diff --git a/DiskArc/Arc/AppleLink.cs b/DiskArc/Arc/AppleLink.cs
index c270fb2..76e44fe 100644
--- a/DiskArc/Arc/AppleLink.cs
+++ b/DiskArc/Arc/AppleLink.cs
@@ -293,5 +293,8 @@ public void AddPart(IFileEntry entry, FilePart part, IPartSource partSource,
         public void DeletePart(IFileEntry entry, FilePart part) {
             throw new InvalidOperationException("This archive format is read-only");
         }
+
+        // IArchive
+        public string? DebugDump() { return null; }
     }
 }
diff --git a/DiskArc/Arc/AppleSingle.cs b/DiskArc/Arc/AppleSingle.cs
index 801f4b1..38e4f17 100644
--- a/DiskArc/Arc/AppleSingle.cs
+++ b/DiskArc/Arc/AppleSingle.cs
@@ -429,5 +429,8 @@ private void CheckModAccess(IFileEntry ientry) {
                 Debug.Assert(entry.ChangeObject != null);
             }
         }
+
+        // IArchive
+        public string? DebugDump() { return null; }
     }
 }
diff --git a/DiskArc/Arc/AudioRecording.cs b/DiskArc/Arc/AudioRecording.cs
index eb8d07e..272865f 100644
--- a/DiskArc/Arc/AudioRecording.cs
+++ b/DiskArc/Arc/AudioRecording.cs
@@ -397,5 +397,8 @@ public void AddPart(IFileEntry entry, FilePart part, IPartSource partSource,
         public void DeletePart(IFileEntry entry, FilePart part) {
             throw new InvalidOperationException("This archive format is read-only");
         }
+
+        // IArchive
+        public string? DebugDump() { return null; }
     }
 }
diff --git a/DiskArc/Arc/Binary2.cs b/DiskArc/Arc/Binary2.cs
index 8200068..6341b79 100644
--- a/DiskArc/Arc/Binary2.cs
+++ b/DiskArc/Arc/Binary2.cs
@@ -614,6 +614,9 @@ public void DeletePart(IFileEntry ientry, FilePart part) {
             IsReconstructionNeeded = true;
         }
 
+        // IArchive
+        public string? DebugDump() { return null; }
+
         /// <summary>
         /// Confirms that we are allowed to modify this entry.
         /// </summary>
diff --git a/DiskArc/Arc/GZip.cs b/DiskArc/Arc/GZip.cs
index eca527a..e8e1186 100644
--- a/DiskArc/Arc/GZip.cs
+++ b/DiskArc/Arc/GZip.cs
@@ -373,5 +373,8 @@ public static string StripGZExtension(string pathName) {
                 return pathName;
             }
         }
+
+        // IArchive
+        public string? DebugDump() { return null; }
     }
 }
diff --git a/DiskArc/Arc/MacBinary.cs b/DiskArc/Arc/MacBinary.cs
index 42d5e9f..5fd1215 100644
--- a/DiskArc/Arc/MacBinary.cs
+++ b/DiskArc/Arc/MacBinary.cs
@@ -227,5 +227,8 @@ public void AddPart(IFileEntry entry, FilePart part, IPartSource partSource,
         public void DeletePart(IFileEntry entry, FilePart part) {
             throw new InvalidOperationException("This archive format is read-only");
         }
+
+        // IArchive
+        public string? DebugDump() { return null; }
     }
 }
diff --git a/DiskArc/Arc/NuFX.cs b/DiskArc/Arc/NuFX.cs
index 4d1b1df..1fa98d0 100644
--- a/DiskArc/Arc/NuFX.cs
+++ b/DiskArc/Arc/NuFX.cs
@@ -747,6 +747,9 @@ public void DeletePart(IFileEntry ientry, FilePart part) {
             ((NuFX_FileEntry)ientry).DeletePart(part);
         }
 
+        // IArchive
+        public string? DebugDump() { return null; }
+
         /// <summary>
         /// Confirms that we are allowed to modify this entry.
         /// </summary>
diff --git a/DiskArc/Arc/Zip.cs b/DiskArc/Arc/Zip.cs
index e7d26ce..bfcb5f1 100644
--- a/DiskArc/Arc/Zip.cs
+++ b/DiskArc/Arc/Zip.cs
@@ -664,6 +664,9 @@ public void DeletePart(IFileEntry ientry, FilePart part) {
             ((Zip_FileEntry)ientry).DeletePart();
         }
 
