diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser/GalaxyBrowseSession.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser/GalaxyBrowseSession.cs
new file mode 100644
index 00000000..6349a953
--- /dev/null
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser/GalaxyBrowseSession.cs
@@ -0,0 +1,191 @@
+using System.Collections.Concurrent;
+using MxGateway.Client;
+using MxGateway.Contracts.Proto.Galaxy;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser;
+
+/// <summary>
+///     Galaxy browse over the gateway's <see cref="GalaxyRepositoryClient"/>.
+///     The gateway returns the deployed hierarchy as a flat <see cref="GalaxyObject"/>
+///     list, so this session fetches the full set once on <see cref="RootAsync"/>,
+///     caches it by <c>TagName</c> (and <c>GobjectId</c> for parent lookup), and serves
+///     subsequent <see cref="ExpandAsync"/> calls in-memory. Attribute fetches are
+///     per-object via <c>DiscoverHierarchyAsync(MaxDepth=0, IncludeAttributes=true)</c>.
+///     Owns the supplied <see cref="MxGatewaySession"/> and disposes it best-effort.
+/// </summary>
+internal sealed class GalaxyBrowseSession : IBrowseSession
+{
+    private readonly MxGatewaySession _session;
+    private readonly GalaxyRepositoryClient _client;
+    private readonly ConcurrentDictionary<string, GalaxyObject> _byTagName = new(StringComparer.Ordinal);
+    private readonly ConcurrentDictionary<int, GalaxyObject> _byGobjectId = new();
+    private bool _disposed;
+
+    /// <summary>Opaque token identifying this session in the AdminUI registry.</summary>
+    public Guid Token { get; } = Guid.NewGuid();
+
+    /// <summary>Wall-clock time of the most recent successful Root/Expand/Attributes call.</summary>
+    public DateTime LastUsedUtc { get; private set; } = DateTime.UtcNow;
+
+    /// <summary>
+    ///     Initializes a new session wrapping a connected gateway client. The factory
+    ///     in <c>GalaxyDriverBrowser</c> (Task 9) constructs both the session and the
+    ///     repository client and hands them off here for the session's lifetime.
+    /// </summary>
+    /// <param name="session">Gateway session to dispose when the browse closes.</param>
+    /// <param name="client">Galaxy repository client to query for hierarchy and attributes.</param>
+    internal GalaxyBrowseSession(MxGatewaySession session, GalaxyRepositoryClient client)
+    {
+        _session = session ?? throw new ArgumentNullException(nameof(session));
+        _client = client ?? throw new ArgumentNullException(nameof(client));
+    }
+
+    /// <summary>
+    ///     Fetches the full Galaxy hierarchy from the gateway, populates the cache,
+    ///     and returns the top-level objects (those with no parent in the deployed model).
+    /// </summary>
+    public async Task<IReadOnlyList<BrowseNode>> RootAsync(CancellationToken cancellationToken)
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        var all = await _client.DiscoverHierarchyAsync(
+            new DiscoverHierarchyOptions { IncludeAttributes = false }, cancellationToken)
+            .ConfigureAwait(false);
+
+        // Populate caches so later ExpandAsync calls can resolve children in-memory.
+        foreach (var obj in all)
+        {
+            _byTagName[obj.TagName] = obj;
+            _byGobjectId[obj.GobjectId] = obj;
+        }
+
+        // Roots are objects whose parent isn't part of the returned set (typically
+        // ParentGobjectId == 0 for WinPlatforms / top-level Areas).
+        var roots = all
+            .Where(o => o.ParentGobjectId == 0 || !_byGobjectId.ContainsKey(o.ParentGobjectId))
+            .ToList();
+
+        LastUsedUtc = DateTime.UtcNow;
+        return Project(roots);
+    }
+
+    /// <summary>
+    ///     Returns the direct children of the cached Galaxy object identified by
+    ///     <paramref name="nodeId"/> (the object's <c>TagName</c>). Throws
+    ///     <see cref="ArgumentException"/> if the tag hasn't been handed out by a
+    ///     prior Root/Expand call (i.e. it's not in the cache).
