diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java
index e63edac73bd..39a465091d2 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java
@@ -26519,24 +26519,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31670_compat.kt")
-                public void testKt31670_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt31758.kt")
                 public void testKt31758() throws Exception {
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31758_compat.kt")
-                public void testKt31758_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt37692.kt")
                 public void testKt37692() throws Exception {
@@ -26561,12 +26549,6 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt");
                 }
 
-                @Test
-                @TestMetadata("overloadResolutionOnNullableContravariantParameter_compat.kt")
-                public void testOverloadResolutionOnNullableContravariantParameter_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("varargWithMoreSpecificSignature.kt")
                 public void testVarargWithMoreSpecificSignature() throws Exception {
diff --git a/compiler/config/src/org/jetbrains/kotlin/config/AnalysisFlags.kt b/compiler/config/src/org/jetbrains/kotlin/config/AnalysisFlags.kt
index 367168cdd5b..6dfeff3d688 100644
--- a/compiler/config/src/org/jetbrains/kotlin/config/AnalysisFlags.kt
+++ b/compiler/config/src/org/jetbrains/kotlin/config/AnalysisFlags.kt
@@ -33,9 +33,6 @@ object AnalysisFlags {
     @JvmStatic
     val explicitApiMode by AnalysisFlag.Delegates.ApiModeDisabledByDefault
 
-    @JvmStatic
-    val constraintSystemForOverloadResolution by AnalysisFlag.Delegates.ConstraintSystemForOverloadResolution
-
     @JvmStatic
     val ideMode by AnalysisFlag.Delegates.Boolean
 
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java
index 31bdbc0f2a3..3aa574c1e63 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java
@@ -26519,24 +26519,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31670_compat.kt")
-                public void testKt31670_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt31758.kt")
                 public void testKt31758() throws Exception {
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31758_compat.kt")
-                public void testKt31758_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt37692.kt")
                 public void testKt37692() throws Exception {
@@ -26561,12 +26549,6 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt");
                 }
 
-                @Test
-                @TestMetadata("overloadResolutionOnNullableContravariantParameter_compat.kt")
-                public void testOverloadResolutionOnNullableContravariantParameter_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("varargWithMoreSpecificSignature.kt")
                 public void testVarargWithMoreSpecificSignature() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java
index fa0d3e5ab9d..d28c8d06d2b 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java
@@ -26519,24 +26519,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31670_compat.kt")
-                public void testKt31670_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt31758.kt")
                 public void testKt31758() throws Exception {
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31758_compat.kt")
-                public void testKt31758_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt37692.kt")
                 public void testKt37692() throws Exception {
@@ -26561,12 +26549,6 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt");
                 }
 
-                @Test
-                @TestMetadata("overloadResolutionOnNullableContravariantParameter_compat.kt")
-                public void testOverloadResolutionOnNullableContravariantParameter_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("varargWithMoreSpecificSignature.kt")
                 public void testVarargWithMoreSpecificSignature() throws Exception {
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionStatelessCallbacksImpl.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionStatelessCallbacksImpl.kt
index 7e37d724152..762370f6b7e 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionStatelessCallbacksImpl.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/KotlinResolutionStatelessCallbacksImpl.kt
@@ -104,10 +104,5 @@ class KotlinResolutionStatelessCallbacksImpl(
 
     override fun createConstraintSystemForOverloadResolution(
         constraintInjector: ConstraintInjector, builtIns: KotlinBuiltIns
-    ): SimpleConstraintSystem {
-        return if (languageVersionSettings.getFlag(AnalysisFlags.constraintSystemForOverloadResolution).forNewInference())
-            SimpleConstraintSystemImpl(constraintInjector, builtIns, kotlinTypeRefiner, languageVersionSettings)
-        else
-            ConstraintSystemBuilderImpl.forSpecificity()
-    }
+    ): SimpleConstraintSystem = SimpleConstraintSystemImpl(constraintInjector, builtIns, kotlinTypeRefiner, languageVersionSettings)
 }
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
index 588cb7542f1..34c4e7c03df 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
@@ -78,7 +78,6 @@ import org.jetbrains.kotlin.types.expressions.unqualifiedSuper.UnqualifiedSuperK
 import org.jetbrains.kotlin.types.typeUtil.TypeUtilsKt;
 import org.jetbrains.kotlin.util.OperatorNameConventions;
 
