diff --git a/elasticsearch/x-pack/src/main/java/org/elasticsearch/xpack/common/text/TextTemplate.java b/elasticsearch/x-pack/src/main/java/org/elasticsearch/xpack/common/text/TextTemplate.java
index a3c31fac856..83ce0db34e6 100644
--- a/elasticsearch/x-pack/src/main/java/org/elasticsearch/xpack/common/text/TextTemplate.java
+++ b/elasticsearch/x-pack/src/main/java/org/elasticsearch/xpack/common/text/TextTemplate.java
@@ -27,6 +27,8 @@ import java.util.Objects;
  */
 public class TextTemplate implements ToXContent {
 
+    public static final String DEFAULT_TEMPLATE_LANG = "mustache";
+
     private final Script script;
     private final String inlineTemplate;
 
@@ -37,7 +39,7 @@ public class TextTemplate implements ToXContent {
 
     public TextTemplate(String template, @Nullable XContentType contentType, ScriptType type,
                         @Nullable Map<String, Object> params) {
-        this.script = new Script(template, type, "mustache", params, contentType);
+        this.script = new Script(template, type, DEFAULT_TEMPLATE_LANG, params, contentType);
         this.inlineTemplate = null;
     }
 
@@ -95,7 +97,7 @@ public class TextTemplate implements ToXContent {
         if (parser.currentToken() == XContentParser.Token.VALUE_STRING) {
             return new TextTemplate(parser.text());
         } else {
-            return new TextTemplate(Script.parse(parser, ParseFieldMatcher.STRICT, "mustache"));
+            return new TextTemplate(Script.parse(parser, ParseFieldMatcher.STRICT, DEFAULT_TEMPLATE_LANG));
         }
     }
 }
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionRegistry.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionRegistry.java
index 0579ac92ead..9a93cf7c561 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionRegistry.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionRegistry.java
@@ -45,7 +45,7 @@ public class ActionRegistry {
         return parsers.get(type);
     }
 
-    public ExecutableActions parseActions(String watchId, XContentParser parser) throws IOException {
+    public ExecutableActions parseActions(String watchId, XContentParser parser, boolean upgradeActionSource) throws IOException {
         if (parser.currentToken() != XContentParser.Token.START_OBJECT) {
             throw new ElasticsearchParseException("could not parse actions for watch [{}]. expected an object but found [{}] instead",
                     watchId, parser.currentToken());
@@ -62,7 +62,8 @@ public class ActionRegistry {
                     throw new ElasticsearchParseException("could not parse action [{}] for watch [{}]. {}", id, watchId, error);
                 }
             } else if (token == XContentParser.Token.START_OBJECT && id != null) {
-                actions.add(ActionWrapper.parse(watchId, id, parser, this, conditionRegistry, transformRegistry, clock, licenseState));
+                actions.add(ActionWrapper.parse(watchId, id, parser, this, conditionRegistry, transformRegistry, clock,
+                        licenseState, upgradeActionSource));
             }
         }
         return new ExecutableActions(actions);
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionWrapper.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionWrapper.java
index 219684a8b71..e8fc9024cb8 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionWrapper.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/ActionWrapper.java
@@ -201,7 +201,7 @@ public class ActionWrapper implements ToXContent {
 
     static ActionWrapper parse(String watchId, String actionId, XContentParser parser,
                                ActionRegistry actionRegistry, ConditionRegistry conditionRegistry, TransformRegistry transformRegistry,
-                               Clock clock, XPackLicenseState licenseState) throws IOException {
+                               Clock clock, XPackLicenseState licenseState, boolean upgradeActionSource) throws IOException {
 
         assert parser.currentToken() == XContentParser.Token.START_OBJECT;
 
@@ -217,9 +217,9 @@ public class ActionWrapper implements ToXContent {
                 currentFieldName = parser.currentName();
             } else {
                 if (ParseFieldMatcher.STRICT.match(currentFieldName, Watch.Field.CONDITION)) {
-                    condition = conditionRegistry.parseExecutable(watchId, parser);
+                    condition = conditionRegistry.parseExecutable(watchId, parser, upgradeActionSource);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Transform.Field.TRANSFORM)) {
-                    transform = transformRegistry.parse(watchId, parser);
+                    transform = transformRegistry.parse(watchId, parser, upgradeActionSource);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Throttler.Field.THROTTLE_PERIOD)) {
                     throttlePeriod = timeValueMillis(parser.longValue());
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Throttler.Field.THROTTLE_PERIOD_HUMAN)) {
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionFactory.java
index 3de9db7ff69..980c541b928 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionFactory.java
@@ -28,8 +28,14 @@ public abstract class ConditionFactory<C extends Condition, R extends Condition.
 
     /**
      * Parses the given xcontent and creates a concrete condition
+     *
+     * @param watchId                   The id of the watch
+     * @param parser                    The parsing that contains the condition content
+     * @param upgradeConditionSource    Whether to upgrade the source related to condition if in legacy format
+     *                                  Note: depending on the version, only conditions implementations that have a
+     *                                  known legacy format will support this option, otherwise this is a noop.
      */
-    public abstract C parseCondition(String watchId, XContentParser parser) throws IOException;
+    public abstract C parseCondition(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException;
 
     /**
      * Creates an {@link ExecutableCondition executable condition} for the given condition.
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionRegistry.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionRegistry.java
index b10894daff8..3f02b1f50be 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionRegistry.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/ConditionRegistry.java
@@ -40,9 +40,15 @@ public class ConditionRegistry {
      *         }
      *     }
      * </code></pre>
+     *
+     * @param watchId                   The id of the watch
+     * @param parser                    The parsing that contains the condition content
+     * @param upgradeConditionSource    Whether to upgrade the source related to condition if in legacy format
+     *                                  Note: depending on the version, only conditions implementations that have a
+     *                                  known legacy format will support this option, otherwise this is a noop.
      */
-    public ExecutableCondition parseExecutable(String watchId, XContentParser parser) throws IOException {
-        Condition condition = parseCondition(watchId, parser);
+    public ExecutableCondition parseExecutable(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException {
+        Condition condition = parseCondition(watchId, parser, upgradeConditionSource);
         return factories.get(condition.type()).createExecutable(condition);
     }
 
@@ -56,7 +62,7 @@ public class ConditionRegistry {
      *     }
      * </code></pre>
      */
-    public Condition parseCondition(String watchId, XContentParser parser) throws IOException {
+    public Condition parseCondition(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException {
         Condition condition = null;
         ConditionFactory factory = null;
 
@@ -74,7 +80,7 @@ public class ConditionRegistry {
                     throw new ElasticsearchParseException("could not parse condition for watch [{}]. unknown condition type [{}]",
                             watchId, type);
                 }
-                condition = factory.parseCondition(watchId, parser);
+                condition = factory.parseCondition(watchId, parser, upgradeConditionSource);
             }
         }
         if (condition == null) {
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionFactory.java
index 73001a21839..c2da3cb1e1e 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionFactory.java
@@ -32,7 +32,7 @@ public class AlwaysConditionFactory extends ConditionFactory<AlwaysCondition, Al
     }
 
     @Override
-    public AlwaysCondition parseCondition(String watchId, XContentParser parser) throws IOException {
+    public AlwaysCondition parseCondition(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException {
         return AlwaysCondition.parse(watchId, parser);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionFactory.java
index 6adbd0a89de..6c186ea3838 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionFactory.java
@@ -33,7 +33,7 @@ public class CompareConditionFactory extends ConditionFactory<CompareCondition,
     }
 
     @Override
-    public CompareCondition parseCondition(String watchId, XContentParser parser) throws IOException {
+    public CompareCondition parseCondition(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException {
         return CompareCondition.parse(watchId, parser);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionFactory.java
index 9ec22e89b9d..5cab4154e76 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionFactory.java
@@ -31,7 +31,7 @@ public class ArrayCompareConditionFactory extends ConditionFactory<ArrayCompareC
     }
 
     @Override
-    public ArrayCompareCondition parseCondition(String watchId, XContentParser parser) throws IOException {
+    public ArrayCompareCondition parseCondition(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException {
         return ArrayCompareCondition.parse(watchId, parser);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionFactory.java
index 1318a3897c7..5aebce5d5fb 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionFactory.java
@@ -32,7 +32,7 @@ public class NeverConditionFactory extends ConditionFactory<NeverCondition, Neve
     }
 
     @Override
-    public NeverCondition parseCondition(String watchId, XContentParser parser) throws IOException {
+    public NeverCondition parseCondition(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException {
         return NeverCondition.parse(watchId, parser);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptCondition.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptCondition.java
index 97dd7870227..46ff0aa8f9d 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptCondition.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptCondition.java
@@ -53,9 +53,15 @@ public class ScriptCondition implements Condition {
         return script.hashCode();
     }
 
-    public static ScriptCondition parse(String watchId, XContentParser parser) throws IOException {
+    public static ScriptCondition parse(String watchId, XContentParser parser, boolean upgradeConditionSource,
+                                        String defaultLegacyScriptLanguage) throws IOException {
         try {
-            Script script = Script.parse(parser, ParseFieldMatcher.STRICT);
+            Script script;
+            if (upgradeConditionSource) {
+                script = Script.parse(parser, ParseFieldMatcher.STRICT, defaultLegacyScriptLanguage);
+            } else {
+                script = Script.parse(parser, ParseFieldMatcher.STRICT);
+            }
             return new ScriptCondition(script);
         } catch (ElasticsearchParseException pe) {
             throw new ElasticsearchParseException("could not parse [{}] condition for watch [{}]. failed to parse script", pe, TYPE,
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionFactory.java
index 0d575269157..f482560b026 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionFactory.java
@@ -10,20 +10,20 @@ import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.script.ScriptSettings;
 import org.elasticsearch.xpack.watcher.condition.ConditionFactory;
 
 import java.io.IOException;
 
-/**
- *
- */
 public class ScriptConditionFactory extends ConditionFactory<ScriptCondition, ScriptCondition.Result, ExecutableScriptCondition> {
 
+    private final Settings settings;
     private final ScriptService scriptService;
 
