diff --git a/chat2db-community-server/chat2db-community-domain/chat2db-community-domain-core/src/test/java/ai/chat2db/community/domain/core/completion/SqlCompletionMetadataProviderAdapterTest.java b/chat2db-community-server/chat2db-community-domain/chat2db-community-domain-core/src/test/java/ai/chat2db/community/domain/core/completion/SqlCompletionMetadataProviderAdapterTest.java
index c89ff7bf8e..a04c337c82 100644
--- a/chat2db-community-server/chat2db-community-domain/chat2db-community-domain-core/src/test/java/ai/chat2db/community/domain/core/completion/SqlCompletionMetadataProviderAdapterTest.java
+++ b/chat2db-community-server/chat2db-community-domain/chat2db-community-domain-core/src/test/java/ai/chat2db/community/domain/core/completion/SqlCompletionMetadataProviderAdapterTest.java
@@ -248,6 +248,14 @@ public String quoteIdentifier(String identifier) {
             return identifier == null ? null : "`" + identifier + "`";
         }
 
+        @Override
+        public String quoteIdentifierAlways(String identifier) {
+            if (identifier == null) {
+                return null;
+            }
+            return "`" + identifier.replace("`", "``") + "`";
+        }
+
         @Override
         public String removeIdentifierQuote(String identifier) {
             return identifier == null ? null : identifier.replace("`", "");
diff --git a/chat2db-community-server/chat2db-community-plugins/chat2db-community-kingbase/src/main/java/ai/chat2db/plugin/kingbase/enums/type/KingBaseIndexTypeEnum.java b/chat2db-community-server/chat2db-community-plugins/chat2db-community-kingbase/src/main/java/ai/chat2db/plugin/kingbase/enums/type/KingBaseIndexTypeEnum.java
index df1080bc8a..1de7d3a7ee 100644
--- a/chat2db-community-server/chat2db-community-plugins/chat2db-community-kingbase/src/main/java/ai/chat2db/plugin/kingbase/enums/type/KingBaseIndexTypeEnum.java
+++ b/chat2db-community-server/chat2db-community-plugins/chat2db-community-kingbase/src/main/java/ai/chat2db/plugin/kingbase/enums/type/KingBaseIndexTypeEnum.java
@@ -12,6 +12,7 @@
 import java.util.List;
 
 import static ai.chat2db.plugin.kingbase.constant.KingBaseIndexTypeEnumConstants.*;
+import ai.chat2db.plugin.kingbase.KingBaseMetaData;
 public enum KingBaseIndexTypeEnum {
 
     PRIMARY("Primary", "PRIMARY KEY"),
@@ -92,10 +93,10 @@ private String buildForeignColum(TableIndex tableIndex) {
             StringBuilder script = new StringBuilder();
             script.append(" REFERENCES ");
             if (StringUtils.isNotBlank(tableIndex.getForeignSchemaName())) {
-                script.append(tableIndex.getForeignSchemaName()).append(".");
+                script.append(KingBaseMetaData.KINGBASE_SQL_IDENTIFIER_PROCESSOR.quoteIdentifierAlways(tableIndex.getForeignSchemaName())).append(".");
             }
             if (StringUtils.isNotBlank(tableIndex.getForeignTableName())) {
-                script.append(tableIndex.getForeignTableName()).append(" ");
+                script.append(KingBaseMetaData.KINGBASE_SQL_IDENTIFIER_PROCESSOR.quoteIdentifierAlways(tableIndex.getForeignTableName())).append(" ");
             }
             if (CollectionUtils.isNotEmpty(tableIndex.getForeignColumnNamelist())) {
                 script.append("(");
diff --git a/chat2db-community-server/chat2db-community-plugins/chat2db-community-mysql/src/main/java/ai/chat2db/plugin/mysql/identifier/MysqlIdentifierProcessor.java b/chat2db-community-server/chat2db-community-plugins/chat2db-community-mysql/src/main/java/ai/chat2db/plugin/mysql/identifier/MysqlIdentifierProcessor.java
index 5b83c4c18d..7e87ef42c8 100644
--- a/chat2db-community-server/chat2db-community-plugins/chat2db-community-mysql/src/main/java/ai/chat2db/plugin/mysql/identifier/MysqlIdentifierProcessor.java
+++ b/chat2db-community-server/chat2db-community-plugins/chat2db-community-mysql/src/main/java/ai/chat2db/plugin/mysql/identifier/MysqlIdentifierProcessor.java
@@ -306,12 +306,26 @@ public String quoteIdentifier(String identifier) {
         return "`" + identifier + "`";
     }
 