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
diff --git a/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/builders/LanguageVersionSettingsBuilder.kt b/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/builders/LanguageVersionSettingsBuilder.kt
index 48a4fd1da57..239d0f9e928 100644
--- a/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/builders/LanguageVersionSettingsBuilder.kt
+++ b/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/builders/LanguageVersionSettingsBuilder.kt
@@ -65,7 +65,6 @@ class LanguageVersionSettingsBuilder {
         val analysisFlags = listOfNotNull(
             analysisFlag(AnalysisFlags.optIn, directives[LanguageSettingsDirectives.OPT_IN].takeIf { it.isNotEmpty() }),
             analysisFlag(AnalysisFlags.ignoreDataFlowInAssert, trueOrNull(LanguageSettingsDirectives.IGNORE_DATA_FLOW_IN_ASSERT in directives)),
-            analysisFlag(AnalysisFlags.constraintSystemForOverloadResolution, directives.singleOrZeroValue(LanguageSettingsDirectives.CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION)),
             analysisFlag(AnalysisFlags.allowResultReturnType, trueOrNull(LanguageSettingsDirectives.ALLOW_RESULT_RETURN_TYPE in directives)),
             analysisFlag(AnalysisFlags.explicitApiMode, directives.singleOrZeroValue(LanguageSettingsDirectives.EXPLICIT_API_MODE)),
             analysisFlag(AnalysisFlags.allowKotlinPackage, trueOrNull(LanguageSettingsDirectives.ALLOW_KOTLIN_PACKAGE in directives)),
diff --git a/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/directives/LanguageSettingsDirectives.kt b/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/directives/LanguageSettingsDirectives.kt
index 292bb82cc76..28afa134f18 100644
--- a/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/directives/LanguageSettingsDirectives.kt
+++ b/compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/directives/LanguageSettingsDirectives.kt
@@ -33,10 +33,6 @@ object LanguageSettingsDirectives : SimpleDirectivesContainer() {
         description = "Enables corresponding analysis flag (AnalysisFlags.ignoreDataFlowInAssert)"
     )
 
-    val CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION by enumDirective<ConstraintSystemForOverloadResolutionMode>(
-        description = "Configures corresponding analysis flag (AnalysisFlags.constraintSystemForOverloadResolution)",
-    )
-
     val ALLOW_RESULT_RETURN_TYPE by directive(
         description = "Allow using Result in return type position"
     )
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt
index 6d0e9e7093c..3a16dea873f 100644
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt
+++ b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt
@@ -1,5 +1,4 @@
 // FIR_IDENTICAL
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_NEW_INFERENCE
 
