diff --git a/OPTIMA-INTEGRATION-TESTS.md b/OPTIMA-INTEGRATION-TESTS.md
index f90b2ee..5053a4f 100644
--- a/OPTIMA-INTEGRATION-TESTS.md
+++ b/OPTIMA-INTEGRATION-TESTS.md
@@ -45,5 +45,14 @@ Po pomyślnym `--check-config` uruchom usługę z tym samym plikiem konfiguracji
 - błędy dla brakującego kontrahenta, produktu, magazynu, waluty i wymaganej ceny;
 - parametryzowane `sql_raw`, wiele recordsetów, dane binarne oraz błąd SQL;
 - dwa równoczesne wywołania `place_order` — dokumenty mają zostać utworzone kolejno na jednym wątku COM.
+- `extraFields` z dwoma istniejącymi atrybutami dokumentu: wartości mają być widoczne na nagłówku RO; nieznany kod ma zwrócić błąd bez zapisu dokumentu.
+
+Runner może sprawdzić ostatni scenariusz po podaniu dwóch kodów atrybutów tekstowych istniejących w firmie testowej:
+
+```powershell
+dotnet run --project .\tests\SmartB2B.Optima.IntegrationTests -- --config .\src\SmartB2B.Optima.Service\config\optima.json --write-order --customer-id 2 --product-code SMARTB2B_TEST_TWR --attribute-code-1 SOURCE --attribute-value-1 B2B --attribute-code-2 NOTE --attribute-value-2 test
+```
+
+Test odczytuje zapisane wartości z `CDN.DokAtrybuty` i sprawdza, że próba użycia nieznanego kodu nie utworzyła RO.
 
 Przed testami trybu `Approved` wykonaj kopię bezpieczeństwa bazy lub użyj firmy przeznaczonej wyłącznie do testów.
diff --git a/README.md b/README.md
index 421e1df..24ba3f5 100644
--- a/README.md
+++ b/README.md
@@ -110,7 +110,7 @@ Wycofanie polega na uruchomieniu `release-enova/daemon/uninstall.cmd` i ponownym
 
 ## Procedury WAMP
 
-- `eu.smartb2b.place_order` przyjmuje `currency_iso`, `companyErpId`, `warehouseErpId`, `purchase_order_number`, `notes` i `lines[]` z polami `symbol`, `quantity`, opcjonalnymi `price_netto` i `price_brutto` oraz `discount`. Enova wymaga `price_netto`; Optima wybiera cenę zgodnie z `TypNB` definicji dokumentu. Wynik jest zwracany jako kwargs: `order_erp_id`, `order_erp_symbol`, `value_netto`, `value_brutto`, `stocks`.
+- `eu.smartb2b.place_order` przyjmuje `currency_iso`, `companyErpId`, `warehouseErpId`, `purchase_order_number`, `notes` i `lines[]` z polami `symbol`, `quantity`, opcjonalnymi `price_netto` i `price_brutto` oraz `discount`. Dla Optimy opcjonalne `extraFields` jest mapą kodów atrybutów dokumentu (`DefAtrybuty.DeA_Kod`) na wartości tekstowe, np. `{"ŹRÓDŁO":"B2B"}`. Nieznany kod lub wartość odrzucona przez Optimę przerywa zapis zamówienia. Enova wymaga `price_netto`; Optima wybiera cenę zgodnie z `TypNB` definicji dokumentu. Wynik jest zwracany jako kwargs: `order_erp_id`, `order_erp_symbol`, `value_netto`, `value_brutto`, `stocks`.
 - `eu.smartb2b.sql_raw` przyjmuje `query` i opcjonalne `params`; parametry odpowiadają kolejno `@1`, `@2`, itd. Wynik ma pola `recordsets`, `recordset`, `output`, `rowsAffected`.
 - Diagnostyka: `eu.smartb2b.sync.get_version`, `get_info`, `get_log`, `get_error_log`.
 