     @Inject
     public ScriptConditionFactory(Settings settings, ScriptService service) {
         super(Loggers.getLogger(ExecutableScriptCondition.class, settings));
+        this.settings = settings;
         scriptService = service;
     }
 
@@ -33,8 +33,9 @@ public class ScriptConditionFactory extends ConditionFactory<ScriptCondition, Sc
     }
 
     @Override
-    public ScriptCondition parseCondition(String watchId, XContentParser parser) throws IOException {
-        return ScriptCondition.parse(watchId, parser);
+    public ScriptCondition parseCondition(String watchId, XContentParser parser, boolean upgradeConditionSource) throws IOException {
+        String defaultLegacyScriptLanguage = ScriptSettings.getLegacyDefaultLang(settings);
+        return ScriptCondition.parse(watchId, parser, upgradeConditionSource, defaultLegacyScriptLanguage);
     }
 
     @Override
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputFactory.java
index 6d7e900fe14..a37dbcb7cde 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputFactory.java
@@ -28,16 +28,22 @@ public abstract class InputFactory<I extends Input, R extends Input.Result, E ex
 
     /**
      * Parses the given xcontent and creates a concrete input
+     *
+     * @param watchId               The id of the watch
+     * @param parser                The parser containing the input content of the watch
+     * @param upgradeInputSource    Whether to upgrade the source related to the inpit if that source is in legacy format
+     *                              Note: depending on the version, only input implementations that have a known legacy
+     *                              format will support this option, otherwise this is a noop.
      */
-    public abstract I parseInput(String watchId, XContentParser parser) throws IOException;
+    public abstract I parseInput(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException;
 
     /**
      * Creates an executable input out of the given input.
      */
     public abstract E createExecutable(I input);
 
-    public E parseExecutable(String watchId, XContentParser parser) throws IOException {
-        I input = parseInput(watchId, parser);
+    public E parseExecutable(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException {
+        I input = parseInput(watchId, parser, upgradeInputSource);
         return createExecutable(input);
     }
 }
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputRegistry.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputRegistry.java
index c83fb47b9f4..d28feb38828 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputRegistry.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/InputRegistry.java
@@ -35,6 +35,17 @@ public class InputRegistry {
      * @return          A new input instance from the parser
      */
     public ExecutableInput parse(String watchId, XContentParser parser) throws IOException {
+        return parse(watchId, parser, false);
+    }
+
+    /**
+     * Reads the contents of parser to create the correct Input
+     *
+     * @param parser                The parser containing the input definition
+     * @param upgradeInputSource    Whether to upgrade the source related to input if in legacy format.
+     * @return                      A new input instance from the parser
+     */
+    public ExecutableInput parse(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException {
         String type = null;
 
         if (parser.currentToken() != XContentParser.Token.START_OBJECT) {
@@ -55,7 +66,7 @@ public class InputRegistry {
                 if (factory == null) {
                     throw new ElasticsearchParseException("could not parse input for watch [{}]. unknown input type [{}]", watchId, type);
                 }
-                input = factory.parseExecutable(watchId, parser);
+                input = factory.parseExecutable(watchId, parser, upgradeInputSource);
             } else {
                 throw new ElasticsearchParseException("could not parse input for watch [{}]. expected an object representing input [{}], " +
                         "but found [{}] instead", watchId, type, token);
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputFactory.java
index 3579d60c0f9..7d9d5104d06 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputFactory.java
@@ -7,7 +7,6 @@ package org.elasticsearch.xpack.watcher.input.chain;
 
 import org.elasticsearch.common.collect.Tuple;
 import org.elasticsearch.common.inject.Inject;
-import org.elasticsearch.common.inject.Injector;
 import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentParser;
@@ -36,7 +35,7 @@ public class ChainInputFactory extends InputFactory<ChainInput, ChainInput.Resul
     }
 
     @Override
-    public ChainInput parseInput(String watchId, XContentParser parser) throws IOException {
+    public ChainInput parseInput(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException {
         return ChainInput.parse(watchId, parser, inputRegistry);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/http/HttpInputFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/http/HttpInputFactory.java
index 1c6c49cd2b3..03ae56ba298 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/http/HttpInputFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/http/HttpInputFactory.java
@@ -40,7 +40,7 @@ public final class HttpInputFactory extends InputFactory<HttpInput, HttpInput.Re
     }
 
     @Override
-    public HttpInput parseInput(String watchId, XContentParser parser) throws IOException {
+    public HttpInput parseInput(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException {
         return HttpInput.parse(watchId, parser, requestTemplateParser);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/none/NoneInputFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/none/NoneInputFactory.java
index 87c6c6b0eff..a9a32821547 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/none/NoneInputFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/none/NoneInputFactory.java
@@ -29,7 +29,7 @@ public class NoneInputFactory extends InputFactory<NoneInput, NoneInput.Result,
     }
 
     @Override
-    public NoneInput parseInput(String watchId, XContentParser parser) throws IOException {
+    public NoneInput parseInput(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException {
         return NoneInput.parse(watchId, parser);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInput.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInput.java
index d9e8a1f075a..e9d5f32630e 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInput.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInput.java
@@ -5,6 +5,7 @@
  */
 package org.elasticsearch.xpack.watcher.input.search;
 
+import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.ParseField;
@@ -12,9 +13,7 @@ import org.elasticsearch.common.ParseFieldMatcher;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentParser;
-import org.elasticsearch.index.query.QueryParseContext;
-import org.elasticsearch.search.aggregations.AggregatorParsers;
-import org.elasticsearch.search.suggest.Suggesters;
+import org.elasticsearch.search.SearchRequestParsers;
 import org.elasticsearch.xpack.watcher.input.Input;
 import org.elasticsearch.xpack.watcher.support.WatcherDateTimeUtils;
 import org.elasticsearch.xpack.watcher.support.search.WatcherSearchTemplateRequest;
@@ -109,9 +108,11 @@ public class SearchInput implements Input {
         return builder;
     }
 
-    public static SearchInput parse(String watchId, XContentParser parser, QueryParseContext context,
-                                    AggregatorParsers aggParsers, Suggesters suggesters)
-            throws IOException {
+    public static SearchInput parse(Logger inputLogger, String watchId, XContentParser parser,
+                                    boolean upgradeInputSource,
+                                    String defaultLegacyScriptLanguage,
+                                    ParseFieldMatcher parseFieldMatcher,
+                                    SearchRequestParsers searchRequestParsers) throws IOException {
         WatcherSearchTemplateRequest request = null;
         Set<String> extract = null;
         TimeValue timeout = null;
@@ -124,7 +125,8 @@ public class SearchInput implements Input {
                 currentFieldName = parser.currentName();
             } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.REQUEST)) {
                 try {
-                    request = WatcherSearchTemplateRequest.fromXContent(parser, ExecutableSearchInput.DEFAULT_SEARCH_TYPE);
+                    request = WatcherSearchTemplateRequest.fromXContent(inputLogger, parser, ExecutableSearchInput.DEFAULT_SEARCH_TYPE,
+                            upgradeInputSource, defaultLegacyScriptLanguage, parseFieldMatcher, searchRequestParsers);
                 } catch (ElasticsearchParseException srpe) {
                     throw new ElasticsearchParseException("could not parse [{}] input for watch [{}]. failed to parse [{}]", srpe, TYPE,
                             watchId, currentFieldName);
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInputFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInputFactory.java
index f521b3b773e..dcadcfc66d9 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInputFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/search/SearchInputFactory.java
@@ -11,12 +11,9 @@ import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentParser;
-import org.elasticsearch.index.query.QueryParseContext;
-import org.elasticsearch.indices.query.IndicesQueriesRegistry;
 import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.script.ScriptSettings;
 import org.elasticsearch.search.SearchRequestParsers;
-import org.elasticsearch.search.aggregations.AggregatorParsers;
-import org.elasticsearch.search.suggest.Suggesters;
 import org.elasticsearch.xpack.security.InternalClient;
 import org.elasticsearch.xpack.watcher.input.InputFactory;
 import org.elasticsearch.xpack.watcher.input.simple.ExecutableSimpleInput;
@@ -25,11 +22,9 @@ import org.elasticsearch.xpack.watcher.support.search.WatcherSearchTemplateServi
 
 import java.io.IOException;
 
-/**
- *
- */
 public class SearchInputFactory extends InputFactory<SearchInput, SearchInput.Result, ExecutableSearchInput> {
 
+    private final Settings settings;
     private final WatcherClientProxy client;
     private final TimeValue defaultTimeout;
     private final SearchRequestParsers searchRequestParsers;
@@ -45,6 +40,7 @@ public class SearchInputFactory extends InputFactory<SearchInput, SearchInput.Re
     public SearchInputFactory(Settings settings, WatcherClientProxy client,
                               SearchRequestParsers searchRequestParsers, ScriptService scriptService) {
         super(Loggers.getLogger(ExecutableSimpleInput.class, settings));
+        this.settings = settings;
         this.parseFieldMatcher = new ParseFieldMatcher(settings);
         this.client = client;
         this.searchRequestParsers = searchRequestParsers;
@@ -58,9 +54,10 @@ public class SearchInputFactory extends InputFactory<SearchInput, SearchInput.Re
     }
 
     @Override
-    public SearchInput parseInput(String watchId, XContentParser parser) throws IOException {
-        QueryParseContext context = new QueryParseContext(searchRequestParsers.queryParsers, parser, parseFieldMatcher);
-        return SearchInput.parse(watchId, parser, context, searchRequestParsers.aggParsers, searchRequestParsers.suggesters);
+    public SearchInput parseInput(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException {
+        String defaultLegacyScriptLanguage = ScriptSettings.getLegacyDefaultLang(settings);
+        return SearchInput.parse(inputLogger, watchId, parser, upgradeInputSource, defaultLegacyScriptLanguage,
+                parseFieldMatcher, searchRequestParsers);
     }
 
     @Override
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputFactory.java
index 4afa085a5dc..ac25f22545f 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputFactory.java
@@ -29,7 +29,7 @@ public class SimpleInputFactory extends InputFactory<SimpleInput, SimpleInput.Re
     }
 
