diff --git a/.github/workflows/sandbox-verification.yml b/.github/workflows/sandbox-verification.yml
index 7c18979..94d51d2 100644
--- a/.github/workflows/sandbox-verification.yml
+++ b/.github/workflows/sandbox-verification.yml
@@ -179,15 +179,9 @@ jobs:
             # (the backend field is String?, not an embedded object).
             # sys.argv avoids shell-quoting issues with special characters.
             if [ -z "${params}" ]; then
-              BODY=$(python3 -c "
-import json, sys
-print(json.dumps({'columnName': sys.argv[1], 'generatorType': sys.argv[2]}))
-" -- "${col}" "${gtype}")
+              BODY=$(python3 -c "import json, sys; print(json.dumps({'columnName': sys.argv[1], 'generatorType': sys.argv[2]}))" "${col}" "${gtype}")
             else
-              BODY=$(python3 -c "
-import json, sys
-print(json.dumps({'columnName': sys.argv[1], 'generatorType': sys.argv[2], 'generatorParams': sys.argv[3]}))
-" -- "${col}" "${gtype}" "${params}")
+              BODY=$(python3 -c "import json, sys; print(json.dumps({'columnName': sys.argv[1], 'generatorType': sys.argv[2], 'generatorParams': sys.argv[3]}))" "${col}" "${gtype}" "${params}")
             fi
             curl -sf -X POST "${API_BASE}/api/workspaces/${WS_ID}/tables/${TABLE_ID}/generators" \
               -H "Content-Type: application/json" \
diff --git a/backend/src/main/kotlin/com/opendatamask/application/service/GeneratorService.kt b/backend/src/main/kotlin/com/opendatamask/application/service/GeneratorService.kt
index aebd80b..bf4a5fe 100644
--- a/backend/src/main/kotlin/com/opendatamask/application/service/GeneratorService.kt
+++ b/backend/src/main/kotlin/com/opendatamask/application/service/GeneratorService.kt
@@ -68,7 +68,7 @@ class GeneratorService(
             GeneratorType.ADDRESS -> faker.address().fullAddress()
             GeneratorType.SSN -> faker.idNumber().ssnValid()
             GeneratorType.CREDIT_CARD -> faker.finance().creditCard()
-            GeneratorType.DATE -> faker.date().past(365 * 10, TimeUnit.DAYS).toString()
+            GeneratorType.DATE -> java.sql.Date(faker.date().past(365 * 10, TimeUnit.DAYS).time)
             GeneratorType.UUID -> UUID.randomUUID().toString()
             GeneratorType.CONSTANT -> params?.get("value") ?: ""
             GeneratorType.NULL -> null
@@ -87,11 +87,11 @@ class GeneratorService(
             GeneratorType.PASSWORD -> faker.internet().password(8, 20, true, true, true)
             GeneratorType.IBAN -> faker.finance().iban()
             GeneratorType.SWIFT_CODE -> faker.finance().bic()
-            GeneratorType.MONEY_AMOUNT -> faker.commerce().price()
+            GeneratorType.MONEY_AMOUNT -> java.math.BigDecimal(faker.commerce().price())
             GeneratorType.BTC_ADDRESS -> faker.regexify("1[A-HJ-NP-Za-km-z1-9]{33}")
             GeneratorType.PASSPORT_NUMBER -> faker.regexify("[A-Z]{2}[0-9]{7}")
             GeneratorType.DRIVERS_LICENSE -> faker.regexify("[A-Z][0-9]{7}")
-            GeneratorType.BIRTH_DATE -> faker.date().birthday().toString()
+            GeneratorType.BIRTH_DATE -> java.sql.Date(faker.date().birthday().time)
             GeneratorType.GENDER -> listOf("Male", "Female", "Non-binary", "Prefer not to say").random()
             GeneratorType.ICD_CODE -> faker.regexify("[A-Z][0-9]{2}\\.[0-9]{1,2}")
             GeneratorType.MEDICAL_RECORD_NUMBER -> faker.regexify("MRN-[0-9]{8}")
@@ -136,12 +136,12 @@ class GeneratorService(
                 val step = params?.get("step")?.toLongOrNull() ?: 1L
                 val key = columnKey ?: "default"
                 val counter = sequentialCounters.computeIfAbsent(key) { AtomicLong(start - step) }
-                counter.addAndGet(step).toString()
+                counter.addAndGet(step)
             }
             GeneratorType.RANDOM_INT -> {
                 val min = params?.get("min")?.toLongOrNull() ?: 1L
                 val max = params?.get("max")?.toLongOrNull() ?: 999999L
-                faker.number().numberBetween(min, max).toString()
+                faker.number().numberBetween(min, max)
             }
             GeneratorType.CONDITIONAL -> {
                 val jsonParams = rawParams?.let {
diff --git a/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceCompositeTest.kt b/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceCompositeTest.kt
index 28fc734..baa8a09 100644
--- a/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceCompositeTest.kt
+++ b/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceCompositeTest.kt
@@ -142,55 +142,53 @@ class GeneratorServiceCompositeTest {
             null,
             mapOf("start" to "10", "step" to "1"),
             columnKey = "test:seq_col_start"
-        ) as String
-        assertEquals("10", result)
+        ) as Long
+        assertEquals(10L, result)
     }
 
