feat(gui): Nexus update badges and check-for-updates action

docs/knowledgebase/README.md

@@ -44,7 +44,7 @@ Use these when citing findings in plans, PRs, or audits:
 
 - [Install lifecycle](install-lifecycle.md) — wizard page order, `InstallationService`, checkpoints, widescreen, CLI flags
 - [Download system](download-system.md) — ResourceRegistry, handler order, `DownloadCacheService`, GUI vs CLI
-- [Mod update checking](update-checking.md) — `NexusApiClient`, `ResourceMetadata` version fields, `ModUpdateCheckService`
+- [Mod update checking](update-checking.md) — `NexusApiClient`, `ModUpdateCheckService`, mod list update badges, menu check action
 - [Install profiles](install-profiles.md) — named loadouts, `ProfileService` capture/apply, `ProfileManagerDialog`
 - [Managed deployment engine](managed-deployment.md) — hardlink deploy, per-component manifests, uninstall/purge (Phase 4 slice 1)
 - [File-level conflicts](file-conflicts.md) — `FileConflictAnalyzer` dry-run VFS attribution and `ConflictsDialog` results UI
@@ -84,7 +84,7 @@ Use these when citing findings in plans, PRs, or audits:
 
 ### Plans (implementation history)
 
-- [docs/plans/](../plans/) — dated plans with requirements and status frontmatter
+- [docs/plans/](../plans/) — dated plans with requirements and status frontmatter; active parity tracker: [vortex-mo2-feature-parity-living-plan.md](../plans/vortex-mo2-feature-parity-living-plan.md)
 
 #### June 2026 arcs (rebrand closure + MainWindow extraction)
 

docs/knowledgebase/update-checking.md

@@ -1,6 +1,6 @@
 # Mod update checking
 
-How ModSync knows whether a tracked Nexus Mods component has a newer version. Core-only as of plan 117; no GUI surface yet.
+How ModSync knows whether a tracked Nexus Mods component has a newer version available.
 
 ## Components
 
@@ -9,6 +9,9 @@ How ModSync knows whether a tracked Nexus Mods component has a newer version. Co
 | `NexusApiClient` | `src/ModSync.Core/Services/Download/NexusApiClient.cs` | `[REPO]` Standalone typed client for the Nexus REST API (`/games/{domain}/mods/{id}.json`, `files.json`, `md5_search`, `/users/validate.json`). Handles 429 Retry-After (single retry) and tracks `X-RL-Daily-Remaining` / `X-RL-Hourly-Remaining` as `DailyRemaining` / `HourlyRemaining`. |
 | `ResourceMetadata` version fields | `src/ModSync.Core/ModComponent.cs` | `[REPO]` `ModVersion` (baseline), `LatestKnownVersion`, `LastUpdateCheck`, `UpdateAvailable` — plain serializable properties on each `ResourceRegistry` entry. |
 | `ModUpdateCheckService` | `src/ModSync.Core/Services/ModUpdateCheckService.cs` | `[REPO]` Batch checker: extracts `(gameDomain, modId)` from `nexusmods.com/{domain}/mods/{id}` URLs in each component's `ResourceRegistry`, fetches mod info once per unique mod across all components, writes results onto the metadata, stops early when the rate-limit budget hits zero. |
+| `ModComponent.NexusUpdateAvailable` | `src/ModSync.Core/ModComponent.cs` | `[REPO]` Computed flag for list binding; call `NotifyNexusUpdateStateChanged()` after mutating metadata. |
+| Mod list badge | `src/ModSync.GUI/Controls/ModListItem.axaml` | `[REPO]` "Update" badge when `NexusUpdateAvailable` is true. |
+| Menu action | `src/ModSync.GUI/Services/MenuBuilderService.cs` | `[REPO]` **Check for Nexus Updates** runs the batch checker (requires API key) and refreshes badges. |
 
 ## Semantics
 
@@ -22,7 +25,7 @@ How ModSync knows whether a tracked Nexus Mods component has a newer version. Co
 
