diff --git a/tpl/partials/partials.go b/tpl/partials/partials.go
index 58899fb77..be552ee30 100644
--- a/tpl/partials/partials.go
+++ b/tpl/partials/partials.go
@@ -234,6 +234,8 @@ func (ns *Namespace) IncludeCached(ctx context.Context, name string, context any
 			depsManagerShared = identity.NewManager()
 			ctx = tpl.Context.DependencyManagerScopedProvider.Set(ctx, depsManagerShared.(identity.DependencyManagerScopedProvider))
 		}
+		// Mark the ctx so templates.Defer can reject being called from a cached body.
+		ctx = tpl.Context.IsInPartialCached.Set(ctx, true)
 		r := ns.doInclude(ctx, keyString, ti, context)
 		if ns.deps.Conf.Watching() {
 			r.mangager = depsManagerShared
diff --git a/tpl/template.go b/tpl/template.go
index 848736267..1708adc75 100644
--- a/tpl/template.go
+++ b/tpl/template.go
@@ -55,6 +55,7 @@ const (
 	contextKeyIsInGoldmark
 	cntextKeyCurrentTemplateInfo
 	contextKeyPartialDecoratorIDStack
+	contextKeyIsInPartialCached
 )
 
 // Context manages values passed in the context to templates.
@@ -66,6 +67,7 @@ var Context = struct {
 	IsInGoldmark                       contexthelpers.ContextDispatcher[bool]
 	CurrentTemplate                    contexthelpers.ContextDispatcher[*CurrentTemplateInfo]
 	PartialDecoratorIDStack            contexthelpers.ContextDispatcher[*collections.Stack[*StringBool]]
+	IsInPartialCached                  contexthelpers.ContextDispatcher[bool]
 }{
 	DependencyManagerScopedProvider: contexthelpers.NewContextDispatcher[identity.DependencyManagerScopedProvider](contextKeyDependencyManagerScopedProvider),
 	DependencyScope:                 contexthelpers.NewContextDispatcher[int](contextKeyDependencyScope),
@@ -73,6 +75,7 @@ var Context = struct {
 	IsInGoldmark:                    contexthelpers.NewContextDispatcher[bool](contextKeyIsInGoldmark),
 	CurrentTemplate:                 contexthelpers.NewContextDispatcher[*CurrentTemplateInfo](cntextKeyCurrentTemplateInfo),
 	PartialDecoratorIDStack:         contexthelpers.NewContextDispatcher[*collections.Stack[*StringBool]](contextKeyPartialDecoratorIDStack),
+	IsInPartialCached:               contexthelpers.NewContextDispatcher[bool](contextKeyIsInPartialCached),
 }
 
 func init() {
diff --git a/tpl/templates/defer_integration_test.go b/tpl/templates/defer_integration_test.go
index f876b0b7e..4f67898bc 100644
--- a/tpl/templates/defer_integration_test.go
+++ b/tpl/templates/defer_integration_test.go
@@ -322,3 +322,48 @@ End.
 
 	b.AssertFileContent("public/index.html", "Home.", "Defer 1", "Defer 2", "Defer 3", "End.")
 }
+
+// See issue 13492.
+func TestDeferInsidePartialCachedShouldFail(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+-- layouts/home.html --
+Home.
+{{ partialCached "css.html" . }}
+-- layouts/partials/css.html --
+{{ with (templates.Defer (dict "key" "global")) }}
+ Defer
+{{ end }}
+`
+
+	b, err := hugolib.TestE(t, files)
+
+	b.Assert(err, qt.Not(qt.IsNil))
+	b.Assert(err.Error(), qt.Contains, "templates.Defer cannot be used inside a partialCached partial")
+}
+
+// Verifies that the partialCached ctx flag propagates through a regular partial call.
+// See issue 13492.
+func TestDeferTransitivelyInsidePartialCachedShouldFail(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+-- layouts/home.html --
+Home.
+{{ partialCached "outer.html" . }}
+-- layouts/partials/outer.html --
+{{ partial "inner.html" . }}
+-- layouts/partials/inner.html --
+{{ with (templates.Defer (dict "key" "global")) }}
+ Defer
+{{ end }}
+`
+
+	b, err := hugolib.TestE(t, files)
+
+	b.Assert(err, qt.Not(qt.IsNil))
+	b.Assert(err.Error(), qt.Contains, "templates.Defer cannot be used inside a partialCached partial")
+}
diff --git a/tpl/templates/templates.go b/tpl/templates/templates.go
index 8428ff252..ad8e08d92 100644
--- a/tpl/templates/templates.go
+++ b/tpl/templates/templates.go
@@ -53,11 +53,18 @@ func (ns *Namespace) Exists(name string) bool {
 }
 
 // Defer defers the execution of a template block.
-func (ns *Namespace) Defer(args ...any) (bool, error) {
+func (ns *Namespace) Defer(ctx context.Context, args ...any) (bool, error) {
 	// Prevent defer from being used in content adapters,
 	// that just doesn't work.
 	ns.deps.Site.CheckReady()
 
+	// Reject use inside a partialCached body: the cached output retains the
+	// deferred placeholder across rebuilds while the executions map is reset,
+	// which used to cause a panic in executeDeferredTemplates. See issue #13492.
+	if tpl.Context.IsInPartialCached.Get(ctx) {
+		return false, fmt.Errorf("templates.Defer cannot be used inside a partialCached partial; use partial instead, or move templates.Defer to the calling template")
+	}
+
 	if len(args) != 0 {
 		return false, fmt.Errorf("Defer does not take any arguments")
 	}