     @Test
     fun `SEQUENTIAL increments by step`() {
         val key = "test:seq_col_step"
-        val r1 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "5"), columnKey = key) as String
-        val r2 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "5"), columnKey = key) as String
-        val r3 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "5"), columnKey = key) as String
-        assertEquals("1", r1)
-        assertEquals("6", r2)
-        assertEquals("11", r3)
+        val r1 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "5"), columnKey = key) as Long
+        val r2 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "5"), columnKey = key) as Long
+        val r3 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "5"), columnKey = key) as Long
+        assertEquals(1L, r1)
+        assertEquals(6L, r2)
+        assertEquals(11L, r3)
     }
 
     @Test
     fun `SEQUENTIAL uses separate counters per column key`() {
-        val r1 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "1"), columnKey = "table:col_a") as String
-        val r2 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "1"), columnKey = "table:col_b") as String
-        assertEquals("1", r1)
-        assertEquals("1", r2, "Different column keys should have independent counters")
+        val r1 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "1"), columnKey = "table:col_a") as Long
+        val r2 = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "1"), columnKey = "table:col_b") as Long
+        assertEquals(1L, r1)
+        assertEquals(1L, r2, "Different column keys should have independent counters")
     }
 
     // ── RANDOM_INT ────────────────────────────────────────────────────────────
 
     @Test
-    fun `RANDOM_INT returns string within range`() {
+    fun `RANDOM_INT returns Long within range`() {
         val result = service.generateValue(
             GeneratorType.RANDOM_INT,
             null,
             mapOf("min" to "1000", "max" to "9999999")
-        ) as String
-        val num = result.toLong()
-        assertTrue(num >= 1000, "Result $num should be >= 1000")
-        assertTrue(num <= 9999999, "Result $num should be <= 9999999")
+        ) as Long
+        assertTrue(result >= 1000, "Result $result should be >= 1000")
+        assertTrue(result <= 9999999, "Result $result should be <= 9999999")
     }
 
     @Test
-    fun `RANDOM_INT returns a string not an integer`() {
+    fun `RANDOM_INT returns a Long not a String`() {
         val result = service.generateValue(GeneratorType.RANDOM_INT, null, mapOf("min" to "1", "max" to "100"))
         assertNotNull(result)
-        assertTrue(result is String, "RANDOM_INT should return a String, got ${result?.javaClass}")
+        assertTrue(result is Long, "RANDOM_INT should return a Long, got ${result?.javaClass}")
     }
 
     @Test
     fun `RANDOM_INT uses defaults when no params`() {
-        val result = service.generateValue(GeneratorType.RANDOM_INT, null, null) as String
-        val num = result.toLong()
-        assertTrue(num >= 1)
-        assertTrue(num <= 999999)
+        val result = service.generateValue(GeneratorType.RANDOM_INT, null, null) as Long
+        assertTrue(result >= 1)
+        assertTrue(result <= 999999)
     }
 }
diff --git a/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceTest.kt b/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceTest.kt
index ee32bc9..8e31239 100644
--- a/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceTest.kt
+++ b/backend/src/test/kotlin/com/opendatamask/application/service/GeneratorServiceTest.kt
@@ -58,9 +58,17 @@ class GeneratorServiceTest {
     }
 
     @Test
-    fun `DATE generates a non-null date string`() {
+    fun `DATE generates a java sql Date`() {
         val result = service.generateValue(GeneratorType.DATE, "2024-01-01", null)
         assertNotNull(result)
+        assertInstanceOf(java.sql.Date::class.java, result)
+    }
+
+    @Test
+    fun `BIRTH_DATE generates a java sql Date`() {
+        val result = service.generateValue(GeneratorType.BIRTH_DATE, "1990-01-15", null)
+        assertNotNull(result)
+        assertInstanceOf(java.sql.Date::class.java, result)
     }
 
     @Test
@@ -170,4 +178,28 @@ class GeneratorServiceTest {
         val result = service.generateValue(GeneratorType.CUSTOM, "fallback", null)
         assertEquals("fallback", result)
     }
+
+    @Test
+    fun `RANDOM_INT generates a Long`() {
+        val result = service.generateValue(GeneratorType.RANDOM_INT, null, mapOf("min" to "30000", "max" to "200000"))
+        assertNotNull(result)
+        assertInstanceOf(java.lang.Long::class.java, result)
+        val value = result as Long
+        assertTrue(value in 30000..199999)
+    }
+
+    @Test
+    fun `SEQUENTIAL generates a Long`() {
+        val result = service.generateValue(GeneratorType.SEQUENTIAL, null, mapOf("start" to "1", "step" to "1"), columnKey = "test:seq")
+        assertNotNull(result)
+        assertInstanceOf(java.lang.Long::class.java, result)
+        assertEquals(1L, result)
+    }
+
+    @Test
+    fun `MONEY_AMOUNT generates a BigDecimal`() {
+        val result = service.generateValue(GeneratorType.MONEY_AMOUNT, null, null)
+        assertNotNull(result)
+        assertInstanceOf(java.math.BigDecimal::class.java, result)
+    }
 }