Add a "Claude Actions" editor context menu (Explain / Add to Chat)

CLAUDE.md

@@ -178,3 +178,5 @@ claude --version            # record the known-good version
 - `new_file_contents` in `openDiff` is in-memory -> write to a temp file to feed the comparison; write to `new_file_path` only on Accept.
 - Debounce `selection_changed` (~100–200ms) or you'll flood the socket.
 - **HTTP responses to the PowerShell shim/hooks MUST declare `charset=utf-8`** (and the shim additionally decodes raw response bytes as UTF-8 itself): PS 5.1's `Invoke-WebRequest` decodes charset-less responses as Latin-1, which mojibakes every non-ASCII character in every tool result (bit as `Microsoftâ„¢ Edge`, fixed 1.14.0).
+- **VSCT: a `<Menu>` can't be parented directly to another menu's ID** (e.g. `IDM_VS_CTXT_CODEWIN`) - it needs an intermediate `<Group>` parented to that ID, with the `<Menu>` parented to the group (same pattern `ClaudeMenuGroup` uses for the Tools-menu button). Parenting the Menu straight to the menu ID compiles fine and the command still registers (`Commands.Item` finds it, `Commands.Raise` invokes it) but the submenu never renders in the actual context menu - silent, no error anywhere. Caught by literally screenshotting a right-click.
+- **The Exp hive caches the compiled command table.** Editing `.vsct` and redeploying just the DLL isn't enough - new command IDs resolve via `Commands.Item`/`Raise` (proving the package loaded) but won't render in menus until you close devenv and run `devenv /rootsuffix Exp /updateconfiguration` once. Pure C#/XAML logic changes (no `.vsct` edit) don't need this - just close devenv, overwrite the hive's `ClaudeCodeVS.dll`, relaunch.

src/ClaudeCodeVS/Attachments/AttachmentService.cs

@@ -364,7 +364,7 @@ private static string TokSuffix(long? est)
         => est is long t ? $" (≈{(t >= 1000 ? (t / 1000.0).ToString("0.0") + "k" : t.ToString())} tok)" : "";
 
     /// <summary>Workspace-relative forward-slash form, or null when the path is outside the workspace.</summary>
-    private static string? ToWorkspaceRelative(string fullPath)
+    internal static string? ToWorkspaceRelative(string fullPath)
     {
         var ws = Ui.BridgeStatus.Workspace;
         if (string.IsNullOrEmpty(ws)) return null;

src/ClaudeCodeVS/ClaudeCodeVsPackage.cs

@@ -3,6 +3,7 @@
 using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
+using ClaudeCodeVs.Protocol;
 using ClaudeCodeVs.Ui;
 using Microsoft.VisualStudio;
 using Microsoft.VisualStudio.Shell;
@@ -54,6 +55,10 @@ protected override async Task InitializeAsync(CancellationToken cancellationToke
                 new CommandID(PackageGuids.CommandSet, PackageIds.LaunchClaude)));
             mcs.AddCommand(new MenuCommand(OnShowPanel,
                 new CommandID(PackageGuids.CommandSet, PackageIds.ShowPanel)));
+            mcs.AddCommand(new MenuCommand(OnExplain,
+                new CommandID(PackageGuids.CommandSet, PackageIds.Explain)));
+            mcs.AddCommand(new MenuCommand(OnAddToChat,
+                new CommandID(PackageGuids.CommandSet, PackageIds.AddToChat)));
         }
     }
 
@@ -95,6 +100,33 @@ private void OnShowPanel(object sender, EventArgs e)
             ErrorHandler.ThrowOnFailure(frame.Show());
     }
 