+    /// </summary>
+    public Task<IReadOnlyList<BrowseNode>> ExpandAsync(string nodeId, CancellationToken cancellationToken)
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        if (!_byTagName.TryGetValue(nodeId, out var parent))
+        {
+            throw new ArgumentException(
+                $"Galaxy object '{nodeId}' is not in the current browse-session cache. " +
+                "Re-open the browser or expand its parent first.", nameof(nodeId));
+        }
+
+        var children = _byGobjectId.Values
+            .Where(o => o.ParentGobjectId == parent.GobjectId)
+            .ToList();
+
+        LastUsedUtc = DateTime.UtcNow;
+        return Task.FromResult(Project(children));
+    }
+
+    /// <summary>
+    ///     Fetches the attributes of the Galaxy object identified by <paramref name="nodeId"/>
+    ///     via <c>DiscoverHierarchyAsync(MaxDepth=0, RootTagName=nodeId, IncludeAttributes=true)</c>.
+    ///     Returns an empty list if the gateway has no matching object.
+    /// </summary>
+    public async Task<IReadOnlyList<AttributeInfo>> AttributesAsync(string nodeId, CancellationToken cancellationToken)
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        var rows = await _client.DiscoverHierarchyAsync(
+            new DiscoverHierarchyOptions
+            {
+                RootTagName = nodeId,
+                MaxDepth = 0,
+                IncludeAttributes = true,
+            }, cancellationToken).ConfigureAwait(false);
+
+        LastUsedUtc = DateTime.UtcNow;
+        var obj = rows.FirstOrDefault();
+        if (obj is null) return Array.Empty<AttributeInfo>();
+
+        var result = new List<AttributeInfo>(obj.Attributes.Count);
+        foreach (var attr in obj.Attributes)
+        {
+            var driverType = !string.IsNullOrEmpty(attr.DataTypeName)
+                ? attr.DataTypeName
+                : attr.MxDataType.ToString(System.Globalization.CultureInfo.InvariantCulture);
+            result.Add(new AttributeInfo(
+                Name: attr.AttributeName,
+                DriverDataType: driverType,
+                IsArray: attr.IsArray,
+                SecurityClass: MapSecurityClass(attr.SecurityClassification)));
+        }
+        return result;
+    }
+
+    /// <summary>
+    ///     Projects <see cref="GalaxyObject"/>s to <see cref="BrowseNode"/>s, ensuring
+    ///     every projected object is also written to the by-tag cache so later
+    ///     <see cref="ExpandAsync"/> calls can find it. Galaxy nodes are always
+    ///     <see cref="BrowseNodeKind.Folder"/> — leaves only appear in the attribute
+    ///     side-panel, never in the tree.
+    /// </summary>
+    private IReadOnlyList<BrowseNode> Project(IReadOnlyList<GalaxyObject> nodes)
+    {
+        var result = new List<BrowseNode>(nodes.Count);
+        foreach (var obj in nodes)
+        {
+            // Belt-and-braces: ensure the cache holds every node we hand back so
+            // ExpandAsync can resolve it on the next round-trip.
+            _byTagName[obj.TagName] = obj;
+            _byGobjectId[obj.GobjectId] = obj;
+
+            var displayName = !string.IsNullOrEmpty(obj.ContainedName) ? obj.ContainedName : obj.TagName;
+            var hasChildrenHint = _byGobjectId.Values.Any(o => o.ParentGobjectId == obj.GobjectId);
+            result.Add(new BrowseNode(
+                NodeId: obj.TagName,
+                DisplayName: displayName,
+                Kind: BrowseNodeKind.Folder,
+                HasChildrenHint: hasChildrenHint));
+        }
+        return result;
+    }
+
+    /// <summary>
+    ///     Maps the Galaxy raw security-classification integer to a display string.
+    ///     Buckets: 0=FreeAccess, 1=Operate, 2=Tune, 3=Configure, 4=ViewOnly;
+    ///     anything else surfaces as <c>Unknown(N)</c>.
+    /// </summary>
+    private static string MapSecurityClass(int raw) => raw switch
+    {
+        0 => "FreeAccess",
+        1 => "Operate",
+        2 => "Tune",
+        3 => "Configure",
+        4 => "ViewOnly",
+        _ => $"Unknown({raw})",
+    };
+
+    /// <summary>
+    ///     Idempotently tears down the underlying gateway session. Swallows exceptions
+    ///     on shutdown — the registry's reaper may be racing a client-initiated close.
+    /// </summary>
+    public async ValueTask DisposeAsync()
+    {
+        if (_disposed) return;
+        _disposed = true;
+        try
+        {
+            await _session.DisposeAsync().ConfigureAwait(false);
+        }
+        catch
+        {
+            // Best-effort: a gateway-side close that hits a torn-down channel is normal.
+        }
+    }
+}