 open class A<T>(val value: T)
 class B<T>(value: T) : A<T>(value)
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.fir.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.fir.kt
deleted file mode 100644
index 085f867a73d..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.fir.kt
+++ /dev/null
@@ -1,15 +0,0 @@
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_OLD_INFERENCE
-
-open class A<T>(val value: T)
-class B<T>(value: T) : A<T>(value)
-
-fun <T> A<T>.foo(block: (T?) -> Unit) {
-    block(value)
-}
-fun <T> B<T>.foo(block: (T) -> Unit) {
-    block(value)
-}
-
-fun main() {
-    B("string").<!OVERLOAD_RESOLUTION_AMBIGUITY!>foo<!> {  }
-}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.kt
deleted file mode 100644
index 7479fd3db5b..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.kt
+++ /dev/null
@@ -1,15 +0,0 @@
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_OLD_INFERENCE
-
-open class A<T>(val value: T)
-class B<T>(value: T) : A<T>(value)
-
-fun <T> A<T>.foo(block: (T?) -> Unit) {
-    block(value)
-}
-fun <T> B<T>.foo(block: (T) -> Unit) {
-    block(value)
-}
-
-fun main() {
-    B("string").foo {  }
-}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.txt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.txt
deleted file mode 100644
index 81a675d81c0..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.txt
+++ /dev/null
@@ -1,21 +0,0 @@
-package
-
-public fun main(): kotlin.Unit
-public fun </*0*/ T> A<T>.foo(/*0*/ block: (T?) -> kotlin.Unit): kotlin.Unit
-public fun </*0*/ T> B<T>.foo(/*0*/ block: (T) -> kotlin.Unit): kotlin.Unit
-
-public open class A</*0*/ T> {
-    public constructor A</*0*/ T>(/*0*/ value: T)
-    public final val value: T
-    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}
-
-public final class B</*0*/ T> : A<T> {
-    public constructor B</*0*/ T>(/*0*/ value: T)
-    public final override /*1*/ /*fake_override*/ val value: T
-    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt
index df3c692342b..07fced92b67 100644
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt
+++ b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt
@@ -1,5 +1,4 @@
 // FIR_IDENTICAL
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_NEW_INFERENCE
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 
 // FILE: a.kt
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.fir.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.fir.kt
deleted file mode 100644
index 11bff181787..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.fir.kt
+++ /dev/null
@@ -1,25 +0,0 @@
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_OLD_INFERENCE
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-
-// FILE: a.kt
-
-package a
-
-enum class A { A1 }
-
-fun <T : Enum<T>> foo(arg: T.() -> Unit) = 1
-
-// FILE: b.kt
-
-package b
-
-fun <T : Any> foo(arg: T.() -> Unit) = 2
-
-// FILE: test.kt
-
-import a.*
-import b.*
-
-fun test() {
-    <!OVERLOAD_RESOLUTION_AMBIGUITY!>foo<!><A> { }
-}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.kt
deleted file mode 100644
index 522128fc864..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.kt
+++ /dev/null
@@ -1,25 +0,0 @@
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_OLD_INFERENCE
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-
-// FILE: a.kt
-
-package a
-
-enum class A { A1 }
-
-fun <T : Enum<T>> foo(arg: T.() -> Unit) = 1
-
-// FILE: b.kt
-
-package b
-
-fun <T : Any> foo(arg: T.() -> Unit) = 2
-
-// FILE: test.kt
-
-import a.*
-import b.*
-
-fun test() {
-    foo<A> { }
-}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.txt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.txt
deleted file mode 100644
index ef13b0a8e93..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.txt
+++ /dev/null
@@ -1,30 +0,0 @@
-package
-
-public fun test(): kotlin.Unit
-
-package a {
-    public fun </*0*/ T : kotlin.Enum<T>> foo(/*0*/ arg: T.() -> kotlin.Unit): kotlin.Int
-
-    public final enum class A : kotlin.Enum<a.A> {
-        enum entry A1
-
-        private constructor A()
-        @kotlin.internal.IntrinsicConstEvaluation public final override /*1*/ /*fake_override*/ val name: kotlin.String
-        public final override /*1*/ /*fake_override*/ val ordinal: kotlin.Int
-        protected final override /*1*/ /*fake_override*/ fun clone(): kotlin.Any
-        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: a.A): kotlin.Int
-        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-        protected/*protected and package*/ final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun finalize(): kotlin.Unit
-        public final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun getDeclaringClass(): java.lang.Class<a.A!>!
-        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-
-        // Static members
-        public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): a.A
-        public final /*synthesized*/ fun values(): kotlin.Array<a.A>
-    }
-}
-
-package b {
-    public fun </*0*/ T : kotlin.Any> foo(/*0*/ arg: T.() -> kotlin.Unit): kotlin.Int
-}
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt
index 1b7425de03c..71075b029e3 100644
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt
+++ b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt
@@ -1,5 +1,4 @@
 // FIR_IDENTICAL
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_NEW_INFERENCE
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 
 // FILE: a.kt
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.fir.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.fir.kt
deleted file mode 100644
index 5fceb00561e..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.fir.kt
+++ /dev/null
@@ -1,23 +0,0 @@
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_OLD_INFERENCE
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-
-// FILE: a.kt
-
-package a
-
-fun <T> foo(block: (T?) -> Unit) {}
-
-// FILE: b.kt
-
-package b
-
-fun <K> foo(block: (K) -> Unit) {}
-
-// FILE: test.kt
-
-import a.*
-import b.*
-
-fun main() {
-    foo<String> {  }
-}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.kt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.kt
deleted file mode 100644
index 2ae1cbf0c8a..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.kt
+++ /dev/null
@@ -1,23 +0,0 @@
-// !CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION: CONSTRAINT_SYSTEM_FOR_OLD_INFERENCE
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-
-// FILE: a.kt
-
-package a
-
-fun <T> foo(block: (T?) -> Unit) {}
-
-// FILE: b.kt
-
-package b
-
-fun <K> foo(block: (K) -> Unit) {}
-
-// FILE: test.kt
-
-import a.*
-import b.*
-
-fun main() {
-    <!OVERLOAD_RESOLUTION_AMBIGUITY!>foo<!><String> {  }
-}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.txt b/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.txt
deleted file mode 100644
index 607442c7911..00000000000
--- a/compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.txt
+++ /dev/null
@@ -1,11 +0,0 @@
-package
-
-public fun main(): kotlin.Unit
-
-package a {
-    public fun </*0*/ T> foo(/*0*/ block: (T?) -> kotlin.Unit): kotlin.Unit
-}
-
-package b {
-    public fun </*0*/ K> foo(/*0*/ block: (K) -> kotlin.Unit): kotlin.Unit
-}
diff --git a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
index f441e8abbf6..eae4994d1f0 100644
--- a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
+++ b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
@@ -26531,24 +26531,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31670_compat.kt")
-                public void testKt31670_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31670_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt31758.kt")
                 public void testKt31758() throws Exception {
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758.kt");
                 }
 