+    // Editor right-click ("Claude Code" submenu): Explain stages the selection as a text attachment
+    // with an instruction header (same insert-not-submit staging as a pasted prompt); Add to Chat just
+    // @-mentions the file/line-range in place. Both read SelectionService.Current, kept live by the
+    // MEF TextViewListener.
+    private void OnExplain(object sender, EventArgs e)
+    {
+        ThreadHelper.ThrowIfNotOnUIThread();
+        var sel = Editor.SelectionService.Current;
+        if (sel.IsEmpty)
+        {
+            Log.Warn("Explain: select some code first.");
+            return;
+        }
+        var header = sel.FilePath is null
+            ? "Explain this code:"
+            : $"Explain this code from {System.IO.Path.GetFileName(sel.FilePath)} (lines {sel.StartLine + 1}-{sel.EndLineInclusive + 1}):";
+        JoinableTaskFactory.RunAsync(() => Attachments.AttachmentService.StageTextAsync(header + "\n\n" + sel.Text))
+            .FileAndForget("claudecodevs/explain");
+    }
+
+    private void OnAddToChat(object sender, EventArgs e)
+    {
+        ThreadHelper.ThrowIfNotOnUIThread();
+        JoinableTaskFactory.RunAsync(() => Editor.SelectionService.MentionCurrentAsync())
+            .FileAndForget("claudecodevs/addToChat");
+    }
+
     protected override void Dispose(bool disposing)
     {
         if (disposing)
@@ -115,4 +147,6 @@ internal static class PackageIds
     // Must match the IDSymbol values in VSCommandTable.vsct.
     public const int LaunchClaude = 0x0100;
     public const int ShowPanel = 0x0101;
+    public const int Explain = 0x0102;
+    public const int AddToChat = 0x0103;
 }

src/ClaudeCodeVS/Editor/SelectionService.cs

@@ -43,6 +43,53 @@ public static JToken LatestAsJson()
         lock (Gate) return (_lastNonEmpty ?? _current).ToJson();
     }
 
+    /// <summary>The live selection snapshot, for the editor context-menu commands (Explain / Add to Chat).</summary>
+    public static SelectionInfo Current
+    {
+        get { lock (Gate) return _current; }
+    }
+
+    /// <summary>
+    /// Push an at_mentioned for the current selection (file + line range), or the whole file if nothing
+    /// is selected - the "Add to Chat" context-menu command. Insert-not-submit, same as every other
+    /// at_mentioned in this codebase (CLAUDE.md).
+    /// </summary>
+    public static async Task MentionCurrentAsync()
+    {
+        var server = _server;
+        if (server is null || !server.HasConnections)
+        {
+            Log.Warn("Add to Chat: Claude isn't connected.");
+            return;
+        }
+
+        var info = Current;
+        if (info.FilePath is null)
+        {
+            Log.Warn("Add to Chat: no active file.");
+            return;
+        }
+
+        var mentionPath = Attachments.AttachmentService.ToWorkspaceRelative(info.FilePath) ?? info.FilePath;
+        var @params = new JObject { ["filePath"] = mentionPath };
+        if (!info.IsEmpty)
+        {
+            @params["lineStart"] = info.StartLine;
+            @params["lineEnd"] = info.EndLineInclusive;
+        }
+
+        try
+        {
+            await server.BroadcastNotificationAsync("at_mentioned", @params, CancellationToken.None);
+            var range = info.IsEmpty ? "" : $" (lines {info.StartLine + 1}-{info.EndLineInclusive + 1})";
+            Log.Info($"Add to Chat: mentioned '{System.IO.Path.GetFileName(info.FilePath)}'{range}.");
+        }
+        catch (Exception e)
+        {
+            Log.Warn($"Add to Chat failed: {e.Message}");
+        }
+    }
+
     /// <summary>Record a fresh selection from a focused view and (debounced) push selection_changed.</summary>
     public static void Update(IWpfTextView view)
     {
@@ -98,6 +145,14 @@ internal sealed class SelectionInfo
 
     public bool IsEmpty => Text.Length == 0;
 
+    /// <summary>
+    /// The last line the selection actually covers. <see cref="EndLine"/> is LSP-shaped (exclusive), so
+    /// selecting whole lines parks the end at column 0 of the NEXT line - reporting that one verbatim
+    /// would claim one line too many. Only for human-facing ranges and at_mentioned; the
+    /// <c>selection_changed</c> / getCurrentSelection JSON keeps the exclusive LSP coordinates.
+    /// </summary>
+    public int EndLineInclusive => EndChar == 0 && EndLine > StartLine ? EndLine - 1 : EndLine;
+
     public SelectionInfo(string text, string? filePath, int startLine, int startChar, int endLine, int endChar)
     {
         Text = text;

