diff --git a/source/MRViewer/MRUITestEngineControl.cpp b/source/MRViewer/MRUITestEngineControl.cpp
index 7b9bb05c3ca2..a272eadff42a 100644
--- a/source/MRViewer/MRUITestEngineControl.cpp
+++ b/source/MRViewer/MRUITestEngineControl.cpp
@@ -157,7 +157,7 @@ Expected<std::vector<PathedEntry>> listAllEntries( const std::vector<std::string
     return ret;
 }
 
-Expected<void> pressButton( const std::vector<std::string>& path )
+Expected<std::string> pressButton( const std::vector<std::string>& path )
 {
     if ( path.empty() )
         return unexpected( "pressButton: Empty path not allowed here." );
@@ -177,7 +177,7 @@ Expected<void> pressButton( const std::vector<std::string>& path )
 
     const std::string_view disabledReason = ( *buttonEx )->disabledReason;
     if ( !disabledReason.empty() )
-        return unexpected( fmt::format( "pressButton {}: {}", pathToString( path ), composeStatus( disabledReason ) ) );
+        return composeStatus( disabledReason );
 
     ( *buttonEx )->simulateClick = true;
 
@@ -276,7 +276,7 @@ template Expected<Value<std::string  >> readValue( const std::vector<std::string
 
 
 template <typename T>
-Expected<void> writeValue( const std::vector<std::string>& path, T value )
+Expected<std::string> writeValue( const std::vector<std::string>& path, T value )
 {
     if ( path.empty() )
         return unexpected( "writeValue: Empty path not allowed here." );
@@ -297,9 +297,9 @@ Expected<void> writeValue( const std::vector<std::string>& path, T value )
 
     const std::string_view disabledReason = entry.disabledReason;
     if ( !disabledReason.empty() )
-        return unexpected( fmt::format( "writeValue {}: {}", pathToString( path ), composeStatus( disabledReason ) ) );
+        return composeStatus( disabledReason );
 
