diff --git a/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.dark.css b/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.dark.css
index 9105fcf9294..6d16af33e75 100644
--- a/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.dark.css
+++ b/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.dark.css
@@ -82,4 +82,9 @@ body.dark {
 
 .dark .error-counter {
     color: #ff1010;
+}
+
+.dark .diagnostic-hover {
+    background-color: #3a3a3a;
+    color: #dfdfdf;
 }
\ No newline at end of file
diff --git a/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.white.css b/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.white.css
index 9ce8fcdb204..f6798dcea9c 100644
--- a/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.white.css
+++ b/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/colors.white.css
@@ -21,7 +21,7 @@
 }
 
 .white .keyword {
-    color: #8ba558;
+    color: rgb(203, 159, 52);
 }
 
 .white a.ref.selected {
@@ -71,4 +71,9 @@
 
 .white .error-counter {
     color: #f00;
+}
+
+.white .diagnostic-hover {
+    background-color: #eaeaea;
+    color: #000;
 }
\ No newline at end of file
diff --git a/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/style.css b/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/style.css
index b16547c6b93..4d7518fc330 100644
--- a/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/style.css
+++ b/compiler/fir/dump/resources/org/jetbrains/kotlin/fir/dump/style.css
@@ -62,4 +62,29 @@ a.ref {
 
 .error-counter {
     margin-left: 10px;
+}
+
+.error.diagnostic-hover-container {
+    position: relative;
+    display: inline-block;
+}
+
+.error:hover .diagnostic-hover {
+    visibility: visible;
+    text-decoration: none;
+    opacity: 1;
+}
+
+.diagnostic-hover {
+    visibility: hidden;
+
+    border-radius: 6px;
+    padding: 5px 5px;
+    position: absolute;
+    z-index: 1;
+    bottom: 100%;
+    left: 0;
+
+    opacity: 0;
+    transition: opacity 0.3s;
 }
\ No newline at end of file
diff --git a/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt b/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
index 5caa6e8d71e..c4caabebc6c 100644
--- a/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
+++ b/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
@@ -15,12 +15,15 @@ import org.jetbrains.kotlin.descriptors.Visibility
 import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.impl.FirDefaultPropertyAccessor
+import org.jetbrains.kotlin.fir.diagnostics.FirDiagnostic
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.expressions.impl.FirElseIfTrueCondition
 import org.jetbrains.kotlin.fir.expressions.impl.FirUnitExpression
 import org.jetbrains.kotlin.fir.references.*
 import org.jetbrains.kotlin.fir.references.impl.FirSimpleNamedReference
 import org.jetbrains.kotlin.fir.resolve.*
+import org.jetbrains.kotlin.fir.resolve.diagnostics.FirAmbiguityError
+import org.jetbrains.kotlin.fir.resolve.diagnostics.FirInapplicableCandidateError
 import org.jetbrains.kotlin.fir.symbols.*
 import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
@@ -31,6 +34,7 @@ import org.jetbrains.kotlin.ir.expressions.IrConstKind
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.calls.inference.model.NewConstraintError
 import org.jetbrains.kotlin.types.AbstractStrictEqualityTypeChecker
 import org.jetbrains.kotlin.types.Variance
 import java.io.File
@@ -575,14 +579,8 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
         }
     }
 
-
-    private fun FlowContent.generate(klass: FirRegularClass) {
-        inl()
-
-        declarationStatus(klass.status)
-
-
-        when (klass.classKind) {
+    private fun FlowContent.classKind(kind: ClassKind) {
+        when (kind) {
             ClassKind.CLASS -> keyword("class")
             ClassKind.INTERFACE -> keyword("interface")
             ClassKind.ENUM_CLASS -> keyword("enum class")
@@ -590,6 +588,13 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
             ClassKind.ANNOTATION_CLASS -> keyword("annotation class")
             ClassKind.OBJECT -> keyword("object")
         }
+    }
+
+    private fun FlowContent.generate(klass: FirRegularClass) {
+        inl()
+
+        declarationStatus(klass.status)
+        classKind(klass.classKind)
         ws
         anchoredName(klass.name, klass.classId.asString())
         if (klass.superTypeRefs.isNotEmpty()) {
@@ -946,6 +951,114 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
         }
     }
 
