
-        IReadOnlyList<SidecarRuntimeToolDto> runtimeTools,
-        SidecarConnectionDiagnosticsDto connection)
-    {
-        return new SidecarCapabilitiesDto
-        {
-            Modes = BuildModeCapabilities(),
-            Models = models,
-            RuntimeTools = runtimeTools,
-            Connection = connection,
-        };
-    }
-
-    private static Dictionary<string, SidecarModeCapabilityDto> BuildModeCapabilities()
-    {
-        return new Dictionary<string, SidecarModeCapabilityDto>(StringComparer.OrdinalIgnoreCase)
-        {
-            ["single"] = new() { Available = true },
-            ["sequential"] = new() { Available = true },
-            ["concurrent"] = new() { Available = true },
-            ["handoff"] = new() { Available = true },
-            ["group-chat"] = new() { Available = true },
-            ["magentic"] = new()
-            {
-                Available = false,
-                Reason = "Microsoft Agent Framework currently documents Magentic orchestration as unsupported in C#.",
-            },
-        };
-    }
-
-    private static async Task<IReadOnlyList<SidecarModelCapabilityDto>> ListAvailableModelsAsync(
-        CopilotClient client,
-        CancellationToken cancellationToken)
-    {
-        List<ModelInfo> models = await client.ListModelsAsync(cancellationToken).ConfigureAwait(false);
-        return models
-            .Select(model => new SidecarModelCapabilityDto
-            {
-                Id = model.Id,
-                Name = model.Name,
-                SupportedReasoningEfforts = (model.SupportedReasoningEfforts ?? [])
-                    .Where(IsReasoningEffort)
-                    .Distinct(StringComparer.Ordinal)
-                    .ToList(),
-                DefaultReasoningEffort = IsReasoningEffort(model.DefaultReasoningEffort)
-                    ? model.DefaultReasoningEffort
-                    : null,
-            })
-            .OrderBy(model => model.Name, StringComparer.OrdinalIgnoreCase)
-            .ToList();
-    }
-
-    private static async Task<IReadOnlyList<SidecarRuntimeToolDto>> TryListAvailableRuntimeToolsAsync(
-        CopilotClient client,
-        CancellationToken cancellationToken)
-    {
-        try
-        {
-            return await ListAvailableRuntimeToolsAsync(client, cancellationToken).ConfigureAwait(false);
-        }
-        catch (Exception exception)
-        {
-            Console.Error.WriteLine($"[aryx sidecar] Failed to list available Copilot runtime tools: {exception.Message}");
-            return [];
-        }
-    }
-
-    private static async Task<IReadOnlyList<SidecarRuntimeToolDto>> ListAvailableRuntimeToolsAsync(
-        CopilotClient client,
-        CancellationToken cancellationToken)
-    {
-        ToolsListResult result = await client.Rpc.Tools.ListAsync(null!, cancellationToken).ConfigureAwait(false);
-        return MapRuntimeTools(result.Tools);
-    }
-
-    internal static IReadOnlyList<SidecarRuntimeToolDto> MapRuntimeTools(IEnumerable<Tool> tools)
-    {
-        return tools
-            .Where(ShouldIncludeRuntimeTool)
-            .Where(tool => !string.IsNullOrWhiteSpace(tool.Name))
-            .Select(tool => new SidecarRuntimeToolDto
-            {
-                Id = tool.Name.Trim(),
-                Label = tool.Name.Trim(),
-                Description = string.IsNullOrWhiteSpace(tool.Description) ? null : tool.Description.Trim(),
-            })
-            .DistinctBy(tool => tool.Id, StringComparer.OrdinalIgnoreCase)
-            .OrderBy(tool => tool.Label, StringComparer.OrdinalIgnoreCase)