     @Override
-    public SimpleInput parseInput(String watchId, XContentParser parser) throws IOException {
+    public SimpleInput parseInput(String watchId, XContentParser parser, boolean upgradeInputSource) throws IOException {
         return SimpleInput.parse(watchId, parser);
     }
 
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequest.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequest.java
index 88499b34c4b..4f906ce3f66 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequest.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequest.java
@@ -5,6 +5,7 @@
  */
 package org.elasticsearch.xpack.watcher.support.search;
 
+import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.action.search.SearchType;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -15,9 +16,14 @@ import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.xcontent.ToXContent;
 import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.index.query.QueryParseContext;
 import org.elasticsearch.script.Script;
 import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.search.SearchRequestParsers;
+import org.elasticsearch.search.builder.SearchSourceBuilder;
+import org.elasticsearch.xpack.common.text.TextTemplate;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -32,8 +38,6 @@ import java.util.Objects;
  */
 public class WatcherSearchTemplateRequest implements ToXContent {
 
-    private static final String DEFAULT_LANG = "mustache";
-
     private final String[] indices;
     private final String[] types;
     private final SearchType searchType;
@@ -50,12 +54,13 @@ public class WatcherSearchTemplateRequest implements ToXContent {
         this.indicesOptions = indicesOptions;
         // Here we convert a watch search request body into an inline search template,
         // this way if any Watcher related context variables are used, they will get resolved.
-        this.template = new Script(searchSource.utf8ToString(), ScriptService.ScriptType.INLINE, DEFAULT_LANG, null);
+        this.template = new Script(searchSource.utf8ToString(), ScriptService.ScriptType.INLINE, TextTemplate.DEFAULT_TEMPLATE_LANG, null);
         this.searchSource = null;
     }
 
     public WatcherSearchTemplateRequest(String[] indices, String[] types, SearchType searchType, IndicesOptions indicesOptions,
                                         Script template) {
+        assert template == null || TextTemplate.DEFAULT_TEMPLATE_LANG.equals(template.getLang());
         this.indices = indices;
         this.types = types;
         this.searchType = searchType;
@@ -113,7 +118,7 @@ public class WatcherSearchTemplateRequest implements ToXContent {
         if (template != null) {
             return template;
         } else {
-            return new Script(searchSource.utf8ToString(), ScriptService.ScriptType.INLINE, DEFAULT_LANG, null);
+            return new Script(searchSource.utf8ToString(), ScriptService.ScriptType.INLINE, TextTemplate.DEFAULT_TEMPLATE_LANG, null);
         }
     }
 
@@ -159,8 +164,12 @@ public class WatcherSearchTemplateRequest implements ToXContent {
     /**
      * Reads a new watcher search request instance for the specified parser.
      */
-    public static WatcherSearchTemplateRequest fromXContent(XContentParser parser, SearchType searchType)
-            throws IOException {
+    public static WatcherSearchTemplateRequest fromXContent(Logger logger, XContentParser parser,
+                                                            SearchType searchType,
+                                                            boolean upgradeSearchSource,
+                                                            String defaultLegacyScriptLanguage,
+                                                            ParseFieldMatcher parseFieldMatcher,
+                                                            SearchRequestParsers searchRequestParsers) throws IOException {
         List<String> indices = new ArrayList<>();
         List<String> types = new ArrayList<>();
         IndicesOptions indicesOptions = DEFAULT_INDICES_OPTIONS;
@@ -200,6 +209,19 @@ public class WatcherSearchTemplateRequest implements ToXContent {
                     try (XContentBuilder builder = XContentBuilder.builder(parser.contentType().xContent())) {
                         builder.copyCurrentStructure(parser);
                         searchSource = builder.bytes();
+                        if (upgradeSearchSource) {
+                            XContentParser searchSourceParser = XContentHelper.createParser(searchSource);
+                            QueryParseContext context =  new QueryParseContext(defaultLegacyScriptLanguage,
+                                    searchRequestParsers.queryParsers, searchSourceParser, parseFieldMatcher);
+                            try (XContentBuilder upgradeBuilder = XContentBuilder.builder(parser.contentType().xContent())) {
+                                SearchSourceBuilder sourceBuilder = SearchSourceBuilder.fromXContent(context,
+                                        searchRequestParsers.aggParsers, searchRequestParsers.suggesters);
+                                upgradeBuilder.value(sourceBuilder);
+                                searchSource = upgradeBuilder.bytes();
+                            } catch (Exception e) {
+                                logger.warn("Unable to upgrade search source: [" + searchSource.utf8ToString() + "]", e);
+                            }
+                        }
                     }
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, INDICES_OPTIONS_FIELD)) {
                     boolean expandOpen = DEFAULT_INDICES_OPTIONS.expandWildcardsOpen();
@@ -248,7 +270,7 @@ public class WatcherSearchTemplateRequest implements ToXContent {
                     indicesOptions = IndicesOptions.fromOptions(ignoreUnavailable, allowNoIndices, expandOpen, expandClosed,
                             DEFAULT_INDICES_OPTIONS);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, TEMPLATE_FIELD)) {
-                    template = Script.parse(parser, ParseFieldMatcher.STRICT, DEFAULT_LANG);
+                    template = Script.parse(parser, ParseFieldMatcher.STRICT, TextTemplate.DEFAULT_TEMPLATE_LANG);
                 } else {
                     throw new ElasticsearchParseException("could not read search request. unexpected object field [" +
                             currentFieldName + "]");
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateService.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateService.java
index 3250f702ef5..224a948bebc 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateService.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateService.java
@@ -56,7 +56,8 @@ public class WatcherSearchTemplateService extends AbstractComponent {
         if (source.getParams() != null) {
             watcherContextParams.putAll(source.getParams());
         }
-        Script template = new Script(source.getScript(), source.getType(), source.getLang(), watcherContextParams,
+        // Templates are always of lang mustache:
+        Script template = new Script(source.getScript(), source.getType(), "mustache", watcherContextParams,
                 source.getContentType());
         CompiledScript compiledScript = scriptService.compile(template, Watcher.SCRIPT_CONTEXT, Collections.emptyMap());
         return (BytesReference) scriptService.executable(compiledScript, template.getParams()).run();
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformFactory.java
index 0e38bb7bd11..b8b2a41f8d3 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformFactory.java
@@ -28,16 +28,22 @@ public abstract class TransformFactory<T extends Transform, R extends Transform.
 
     /**
      * Parses the given xcontent and creates a concrete transform
+     *
+     * @param watchId                   The id of the watch
+     * @param parser                    The parsing that contains the condition content
+     * @param upgradeTransformSource    Whether to upgrade the source related to transform if in legacy format
+     *                                  Note: depending on the version, only transform implementations that have a
+     *                                  known legacy format will support this option, otherwise this is a noop.
      */
-    public abstract T parseTransform(String watchId, XContentParser parser) throws IOException;
+    public abstract T parseTransform(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException;
 
     /**
      * Creates an executable transform out of the given transform.
      */
     public abstract E createExecutable(T transform);
 
-    public E parseExecutable(String watchId, XContentParser parser) throws IOException {
-        T transform = parseTransform(watchId, parser);
+    public E parseExecutable(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException {
+        T transform = parseTransform(watchId, parser, upgradeTransformSource);
         return createExecutable(transform);
     }
 }
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformRegistry.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformRegistry.java
index 59e7ca07542..17280f0f92e 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformRegistry.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/TransformRegistry.java
@@ -35,7 +35,7 @@ public class TransformRegistry {
         return factories.get(type);
     }
 
-    public ExecutableTransform parse(String watchId, XContentParser parser) throws IOException {
+    public ExecutableTransform parse(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException {
         String type = null;
         XContentParser.Token token;
         ExecutableTransform transform = null;
@@ -43,25 +43,26 @@ public class TransformRegistry {
             if (token == XContentParser.Token.FIELD_NAME) {
                 type = parser.currentName();
             } else if (type != null) {
-                transform = parse(watchId, type, parser);
+                transform = parse(watchId, type, parser, upgradeTransformSource);
             }
         }
         return transform;
     }
 
-    public ExecutableTransform parse(String watchId, String type, XContentParser parser) throws IOException {
+    public ExecutableTransform parse(String watchId, String type, XContentParser parser,
+                                     boolean upgradeTransformSource) throws IOException {
         TransformFactory factory = factories.get(type);
         if (factory == null) {
             throw new ElasticsearchParseException("could not parse transform for watch [{}], unknown transform type [{}]", watchId, type);
         }
-        return factory.parseExecutable(watchId, parser);
+        return factory.parseExecutable(watchId, parser, upgradeTransformSource);
     }
 
-    public Transform parseTransform(String watchId, String type, XContentParser parser) throws IOException {
+    public Transform parseTransform(String watchId, String type, XContentParser parser, boolean upgradeSource) throws IOException {
         TransformFactory factory = factories.get(type);
         if (factory == null) {
             throw new ElasticsearchParseException("could not parse transform for watch [{}], unknown transform type [{}]", watchId, type);
         }
-        return factory.parseTransform(watchId, parser);
+        return factory.parseTransform(watchId, parser, upgradeSource);
     }
 }
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransform.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransform.java
index cabd57cbc78..965c9436b8b 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransform.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransform.java
@@ -71,7 +71,8 @@ public class ChainTransform implements Transform {
         return builder.endArray();
     }
 
-    public static ChainTransform parse(String watchId, XContentParser parser, TransformRegistry transformRegistry) throws IOException {
+    public static ChainTransform parse(String watchId, XContentParser parser, TransformRegistry transformRegistry,
+                                       boolean upgradeSource) throws IOException {
         XContentParser.Token token = parser.currentToken();
         if (token != XContentParser.Token.START_ARRAY) {
             throw new ElasticsearchParseException("could not parse [{}] transform for watch [{}]. expected an array of transform objects," +
@@ -90,7 +91,7 @@ public class ChainTransform implements Transform {
                 if (token == XContentParser.Token.FIELD_NAME) {
                     currentFieldName = parser.currentName();
                 } else {
-                    transforms.add(transformRegistry.parseTransform(watchId, currentFieldName, parser));
+                    transforms.add(transformRegistry.parseTransform(watchId, currentFieldName, parser, upgradeSource));
                 }
             }
         }
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformFactory.java
index 0ec022302d0..285a360a62a 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformFactory.java
@@ -31,8 +31,8 @@ public final class ChainTransformFactory extends TransformFactory<ChainTransform
     }
 