diff --git a/src/SmartB2B.Optima.Adapter/LateBoundOptimaComFacade.cs b/src/SmartB2B.Optima.Adapter/LateBoundOptimaComFacade.cs
index 97826fc..dedef04 100644
--- a/src/SmartB2B.Optima.Adapter/LateBoundOptimaComFacade.cs
+++ b/src/SmartB2B.Optima.Adapter/LateBoundOptimaComFacade.cs
@@ -151,6 +151,7 @@ internal sealed class LateBoundOptimaComFacade : IOptimaComFacade
             doc.Uwagi = request.Notes?.Trim() ?? string.Empty;
             doc.WalutaSymbol = request.CurrencyIso;
             doc.Export = 0;
+            AddDocumentAttributes(comSession, doc, request.ExtraFields);
             elements = doc.Elementy;
 
             var calculationMode = Convert.ToInt32(doc.TypNB);
@@ -184,7 +185,19 @@ internal sealed class LateBoundOptimaComFacade : IOptimaComFacade
             }
 
             Verbose(verboseLogging, "Optima: zapis dokumentu przez session.Save().");
-            comSession.Save();
+            try
+            {
+                comSession.Save();
+            }
+            catch (Exception exception) when (request.ExtraFields.Count > 0)
+            {
+                var codes = request.ExtraFields.Keys.ToArray();
+                throw new ErpOperationException(
+                    "eu.smartb2b.erp.invalid_document_attribute",
+                    $"Nie udało się zapisać zamówienia z atrybutami dokumentu: {string.Join(", ", codes)}.",
+                    new Dictionary<string, object?> { ["attributeCodes"] = codes },
+                    exception);
+            }
             var net = Convert.ToDecimal(doc.RazemNettoWal);
             var gross = Convert.ToDecimal(doc.RazemBruttoWal);
             return new OrderResult(
@@ -212,6 +225,58 @@ internal sealed class LateBoundOptimaComFacade : IOptimaComFacade
         }
     }
 
+    internal static void AddDocumentAttributes(
+        dynamic session,
+        dynamic document,
+        IReadOnlyDictionary<string, string> extraFields)
+    {
+        if (extraFields.Count == 0) return;
+
+        object? attributes = null;
+        try
+        {
+            attributes = document.Atrybuty;
+            foreach (var (code, value) in extraFields)
+            {
+                object? definition = null;
+                object? attribute = null;
+                try
+                {
+                    definition = FindRequired(
+                        session,
+                        "CDN.DefAtrybuty",
+                        $"DeA_Typ=4 AND DeA_Kod='{EscapeFilter(code)}'",
+                        "eu.smartb2b.erp.document_attribute_not_found",
+                        $"Nie znaleziono atrybutu dokumentu o kodzie '{code}'.");
+                    attribute = ((dynamic)attributes).AddNew();
+                    ((dynamic)attribute).DeAID = Convert.ToInt32(((dynamic)definition).ID);
+                    ((dynamic)attribute).Wartosc = value;
+                }
+                catch (ErpOperationException)
+                {
+                    throw;
+                }
+                catch (Exception exception)
+                {
+                    throw new ErpOperationException(
+                        "eu.smartb2b.erp.invalid_document_attribute",
+                        $"Nie można przypisać wartości atrybutu dokumentu '{code}'.",
+                        new Dictionary<string, object?> { ["attributeCode"] = code },
+                        exception);
+                }
+                finally
+                {
+                    ReleaseComObject(attribute);
+                    ReleaseComObject(definition);
+                }
+            }
+        }
+        finally
+        {
+            ReleaseComObject(attributes);
+        }
+    }
+
     private static object FindRequired(
         dynamic session,
         string collectionName,
diff --git a/src/SmartB2B.Optima.Adapter/OptimaOrderAdapter.cs b/src/SmartB2B.Optima.Adapter/OptimaOrderAdapter.cs
index b9112b5..c8e1050 100644
--- a/src/SmartB2B.Optima.Adapter/OptimaOrderAdapter.cs
+++ b/src/SmartB2B.Optima.Adapter/OptimaOrderAdapter.cs
@@ -41,7 +41,7 @@ public sealed class OptimaOrderAdapter : IErpOrderAdapter
             "Comarch ERP Optima",
             runtime.ErpVersion,
             configuration.Connection.DatabaseName,
-            ["price_netto", "price_brutto", "multi_currency", "Buffer", "Approved", "COM STA"],
+            ["price_netto", "price_brutto", "multi_currency", "extraFields", "Buffer", "Approved", "COM STA"],
             new Dictionary<string, string>
             {
                 ["COM ProgID"] = runtime.ComProgId,
diff --git a/src/SmartB2B.Optima.Adapter/SmartB2B.Optima.Adapter.csproj b/src/SmartB2B.Optima.Adapter/SmartB2B.Optima.Adapter.csproj
index 457bf4d..61cac22 100644
--- a/src/SmartB2B.Optima.Adapter/SmartB2B.Optima.Adapter.csproj
+++ b/src/SmartB2B.Optima.Adapter/SmartB2B.Optima.Adapter.csproj
@@ -7,5 +7,6 @@
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="../SmartB2B.Sync.Contracts/SmartB2B.Sync.Contracts.csproj" />
+    <InternalsVisibleTo Include="SmartB2B.Optima.Tests" />
   </ItemGroup>
 </Project>
diff --git a/src/SmartB2B.Sync.Contracts/SyncContracts.cs b/src/SmartB2B.Sync.Contracts/SyncContracts.cs
index 963c835..de69c66 100644
--- a/src/SmartB2B.Sync.Contracts/SyncContracts.cs
+++ b/src/SmartB2B.Sync.Contracts/SyncContracts.cs
@@ -36,6 +36,8 @@ public sealed class OrderRequest
     public OrderSaveMode SaveMode { get; init; } = OrderSaveMode.Buffer;
 
