TASK 4 ship step 5.5: social bar bug fixes + bar on the live output — direction-snap drag (SocialBarSnap.Decide + ClearValue, local Canvas.Top was overriding the binding), fediverse nodeinfo subdomain probing + load-time heal (settable FediverseSoftware), SocialBarRenderer strip blitted above the flash via a re-read FramePump socialBar seam — 155 tests passing, 0 warnings

ytLive.Tests/FramePumpTests.cs

@@ -66,7 +66,8 @@ public class FramePumpTests
 
     private static FramePump NewPump(FakeEncoder encoder, Func<EncoderOptions?>? options = null,
         Func<Scene?>? scene = null, Func<SceneElement, VideoFrame?>? resolve = null,
-        List<string>? log = null)
+        List<string>? log = null,
+        Func<(VideoFrame? Frame, SocialBarPosition Position)>? socialBar = null)
     {
         return new FramePump(
             sceneProvider: scene ?? (() => BackdropScene()),
@@ -83,7 +84,8 @@ public class FramePumpTests
             }),
             encoderFactory: () => encoder,
             log: log != null ? m => log.Add(m) : null,
-            pacingDelay: async (_, _) => await Task.Yield()); // deterministic: no real waits
+            pacingDelay: async (_, _) => await Task.Yield(), // deterministic: no real waits
+            socialBar: socialBar);
     }
 
     private static void AssertColor(VideoFrame frame, int x, int y, byte r, byte g, byte b)
@@ -163,6 +165,49 @@ public class FramePumpTests
         Assert.False(pump.IsRunning);
     }
 
+    [Fact]
+    public async Task Start_WithSocialBarSeam_PlacesBarAtTopThenBottomEdge()
+    {
+        var red = SceneCompositorTests.Solid(64, 48, 255, 0, 0);
+        var bar = new VideoFrame(64, 8, new byte[64 * 8 * 4]);
+        Array.Fill(bar.BgraPixels, (byte)255); // opaque white strip
+
+        var encoder = new FakeEncoder();
+        var position = SocialBarPosition.Top;
+        using var pump = NewPump(encoder,
+            resolve: e => e is Source { IsBackdrop: true } ? red : null,
+            socialBar: () => (bar, position));
+
+        await pump.StartAsync();
+        await encoder.FrameArrived.Task.WaitAsync(TimeSpan.FromSeconds(5));
+        Assert.NotEmpty(encoder.Frames);
+        AssertColor(encoder.Frames[0], 0, 0, 255, 255, 255); // bar at the top edge
+
+        // Flip to Bottom: the pump re-reads the seam each frame, so a later frame
+        // lands the bar at the bottom edge (SourceRectHeight - bar height) and the
+        // top corner clears back to backdrop.
+        position = SocialBarPosition.Bottom;
+        VideoFrame? flipped = null;
+        var deadline = DateTime.UtcNow.AddSeconds(5);
+        while (DateTime.UtcNow < deadline && flipped == null)
+        {
+            for (var i = 1; i < encoder.Frames.Count; i++)
+            {
+                var f = encoder.Frames[i];
+                if (f.BgraPixels[2] == 255 && f.BgraPixels[1] == 0 && f.BgraPixels[0] == 0)
+                {
+                    flipped = f;
+                    break;
+                }
+            }
+            if (flipped == null) await Task.Delay(10);
+        }
+        Assert.NotNull(flipped);
+        AssertColor(flipped!, 0, 47, 255, 255, 255); // bar sits on the bottom edge
+
+        await pump.StopAsync();
+    }
+
     [Fact]
     public async Task Start_EncoderThrows_RaisesFailed_AndDisposes()
     {