     @Override
-    public ChainTransform parseTransform(String watchId, XContentParser parser) throws IOException {
-        return ChainTransform.parse(watchId, parser, registry);
+    public ChainTransform parseTransform(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException {
+        return ChainTransform.parse(watchId, parser, registry, upgradeTransformSource);
     }
 
     @Override
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransform.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransform.java
index 1ad253b1248..e36762bdda8 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransform.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransform.java
@@ -54,9 +54,15 @@ public class ScriptTransform implements Transform {
         return script.toXContent(builder, params);
     }
 
-    public static ScriptTransform parse(String watchId, XContentParser parser) throws IOException {
+    public static ScriptTransform parse(String watchId, XContentParser parser, boolean upgradeSource,
+                                        String defaultLegacyScriptLanguage) throws IOException {
         try {
-            Script script = Script.parse(parser, ParseFieldMatcher.STRICT);
+            Script script;
+            if (upgradeSource) {
+                script = Script.parse(parser, ParseFieldMatcher.STRICT, defaultLegacyScriptLanguage);
+            } else {
+                script = Script.parse(parser, ParseFieldMatcher.STRICT);
+            }
             return new ScriptTransform(script);
         } catch (ElasticsearchParseException pe) {
             throw new ElasticsearchParseException("could not parse [{}] transform for watch [{}]. failed to parse script", pe, TYPE,
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformFactory.java
index e00e6fec40b..06eec5a20fb 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformFactory.java
@@ -10,20 +10,20 @@ import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.script.ScriptSettings;
 import org.elasticsearch.xpack.watcher.transform.TransformFactory;
 
 import java.io.IOException;
 
-/**
- *
- */
 public class ScriptTransformFactory extends TransformFactory<ScriptTransform, ScriptTransform.Result, ExecutableScriptTransform> {
 
+    private final Settings settings;
     private final ScriptService scriptService;
 
     @Inject
     public ScriptTransformFactory(Settings settings, ScriptService scriptService) {
         super(Loggers.getLogger(ExecutableScriptTransform.class, settings));
+        this.settings = settings;
         this.scriptService = scriptService;
     }
 
@@ -33,8 +33,9 @@ public class ScriptTransformFactory extends TransformFactory<ScriptTransform, Sc
     }
 
     @Override
-    public ScriptTransform parseTransform(String watchId, XContentParser parser) throws IOException {
-        return ScriptTransform.parse(watchId, parser);
+    public ScriptTransform parseTransform(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException {
+        String defaultLegacyScriptLanguage = ScriptSettings.getLegacyDefaultLang(settings);
+        return ScriptTransform.parse(watchId, parser, upgradeTransformSource, defaultLegacyScriptLanguage);
     }
 
     @Override
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransform.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransform.java
index 6bdee9e4fb8..1b690145c86 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransform.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransform.java
@@ -5,6 +5,7 @@
  */
 package org.elasticsearch.xpack.watcher.transform.search;
 
+import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.ParseField;
@@ -12,9 +13,7 @@ import org.elasticsearch.common.ParseFieldMatcher;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentParser;
-import org.elasticsearch.index.query.QueryParseContext;
-import org.elasticsearch.search.aggregations.AggregatorParsers;
-import org.elasticsearch.search.suggest.Suggesters;
+import org.elasticsearch.search.SearchRequestParsers;
 import org.elasticsearch.xpack.watcher.support.WatcherDateTimeUtils;
 import org.elasticsearch.xpack.watcher.support.search.WatcherSearchTemplateRequest;
 import org.elasticsearch.xpack.watcher.transform.Transform;
@@ -92,9 +91,12 @@ public class SearchTransform implements Transform {
         return builder;
     }
 
-    public static SearchTransform parse(String watchId, XContentParser parser, QueryParseContext context,
-                                        AggregatorParsers aggParsers, Suggesters suggesters)
-            throws IOException {
+    public static SearchTransform parse(Logger transformLogger, String watchId,
+                                        XContentParser parser,
+                                        boolean upgradeTransformSource,
+                                        String defaultLegacyScriptLanguage,
+                                        ParseFieldMatcher parseFieldMatcher,
+                                        SearchRequestParsers searchRequestParsers) throws IOException {
         WatcherSearchTemplateRequest request = null;
         TimeValue timeout = null;
         DateTimeZone dynamicNameTimeZone = null;
@@ -106,7 +108,10 @@ public class SearchTransform implements Transform {
                 currentFieldName = parser.currentName();
             } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.REQUEST)) {
                 try {
-                    request = WatcherSearchTemplateRequest.fromXContent(parser, ExecutableSearchTransform.DEFAULT_SEARCH_TYPE);
+                    request = WatcherSearchTemplateRequest.fromXContent(
+                            transformLogger, parser, ExecutableSearchTransform.DEFAULT_SEARCH_TYPE, upgradeTransformSource,
+                            defaultLegacyScriptLanguage, parseFieldMatcher, searchRequestParsers
+                    );
                 } catch (ElasticsearchParseException srpe) {
                     throw new ElasticsearchParseException("could not parse [{}] transform for watch [{}]. failed to parse [{}]", srpe,
                             TYPE, watchId, currentFieldName);
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransformFactory.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransformFactory.java
index 0f4ec07a3ce..056601c087f 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransformFactory.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/transform/search/SearchTransformFactory.java
@@ -13,19 +13,17 @@ import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentParser;
-import org.elasticsearch.index.query.QueryParseContext;
 import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.script.ScriptSettings;
 import org.elasticsearch.search.SearchRequestParsers;
 import org.elasticsearch.xpack.security.InternalClient;
 import org.elasticsearch.xpack.watcher.support.init.proxy.WatcherClientProxy;
 import org.elasticsearch.xpack.watcher.support.search.WatcherSearchTemplateService;
 import org.elasticsearch.xpack.watcher.transform.TransformFactory;
 
-/**
- *
- */
 public class SearchTransformFactory extends TransformFactory<SearchTransform, SearchTransform.Result, ExecutableSearchTransform> {
 
+    private final Settings settings;
     protected final WatcherClientProxy client;
     private final TimeValue defaultTimeout;
     private final SearchRequestParsers searchRequestParsers;
@@ -40,6 +38,7 @@ public class SearchTransformFactory extends TransformFactory<SearchTransform, Se
     public SearchTransformFactory(Settings settings, WatcherClientProxy client,
                                   SearchRequestParsers searchRequestParsers, ScriptService scriptService) {
         super(Loggers.getLogger(ExecutableSearchTransform.class, settings));
+        this.settings = settings;
         this.client = client;
         this.parseFieldMatcher = new ParseFieldMatcher(settings);
         this.searchRequestParsers = searchRequestParsers;
@@ -53,9 +52,10 @@ public class SearchTransformFactory extends TransformFactory<SearchTransform, Se
     }
 
     @Override
-    public SearchTransform parseTransform(String watchId, XContentParser parser) throws IOException {
-        QueryParseContext context = new QueryParseContext(searchRequestParsers.queryParsers, parser, parseFieldMatcher);
-        return SearchTransform.parse(watchId, parser, context, searchRequestParsers.aggParsers, searchRequestParsers.suggesters);
+    public SearchTransform parseTransform(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException {
+        String defaultLegacyScriptLanguage = ScriptSettings.getLegacyDefaultLang(settings);
+        return SearchTransform.parse(transformLogger, watchId, parser, upgradeTransformSource, defaultLegacyScriptLanguage,
+                parseFieldMatcher, searchRequestParsers);
     }
 
     @Override
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/Watch.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/Watch.java
index 16fcdad641f..d47f928ef81 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/Watch.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/Watch.java
@@ -236,11 +236,15 @@ public class Watch implements TriggerEngine.Job, ToXContent {
         }
 
         public Watch parse(String name, boolean includeStatus, BytesReference source) throws IOException {
-            return parse(name, includeStatus, false, source, clock.nowUTC());
+            return parse(name, includeStatus, false, source, clock.nowUTC(), false);
+        }
+
+        public Watch parse(String name, boolean includeStatus, BytesReference source, boolean upgradeSource) throws IOException {
+            return parse(name, includeStatus, false, source, clock.nowUTC(), upgradeSource);
         }
 
         public Watch parse(String name, boolean includeStatus, BytesReference source, DateTime now) throws IOException {
-            return parse(name, includeStatus, false, source, now);
+            return parse(name, includeStatus, false, source, now, false);
         }
 
         /**
@@ -256,10 +260,11 @@ public class Watch implements TriggerEngine.Job, ToXContent {
          * @see org.elasticsearch.xpack.watcher.WatcherService#putWatch(String, BytesReference, TimeValue, boolean)
          */
         public Watch parseWithSecrets(String id, boolean includeStatus, BytesReference source, DateTime now) throws IOException {
-            return parse(id, includeStatus, true, source, now);
+            return parse(id, includeStatus, true, source, now, false);
         }
 
-        private Watch parse(String id, boolean includeStatus, boolean withSecrets, BytesReference source, DateTime now) throws IOException {
+        private Watch parse(String id, boolean includeStatus, boolean withSecrets, BytesReference source, DateTime now,
+                            boolean upgradeSource) throws IOException {
             if (logger.isTraceEnabled()) {
                 logger.trace("parsing watch [{}] ", source.utf8ToString());
             }
@@ -267,7 +272,7 @@ public class Watch implements TriggerEngine.Job, ToXContent {
             try {
                 parser = new WatcherXContentParser(createParser(source), new HaltedClock(now), withSecrets ? cryptoService : null);
                 parser.nextToken();
-                return parse(id, includeStatus, parser);
+                return parse(id, includeStatus, parser, upgradeSource);
             } catch (IOException ioe) {
                 throw ioException("could not parse watch [{}]", ioe, id);
             } finally {
@@ -277,7 +282,7 @@ public class Watch implements TriggerEngine.Job, ToXContent {
             }
         }
 
