Let a session's transport say what it negotiated

ISshConnection and ISftpSession both carry Cipher now — the server-to-client
algorithm off SSH.NET's own ConnectionInfo, captured once because a rekey is
not an event that library raises — and TerminalWorkspace.GetSessionFacts hands
that plus the host key's algorithm back per session, without ever handing over
the connection itself. Nothing reads either yet; the status bar that will is
the next commit.

src/DodoSSH.Client.Ssh/SftpSession.cs

@@ -265,6 +265,17 @@ public interface ISftpSession : IRemoteFileStore
 {
     /// <summary>The host key that was accepted for this session.</summary>
     HostKeyPresentation HostKey { get; }
+
+    /// <summary>
+    /// The negotiated server-to-client encryption algorithm, e.g. <c>aes256-gcm@openssh.com</c>.
+    /// </summary>
+    /// <remarks>
+    /// The same fact <see cref="ISshConnection.Cipher"/> is, read the same way — off SSH.NET's
+    /// <c>ConnectionInfo.CurrentServerEncryption</c> once the handshake this session's own connect performed
+    /// has finished — and for the same reason: <c>SftpClient</c> derives from <c>BaseClient</c> exactly as
+    /// <c>SshClient</c> does, and rekeys are no more visible here than they are there. See that member's remark.
+    /// </remarks>
+    string Cipher { get; }
 }
 
 /// <summary>

src/DodoSSH.Client.Ssh/SshConnection.cs

@@ -98,6 +98,25 @@ public interface ISshConnection : IAsyncDisposable
     /// <summary>The host key that was accepted for this connection.</summary>
     HostKeyPresentation HostKey { get; }
 
+    /// <summary>
+    /// The negotiated server-to-client encryption algorithm, e.g. <c>aes256-gcm@openssh.com</c>.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Read once, immediately after the handshake, off SSH.NET's own <c>ConnectionInfo.CurrentServerEncryption</c>.
+    /// The only event that could make this stale is a rekey, and SSH.NET raises no event for one and exposes no
+    /// way to ask again — there is nothing behind this property to go and re-read. A captured value is therefore
+    /// not a snapshot that might drift; it is the only value there has ever been a moment to observe.
+    /// </para>
+    /// <para>
+    /// <b>Server-to-client, not client-to-server.</b> SSH negotiates the two directions independently and a
+    /// server is free to choose differently for each, so the two can in principle disagree. This is the
+    /// direction the bytes drawn on a terminal pane travelled in, which is the fact a status bar showing what
+    /// the screen is made of should be naming.
+    /// </para>
+    /// </remarks>
+    string Cipher { get; }
+
     /// <summary>Opens an interactive shell with a pseudo-terminal.</summary>
     Task<ISshShellSession> OpenShellAsync(TerminalSize size, CancellationToken cancellationToken);
 }

src/DodoSSH.Client.Ssh/SshNetConnectionFactory.cs

@@ -274,6 +274,16 @@ internal sealed class SshNetConnection(SshClient client, HostKeyPresentation hos
     /// <inheritdoc />
     public HostKeyPresentation HostKey { get; } = hostKey;
 
+    /// <inheritdoc />
+    /// <remarks>
+    /// Read at construction rather than lazily: by the time an <see cref="SshNetConnection"/> exists,
+    /// <see cref="SshNetConnectionFactory.ConnectAsync"/> has already awaited <c>client.ConnectAsync</c>, so
+    /// <c>ConnectionInfo</c> is already populated and there is no earlier moment reading it would race. SSH.NET
+    /// types the property as a non-nullable <c>string</c>, so this reads straight through rather than coalescing
+    /// a null that the library's own contract says cannot occur.
+    /// </remarks>
+    public string Cipher { get; } = client.ConnectionInfo.CurrentServerEncryption;
+
     /// <inheritdoc />
     public Task<ISshShellSession> OpenShellAsync(TerminalSize size, CancellationToken cancellationToken)
     {

src/DodoSSH.Client.Ssh/SshNetSftpSession.cs

@@ -20,6 +20,14 @@ internal sealed class SshNetSftpSession(SftpClient client, HostKeyPresentation h
     /// <inheritdoc />
     public HostKeyPresentation HostKey { get; } = hostKey;
 