-    auto writeValueOfCorrectType = [&entry, &path]( auto fixedValue ) -> Expected<void>
+    auto writeValueOfCorrectType = [&entry, &path]( auto fixedValue ) -> Expected<std::string>
     {
         using U = decltype( fixedValue );
         auto &target = std::get<TestEngine::ValueEntry::Value<U>>( entry.value );
@@ -347,19 +347,19 @@ Expected<void> writeValue( const std::vector<std::string>& path, T value )
     else if constexpr ( std::is_same_v<T, double> )
     {
         return std::visit( MR::overloaded{
-            [&]( const TestEngine::ValueEntry::Value<std::string  >& ) -> Expected<void> { return unexpected( fmt::format( "writeValue: `{}` is a string, but received a number.", pathToString( path ) ) ); },
-            [&]( const TestEngine::ValueEntry::Value<double       >& ) -> Expected<void> { return writeValueOfCorrectType( value ); },
-            [&]( const TestEngine::ValueEntry::Value<std::int64_t >& ) -> Expected<void> { return unexpected( fmt::format( "writeValue: `{}` is an integer, but received a fractional number.", pathToString( path ) ) ); },
-            [&]( const TestEngine::ValueEntry::Value<std::uint64_t>& ) -> Expected<void> { return unexpected( fmt::format( "writeValue: `{}` is an integer, but received a fractional number.", pathToString( path ) ) ); },
+            [&]( const TestEngine::ValueEntry::Value<std::string  >& ) -> Expected<std::string> { return unexpected( fmt::format( "writeValue: `{}` is a string, but received a number.", pathToString( path ) ) ); },
+            [&]( const TestEngine::ValueEntry::Value<double       >& ) -> Expected<std::string> { return writeValueOfCorrectType( value ); },
+            [&]( const TestEngine::ValueEntry::Value<std::int64_t >& ) -> Expected<std::string> { return unexpected( fmt::format( "writeValue: `{}` is an integer, but received a fractional number.", pathToString( path ) ) ); },
+            [&]( const TestEngine::ValueEntry::Value<std::uint64_t>& ) -> Expected<std::string> { return unexpected( fmt::format( "writeValue: `{}` is an integer, but received a fractional number.", pathToString( path ) ) ); },
         }, entry.value );
     }
     else if constexpr ( std::is_same_v<T, std::int64_t> )
     {
         return std::visit( MR::overloaded{
-            [&]( const TestEngine::ValueEntry::Value<std::string  >& ) -> Expected<void> { return unexpected( fmt::format( "writeValue: `{}` is a string, but received a number.", pathToString( path ) ) ); },
-            [&]( const TestEngine::ValueEntry::Value<double       >& ) -> Expected<void> { return writeValueOfCorrectType( double( value ) ); },
-            [&]( const TestEngine::ValueEntry::Value<std::int64_t >& ) -> Expected<void> { return writeValueOfCorrectType( value ); },
-            [&]( const TestEngine::ValueEntry::Value<std::uint64_t>& ) -> Expected<void>
+            [&]( const TestEngine::ValueEntry::Value<std::string  >& ) -> Expected<std::string> { return unexpected( fmt::format( "writeValue: `{}` is a string, but received a number.", pathToString( path ) ) ); },
+            [&]( const TestEngine::ValueEntry::Value<double       >& ) -> Expected<std::string> { return writeValueOfCorrectType( double( value ) ); },
+            [&]( const TestEngine::ValueEntry::Value<std::int64_t >& ) -> Expected<std::string> { return writeValueOfCorrectType( value ); },
+            [&]( const TestEngine::ValueEntry::Value<std::uint64_t>& ) -> Expected<std::string>
             {
                 if ( value < 0 )
                     return unexpected( fmt::format( "writeValue: `{}` is unsigned, but received a negative number.", pathToString( path ) ) );
@@ -370,10 +370,10 @@ Expected<void> writeValue( const std::vector<std::string>& path, T value )
     else if constexpr ( std::is_same_v<T, std::uint64_t> )
     {
         return std::visit( MR::overloaded{
-            [&]( const TestEngine::ValueEntry::Value<std::string  >& ) -> Expected<void> { return unexpected( fmt::format( "writeValue: `{}` is a string, but received a number.", pathToString( path ) ) ); },
-            [&]( const TestEngine::ValueEntry::Value<double       >& ) -> Expected<void> { return writeValueOfCorrectType( double( value ) ); },
-            [&]( const TestEngine::ValueEntry::Value<std::uint64_t>& ) -> Expected<void> { return writeValueOfCorrectType( value ); },
-            [&]( const TestEngine::ValueEntry::Value<std::int64_t >& ) -> Expected<void>
+            [&]( const TestEngine::ValueEntry::Value<std::string  >& ) -> Expected<std::string> { return unexpected( fmt::format( "writeValue: `{}` is a string, but received a number.", pathToString( path ) ) ); },
+            [&]( const TestEngine::ValueEntry::Value<double       >& ) -> Expected<std::string> { return writeValueOfCorrectType( double( value ) ); },
+            [&]( const TestEngine::ValueEntry::Value<std::uint64_t>& ) -> Expected<std::string> { return writeValueOfCorrectType( value ); },
+            [&]( const TestEngine::ValueEntry::Value<std::int64_t >& ) -> Expected<std::string>
             {
                 if ( value > std::uint64_t( std::numeric_limits<std::int64_t>::max() ) )
                     return unexpected( fmt::format( "writeValue: `{}` is signed, but received an unsigned integer large enough to not be representable as `int64_t`.", pathToString( path ) ) );
@@ -383,9 +383,9 @@ Expected<void> writeValue( const std::vector<std::string>& path, T value )
     }
 }
 
-template Expected<void> writeValue( const std::vector<std::string>& path, std::int64_t  value );
-template Expected<void> writeValue( const std::vector<std::string>& path, std::uint64_t value );
-template Expected<void> writeValue( const std::vector<std::string>& path, double        value );
-template Expected<void> writeValue( const std::vector<std::string>& path, std::string   value );
+template Expected<std::string> writeValue( const std::vector<std::string>& path, std::int64_t  value );
+template Expected<std::string> writeValue( const std::vector<std::string>& path, std::uint64_t value );
+template Expected<std::string> writeValue( const std::vector<std::string>& path, double        value );
+template Expected<std::string> writeValue( const std::vector<std::string>& path, std::string   value );
 
