fix: use live copilot model availability

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

sidecar/src/Kopaya.AgentHost/Contracts/ProtocolModels.cs

@@ -48,10 +48,19 @@ public sealed class SidecarModeCapabilityDto
     public string? Reason { get; init; }
 }
 
+public sealed class SidecarModelCapabilityDto
+{
+    public string Id { get; init; } = string.Empty;
+    public string Name { get; init; } = string.Empty;
+    public IReadOnlyList<string> SupportedReasoningEfforts { get; init; } = [];
+    public string? DefaultReasoningEffort { get; init; }
+}
+
 public sealed class SidecarCapabilitiesDto
 {
     public string Runtime { get; init; } = "dotnet-maf";
     public Dictionary<string, SidecarModeCapabilityDto> Modes { get; init; } = new(StringComparer.OrdinalIgnoreCase);
+    public IReadOnlyList<SidecarModelCapabilityDto> Models { get; init; } = [];
 }
 
 public class SidecarCommandEnvelope

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

@@ -1,12 +1,14 @@
 using System.Collections.Concurrent;
 using System.Text.Json;
 using System.Text.Json.Serialization;
+using GitHub.Copilot.SDK;
 using Kopaya.AgentHost.Contracts;
 
 namespace Kopaya.AgentHost.Services;
 
 public sealed class SidecarProtocolHost
 {
+    private readonly Func<CancellationToken, Task<SidecarCapabilitiesDto>> _capabilitiesProvider;
     private readonly PatternValidator _patternValidator;
     private readonly ITurnWorkflowRunner _workflowRunner;
     private readonly JsonSerializerOptions _jsonOptions;
@@ -18,10 +20,14 @@ public sealed class SidecarProtocolHost
     {
     }
 
-    public SidecarProtocolHost(PatternValidator patternValidator, ITurnWorkflowRunner? workflowRunner = null)
+    public SidecarProtocolHost(
+        PatternValidator patternValidator,
+        ITurnWorkflowRunner? workflowRunner = null,
+        Func<CancellationToken, Task<SidecarCapabilitiesDto>>? capabilitiesProvider = null)
     {
         _patternValidator = patternValidator;
         _workflowRunner = workflowRunner ?? new CopilotWorkflowRunner(_patternValidator);
+        _capabilitiesProvider = capabilitiesProvider ?? BuildCapabilitiesAsync;
         _jsonOptions = new JsonSerializerOptions(JsonSerializerDefaults.Web)
         {
             DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
@@ -82,7 +88,7 @@ public sealed class SidecarProtocolHost
                     {
                         Type = "capabilities",
                         RequestId = envelope.RequestId,
-                        Capabilities = BuildCapabilities(),
+                        Capabilities = await _capabilitiesProvider(cancellationToken).ConfigureAwait(false),
                     }, cancellationToken).ConfigureAwait(false);
                     break;
 
@@ -155,8 +161,19 @@ public sealed class SidecarProtocolHost
         }
     }
 
-    private static SidecarCapabilitiesDto BuildCapabilities()
+    private static async Task<SidecarCapabilitiesDto> BuildCapabilitiesAsync(CancellationToken cancellationToken)
     {
+        IReadOnlyList<SidecarModelCapabilityDto> models = [];
+
+        try
+        {
+            models = await ListAvailableModelsAsync(cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception exception)
+        {
+            Console.Error.WriteLine($"[kopaya sidecar] Failed to list available Copilot models: {exception.Message}");
+        }
+
         return new SidecarCapabilitiesDto
         {
             Modes = new Dictionary<string, SidecarModeCapabilityDto>(StringComparer.OrdinalIgnoreCase)
@@ -172,6 +189,38 @@ public sealed class SidecarProtocolHost
                     Reason = "Microsoft Agent Framework currently documents Magentic orchestration as unsupported in C#.",
                 },
             },
+            Models = models,
         };
     }
+
+    private static async Task<IReadOnlyList<SidecarModelCapabilityDto>> ListAvailableModelsAsync(
+        CancellationToken cancellationToken)
+    {
+        CopilotClientOptions clientOptions = CopilotCliPathResolver.CreateClientOptions();
+
+        await using CopilotClient client = new(clientOptions);
+        await client.StartAsync(cancellationToken).ConfigureAwait(false);
+
+        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 bool IsReasoningEffort(string? value)
+    {
+        return value is "low" or "medium" or "high" or "xhigh";
+    }
 }

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

@@ -18,7 +18,7 @@ public sealed class SidecarProtocolHostTests
         {
             Type = "describe-capabilities",
             RequestId = "cap-1",
-        });
+        }, CreateHostForTests());
 
         Assert.Collection(
             events,
@@ -33,6 +33,10 @@ public sealed class SidecarProtocolHostTests
                 JsonElement modes = capabilities.GetProperty("modes");
                 Assert.True(modes.GetProperty("single").GetProperty("available").GetBoolean());
                 Assert.False(modes.GetProperty("magentic").GetProperty("available").GetBoolean());
+                JsonElement[] models = capabilities.GetProperty("models").EnumerateArray().ToArray();
+                JsonElement model = Assert.Single(models);
+                Assert.Equal("gpt-5.4", model.GetProperty("id").GetString());
+                Assert.Equal("medium", model.GetProperty("defaultReasoningEffort").GetString());
 
                 string magenticReason = modes.GetProperty("magentic").GetProperty("reason").GetString() ?? string.Empty;
                 Assert.Contains("unsupported", magenticReason, StringComparison.OrdinalIgnoreCase);
@@ -220,10 +224,42 @@ public sealed class SidecarProtocolHostTests
         using StringReader reader = new(input);
         using StringWriter writer = new();
 
-        await (host ?? new SidecarProtocolHost()).RunAsync(reader, writer, CancellationToken.None);
+        await (host ?? CreateHostForTests()).RunAsync(reader, writer, CancellationToken.None);
         return ParseEvents(writer.ToString());
     }
 
+    private static SidecarProtocolHost CreateHostForTests()
+    {
+        return new SidecarProtocolHost(
+            new PatternValidator(),
+            capabilitiesProvider: _ => Task.FromResult(new SidecarCapabilitiesDto
+            {
+                Modes = 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#.",
+                    },
+                },
+                Models =
+                [
+                    new SidecarModelCapabilityDto
+                    {
+                        Id = "gpt-5.4",
+                        Name = "GPT-5.4",
+                        SupportedReasoningEfforts = ["low", "medium", "high", "xhigh"],
+                        DefaultReasoningEffort = "medium",
+                    },
+                ],
+            }));
+    }
+
     private static IReadOnlyList<JsonElement> ParseEvents(string output)
     {
         List<JsonElement> events = [];