Fix LT-22614: FLEx does not restart after a Send/Receive merge

Src/Common/FwUtils/FLExBridgeHelper.cs

@@ -8,7 +8,9 @@
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Security.Cryptography;
 using System.ServiceModel;
+using System.Text;
 using System.Threading;
 using SIL.LCModel;
 using SIL.LCModel.Utils;
@@ -245,7 +247,7 @@ public static bool LaunchFieldworksBridge(string projectFolder, string userName,
 			int fwmodelVersionNumber, string liftModelVersionNumber, string writingSystemId, Action onNonBlockerCommandComplete,
 			out bool changesReceived, out string projectName, Uri projectUri, string name, string credentialsPassword, string repoIdentifier)
 		{
-			_pipeID = string.Format(@"SendReceive{0}{1}", projectFolder, command);
+			_pipeID = GeneratePipeId(projectFolder, command);
 			_flexBridgeTerminated = false;
 			changesReceived = false;
 			var args = "";
@@ -324,6 +326,27 @@ public static bool LaunchFieldworksBridge(string projectFolder, string userName,
 			return true;
 		}
 
+		/// <summary>
+		/// Generates the pipe ID embedded in the WCF endpoint names shared with FLEx Bridge, which
+		/// receives it via '-pipeID' and uses it verbatim. The project path is digested rather than
+		/// used directly (LT-22614): WCF hashes long pipe URIs with an algorithm that differs between
+		/// FieldWorks (net48, SHA256) and FLEx Bridge (net462, SHA1), so long paths silently broke all
+		/// bridge signalling; a short ID is always used literally on both sides. Must stay
+		/// deterministic per (projectFolder, command) so duplicate launches collide.
+		/// </summary>
+		private static string GeneratePipeId(string projectFolder, string command)
+		{
+			using (var sha = SHA256.Create())
+			{
+				// SHA256.Create() is stable across processes and FIPS-safe (unlike GetHashCode or MD5).
+				var digest = sha.ComputeHash(Encoding.UTF8.GetBytes(projectFolder ?? string.Empty));
+				// First 8 bytes as hex: unique enough, and URI-safe where Base64 is not.
+				// (On .NET 5+ this would be Convert.ToHexString(digest.AsSpan(0, 8)).)
+				var token = BitConverter.ToString(digest, 0, 8).Replace("-", string.Empty);
+				return "SendReceive" + token + command;
+			}
+		}
+
 		private static void LaunchFlexBridge(IIPCHost host, string command, string args, Action onNonBlockerCommandComplete,
 			string userPass, ref bool changesReceived, ref string projectName)
 		{