+    @Override
+    public String quoteIdentifierAlways(String identifier) {
+        if (identifier == null) {
+            return null;
+        }
+        return "`" + identifier.replace("`", "``") + "`";
+    }
+
     @Override
     public String removeIdentifierQuote(String identifier) {
         if (StringUtils.isBlank(identifier)) {
             return identifier;
         }
-        return removePattern(identifier, MYSQL_PATTERN);
+        if (identifier.startsWith("`") && identifier.endsWith("`") && identifier.length() >= 2) {
+            return identifier.substring(1, identifier.length() - 1).replace("``", "`");
+        }
+        if (identifier.startsWith("\"") && identifier.endsWith("\"") && identifier.length() >= 2) {
+            return identifier.substring(1, identifier.length() - 1).replace("\"\"", "\"");
+        }
+        return identifier;
     }
 
     @Override
diff --git a/chat2db-community-server/chat2db-community-plugins/chat2db-community-mysql/src/test/java/ai/chat2db/plugin/mysql/identifier/MysqlIdentifierProcessorTest.java b/chat2db-community-server/chat2db-community-plugins/chat2db-community-mysql/src/test/java/ai/chat2db/plugin/mysql/identifier/MysqlIdentifierProcessorTest.java
new file mode 100644
index 0000000000..aba8fb9915
--- /dev/null
+++ b/chat2db-community-server/chat2db-community-plugins/chat2db-community-mysql/src/test/java/ai/chat2db/plugin/mysql/identifier/MysqlIdentifierProcessorTest.java
@@ -0,0 +1,70 @@
+package ai.chat2db.plugin.mysql.identifier;
+
+import ai.chat2db.spi.DefaultSQLIdentifierProcessor;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * Contract tests for {@link MysqlIdentifierProcessor}.
+ * Covers the backtick-based {@code quoteIdentifierAlways} /
+ * {@code removeIdentifierQuote} round-trip and embedded-delimiter escaping.
+ */
+class MysqlIdentifierProcessorTest {
+
+    private final MysqlIdentifierProcessor processor = new MysqlIdentifierProcessor();
+
+    @Test
+    void quoteIdentifierAlways_wrapsInBacktick() {
+        assertEquals("`mycol`", processor.quoteIdentifierAlways("mycol"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_escapesEmbeddedBacktick() {
+        assertEquals("`a``b`", processor.quoteIdentifierAlways("a`b"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_preservesMixedCase() {
+        assertEquals("`MixedCase`", processor.quoteIdentifierAlways("MixedCase"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_handlesNull() {
+        assertNull(processor.quoteIdentifierAlways(null));
+    }
+
+    @Test
+    void removeIdentifierQuote_stripsBacktick() {
+        assertEquals("mycol", processor.removeIdentifierQuote("`mycol`"));
+    }
+
+    @Test
+    void removeIdentifierQuote_unescapesBacktick() {
+        assertEquals("a`b", processor.removeIdentifierQuote("`a``b`"));
+    }
+
+    @Test
+    void removeIdentifierQuote_stripsDoubleQuote() {
+        assertEquals("mycol", processor.removeIdentifierQuote("\"mycol\""));
+    }
+
+    @Test
+    void roundTrip_plainName() {
+        String raw = "mycol";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_embeddedBacktick() {
+        String raw = "a`b";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_mixedCase() {
+        String raw = "MixedCase";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+}
diff --git a/chat2db-community-server/chat2db-community-plugins/chat2db-community-postgresql/src/main/java/ai/chat2db/plugin/postgresql/enums/type/PostgreSQLIndexTypeEnum.java b/chat2db-community-server/chat2db-community-plugins/chat2db-community-postgresql/src/main/java/ai/chat2db/plugin/postgresql/enums/type/PostgreSQLIndexTypeEnum.java
index e4ecc099fa..638894ade9 100644
--- a/chat2db-community-server/chat2db-community-plugins/chat2db-community-postgresql/src/main/java/ai/chat2db/plugin/postgresql/enums/type/PostgreSQLIndexTypeEnum.java
+++ b/chat2db-community-server/chat2db-community-plugins/chat2db-community-postgresql/src/main/java/ai/chat2db/plugin/postgresql/enums/type/PostgreSQLIndexTypeEnum.java
@@ -12,6 +12,7 @@
 import java.util.List;
 
 import static ai.chat2db.plugin.postgresql.constant.PostgreSQLIndexTypeEnumConstants.*;
+import ai.chat2db.plugin.postgresql.PostgreSQLMetaData;
 public enum PostgreSQLIndexTypeEnum {
 
