diff --git a/server/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java b/server/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java
index f9b9de97715ed..ea1ffdb7c019f 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java
@@ -88,6 +88,42 @@ public enum Mode {
         true
     );
 
+    private static final SourceFieldMapper DEFAULT_DISABLED = new SourceFieldMapper(
+        Mode.DISABLED,
+        Explicit.IMPLICIT_TRUE,
+        Strings.EMPTY_ARRAY,
+        Strings.EMPTY_ARRAY,
+        null,
+        true
+    );
+
+    private static final SourceFieldMapper DEFAULT_DISABLED_NO_RECOVERY_SOURCE = new SourceFieldMapper(
+        Mode.DISABLED,
+        Explicit.IMPLICIT_TRUE,
+        Strings.EMPTY_ARRAY,
+        Strings.EMPTY_ARRAY,
+        null,
+        false
+    );
+
+    private static final SourceFieldMapper DEFAULT_SYNTHETIC = new SourceFieldMapper(
+        Mode.SYNTHETIC,
+        Explicit.IMPLICIT_TRUE,
+        Strings.EMPTY_ARRAY,
+        Strings.EMPTY_ARRAY,
+        null,
+        true
+    );
+
+    private static final SourceFieldMapper DEFAULT_SYNTHETIC_NO_RECOVERY_SOURCE = new SourceFieldMapper(
+        Mode.SYNTHETIC,
+        Explicit.IMPLICIT_TRUE,
+        Strings.EMPTY_ARRAY,
+        Strings.EMPTY_ARRAY,
+        null,
+        false
+    );
+
     private static final SourceFieldMapper DEFAULT_NO_RECOVERY_SOURCE = new SourceFieldMapper(
         null,
         Explicit.IMPLICIT_TRUE,
@@ -297,7 +333,7 @@ public SourceFieldMapper build() {
                 ? INDEX_MAPPER_SOURCE_MODE_SETTING.get(settings)
                 : mode.get();
             if (isDefault(sourceMode)) {
-                return resolveSourceMode(indexMode, sourceMode, enableRecoverySource);
+                return resolveSourceMode(indexMode, sourceMode == null ? Mode.STORED : sourceMode, enableRecoverySource);
 
             }
             if (supportsNonDefaultParameterValues == false) {
@@ -340,25 +376,39 @@ public SourceFieldMapper build() {
     }
 
     private static SourceFieldMapper resolveSourceMode(final IndexMode indexMode, final Mode sourceMode, boolean enableRecoverySource) {
-        if (indexMode == IndexMode.STANDARD) {
-            return enableRecoverySource ? DEFAULT : DEFAULT_NO_RECOVERY_SOURCE;
+        switch (indexMode) {
+            case STANDARD:
+                switch (sourceMode) {
+                    case SYNTHETIC:
+                        return enableRecoverySource ? DEFAULT_SYNTHETIC : DEFAULT_SYNTHETIC_NO_RECOVERY_SOURCE;
+                    case STORED:
+                        return enableRecoverySource ? DEFAULT : DEFAULT_NO_RECOVERY_SOURCE;
+                    case DISABLED:
+                        return enableRecoverySource ? DEFAULT_DISABLED : DEFAULT_DISABLED_NO_RECOVERY_SOURCE;
+                    default:
+                        throw new IllegalArgumentException("Unsupported source mode: " + sourceMode);
+                }
+            case TIME_SERIES:
+            case LOGSDB:
+                switch (sourceMode) {
+                    case SYNTHETIC:
+                        return enableRecoverySource
+                            ? (indexMode == IndexMode.TIME_SERIES ? TSDB_DEFAULT : LOGSDB_DEFAULT)
+                            : (indexMode == IndexMode.TIME_SERIES ? TSDB_DEFAULT_NO_RECOVERY_SOURCE : LOGSDB_DEFAULT_NO_RECOVERY_SOURCE);
+                    case STORED:
+                        return enableRecoverySource
+                            ? (indexMode == IndexMode.TIME_SERIES ? TSDB_DEFAULT_STORED : LOGSDB_DEFAULT_STORED)
+                            : (indexMode == IndexMode.TIME_SERIES
+                                ? TSDB_DEFAULT_NO_RECOVERY_SOURCE_STORED
+                                : LOGSDB_DEFAULT_NO_RECOVERY_SOURCE_STORED);
+                    case DISABLED:
+                        throw new IllegalArgumentException("_source can not be disabled in index using [" + indexMode + "] index mode");
+                    default:
+                        throw new IllegalArgumentException("Unsupported source mode: " + sourceMode);
+                }
+            default:
+                throw new IllegalArgumentException("Unsupported index mode: " + indexMode);
         }
-        final SourceFieldMapper syntheticWithoutRecoverySource = indexMode == IndexMode.TIME_SERIES
-            ? TSDB_DEFAULT_NO_RECOVERY_SOURCE
-            : LOGSDB_DEFAULT_NO_RECOVERY_SOURCE;
-        final SourceFieldMapper syntheticWithRecoverySource = indexMode == IndexMode.TIME_SERIES ? TSDB_DEFAULT : LOGSDB_DEFAULT;
-        final SourceFieldMapper storedWithoutRecoverySource = indexMode == IndexMode.TIME_SERIES
-            ? TSDB_DEFAULT_NO_RECOVERY_SOURCE_STORED
-            : LOGSDB_DEFAULT_NO_RECOVERY_SOURCE_STORED;
-        final SourceFieldMapper storedWithRecoverySource = indexMode == IndexMode.TIME_SERIES ? TSDB_DEFAULT_STORED : LOGSDB_DEFAULT_STORED;
-
-        return switch (sourceMode) {
-            case SYNTHETIC -> enableRecoverySource ? syntheticWithRecoverySource : syntheticWithoutRecoverySource;
-            case STORED -> enableRecoverySource ? storedWithRecoverySource : storedWithoutRecoverySource;
-            case DISABLED -> throw new IllegalArgumentException(
-                "_source can not be disabled in index using [" + indexMode + "] index mode"
-            );
-        };
     }
 