+    private fun FlowContent.describeVerbose(symbol: FirCallableSymbol<*>, fir: FirMemberFunction<*>) {
+        describeTypeParameters(fir)
+
+        fir.receiverTypeRef?.let {
+            +"("
+            generate(it)
+            +")."
+        }
+        symbolRef(symbol) {
+            +symbol.callableId.toString()
+        }
+        +"("
+        generateList(fir.valueParameters) {
+            generate(it.returnTypeRef)
+        }
+        +"): "
+        generate(fir.returnTypeRef)
+    }
+
+    private fun FlowContent.describeVerbose(symbol: FirCallableSymbol<*>, fir: FirVariable<*>) {
+        if (fir is FirTypeParametersOwner) describeTypeParameters(fir)
+
+        fir.receiverTypeRef?.let {
+            +"("
+            generate(it)
+            +")."
+        }
+        symbolRef(symbol) {
+            +symbol.callableId.toString()
+        }
+        +":"
+        generate(fir.returnTypeRef)
+    }
+
+    private fun FlowContent.describeTypeParameters(typeParameterContainer: FirTypeParametersOwner) {
+        if (typeParameterContainer.typeParameters.isEmpty()) return
+        +"<"
+        generateList(typeParameterContainer.typeParameters) {
+            generate(it.variance)
+            if (it.isReified) {
+                keyword("reified ")
+            }
+
+            simpleName(it.name)
+
+            if (it.bounds.isNotEmpty()) {
+                +": "
+                generateList(it.bounds) { bound ->
+                    generate(bound)
+                }
+            }
+        }
+        +"> "
+    }
+
+    private fun FlowContent.describeVerbose(symbol: FirBasedSymbol<*>) {
+        when (symbol) {
+            is FirClassLikeSymbol<*> ->
+                when (val fir = symbol.fir) {
+                    is FirRegularClass -> {
+                        declarationStatus(fir.status)
+                        classKind(fir.classKind)
+                        ws
+                        symbolRef(symbol) {
+                            +fir.classId.asString()
+                        }
+                        describeTypeParameters(fir)
+                    }
+                    is FirTypeAlias -> {
+                        keyword("typealias ")
+                        symbolRef(symbol) {
+                            +symbol.classId.asString()
+                        }
+                        describeTypeParameters(fir)
+                    }
+                    else -> +symbol.describe()
+                }
+            is FirCallableSymbol<*> -> {
+                when (val fir = symbol.fir) {
+                    is FirSimpleFunction -> {
+                        declarationStatus(fir.status)
+                        keyword("fun ")
+                        describeVerbose(symbol, fir)
+                    }
+                    is FirConstructor -> {
+                        declarationStatus(fir.status)
+                        keyword("constructor ")
+                        describeVerbose(symbol, fir)
+                    }
+                    is FirField -> {
+                        declarationStatus(fir.status)
+                        keyword("field ")
+                        describeVerbose(symbol, fir)
+                    }
+                    is FirProperty -> {
+                        declarationStatus(fir.status)
+                        if (fir.isVal)
+                            keyword("val ")
+                        else if (fir.isVar)
+                            keyword("var ")
+                        describeVerbose(symbol, fir)
+                    }
+                }
+            }
+            else -> +symbol.describe()
+        }
+    }
+
     private fun FlowContent.symbolRef(symbol: FirBasedSymbol<*>?, body: FlowContent.() -> Unit) {
         val (link, classes) = when (symbol) {
             null -> null to setOf()
@@ -960,6 +1073,58 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
         }
     }
 
