diff --git a/firmware/controllers/algo/rusefi_generated.h b/firmware/controllers/algo/rusefi_generated.h
index bd4a0f7628..c00ac81ad3 100644
--- a/firmware/controllers/algo/rusefi_generated.h
+++ b/firmware/controllers/algo/rusefi_generated.h
@@ -1,5 +1,5 @@
 //
-// generated by ConfigDefinition.jar tool based on rusefi_config.txt
+// was generated automatically by ConfigDefinition.jar based on integration\rusefi_config.txt
 //
 
 #define accelerometerSpiDevice_offset 2736
diff --git a/firmware/gen_config.bat b/firmware/gen_config.bat
index 7e25f69e3f..7ceaeab12c 100644
--- a/firmware/gen_config.bat
+++ b/firmware/gen_config.bat
@@ -5,7 +5,14 @@ rem the storage section of rusefi.ini is updated as well
 rem lazy is broken - TS input is not considered a change
 rm build/config.gen
 
-java -jar ../java_tools/ConfigDefinition.jar -definition integration\rusefi_config.txt -romraider integration -ts_destination tunerstudio -c_defines controllers\algo\rusefi_generated.h -c_destination controllers\algo\engine_configuration_generated_structures.h -java_destination ../java_console -skip build/config.gen
+java -Drusefi.generator.lazyfile.enabled=true ^
+ -jar ../java_tools/ConfigDefinition.jar ^
+ -definition integration\rusefi_config.txt ^
+ -romraider integration ^
+ -ts_destination tunerstudio ^
+ -c_defines controllers\algo\rusefi_generated.h ^
+ -c_destination controllers\algo\engine_configuration_generated_structures.h ^
+ -java_destination ../java_console -skip build/config.gen
 
 
 rem This would automatically copy latest file to 'dev' TS project
diff --git a/java_console/rusefi.xml b/java_console/rusefi.xml
index e64fb4ec12..370c2cfacf 100644
--- a/java_console/rusefi.xml
+++ b/java_console/rusefi.xml
@@ -1,6 +1,6 @@
 <roms>
 
-<!-- Generated by ConfigDefinition utility on Fri Feb 22 22:08:31 EST 2019 -->
+<!-- was generated automatically by ConfigDefinition.jar based on Sat Jun 01 16:45:56 EDT 2019 -->
 
     <rom>
         <romid>
diff --git a/java_tools/ConfigDefinition.jar b/java_tools/ConfigDefinition.jar
index d5d87a27eb..c37f614d3e 100644
Binary files a/java_tools/ConfigDefinition.jar and b/java_tools/ConfigDefinition.jar differ
diff --git a/java_tools/configuration_definition/.idea/runConfigurations/ConfigDefinition.xml b/java_tools/configuration_definition/.idea/runConfigurations/ConfigDefinition.xml
index 23175c3bc9..887631adc6 100644
--- a/java_tools/configuration_definition/.idea/runConfigurations/ConfigDefinition.xml
+++ b/java_tools/configuration_definition/.idea/runConfigurations/ConfigDefinition.xml
@@ -2,7 +2,8 @@
   <configuration default="false" name="ConfigDefinition" type="Application" factoryName="Application" nameIsGenerated="true">
     <option name="MAIN_CLASS_NAME" value="com.rusefi.ConfigDefinition" />
     <module name="configuration_definition" />
-    <option name="PROGRAM_PARAMETERS" value="-definition ../../firmware/integration/rusefi_config.txt -ts_destination ../../firmware/tunerstudio -c_destination ../../firmware/controllers\algo\engine_configuration_generated_structures.h -java_destination ../../java_console -skip lastMd5" />
+    <option name="PROGRAM_PARAMETERS" value="-definition ../../firmware/integration/rusefi_config.txt -ts_destination ../../firmware/tunerstudio -c_destination ../../firmware/controllers\algo\engine_configuration_generated_structures.h -java_destination ../../java_console" />
+    <option name="VM_PARAMETERS" value="-Drusefi.generator.lazyfile.enabled=true" />
     <RunnerSettings RunnerId="Debug">
       <option name="DEBUG_PORT" value="" />
       <option name="TRANSPORT" value="0" />
diff --git a/java_tools/configuration_definition/src/com/rusefi/ConfigDefinition.java b/java_tools/configuration_definition/src/com/rusefi/ConfigDefinition.java
index ed4deee456..d0225bf8b9 100644
--- a/java_tools/configuration_definition/src/com/rusefi/ConfigDefinition.java
+++ b/java_tools/configuration_definition/src/com/rusefi/ConfigDefinition.java
@@ -4,6 +4,7 @@ import com.rusefi.output.CHeaderConsumer;
 import com.rusefi.output.ConfigurationConsumer;
 import com.rusefi.output.JavaFieldsConsumer;
 import com.rusefi.output.TSProjectConsumer;
+import com.rusefi.util.LazyFile;
 