src/ClaudeCodeVS/VSCommandTable.vsct

@@ -13,8 +13,31 @@
       <Group guid="guidClaudeCmdSet" id="ClaudeMenuGroup" priority="0x0600">
         <Parent guid="guidSHLMainMenu" id="IDM_VS_MENU_TOOLS" />
       </Group>
+      <Group guid="guidClaudeCmdSet" id="ClaudeCtxMenuGroup" priority="0x0100">
+        <Parent guid="guidClaudeCmdSet" id="ClaudeCtxMenu" />
+      </Group>
+      <!-- The Menu below can't be parented directly to a menu ID - it needs a Group in between,
+           same as ClaudeMenuGroup does for the Tools menu placement above. MID priority on purpose:
+           the code editor's right-click menu is the most muscle-memory-sensitive surface in VS, so
+           the submenu sits below the navigation block (Go To Definition etc.), roughly where
+           Copilot's entries live - never at the very top. -->
+      <Group guid="guidClaudeCmdSet" id="ClaudeCtxTopGroup" priority="0x0200">
+        <Parent guid="guidSHLMainMenu" id="IDM_VS_CTXT_CODEWIN" />
+      </Group>
     </Groups>
 
+    <!-- Editor right-click submenu: "Claude Code" -> Explain / Add to Chat. Named for the brand,
+         matching the Tools and View > Other Windows entries (one brand, not a third variant). -->
+    <Menus>
+      <Menu guid="guidClaudeCmdSet" id="ClaudeCtxMenu" priority="0x0001" type="Menu">
+        <Parent guid="guidClaudeCmdSet" id="ClaudeCtxTopGroup" />
+        <Strings>
+          <ButtonText>Claude Code</ButtonText>
+          <CommandName>Claude Code</CommandName>
+        </Strings>
+      </Menu>
+    </Menus>
+
     <Buttons>
       <Button guid="guidClaudeCmdSet" id="LaunchClaudeId" priority="0x0100" type="Button">
         <Parent guid="guidClaudeCmdSet" id="ClaudeMenuGroup" />
@@ -36,15 +59,36 @@
           <ButtonText>Claude Code</ButtonText>
         </Strings>
       </Button>
+      <Button guid="guidClaudeCmdSet" id="ExplainId" priority="0x0100" type="Button">
+        <Parent guid="guidClaudeCmdSet" id="ClaudeCtxMenuGroup" />
+        <Icon guid="ImageCatalogGuid" id="StatusHelp" />
+        <CommandFlag>IconIsMoniker</CommandFlag>
+        <Strings>
+          <ButtonText>Explain</ButtonText>
+        </Strings>
+      </Button>
+      <Button guid="guidClaudeCmdSet" id="AddToChatId" priority="0x0110" type="Button">
+        <Parent guid="guidClaudeCmdSet" id="ClaudeCtxMenuGroup" />
+        <Icon guid="ImageCatalogGuid" id="Comment" />
+        <CommandFlag>IconIsMoniker</CommandFlag>
+        <Strings>
+          <ButtonText>Add to Chat</ButtonText>
+        </Strings>
+      </Button>
     </Buttons>
   </Commands>
 
   <Symbols>
     <GuidSymbol name="guidClaudeCodeVsPackage" value="{d9032717-8a83-4ab5-9b63-2fe9d9a78481}" />
     <GuidSymbol name="guidClaudeCmdSet" value="{9495bbbb-756d-4dc4-807d-1408d50e7d33}">
       <IDSymbol name="ClaudeMenuGroup" value="0x1020" />
+      <IDSymbol name="ClaudeCtxMenu" value="0x1021" />
+      <IDSymbol name="ClaudeCtxMenuGroup" value="0x1022" />
+      <IDSymbol name="ClaudeCtxTopGroup" value="0x1023" />
       <IDSymbol name="LaunchClaudeId" value="0x0100" />
       <IDSymbol name="ShowPanelId" value="0x0101" />
+      <IDSymbol name="ExplainId" value="0x0102" />
+      <IDSymbol name="AddToChatId" value="0x0103" />
     </GuidSymbol>
   </Symbols>
 </CommandTable>