Faucet: switch to Gateway gRPC ExecutionService + add API key

csharp/src/StationAPI/Configuration/StationConfig.cs

@@ -62,7 +62,6 @@ public class SolverConfig
     public string? LogoUrl { get; set; }
     public string GrpcEndpoint { get; set; } = null!;
     public string? WebhookSecret { get; set; }
-    public string? AdminApiUrl { get; set; }
 
     /// <summary>
     /// Bearer token for the solver's Gateway gRPC API. Format: <c>tsk_test_*</c> or

csharp/src/StationAPI/Program.cs

@@ -78,10 +78,6 @@
 builder.Services.AddMemoryCache();
 builder.Services.AddSingleton<IFaucetRateLimiter, MemoryCacheFaucetRateLimiter>();
 builder.Services.AddTransient<IFaucetService, FaucetService>();
-builder.Services.AddHttpClient("solver-admin", client =>
-{
-    client.Timeout = TimeSpan.FromSeconds(15);
-});
 
 // Binance price feed HttpClient
 builder.Services.AddHttpClient("binance", client =>

csharp/src/StationAPI/Services/FaucetService.cs

@@ -1,6 +1,6 @@
-using System.Net.Http.Json;
 using System.Numerics;
-using System.Text.Json;
+using Grpc.Core;
+using Train.Solver.Proto;
 using Train.Solver.StationAPI.Configuration;
 using Train.Solver.StationAPI.Helpers;
 
@@ -11,16 +11,16 @@ public class FaucetService : IFaucetService
     private const string EvmNativeAddress = "0x0000000000000000000000000000000000000000";
 
     private readonly IStationConfigProvider _configProvider;
-    private readonly IHttpClientFactory _httpClientFactory;
+    private readonly ISolverClientFactory _clientFactory;
     private readonly ILogger<FaucetService> _logger;
 
     public FaucetService(
         IStationConfigProvider configProvider,
-        IHttpClientFactory httpClientFactory,
+        ISolverClientFactory clientFactory,
         ILogger<FaucetService> logger)
     {
         _configProvider = configProvider;
-        _httpClientFactory = httpClientFactory;
+        _clientFactory = clientFactory;
         _logger = logger;
     }
 
@@ -36,10 +36,10 @@ public FaucetService(
 
     public async Task<FaucetClaimResult> ClaimAsync(FaucetItemConfig item, string recipientAddress, CancellationToken ct)
     {
-        var solver = _configProvider.Current.Solvers.FirstOrDefault(s => !string.IsNullOrEmpty(s.AdminApiUrl));
-        if (solver is null || string.IsNullOrEmpty(solver.AdminApiUrl))
+        var solver = _configProvider.Current.Solvers.FirstOrDefault();
+        if (solver is null)
         {
-            return new FaucetClaimResult(false, null, "No solver with admin API configured");
+            return new FaucetClaimResult(false, null, "No solver configured");
         }
 
         if (!BigInteger.TryParse(item.Amount, out var amount) || amount.Sign <= 0)
@@ -57,46 +57,44 @@ public async Task<FaucetClaimResult> ClaimAsync(FaucetItemConfig item, string re
             return new FaucetClaimResult(false, null, ex.Message);
         }
 
+        var client = _clientFactory.GetExecutionClient(solver.Id);
+        if (client is null)
+        {
+            return new FaucetClaimResult(false, null, "Solver execution client unavailable");
+        }
+
         var correlationId = $"faucet-{Guid.NewGuid()}";
         var networkIdentifier = item.SolverNetworkIdentifier ?? item.Caip2Id;
 
-        var payload = new
+        var request = new SubmitExecutionRequest
         {
-            networkSlug = networkIdentifier,
-            walletAddress = item.MinterAddress,
-            toAddress = item.TokenContract,
-            callData,
-            amount = "0",
-            tokenContract = EvmNativeAddress,
-            correlationId
+            NetworkSlug = networkIdentifier,
+            WalletAddress = item.MinterAddress,
+            ToAddress = item.TokenContract,
+            CallData = callData,
+            Amount = "0",
+            TokenContract = EvmNativeAddress,
+            CorrelationId = correlationId,
         };
 