ytLive.Tests/SceneCompositorTests.cs

@@ -180,6 +180,43 @@ public class SceneCompositorTests
         // untouched corner stays pure red
         AssertColor(output, 0, 0, 255, 0, 0);
     }
+
+    [Fact]
+    public void Composite_WithSocialBar_OverlaysAboveFlash_AtTopOrBottom()
+    {
+        var red = Solid(1920, 1080, 255, 0, 0);
+        var backdrop = new Source { Type = SourceType.DisplayCapture, IsBackdrop = true, CaptureKey = "monitor:0" };
+        var scene = new Scene { Name = "Live" };
+        scene.Elements.Add(backdrop);
+
+        var options = new CompositorOptions
+        {
+            SourceRectX = 0, SourceRectY = 0, SourceRectWidth = 1920, SourceRectHeight = 1080,
+            OutputWidth = 1920, OutputHeight = 1080,
+        };
+        var compositor = new SceneCompositor();
+
+        // master-sized overlay: opaque green at (0,0), 50%-white at the center
+        var bar = new VideoFrame(1920, 1080, new byte[1920 * 1080 * 4]);
+        var g = 0;
+        bar.BgraPixels[g] = 0; bar.BgraPixels[g + 1] = 255; bar.BgraPixels[g + 2] = 0; bar.BgraPixels[g + 3] = 255;
+        var w = (540 * 1920 + 960) * 4;
+        bar.BgraPixels[w] = 255; bar.BgraPixels[w + 1] = 255; bar.BgraPixels[w + 2] = 255; bar.BgraPixels[w + 3] = 128;
+
+        // flash: opaque magenta at (0,0) — the bar must cover it
+        var flash = new VideoFrame(1920, 1080, new byte[1920 * 1080 * 4]);
+        flash.BgraPixels[0] = 255; flash.BgraPixels[1] = 0; flash.BgraPixels[2] = 255; flash.BgraPixels[3] = 255;
+
+        var top = compositor.Render(scene, _ => red, flash, options, bar, 0);
+        AssertColor(top, 0, 0, 0, 255, 0); // bar above flash at the top-left
+        AssertColor(top, 960, 540, 255, 127, 127); // 50% white over red
+        AssertColor(top, 100, 100, 255, 0, 0); // empty overlay area: backdrop
+
+        var bottom = compositor.Render(scene, _ => red, flash, options, bar, 1040);
+        AssertColor(bottom, 0, 1040, 0, 255, 0); // bar drawn at the bottom edge
+        AssertColor(bottom, 0, 1039, 255, 0, 0); // backdrop just above the bar
+        AssertColor(bottom, 960, 540, 255, 0, 0); // bar region moved away from center
+    }
 }
 
 public class StretchMathTests

ytLive.Tests/SocialBarTests.cs

@@ -1,8 +1,11 @@
 using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.Data.Sqlite;
 using Xunit;
 using ytLive.Models;
 using ytLive.Services;
+using ytLive.ViewModels;
 
 namespace ytLive.Tests;
 
@@ -16,6 +19,102 @@ public class SocialBarTests
         return path;
     }
 
+    /// <summary>Resolves every fediverse domain as Mastodon — the heal test only
+    /// cares that a missing stored software name gets filled in and persisted.</summary>
+    private sealed class MastodonValidator : ISocialValidator
+    {
+        public Task<string?> ResolveFediverseSoftwareAsync(string domain, CancellationToken ct)
+            => Task.FromResult<string?>("mastodon");
+
+        public Task<SocialLookupResult> LookupAsync(SocialService service, string handleOrUrl, CancellationToken ct)
+            => throw new System.NotSupportedException();
+    }
+
+    [Fact]
+    public void SocialBarSnap_Decide_DirectionAndDeadzone()
+    {
+        Assert.Equal(SocialBarPosition.Top, SocialBarSnap.Decide(-10));
+        Assert.Equal(SocialBarPosition.Top, SocialBarSnap.Decide(-6));
+        Assert.Equal(SocialBarPosition.Bottom, SocialBarSnap.Decide(10));
+        Assert.Equal(SocialBarPosition.Bottom, SocialBarSnap.Decide(6));
+        Assert.Null(SocialBarSnap.Decide(5));
+        Assert.Null(SocialBarSnap.Decide(0));
+        Assert.Null(SocialBarSnap.Decide(-5));
+    }
+
+    [Fact]
+    public void SocialBarSnap_Decide_HonorsCustomDeadzone()
+    {
+        Assert.Null(SocialBarSnap.Decide(10, 20));
+        Assert.Equal(SocialBarPosition.Top, SocialBarSnap.Decide(-21, 20));
+    }
+
+    [Fact]
+    public void SocialEntry_FediverseSoftware_SettableUpdatesLogo()
+    {
+        var entry = new SocialEntry
+        {
+            Service = SocialService.Fediverse,
+            Handle = "@gramps@llamachile.tube",
+            ProfileUrl = "https://llamachile.tube/@gramps",
+        };
+        var honeycomb = entry.LogoData;
+        entry.FediverseSoftware = "mastodon";
+        Assert.Equal(SocialServiceIcons.LogoDataForFediverse("mastodon"), entry.LogoData);
+        Assert.NotEqual(honeycomb, entry.LogoData);
+    }
+
+    /// <summary>The single integration test for this branch: a fediverse entry
+    /// persisted with a NULL software name is loaded, healed via the real validator
+    /// seam, and the resolved name is persisted back — surviving a second load.</summary>
+    [Fact]
+    public async Task Socials_HealMissingFediverseSoftware_RoundTripsThroughDb()
+    {
+        var path = TempDbPath();
+        try
+        {
+            var socials = new SocialsConfig();
+            socials.Entries.Add(new SocialEntry
+            {
+                Service = SocialService.Fediverse,
+                Handle = "@gramps@llamachile.tube",
+                ProfileUrl = "https://llamachile.tube/@gramps",
+            });
+            using (var store = new LayoutStore(path))
+                store.Save(new[] { new Scene { Name = "Live" } }, null, socials);
+
+            SocialsConfig? loaded;
+            using (var store = new LayoutStore(path))
+            {
+                store.Load();
+                loaded = store.Socials;
+                Assert.NotNull(loaded);
+                Assert.Null(loaded!.Entries[0].FediverseSoftware);
+            }
+
+            var healed = await MainViewModel.HealFediverseSoftwareAsync(loaded!, new MastodonValidator());
+            Assert.Single(healed);
+            Assert.Equal("mastodon", healed["@gramps@llamachile.tube"]);
+            loaded.Entries[0].FediverseSoftware = healed["@gramps@llamachile.tube"];
+
+            using (var store = new LayoutStore(path))
+                store.Save(new[] { new Scene { Name = "Live" } }, null, loaded);
+
+            using (var store = new LayoutStore(path))
+            {
+                store.Load();
+                var again = store.Socials;
+                Assert.NotNull(again);
+                Assert.Equal("mastodon", again!.Entries[0].FediverseSoftware);
+            }
+        }
+        finally
+        {
+            SqliteConnection.ClearAllPools();
+            if (File.Exists(path)) File.Delete(path);
+        }
+    }
+
     [Fact]
     public void SocialsConfig_RoundTrip_PersistsEntriesAndBarSettings()
     {