 import java.io.*;
 import java.math.BigInteger;
@@ -20,6 +21,7 @@ import java.util.List;
 @SuppressWarnings("StringConcatenationInsideStringBufferAppend")
 public class ConfigDefinition {
     public static final String EOL = "\n";
+    public static final String GENERATED_AUTOMATICALLY_TAG = "was generated automatically by ConfigDefinition.jar based on ";
     public static String MESSAGE;
 
     private static final String ROM_RAIDER_XML_TEMPLATE = "rusefi_template.xml";
@@ -32,6 +34,7 @@ public class ConfigDefinition {
     private static final String KEY_CONSOLE_DESTINATION = "-java_destination";
     private static final String KEY_PREPEND = "-prepend";
     private static final String KEY_SKIP = "-skip";
+    public static String definitionInputFile = null;
 
     public static void main(String[] args) throws IOException {
         if (args.length < 2) {
@@ -44,7 +47,6 @@ public class ConfigDefinition {
             return;
         }
 
-        String definitionInputFile = null;
         String tsPath = null;
         String destCHeader = null;
         String destCDefines = null;
@@ -76,7 +78,7 @@ public class ConfigDefinition {
             }
         }
 
-        MESSAGE = "was generated automatically by ConfigDefinition.jar based on " + definitionInputFile + " " + new Date();
+        MESSAGE = GENERATED_AUTOMATICALLY_TAG + definitionInputFile + " " + new Date();
 
         System.out.println("Reading from " + definitionInputFile);
 
@@ -169,13 +171,12 @@ public class ConfigDefinition {
         System.out.println("Reading from " + inputFileName);
         System.out.println("Writing to " + outputFileName);
 
-        VariableRegistry.INSTANCE.put("generator_message", "Generated by ConfigDefinition utility on " + new Date());
+        VariableRegistry.INSTANCE.put("generator_message", ConfigDefinition.GENERATED_AUTOMATICALLY_TAG + new Date());
 
         File inputFile = new File(inputFileName);
 
-        File outputFile = new File(outputFileName);
         BufferedReader fr = new BufferedReader(new FileReader(inputFile));
-        FileWriter fw = new FileWriter(outputFile);
+        LazyFile fw = new LazyFile(outputFileName);
 
         String line;
         while ((line = fr.readLine()) != null) {
diff --git a/java_tools/configuration_definition/src/com/rusefi/VariableRegistry.java b/java_tools/configuration_definition/src/com/rusefi/VariableRegistry.java
index b41066cc4b..ea2e6db2dd 100644
--- a/java_tools/configuration_definition/src/com/rusefi/VariableRegistry.java
+++ b/java_tools/configuration_definition/src/com/rusefi/VariableRegistry.java
@@ -1,7 +1,8 @@
 package com.rusefi;
 
+import com.rusefi.util.LazyFile;
+
 import java.io.BufferedWriter;
-import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.util.*;
@@ -96,9 +97,9 @@ public class VariableRegistry extends TreeMap<String, String> {
 
     public void writeNumericsToFile(String fileName) throws IOException {
         System.out.println("Writing to " + fileName);
-        BufferedWriter cHeader = new BufferedWriter(new FileWriter(fileName));
+        LazyFile cHeader = new LazyFile(fileName);
 
