Add per-profile "Lock to exact peer addresses" setting (#17, held for next release)

Feature request from the same singer: a way to pin a profile to exact peer addresses
so RemSound never matches the other computer by its advertised name and never switches
to a different address it discovers — for a machine reachable at two addresses at once
(VPN + LAN), they want only the one they chose, and would rather the connection die than
wander. The logical end of the v4.7/v4.8 direction.

New per-profile Profile.LockPeerAddresses (default false), round-tripped through
RemSoundSettingsStore (ApplyProfile/CopyTo + Load/SaveLockPeerAddresses), mirroring the
PriorityMode pattern. New AccessibleCheckBox on the Connectivity tab ("Lock to these exact
peer addresses, no matter what — never follow names or switch", Alt+L), saved with the
profile, marks the profile dirty on change. When set, RefreshKnownPeers early-returns
before the discovered-peer merge and the address-follow, so the profile's peers stay
exactly as set (the allow-list is still pushed). Off = unchanged behaviour.

Manual: rewrote the "Connecting to one specific IP" section (which over-promised that
add-by-IP "can never drift" — the merge/follow could) into an unambiguous "Locking a
profile to one exact address" section, plus a Connectivity-tab control-table row.

Held for the next release.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.App/MainForm.cs

@@ -238,6 +238,14 @@ public sealed class MainForm : Form
     private readonly CheckedListBox rememberedPeersList = new() { CheckOnClick = true, Width = 430, Height = 90, AccessibleName = "Remembered peers (Alt+R)" };
     private readonly Label rememberedPeersStatus = new() { AutoSize = true, Text = "No remembered peer selected." };
     private readonly Button manualAddButton = new() { Text = "Add peer by IP (Alt+&A)", AutoSize = true, AccessibleName = "Add peer by IP" };
+    // Per-profile "pin to exact addresses" toggle (#17). When ticked, RefreshKnownPeers skips the
+    // discovered-peer merge and the address-follow, so the profile's peers stay exactly as the user set.
+    private readonly AccessibleCheckBox lockPeerAddressesBox = new()
+    {
+        Text = "Lock to these exact peer addresses, no matter what — never follow names or switch (Alt+&L)",
+        AccessibleName = "Lock to these exact peer addresses, no matter what; never follow names or switch address",
+        AutoSize = true,
+    };
     // loggingBox + writeLogsNowButton field instances retired 2026-05-08 — both controls
     // now live inside PreferencesDialog. The form-level logFile.Enabled gate is set
     // directly from the settings store at startup (see ApplyLoggingEnabled).
@@ -2797,7 +2805,7 @@ public sealed class MainForm : Form
             Dock = DockStyle.Fill,
             Padding = new Padding(12),
             ColumnCount = 2,
-            RowCount = 5,
+            RowCount = 6,
             AutoScroll = true,
         };
         panel.ColumnStyles.Add(new ColumnStyle(SizeType.AutoSize));
@@ -2921,19 +2929,29 @@ public sealed class MainForm : Form
         // Preferences dialog (File → Preferences, Ctrl+P) as the last two items.
 
         // === Layout ===
-        // 5 rows: 0–2 the three peer lists, 3 manual-add, 4 connection-status readout.
-        panel.RowCount = 5;
+        // 6 rows: 0–2 the three peer lists, 3 manual-add, 4 the lock-to-fixed-addresses toggle, 5 status.
+        panel.RowCount = 6;
         FormLayoutRows.AddCheckedListRow(panel, 0, "Connected peers (Alt+&C)", connectedPeersList, connectedPeersStatus, FocusListControl);
         FormLayoutRows.AddCheckedListRow(panel, 1, "Discovered peers (Alt+&D)", discoveredPeersList, discoveredPeersStatus, FocusListControl);
         FormLayoutRows.AddCheckedListRow(panel, 2, "Remembered peers (Alt+&R)", rememberedPeersList, rememberedPeersStatus, FocusListControl);
         panel.Controls.Add(new Label { Text = "Manual peer", AutoSize = true, Anchor = AnchorStyles.Left }, 0, 3);
         panel.Controls.Add(manualAddButton, 1, 3);
 
+        lockPeerAddressesBox.Checked = settings.LoadLockPeerAddresses();
+        lockPeerAddressesBox.CheckedChanged += (_, _) =>
+        {
+            settings.SaveLockPeerAddresses(lockPeerAddressesBox.Checked);
+            MarkProfileDirty();
+            logFile.Event($"lock peer addresses: {(lockPeerAddressesBox.Checked ? "on" : "off")}");
+        };
+        panel.Controls.Add(lockPeerAddressesBox, 0, 4);
+        panel.SetColumnSpan(lockPeerAddressesBox, 2);
+
         // Connection status readout — last row, tab-into-able.
         var statusLabel = new MnemonicLabel { Text = "Connection status (Alt+&S)", AutoSize = true, Anchor = AnchorStyles.Left, MnemonicTarget = statusReadout };
         statusLabel.Click += (_, _) => statusReadout.Focus();
-        panel.Controls.Add(statusLabel, 0, 4);
-        panel.Controls.Add(statusReadout, 1, 4);
+        panel.Controls.Add(statusLabel, 0, 5);
+        panel.Controls.Add(statusReadout, 1, 5);
 