+    private fun FlowContent.diagnosticHover(body: FlowContent.() -> Unit) {
+        span(classes = "diagnostic-hover") {
+            body()
+        }
+    }
+
+    private fun FlowContent.errorWithDiagnostic(body: FlowContent.() -> Unit) {
+        error {
+            classes = classes + "diagnostic-hover-container"
+            body()
+        }
+    }
+
+    private fun FlowContent.generate(diagnostic: FirDiagnostic) {
+        when (diagnostic) {
+            is FirInapplicableCandidateError -> {
+                for (candidate in diagnostic.candidates) {
+                    describeVerbose(candidate.symbol)
+                    br
+                    candidate.diagnostics.forEach { callDiagnostic ->
+                        when (callDiagnostic) {
+                            is NewConstraintError -> {
+                                ident()
+                                +"Lower: "
+                                generate(callDiagnostic.lowerType as ConeKotlinType)
+                                br
+                                ident()
+                                +"Upper: "
+                                generate(callDiagnostic.upperType as ConeKotlinType)
+                            }
+                            else -> {
+                                ident()
+                                callDiagnostic::class.qualifiedName?.let { +it }
+                                Unit
+                            }
+                        }
+                        br
+                    }
+                }
+            }
+            is FirAmbiguityError -> {
+                +"Ambiguity: "
+                br
+                for (candidate in diagnostic.candidates) {
+                    describeVerbose(candidate)
+                    br
+                }
+            }
+            else -> +diagnostic.reason
+        }
+    }
+
     private fun FlowContent.generate(reference: FirReference) {
         when (reference) {
             is FirSuperReference -> keyword("super")
@@ -972,9 +1137,11 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
                 }
             }
             is FirErrorNamedReference -> {
-                error {
-                    title = reference.diagnostic.reason
+                errorWithDiagnostic {
                     simpleName(reference.name)
+                    diagnosticHover {
+                        generate(reference.diagnostic)
+                    }
                 }
             }
             is FirSimpleNamedReference -> {
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt
index 6c6d98ecafc..135331669de 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt
@@ -349,7 +349,12 @@ class FirCallResolver(
             applicability < CandidateApplicability.SYNTHETIC_RESOLVED -> {
                 FirErrorNamedReferenceImpl(
                     source,
-                    FirInapplicableCandidateError(applicability, candidates.map { it.symbol })
+                    FirInapplicableCandidateError(applicability, candidates.map {
+                        FirInapplicableCandidateError.CandidateInfo(
+                            it.symbol,
+                            if (it.systemInitialized) it.system.diagnostics else emptyList()
+                        )
+                    })
                 )
             }
             candidates.size == 1 -> {
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Candidate.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Candidate.kt
index 8defdce804d..cff33319c4d 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Candidate.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Candidate.kt
@@ -67,9 +67,12 @@ class Candidate(
     private val baseSystem: ConstraintStorage,
     val callInfo: CallInfo
 ) {
+
+    var systemInitialized: Boolean = false
     val system by lazy {
         val system = bodyResolveComponents.inferenceComponents.createConstraintSystem()
         system.addOtherSystem(baseSystem)
+        systemInitialized = true
         system
     }
 
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/FirDiagnostics.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/FirDiagnostics.kt
index bdfb584c1ec..e6f6237c5e3 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/FirDiagnostics.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/FirDiagnostics.kt
@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.calls.model.KotlinCallDiagnostic
 
 class FirUnresolvedReferenceError(val name: Name? = null) : FirDiagnostic() {
     override val reason: String get() = "Unresolved reference" + if (name != null) ": ${name.asString()}" else ""
@@ -25,8 +26,13 @@ class FirUnresolvedNameError(val name: Name) : FirDiagnostic() {
     override val reason: String get() = "Unresolved name: $name"
 }
 
-class FirInapplicableCandidateError(val applicability: CandidateApplicability, val candidates: Collection<AbstractFirBasedSymbol<*>>) : FirDiagnostic() {
-    override val reason: String get() = "Inapplicable($applicability): ${candidates.map { describeSymbol(it) }}"
+class FirInapplicableCandidateError(
+    val applicability: CandidateApplicability,
+    val candidates: Collection<CandidateInfo>
+) : FirDiagnostic() {
+    data class CandidateInfo(val symbol: AbstractFirBasedSymbol<*>, val diagnostics: List<KotlinCallDiagnostic>)
+
+    override val reason: String get() = "Inapplicable($applicability): ${candidates.map { describeSymbol(it.symbol) }}"
 }
 
 class FirAmbiguityError(val name: Name, val candidates: Collection<AbstractFirBasedSymbol<*>>) : FirDiagnostic() {
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt
index 9471bb11ad6..83265a60af9 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt
@@ -53,7 +53,7 @@ class ErrorNodeDiagnosticCollectorComponent(collector: AbstractDiagnosticCollect
             is FirUnresolvedReferenceError -> FirErrors.UNRESOLVED_REFERENCE.onSource(source, diagnostic.name?.asString())
             is FirUnresolvedSymbolError -> FirErrors.UNRESOLVED_REFERENCE.onSource(source, diagnostic.classId.asString())
             is FirUnresolvedNameError -> FirErrors.UNRESOLVED_REFERENCE.onSource(source, diagnostic.name.asString())
-            is FirInapplicableCandidateError -> FirErrors.INAPPLICABLE_CANDIDATE.onSource(source, diagnostic.candidates)
+            is FirInapplicableCandidateError -> FirErrors.INAPPLICABLE_CANDIDATE.onSource(source, diagnostic.candidates.map { it.symbol })
             is FirAmbiguityError -> FirErrors.AMBIGUITY.onSource(source, diagnostic.candidates)
             is FirOperatorAmbiguityError -> FirErrors.ASSIGN_OPERATOR_AMBIGUITY.onSource(source, diagnostic.candidates)
             is FirVariableExpectedError -> Errors.VARIABLE_EXPECTED.onSource(source)