+        // IArchive
+        public string? DebugDump() { return null; }
+
         /// <summary>
         /// Confirms that we are allowed to modify this entry.
         /// </summary>
diff --git a/DiskArc/FS/CPM.cs b/DiskArc/FS/CPM.cs
index a8dbb99..d0a9321 100644
--- a/DiskArc/FS/CPM.cs
+++ b/DiskArc/FS/CPM.cs
@@ -427,6 +427,9 @@ public override string ToString() {
             return "[CP/M" + rawStr + "]";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return null; }
+
         // IDisposable generic finalizer.
         ~CPM() {
             Dispose(false);
diff --git a/DiskArc/FS/DOS.cs b/DiskArc/FS/DOS.cs
index 271c29c..685002d 100644
--- a/DiskArc/FS/DOS.cs
+++ b/DiskArc/FS/DOS.cs
@@ -383,6 +383,9 @@ public override string ToString() {
             return "[DOS " + id + "]";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return null; }
+
 
         // IDisposable generic finalizer.
         ~DOS() {
diff --git a/DiskArc/FS/Gutenberg.cs b/DiskArc/FS/Gutenberg.cs
index 488e3cb..7710416 100644
--- a/DiskArc/FS/Gutenberg.cs
+++ b/DiskArc/FS/Gutenberg.cs
@@ -173,6 +173,9 @@ public override string ToString() {
             return "[Gutenberg (" + id + ")]";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return null; }
+
         // IDisposable generic finalizer.
         ~Gutenberg() {
             Dispose(false);
diff --git a/DiskArc/FS/HFS.cs b/DiskArc/FS/HFS.cs
index 7907fee..ac4a48a 100644
--- a/DiskArc/FS/HFS.cs
+++ b/DiskArc/FS/HFS.cs
@@ -225,6 +225,9 @@ public override string ToString() {
             return "[HFS vol: " + id + "]";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return HFS_Dump.Dump(this); }
+
         // IDisposable generic finalizer.
         ~HFS() {
             Dispose(false);
diff --git a/DiskArc/FS/HFS_Dump.cs b/DiskArc/FS/HFS_Dump.cs
index 51fb217..5c3708a 100644
--- a/DiskArc/FS/HFS_Dump.cs
+++ b/DiskArc/FS/HFS_Dump.cs
@@ -53,6 +53,7 @@ public static string Dump(HFS fs) {
             sb.AppendLine("Total Files        : " + mdb.FileCount);
             sb.AppendLine("Total Dirs         : " + mdb.DirCount);
             sb.AppendLine("Next CNID          : " + mdb.NextCatalogID);
+            sb.AppendLine("Blessed system CNID: " + mdb.FndrInfo[0]);
 
             sb.AppendLine("Vol Bitmap Start   : " + mdb.VolBitmapStart);
             sb.AppendLine("Free Blocks        : " + mdb.FreeBlocks);
diff --git a/DiskArc/FS/HFS_MDB.cs b/DiskArc/FS/HFS_MDB.cs
index d9ae281..4fff80e 100644
--- a/DiskArc/FS/HFS_MDB.cs
+++ b/DiskArc/FS/HFS_MDB.cs
@@ -212,6 +212,13 @@ public uint DirCount {
 
         /// <summary>drFndrInfo: information used by the Macintosh Finder.</summary>
         private uint[] drFndrInfo = new uint[8];
+        public uint[] FndrInfo {
+            get {
+                uint[] copy = new uint[8];
+                Array.Copy(drFndrInfo, copy, drFndrInfo.Length);
+                return copy;
+            }
+        }
 
