Ask Copilot CLI for the list of models instead of hardcoding it

PolyPilot.Tests/ModelSelectionTests.cs

@@ -117,11 +117,42 @@ public void NormalizeToSlug_AllFallbackModels_AreAlreadySlugs()
     }
 
     [Fact]
-    public void FallbackModels_IncludeCurrentGptVariants()
+    public void BuildSelectionList_AppendsSelectionAndDefault_WhenDiscoveryIsEmpty()
     {
-        Assert.Contains("gpt-5.4", ModelHelper.FallbackModels);
-        Assert.Contains("gpt-5.4-mini", ModelHelper.FallbackModels);
-        Assert.Contains("gpt-5.3-codex", ModelHelper.FallbackModels);
+        var models = ModelHelper.BuildSelectionList(Array.Empty<string>(), "Custom Preview", "claude-opus-4.6");
+
+        Assert.Equal(new[] { "custom-preview", "claude-opus-4.6" }, models);
+    }
+
+    [Fact]
+    public void BuildSelectionList_NormalizesDiscoveredModels_AndAvoidsDuplicates()
+    {
+        var models = ModelHelper.BuildSelectionList(
+            new[] { "Claude Opus 4.6", "claude-opus-4.6", "Custom Preview" },
+            "custom-preview",
+            "claude-opus-4.6");
+
+        Assert.Equal(new[] { "claude-opus-4.6", "custom-preview" }, models);
+    }
+
+    [Fact]
+    public void ShouldAcceptObservedModel_EmptyCurrentModel_AcceptsObserved()
+    {
+        Assert.True(ModelHelper.ShouldAcceptObservedModel("", "claude-opus-4.6"));
+        Assert.True(ModelHelper.ShouldAcceptObservedModel("resumed", "claude-opus-4.6"));
+    }
+
+    [Fact]
+    public void ShouldAcceptObservedModel_SameModel_AcceptsObserved()
+    {
+        Assert.True(ModelHelper.ShouldAcceptObservedModel("Claude Opus 4.6", "claude-opus-4.6"));
+    }
+
+    [Fact]
+    public void ShouldAcceptObservedModel_DifferentObservedModel_PreservesExplicitChoice()
+    {
+        Assert.False(ModelHelper.ShouldAcceptObservedModel("gpt-5.4", "claude-opus-4.6"));
+        Assert.False(ModelHelper.ShouldAcceptObservedModel("claude-haiku-4.5", "claude-opus-4.6"));
     }
 
     [Fact]
@@ -493,6 +524,19 @@ public void ChangeModel_DisplayNameFromDropdown_NormalizesToSlug()
         }
     }
 
+    [Fact]
+    public void BuildSelectionList_PreservesDiscoveryOrder_AndAppendsMissingRequiredModels()
+    {
+        var models = ModelHelper.BuildSelectionList(
+            new[] { "claude-sonnet-4.6", "Claude Opus 4.6", "gpt-5.4" },
+            "claude-opus-4.6",
+            "gpt-5-mini");
+
+        Assert.Equal(
+            new[] { "claude-sonnet-4.6", "claude-opus-4.6", "gpt-5.4", "gpt-5-mini" },
+            models);
+    }
+
     // --- PrettifyModel tests ---
     // The prettifier is duplicated in ExpandedSessionView.razor and ModelSelector.razor.
     // We test the logic inline here to catch regressions like the "Opus-4.5" bug.

PolyPilot.Tests/ScenarioReferenceTests.cs

@@ -153,13 +153,14 @@ public void Scenario_RefreshSessionsButton_HasUnitTestCoverage()
 