 } // namespace MR::UI::TestEngine::Control
diff --git a/source/MRViewer/MRUITestEngineControl.h b/source/MRViewer/MRUITestEngineControl.h
index 8cf2b752104e..4c6a3e74b8f6 100644
--- a/source/MRViewer/MRUITestEngineControl.h
+++ b/source/MRViewer/MRUITestEngineControl.h
@@ -68,8 +68,11 @@ using PathedEntry = std::pair<std::vector<std::string>, TypedEntry>;
 // and their descendants appear on subsequent rows with `path` extending theirs.
 [[nodiscard]] MRVIEWER_API Expected<std::vector<PathedEntry>> listAllEntries( const std::vector<std::string>& rootPath );
 
-// Presses the button at this path, or returns an error.
-MRVIEWER_API Expected<void> pressButton( const std::vector<std::string>& path );
+// Presses the button at this path.
+// Returns empty string on success (click simulated). If the button was drawn disabled, the press is a silent
+// no-op and the return is a non-empty status (`"disabled"` / `"disabled: <reason>"`) matching `composeStatus()`.
+// `unexpected` is returned only for hard errors (path not found, entry is not a button).
+MRVIEWER_API Expected<std::string> pressButton( const std::vector<std::string>& path );
 
 // Read/write values: (drags, sliders, etc)
 
@@ -101,14 +104,17 @@ extern template MRVIEWER_API Expected<Value<std::uint64_t>> readValue( const std
 extern template MRVIEWER_API Expected<Value<double       >> readValue( const std::vector<std::string>& path );
 extern template MRVIEWER_API Expected<Value<std::string  >> readValue( const std::vector<std::string>& path );
 
-// Modifies the value at the `path`, or returns an error if the path, type or value are wrong.
+// Modifies the value at the `path`.
+// Returns empty string on success (write simulated). If the widget was drawn disabled, the write is a silent
+// no-op and the return is a non-empty status (`"disabled"` / `"disabled: <reason>"`) matching `composeStatus()`.
+// `unexpected` is returned only for hard errors (path not found, wrong type, out-of-range / not-in-allowedValues).
 template <typename T>
-MRVIEWER_API Expected<void> writeValue( const std::vector<std::string>& path, T value );
+MRVIEWER_API Expected<std::string> writeValue( const std::vector<std::string>& path, T value );
 
-extern template MRVIEWER_API Expected<void> writeValue( const std::vector<std::string>& path, std::int64_t  value );
-extern template MRVIEWER_API Expected<void> writeValue( const std::vector<std::string>& path, std::uint64_t value );
-extern template MRVIEWER_API Expected<void> writeValue( const std::vector<std::string>& path, double        value );
-extern template MRVIEWER_API Expected<void> writeValue( const std::vector<std::string>& path, std::string   value );
+extern template MRVIEWER_API Expected<std::string> writeValue( const std::vector<std::string>& path, std::int64_t  value );
+extern template MRVIEWER_API Expected<std::string> writeValue( const std::vector<std::string>& path, std::uint64_t value );
+extern template MRVIEWER_API Expected<std::string> writeValue( const std::vector<std::string>& path, double        value );
+extern template MRVIEWER_API Expected<std::string> writeValue( const std::vector<std::string>& path, std::string   value );
 
 
 } // namespace MR::UI::TestEngine::Control
diff --git a/source/MRViewer/MRViewerMcp.cpp b/source/MRViewer/MRViewerMcp.cpp
index 6410faa49d14..87e092953baa 100644
--- a/source/MRViewer/MRViewerMcp.cpp
+++ b/source/MRViewer/MRViewerMcp.cpp
@@ -2,6 +2,7 @@
 
 #include "MRMcp/MRMcp.h"
 #include "MRMesh/MROnInit.h"
+#include "MRPch/MRFmt.h"
 #include "MRViewer/MRCommandLoop.h"
 #include "MRViewer/MRUITestEngineControl.h"
 