         /// <summary>drVCSize / drEmbedSigWord: originally, size (in allocation blocks) of the
         /// volume cache.  Changed to embedded volume signature.</summary>
diff --git a/DiskArc/FS/MFS.cs b/DiskArc/FS/MFS.cs
index f123208..6480334 100644
--- a/DiskArc/FS/MFS.cs
+++ b/DiskArc/FS/MFS.cs
@@ -163,6 +163,9 @@ public override string ToString() {
             return "[MFS (" + id + ")]";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return null; }
+
         // IDisposable generic finalizer.
         ~MFS() {
             Dispose(false);
diff --git a/DiskArc/FS/Pascal.cs b/DiskArc/FS/Pascal.cs
index 5077481..d21a68c 100644
--- a/DiskArc/FS/Pascal.cs
+++ b/DiskArc/FS/Pascal.cs
@@ -253,6 +253,9 @@ public override string ToString() {
             return "[Pascal vol '" + id + "']";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return null; }
+
         // IDisposable generic finalizer.
         ~Pascal() {
             Dispose(false);
diff --git a/DiskArc/FS/ProDOS.cs b/DiskArc/FS/ProDOS.cs
index 994bf82..f8d1b61 100644
--- a/DiskArc/FS/ProDOS.cs
+++ b/DiskArc/FS/ProDOS.cs
@@ -246,6 +246,9 @@ public override string ToString() {
             return "[ProDOS vol '" + id + "']";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return null; }
+
         // IDisposable generic finalizer.
         ~ProDOS() {
             Dispose(false);
diff --git a/DiskArc/FS/RDOS.cs b/DiskArc/FS/RDOS.cs
index 8804902..0bb3f1d 100644
--- a/DiskArc/FS/RDOS.cs
+++ b/DiskArc/FS/RDOS.cs
@@ -254,6 +254,9 @@ public override string ToString() {
             return "[RDOS (" + id + ")]";
         }
 
+        // IFileSystem
+        public string? DebugDump() { return null; }
+
         // IDisposable generic finalizer.
         ~RDOS() {
             Dispose(false);
diff --git a/DiskArc/IArchive.cs b/DiskArc/IArchive.cs
index cf6b45c..abfb3ba 100644
--- a/DiskArc/IArchive.cs
+++ b/DiskArc/IArchive.cs
@@ -296,5 +296,11 @@ void AddPart(IFileEntry entry, Defs.FilePart part, IPartSource partSource,
         /// <exception cref="NotSupportedException">This type of archive does not allow this
         ///   part.</exception>
         void DeletePart(IFileEntry entry, Defs.FilePart part);
+
+        /// <summary>
+        /// Generates detailed human-readable information about the archive.
+        /// </summary>
+        /// <returns>Formatted text, or null if not implemented.</returns>
+        string? DebugDump();
     }
 }
diff --git a/DiskArc/IFileSystem.cs b/DiskArc/IFileSystem.cs
index 13df2f0..884331a 100644
--- a/DiskArc/IFileSystem.cs
+++ b/DiskArc/IFileSystem.cs
@@ -399,5 +399,11 @@ enum FileAccessMode {
         /// Closes all open files.
         /// </summary>
         void CloseAll();
+
+        /// <summary>
+        /// Generates detailed human-readable information about the filesystem.
+        /// </summary>
+        /// <returns>Formatted text, or null if not implemented.</returns>
+        string? DebugDump();
     }
 }
diff --git a/cp2/CP2Main.cs b/cp2/CP2Main.cs
index ed1d8b8..7bf6852 100644
--- a/cp2/CP2Main.cs
+++ b/cp2/CP2Main.cs
@@ -247,11 +247,16 @@ public Command(string[] names, string summary, string usage, bool needsArchive,
                 usage: "",
                 needsArchive: false, acceptsMultipleArgs: false,
                 handler: HandleCrash),
+            new Command(names: new string[] { "debug-show-info" },
+                summary: "displays detailed archive-specific information",
+                usage: "<ext-archive>",
+                needsArchive: true, acceptsMultipleArgs: false,
+                handler: DebugCmd.HandleShowInfo),
             new Command(names: new string[] { "debug-wtree" },
                 summary: "displays work tree for an archive",
                 usage: "<archive>",
                 needsArchive: true, acceptsMultipleArgs: false,
-                handler: Tests.DebugWorkTree.HandleDumpTree),
+                handler: DebugCmd.HandleDumpWTree),
             new Command(names: new string[] { "debug-test" },
                 summary: "executes program tests",
                 usage: "",
diff --git a/cp2/Tests/DebugWorkTree.cs b/cp2/DebugCmd.cs
similarity index 56%
rename from cp2/Tests/DebugWorkTree.cs
rename to cp2/DebugCmd.cs
index d0d8832..9a21571 100644
--- a/cp2/Tests/DebugWorkTree.cs
+++ b/cp2/DebugCmd.cs
@@ -17,29 +17,90 @@
 using System.Diagnostics;
 
 using AppCommon;
-using CommonUtil;
+using DiskArc.Arc;
+using DiskArc.Multi;
 using DiskArc;
 using static AppCommon.WorkTree;
 
