From ab714a24ce15863d442f698625f6629d07c86b5a Mon Sep 17 00:00:00 2001
From: EugeneTes <meelstorm@gmail.com>
Date: Thu, 8 Oct 2026 14:09:18 +0000
Subject: [PATCH] refactor(a2a-client): no runtime-internal native calls for
 attachments

---
 .../A2ATool.cs                                | 27 ++-----------------
 .../A2A/A2AToolTests.cs                       | 15 -----------
 2 files changed, 2 insertions(+), 40 deletions(-)

diff --git a/extensions/Volcanic.AgenticCore.Extensions.A2A/A2ATool.cs b/extensions/Volcanic.AgenticCore.Extensions.A2A/A2ATool.cs
index c08eada..e7c9e63 100644
--- a/extensions/Volcanic.AgenticCore.Extensions.A2A/A2ATool.cs
+++ b/extensions/Volcanic.AgenticCore.Extensions.A2A/A2ATool.cs
@@ -285,7 +285,7 @@ internal sealed class A2ATool(A2AClientSettings settings, string target, A2AWatc
     }
 
     /// <summary>
-    /// Reads the attachments: regular workspace files (symlinks resolved and confined), together at most
+    /// Reads the attachments: workspace files (symlinks resolved and confined), together at most
     /// <see cref="A2AClientSettings.MaxFileBytes"/>, each read through one opened stream so a file growing meanwhile is
     /// still capped.
     /// </summary>
@@ -297,7 +297,7 @@ internal sealed class A2ATool(A2AClientSettings settings, string target, A2AWatc
         {
             var full = ConfinedPath(workspace, path);
             if (Directory.Exists(full) || !File.Exists(full)) throw new ArgumentException($"{path} does not exist or is not a file.");
-            if (!IsRegularFile(full)) throw new ArgumentException($"{path} is not a regular file.");
+            // Special files (FIFOs, devices) aren't detected: a FIFO would block here until the run is aborted.
             byte[] bytes;
             await using (var stream = new FileStream(full, new FileStreamOptions
                          { Mode = FileMode.Open, Access = FileAccess.Read, Share = FileShare.Read, Options = FileOptions.Asynchronous }))
@@ -321,29 +321,6 @@ internal sealed class A2ATool(A2AClientSettings settings, string target, A2AWatc
         return parts;
     }
 
-    /// <summary>
-    /// False for FIFOs, sockets and devices, which could block or never end. Unix: the runtime's own stat (the managed
-    /// API reports every non-directory as a file); elsewhere every existing file counts as regular.
-    /// </summary>
-    private static bool IsRegularFile(string path)
-    {
-        if (OperatingSystem.IsWindows()) return true;
-        try
-        {
-            var status = new byte[512]; // FileStatus is ~120 bytes; Mode is the second int32
-            if (SystemNativeStat(path, status) != 0) return false;
-            const int typeMask = 0xF000, regular = 0x8000;
-            return (BitConverter.ToInt32(status, 4) & typeMask) == regular;
-        }
-        catch (Exception ex) when (ex is DllNotFoundException or EntryPointNotFoundException)
-        {
-            return true;
-        }
-    }
-
-    [System.Runtime.InteropServices.DllImport("libSystem.Native", EntryPoint = "SystemNative_Stat")]
-    private static extern int SystemNativeStat([System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPUTF8Str)] string path, byte[] status);
-
     /// <summary>The real path of a workspace file: inside the workspace lexically and after every symlink is resolved.</summary>
     internal static string ConfinedPath(string workspace, string path)
     {
diff --git a/tests/Volcanic.AgenticCore.Extensions.Tests/A2A/A2AToolTests.cs b/tests/Volcanic.AgenticCore.Extensions.Tests/A2A/A2AToolTests.cs
index e73533c..5bdafcd 100644
--- a/tests/Volcanic.AgenticCore.Extensions.Tests/A2A/A2AToolTests.cs
+++ b/tests/Volcanic.AgenticCore.Extensions.Tests/A2A/A2AToolTests.cs
@@ -315,21 +315,6 @@ public class A2AToolTests
         Assert.Empty(remote.Faux.Requests);
     }
 
-    [Fact]
-    public async Task Send_Fifo_Rejected()
-    {
-        if (OperatingSystem.IsWindows()) return;
-        await using var remote = await RemoteAgentServer.StartAsync();
-        await using var host = new A2AClientHost(remote);
-        using (var mkfifo = System.Diagnostics.Process.Start("mkfifo", Path.Combine(host.Workspace, "pipe")))
-            await mkfifo.WaitForExitAsync();
-        var session = await host.CreateSessionAsync();
-        var (text, isError) = await host.CallToolAsync(session, new { action = "send", agent = "remote", message = "x", files = new[] { "pipe" } });
-        Assert.True(isError);
-        Assert.Contains("not a regular file", text);
-        Assert.Empty(remote.Faux.Requests);
-    }
-
     [Fact]
     public async Task Cancel_RemoteDown_KeepsWatching_AndResultStillArrives()
     {