+    /// <inheritdoc />
+    /// <remarks>
+    /// Read at construction, the same way and for the same reason as <c>SshNetConnection.Cipher</c>: this type
+    /// is only ever built after <c>SshNetConnectionFactory.OpenSftpAsync</c> has awaited <c>client.ConnectAsync</c>,
+    /// so <c>ConnectionInfo</c> is already populated by the time there is a session to read it from.
+    /// </remarks>
+    public string Cipher { get; } = client.ConnectionInfo.CurrentServerEncryption;
+
     /// <inheritdoc />
     public string HomeDirectory { get; } = homeDirectory;
 

src/DodoSSH.Client.Terminal/TerminalWorkspace.cs

@@ -37,6 +37,18 @@ public sealed class TerminalSessionEndedEventArgs(uint sessionId) : EventArgs
     public uint SessionId { get; } = sessionId;
 }
 
+/// <summary>
+/// The negotiated cipher and host-key algorithm for one live session.
+/// </summary>
+/// <param name="Cipher">The server-to-client encryption algorithm; see <see cref="ISshConnection.Cipher"/>.</param>
+/// <param name="HostKeyAlgorithm">The host key's algorithm, e.g. <c>ssh-ed25519</c>.</param>
+/// <remarks>
+/// Two facts rather than the whole <see cref="ISshConnection"/>, because that is all a caller outside this
+/// assembly has any business reading off a session it does not own — everything else on the connection
+/// (disposal, the shell) belongs to the workspace alone. See <see cref="TerminalWorkspace.GetSessionFacts"/>.
+/// </remarks>
+public sealed record SessionFacts(string Cipher, string HostKeyAlgorithm);
+
 /// <summary>The renderer asking for a different font size.</summary>
 /// <param name="step">
 /// How far to move, in points of font size, or zero to go back to the default. It is a step rather than a
@@ -180,6 +192,37 @@ public sealed class TerminalWorkspace : IAsyncDisposable
         }
     }
 
+    /// <summary>
+    /// The negotiated cipher and host-key algorithm for one live session, or null when the id names no
+    /// session this workspace still has open.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Additive, and deliberately narrow: the caller this exists for — the shell's own connect path, which
+    /// wants these two facts for its status bar — has no other business with a session it does not own, and a
+    /// method that handed back the <see cref="ISshConnection"/> itself would have handed over the shell,
+    /// disposal and all, to code that already goes through <see cref="CloseSessionAsync"/> for that.
+    /// </para>
+    /// <para>
+    /// "No session this workspace still has open" covers two different absences the same way
+    /// <see cref="IsSessionLive"/> already does: an id this workspace never issued, and one whose shell has
+    /// already ended but whose entry has not been removed yet. Both are "nothing to report" to a caller
+    /// asking what a session's transport looks like right now.
+    /// </para>
+    /// </remarks>
+    public SessionFacts? GetSessionFacts(uint sessionId)
+    {
+        lock (sessionGate)
+        {
+            if (!sessions.TryGetValue(sessionId, out var session) || session.Run.IsCompleted)
+            {
+                return null;
+            }
+
+            return new SessionFacts(session.Connection.Cipher, session.Connection.HostKey.Algorithm);
+        }
+    }
+
     /// <summary>
     /// Raised with the session id when a shell ends on its own.
     /// </summary>

tests/DodoSSH.Client.App.Tests/FakeSsh.cs

@@ -83,6 +83,9 @@ internal sealed class FakeSftpSession(SshConnectionRequest request) : ISftpSessi
     public HostKeyPresentation HostKey { get; } =
         new(request.Host, request.Port, "ssh-ed25519", "SHA256:fake");
 
+    /// <inheritdoc />
+    public string Cipher { get; } = "aes256-gcm@openssh.com";
+
     /// <inheritdoc />
     public string HomeDirectory => $"/home/{request.Username}";
 