     public static final TypeParser PARSER = new ConfigurableTypeParser(c -> {
@@ -371,7 +421,7 @@ private static SourceFieldMapper resolveSourceMode(final IndexMode indexMode, fi
                 return enableRecoverySource ? TSDB_LEGACY_DEFAULT : TSDB_LEGACY_DEFAULT_NO_RECOVERY_SOURCE;
             }
         }
-        return resolveSourceMode(indexMode, settingSourceMode, enableRecoverySource);
+        return resolveSourceMode(indexMode, settingSourceMode == null ? Mode.STORED : settingSourceMode, enableRecoverySource);
     },
         c -> new Builder(
             c.getIndexSettings().getMode(),
@@ -541,4 +591,12 @@ public SourceLoader newSourceLoader(Mapping mapping, SourceFieldMetrics metrics)
     public boolean isSynthetic() {
         return mode == Mode.SYNTHETIC;
     }
+
+    public boolean isDisabled() {
+        return mode == Mode.DISABLED;
+    }
+
+    public boolean isStored() {
+        return mode == null || mode == Mode.STORED;
+    }
 }
diff --git a/server/src/test/java/org/elasticsearch/index/mapper/SourceFieldMapperTests.java b/server/src/test/java/org/elasticsearch/index/mapper/SourceFieldMapperTests.java
index 2f417e688cb97..df6d9380fd141 100644
--- a/server/src/test/java/org/elasticsearch/index/mapper/SourceFieldMapperTests.java
+++ b/server/src/test/java/org/elasticsearch/index/mapper/SourceFieldMapperTests.java
@@ -443,6 +443,167 @@ public void testRecoverySourceWithLogs() throws IOException {
         }
     }
 
+    public void testStandardIndexModeWithSourceModeSetting() throws IOException {
+        // Test for IndexMode.STANDARD
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.STANDARD.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.SYNTHETIC)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isSynthetic());
+        }
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.STANDARD.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.STORED)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            final DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isStored());
+        }
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.STANDARD.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.DISABLED)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            final DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isDisabled());
+        }
+
+        // Test for IndexMode.LOGSDB
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.LOGSDB.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.SYNTHETIC)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isSynthetic());
+        }
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.LOGSDB.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.STORED)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            final DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isStored());
+        }
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.LOGSDB.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.DISABLED)
+                .build();
+            var ex = expectThrows(MapperParsingException.class, () -> createMapperService(settings, mappings));
+            assertEquals("Failed to parse mapping: _source can not be disabled in index using [logsdb] index mode", ex.getMessage());
+        }
+
+        // Test for IndexMode.TIME_SERIES
+        {
+            final String mappings = """
+                    {
+                        "_doc" : {
+                            "properties": {
+                                "routing_field": {
+                                    "type": "keyword",
+                                    "time_series_dimension": true
+                                }
+                            }
+                        }
+                    }
+                """;
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.TIME_SERIES.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.SYNTHETIC)
+                .put(IndexMetadata.INDEX_ROUTING_PATH.getKey(), "routing_field")
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isSynthetic());
+        }
+        {
+            final String mappings = """
+                    {
+                        "_doc" : {
+                            "properties": {
+                                "routing_field": {
+                                    "type": "keyword",
+                                    "time_series_dimension": true
+                                }
+                            }
+                        }
+                    }
+                """;
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.TIME_SERIES.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.STORED)
+                .put(IndexMetadata.INDEX_ROUTING_PATH.getKey(), "routing_field")
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            final DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isStored());
+        }
+        {
+            final String mappings = """
+                    {
+                        "_doc" : {
+                            "properties": {
+                                "routing_field": {
+                                    "type": "keyword",
+                                    "time_series_dimension": true
+                                }
+                            }
+                        }
+                    }
+                """;
+            final Settings settings = Settings.builder()
+                .put(IndexSettings.MODE.getKey(), IndexMode.TIME_SERIES.name())
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.DISABLED)
+                .put(IndexMetadata.INDEX_ROUTING_PATH.getKey(), "routing_field")
+                .build();
+            var ex = expectThrows(MapperParsingException.class, () -> createMapperService(settings, mappings));
+            assertEquals("Failed to parse mapping: _source can not be disabled in index using [time_series] index mode", ex.getMessage());
+        }
+
+        // Test cases without IndexMode (default to standard)
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.SYNTHETIC)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isSynthetic());
+        }
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.STORED)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            final DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isStored());
+        }
+        {
+            final XContentBuilder mappings = topMapping(b -> {});
+            final Settings settings = Settings.builder()
+                .put(SourceFieldMapper.INDEX_MAPPER_SOURCE_MODE_SETTING.getKey(), SourceFieldMapper.Mode.DISABLED)
+                .build();
+            final MapperService mapperService = createMapperService(settings, mappings);
+            final DocumentMapper docMapper = mapperService.documentMapper();
+            assertTrue(docMapper.sourceMapper().isDisabled());
+        }
+    }
+
     public void testRecoverySourceWithLogsCustom() throws IOException {
         XContentBuilder mappings = topMapping(b -> b.startObject(SourceFieldMapper.NAME).field("mode", "synthetic").endObject());
         {