diff --git a/compiler/fir/analysis-tests/testData/extendedCheckers/RedundantSingleExpressionStringTemplateChecker.txt b/compiler/fir/analysis-tests/testData/extendedCheckers/RedundantSingleExpressionStringTemplateChecker.txt
index 33f8dbee0aa..9c66c0fa4b3 100644
--- a/compiler/fir/analysis-tests/testData/extendedCheckers/RedundantSingleExpressionStringTemplateChecker.txt
+++ b/compiler/fir/analysis-tests/testData/extendedCheckers/RedundantSingleExpressionStringTemplateChecker.txt
@@ -1,9 +1,9 @@
 FILE: RedundantSingleExpressionStringTemplateChecker.kt
     public final val x: R|kotlin/String| = String(Hello)
         public get(): R|kotlin/String|
-    public final val y: R|kotlin/String| = R|/x|.R|kotlin/Any.toString|()
+    public final val y: R|kotlin/String| = <strcat>(R|/x|.R|kotlin/Any.toString|())
         public get(): R|kotlin/String|
-    public final val z: R|kotlin/String| = R|/y|.R|kotlin/Any.hashCode|().R|kotlin/Any.toString|()
+    public final val z: R|kotlin/String| = <strcat>(R|/y|.R|kotlin/Any.hashCode|().R|kotlin/Any.toString|())
         public get(): R|kotlin/String|
     public final fun toString(x: R|kotlin/String|): R|kotlin/String| {
         ^toString <strcat>(String(IC), R|<local>/x|.R|kotlin/Any.toString|())
diff --git a/compiler/fir/analysis-tests/testData/extendedCheckers/UselessCallOnNotNullChecker/NotNullTypeChain.txt b/compiler/fir/analysis-tests/testData/extendedCheckers/UselessCallOnNotNullChecker/NotNullTypeChain.txt
index ba45e862468..8e2385f983a 100644
--- a/compiler/fir/analysis-tests/testData/extendedCheckers/UselessCallOnNotNullChecker/NotNullTypeChain.txt
+++ b/compiler/fir/analysis-tests/testData/extendedCheckers/UselessCallOnNotNullChecker/NotNullTypeChain.txt
@@ -2,7 +2,7 @@ FILE: NotNullTypeChain.kt
     public final val list1: R|kotlin/collections/List<kotlin/Int>| = R|kotlin/collections/listOf|<R|kotlin/Int|>(Int(1))
         public get(): R|kotlin/collections/List<kotlin/Int>|
     public final val list: R|kotlin/collections/List<kotlin/String>| = R|/list1|.R|kotlin/collections/orEmpty|<R|kotlin/Int|>().R|kotlin/collections/map|<R|kotlin/Int|, R|kotlin/String|>(<L> = map@fun <anonymous>(it: R|kotlin/Int|): R|kotlin/String| <kind=UNKNOWN>  {
-        ^ R|<local>/it|.R|kotlin/Any.toString|()
+        ^ <strcat>(R|<local>/it|.R|kotlin/Any.toString|())
     }
     )
         public get(): R|kotlin/collections/List<kotlin/String>|
diff --git a/compiler/fir/analysis-tests/testData/resolve/arguments/stringTemplates.txt b/compiler/fir/analysis-tests/testData/resolve/arguments/stringTemplates.txt
index c4fd97009c8..9e3baf7a4c5 100644
--- a/compiler/fir/analysis-tests/testData/resolve/arguments/stringTemplates.txt
+++ b/compiler/fir/analysis-tests/testData/resolve/arguments/stringTemplates.txt
@@ -8,5 +8,5 @@ FILE: stringTemplates.kt
     public final fun foo(s: R|kotlin/String|): R|kotlin/Unit| {
     }
     public final fun test(a: R|A|): R|kotlin/Unit| {
-        R|/foo|(R|<local>/a|.R|kotlin/Any.toString|())
+        R|/foo|(<strcat>(R|<local>/a|.R|kotlin/Any.toString|()))
     }
diff --git a/compiler/fir/raw-fir/raw-fir.common/src/org/jetbrains/kotlin/fir/builder/BaseFirBuilder.kt b/compiler/fir/raw-fir/raw-fir.common/src/org/jetbrains/kotlin/fir/builder/BaseFirBuilder.kt
index 5f6d441a0b8..be9bec961f1 100644
--- a/compiler/fir/raw-fir/raw-fir.common/src/org/jetbrains/kotlin/fir/builder/BaseFirBuilder.kt
+++ b/compiler/fir/raw-fir/raw-fir.common/src/org/jetbrains/kotlin/fir/builder/BaseFirBuilder.kt
@@ -386,7 +386,6 @@ abstract class BaseFirBuilder<T>(val baseSession: FirSession, val context: Conte
             source = base?.toFirSourceElement()
             // Fast-pass if there is no non-const string expressions
             if (!hasExpressions) return buildConstExpression(source, FirConstKind.String, sb.toString())
-            argumentList.arguments.singleOrNull()?.let { return it }
         }
     }
 
diff --git a/compiler/testData/codegen/box/strings/stringFromJavaPlus.kt b/compiler/testData/codegen/box/strings/stringFromJavaPlus.kt
index 94a6a0a5051..ce2912e851d 100644
--- a/compiler/testData/codegen/box/strings/stringFromJavaPlus.kt
+++ b/compiler/testData/codegen/box/strings/stringFromJavaPlus.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // TARGET_BACKEND: JVM
 // WITH_RUNTIME
 
diff --git a/compiler/testData/codegen/bytecodeText/inlineClasses/inlineClassInStringTemplate.kt b/compiler/testData/codegen/bytecodeText/inlineClasses/inlineClassInStringTemplate.kt
index 40ab8cce869..baf0e9511ca 100644
--- a/compiler/testData/codegen/bytecodeText/inlineClasses/inlineClassInStringTemplate.kt
+++ b/compiler/testData/codegen/bytecodeText/inlineClasses/inlineClassInStringTemplate.kt
@@ -1,5 +1,4 @@
 // !LANGUAGE: +InlineClasses
-// IGNORE_BACKEND_FIR: JVM_IR
 