     public IReadOnlyList<OrderLineRequest> Items { get; init; } = [];
+
+    public IReadOnlyDictionary<string, string> ExtraFields { get; init; } = new Dictionary<string, string>();
 }
 
 public sealed class OrderLineRequest
@@ -126,6 +128,12 @@ public static class OrderValidator
             errors.Add("Definicja dokumentu jest wymagana.");
         }
 
+        foreach (var field in request.ExtraFields)
+        {
+            if (string.IsNullOrWhiteSpace(field.Key)) errors.Add("Kod w extraFields nie może być pusty.");
+            if (field.Value is null) errors.Add($"extraFields['{field.Key}'] musi być tekstem.");
+        }
+
         if (request.Items is null || request.Items.Count == 0)
         {
             errors.Add("Zamówienie musi zawierać co najmniej jedną pozycję.");
diff --git a/src/SmartB2B.Sync.Service/Orders/PlaceOrderHandler.cs b/src/SmartB2B.Sync.Service/Orders/PlaceOrderHandler.cs
index a50401f..669acaf 100644
--- a/src/SmartB2B.Sync.Service/Orders/PlaceOrderHandler.cs
+++ b/src/SmartB2B.Sync.Service/Orders/PlaceOrderHandler.cs
@@ -1,4 +1,5 @@
 using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
 using SmartB2B.Sync.Contracts;
 using SmartB2B.Sync.Service.Diagnostics;
 using SmartB2B.Sync.Service.Rpc;
@@ -34,6 +35,7 @@ public sealed class PlaceOrderHandler
             DocumentDefinition = _configuration.DocumentDefinition,
             WarehouseCode = invocation.Get<string>("warehouseErpId") ?? _configuration.DefaultWarehouseCode,
             SaveMode = _configuration.SaveMode,
+            ExtraFields = ReadExtraFields(invocation),
             Items = inputLines.Select(line => new OrderLineRequest
             {
                 ProductCode = line.Symbol ?? string.Empty,
@@ -93,6 +95,37 @@ public sealed class PlaceOrderHandler
             _orderLock.Release();
         }
     }
+
+    private static IReadOnlyDictionary<string, string> ReadExtraFields(RpcInvocation invocation)
+    {
+        if (!invocation.Contains("extraFields")) return new Dictionary<string, string>();
+
+        JToken? token;
+        try { token = invocation.Get<JToken>("extraFields"); }
+        catch (Exception exception) when (exception is JsonException or ArgumentException or InvalidCastException or FormatException)
+        {
+            throw InvalidExtraFields("extraFields musi być mapą kodów atrybutów na wartości tekstowe.");
+        }
+
+        if (token is not JObject fields)
+            throw InvalidExtraFields("extraFields musi być mapą kodów atrybutów na wartości tekstowe.");
+
+        var result = new Dictionary<string, string>(StringComparer.Ordinal);
+        foreach (var field in fields.Properties())
+        {
+            var code = field.Name.Trim();
+            if (code.Length == 0) throw InvalidExtraFields("Kod w extraFields nie może być pusty.");
+            if (field.Value.Type != JTokenType.String)
+                throw InvalidExtraFields($"extraFields['{code}'] musi być tekstem.");
+            if (!result.TryAdd(code, field.Value.Value<string>()!))
+                throw InvalidExtraFields($"Kod '{code}' występuje w extraFields więcej niż raz.");
+        }
+
+        return result;
+    }
+
+    private static Exception InvalidExtraFields(string message) =>
+        WampErrorFactory.Create("eu.smartb2b.erp.invalid_order_lines", message);
 }
 
