diff --git a/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/NativeStringExpressionEvaluator.java b/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/NativeStringExpressionEvaluator.java
index d0156bbdd..9bc068a0e 100644
--- a/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/NativeStringExpressionEvaluator.java
+++ b/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/NativeStringExpressionEvaluator.java
@@ -38,6 +38,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.UUID;
+import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 /** Evaluates SPARQL expressions that produce string literals. */
@@ -209,7 +210,8 @@ private static DatatypeValue replace(ReplaceAst expression, NativeEvaluationCont
             throw new QueryTypeErrorException("REPLACE pattern must not match an empty string");
         }
         try {
-            String result = compiled.matcher(source.getLabel()).replaceAll(replacement);
+            String result = compiled.matcher(source.getLabel()).replaceAll(
+                    flags.contains("q") ? Matcher.quoteReplacement(replacement) : replacement);
             return stringLike(source, result, context);
         } catch (IndexOutOfBoundsException invalidGroup) {
             throw new QueryTypeErrorException("Invalid replacement group", invalidGroup);
@@ -260,21 +262,34 @@ private static DatatypeValue digest(
         }
     }
 
+    @SuppressWarnings("MagicConstant")
     private static Pattern compilePattern(String expression, String flags) {
         int options = regexOptions(flags);
-        return Pattern.compile(flags.contains("x") ? removePatternWhitespace(expression) : expression, options);
+        String processed = expression;
+        if (flags.contains("q")) {
+            processed = Pattern.quote(expression);
+        } else if (flags.contains("x")) {
+            processed = removePatternWhitespace(expression);
+        }
+        return Pattern.compile(processed, options);
     }
 
+    /** XPath x ignores XML whitespace outside character classes, but does not introduce comments. */
     private static String removePatternWhitespace(String expression) {
-        StringBuilder result = new StringBuilder();
+        StringBuilder result = new StringBuilder(expression.length());
         boolean escaped = false;
         int brackets = 0;
         for (int index = 0; index < expression.length(); index++) {
             char character = expression.charAt(index);
+            if (brackets == 0 && " \t\r\n".indexOf(character) >= 0) {
+                continue;
+            }
             if (!escaped) {
-                if (character == '[') brackets++;
-                if (character == ']') brackets--;
-                if (brackets == 0 && " \t\r\n".indexOf(character) >= 0) continue;
+                if (character == '[') {
+                    brackets++;
+                } else if (character == ']' && brackets > 0) {
+                    brackets--;
+                }
             }
             result.append(character);
             escaped = !escaped && character == '\\';
@@ -282,8 +297,9 @@ private static String removePatternWhitespace(String expression) {
         return result.toString();
     }
 
+    /** @return a combination of {@link Pattern} flag constants */
     private static int regexOptions(String flags) {
-        if (!flags.chars().allMatch(flag -> "imsx".indexOf(flag) >= 0)) {
+        if (!flags.chars().allMatch(flag -> "imsxq".indexOf(flag) >= 0)) {
             throw new QueryTypeErrorException("Invalid regular expression flags");
         }
         int options = 0;
diff --git a/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolver.java b/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolver.java
index 179ee5292..60155b40e 100644
--- a/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolver.java
+++ b/src/main/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolver.java
@@ -16,6 +16,7 @@
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 
 /** Resolves SPARQL terms against one immutable query-prologue snapshot. */
 public final class SparqlTermResolver {
@@ -98,10 +99,35 @@ public String unquoteLexical(String lexical) {
             return lexical;
         }
         String unquotedTriple = stripTripleQuotes(lexical);
-        if (unquotedTriple != null) {
-            return unquotedTriple;
+        return processSparqlEscapes(Objects.requireNonNullElseGet(unquotedTriple, () -> stripSingleQuotes(lexical)));
+    }
+
+    static String processSparqlEscapes(String s) {
+        if (s.indexOf('\\') < 0) {
+            return s;
+        }
+        StringBuilder sb = new StringBuilder(s.length());
+        int i = 0;
+        while (i < s.length()) {
+            if (s.charAt(i) == '\\' && i + 1 < s.length()) {
+                i++;
+                switch (s.charAt(i)) {
+                    case 't' -> sb.append('\t');
+                    case 'n' -> sb.append('\n');
+                    case 'r' -> sb.append('\r');
+                    case 'b' -> sb.append('\b');
+                    case 'f' -> sb.append('\f');
+                    case '"' -> sb.append('"');
+                    case '\'' -> sb.append('\'');
+                    case '\\' -> sb.append('\\');
+                    default -> { sb.append('\\'); sb.append(s.charAt(i)); }
+                }
+            } else {
+                sb.append(s.charAt(i));
+            }
+            i++;
         }
-        return stripSingleQuotes(lexical);
+        return sb.toString();
     }
 
