diff --git a/arrow-libs/optics/arrow-optics-ksp-plugin/src/main/kotlin/arrow/optics/plugin/internals/domain.kt b/arrow-libs/optics/arrow-optics-ksp-plugin/src/main/kotlin/arrow/optics/plugin/internals/domain.kt
index b59e25c4f6..7652804661 100644
--- a/arrow-libs/optics/arrow-optics-ksp-plugin/src/main/kotlin/arrow/optics/plugin/internals/domain.kt
+++ b/arrow-libs/optics/arrow-optics-ksp-plugin/src/main/kotlin/arrow/optics/plugin/internals/domain.kt
@@ -6,9 +6,11 @@ import arrow.optics.plugin.companionObject
 import com.google.devtools.ksp.getDeclaredProperties
 import com.google.devtools.ksp.getVisibility
 import com.google.devtools.ksp.symbol.KSClassDeclaration
+import com.google.devtools.ksp.symbol.KSDeclaration
 import com.google.devtools.ksp.symbol.KSType
 import com.google.devtools.ksp.symbol.KSTypeParameter
 import com.google.devtools.ksp.symbol.Variance
+import com.google.devtools.ksp.symbol.Visibility
 import java.util.*
 
 data class ADT(val declaration: KSClassDeclaration, val targets: List<Target>) {
@@ -16,8 +18,7 @@ data class ADT(val declaration: KSClassDeclaration, val targets: List<Target>) {
   val sourceName = declaration.simpleName.asString().replaceFirstChar { it.lowercase(Locale.getDefault()) }.sanitize()
   val simpleName = declaration.nameWithParentClass
   val packageName = declaration.packageName.asSanitizedString()
-  val visibilityModifierName =
-    (declaration.companionObject?.getVisibility() ?: declaration.getVisibility()).name.lowercase()
+  val visibilityModifierName = declaration.effectiveCompanionVisibility.name.lowercase()
   val typeParameters: List<String> = declaration.typeParameters.map { tyParam ->
     if (tyParam.variance == Variance.STAR) return@map "*"
     // val prefix = when (it.variance) {
@@ -52,6 +53,36 @@ val KSClassDeclaration.nameWithParentClass: String
     else -> simpleName.asString()
   }
 
+val KSClassDeclaration.effectiveCompanionVisibility: Visibility
+  get() {
+    val visibilities =
+      listOfNotNull(companionObject?.getVisibility(), getVisibility()) +
+        allParentDeclarations().filterIsInstance<KSClassDeclaration>().map { it.getVisibility() }
+    return visibilities.foldRight(Visibility.PUBLIC, Visibility::plus)
+  }
+
+fun KSDeclaration.allParentDeclarations(): List<KSDeclaration> = when (val parent = parentDeclaration) {
+  null -> emptyList()
+  else -> listOfNotNull(parent) + parent.allParentDeclarations()
+}
+
+operator fun Visibility.plus(other: Visibility): Visibility = when {
+  this == other -> this
+
+  this == Visibility.PUBLIC -> other
+
+  other == Visibility.PUBLIC -> this
+
+  this == Visibility.LOCAL || other == Visibility.LOCAL -> Visibility.LOCAL
+
+  this == Visibility.PRIVATE || other == Visibility.PRIVATE -> Visibility.PRIVATE
+
+  (this == Visibility.INTERNAL || this == Visibility.PROTECTED) &&
+    (other == Visibility.INTERNAL || other == Visibility.PROTECTED) -> Visibility.PRIVATE
+
+  else -> Visibility.PRIVATE
+}
+
 enum class OpticsTarget {
   ISO,
   LENS,
diff --git a/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/Compilation.kt b/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/Compilation.kt
index d1f10b4c03..81793a4118 100644
--- a/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/Compilation.kt
+++ b/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/Compilation.kt
@@ -89,7 +89,7 @@ fun buildCompilation(
   this.sources = sources.toList()
   this.verbose = false
   this.allWarningsAsErrors = allWarningsAsErrors
-  this.languageVersion = "2.0"
+  this.languageVersion = "2.1"
   if (contextParameters) {
     this.kotlincArguments = listOf("-Xcontext-parameters")
   }
diff --git a/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/DSLTests.kt b/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/DSLTests.kt
index a3ad8c8739..c33f97b3ea 100755
--- a/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/DSLTests.kt
+++ b/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/DSLTests.kt
@@ -13,7 +13,7 @@ class DSLTests {
       |$dslModel
       |$dslValues
       |val modify = Employees.employees.every.company.notNull.address
-      |  .street.name.modify(employees, String::toUpperCase)
+      |  .street.name.modify(employees, String::uppercase)
       |val r = modify.employees.map { it.company?.address?.street?.name }.toString()
       """.evals("r" to "[LAMBDA STREET, LAMBDA STREET]")
   }
diff --git a/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/LensTests.kt b/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/LensTests.kt
index dbd5241ddd..652f36a0dd 100755
--- a/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/LensTests.kt
+++ b/arrow-libs/optics/arrow-optics-ksp-plugin/src/test/kotlin/arrow/optics/plugin/LensTests.kt
@@ -325,4 +325,23 @@ class LensTests {
       |val r = lens != null
       """.evals("r" to true)
   }
+
+  @Test
+  fun `Visibilities are correctly computed (#3869)`() {
+    """
+      |$`package`
+      |$imports
+      |@optics
+      |internal sealed interface Interface {
+      |  @optics
+      |  data class DataClass(val value: Int) : Interface {
+      |    companion object
+      |  }
+      |  companion object
+      |}
+      |
+      |internal val lens: Lens<Interface.DataClass, Int> = Interface.DataClass.value
+      |internal val r = lens != null
+      """.evals("r" to true)
+  }
 }
diff --git a/generator-scripts/tuple.generator.kts b/generator-scripts/tuple.generator.kts
index 36d04196df..fff41c82be 100644
--- a/generator-scripts/tuple.generator.kts
+++ b/generator-scripts/tuple.generator.kts
@@ -28,15 +28,15 @@ for (i in 2..maxTuple) {
 
   val letters = availableLetters.take(i + 1)
 
-  val diamond1 = "<${letters.joinToString { it.toUpperCase() }}>"
-  val diamond2 = "<${letters.dropLast(1).joinToString { it.toUpperCase() }}>"
+  val diamond1 = "<${letters.joinToString { it.uppercase() }}>"
+  val diamond2 = "<${letters.dropLast(1).joinToString { it.uppercase() }}>"
 
   val newLetter = availableLetters[i]
 
   val constructor = (letters.dropLast(1).map { "this.$it" } + newLetter).joinToString()
 
   fileContent.append(
-          "operator fun $diamond1 Tuple$i$diamond2.plus($newLetter: ${newLetter.toUpperCase()}): Tuple${i+1}$diamond1 = Tuple${i + 1}($constructor)"
+          "operator fun $diamond1 Tuple$i$diamond2.plus($newLetter: ${newLetter.uppercase()}): Tuple${i+1}$diamond1 = Tuple${i + 1}($constructor)"
   )
   fileContent.append("\n")
 
@@ -44,4 +44,4 @@ for (i in 2..maxTuple) {
 
 val fileLocation = "../modules/core/arrow-syntax/src/main/kotlin/arrow/syntax/collections/tuple.kt"
 
-File("tuple.kt").writeText(fileContent.toString())
\ No newline at end of file
+File("tuple.kt").writeText(fileContent.toString())