 public sealed class PlaceOrderLine
diff --git a/tests/SmartB2B.Optima.IntegrationTests/Program.cs b/tests/SmartB2B.Optima.IntegrationTests/Program.cs
index 5b393e4..b3dd056 100644
--- a/tests/SmartB2B.Optima.IntegrationTests/Program.cs
+++ b/tests/SmartB2B.Optima.IntegrationTests/Program.cs
@@ -11,7 +11,8 @@ if (!options.TryGetValue("config", out var configPath) || string.IsNullOrWhiteSp
 {
     Console.Error.WriteLine(
         "Użycie: --config <optima.json> [--negative-tests] [--write-order [--approved]] " +
-        "[--customer-id <ID> --product-code <KOD>]");
+        "[--customer-id <ID> --product-code <KOD>] " +
+        "[--attribute-code-1 <KOD> --attribute-value-1 <TEKST> --attribute-code-2 <KOD> --attribute-value-2 <TEKST>]");
     return 2;
 }
 
@@ -78,9 +79,28 @@ if (saveMode == OrderSaveMode.Buffer && runtime.AdapterConfiguration.SaveMode !=
 }
 
 var reference = $"SMARTB2B-IT-{DateTime.UtcNow:yyyyMMdd-HHmmss}";
-var request = CreateRequest(runtime.AdapterConfiguration, customerId!, productCode!, "PLN", reference, saveMode);
+var extraFields = ReadTestAttributes(options);
+if (extraFields.Count > 0)
+{
+    var missingReference = reference + "-MISSING";
+    var missingCode = "__SMARTB2B_MISSING_ATTR__";
+    ExpectError(
+        () => adapter.CreateOrder(CreateRequest(
+            runtime.AdapterConfiguration, customerId!, productCode!, "PLN", missingReference,
+            OrderSaveMode.Buffer, new Dictionary<string, string> { [missingCode] = "test" })),
+        "eu.smartb2b.erp.document_attribute_not_found");
+    await AssertNoOrderWithReferenceAsync(sql, missingReference);
+    Console.WriteLine("PASS extraFields: nieznany kod nie utworzył zamówienia.");
+}
+
+var request = CreateRequest(runtime.AdapterConfiguration, customerId!, productCode!, "PLN", reference, saveMode, extraFields);
 
 var result = adapter.CreateOrder(request);
+if (extraFields.Count > 0)
+{
+    await AssertSavedAttributesAsync(sql, result.Id, extraFields);
+    Console.WriteLine("PASS extraFields: dwa atrybuty zapisano na nagłówku zamówienia.");
+}
 Console.WriteLine("PASS place_order:");
 Console.WriteLine(JsonSerializer.Serialize(new
 {
@@ -124,7 +144,8 @@ static OrderRequest CreateRequest(
     string productCode,
     string currency,
     string reference,
-    OrderSaveMode saveMode = OrderSaveMode.Buffer) => new()
+    OrderSaveMode saveMode = OrderSaveMode.Buffer,
+    IReadOnlyDictionary<string, string>? extraFields = null) => new()
 {
     CurrencyIso = currency,
     CustomerCode = customerId,
@@ -133,6 +154,7 @@ static OrderRequest CreateRequest(
     DocumentDefinition = configuration.DocumentDefinition,
     WarehouseCode = configuration.DefaultWarehouseCode,
     SaveMode = saveMode,
+    ExtraFields = extraFields ?? new Dictionary<string, string>(),
     Items =
     [
         new OrderLineRequest
@@ -146,6 +168,56 @@ static OrderRequest CreateRequest(
     ]
 };
 
