diff --git a/src/AcDream.Core.Net/Messages/InteractRequests.cs b/src/AcDream.Core.Net/Messages/InteractRequests.cs
new file mode 100644
index 0000000..d9cfe7b
--- /dev/null
+++ b/src/AcDream.Core.Net/Messages/InteractRequests.cs
@@ -0,0 +1,76 @@
+using System.Buffers.Binary;
+
+namespace AcDream.Core.Net.Messages;
+
+/// <summary>
+/// Outbound interaction GameActions. Each carries a single uint32
+/// target guid (plus a second guid for <c>UseWithTarget</c>) inside the
+/// standard <c>0xF7B1</c> GameAction envelope.
+///
+/// <para>
+/// Wire layout (r08 §3 rows 0x0035/0x0036):
+/// <code>
+///   u32 0xF7B1
+///   u32 gameActionSequence
+///   u32 subOpcode
+///   u32 targetGuid        // e.g. door, NPC, lifestone, corpse, item
+///   u32 sourceGuid        // only for UseWithTarget (the item you're using)
+/// </code>
+/// </para>
+///
+/// <para>
+/// Server reply is <c>GameEventType.UseDone</c> (0x01C7) carrying a
+/// <c>WeenieError</c>; 0 = success.
+/// </para>
+/// </summary>
+public static class InteractRequests
+{
+    public const uint GameActionEnvelope = 0xF7B1u;
+    public const uint UseOpcode = 0x0036u;
+    public const uint UseWithTargetOpcode = 0x0035u;
+    public const uint TeleToLifestoneOpcode = 0x0063u;
+
+    /// <summary>
+    /// Use an object: click a door, loot a corpse, talk to an NPC,
+    /// activate a lifestone, step onto a portal.
+    /// </summary>
+    public static byte[] BuildUse(uint gameActionSequence, uint targetGuid)
+    {
+        byte[] body = new byte[16];
+        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  UseOpcode);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), targetGuid);
+        return body;
+    }
+
+    /// <summary>
+    /// Use source item on target: e.g. key on locked door, key on
+    /// chest, scroll on yourself, salvage tool on an item.
+    /// </summary>
+    public static byte[] BuildUseWithTarget(
+        uint gameActionSequence, uint sourceGuid, uint targetGuid)
+    {
+        byte[] body = new byte[20];
+        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  UseWithTargetOpcode);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(12), sourceGuid);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(16), targetGuid);
+        return body;
+    }
+
+    /// <summary>
+    /// Teleport to your lifestone. No target guid — just tells the
+    /// server "recall me." Fails if you haven't tied to a lifestone
+    /// (server responds with a WeenieError).
+    /// </summary>
+    public static byte[] BuildTeleToLifestone(uint gameActionSequence)
+    {
+        byte[] body = new byte[12];
+        BinaryPrimitives.WriteUInt32LittleEndian(body,            GameActionEnvelope);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(4),  gameActionSequence);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.AsSpan(8),  TeleToLifestoneOpcode);
+        return body;
+    }
+}
diff --git a/tests/AcDream.Core.Net.Tests/Messages/InteractRequestsTests.cs b/tests/AcDream.Core.Net.Tests/Messages/InteractRequestsTests.cs
new file mode 100644
index 0000000..5e99b5d
--- /dev/null
+++ b/tests/AcDream.Core.Net.Tests/Messages/InteractRequestsTests.cs
@@ -0,0 +1,45 @@
+using System;
+using System.Buffers.Binary;
+using AcDream.Core.Net.Messages;
+using Xunit;
+
+namespace AcDream.Core.Net.Tests.Messages;
+
+public sealed class InteractRequestsTests
+{
+    [Fact]
+    public void BuildUse_WritesOpcode0x0036AndTarget()
+    {
+        byte[] body = InteractRequests.BuildUse(gameActionSequence: 2, targetGuid: 0xDEAD);
+
+        Assert.Equal(16, body.Length);
+        Assert.Equal(InteractRequests.UseOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+        Assert.Equal(0xDEADu,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(12)));
+    }
+
+    [Fact]
+    public void BuildUseWithTarget_WritesBothGuids()
+    {
+        byte[] body = InteractRequests.BuildUseWithTarget(
+            gameActionSequence: 3, sourceGuid: 0x1000, targetGuid: 0x2000);
+
+        Assert.Equal(20, body.Length);
+        Assert.Equal(InteractRequests.UseWithTargetOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+        Assert.Equal(0x1000u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(12)));
+        Assert.Equal(0x2000u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(16)));
+    }
+
+    [Fact]
+    public void BuildTeleToLifestone_IsEnvelopeOnly()
+    {
+        byte[] body = InteractRequests.BuildTeleToLifestone(gameActionSequence: 7);
+        Assert.Equal(12, body.Length);
+        Assert.Equal(InteractRequests.TeleToLifestoneOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+    }
+}