-        cHeader.write("//\n// generated by ConfigDefinition.jar tool based on rusefi_config.txt\n//\n\n");
+        cHeader.write("//\n// " + ConfigDefinition.GENERATED_AUTOMATICALLY_TAG + ConfigDefinition.definitionInputFile + "\n//\n\n");
         for (String value : cAllDefinitions.values())
             cHeader.write(value);
         cHeader.close();
diff --git a/java_tools/configuration_definition/src/com/rusefi/output/CHeaderConsumer.java b/java_tools/configuration_definition/src/com/rusefi/output/CHeaderConsumer.java
index 38732c5cca..c1610bc53c 100644
--- a/java_tools/configuration_definition/src/com/rusefi/output/CHeaderConsumer.java
+++ b/java_tools/configuration_definition/src/com/rusefi/output/CHeaderConsumer.java
@@ -3,6 +3,7 @@ package com.rusefi.output;
 import com.rusefi.ConfigDefinition;
 import com.rusefi.ConfigField;
 import com.rusefi.ConfigStructure;
+import com.rusefi.util.LazyFile;
 
 import java.io.BufferedWriter;
 import java.io.FileWriter;
@@ -15,11 +16,11 @@ import static com.rusefi.ConfigDefinition.EOL;
  */
 public class CHeaderConsumer implements ConfigurationConsumer {
     public static final String BOOLEAN_TYPE = "bool";
-    private final BufferedWriter cHeader;
+    private final LazyFile cHeader;
 
     public CHeaderConsumer(String destCHeader) throws IOException {
         System.out.println("Writing C header to " + destCHeader);
-        cHeader = new BufferedWriter(new FileWriter(destCHeader));
+        cHeader = new LazyFile(destCHeader);
         cHeader.write("// this section " + ConfigDefinition.MESSAGE + EOL);
         cHeader.write("// begin" + EOL);
         String id = destCHeader.replaceAll("[\\\\\\.\\/]", "_").toUpperCase();
diff --git a/java_tools/configuration_definition/src/com/rusefi/output/JavaFieldsConsumer.java b/java_tools/configuration_definition/src/com/rusefi/output/JavaFieldsConsumer.java
index 248a13065f..46f12cdead 100644
--- a/java_tools/configuration_definition/src/com/rusefi/output/JavaFieldsConsumer.java
+++ b/java_tools/configuration_definition/src/com/rusefi/output/JavaFieldsConsumer.java
@@ -1,6 +1,7 @@
 package com.rusefi.output;
 
 import com.rusefi.*;
+import com.rusefi.util.LazyFile;
 
 import java.io.*;
 import java.util.HashSet;
@@ -20,14 +21,14 @@ public class JavaFieldsConsumer implements ConfigurationConsumer {
     private final CharArrayWriter javaFieldsWriter;
     private final ReaderState state;
     private final String javaConsolePath;
-    private final BufferedWriter javaFields;
+    private final LazyFile javaFields;
 
     public JavaFieldsConsumer(CharArrayWriter javaFieldsWriter, ReaderState state, String javaConsolePath) throws IOException {
         this.javaFieldsWriter = javaFieldsWriter;
         this.state = state;
         this.javaConsolePath = javaConsolePath;
 
-        javaFields = new BufferedWriter(new FileWriter(javaConsolePath + File.separator + JAVA_SOURCE_CODE_FILE_NAME));
+        javaFields = new LazyFile(javaConsolePath + File.separator + JAVA_SOURCE_CODE_FILE_NAME);
     }
 
     public static int writeJavaFields(List<ConfigField> tsFields, ReaderState state, String prefix, Writer javaFieldsWriter, int tsPosition) throws IOException {
diff --git a/java_tools/configuration_definition/src/com/rusefi/output/TSProjectConsumer.java b/java_tools/configuration_definition/src/com/rusefi/output/TSProjectConsumer.java
index 761223ee00..900322ed63 100644
--- a/java_tools/configuration_definition/src/com/rusefi/output/TSProjectConsumer.java
+++ b/java_tools/configuration_definition/src/com/rusefi/output/TSProjectConsumer.java
@@ -1,6 +1,7 @@
 package com.rusefi.output;
 
 import com.rusefi.*;
+import com.rusefi.util.LazyFile;
 
 import java.io.*;
 