+static IReadOnlyDictionary<string, string> ReadTestAttributes(Dictionary<string, string?> options)
+{
+    var names = new[] { "attribute-code-1", "attribute-value-1", "attribute-code-2", "attribute-value-2" };
+    if (!names.Any(options.ContainsKey)) return new Dictionary<string, string>();
+    if (names.Any(name => !options.ContainsKey(name)))
+        throw new ArgumentException("Test extraFields wymaga dwóch kodów i dwóch wartości atrybutów tekstowych.");
+
+    var first = options["attribute-code-1"]?.Trim();
+    var second = options["attribute-code-2"]?.Trim();
+    if (string.IsNullOrWhiteSpace(first) || string.IsNullOrWhiteSpace(second) || first == second)
+        throw new ArgumentException("Kody dwóch atrybutów muszą być różne i niepuste.");
+    return new Dictionary<string, string>
+    {
+        [first] = options["attribute-value-1"] ?? string.Empty,
+        [second] = options["attribute-value-2"] ?? string.Empty
+    };
+}
+
+static async Task AssertNoOrderWithReferenceAsync(SqlRawHandler sql, string reference)
+{
+    var result = (SqlRawResult?)await sql.HandleAsync(
+        new RpcInvocation([], new Dictionary<string, object?>
+        {
+            ["query"] = "SELECT COUNT(*) AS order_count FROM CDN.TraNag WHERE TrN_NumerObcy=@1",
+            ["params"] = new object?[] { reference }
+        }), CancellationToken.None);
+    if (Convert.ToInt32(result?.Recordsets[0][0]["order_count"]) != 0)
+        throw new InvalidOperationException("Nieznany atrybut pozostawił zapisane zamówienie.");
+}
+
+static async Task AssertSavedAttributesAsync(
+    SqlRawHandler sql, int orderId, IReadOnlyDictionary<string, string> expected)
+{
+    var result = (SqlRawResult?)await sql.HandleAsync(
+        new RpcInvocation([], new Dictionary<string, object?>
+        {
+            ["query"] = "SELECT DeA_Kod, DAt_WartoscTxt FROM CDN.DokAtrybuty JOIN CDN.DefAtrybuty ON DAt_DeAId=DeA_DeAId WHERE DAt_TrNId=@1",
+            ["params"] = new object?[] { orderId }
+        }), CancellationToken.None);
+    var actual = result?.Recordsets[0].ToDictionary(
+        row => Convert.ToString(row["DeA_Kod"])!,
+        row => Convert.ToString(row["DAt_WartoscTxt"]) ?? string.Empty,
+        StringComparer.Ordinal);
+    foreach (var (code, value) in expected)
+    {
+        if (actual is null || !actual.TryGetValue(code, out var saved) || saved != value)
+            throw new InvalidOperationException($"Atrybut '{code}' nie ma oczekiwanej wartości na dokumencie {orderId}.");
+    }
+}
+
 static void ExpectError(Action action, string expectedUri)
 {
     try
diff --git a/tests/SmartB2B.Optima.Tests/Program.cs b/tests/SmartB2B.Optima.Tests/Program.cs
index d1130ca..0c04fa3 100644
--- a/tests/SmartB2B.Optima.Tests/Program.cs
+++ b/tests/SmartB2B.Optima.Tests/Program.cs
@@ -3,6 +3,7 @@ using SmartB2B.Optima.Adapter;
 using SmartB2B.Sync.Contracts;
 using SmartB2B.Sync.Service.Orders;
 using SmartB2B.Sync.Service.Rpc;
+using WampSharp.V2.Core.Contracts;
 
 var tests = new (string Name, Func<Task> Run)[]
 {
@@ -14,6 +15,11 @@ var tests = new (string Name, Func<Task> Run)[]
     ("Tryb brutto wybiera price_brutto", GrossDocumentSelectsGrossPrice),
     ("Brak ceny wymaganej przez definicję jest stabilnym błędem", RequiredPriceIsEnforced),
     ("Handler przekazuje pełny kontrakt do Optimy", HandlerMapsOptimaContract),
+    ("Handler przyjmuje i pomija opcjonalne extraFields", HandlerMapsOptionalExtraFields),
+    ("Handler odrzuca błędne extraFields", HandlerRejectsInvalidExtraFields),
+    ("Fasada przypisuje atrybuty nagłówka przed zapisem", FacadeAddsDocumentAttributes),
+    ("Fasada odrzuca nieznany kod atrybutu", FacadeRejectsMissingAttribute),
+    ("Fasada zgłasza odrzuconą wartość atrybutu", FacadeRejectsAttributeValue),
     ("Wynik Optimy zachowuje kwargs WAMP", HandlerReturnsKeywordResult),
     ("Operacje zamówień są serializowane", ConcurrentOrdersAreSerialized),
     ("Fasada COM działa na jednym wątku STA", FacadeRunsOnSingleStaThread),
@@ -102,6 +108,105 @@ static async Task HandlerMapsOptimaContract()
     AssertEqual(123m, request.Items[0].UnitPriceGross, "brutto");
 }
 