-        public Watch parse(String id, boolean includeStatus, XContentParser parser) throws IOException {
+        public Watch parse(String id, boolean includeStatus, XContentParser parser, boolean upgradeWatchSource) throws IOException {
             Trigger trigger = null;
             ExecutableInput input = defaultInput;
             ExecutableCondition condition = defaultCondition;
@@ -299,11 +304,11 @@ public class Watch implements TriggerEngine.Job, ToXContent {
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.TRIGGER)) {
                     trigger = triggerService.parseTrigger(id, parser);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.INPUT)) {
-                    input = inputRegistry.parse(id, parser);
+                    input = inputRegistry.parse(id, parser, upgradeWatchSource);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.CONDITION)) {
-                    condition = conditionRegistry.parseExecutable(id, parser);
+                    condition = conditionRegistry.parseExecutable(id, parser, upgradeWatchSource);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.TRANSFORM)) {
-                    transform = transformRegistry.parse(id, parser);
+                    transform = transformRegistry.parse(id, parser, upgradeWatchSource);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.THROTTLE_PERIOD)) {
                     throttlePeriod = timeValueMillis(parser.longValue());
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.THROTTLE_PERIOD_HUMAN)) {
@@ -315,7 +320,7 @@ public class Watch implements TriggerEngine.Job, ToXContent {
                                 pe, id, currentFieldName);
                     }
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.ACTIONS)) {
-                    actions = actionRegistry.parseActions(id, parser);
+                    actions = actionRegistry.parseActions(id, parser, upgradeWatchSource);
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.METADATA)) {
                     metatdata = parser.map();
                 } else if (ParseFieldMatcher.STRICT.match(currentFieldName, Field.STATUS)) {
diff --git a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/WatchStore.java b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/WatchStore.java
index 43305267267..e4b7bdc40fb 100644
--- a/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/WatchStore.java
+++ b/elasticsearch/x-pack/watcher/src/main/java/org/elasticsearch/xpack/watcher/watch/WatchStore.java
@@ -50,8 +50,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
 
 import static org.elasticsearch.xpack.watcher.support.Exceptions.illegalState;
 
-/**
- */
 public class WatchStore extends AbstractComponent {
 
     public static final String INDEX = ".watches";
@@ -310,7 +308,7 @@ public class WatchStore extends AbstractComponent {
                 for (SearchHit hit : response.getHits()) {
                     String id = hit.getId();
                     try {
-                        Watch watch = watchParser.parse(id, true, hit.getSourceRef());
+                        Watch watch = watchParser.parse(id, true, hit.getSourceRef(), true);
                         watch.status().version(hit.version());
                         watch.version(hit.version());
                         watches.put(id, watch);
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionTests.java
index acfd131c8ae..566379fbb57 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/always/AlwaysConditionTests.java
@@ -32,7 +32,7 @@ public class AlwaysConditionTests extends ESTestCase {
         builder.endObject();
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        AlwaysCondition condition = factory.parseCondition("_id", parser);
+        AlwaysCondition condition = factory.parseCondition("_id", parser, false);
         ExecutableAlwaysCondition executable = factory.createExecutable(condition);
         assertTrue(executable.execute(null).met());
     }
@@ -46,7 +46,7 @@ public class AlwaysConditionTests extends ESTestCase {
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
         try {
-            factor.parseCondition("_id", parser);
+            factor.parseCondition("_id", parser, false);
             fail("expected a condition exception trying to parse an invalid condition XContent, ["
                     + AlwaysCondition.TYPE + "] condition should not parse with a body");
         } catch (ElasticsearchParseException e) {
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionTests.java
index 90303c19590..78fab989439 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/CompareConditionTests.java
@@ -177,7 +177,7 @@ public class CompareConditionTests extends ESTestCase {
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         parser.nextToken();
 
-        CompareCondition condition = factory.parseCondition("_id", parser);
+        CompareCondition condition = factory.parseCondition("_id", parser, false);
 
         assertThat(condition, notNullValue());
         assertThat(condition.getPath(), is("key1.key2"));
@@ -195,7 +195,7 @@ public class CompareConditionTests extends ESTestCase {
 
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         try {
-            factory.parseCondition("_id", parser);
+            factory.parseCondition("_id", parser, false);
             fail("Expected ElasticsearchParseException");
         } catch (ElasticsearchParseException e) {
             assertThat(e.getMessage(), containsString("expected an object but found [null] instead"));
@@ -215,7 +215,7 @@ public class CompareConditionTests extends ESTestCase {
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         parser.nextToken();
         try {
-            factory.parseCondition("_id", parser);
+            factory.parseCondition("_id", parser, false);
             fail("Expected ElasticsearchParseException");
         } catch (ElasticsearchParseException e) {
             assertThat(e.getMessage(), containsString("unknown comparison operator [foobar]"));
@@ -236,7 +236,7 @@ public class CompareConditionTests extends ESTestCase {
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         parser.nextToken();
         try {
-            factory.parseCondition("_id", parser);
+            factory.parseCondition("_id", parser, false);
             fail("Expected ElasticsearchParseException");
         } catch (ElasticsearchParseException e) {
             assertThat(e.getMessage(), containsString("must either be a numeric, string, boolean or null value, but found ["));
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionTests.java
index 049110cf939..29c65257f04 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/compare/array/ArrayCompareConditionTests.java
@@ -185,7 +185,7 @@ public class ArrayCompareConditionTests extends ESTestCase {
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         parser.nextToken();
 
-        ArrayCompareCondition condition = factory.parseCondition("_id", parser);
+        ArrayCompareCondition condition = factory.parseCondition("_id", parser, false);
 
         assertThat(condition, notNullValue());
         assertThat(condition.getArrayPath(), is("key1.key2"));
@@ -221,7 +221,7 @@ public class ArrayCompareConditionTests extends ESTestCase {
         expectedException.expect(ElasticsearchParseException.class);
         expectedException.expectMessage("duplicate comparison operator");
 
-        factory.parseCondition("_id", parser);
+        factory.parseCondition("_id", parser, false);
     }
 
     public void testParseContainsUnknownOperator() throws IOException {
@@ -245,7 +245,7 @@ public class ArrayCompareConditionTests extends ESTestCase {
         expectedException.expect(ElasticsearchParseException.class);
         expectedException.expectMessage("unknown comparison operator");
 
-        factory.parseCondition("_id", parser);
+        factory.parseCondition("_id", parser, false);
     }
 
     public void testParseContainsDuplicateValue() throws IOException {
@@ -271,7 +271,7 @@ public class ArrayCompareConditionTests extends ESTestCase {
         expectedException.expect(ElasticsearchParseException.class);
         expectedException.expectMessage("duplicate field \"value\"");
 
-        factory.parseCondition("_id", parser);
+        factory.parseCondition("_id", parser, false);
     }
 
     public void testParseContainsDuplicateQuantifier() throws IOException {
@@ -297,7 +297,7 @@ public class ArrayCompareConditionTests extends ESTestCase {
         expectedException.expect(ElasticsearchParseException.class);
         expectedException.expectMessage("duplicate field \"quantifier\"");
 
-        factory.parseCondition("_id", parser);
+        factory.parseCondition("_id", parser, false);
     }
 
     public void testParseContainsUnknownQuantifier() throws IOException {
@@ -321,7 +321,7 @@ public class ArrayCompareConditionTests extends ESTestCase {
         expectedException.expect(ElasticsearchParseException.class);
         expectedException.expectMessage("unknown comparison quantifier");
 
-        factory.parseCondition("_id", parser);
+        factory.parseCondition("_id", parser, false);
     }
 
     public void testParseContainsUnexpectedFieldInComparisonOperator() throws IOException {
@@ -347,6 +347,6 @@ public class ArrayCompareConditionTests extends ESTestCase {
         expectedException.expect(ElasticsearchParseException.class);
         expectedException.expectMessage("expected a field indicating the comparison value or comparison quantifier");
 
-        factory.parseCondition("_id", parser);
+        factory.parseCondition("_id", parser, false);
     }
 }
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionTests.java
index 6ee71c66988..e536aeda66b 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/never/NeverConditionTests.java
@@ -34,7 +34,7 @@ public class NeverConditionTests extends ESTestCase {
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
 
-        NeverCondition condition = factory.parseCondition("_id", parser);
+        NeverCondition condition = factory.parseCondition("_id", parser, false);
         ExecutableNeverCondition executable = factory.createExecutable(condition);
         assertFalse(executable.execute(null).met());
     }
@@ -48,7 +48,7 @@ public class NeverConditionTests extends ESTestCase {
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
         try {
-            factory.parseCondition("_id", parser);
+            factory.parseCondition("_id", parser, false);
             fail("expected a condition exception trying to parse an invalid condition XContent, ["
                     + AlwaysCondition.TYPE + "] condition should not parse with a body");
         } catch (ElasticsearchParseException e) {
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionTests.java
index b22391f7f8a..61ebf6c465b 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/condition/script/ScriptConditionTests.java
@@ -28,7 +28,6 @@ import org.elasticsearch.script.ScriptService.ScriptType;
 import org.elasticsearch.script.ScriptSettings;
 import org.elasticsearch.search.internal.InternalSearchResponse;
 import org.elasticsearch.test.ESTestCase;
-import org.elasticsearch.xpack.XPackPlugin;
 import org.elasticsearch.xpack.watcher.execution.WatchExecutionContext;
 import org.elasticsearch.xpack.watcher.test.AbstractWatcherIntegrationTestCase;
 import org.elasticsearch.xpack.watcher.watch.Payload;
@@ -120,7 +119,7 @@ public class ScriptConditionTests extends ESTestCase {
 
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        ScriptCondition condition = factory.parseCondition("_watch", parser);
+        ScriptCondition condition = factory.parseCondition("_watch", parser, false);
         ExecutableScriptCondition executable = factory.createExecutable(condition);
 