@@ -75,11 +76,15 @@ static nlohmann::json mcpToolListAllUiEntries( const nlohmann::json& args )
 
 static nlohmann::json mcpToolPressButton( const nlohmann::json& args )
 {
+    const auto path = args.at( "path" ).get<std::vector<std::string>>();
     MR::CommandLoop::runCommandFromGUIThread( [&]
     {
-        auto ex = UI::TestEngine::Control::pressButton( args.at( "path" ).get<std::vector<std::string>>() );
+        auto ex = UI::TestEngine::Control::pressButton( path );
         if ( !ex )
             throw std::runtime_error( ex.error() );
+        // Non-empty = disabled status; surface to MCP as an error (empty = OK, click simulated).
+        if ( !ex->empty() )
+            throw std::runtime_error( fmt::format( "pressButton {}: {}", UI::TestEngine::Control::pathToString( path ), *ex ) );
     } );
     skipFramesAfterInput();
 
@@ -117,11 +122,15 @@ static nlohmann::json mcpToolReadValue( const nlohmann::json& args )
 template <typename T>
 static nlohmann::json mcpToolWriteValue( const nlohmann::json& args )
 {
+    const auto path = args.at( "path" ).get<std::vector<std::string>>();
     MR::CommandLoop::runCommandFromGUIThread( [&]
     {
-        auto ex = UI::TestEngine::Control::writeValue<T>( args.at( "path" ).get<std::vector<std::string>>(), T( args.at( "value" ) ) );
+        auto ex = UI::TestEngine::Control::writeValue<T>( path, T( args.at( "value" ) ) );
         if ( !ex )
             throw std::runtime_error( ex.error() );
+        // Non-empty = disabled status; surface to MCP as an error (empty = OK, write simulated).
+        if ( !ex->empty() )
+            throw std::runtime_error( fmt::format( "writeValue {}: {}", UI::TestEngine::Control::pathToString( path ), *ex ) );
     } );
     skipFramesAfterInput();
 
diff --git a/source/mrviewerpy/MRPythonUiInteraction.cpp b/source/mrviewerpy/MRPythonUiInteraction.cpp
index e06911f2a4c9..a28fb979fba4 100644
--- a/source/mrviewerpy/MRPythonUiInteraction.cpp
+++ b/source/mrviewerpy/MRPythonUiInteraction.cpp
@@ -75,7 +75,10 @@ MR_ADD_PYTHON_FUNCTION( mrviewerpy, uiPressButton,
         MR::CommandLoop::runCommandFromGUIThread( [&]
         {
             spdlog::info( "pressButton {}: frame {}", MR::UI::TestEngine::Control::pathToString( path ), MR::getViewerInstance().getTotalFrames() );
-            MR::expectedValueOrThrow( MR::UI::TestEngine::Control::pressButton( path ) );
+            // Empty status = OK (click simulated); non-empty = disabled (silent no-op — pre-#5961 test contract).
+            auto status = MR::expectedValueOrThrow( MR::UI::TestEngine::Control::pressButton( path ) );
+            if ( !status.empty() )
+                spdlog::warn( "pressButton {}: {} (silent no-op)", MR::UI::TestEngine::Control::pathToString( path ), status );
         } );
         for ( int i = 0; i < MR::getViewerInstance().forceRedrawMinimumIncrementAfterEvents; ++i )
             MR::CommandLoop::runCommandFromGUIThread( [] {} ); // Wait a few frames.
@@ -117,7 +120,10 @@ namespace
     {
         MR::CommandLoop::runCommandFromGUIThread( [&]
         {
-            MR::expectedValueOrThrow( Control::writeValue<T>( path, std::move( value ) ) );
+            // Empty status = OK (write simulated); non-empty = disabled (silent no-op — pre-#5961 test contract).
+            auto status = MR::expectedValueOrThrow( Control::writeValue<T>( path, std::move( value ) ) );
+            if ( !status.empty() )
+                spdlog::warn( "writeValue {}: {} (silent no-op)", Control::pathToString( path ), status );
         } );
     }
 }