     /// <summary>
     /// Scenario: "create-session-model-picker-includes-gpt-5-4"
-    /// Unit test equivalents: ModelSelectionTests.FallbackModels_IncludeCurrentGptVariants
+    /// Unit test equivalents: ModelSelectionTests.BuildSelectionList_AppendsSelectionAndDefault_WhenDiscoveryIsEmpty,
+    ///   ModelSelectionTests.BuildSelectionList_NormalizesDiscoveredModels_AndAvoidsDuplicates,
     ///   and EventsJsonlParsingTests.ExtractLatestModelFromEvents_LaterModelChangeWins
     /// </summary>
     [Fact]
     public void Scenario_ModelPickerIncludesGpt54_HasUnitTestCoverage()
     {
-        Assert.True(true, "See ModelSelectionTests.FallbackModels_IncludeCurrentGptVariants and EventsJsonlParsingTests.ExtractLatestModelFromEvents_LaterModelChangeWins");
+        Assert.True(true, "See ModelSelectionTests.BuildSelectionList_* and EventsJsonlParsingTests.ExtractLatestModelFromEvents_LaterModelChangeWins");
     }
 
     /// <summary>

PolyPilot.Tests/Scenarios/mode-switch-scenarios.json

@@ -530,9 +530,10 @@
     {
       "id": "create-session-model-picker-includes-gpt-5-4",
       "name": "Create session model picker exposes GPT-5.4",
-      "description": "The create-session model selector should list GPT-5.4 so users can match the CLI even when the app falls back to its built-in model catalog.",
+      "description": "The create-session model selector should list GPT-5.4 from the Copilot CLI's discovered model list, without requiring PolyPilot to hardcode every supported model.",
       "unitTestCoverage": [
-        "ModelSelectionTests.FallbackModels_IncludeCurrentGptVariants"
+        "ModelSelectionTests.BuildSelectionList_AppendsSelectionAndDefault_WhenDiscoveryIsEmpty",
+        "ModelSelectionTests.BuildSelectionList_NormalizesDiscoveredModels_AndAvoidsDuplicates"
       ],
       "steps": [
         {
@@ -1585,4 +1586,4 @@
       ]
     }
   ]
-}
+}

PolyPilot.Tests/StateChangeCoalescerTests.cs

@@ -70,19 +70,31 @@ public async Task SeparateBursts_FireSeparately()
     {
         var svc = CreateService();
         int fireCount = 0;
-        svc.OnStateChanged += () => Interlocked.Increment(ref fireCount);
+        var firstBurstFired = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        var secondBurstFired = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        svc.OnStateChanged += () =>
+        {
+            var count = Interlocked.Increment(ref fireCount);
+            if (count >= 1)
+                firstBurstFired.TrySetResult();
+            if (count >= 2)
+                secondBurstFired.TrySetResult();
+        };
 
         // First burst
         for (int i = 0; i < 10; i++)
             svc.NotifyStateChangedCoalesced();
-        // Wait well beyond the coalesce window (150ms) to ensure the timer fires,
-        // even under heavy CI/GC load. Previous 300ms was flaky under load.
-        await Task.Delay(800);
+        var firstBurstCompleted = await Task.WhenAny(firstBurstFired.Task, Task.Delay(5000));
+        Assert.Same(firstBurstFired.Task, firstBurstCompleted);
 
-        // Second burst after timer has fired
+        // Second burst after the first coalesced notification has actually fired
         for (int i = 0; i < 10; i++)
             svc.NotifyStateChangedCoalesced();
-        await Task.Delay(800);
+        var secondBurstCompleted = await Task.WhenAny(secondBurstFired.Task, Task.Delay(5000));
+        Assert.Same(secondBurstFired.Task, secondBurstCompleted);
+
+        // Small settle window for any extra coalesced fires.
+        await Task.Delay(100);
 
         // Each burst should produce ~1 notification
         Assert.InRange(fireCount, 2, 4);

PolyPilot/Components/Layout/SessionListItem.razor

@@ -191,7 +191,7 @@
                     <div class="model-picker-inline" @onclick:stopPropagation="true">
                         <select value="@(Meta?.PreferredModel ?? "")" @onchange="OnPreferredModelChanged">
                             <option value="">Default (@Session.Model)</option>
-                            @foreach (var model in CopilotService.AvailableModels)
+                            @foreach (var model in GetSelectableModels())
                             {
                                 var strengths = ModelCapabilities.GetStrengths(model);
                                 <option value="@model" title="@strengths">@model</option>
@@ -405,6 +405,11 @@
         CopilotService.SetSessionPreferredModel(Session.Name, string.IsNullOrEmpty(slug) ? null : slug);
     }
 