 // FILE: Z.kt
 inline class Z(val value: Int)
diff --git a/compiler/testData/codegen/bytecodeText/stringOperations/kt42457_old.kt b/compiler/testData/codegen/bytecodeText/stringOperations/kt42457_old.kt
index e68d1e1070a..2f94fa9c7b3 100644
--- a/compiler/testData/codegen/bytecodeText/stringOperations/kt42457_old.kt
+++ b/compiler/testData/codegen/bytecodeText/stringOperations/kt42457_old.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // KOTLIN_CONFIGURATION_FLAGS: STRING_CONCAT=indy-with-constants
 // JVM_TARGET: 9
 // FILE: JavaClass.java
diff --git a/compiler/testData/codegen/bytecodeText/stringOperations/singleConcat.kt b/compiler/testData/codegen/bytecodeText/stringOperations/singleConcat.kt
index 25b0928e01a..e39f97ba536 100644
--- a/compiler/testData/codegen/bytecodeText/stringOperations/singleConcat.kt
+++ b/compiler/testData/codegen/bytecodeText/stringOperations/singleConcat.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun f(s: String) = "$s"
 
 fun g(s: String?) = "$s"
diff --git a/compiler/testData/ir/irText/expressions/stringTemplates.fir.txt b/compiler/testData/ir/irText/expressions/stringTemplates.fir.txt
index d8b414ae277..6101d3b3acc 100644
--- a/compiler/testData/ir/irText/expressions/stringTemplates.fir.txt
+++ b/compiler/testData/ir/irText/expressions/stringTemplates.fir.txt
@@ -74,8 +74,9 @@ FILE fqName:<root> fileName:/stringTemplates.kt
   PROPERTY name:test7 visibility:public modality:FINAL [val]
     FIELD PROPERTY_BACKING_FIELD name:test7 type:kotlin.String visibility:private [final,static]
       EXPRESSION_BODY
-        CALL 'public open fun toString (): kotlin.String [fake_override] declared in kotlin.String' type=kotlin.String origin=null
-          $this: CALL 'public final fun <get-test1> (): kotlin.String declared in <root>' type=kotlin.String origin=GET_PROPERTY
+        STRING_CONCATENATION type=kotlin.String
+          CALL 'public open fun toString (): kotlin.String [fake_override] declared in kotlin.String' type=kotlin.String origin=null
+            $this: CALL 'public final fun <get-test1> (): kotlin.String declared in <root>' type=kotlin.String origin=GET_PROPERTY
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test7> visibility:public modality:FINAL <> () returnType:kotlin.String
       correspondingProperty: PROPERTY name:test7 visibility:public modality:FINAL [val]
       BLOCK_BODY
@@ -84,8 +85,9 @@ FILE fqName:<root> fileName:/stringTemplates.kt
   PROPERTY name:test8 visibility:public modality:FINAL [val]
     FIELD PROPERTY_BACKING_FIELD name:test8 type:kotlin.String visibility:private [final,static]
       EXPRESSION_BODY
-        CALL 'public open fun toString (): kotlin.String [fake_override] declared in kotlin.String' type=kotlin.String origin=null
-          $this: CALL 'public final fun foo (): kotlin.String declared in <root>' type=kotlin.String origin=null
+        STRING_CONCATENATION type=kotlin.String
+          CALL 'public open fun toString (): kotlin.String [fake_override] declared in kotlin.String' type=kotlin.String origin=null
+            $this: CALL 'public final fun foo (): kotlin.String declared in <root>' type=kotlin.String origin=null
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test8> visibility:public modality:FINAL <> () returnType:kotlin.String
       correspondingProperty: PROPERTY name:test8 visibility:public modality:FINAL [val]
       BLOCK_BODY
@@ -94,8 +96,9 @@ FILE fqName:<root> fileName:/stringTemplates.kt
   PROPERTY name:test9 visibility:public modality:FINAL [val]
     FIELD PROPERTY_BACKING_FIELD name:test9 type:kotlin.String visibility:private [final,static]
       EXPRESSION_BODY
-        CALL 'public open fun toString (): kotlin.String [fake_override] declared in kotlin.Int' type=kotlin.String origin=null
-          $this: CALL 'public final fun <get-x> (): kotlin.Int declared in <root>' type=kotlin.Int origin=GET_PROPERTY
+        STRING_CONCATENATION type=kotlin.String
+          CALL 'public open fun toString (): kotlin.String [fake_override] declared in kotlin.Int' type=kotlin.String origin=null
+            $this: CALL 'public final fun <get-x> (): kotlin.Int declared in <root>' type=kotlin.Int origin=GET_PROPERTY
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test9> visibility:public modality:FINAL <> () returnType:kotlin.String
       correspondingProperty: PROPERTY name:test9 visibility:public modality:FINAL [val]
       BLOCK_BODY