         // Initial render so the box has content the moment the user tabs into it.
         RefreshStatusReadout();
@@ -5226,6 +5244,16 @@ public sealed class MainForm : Form
         foreach (var peer in discovery.Peers) knownPeers[peer.InstanceId] = peer;
         foreach (var peer in manualPeers.Values) knownPeers[peer.InstanceId] = peer;
 
+        // Locked-to-fixed-addresses profiles (#17): the user wants RemSound to use exactly the peer
+        // addresses they set and never substitute one found on the network. Skip the discovered-peer
+        // merge (which would attach a computer name to their selection) and the address-follow below;
+        // the selection's allow-list is still pushed so audio flows to those exact addresses, unchanged.
+        if (settings.LoadLockPeerAddresses())
+        {
+            PushAllowedReceiveSenders();
+            return;
+        }
+
         // Dedupe by endpoint (address:port). When a manual peer (typed by IP) and a discovered
         // peer (broadcasting hostname) point to the same machine, drop the manual entry and
         // forward any active selection to the discovered peer so the user doesn't lose it.

src/RemSound.Core/Profile.cs

@@ -177,6 +177,12 @@ public sealed class Profile
     /// list at save time. On load, RemSound auto-connects to any of these that resolve.</summary>
     public List<string> SelectedConnectedPeers { get; set; } = [];
 
+    /// <summary>When true, this profile is LOCKED to the exact peer addresses set above. RemSound uses
+    /// only those addresses, never matches the other computer by the name it advertises on the network,
+    /// and never switches to a different address it discovers — even if the set address stops working
+    /// (the connection simply waits or drops rather than moving). Off by default. (#17)</summary>
+    public bool LockPeerAddresses { get; set; }
+
     // === Hotkeys ===
     public HotkeyRecord? ReceiveMuteHotkey { get; set; }
     public HotkeyRecord? SendMuteHotkey { get; set; }

src/RemSound.Core/RemSoundSettingsStore.cs

@@ -282,6 +282,19 @@ public sealed class RemSoundSettingsStore
         Save(s);
     }
 
+    /// <summary>When true, this profile is locked to the exact peer addresses the user set — RemSound
+    /// uses only those, never follows the other computer by its advertised name and never switches to a
+    /// discovered address. Off by default; opt in per profile. (#17)</summary>
+    public bool LoadLockPeerAddresses(bool defaultValue = false) =>
+        Try(() => Load()?.LockPeerAddresses) ?? defaultValue;
+
+    public void SaveLockPeerAddresses(bool value)
+    {
+        var s = Load() ?? new Settings();
+        s.LockPeerAddresses = value;
+        Save(s);
+    }
+
     /// <summary>Suppresses the connect/disconnect sound cues that play when a peer's health
     /// transitions to/from Healthy. Off by default — cues are on. Saved per-profile so users
     /// who don't want them in a given setup don't have to remember to mute every session.
@@ -537,6 +550,7 @@ public sealed class RemSoundSettingsStore
             SendRate = profile.SendRate,
             TightLatencyMode = profile.TightLatencyMode,
             PriorityMode = profile.PriorityMode,
+            LockPeerAddresses = profile.LockPeerAddresses,
             Smoothness = profile.Smoothness,
             ConcealmentArtifact = (ConcealmentArtifact)profile.ConcealmentArtifactRaw,
             MuteConnectionCues = profile.MuteConnectionCues,
@@ -581,6 +595,7 @@ public sealed class RemSoundSettingsStore
         if (s.SendRate is SendRate sr) profile.SendRate = sr;
         if (s.TightLatencyMode is bool tl) profile.TightLatencyMode = tl;
         if (s.PriorityMode is bool pm) profile.PriorityMode = pm;
+        if (s.LockPeerAddresses is bool lpa) profile.LockPeerAddresses = lpa;
         if (s.Smoothness is int sm) profile.Smoothness = sm;
         if (s.ConcealmentArtifact is ConcealmentArtifact ca) profile.ConcealmentArtifactRaw = (int)ca;
         if (s.MuteConnectionCues is bool mc) profile.MuteConnectionCues = mc;
@@ -626,6 +641,7 @@ public sealed class RemSoundSettingsStore
         public SendRate? SendRate { get; set; }
         public bool? TightLatencyMode { get; set; }
         public bool? PriorityMode { get; set; }
+        public bool? LockPeerAddresses { get; set; }
         public int? Smoothness { get; set; }
         public ConcealmentArtifact? ConcealmentArtifact { get; set; }
         public bool? MuteConnectionCues { get; set; }