 - `ModComponent.ResourceRegistry` getter returns a defensive copy of the dictionary, but the `ResourceMetadata` values are shared references; the service mutates them in place — that is the supported persistence path. `[REPO]`
 - `ModSync.Core` compiles as C# 7.3 and multi-targets net48; keep additions to these classes within that language level. `[REPO]`
-- `NexusModsDownloadHandler` still has its own inline API code; migrating it onto `NexusApiClient` is a planned follow-up, as are endorsements and GUI update badges (see `docs/plans/2026-06-12-117-nexus-update-checks-plan.md`). `[REPO]`
+- `NexusModsDownloadHandler` still has its own inline API code; migrating it onto `NexusApiClient` is a planned follow-up, as are endorsements and persisting check results via `DownloadCacheService`. `[REPO]`
 
 ## Tests
 

docs/plans/2026-06-14-122-update-badges-plan.md

@@ -0,0 +1,37 @@
+---
+title: "feat: Nexus update badges and check-for-updates menu action"
+type: feat
+status: completed
+date: 2026-06-14
+origin: docs/plans/2026-06-12-117-nexus-update-checks-plan.md (Phase 2, GUI slice)
+branch: feat/update-badges-gui
+---
+
+# feat: Nexus update badges and check-for-updates menu action
+
+Second sub-slice of Phase 2 (mod version tracking + update checks) of the Vortex/MO2
+feature-parity roadmap.
+
+## Goal
+
+Surface `ModUpdateCheckService` results in the mod list and expose a user-triggered
+"Check for Nexus Updates" action without changing download or install pipelines.
+
+## Landed
+
+- `ModComponent.NexusUpdateAvailable` + `NotifyNexusUpdateStateChanged()` for list binding.
+- `ModListItem` "Update" badge when any tracked Nexus resource has `UpdateAvailable`.
+- `MenuBuilderService` common menu item runs `ModUpdateCheckService` and refreshes badges.
+- Knowledgebase and living-plan delta updated.
+
+## Out of scope
+
+- Sidebar-only badges, endorsement UI, persisting check results via `DownloadCacheService`.
+- Migrating `NexusModsDownloadHandler` onto `NexusApiClient`.
+- Desktop GUI validation of badge rendering (headless agent skipped).
+
+## Tests
+
+```bash
+dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter "FullyQualifiedName~ModUpdateCheck"
+```

docs/plans/vortex-mo2-feature-parity-living-plan.md

@@ -0,0 +1,50 @@
+---
+title: "Vortex/MO2 feature parity — living plan"
+type: living-plan
+status: active
+date: 2026-06-14
+origin: Vortex/MO2 feature-parity roadmap (phases 1–7)
+---
+
+# Vortex/MO2 feature parity — living plan
+
+Single authoritative tracker for parity work. Individual slice plans under
+`docs/plans/` remain the implementation record; this file holds status and next steps only.
+
+## Phase status
+
+| Phase | Area | Status |
+|-------|------|--------|
+| 1 | nxm protocol handler | Merged (#155–#164) |
+| 2 | Nexus update checks | Core merged (#156); GUI badges in PR #167 (plan 122) |
+| 3 | Profiles | Merged (#157) |
+| 4 | Managed deployment | **Merged** (#158); install wiring deferred |
+| 5 | File conflicts | Core #160 + GUI #165 merged |
+| 6 | FOMOD | Parser + installer dialog merged (#166); archive hook deferred |
+| 7 | (roadmap tail) | Per slice plans |
+
+## Delta update (2026-06-14)
+
+### Landed
+
+- FOMOD installer dialog + parser stack (#166).
+- Conflicts analysis GUI (#165).
+- Nexus update check core (#156).
+- **Update badges + "Check for Nexus Updates" menu action** (plan 122, branch `feat/update-badges-gui`).
+
+### Partial
+
+- Managed deployment engine (#158): rebased on master, CI pending → merge when green; no install-path wiring yet.
+- FOMOD: no automatic archive enumeration hook in download flow.
+- Update checking: no endorsement UI, no cache persistence of check results.
+
+### Next
+
+1. Merge PR #158 when CI is green.
+2. Wire `DeploymentService` into install execution + optional GUI toggle (plan 116 slice 2).
+3. FOMOD archive discovery hook in download/archive enumeration.
+4. Migrate `NexusModsDownloadHandler` to `NexusApiClient` when download handler branch is stable.
+
+## Superseded
+
+- PR #162 closed; superseded by #166 (FOMOD dialog includes parser stack).