ytLive.Tests/SocialValidatorTests.cs

@@ -103,6 +103,39 @@ public class SocialValidatorTests
         Assert.Null(result.FediverseSoftware);
     }
 
+    [Fact]
+    public async Task FediverseSoftware_IdentityDomainSilent_ProbesWellKnownSubdomains()
+    {
+        // The identity domain is a silent landing page (no nodeinfo, no redirect);
+        // the real instance lives on mastodon.<domain> — the probe must find it.
+        var validator = Validator(new StubHandler(request =>
+        {
+            var host = request.RequestUri!.Host;
+            if (host == "mastodon.llamachile.tube")
+            {
+                if (request.RequestUri.AbsolutePath.StartsWith("/.well-known"))
+                    return Json(new { links = new[] { new { rel = "http://nodeinfo.diaspora.software/ns/schema/2.0", href = "https://mastodon.llamachile.tube/nodeinfo/2.0" } } });
+                if (request.RequestUri.AbsolutePath.StartsWith("/nodeinfo"))
+                    return Json(new { software = new { name = "mastodon", version = "4.6.3" } });
+            }
+            return new HttpResponseMessage(HttpStatusCode.NotFound);
+        }));
+
+        var software = await validator.ResolveFediverseSoftwareAsync("llamachile.tube", CancellationToken.None);
+
+        Assert.Equal("mastodon", software);
+    }
+
+    [Fact]
+    public async Task FediverseSoftware_NoSubdomainAnswers_ReturnsNull()
+    {
+        var validator = Validator(new StubHandler(new HttpResponseMessage(HttpStatusCode.NotFound)));
+
+        var software = await validator.ResolveFediverseSoftwareAsync("silent.example", CancellationToken.None);
+
+        Assert.Null(software);
+    }
+
     [Fact]
     public async Task FediverseHandle_CanceledDuringNodeInfo_IsCanceled()
     {

ytLive.Tests/SocialsDialogViewModelTests.cs

@@ -15,6 +15,9 @@ public class SocialsDialogViewModelTests
     {
         public int LookupCount { get; private set; }
 
+        public Task<string?> ResolveFediverseSoftwareAsync(string domain, CancellationToken ct)
+            => Task.FromResult<string?>("mastodon");
+
         public Task<SocialLookupResult> LookupAsync(SocialService service, string handleOrUrl, CancellationToken ct)
         {
             LookupCount++;
@@ -51,6 +54,9 @@ public class SocialsDialogViewModelTests
 
         public Task<SocialLookupResult> LookupAsync(SocialService service, string handleOrUrl, CancellationToken ct)
             => Gate.Task;
+
+        public Task<string?> ResolveFediverseSoftwareAsync(string domain, CancellationToken ct)
+            => Task.FromResult<string?>(null);
     }
 
     private sealed class SignInFake