         SearchResponse response = new SearchResponse(InternalSearchResponse.empty(), "", 3, 3, 500L, new ShardSearchFailure[0]);
@@ -132,7 +131,7 @@ public class ScriptConditionTests extends ESTestCase {
         builder = createConditionContent("return true", null, ScriptType.INLINE);
         parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        condition = factory.parseCondition("_watch", parser);
+        condition = factory.parseCondition("_watch", parser, false);
         executable = factory.createExecutable(condition);
 
         ctx = mockExecutionContext("_name", new Payload.XContent(response));
@@ -147,7 +146,7 @@ public class ScriptConditionTests extends ESTestCase {
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
         try {
-            factory.parseCondition("_id", parser);
+            factory.parseCondition("_id", parser, false);
             fail("expected a condition exception trying to parse an invalid condition XContent");
         } catch (ElasticsearchParseException e) {
             // TODO add these when the test if fixed
@@ -171,7 +170,7 @@ public class ScriptConditionTests extends ESTestCase {
         XContentBuilder builder = createConditionContent(script, "groovy", scriptType);
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        ScriptCondition scriptCondition = conditionParser.parseCondition("_watch", parser);
+        ScriptCondition scriptCondition = conditionParser.parseCondition("_watch", parser, false);
         expectThrows(GeneralScriptException.class,
                 () -> conditionParser.createExecutable(scriptCondition));
     }
@@ -182,7 +181,7 @@ public class ScriptConditionTests extends ESTestCase {
         XContentBuilder builder = createConditionContent(script, "not_a_valid_lang", ScriptType.INLINE);
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        ScriptCondition scriptCondition = conditionParser.parseCondition("_watch", parser);
+        ScriptCondition scriptCondition = conditionParser.parseCondition("_watch", parser, false);
         GeneralScriptException exception = expectThrows(GeneralScriptException.class,
                 () -> conditionParser.createExecutable(scriptCondition));
         assertThat(exception.getMessage(), containsString("script_lang not supported [not_a_valid_lang]]"));
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputTests.java
index b135abe8dd1..1efb0e27a49 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/chain/ChainInputTests.java
@@ -83,7 +83,7 @@ public class ChainInputTests extends ESTestCase {
         // first pass JSON and check for correct inputs
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        ChainInput chainInput = chainInputFactory.parseInput("test", parser);
+        ChainInput chainInput = chainInputFactory.parseInput("test", parser, false);
 
         assertThat(chainInput.getInputs(), hasSize(2));
         assertThat(chainInput.getInputs().get(0).v1(), is("first"));
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/http/HttpInputTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/http/HttpInputTests.java
index 9af85ea6286..668270898f1 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/http/HttpInputTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/http/HttpInputTests.java
@@ -188,7 +188,7 @@ public class HttpInputTests extends ESTestCase {
         BytesReference source = jsonBuilder().value(inputBuilder.build()).bytes();
         XContentParser parser = XContentHelper.createParser(source);
         parser.nextToken();
-        HttpInput result = httpParser.parseInput("_id", parser);
+        HttpInput result = httpParser.parseInput("_id", parser, false);
 
         assertThat(result.type(), equalTo(HttpInput.TYPE));
         assertThat(result.getRequest().scheme(), equalTo(scheme != null ? scheme : Scheme.HTTP)); // http is the default
@@ -226,7 +226,7 @@ public class HttpInputTests extends ESTestCase {
         XContentParser parser = XContentHelper.createParser(builder.bytes());
         parser.nextToken();
         try {
-            httpParser.parseInput("_id", parser);
+            httpParser.parseInput("_id", parser, false);
             fail("Expected IllegalArgumentException");
         } catch (IllegalArgumentException e) {
             assertThat(e.getMessage(), is("unsupported http method [_METHOD]"));
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputTests.java
index 91894a3fdc2..d9ab8dec906 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/input/simple/SimpleInputTests.java
@@ -48,7 +48,7 @@ public class SimpleInputTests extends ESTestCase {
         InputFactory parser = new SimpleInputFactory(Settings.builder().build());
         XContentParser xContentParser = JsonXContent.jsonXContent.createParser(jsonBuilder.bytes());
         xContentParser.nextToken();
-        ExecutableInput input = parser.parseExecutable("_id", xContentParser);
+        ExecutableInput input = parser.parseExecutable("_id", xContentParser, false);
         assertEquals(input.type(), SimpleInput.TYPE);
 
 
@@ -65,7 +65,7 @@ public class SimpleInputTests extends ESTestCase {
         XContentParser xContentParser = JsonXContent.jsonXContent.createParser(jsonBuilder.bytes());
         xContentParser.nextToken();
         try {
-            parser.parseInput("_id", xContentParser);
+            parser.parseInput("_id", xContentParser, false);
             fail("[simple] input parse should fail with an InputException for an empty json object");
         } catch (ElasticsearchParseException e) {
             assertThat(e.getMessage(), containsString("expected an object but found [VALUE_STRING] instead"));
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/WatcherUtilsTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/WatcherUtilsTests.java
index 04611dcea70..64617575d66 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/WatcherUtilsTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/WatcherUtilsTests.java
@@ -124,7 +124,8 @@ public class WatcherUtilsTests extends ESTestCase {
         request.toXContent(builder, ToXContent.EMPTY_PARAMS);
         XContentParser parser = XContentHelper.createParser(builder.bytes());
         assertThat(parser.nextToken(), equalTo(XContentParser.Token.START_OBJECT));
-        WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(parser, DEFAULT_SEARCH_TYPE);
+        WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(logger, parser, DEFAULT_SEARCH_TYPE,
+                false, null, null, null);
 
         assertThat(result.getIndices(), arrayContainingInAnyOrder(expectedIndices != null ? expectedIndices : new String[0]));
         assertThat(result.getTypes(), arrayContainingInAnyOrder(expectedTypes != null ? expectedTypes : new String[0]));
@@ -213,7 +214,8 @@ public class WatcherUtilsTests extends ESTestCase {
 
         XContentParser parser = XContentHelper.createParser(builder.bytes());
         assertThat(parser.nextToken(), equalTo(XContentParser.Token.START_OBJECT));
-        WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(parser, DEFAULT_SEARCH_TYPE);
+        WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(logger, parser, DEFAULT_SEARCH_TYPE,
+                false, null, null, null);
 
         assertThat(result.getIndices(), arrayContainingInAnyOrder(indices));
         assertThat(result.getTypes(), arrayContainingInAnyOrder(types));
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequestTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequestTests.java
index 5efa5996d0b..4005a93f8bc 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequestTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/support/search/WatcherSearchTemplateRequestTests.java
@@ -6,15 +6,23 @@
 package org.elasticsearch.xpack.watcher.support.search;
 
 import org.elasticsearch.action.search.SearchType;
+import org.elasticsearch.common.ParseFieldMatcher;
 import org.elasticsearch.common.bytes.BytesArray;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.common.xcontent.support.XContentMapValues;
+import org.elasticsearch.search.SearchModule;
+import org.elasticsearch.search.SearchRequestParsers;
 import org.elasticsearch.test.ESTestCase;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.Map;
 
 import static java.util.Collections.singletonMap;
+import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
 import static org.hamcrest.Matchers.equalTo;
 
 public class WatcherSearchTemplateRequestTests extends ESTestCase {
@@ -33,7 +41,8 @@ public class WatcherSearchTemplateRequestTests extends ESTestCase {
         try (XContentParser parser = XContentHelper.createParser(new BytesArray(source))) {
             parser.nextToken();
 
-            WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(parser, randomFrom(SearchType.values()));
+            WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(
+                    logger, parser, randomFrom(SearchType.values()), false, null, null, null);
             assertNotNull(result.getTemplate());
             assertThat(result.getTemplate().getScript(), equalTo(expectedScript));
             assertThat(result.getTemplate().getLang(), equalTo(expectedLang));
@@ -42,4 +51,53 @@ public class WatcherSearchTemplateRequestTests extends ESTestCase {
             fail("Failed to parse watch search request: " + e.getMessage());
         }
     }
+
+    public void testUpgradeSearchSource() throws IOException {
+        XContentBuilder contentBuilder = jsonBuilder();
+        contentBuilder.startObject();
+        contentBuilder.startObject("body");
+
+        contentBuilder.startObject("query");
+        contentBuilder.startObject("script");
+        contentBuilder.startObject("script");
+        contentBuilder.field("inline", "return true");
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+
+        contentBuilder.startObject("aggregations");
+        contentBuilder.startObject("avg_grade");
+        contentBuilder.startObject("avg");
+        contentBuilder.startObject("script");
+        contentBuilder.field("inline", "1 + 1");
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+        contentBuilder.startObject("another_avg");
+        contentBuilder.startObject("avg");
+        contentBuilder.startObject("script");
+        contentBuilder.field("inline", "1 + 2");
+        contentBuilder.field("lang", "javascript");
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+
+        contentBuilder.endObject();
+        contentBuilder.endObject();
+        XContentParser parser = XContentHelper.createParser(contentBuilder.bytes());
+        parser.nextToken();
+
+        SearchRequestParsers searchRequestParsers = new SearchModule(Settings.EMPTY, false, Collections.emptyList())
+                .getSearchRequestParsers();
+        WatcherSearchTemplateRequest result = WatcherSearchTemplateRequest.fromXContent(
+                logger, parser, SearchType.DEFAULT, true, "your_legacy_lang", ParseFieldMatcher.STRICT, searchRequestParsers);
+        Map<String, Object> parsedResult = XContentHelper.convertToMap(result.getSearchSource(), true).v2();
+        // after upgrading the language must be equal to legacy language, because no language was defined explicitly in these scripts:
+        assertThat(XContentMapValues.extractValue("query.script.script.lang", parsedResult), equalTo("your_legacy_lang"));
+        assertThat(XContentMapValues.extractValue("aggregations.avg_grade.avg.script.lang", parsedResult), equalTo("your_legacy_lang"));
+        // after upgrading the language must remain javascript here, because that has been explicitly defined in the script:
+        assertThat(XContentMapValues.extractValue("aggregations.another_avg.avg.script.lang", parsedResult), equalTo("javascript"));
+    }
+
 }
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchInputTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchInputTests.java
index e95db798ee1..46c689240b7 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchInputTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchInputTests.java
@@ -22,7 +22,6 @@ import org.elasticsearch.search.SearchRequestParsers;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.test.ESIntegTestCase.ClusterScope;
-import org.elasticsearch.xpack.XPackPlugin;
 import org.elasticsearch.xpack.watcher.actions.ExecutableActions;
 import org.elasticsearch.xpack.watcher.condition.always.ExecutableAlwaysCondition;
 import org.elasticsearch.xpack.watcher.execution.TriggeredExecutionContext;
@@ -152,7 +151,7 @@ public class SearchInputTests extends ESIntegTestCase {
         SearchInputFactory factory = new SearchInputFactory(Settings.EMPTY, WatcherClientProxy.of(client()),
                                                             searchParsers, scriptService());
 