-            .ToList();
-    }
-
-    private static bool ShouldIncludeRuntimeTool(Tool tool)
-    {
-        string? toolName = string.IsNullOrWhiteSpace(tool.Name) ? null : tool.Name.Trim();
-        return toolName is not null
-            && !ExcludedRuntimeToolNames.Contains(toolName);
-    }
-
-    private static bool IsReasoningEffort(string? value)
-    {
-        return value is "low" or "medium" or "high" or "xhigh";
-    }
-
-    internal static SidecarConnectionDiagnosticsDto CreateMissingCliDiagnostics(Exception exception)
-    {
-        return new SidecarConnectionDiagnosticsDto
-        {
-            Status = "copilot-cli-missing",
-            Summary = "GitHub Copilot CLI is not installed or is not available on PATH.",
-            Detail = exception.Message,
-            CheckedAt = DateTimeOffset.UtcNow.ToString("O"),
-        };
-    }
-
-    internal static SidecarConnectionDiagnosticsDto CreateReadyConnectionDiagnostics(
-        string cliPath,
-        int modelCount,
-        SidecarCopilotCliVersionDiagnosticsDto? cliVersion = null,
-        SidecarCopilotAccountDiagnosticsDto? account = null)
-    {
-        string summary = modelCount switch
-        {
-            0 => "Connected to GitHub Copilot, but no models were reported.",
-            1 => "Connected to GitHub Copilot. 1 model is available.",
-            _ => $"Connected to GitHub Copilot. {modelCount} models are available.",
-        };
-
-        return new SidecarConnectionDiagnosticsDto
-        {
-            Status = "ready",
-            Summary = summary,
-            Detail = $"Using Copilot CLI at {cliPath}.",
-            CopilotCliPath = cliPath,
-            CopilotCliVersion = cliVersion,
-            Account = account,
-            CheckedAt = DateTimeOffset.UtcNow.ToString("O"),
-        };
-    }
-
-    internal static SidecarConnectionDiagnosticsDto CreateFailureConnectionDiagnostics(
-        string? cliPath,
-        Exception exception,
-        SidecarCopilotCliVersionDiagnosticsDto? cliVersion = null,
-        SidecarCopilotAccountDiagnosticsDto? account = null)
-    {
-        string status = ClassifyConnectionStatus(exception);
-        string summary = status == "copilot-auth-required"
-            ? "GitHub Copilot requires authentication before Aryx can load models."
-            : "GitHub Copilot was found, but Aryx could not load its model list.";
-
-        return new SidecarConnectionDiagnosticsDto
-        {
-            Status = status,
-            Summary = summary,
-            Detail = exception.Message,
-            CopilotCliPath = cliPath,
-            CopilotCliVersion = cliVersion,
-            Account = account,
-            CheckedAt = DateTimeOffset.UtcNow.ToString("O"),
-        };
-    }
-
-    internal static string ClassifyConnectionStatus(Exception exception)
-    {
-        string message = exception.Message;
-        if (AuthenticationErrorIndicators.Any(indicator =>
-            message.Contains(indicator, StringComparison.OrdinalIgnoreCase)))
-        {
-            return "copilot-auth-required";
-        }
-
-        return "copilot-error";
-    }
-
     private sealed record CommandContext(
         string RawCommand,
         SidecarCommandEnvelope Envelope,
         TextWriter Output,
         CancellationToken CancellationToken);
-
-    private sealed record CapabilityProbeResult(
-        IReadOnlyList<SidecarModelCapabilityDto> Models,
-        IReadOnlyList<SidecarRuntimeToolDto> RuntimeTools,
-        SidecarConnectionDiagnosticsDto Connection);
 }

