diff --git a/compiler/testData/codegen/box/builderInference/issues/kt54400a.kt b/compiler/testData/codegen/box/builderInference/issues/kt54400a.kt
new file mode 100644
index 00000000000..4bba0b0b267
--- /dev/null
+++ b/compiler/testData/codegen/box/builderInference/issues/kt54400a.kt
@@ -0,0 +1,26 @@
+// ISSUE: KT-54400
+
+// IGNORE_LIGHT_ANALYSIS
+// IGNORE_BACKEND: ANY
+// REASON: red code (see corresponding diagnostic test)
+
+fun box(): String {
+    build {
+        typeVariableMutableProperty = ""
+    }
+    return "OK"
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = "" as TV
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/codegen/box/builderInference/issues/kt54400b.kt b/compiler/testData/codegen/box/builderInference/issues/kt54400b.kt
new file mode 100644
index 00000000000..8ded81226e7
--- /dev/null
+++ b/compiler/testData/codegen/box/builderInference/issues/kt54400b.kt
@@ -0,0 +1,26 @@
+// ISSUE: KT-54400
+
+// IGNORE_LIGHT_ANALYSIS
+// IGNORE_BACKEND: ANY
+// REASON: red code (see corresponding diagnostic test)
+
+fun box(): String {
+    build {
+        typeVariableMutableProperty = 42
+    }
+    return "OK"
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = 42 as TV
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/codegen/box/builderInference/issues/kt54400c.kt b/compiler/testData/codegen/box/builderInference/issues/kt54400c.kt
new file mode 100644
index 00000000000..fdd3ceca765
--- /dev/null
+++ b/compiler/testData/codegen/box/builderInference/issues/kt54400c.kt
@@ -0,0 +1,26 @@
+// ISSUE: KT-54400
+
+// IGNORE_LIGHT_ANALYSIS
+// IGNORE_BACKEND: ANY
+// REASON: red code (see corresponding diagnostic test)
+
+fun box(): String {
+    build {
+        typeVariableMutableProperty = {}
+    }
+    return "OK"
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = {} as TV
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/diagnostics/tests/builderInference/issues/kt54400a.fir.kt b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400a.fir.kt
new file mode 100644
index 00000000000..5e4816d6194
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400a.fir.kt
@@ -0,0 +1,25 @@
+// ISSUE: KT-54400
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>build<!> {
+        typeVariableMutableProperty = ""
+    }
+    // exact type equality check — turns unexpected compile-time behavior into red code
+    // considered to be non-user-reproducible code for the purposes of these tests
+    <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>checkExactType<!><<!CANNOT_INFER_PARAMETER_TYPE!>Buildee<String><!>>(buildee)
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/diagnostics/tests/builderInference/issues/kt54400a.kt b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400a.kt
new file mode 100644
index 00000000000..8923678043a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400a.kt
@@ -0,0 +1,25 @@
+// ISSUE: KT-54400
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>build<!> {
+        typeVariableMutableProperty = <!TYPE_MISMATCH("TypeVariable(PTV); String")!>""<!>
+    }
+    // exact type equality check — turns unexpected compile-time behavior into red code
+    // considered to be non-user-reproducible code for the purposes of these tests
+    checkExactType<Buildee<String>>(<!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>buildee<!>)
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/diagnostics/tests/builderInference/issues/kt54400b.fir.kt b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400b.fir.kt
new file mode 100644
index 00000000000..9e37b8906ad
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400b.fir.kt
@@ -0,0 +1,25 @@
+// ISSUE: KT-54400
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>build<!> {
+        typeVariableMutableProperty = 42
+    }
+    // exact type equality check — turns unexpected compile-time behavior into red code
+    // considered to be non-user-reproducible code for the purposes of these tests
+    <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>checkExactType<!><<!CANNOT_INFER_PARAMETER_TYPE!>Buildee<Int><!>>(buildee)
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/diagnostics/tests/builderInference/issues/kt54400b.kt b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400b.kt
new file mode 100644
index 00000000000..c9b68318ed0
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400b.kt
@@ -0,0 +1,25 @@
+// ISSUE: KT-54400
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>build<!> {
+        typeVariableMutableProperty = <!TYPE_MISMATCH("TypeVariable(PTV); Int")!>42<!>
+    }
+    // exact type equality check — turns unexpected compile-time behavior into red code
+    // considered to be non-user-reproducible code for the purposes of these tests
+    checkExactType<Buildee<Int>>(<!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>buildee<!>)
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/diagnostics/tests/builderInference/issues/kt54400c.fir.kt b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400c.fir.kt
new file mode 100644
index 00000000000..f725c076192
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400c.fir.kt
@@ -0,0 +1,25 @@
+// ISSUE: KT-54400
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>build<!> {
+        typeVariableMutableProperty = {}
+    }
+    // exact type equality check — turns unexpected compile-time behavior into red code
+    // considered to be non-user-reproducible code for the purposes of these tests
+    <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>checkExactType<!><<!CANNOT_INFER_PARAMETER_TYPE!>Buildee<() -> Unit><!>>(buildee)
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}
diff --git a/compiler/testData/diagnostics/tests/builderInference/issues/kt54400c.kt b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400c.kt
new file mode 100644
index 00000000000..117d0b4592d
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/builderInference/issues/kt54400c.kt
@@ -0,0 +1,25 @@
+// ISSUE: KT-54400
+// CHECK_TYPE_WITH_EXACT
+
+fun test() {
+    val buildee = <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>build<!> {
+        typeVariableMutableProperty = <!TYPE_MISMATCH("TypeVariable(PTV); () -> Unit")!>{}<!>
+    }
+    // exact type equality check — turns unexpected compile-time behavior into red code
+    // considered to be non-user-reproducible code for the purposes of these tests
+    checkExactType<Buildee<() -> Unit>>(<!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>buildee<!>)
+}
+
+
+
+
+class Buildee<TV> {
+    var typeVariableMutableProperty: TV
+        get() = storage
+        set(value) { storage = value }
+    private var storage: TV = null!!
+}
+
+fun <PTV> build(instructions: Buildee<PTV>.() -> Unit): Buildee<PTV> {
+    return Buildee<PTV>().apply(instructions)
+}