-        SearchInput searchInput = factory.parseInput("_id", parser);
+        SearchInput searchInput = factory.parseInput("_id", parser, false);
         assertEquals(SearchInput.TYPE, searchInput.type());
         assertThat(searchInput.getTimeout(), equalTo(timeout));
     }
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchTransformTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchTransformTests.java
index d664daa1614..0a43d05fa66 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchTransformTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/SearchTransformTests.java
@@ -217,7 +217,7 @@ public class SearchTransformTests extends ESIntegTestCase {
         SearchRequestParsers searchRequestParsers = internalCluster().getInstance(SearchRequestParsers.class);
         SearchTransformFactory transformFactory = new SearchTransformFactory(Settings.EMPTY, WatcherClientProxy.of(client()),
                                                                              searchRequestParsers, scriptService());
-        ExecutableSearchTransform executable = transformFactory.parseExecutable("_id", parser);
+        ExecutableSearchTransform executable = transformFactory.parseExecutable("_id", parser, false);
 
         assertThat(executable, notNullValue());
         assertThat(executable.type(), is(SearchTransform.TYPE));
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/WatcherBackwardsCompatibilityTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/WatcherBackwardsCompatibilityTests.java
index 00c54c27e76..4dc2c4b4cad 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/WatcherBackwardsCompatibilityTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/test/integration/WatcherBackwardsCompatibilityTests.java
@@ -12,6 +12,8 @@ import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.env.Environment;
+import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.script.MockScriptPlugin;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.xpack.watcher.support.xcontent.ObjectPath;
 import org.elasticsearch.xpack.watcher.test.AbstractWatcherIntegrationTestCase;
@@ -21,7 +23,10 @@ import org.elasticsearch.xpack.watcher.watch.WatchStore;
 import java.io.InputStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.Collections;
+import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
@@ -44,6 +49,13 @@ public class WatcherBackwardsCompatibilityTests extends AbstractWatcherIntegrati
         return false;
     }
 
+    @Override
+    protected List<Class<? extends Plugin>> pluginTypes() {
+        List<Class<? extends Plugin>> plugins = super.pluginTypes();
+        plugins.add(FoolMeScriptLang.class);
+        return plugins;
+    }
+
     public void testWatchLoadedSuccessfullyAfterUpgrade() throws Exception {
         // setup node
         Path dataDir = createTempDir();
@@ -86,10 +98,32 @@ public class WatcherBackwardsCompatibilityTests extends AbstractWatcherIntegrati
         assertThat(getWatchResponse.isFound(), is(true));
         Map<String, Object> watchSourceAsMap = getWatchResponse.getSource().getAsMap();
         assertThat(ObjectPath.eval("trigger.schedule.interval", watchSourceAsMap), equalTo("99w"));
-        assertThat(ObjectPath.eval("input.search.request.body.query.bool.filter.1.range.date.lte", watchSourceAsMap),
+        assertThat(ObjectPath.eval("input.search.request.body.query.bool.filter.1.range.date.to", watchSourceAsMap),
                 equalTo("{{ctx.trigger.scheduled_time}}"));
         assertThat(ObjectPath.eval("actions.log_error.logging.text", watchSourceAsMap),
                 equalTo("Found {{ctx.payload.hits.total}} errors in the logs"));
+
+        // Check that all scripts have been upgraded, so that the language has been set to groovy (legacy language default):
+        assertThat(ObjectPath.eval("input.search.request.body.query.bool.filter.2.script.script.lang", watchSourceAsMap),
+                equalTo("groovy"));
+        assertThat(ObjectPath.eval("input.search.request.body.aggregations.avg_grade.avg.script.lang", watchSourceAsMap),
+                equalTo("groovy"));
+        assertThat(ObjectPath.eval("condition.script.lang", watchSourceAsMap), equalTo("groovy"));
+    }
+
+    // Fool the script service that this is the groovy script language, so that we can just load the watch upon startup
+    // and verify that the lang options on scripts have been set.
+    public static class FoolMeScriptLang extends MockScriptPlugin{
+
+        @Override
+        protected Map<String, Function<Map<String, Object>, Object>> pluginScripts() {
+            return Collections.singletonMap("ctx.payload.hits.total > 0", (vars) -> true);
+        }
+
+        @Override
+        public String pluginScriptLang() {
+            return "groovy";
+        }
     }
 
 }
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformTests.java
index 382fd4a6f15..560a8585bc8 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/chain/ChainTransformTests.java
@@ -126,7 +126,7 @@ public class ChainTransformTests extends ESTestCase {
 
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         parser.nextToken();
-        ExecutableChainTransform executable = transformParser.parseExecutable("_id", parser);
+        ExecutableChainTransform executable = transformParser.parseExecutable("_id", parser, false);
         assertThat(executable, notNullValue());
         assertThat(executable.transform().getTransforms(), notNullValue());
         assertThat(executable.transform().getTransforms(), hasSize(4));
@@ -204,7 +204,7 @@ public class ChainTransformTests extends ESTestCase {
             }
 
             @Override
-            public Transform parseTransform(String watchId, XContentParser parser) throws IOException {
+            public Transform parseTransform(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException {
                 if (parser.currentToken() == XContentParser.Token.VALUE_STRING) {
                     return new Transform(parser.text());
                 }
@@ -273,7 +273,7 @@ public class ChainTransformTests extends ESTestCase {
             }
 
             @Override
-            public Transform parseTransform(String watchId, XContentParser parser) throws IOException {
+            public Transform parseTransform(String watchId, XContentParser parser, boolean upgradeTransformSource) throws IOException {
                 assert parser.currentToken() == XContentParser.Token.START_OBJECT;
                 XContentParser.Token token = parser.nextToken();
                 assert token == XContentParser.Token.END_OBJECT;
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformTests.java
index f9203f4bf27..6433d0f5278 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/transform/script/ScriptTransformTests.java
@@ -152,7 +152,7 @@ public class ScriptTransformTests extends ESTestCase {
 
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         parser.nextToken();
-        ExecutableScriptTransform transform = new ScriptTransformFactory(Settings.EMPTY, service).parseExecutable("_id", parser);
+        ExecutableScriptTransform transform = new ScriptTransformFactory(Settings.EMPTY, service).parseExecutable("_id", parser, false);
         Script script = new Script("_script", type, "_lang", singletonMap("key", "value"));
         assertThat(transform.transform().getScript(), equalTo(script));
     }
@@ -163,7 +163,7 @@ public class ScriptTransformTests extends ESTestCase {
 
         XContentParser parser = JsonXContent.jsonXContent.createParser(builder.bytes());
         parser.nextToken();
-        ExecutableScriptTransform transform = new ScriptTransformFactory(Settings.EMPTY, service).parseExecutable("_id", parser);
+        ExecutableScriptTransform transform = new ScriptTransformFactory(Settings.EMPTY, service).parseExecutable("_id", parser, false);
         assertThat(transform.transform().getScript(), equalTo(new Script("_script")));
     }
 
@@ -189,7 +189,7 @@ public class ScriptTransformTests extends ESTestCase {
 
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        ScriptTransform scriptTransform = transformFactory.parseTransform("_watch", parser);
+        ScriptTransform scriptTransform = transformFactory.parseTransform("_watch", parser, false);
         try {
             transformFactory.createExecutable(scriptTransform);
             fail("expected a transform validation exception trying to create an executable with a bad or missing script");
@@ -212,7 +212,7 @@ public class ScriptTransformTests extends ESTestCase {
 
         XContentParser parser = XContentFactory.xContent(builder.bytes()).createParser(builder.bytes());
         parser.nextToken();
-        ScriptTransform scriptCondition = transformFactory.parseTransform("_watch", parser);
+        ScriptTransform scriptCondition = transformFactory.parseTransform("_watch", parser, false);
         try {
             transformFactory.createExecutable(scriptCondition);
             fail("expected a transform validation exception trying to create an executable with an invalid language");
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchStoreTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchStoreTests.java
index 44221316b23..06ab49cd227 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchStoreTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchStoreTests.java
@@ -67,8 +67,6 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyZeroInteractions;
 import static org.mockito.Mockito.when;
 
-/**
- */
 public class WatchStoreTests extends ESTestCase {
     private WatchStore watchStore;
     private WatcherClientProxy clientProxy;
@@ -221,10 +219,10 @@ public class WatchStoreTests extends ESTestCase {
         when(watch3.status()).thenReturn(status);
         Watch watch4 = mock(Watch.class);
         when(watch4.status()).thenReturn(status);
-        when(parser.parse("_id1", true, source)).thenReturn(watch1);
-        when(parser.parse("_id2", true, source)).thenReturn(watch2);
-        when(parser.parse("_id3", true, source)).thenReturn(watch3);
-        when(parser.parse("_id4", true, source)).thenReturn(watch4);
+        when(parser.parse("_id1", true, source, true)).thenReturn(watch1);
+        when(parser.parse("_id2", true, source, true)).thenReturn(watch2);
+        when(parser.parse("_id3", true, source, true)).thenReturn(watch3);
+        when(parser.parse("_id4", true, source, true)).thenReturn(watch4);
 
         when(clientProxy.clearScroll(anyString())).thenReturn(new ClearScrollResponse(true, 0));
 
@@ -303,7 +301,7 @@ public class WatchStoreTests extends ESTestCase {
             };
             when(watch.transform()).thenReturn(randomFrom(testTransform, null));
 
-            when(parser.parse("_id" + i, true, source)).thenReturn(watch);
+            when(parser.parse("_id" + i, true, source, true)).thenReturn(watch);
         }
 