@@ -139,6 +142,9 @@ internal sealed class FakeSshConnection(SshConnectionRequest request) : ISshConn
     public HostKeyPresentation HostKey { get; } =
         new(request.Host, request.Port, "ssh-ed25519", "SHA256:fake");
 
+    /// <inheritdoc />
+    public string Cipher { get; } = "aes256-gcm@openssh.com";
+
     /// <inheritdoc />
     public Task<ISshShellSession> OpenShellAsync(
         TerminalSize size,

tests/DodoSSH.Client.Ssh.Tests/KeyAuthenticationTests.cs

@@ -36,6 +36,12 @@ public sealed class KeyAuthenticationTests(SshServerFixture fixture)
 
         connection.IsConnected.ShouldBeTrue();
 
+        // The one place this suite checks Cipher against a real handshake rather than a fake's fixed string.
+        // SSH.NET negotiates whatever the container's sshd offers first from its own preference list, so the
+        // exact algorithm is not pinned here — only that ConnectionInfo.CurrentServerEncryption came back as
+        // something rather than the empty string a stalled or pre-handshake read would produce.
+        connection.Cipher.ShouldNotBeNullOrEmpty();
+
         // Authenticated is not the same as usable: a channel has to open on the connection too.
         await using var shell = await connection.OpenShellAsync(TerminalSize.Default, Token);
 

tests/DodoSSH.Client.Terminal.Tests/FakeShellSession.cs

@@ -136,6 +136,9 @@ internal sealed class FakeConnection(SshConnectionRequest request, long bytesPer
     public HostKeyPresentation HostKey { get; } =
         new(request.Host, request.Port, "ssh-ed25519", "SHA256:fake");
 
+    /// <inheritdoc />
+    public string Cipher { get; } = "aes256-gcm@openssh.com";
+
     /// <summary>The shell this connection opened, if it opened one.</summary>
     internal FakeShellSession? Shell { get; private set; }
 

tests/DodoSSH.Client.Terminal.Tests/TerminalWorkspaceTests.cs

@@ -149,6 +149,31 @@ public sealed class TerminalWorkspaceTests
         workspace.IsSessionLive(second).ShouldBeTrue("closing one tab must not disturb another");
     }
 
+    /// <remarks>
+    /// The shell's connect path reads these back once, right after <see cref="TerminalWorkspace.OpenSessionAsync"/>
+    /// returns, to fill in the status bar's cipher and host-key facts — see <c>VaultViewModel.ConnectAndAnnounceAsync</c>.
+    /// Asserted the same way <see cref="LivenessIsAnsweredPerSession"/> asserts liveness: per session, and
+    /// null rather than thrown for an id this workspace never issued.
+    /// </remarks>
+    [Fact]
+    public async Task SessionFactsAreReadPerSession()
+    {
+        var connections = new FakeConnectionFactory();
+
+        await using var workspace = CreateWorkspace(connections);
+
+        var sessionId = await workspace.OpenSessionAsync(
+            Request(), TerminalSize.Default, TestContext.Current.CancellationToken);
+
+        var facts = workspace.GetSessionFacts(sessionId).ShouldNotBeNull();
+        var connection = connections.Connections.ShouldHaveSingleItem();
+
+        facts.Cipher.ShouldBe(connection.Cipher);
+        facts.HostKeyAlgorithm.ShouldBe(connection.HostKey.Algorithm);
+
+        workspace.GetSessionFacts(9999).ShouldBeNull("this workspace never issued that id");
+    }
+
     /// <remarks>
     /// <para>
     /// Inserting a snippet has to be able to say whether it arrived, and the transport cannot: it drops

tests/DodoSSH.Client.Transfer.Tests/FakeSftpSession.cs

@@ -23,6 +23,9 @@ internal sealed class FakeSftpSession : ISftpSession
     /// <inheritdoc />
     public HostKeyPresentation HostKey { get; } = new("host.internal", 22, "ssh-ed25519", "SHA256:fake");
 
+    /// <inheritdoc />
+    public string Cipher { get; } = "aes256-gcm@openssh.com";
+
     /// <inheritdoc />
     public string HomeDirectory => "/home/dodo";