     PRIMARY("Primary", "PRIMARY KEY"),
@@ -92,10 +93,10 @@ private String buildForeignColum(TableIndex tableIndex) {
             StringBuilder script = new StringBuilder();
             script.append(" REFERENCES ");
             if (StringUtils.isNotBlank(tableIndex.getForeignSchemaName())) {
-                script.append(tableIndex.getForeignSchemaName()).append(".");
+                script.append(PostgreSQLMetaData.POSTGRE_SQL_IDENTIFIER_PROCESSOR.quoteIdentifierAlways(tableIndex.getForeignSchemaName())).append(".");
             }
             if (StringUtils.isNotBlank(tableIndex.getForeignTableName())) {
-                script.append(tableIndex.getForeignTableName()).append(" ");
+                script.append(PostgreSQLMetaData.POSTGRE_SQL_IDENTIFIER_PROCESSOR.quoteIdentifierAlways(tableIndex.getForeignTableName())).append(" ");
             }
             if (CollectionUtils.isNotEmpty(tableIndex.getForeignColumnNamelist())) {
                 script.append("(");
diff --git a/chat2db-community-server/chat2db-community-plugins/chat2db-community-snowflake/src/main/java/ai/chat2db/plugin/snowflake/SnowflakeMetaData.java b/chat2db-community-server/chat2db-community-plugins/chat2db-community-snowflake/src/main/java/ai/chat2db/plugin/snowflake/SnowflakeMetaData.java
index cd94c4b461..e4251b90dd 100644
--- a/chat2db-community-server/chat2db-community-plugins/chat2db-community-snowflake/src/main/java/ai/chat2db/plugin/snowflake/SnowflakeMetaData.java
+++ b/chat2db-community-server/chat2db-community-plugins/chat2db-community-snowflake/src/main/java/ai/chat2db/plugin/snowflake/SnowflakeMetaData.java
@@ -3,6 +3,8 @@
 import ai.chat2db.plugin.snowflake.builder.SnowflakeSqlBuilder;
 import ai.chat2db.plugin.snowflake.enums.type.*;
 import ai.chat2db.spi.IDbMetaData;
+import ai.chat2db.spi.DefaultSQLIdentifierProcessor;
+import ai.chat2db.spi.ISQLIdentifierProcessor;
 import ai.chat2db.spi.ISqlBuilder;
 import ai.chat2db.spi.DefaultMetaService;
 import ai.chat2db.community.domain.api.model.account.*;
@@ -29,6 +31,8 @@
 import static ai.chat2db.plugin.snowflake.constant.SnowflakeMetaDataConstants.*;
 public class SnowflakeMetaData extends DefaultMetaService implements IDbMetaData {
 
+    public static final ISQLIdentifierProcessor SNOWFLAKE_SQL_IDENTIFIER_PROCESSOR = new DefaultSQLIdentifierProcessor();
+
 
 
     @Override
diff --git a/chat2db-community-server/chat2db-community-plugins/chat2db-community-sqlserver/src/main/java/ai/chat2db/plugin/sqlserver/identifier/SqlServerIdentifierProcessor.java b/chat2db-community-server/chat2db-community-plugins/chat2db-community-sqlserver/src/main/java/ai/chat2db/plugin/sqlserver/identifier/SqlServerIdentifierProcessor.java
index 1c0df48daa..f74b41ab47 100644
--- a/chat2db-community-server/chat2db-community-plugins/chat2db-community-sqlserver/src/main/java/ai/chat2db/plugin/sqlserver/identifier/SqlServerIdentifierProcessor.java
+++ b/chat2db-community-server/chat2db-community-plugins/chat2db-community-sqlserver/src/main/java/ai/chat2db/plugin/sqlserver/identifier/SqlServerIdentifierProcessor.java
@@ -219,12 +219,26 @@ public String quoteIdentifier(String identifier) {
         return "[" + identifier + "]";
     }
 