-namespace cp2.Tests {
-    public static class DebugWorkTree {
+namespace cp2 {
+    public static class DebugCmd {
         /// <summary>
-        /// Handles "debug-wtree" command.
+        /// Handles "debug-show-info" command.
         /// </summary>
-        public static bool HandleDumpTree(string cmdName, string[] args, ParamsBag parms) {
+        public static bool HandleShowInfo(string cmdName, string[] args, ParamsBag parms) {
+            Debug.Assert(args.Length == 1);
+            if (!ExtArchive.OpenExtArc(args[0], false, true, parms, out DiskArcNode? rootNode,
+                    out DiskArcNode? leafNode, out object? leaf, out IFileEntry endDirEntry)) {
+                return false;
+            }
+            Debug.Assert(rootNode != null && leaf != null);
+
+            using (rootNode) {
+                string? hdrStr = null;
+                string? outStr = null;
+                if (leaf is IArchive) {
+                    IArchive archive = (IArchive)leaf;
+                    hdrStr = "--- " + ThingString.IArchive(archive) + " ---";
+                    outStr = archive.DebugDump();
+                } else if (leaf is IDiskImage) {
+                    IDiskImage disk = (IDiskImage)leaf;
+                    if (disk.Contents is IFileSystem) {
+                        IFileSystem fs = (IFileSystem)disk.Contents;
+                        hdrStr = "--- " + ThingString.IFileSystem(fs) + " ---";
+                        outStr = fs.DebugDump();
+                    } else if (disk.Contents is IMultiPart) {
+                        outStr = "No info available for multi-part filesystem.";
+                    } else {
+                        Console.Error.WriteLine("Error: disk image contents not recognized");
+                        return false;
+                    }
+                } else if (leaf is Partition) {
+                    Partition part = (Partition)leaf;
+                    if (part.FileSystem == null) {
+                        part.AnalyzePartition();
+                    }
+                    if (part.FileSystem != null) {
+                        hdrStr = "--- " + ThingString.IFileSystem(part.FileSystem) + " ---";
+                        outStr = part.FileSystem.DebugDump();
+                    } else {
+                        outStr = "Partition has unknown contents.";
+                    }
+                } else {
+                    Console.Error.WriteLine("Internal issue: what is " + leaf);
+                    Debug.Assert(false);
+                    return false;
+                }
+                if (hdrStr != null) {
+                    Console.WriteLine(hdrStr);
+                }
+                if (outStr != null) {
+                    Console.WriteLine(outStr);
+                } else {
+                    Console.WriteLine("Debug info not available.");
+                }
+                return true;
+            }
+        }
+
+
+        /// <summary>
+        /// Handles "debug-wtree" command.  This displays the WorkTree structure, which is
+        /// only used by the GUI app.
+        /// </summary>
+        public static bool HandleDumpWTree(string cmdName, string[] args, ParamsBag parms) {
             if (args.Length != 1) {
                 CP2Main.ShowUsage(cmdName);
                 return false;
             }
 
-            string extArchive = args[0];
+            string fileName = args[0];  // not processing ext-archive strings
 
             // Include the config parameters in the closure.
             DepthLimiter limiter =
                 delegate (DepthParentKind parentKind, DepthChildKind childKind) {
                     return DepthLimit(parentKind, childKind, parms.Depth);
-            };
-            using (WorkTree tree = new WorkTree(extArchive, limiter, true, null, parms.AppHook)) {
+                };
+            using (WorkTree tree = new WorkTree(fileName, limiter, true, null, parms.AppHook)) {
                 Console.Write(tree.GenerateTreeSummary());
             }