+static async Task HandlerMapsOptionalExtraFields()
+{
+    using var adapter = new CapturingAdapter();
+    var handler = new PlaceOrderHandler(adapter, CreateConfiguration());
+    await handler.HandleAsync(CreateInvocation(new Dictionary<string, object?>
+    {
+        ["SOURCE"] = "B2B",
+        ["NOTE"] = ""
+    }), CancellationToken.None);
+    AssertEqual("B2B", adapter.LastRequest?.ExtraFields["SOURCE"], "wartość SOURCE");
+    AssertEqual("", adapter.LastRequest?.ExtraFields["NOTE"], "pusta wartość");
+
+    await handler.HandleAsync(CreateInvocation(), CancellationToken.None);
+    AssertEqual(0, adapter.LastRequest?.ExtraFields.Count, "brak extraFields");
+    await handler.HandleAsync(CreateInvocation(new Dictionary<string, string>()), CancellationToken.None);
+    AssertEqual(0, adapter.LastRequest?.ExtraFields.Count, "puste extraFields");
+}
+
+static async Task HandlerRejectsInvalidExtraFields()
+{
+    foreach (var invalid in new object?[]
+    {
+        null,
+        "text",
+        new[] { "SOURCE" },
+        new Dictionary<string, object?> { ["SOURCE"] = 123 },
+        new Dictionary<string, object?> { [" "] = "value" },
+        new Dictionary<string, object?> { ["SOURCE"] = "one", [" SOURCE "] = "two" }
+    })
+    {
+        using var adapter = new CapturingAdapter();
+        var handler = new PlaceOrderHandler(adapter, CreateConfiguration());
+        try
+        {
+            await handler.HandleAsync(CreateInvocation(invalid, includeExtraFields: true), CancellationToken.None);
+            throw new InvalidOperationException("Oczekiwano odrzucenia extraFields.");
+        }
+        catch (WampException exception) when (exception.ErrorUri == "eu.smartb2b.erp.invalid_order_lines")
+        {
+            AssertEqual(null, adapter.LastRequest, "brak zapisu zamówienia");
+        }
+    }
+}
+
+static Task FacadeAddsDocumentAttributes()
+{
+    var session = new FakeAttributeSession(new Dictionary<string, int> { ["SOURCE"] = 7, ["NOTE"] = 8 });
+    var document = new FakeAttributeDocument();
+    LateBoundOptimaComFacade.AddDocumentAttributes(session, document, new Dictionary<string, string>
+    {
+        ["SOURCE"] = "B2B",
+        ["NOTE"] = ""
+    });
+    AssertEqual(2, document.Atrybuty.Items.Count, "liczba atrybutów");
+    AssertEqual(7, document.Atrybuty.Items[0].DeAID, "ID SOURCE");
+    AssertEqual("B2B", document.Atrybuty.Items[0].Wartosc, "wartość SOURCE");
+    AssertEqual(8, document.Atrybuty.Items[1].DeAID, "ID NOTE");
+    AssertEqual("", document.Atrybuty.Items[1].Wartosc, "pusta wartość NOTE");
+    return Task.CompletedTask;
+}
+
+static Task FacadeRejectsMissingAttribute()
+{
+    var session = new FakeAttributeSession(new Dictionary<string, int>());
+    var document = new FakeAttributeDocument();
+    try
+    {
+        LateBoundOptimaComFacade.AddDocumentAttributes(session, document, new Dictionary<string, string>
+        {
+            ["MISSING"] = "value"
+        });
+        throw new InvalidOperationException("Oczekiwano błędu nieznanego kodu.");
+    }
+    catch (ErpOperationException exception) when (exception.ErrorUri == "eu.smartb2b.erp.document_attribute_not_found")
+    {
+        AssertEqual(0, document.Atrybuty.Items.Count, "brak dodanego atrybutu");
+        return Task.CompletedTask;
+    }
+}
+
+static Task FacadeRejectsAttributeValue()
+{
+    var session = new FakeAttributeSession(new Dictionary<string, int> { ["SOURCE"] = 7 });
+    var document = new FakeAttributeDocument();
+    try
+    {
+        LateBoundOptimaComFacade.AddDocumentAttributes(session, document, new Dictionary<string, string>
+        {
+            ["SOURCE"] = "REJECTED"
+        });
+        throw new InvalidOperationException("Oczekiwano błędu wartości atrybutu.");
+    }
+    catch (ErpOperationException exception) when (exception.ErrorUri == "eu.smartb2b.erp.invalid_document_attribute")
+    {
+        AssertEqual("SOURCE", exception.Details["attributeCode"], "kod w błędzie");
+        return Task.CompletedTask;
+    }
+}
+
 static async Task HandlerReturnsKeywordResult()
 {
     using var adapter = new CapturingAdapter();
@@ -135,6 +240,7 @@ static Task FacadeRunsOnSingleStaThread()
     AssertEqual(1, facade.ThreadIds.Distinct().Count(), "liczba wątków COM");
     AssertEqual(ApartmentState.STA, facade.ApartmentStates.Distinct().Single(), "apartment COM");
     AssertEqual("Buffer", info.Details?["Save mode"], "tryb zapisu w diagnostyce");
+    AssertEqual(true, info.Capabilities.Contains("extraFields"), "możliwość extraFields");
     return Task.CompletedTask;
 }
 