     private static String stripTripleQuotes(String lexical) {
diff --git a/src/test/java/fr/inria/corese/core/next/query/impl/sparql/bridge/NativeExpressionEvaluatorTest.java b/src/test/java/fr/inria/corese/core/next/query/impl/sparql/bridge/NativeExpressionEvaluatorTest.java
new file mode 100644
index 000000000..52dc83c06
--- /dev/null
+++ b/src/test/java/fr/inria/corese/core/next/query/impl/sparql/bridge/NativeExpressionEvaluatorTest.java
@@ -0,0 +1,137 @@
+package fr.inria.corese.core.next.query.impl.sparql.bridge;
+
+import fr.inria.corese.core.next.query.Repositories;
+import fr.inria.corese.core.next.storage.impl.memory.MemoryStorageManager;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Unit tests for SPARQL REGEX built-in with XPath flag support.
+ *
+ */
+@DisplayName("NativeExpressionEvaluator - XPath REGEX flag support")
+class NativeExpressionEvaluatorTest {
+
+    private boolean ask(String filter) {
+        try (var repo = Repositories.create(MemoryStorageManager.builder().build());
+             var conn = repo.getConnection()) {
+            return conn.prepareBooleanQuery(
+                    "PREFIX ex: <http://example.com/#> ASK { FILTER(" + filter + ") }").evaluate();
+        }
+    }
+
+
+    @Test
+    @DisplayName("REGEX with i flag matches case-insensitively")
+    void iFlagMatchesCaseInsensitively() {
+        assertTrue(ask("REGEX(\"ABCdefGHIjkl\", \"abc\", \"i\")"));
+        assertTrue(ask("REGEX(\"abcDEFghiJKL\", \"ABC\", \"i\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with s flag makes dot match newlines")
+    void sFlagDotMatchesNewline() {
+        assertTrue(ask("REGEX(\"a\\nb\", \"a.b\", \"s\")"));
+        assertFalse(ask("REGEX(\"a\\nb\", \"a.b\")"));
+    }
+
+
+    @Test
+    @DisplayName("REGEX with m flag makes ^ and $ match line boundaries")
+    void mFlagAnchorMatchesLineBoundary() {
+        assertTrue(ask("REGEX(\"foo\\nbar\", \"^bar$\", \"m\")"));
+        assertFalse(ask("REGEX(\"foo\\nbar\", \"^bar$\")"));
+    }
+
+
+    @Test
+    @DisplayName("REGEX with x flag ignores whitespace in pattern")
+    void xFlagIgnoresWhitespace() {
+        assertTrue(ask("REGEX(\"ac\", \" a c \", \"x\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with x flag ignores newline and tab in pattern")
+    void xFlagIgnoresNewlineAndTab() {
+        assertTrue(ask("REGEX(\"ac\", \" a\\n\\tc \", \"x\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with x flag preserves whitespace inside bracket expression")
+    void xFlagPreservesWhitespaceInsideBrackets() {
+        assertTrue(ask("REGEX(\"a\\nc\", \" a[\\\\n]c \", \"x\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with x flag preserves hashes and whitespace in classes")
+    void xFlagPreservesHashesAndClassWhitespace() {
+        assertFalse(ask("REGEX(\"a\", \"a#b\", \"x\")"));
+        assertTrue(ask("REGEX(\"a#b\", \" a # b \", \"x\")"));
+        assertTrue(ask("REGEX(\"#\", \"[#]\", \"x\")"));
+        assertTrue(ask("REGEX(\" \", \"[ a]\", \"x\")"));
+        assertTrue(ask("REGEX(\"\\n\\t\\r\", \"^[ \\n\\t\\r]+$\", \"x\")"));
+        assertFalse(ask("REGEX(\"ac\", \"a[ ]c\", \"x\")"));
+    }
+
+    @Test
+    void xFlagRespectsEscapedBrackets() {
+        assertTrue(ask("REGEX(\"[a]\", \"\\\\[ a \\\\]\", \"x\")"));
+        assertTrue(ask("REGEX(\"] \", \"^[\\\\] ]+$\", \"x\")"));
+    }
+
+    @Test
+    void qFlagOverridesOtherPatternFlags() {