-                @Test
-                @TestMetadata("kt31758_compat.kt")
-                public void testKt31758_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt31758_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("kt37692.kt")
                 public void testKt37692() throws Exception {
@@ -26573,12 +26561,6 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter.kt");
                 }
 
-                @Test
-                @TestMetadata("overloadResolutionOnNullableContravariantParameter_compat.kt")
-                public void testOverloadResolutionOnNullableContravariantParameter_compat() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/resolve/overloadConflicts/overloadResolutionOnNullableContravariantParameter_compat.kt");
-                }
-
                 @Test
                 @TestMetadata("varargWithMoreSpecificSignature.kt")
                 public void testVarargWithMoreSpecificSignature() throws Exception {
diff --git a/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/CompilerTestLanguageVersionSettings.kt b/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/CompilerTestLanguageVersionSettings.kt
index 57f5d1c595a..e6e234dde5f 100644
--- a/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/CompilerTestLanguageVersionSettings.kt
+++ b/compiler/tests-common/tests/org/jetbrains/kotlin/checkers/CompilerTestLanguageVersionSettings.kt
@@ -23,7 +23,6 @@ const val SKIP_METADATA_VERSION_CHECK = "SKIP_METADATA_VERSION_CHECK"
 const val ALLOW_RESULT_RETURN_TYPE = "ALLOW_RESULT_RETURN_TYPE"
 const val INHERIT_MULTIFILE_PARTS = "INHERIT_MULTIFILE_PARTS"
 const val SANITIZE_PARENTHESES = "SANITIZE_PARENTHESES"
-const val CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION = "CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION"
 const val ENABLE_JVM_PREVIEW = "ENABLE_JVM_PREVIEW"
 
 data class CompilerTestLanguageVersionSettings(
@@ -67,9 +66,6 @@ fun parseLanguageVersionSettings(directives: Directives): CompilerTestLanguageVe
         analysisFlag(JvmAnalysisFlags.inheritMultifileParts, if (INHERIT_MULTIFILE_PARTS in directives) true else null),
         analysisFlag(JvmAnalysisFlags.sanitizeParentheses, if (SANITIZE_PARENTHESES in directives) true else null),
         analysisFlag(JvmAnalysisFlags.enableJvmPreview, if (ENABLE_JVM_PREVIEW in directives) true else null),
-        analysisFlag(AnalysisFlags.constraintSystemForOverloadResolution, directives[CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION]?.let {
-            ConstraintSystemForOverloadResolutionMode.valueOf(it)
-        }),
         analysisFlag(AnalysisFlags.explicitApiVersion, if (apiVersionString != null) true else null)
     )
 
diff --git a/compiler/util/src/org/jetbrains/kotlin/config/AnalysisFlag.kt b/compiler/util/src/org/jetbrains/kotlin/config/AnalysisFlag.kt
index 4d1a20ddfb1..022d6067d56 100644
--- a/compiler/util/src/org/jetbrains/kotlin/config/AnalysisFlag.kt
+++ b/compiler/util/src/org/jetbrains/kotlin/config/AnalysisFlag.kt
@@ -36,10 +36,5 @@ class AnalysisFlag<out T> internal constructor(
         object ListOfStrings {
             operator fun provideDelegate(instance: Any?, property: KProperty<*>) = Delegate(property.name, emptyList<String>())
         }
-
-        object ConstraintSystemForOverloadResolution {
-            operator fun provideDelegate(instance: Any?, property: KProperty<*>) =
-                Delegate(property.name, ConstraintSystemForOverloadResolutionMode.CONSTRAINT_SYSTEM_FOR_NEW_INFERENCE)
-        }
     }
 }