+    private IReadOnlyList<string> GetSelectableModels() =>
+        CopilotService.AvailableModels.Count > 0
+            ? ModelHelper.BuildSelectionList(CopilotService.AvailableModels, Meta?.PreferredModel, Session.Model, CopilotService.DefaultModel)
+            : ModelHelper.BuildSelectionList(ModelHelper.FallbackModels, Meta?.PreferredModel, Session.Model, CopilotService.DefaultModel);
+
     private static string GetShortPath(string path)
     {
         var parts = path.Split(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);

PolyPilot/Components/Layout/SessionSidebar.razor

@@ -1439,7 +1439,9 @@ else
     }
 
     private IReadOnlyList<string> availableModels =>
-        CopilotService.AvailableModels.Count > 0 ? CopilotService.AvailableModels : ModelHelper.FallbackModels;
+        CopilotService.AvailableModels.Count > 0
+            ? ModelHelper.BuildSelectionList(CopilotService.AvailableModels, selectedModel, CopilotService.DefaultModel)
+            : ModelHelper.BuildSelectionList(ModelHelper.FallbackModels, selectedModel, CopilotService.DefaultModel);
 
     private IEnumerable<PersistedSessionInfo> filteredPersistedSessions => 
         (string.IsNullOrWhiteSpace(sessionFilter) 
@@ -1468,7 +1470,7 @@ else
         // Restore last selected model
         var uiState = CopilotService.LoadUiState();
         if (!string.IsNullOrEmpty(uiState?.SelectedModel))
-            selectedModel = uiState.SelectedModel;
+            selectedModel = ModelHelper.NormalizeToSlug(uiState.SelectedModel);
     }
 
     private void SaveSelectedModel()

PolyPilot/Components/Pages/Dashboard.razor

@@ -3353,7 +3353,9 @@
     // === Model, plan mode, font, token helpers ===
 
     private IReadOnlyList<string> availableModels =>
-        CopilotService.AvailableModels.Count > 0 ? CopilotService.AvailableModels : ModelHelper.FallbackModels;
+        CopilotService.AvailableModels.Count > 0
+            ? ModelHelper.BuildSelectionList(CopilotService.AvailableModels, CopilotService.DefaultModel)
+            : ModelHelper.BuildSelectionList(ModelHelper.FallbackModels, CopilotService.DefaultModel);
 
     private string GetSessionModel(AgentSessionInfo session)
     {

PolyPilot/Models/ModelHelper.cs

@@ -1,4 +1,5 @@
 using System.Text.Json;
+using System.Text.RegularExpressions;
 
 namespace PolyPilot.Models;
 
@@ -10,6 +11,15 @@ namespace PolyPilot.Models;
 /// </summary>
 public static class ModelHelper
 {
+    private static readonly Regex ValidSlugPattern = new(@"^[a-z0-9][-a-z0-9.]*$", RegexOptions.Compiled);
+
+    /// <summary>
+    /// Returns true if the string looks like a valid model slug
+    /// (lowercase alphanumeric with hyphens and dots, e.g. "claude-opus-4.6").
+    /// </summary>
+    public static bool IsValidModelSlug(string? slug) =>
+        !string.IsNullOrEmpty(slug) && ValidSlugPattern.IsMatch(slug);
+
     public static IReadOnlyList<string> FallbackModels { get; } = new[]
     {
         "claude-opus-4.6",
@@ -34,6 +44,35 @@ public static class ModelHelper
         "gemini-3-pro-preview",
     };
 