src/ModSync.Core/ModComponent.cs

@@ -738,6 +738,31 @@ public bool IsValidating
                 OnPropertyChanged();
             }
         }
+
+        /// <summary>
+        /// True when any <see cref="ResourceRegistry"/> entry has
+        /// <see cref="ResourceMetadata.UpdateAvailable"/> set after a Nexus update check.
+        /// </summary>
+        [JsonIgnore]
+        public bool NexusUpdateAvailable
+        {
+            get
+            {
+                foreach (ResourceMetadata metadata in _resourceRegistry.Values)
+                {
+                    if (metadata != null && metadata.UpdateAvailable)
+                    {
+                        return true;
+                    }
+                }
+
+                return false;
+            }
+        }
+
+        /// <summary>Raises <see cref="PropertyChanged"/> for <see cref="NexusUpdateAvailable"/> after metadata mutation.</summary>
+        public void NotifyNexusUpdateStateChanged() => OnPropertyChanged(nameof(NexusUpdateAvailable));
+
         public bool WidescreenOnly
         {
             get => _widescreenOnly;

src/ModSync.GUI/Controls/ModListItem.axaml

@@ -43,7 +43,7 @@
                 <!--  Main mod info (always visible)  -->
                 <Grid x:Name="MainModInfo" Grid.Row="0" RowDefinitions="Auto,Auto">
                     <!--  Row 0: main info across 6 columns  -->
-                    <Grid Grid.Row="0" ColumnDefinitions="Auto,Auto,*,Auto,Auto,Auto">
+                    <Grid Grid.Row="0" ColumnDefinitions="Auto,Auto,*,Auto,Auto,Auto,Auto">
 
                         <!--  Checkbox  -->
                         <CheckBox
@@ -86,19 +86,38 @@
                             </TextBlock.Text>
                         </TextBlock>
 
+                        <!--  Nexus update badge  -->
+                        <Border
+                            Grid.Column="3"
+                            Margin="8,0,4,0"
+                            Padding="6,2"
+                            VerticalAlignment="Top"
+                            Classes="mod-list-item-badge"
+                            CornerRadius="6"
+                            IsVisible="{Binding NexusUpdateAvailable}"
+                            ToolTip.Tip="A newer version is available on Nexus Mods">
+                            <TextBlock
+                                HorizontalAlignment="Center"
+                                VerticalAlignment="Center"
+                                FontSize="10"
+                                FontWeight="Medium"
+                                Text="Update"
+                                TextTrimming="CharacterEllipsis" />
+                        </Border>
+
                         <!--  Validation Status Icon  -->
                         <TextBlock
                             x:Name="ValidationIcon"
-                            Grid.Column="3"
-                            Margin="8,0,8,0"
+                            Grid.Column="4"
+                            Margin="4,0,8,0"
                             VerticalAlignment="Top"
                             FontSize="14"
                             IsVisible="False" />
 
                         <!--  Drag Handle (Editor Mode Only)  -->
                         <TextBlock
                             x:Name="DragHandle"
-                            Grid.Column="4"
+                            Grid.Column="5"
                             VerticalAlignment="Center"
                             Classes="mod-list-item-drag-handle"
                             Cursor="Hand"
@@ -111,7 +130,7 @@
                         <!--  Download Button  -->
                         <Button
                             x:Name="DownloadButton"
-                            Grid.Column="5"
+                            Grid.Column="6"
                             Width="24"
                             Height="24"
                             Margin="4,0,0,0"