@@ -152,9 +258,9 @@ static async Task AdapterSerializesComCalls()
     AssertEqual(1, facade.MaximumConcurrency, "maksymalna równoległość fasady COM");
 }
 
-static RpcInvocation CreateInvocation() => new(
-    [],
-    new Dictionary<string, object?>
+static RpcInvocation CreateInvocation(object? extraFields = null, bool includeExtraFields = false)
+{
+    var arguments = new Dictionary<string, object?>
     {
         ["currency_iso"] = "eur",
         ["companyErpId"] = "123",
@@ -172,7 +278,10 @@ static RpcInvocation CreateInvocation() => new(
                 Discount = 12.5m
             }
         }
-    });
+    };
+    if (includeExtraFields || extraFields is not null) arguments["extraFields"] = extraFields;
+    return new RpcInvocation([], arguments);
+}
 
 static ErpAdapterConfiguration CreateConfiguration() => new(
     new ErpConnectionOptions("Firma demo", "ADMIN", "", "Server=.;Database=demo"),
@@ -317,3 +426,69 @@ file sealed class CapturingComFacade : IOptimaComFacade
         return true;
     });
 }
+
+public sealed class FakeAttributeSession
+{
+    private readonly IReadOnlyDictionary<string, int> _definitions;
+
+    public FakeAttributeSession(IReadOnlyDictionary<string, int> definitions) => _definitions = definitions;
+
+    public FakeDefinitionCollection CreateObject(string name)
+    {
+        if (name != "CDN.DefAtrybuty") throw new InvalidOperationException($"Nieoczekiwana kolekcja: {name}");
+        return new FakeDefinitionCollection(_definitions);
+    }
+}
+
+public sealed class FakeDefinitionCollection
+{
+    private readonly IReadOnlyDictionary<string, int> _definitions;
+
+    public FakeDefinitionCollection(IReadOnlyDictionary<string, int> definitions) => _definitions = definitions;
+
+    public FakeDefinition? Item(string filter)
+    {
+        if (!filter.StartsWith("DeA_Typ=4 AND DeA_Kod='", StringComparison.Ordinal))
+            throw new InvalidOperationException($"Niepoprawny filtr: {filter}");
+        var code = filter["DeA_Typ=4 AND DeA_Kod='".Length..^1].Replace("''", "'", StringComparison.Ordinal);
+        return _definitions.TryGetValue(code, out var id) ? new FakeDefinition(id) : null;
+    }
+}
+
+public sealed class FakeDefinition
+{
+    public FakeDefinition(int id) => ID = id;
+    public int ID { get; }
+}
+
+public sealed class FakeAttributeDocument
+{
+    public FakeAttributeCollection Atrybuty { get; } = new();
+}
+
+public sealed class FakeAttributeCollection
+{
+    public List<FakeDocumentAttribute> Items { get; } = [];
+
+    public FakeDocumentAttribute AddNew()
+    {
+        var attribute = new FakeDocumentAttribute();
+        Items.Add(attribute);
+        return attribute;
+    }
+}
+
+public sealed class FakeDocumentAttribute
+{
+    public int DeAID { get; set; }
+    private string? _value;
+    public string? Wartosc
+    {
+        get => _value;
+        set
+        {
+            if (value == "REJECTED") throw new ArgumentException("Niepoprawna wartość.");
+            _value = value;
+        }
+    }
+}