+    @Override
+    public String quoteIdentifierAlways(String identifier) {
+        if (identifier == null) {
+            return null;
+        }
+        return "[" + identifier.replace("]", "]]") + "]";
+    }
+
     @Override
     public String removeIdentifierQuote(String identifier) {
         if (StringUtils.isBlank(identifier)) {
             return identifier;
         }
-        return removePattern(identifier, SQL_SERVER_PATTERN);
+        if (identifier.startsWith("[") && identifier.endsWith("]") && identifier.length() >= 2) {
+            return identifier.substring(1, identifier.length() - 1).replace("]]", "]");
+        }
+        if (identifier.startsWith("\"") && identifier.endsWith("\"") && identifier.length() >= 2) {
+            return identifier.substring(1, identifier.length() - 1).replace("\"\"", "\"");
+        }
+        return identifier;
     }
 
     @Override
diff --git a/chat2db-community-server/chat2db-community-plugins/chat2db-community-sqlserver/src/test/java/ai/chat2db/plugin/sqlserver/identifier/SqlServerIdentifierProcessorTest.java b/chat2db-community-server/chat2db-community-plugins/chat2db-community-sqlserver/src/test/java/ai/chat2db/plugin/sqlserver/identifier/SqlServerIdentifierProcessorTest.java
new file mode 100644
index 0000000000..31c8249911
--- /dev/null
+++ b/chat2db-community-server/chat2db-community-plugins/chat2db-community-sqlserver/src/test/java/ai/chat2db/plugin/sqlserver/identifier/SqlServerIdentifierProcessorTest.java
@@ -0,0 +1,69 @@
+package ai.chat2db.plugin.sqlserver.identifier;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * Contract tests for {@link SqlServerIdentifierProcessor}.
+ * Covers the bracket-based {@code quoteIdentifierAlways} /
+ * {@code removeIdentifierQuote} round-trip and embedded-delimiter escaping.
+ */
+class SqlServerIdentifierProcessorTest {
+
+    private final SqlServerIdentifierProcessor processor = new SqlServerIdentifierProcessor();
+
+    @Test
+    void quoteIdentifierAlways_wrapsInBrackets() {
+        assertEquals("[mycol]", processor.quoteIdentifierAlways("mycol"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_preservesMixedCase() {
+        assertEquals("[MixedCase]", processor.quoteIdentifierAlways("MixedCase"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_escapesEmbeddedCloseBracket() {
+        assertEquals("[a]]b]", processor.quoteIdentifierAlways("a]b"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_handlesNull() {
+        assertNull(processor.quoteIdentifierAlways(null));
+    }
+
+    @Test
+    void removeIdentifierQuote_stripsBrackets() {
+        assertEquals("mycol", processor.removeIdentifierQuote("[mycol]"));
+    }
+
+    @Test
+    void removeIdentifierQuote_unescapesCloseBracket() {
+        assertEquals("a]b", processor.removeIdentifierQuote("[a]]b]"));
+    }
+
+    @Test
+    void removeIdentifierQuote_stripsDoubleQuote() {
+        assertEquals("mycol", processor.removeIdentifierQuote("\"mycol\""));
+    }
+
+    @Test
+    void roundTrip_plainName() {
+        String raw = "mycol";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_embeddedCloseBracket() {
+        String raw = "a]b";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_mixedCase() {
+        String raw = "MixedCase";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+}
diff --git a/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/DefaultSQLIdentifierProcessor.java b/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/DefaultSQLIdentifierProcessor.java
index faa8b3b5fd..23fa275a95 100644
--- a/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/DefaultSQLIdentifierProcessor.java
+++ b/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/DefaultSQLIdentifierProcessor.java
@@ -41,12 +41,23 @@ public String quoteIdentifier(String identifier) {
         return StringUtils.wrap(identifier, '"');
     }
 
+    @Override
+    public String quoteIdentifierAlways(String identifier) {
+        if (identifier == null) {
+            return null;
+        }
+        return "\"" + identifier.replace("\"", "\"\"") + "\"";
+    }
+
     @Override
     public String removeIdentifierQuote(String identifier) {
         if (StringUtils.isBlank(identifier)) {
             return identifier;
         }
-        return removePattern(identifier, STANDARD_PATTERN);
+        if (identifier.startsWith("\"") && identifier.endsWith("\"") && identifier.length() >= 2) {
+            return identifier.substring(1, identifier.length() - 1).replace("\"\"", "\"");
+        }
+        return identifier;
     }
 