+        assertTrue(ask("REGEX(\" A#b \", \" a#b \", \"qxims\")"));
+        assertFalse(ask("REGEX(\"ab\", \" a b \", \"qx\")"));
+        assertFalse(ask("REGEX(\"a\\nb\", \"a.b\", \"qs\")"));
+        assertFalse(ask("REGEX(\"a\\nb\", \"^b$\", \"qm\")"));
+    }
+
+    @Test
+    void qFlagQuotesReplacement() {
+        assertTrue(ask("REPLACE(\"a/b\", \"/\", \"$0\", \"q\") = \"a$0b\""));
+        assertTrue(ask("REPLACE(\"a/b\", \"/\", \"$\", \"q\") = \"a$b\""));
+        assertTrue(ask("REPLACE(\"a/b\", \"/\", \"\\\\\", \"q\") = \"a\\\\b\""));
+        assertTrue(ask("REPLACE(\"a/b\", \"/\", \"$0\") = \"a/b\""));
+    }
+
+    @Test
+    void xFlagAlsoAppliesToReplace() {
+        assertTrue(ask("REPLACE(\"a b\", \"[ ]\", \"-\", \"x\") = \"a-b\""));
+        assertTrue(ask("REPLACE(\"a#b\", \"#\", \"-\", \"x\") = \"a-b\""));
+    }
+
+    @Test
+    @DisplayName("REGEX with q flag treats pattern as literal (no metacharacters)")
+    void qFlagTreatsPatternAsLiteral() {
+        assertTrue(ask("REGEX(\"a?+*.{}()[]c\", \"a?+*.{}()[]c\", \"q\")"));
+        assertFalse(ask("REGEX(\"abc\", \"a?+*.{}()[]c\", \"q\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with iq flags matches literal pattern case-insensitively")
+    void iqFlagsMatchLiteralCaseInsensitively() {
+        assertTrue(ask("REGEX(\"a?+*.{}()[]c\", \"a?+*.{}()[]C\", \"iq\")"));
+        assertFalse(ask("REGEX(\"abc\", \"a?+*.{}()[]C\", \"iq\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with [] expression matches 'b' in character class")
+    void bracketExpressionMatchesB() {
+        assertTrue(ask("REGEX(\"abc\", \"a[b\\\\n]c\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with [] expression matches newline in character class")
+    void bracketExpressionMatchesNewline() {
+        assertTrue(ask("REGEX(\"a\\nc\", \"a[b\\\\n]c\")"));
+    }
+
+    @Test
+    @DisplayName("REGEX with [] expression does not match unrelated characters")
+    void bracketExpressionDoesNotMatchOther() {
+        assertFalse(ask("REGEX(\"adc\", \"a[b\\\\n]c\")"));
+    }
+}
diff --git a/src/test/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolverTest.java b/src/test/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolverTest.java
index d9b4c2f90..c91c2d5af 100644
--- a/src/test/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolverTest.java
+++ b/src/test/java/fr/inria/corese/core/next/query/impl/sparql/bridge/SparqlTermResolverTest.java
@@ -13,6 +13,23 @@
 
 class SparqlTermResolverTest {
 
+    @Test
+    void decodesSparqlEscapesExactlyOnce() {
+        SparqlTermResolver resolver = new SparqlTermResolver(null);
+
+        assertEquals("\t\n\r\b\f\"'\\", resolver.unquoteLexical("\"\\t\\n\\r\\b\\f\\\"\\'\\\\\""));
+        assertEquals("\\n", resolver.unquoteLexical("\"\\\\n\""));
+        assertEquals("a\nb", resolver.unquoteLexical("\"\"\"a\\nb\"\"\""));
+        assertEquals("a\tb", resolver.unquoteLexical("'''a\\tb'''"));
+    }
+
+    @Test
+    void preservesUnknownEscapesAndTrailingBackslash() {
+        assertEquals("\\d", SparqlTermResolver.processSparqlEscapes("\\d"));
+        assertEquals("end\\", SparqlTermResolver.processSparqlEscapes("end\\"));
+        assertEquals("", SparqlTermResolver.processSparqlEscapes(""));
+    }
+
     @Test
     void resolvesTermsFromItsOwnPrologue() {
         QueryPrologueAst prologue = new QueryPrologueAst(