src/ModSync.GUI/Services/MenuBuilderService.cs

@@ -4,7 +4,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
+using System.Net.Http;
 using System.Threading.Tasks;
 
 using Avalonia.Controls;
@@ -13,6 +15,7 @@
 
 using ModSync.Core;
 using ModSync.Core.Services;
+using ModSync.Core.Services.Download;
 using ModSync.Dialogs;
 
 using ReactiveUI;
@@ -344,6 +347,63 @@ await InformationDialog.ShowInformationDialogAsync(
                     }
                 }),
             });
+
+            _ = items.Add(new MenuItem
+            {
+                Header = "🔔 Check for Nexus Updates",
+                Command = ReactiveCommand.CreateFromTask(RunNexusUpdateCheckAsync),
+            });
+        }
+
+        private async Task RunNexusUpdateCheckAsync()
+        {
+            if (string.IsNullOrWhiteSpace(MainConfig.NexusModsApiKey))
+            {
+                await InformationDialog.ShowInformationDialogAsync(
+                    _parentWindow,
+                    "Set a Nexus Mods API key in Settings before checking for updates.");
+                return;
+            }
+
+            List<ModComponent> mods = _modManagementService.SearchMods(string.Empty);
+            using (var httpClient = new HttpClient())
+            {
+                var apiClient = new NexusApiClient(httpClient, MainConfig.NexusModsApiKey);
+                var updateService = new ModUpdateCheckService(apiClient);
+                ModUpdateCheckResult result = await updateService.CheckForUpdatesAsync(mods).ConfigureAwait(true);
+
+                foreach (ModComponent component in mods)
+                {
+                    component.NotifyNexusUpdateStateChanged();
+                }
+
+                string summary = string.Format(
+                    CultureInfo.InvariantCulture,
+                    "Nexus update check complete.\n\nChecked: {0}\nSkipped (non-Nexus): {1}\nUpdates found: {2}",
+                    result.CheckedCount,
+                    result.SkippedCount,
+                    result.UpdatesFound.Count);
+
+                if (result.RateLimitReached)
+                {
+                    summary += "\n\nStopped early: Nexus API rate limit reached.";
+                }
+
+                if (result.Errors.Count > 0)
+                {
+                    summary += string.Format(
+                        CultureInfo.InvariantCulture,
+                        "\n\nErrors ({0}):\n{1}",
+                        result.Errors.Count,
+                        string.Join("\n", result.Errors.Take(5)));
+                    if (result.Errors.Count > 5)
+                    {
+                        summary += string.Format(CultureInfo.InvariantCulture, "\n… and {0} more.", result.Errors.Count - 5);
+                    }
+                }
+
+                await InformationDialog.ShowInformationDialogAsync(_parentWindow, summary);
+            }
         }
 
         [System.Diagnostics.CodeAnalysis.SuppressMessage("Design", "MA0051:Method is too long", Justification = "<Pending>")]

src/ModSync.Tests/ModUpdateCheckServiceTests.cs

@@ -257,6 +257,25 @@ public async Task CheckForUpdatesAsync_ApiError_RecordedAndOtherModsStillChecked
             });
         }
 
+        [Test]
+        public void NexusUpdateAvailable_ReflectsResourceMetadataFlags()
+        {
+            var metadataWithUpdate = new ResourceMetadata { UpdateAvailable = true };
+            var metadataWithoutUpdate = new ResourceMetadata { UpdateAvailable = false };
+            ModComponent withUpdate = CreateComponent(
+                "Has Update",
+                ("https://www.nexusmods.com/kotor/mods/1", metadataWithUpdate));
+            ModComponent withoutUpdate = CreateComponent(
+                "No Update",
+                ("https://www.nexusmods.com/kotor/mods/2", metadataWithoutUpdate));
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(withUpdate.NexusUpdateAvailable, Is.True);
+                Assert.That(withoutUpdate.NexusUpdateAvailable, Is.False);
+            });
+        }
+
         [Test]
         public void CheckForUpdatesAsync_NullComponents_Throws()
         {