     @Override
diff --git a/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/ISQLIdentifierProcessor.java b/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/ISQLIdentifierProcessor.java
index d87387ea65..7d4cd549a7 100644
--- a/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/ISQLIdentifierProcessor.java
+++ b/chat2db-community-server/chat2db-community-spi/src/main/java/ai/chat2db/spi/ISQLIdentifierProcessor.java
@@ -87,4 +87,16 @@ public interface ISQLIdentifierProcessor {
      */
     String escapeString(String str);
 
+
+    /**
+     * Quotes an identifier unconditionally, preserving the exact name.
+     * <p>
+     * Embedded delimiter characters are escaped per the dialect convention.
+     * Satisfies: {@code removeIdentifierQuote(quoteIdentifierAlways(raw)).equals(raw)}
+     *
+     * @param identifier raw identifier text.
+     * @return unconditionally quoted identifier text with the original case preserved.
+     */
+    String quoteIdentifierAlways(String identifier);
+
 }
diff --git a/chat2db-community-server/chat2db-community-spi/src/test/java/ai/chat2db/spi/DefaultSQLIdentifierProcessorTest.java b/chat2db-community-server/chat2db-community-spi/src/test/java/ai/chat2db/spi/DefaultSQLIdentifierProcessorTest.java
new file mode 100644
index 0000000000..93198ac695
--- /dev/null
+++ b/chat2db-community-server/chat2db-community-spi/src/test/java/ai/chat2db/spi/DefaultSQLIdentifierProcessorTest.java
@@ -0,0 +1,110 @@
+package ai.chat2db.spi;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+/**
+ * Contract tests for {@link DefaultSQLIdentifierProcessor}.
+ * Covers the {@code quoteIdentifierAlways} / {@code removeIdentifierQuote}
+ * round-trip, conditional vs always-quote behavior, and embedded-delimiter
+ * escaping.
+ */
+class DefaultSQLIdentifierProcessorTest {
+
+    private final DefaultSQLIdentifierProcessor processor = new DefaultSQLIdentifierProcessor();
+
+    // ---- quoteIdentifierAlways ----
+
+    @Test
+    void quoteIdentifierAlways_wrapsSimpleName() {
+        assertEquals("\"mycol\"", processor.quoteIdentifierAlways("mycol"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_preservesMixedCase() {
+        assertEquals("\"MixedCase\"", processor.quoteIdentifierAlways("MixedCase"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_escapesEmbeddedDoubleQuote() {
+        assertEquals("\"A\"\"B\"", processor.quoteIdentifierAlways("A\"B"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_handlesReservedKeyword() {
+        assertEquals("\"SELECT\"", processor.quoteIdentifierAlways("SELECT"));
+    }
+
+    @Test
+    void quoteIdentifierAlways_handlesNull() {
+        assertNull(processor.quoteIdentifierAlways(null));
+    }
+
+    // ---- quoteIdentifier (conditional) ----
+
+    @Test
+    void quoteIdentifier_doesNotQuoteLowercaseValid() {
+        assertEquals("lower", processor.quoteIdentifier("lower"));
+    }
+
+    @Test
+    void quoteIdentifier_quotesInvalidIdentifier() {
+        assertEquals("\"a b\"", processor.quoteIdentifier("a b"));
+    }
+
+    @Test
+    void quoteIdentifierIgnoreCase_doesNotQuoteLowercase() {
+        assertEquals("lower", processor.quoteIdentifierIgnoreCase("lower"));
+    }
+
+    // ---- removeIdentifierQuote ----
+
+    @Test
+    void removeIdentifierQuote_stripsAndUnescapes() {
+        assertEquals("A\"B", processor.removeIdentifierQuote("\"A\"\"B\""));
+    }
+
+    @Test
+    void removeIdentifierQuote_passesThroughUnquoted() {
+        assertEquals("plain", processor.removeIdentifierQuote("plain"));
+    }
+
+    @Test
+    void removeIdentifierQuote_stripsSimpleQuoted() {
+        assertEquals("mycol", processor.removeIdentifierQuote("\"mycol\""));
+    }
+
+    // ---- round-trip ----
+
+    @Test
+    void roundTrip_plainName() {
+        String raw = "mycol";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_mixedCase() {
+        String raw = "MixedCase";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_embeddedDelimiter() {
+        String raw = "A\"B";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_reservedKeyword() {
+        String raw = "SELECT";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+
+    @Test
+    void roundTrip_empty() {
+        String raw = "";
+        assertEquals(raw, processor.removeIdentifierQuote(processor.quoteIdentifierAlways(raw)));
+    }
+}