@@ -99,7 +100,7 @@ public class TSProjectConsumer implements ConfigurationConsumer {
         TsFileContent tsContent = readTsFile(tsPath);
         System.out.println("Got " + tsContent.getPrefix().length() + "/" + tsContent.getPostfix().length() + " of " + TS_FILE_INPUT_NAME);
 
-        BufferedWriter tsHeader = new BufferedWriter(new FileWriter(tsPath + File.separator + TS_FILE_OUTPUT_NAME));
+        LazyFile tsHeader = new LazyFile(tsPath + File.separator + TS_FILE_OUTPUT_NAME);
         tsHeader.write(tsContent.getPrefix());
 
         tsHeader.write("; " + CONFIG_DEFINITION_START + ConfigDefinition.EOL);
diff --git a/java_tools/configuration_definition/src/com/rusefi/util/LazyFile.java b/java_tools/configuration_definition/src/com/rusefi/util/LazyFile.java
new file mode 100644
index 0000000000..10b3908850
--- /dev/null
+++ b/java_tools/configuration_definition/src/com/rusefi/util/LazyFile.java
@@ -0,0 +1,72 @@
+package com.rusefi.util;
+
+import com.rusefi.ConfigDefinition;
+
+import java.io.*;
+import java.nio.file.Paths;
+import java.util.Scanner;
+import java.util.regex.Pattern;
+
+/**
+ * This file would override file content only of content has changed, disregarding the magic tag line.
+ */
+public class LazyFile {
+    private static final String PROPERTY_NAME = "rusefi.generator.lazyfile.enabled";
+    private static boolean ENABLED = Boolean.getBoolean(PROPERTY_NAME);
+
+    static {
+        System.out.println(PROPERTY_NAME + "=" + ENABLED);
+    }
+
+    private String filename;
+
+    private final StringBuffer content = new StringBuffer();
+    private final StringBuffer contentWithoutTag = new StringBuffer();
+
+    public LazyFile(String filename) {
+        this.filename = filename;
+    }
+
+    public void write(String line) {
+        content.append(line);
+        if (!line.contains(ConfigDefinition.GENERATED_AUTOMATICALLY_TAG))
+            contentWithoutTag.append(line);
+    }
+
+    public void close() throws IOException {
+        String fileContent = unifySpaces(readCurrentContent(filename));
+        String newContent = unifySpaces(contentWithoutTag.toString().trim());
+        if (fileContent.equals(newContent)) {
+            System.out.println(getClass().getSimpleName() + ": Not updating " + filename + " since looks to be the same content");
+            return;
+        }
+        for (int i = 0; i < Math.min(fileContent.length(), newContent.length()); i++) {
+            if (fileContent.charAt(i) != newContent.charAt(i)) {
+                System.out.println(getClass().getSimpleName() + " " + filename + ": Not same at " + i);
+                break;
+            }
+        }
+        FileWriter fw = new FileWriter(filename);
+        fw.write(content.toString());
+        fw.close();
+    }
+
+    private static String unifySpaces(String line) {
+        return line.replaceAll("\n[\n]*", "\n").trim();
+    }
+
+    private String readCurrentContent(String filename) throws IOException {
+        if (!new File(filename).exists())
+            return "";
+        BufferedReader br = new BufferedReader(new FileReader(filename));
+        Scanner in = new Scanner(Paths.get(filename), "UTF-8");
+        String line;
+        Pattern pat = Pattern.compile(".*\\R|.+\\z");
+        StringBuffer sb = new StringBuffer();
+        while ((line = in.findWithinHorizon(pat, 0)) != null) {
+            if (!line.contains(ConfigDefinition.GENERATED_AUTOMATICALLY_TAG))
+                sb.append(line);
+        }
+        return sb.toString();
+    }
+}