sidecar/tests/Aryx.AgentHost.Tests/SidecarProtocolHostTests.cs

@@ -62,6 +62,103 @@ public sealed class SidecarProtocolHostTests
             });
     }
 
+    [Fact]
+    public async Task InternalConstructor_UsesAgentProviderDefaults()
+    {
+        FakeWorkflowRunner workflowRunner = new(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
+        {
+            await onActivity(new AgentActivityEventDto
+            {
+                Type = "agent-activity",
+                RequestId = command.RequestId,
+                SessionId = command.SessionId,
+                ActivityType = "thinking",
+                AgentId = "agent-provider",
+                AgentName = "Provider Agent",
+            });
+
+            return
+            [
+                new ChatMessageDto
+                {
+                    Id = "assistant-provider",
+                    Role = "assistant",
+                    AuthorName = "Provider Agent",
+                    Content = "Hello from the provider.",
+                    CreatedAt = "2026-01-01T00:00:00.0000000Z",
+                },
+            ];
+        });
+        FakeSessionManager sessionManager = new()
+        {
+            Sessions =
+            [
+                new CopilotSessionInfoDto
+                {
+                    CopilotSessionId = "aryx::provider-session::agent-provider",
+                    ManagedByAryx = true,
+                    SessionId = "provider-session",
+                    AgentId = "agent-provider",
+                },
+            ],
+        };
+        SidecarCapabilitiesDto capabilities = new()
+        {
+            Modes = new Dictionary<string, SidecarModeCapabilityDto>(StringComparer.OrdinalIgnoreCase)
+            {
+                ["single"] = new() { Available = true },
+            },
+            Models =
+            [
+                new SidecarModelCapabilityDto
+                {
+                    Id = "provider-model",
+                    Name = "Provider Model",
+                },
+            ],
+            RuntimeTools = [],
+            Connection = new SidecarConnectionDiagnosticsDto
+            {
+                Status = "ready",
+                Summary = "Provider is ready.",
+                CheckedAt = "2026-01-01T00:00:00.0000000Z",
+            },
+        };
+        SidecarProtocolHost host = new(
+            new WorkflowValidator(),
+            new FakeAgentProvider(workflowRunner, sessionManager, capabilities));
+
+        IReadOnlyList<JsonElement> capabilityEvents = await RunHostAsync(
+            new DescribeCapabilitiesCommandDto
+            {
+                Type = "describe-capabilities",
+                RequestId = "provider-capabilities",
+            },
+            host);
+        IReadOnlyList<JsonElement> sessionEvents = await RunHostAsync(
+            new ListSessionsCommandDto
+            {
+                Type = "list-sessions",
+                RequestId = "provider-sessions",
+            },
+            host);
+        IReadOnlyList<JsonElement> turnEvents = await RunHostAsync(
+            CreateRunTurnCommand(requestId: "provider-turn"),
+            host);
+
+        JsonElement capabilityEvent = AssertSingleEvent(capabilityEvents, "capabilities", "provider-capabilities");
+        JsonElement model = Assert.Single(capabilityEvent.GetProperty("capabilities").GetProperty("models").EnumerateArray());
+        Assert.Equal("provider-model", model.GetProperty("id").GetString());
+
+        JsonElement listedEvent = AssertSingleEvent(sessionEvents, "sessions-listed", "provider-sessions");
+        JsonElement session = Assert.Single(listedEvent.GetProperty("sessions").EnumerateArray());
+        Assert.Equal("provider-session", session.GetProperty("sessionId").GetString());
+
+        JsonElement turnComplete = AssertSingleEvent(turnEvents, "turn-complete", "provider-turn");
+        JsonElement message = Assert.Single(turnComplete.GetProperty("messages").EnumerateArray());
+        Assert.Equal("Hello from the provider.", message.GetProperty("content").GetString());
+    }
+
     [Fact]
     public async Task ValidateWorkflowCommand_ReturnsIssuesAndCompletion()
     {
@@ -668,7 +765,7 @@ public sealed class SidecarProtocolHostTests
     [Fact]
     public void MapRuntimeTools_ExcludesOnlyInternalMetaToolsAndDeduplicatesByName()
     {
-        IReadOnlyList<SidecarRuntimeToolDto> runtimeTools = SidecarProtocolHost.MapRuntimeTools(
+        IReadOnlyList<SidecarRuntimeToolDto> runtimeTools = CopilotAgentProvider.MapRuntimeTools(
         [
             new Tool
             {
@@ -721,7 +818,7 @@ public sealed class SidecarProtocolHostTests
     [Fact]
     public void ClassifyConnectionStatus_ReturnsAuthRequiredForLoginFailures()
     {
-        string status = SidecarProtocolHost.ClassifyConnectionStatus(
+        string status = CopilotAgentProvider.ClassifyConnectionStatus(
             new InvalidOperationException("Please run copilot auth login to continue."));
 
         Assert.Equal("copilot-auth-required", status);
@@ -731,7 +828,7 @@ public sealed class SidecarProtocolHostTests
     public void CreateReadyConnectionDiagnostics_ReportsCliPathAndModelCount()
     {
         SidecarConnectionDiagnosticsDto diagnostics =
-            SidecarProtocolHost.CreateReadyConnectionDiagnostics(
+            CopilotAgentProvider.CreateReadyConnectionDiagnostics(
                 @"C:\tools\copilot\copilot.exe",
                 2,
                 new SidecarCopilotCliVersionDiagnosticsDto
@@ -1145,6 +1242,38 @@ public sealed class SidecarProtocolHostTests
         }
     }
 
+    private sealed class FakeAgentProvider : IAgentProvider
+    {
+        private readonly ITurnWorkflowRunner _workflowRunner;
+        private readonly IProviderSessionManager _sessionManager;
+        private readonly SidecarCapabilitiesDto _capabilities;
+
+        public FakeAgentProvider(
+            ITurnWorkflowRunner workflowRunner,
+            IProviderSessionManager sessionManager,
+            SidecarCapabilitiesDto capabilities)
+        {
+            _workflowRunner = workflowRunner;
+            _sessionManager = sessionManager;
+            _capabilities = capabilities;
+        }
+
+        public ITurnWorkflowRunner CreateWorkflowRunner(WorkflowValidator workflowValidator)
+        {
+            return _workflowRunner;
+        }
+
+        public Task<SidecarCapabilitiesDto> GetCapabilitiesAsync(CancellationToken cancellationToken)
+        {
+            return Task.FromResult(_capabilities);
+        }
+
+        public IProviderSessionManager CreateSessionManager()
+        {
+            return _sessionManager;
+        }
+    }
+
     private sealed class FakeSessionManager : ICopilotSessionManager
     {
         public IReadOnlyList<CopilotSessionInfoDto> Sessions { get; init; } = [];