-        var http = _httpClientFactory.CreateClient("solver-admin");
-        var url = solver.AdminApiUrl.TrimEnd('/') + "/api/custom-transaction";
-
         try
         {
-            using var response = await http.PostAsJsonAsync(url, payload, ct);
-            if (!response.IsSuccessStatusCode)
-            {
-                var body = await response.Content.ReadAsStringAsync(ct);
-                _logger.LogWarning("Faucet claim rejected by solver: {Status} {Body}", (int)response.StatusCode, body);
-                return new FaucetClaimResult(false, null, $"Solver responded {(int)response.StatusCode}");
-            }
-
-            using var stream = await response.Content.ReadAsStreamAsync(ct);
-            using var doc = await JsonDocument.ParseAsync(stream, cancellationToken: ct);
-            if (doc.RootElement.TryGetProperty("accepted", out var accepted) && accepted.ValueKind == JsonValueKind.False)
+            var response = await client.SubmitTransactionAsync(request, cancellationToken: ct);
+            if (!response.Accepted)
             {
-                return new FaucetClaimResult(false, null, "Solver did not accept the transaction");
+                var error = string.IsNullOrEmpty(response.ErrorMessage)
+                    ? "Solver did not accept the transaction"
+                    : response.ErrorMessage;
+                _logger.LogWarning("Faucet claim rejected by solver: {Error}", error);
+                return new FaucetClaimResult(false, null, error);
             }
 
-            return new FaucetClaimResult(true, correlationId, null);
+            return new FaucetClaimResult(true, response.CorrelationId, null);
         }
-        catch (HttpRequestException ex)
+        catch (RpcException ex)
         {
-            _logger.LogError(ex, "Failed to call solver admin API for faucet claim");
-            return new FaucetClaimResult(false, null, "Failed to reach solver");
+            _logger.LogError(ex, "Faucet claim gRPC call failed");
+            return new FaucetClaimResult(false, null, ex.Status.Detail ?? "Failed to reach solver");
         }
     }
 }

csharp/src/StationAPI/Services/SolverClientFactory.cs

@@ -1,4 +1,5 @@
 using System.Collections.Concurrent;
+using Grpc.Core;
 using Grpc.Core.Interceptors;
 using Grpc.Net.Client;
 using Grpc.Net.Client.Web;
@@ -10,6 +11,7 @@ namespace Train.Solver.StationAPI.Services;
 public interface ISolverClientFactory
 {
     SolverService.SolverServiceClient? GetClient(string solverId);
+    ExecutionService.ExecutionServiceClient? GetExecutionClient(string solverId);
 }
 
 public class SolverClientFactory : ISolverClientFactory, IDisposable
@@ -23,6 +25,18 @@ public SolverClientFactory(IStationConfigProvider configProvider)
     }
 
     public SolverService.SolverServiceClient? GetClient(string solverId)
+    {
+        var invoker = GetInvoker(solverId);
+        return invoker is null ? null : new SolverService.SolverServiceClient(invoker);
+    }
+
+    public ExecutionService.ExecutionServiceClient? GetExecutionClient(string solverId)
+    {
+        var invoker = GetInvoker(solverId);
+        return invoker is null ? null : new ExecutionService.ExecutionServiceClient(invoker);
+    }
+
+    private CallInvoker? GetInvoker(string solverId)
     {
         var solver = _configProvider.Current.Solvers.FirstOrDefault(s => s.Id == solverId);
         if (solver is null) return null;
@@ -35,11 +49,9 @@ public SolverClientFactory(IStationConfigProvider configProvider)
 
         // Channels are cached per endpoint, but the API key is per solver — wrap the
         // invoker so each client carries its own auth header. CallInvoker is cheap.
-        var invoker = string.IsNullOrEmpty(solver.ApiKey)
+        return string.IsNullOrEmpty(solver.ApiKey)
             ? channel.CreateCallInvoker()
             : channel.Intercept(new ApiKeyClientInterceptor(solver.ApiKey));
-
-        return new SolverService.SolverServiceClient(invoker);
     }
 
     public void Dispose()

csharp/src/StationAPI/station-config.json

@@ -234,8 +234,7 @@
       "logoUrl": "https://raw.githubusercontent.com/TrainProtocol/.github/main/assets/logo.png",
       "grpcEndpoint": "https://train-solver-api.lb.layerswap.io",
       "webhookSecret": "station-webhook-secret-1",
-      "adminApiUrl": "https://train-solver-admin.lb.layerswap.io",
-      "apiKey": null
+      "apiKey": "tsk_test_jw9ku1zA2ETneTV-_Rm7BveBLOR_8fGXNkKR6bxbUBM"
     }
   ],
   "faucet": {