         SearchResponse searchResponse = mockSearchResponse(1, 1, hitCount, hits.toArray(new InternalSearchHit[] {}));
@@ -365,7 +363,7 @@ public class WatchStoreTests extends ESTestCase {
         Watch watch = mock(Watch.class);
         WatchStatus status = mock(WatchStatus.class);
         when(watch.status()).thenReturn(status);
-        when(parser.parse("_id1", true, source)).thenReturn(watch);
+        when(parser.parse("_id1", true, source, true)).thenReturn(watch);
 
         when(clientProxy.clearScroll(anyString())).thenReturn(new ClearScrollResponse(true, 0));
 
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchTests.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchTests.java
index b778264365a..11106d22a04 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchTests.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/xpack/watcher/watch/WatchTests.java
@@ -7,6 +7,7 @@ package org.elasticsearch.xpack.watcher.watch;
 
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.action.search.SearchRequest;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.logging.Loggers;
 import org.elasticsearch.common.settings.Settings;
@@ -15,10 +16,12 @@ import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.index.query.MatchAllQueryBuilder;
 import org.elasticsearch.index.query.QueryParser;
+import org.elasticsearch.index.query.ScriptQueryBuilder;
 import org.elasticsearch.indices.query.IndicesQueriesRegistry;
 import org.elasticsearch.license.XPackLicenseState;
 import org.elasticsearch.script.Script;
 import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.script.ScriptSettings;
 import org.elasticsearch.search.SearchRequestParsers;
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.xpack.common.http.HttpClient;
@@ -81,6 +84,7 @@ import org.elasticsearch.xpack.watcher.input.simple.ExecutableSimpleInput;
 import org.elasticsearch.xpack.watcher.input.simple.SimpleInput;
 import org.elasticsearch.xpack.watcher.input.simple.SimpleInputFactory;
 import org.elasticsearch.xpack.watcher.support.init.proxy.WatcherClientProxy;
+import org.elasticsearch.xpack.watcher.support.search.WatcherSearchTemplateRequest;
 import org.elasticsearch.xpack.watcher.support.search.WatcherSearchTemplateService;
 import org.elasticsearch.xpack.watcher.test.WatcherTestUtils;
 import org.elasticsearch.xpack.watcher.transform.ExecutableTransform;
@@ -181,7 +185,7 @@ public class WatchTests extends ESTestCase {
         TriggerService triggerService = new TriggerService(Settings.EMPTY, singleton(triggerEngine));
 
         ExecutableInput input = randomInput();
-        InputRegistry inputRegistry = registry(input);
+        InputRegistry inputRegistry = registry(input.type());
 
         ExecutableCondition condition = randomCondition();
         ConditionRegistry conditionRegistry = conditionRegistry();
@@ -230,7 +234,7 @@ public class WatchTests extends ESTestCase {
         TriggerService triggerService = new TriggerService(Settings.EMPTY, singleton(triggerEngine));
         ConditionRegistry conditionRegistry = conditionRegistry();
         ExecutableInput input = randomInput();
-        InputRegistry inputRegistry = registry(input);
+        InputRegistry inputRegistry = registry(input.type());
 
         TransformRegistry transformRegistry = transformRegistry();
 
@@ -259,7 +263,7 @@ public class WatchTests extends ESTestCase {
         TriggerService triggerService = new TriggerService(Settings.EMPTY, singleton(triggerEngine));
 
         ConditionRegistry conditionRegistry = conditionRegistry();
-        InputRegistry inputRegistry = registry(new ExecutableNoneInput(logger));
+        InputRegistry inputRegistry = registry(new ExecutableNoneInput(logger).type());
         TransformRegistry transformRegistry = transformRegistry();
         ExecutableActions actions =  new ExecutableActions(Collections.emptyList());
         ActionRegistry actionRegistry = registry(actions, conditionRegistry, transformRegistry);
@@ -282,6 +286,84 @@ public class WatchTests extends ESTestCase {
         assertThat(watch.actions().count(), is(0));
     }
 
+    public void testParseWatch_verifyScriptLangDefault() throws Exception {
+        ScheduleRegistry scheduleRegistry = registry(new IntervalSchedule(new IntervalSchedule.Interval(1,
+                IntervalSchedule.Interval.Unit.SECONDS)));
+        TriggerEngine triggerEngine = new ParseOnlyScheduleTriggerEngine(Settings.EMPTY, scheduleRegistry, SystemClock.INSTANCE);
+        TriggerService triggerService = new TriggerService(Settings.EMPTY, singleton(triggerEngine));
+
+        ConditionRegistry conditionRegistry = conditionRegistry();
+        InputRegistry inputRegistry = registry(SearchInput.TYPE);
+        TransformRegistry transformRegistry = transformRegistry();
+        ExecutableActions actions =  new ExecutableActions(Collections.emptyList());
+        ActionRegistry actionRegistry = registry(actions, conditionRegistry, transformRegistry);
+        Watch.Parser watchParser = new Watch.Parser(settings, conditionRegistry, triggerService, transformRegistry, actionRegistry,
+                inputRegistry, null, SystemClock.INSTANCE);
+
+        IndicesQueriesRegistry queryRegistry = new IndicesQueriesRegistry();
+        QueryParser<MatchAllQueryBuilder> queryParser1 = MatchAllQueryBuilder::fromXContent;
+        queryRegistry.register(queryParser1, MatchAllQueryBuilder.NAME);
+        QueryParser<ScriptQueryBuilder> queryParser2 = ScriptQueryBuilder::fromXContent;
+        queryRegistry.register(queryParser2, ScriptQueryBuilder.NAME);
+        SearchRequestParsers searchParsers = new SearchRequestParsers(queryRegistry, null,  null);
+        WatcherSearchTemplateService searchTemplateService = new WatcherSearchTemplateService(settings, scriptService, searchParsers);
+
+        XContentBuilder builder = XContentFactory.jsonBuilder();
+        builder.startObject();
+
+        builder.startObject("trigger");
+        builder.startObject("schedule");
+        builder.field("interval", "99w");
+        builder.endObject();
+        builder.endObject();
+
+        builder.startObject("input");
+        builder.startObject("search");
+        builder.startObject("request");
+        builder.startObject("body");
+        builder.startObject("query");
+        builder.startObject("script");
+        if (randomBoolean()) {
+            builder.field("script", "return true");
+        } else {
+            builder.startObject("script");
+            builder.field("inline", "return true");
+            builder.endObject();
+        }
+        builder.endObject();
+        builder.endObject();
+        builder.endObject();
+        builder.endObject();
+        builder.endObject();
+        builder.endObject();
+
+        builder.startObject("condition");
+        if (randomBoolean()) {
+            builder.field("script", "return true");
+        } else {
+            builder.startObject("script");
+            builder.field("inline", "return true");
+            builder.endObject();
+        }
+        builder.endObject();
+
+        builder.endObject();
+
+        // parse in default mode:
+        Watch watch = watchParser.parse("_id", false, builder.bytes());
+        assertThat(((ScriptCondition) watch.condition().condition()).getScript().getLang(), equalTo(Script.DEFAULT_SCRIPT_LANG));
+        WatcherSearchTemplateRequest request = ((SearchInput) watch.input().input()).getRequest();
+        SearchRequest searchRequest = searchTemplateService.toSearchRequest(request);
+        assertThat(((ScriptQueryBuilder) searchRequest.source().query()).script().getLang(), equalTo(Script.DEFAULT_SCRIPT_LANG));
+
+        // parse in legacy mode:
+        watch = watchParser.parse("_id", false, builder.bytes(), true);
+        assertThat(((ScriptCondition) watch.condition().condition()).getScript().getLang(), equalTo("groovy"));
+        request = ((SearchInput) watch.input().input()).getRequest();
+        searchRequest = searchTemplateService.toSearchRequest(request);
+        assertThat(((ScriptQueryBuilder) searchRequest.source().query()).script().getLang(), equalTo("groovy"));
+    }
+
     private static Schedule randomSchedule() {
         String type = randomFrom(CronSchedule.TYPE, HourlySchedule.TYPE, DailySchedule.TYPE, WeeklySchedule.TYPE, MonthlySchedule.TYPE,
                 YearlySchedule.TYPE, IntervalSchedule.TYPE);
@@ -346,13 +428,15 @@ public class WatchTests extends ESTestCase {
         }
     }
 
-    private InputRegistry registry(ExecutableInput input) {
+    private InputRegistry registry(String inputType) {
         Map<String, InputFactory> parsers = new HashMap<>();
-        switch (input.type()) {
+        switch (inputType) {
             case SearchInput.TYPE:
                 IndicesQueriesRegistry queryRegistry = new IndicesQueriesRegistry();
-                QueryParser<MatchAllQueryBuilder> queryParser = MatchAllQueryBuilder::fromXContent;
-                queryRegistry.register(queryParser, MatchAllQueryBuilder.NAME);
+                QueryParser<MatchAllQueryBuilder> queryParser1 = MatchAllQueryBuilder::fromXContent;
+                queryRegistry.register(queryParser1, MatchAllQueryBuilder.NAME);
+                QueryParser<ScriptQueryBuilder> queryParser2 = ScriptQueryBuilder::fromXContent;
+                queryRegistry.register(queryParser2, ScriptQueryBuilder.NAME);
                 SearchRequestParsers searchParsers = new SearchRequestParsers(queryRegistry, null,  null);
                 parsers.put(SearchInput.TYPE, new SearchInputFactory(settings, client, searchParsers, scriptService));
                 return new InputRegistry(Settings.EMPTY, parsers);
diff --git a/elasticsearch/x-pack/watcher/src/test/resources/bwc_indices/bwc_index_2_3_5.zip b/elasticsearch/x-pack/watcher/src/test/resources/bwc_indices/bwc_index_2_3_5.zip
index 1e0bf8f00d2..5d074c0ab5d 100644
Binary files a/elasticsearch/x-pack/watcher/src/test/resources/bwc_indices/bwc_index_2_3_5.zip and b/elasticsearch/x-pack/watcher/src/test/resources/bwc_indices/bwc_index_2_3_5.zip differ