+    /// <summary>
+    /// Builds a model picker list from CLI-discovered models plus any required
+    /// fallback choices (current selection, current session model, default model).
+    /// All values are normalized to slugs and deduplicated case-insensitively.
+    /// </summary>
+    public static IReadOnlyList<string> BuildSelectionList(IEnumerable<string>? discoveredModels, params string?[] requiredModels)
+    {
+        var result = new List<string>();
+        var seen = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+        void Add(string? model)
+        {
+            var normalized = NormalizeToSlug(model);
+            if (!string.IsNullOrEmpty(normalized) && seen.Add(normalized))
+                result.Add(normalized);
+        }
+
+        if (discoveredModels != null)
+        {
+            foreach (var model in discoveredModels)
+                Add(model);
+        }
+
+        foreach (var model in requiredModels)
+            Add(model);
+
+        return result;
+    }
+
     /// <summary>
     /// Normalize any model string to its canonical slug form.
     /// Handles display names like "Claude Opus 4.5", "GPT-5.1-Codex", 
@@ -90,6 +129,23 @@ public static bool IsDisplayName(string? model)
         return model.Any(char.IsUpper) || model.Contains(' ');
     }
 
+    /// <summary>
+    /// Decide whether an observed SDK/CLI event model should replace the current session model.
+    /// Preserve an explicit user-selected model when metrics events report a different backend
+    /// model (for example after resume/abort flows that transiently report a default model).
+    /// </summary>
+    public static bool ShouldAcceptObservedModel(string? currentModel, string? observedModel)
+    {
+        var normalizedObserved = NormalizeToSlug(observedModel);
+        if (string.IsNullOrEmpty(normalizedObserved))
+            return false;
+
+        var normalizedCurrent = NormalizeToSlug(currentModel);
+        return string.IsNullOrEmpty(normalizedCurrent) ||
+               normalizedCurrent == "resumed" ||
+               normalizedCurrent == normalizedObserved;
+    }
+
     /// <summary>
     /// Converts a model slug to a human-friendly display name.
     /// If displayNames dictionary is provided and contains the slug, uses the SDK's display name.

PolyPilot/Services/CopilotService.Events.cs

@@ -772,8 +772,15 @@ await notifService.SendNotificationAsync(
                 if (!string.IsNullOrEmpty(uModel))
                 {
                     var normalizedUModel = Models.ModelHelper.NormalizeToSlug(uModel);
-                    Debug($"[UsageInfo] Updating model from event: {state.Info.Model} -> {normalizedUModel}");
-                    state.Info.Model = normalizedUModel;
+                    if (Models.ModelHelper.ShouldAcceptObservedModel(state.Info.Model, normalizedUModel))
+                    {
+                        Debug($"[UsageInfo] Updating model from event: {state.Info.Model} -> {normalizedUModel}");
+                        state.Info.Model = normalizedUModel;
+                    }
+                    else
+                    {
+                        Debug($"[UsageInfo] Ignoring backend-reported model: {normalizedUModel} (keeping explicit session model: {state.Info.Model})");
+                    }
                 }
                 if (uCurrentTokens.HasValue) state.Info.ContextCurrentTokens = uCurrentTokens;
                 if (uTokenLimit.HasValue) state.Info.ContextTokenLimit = uTokenLimit;
@@ -807,7 +814,17 @@ await notifService.SendNotificationAsync(
                 }
                 catch { }
                 if (!string.IsNullOrEmpty(aModel))
-                    state.Info.Model = Models.ModelHelper.NormalizeToSlug(aModel);
+                {
+                    var normalizedAModel = Models.ModelHelper.NormalizeToSlug(aModel);
+                    if (Models.ModelHelper.ShouldAcceptObservedModel(state.Info.Model, normalizedAModel))
+                    {
+                        state.Info.Model = normalizedAModel;
+                    }
+                    else
+                    {
+                        Debug($"[AssistantUsage] Ignoring backend-reported model: {normalizedAModel} (keeping explicit session model: {state.Info.Model})");
+                    }
+                }
                 if (aInput.HasValue) state.Info.TotalInputTokens += aInput.Value;
                 if (aOutput.HasValue) state.Info.TotalOutputTokens += aOutput.Value;
                 if (aInput.HasValue || aOutput.HasValue || aPremiumQuota != null)