diff --git a/shortcuts/common/runner.go b/shortcuts/common/runner.go
index aa535af0..2fbe9141 100644
--- a/shortcuts/common/runner.go
+++ b/shortcuts/common/runner.go
@@ -73,11 +73,20 @@ func (ctx *RuntimeContext) IsBot() bool {
 // UserOpenId returns the current user's open_id from config.
 func (ctx *RuntimeContext) UserOpenId() string { return ctx.Config.UserOpenId }
 
-// Lang returns the user's preference as a canonical locale, or "" if unset or
-// unrecognized; callers choose their own fallback.
+// Lang returns the user's preference as a canonical locale.
+// Empty stays empty (unset). Any non-empty stored value that does not resolve
+// via i18n.Parse (e.g. legacy ko_kr / fr_fr from before the catalog was
+// shrunk to zh/en/ja) is silently coerced to LangZhCN — existing configs
+// stay readable, just behave as zh.
 func (ctx *RuntimeContext) Lang() i18n.Lang {
-	lang, _ := i18n.Parse(string(ctx.Config.Lang))
-	return lang
+	raw := string(ctx.Config.Lang)
+	if raw == "" {
+		return ""
+	}
+	if lang, ok := i18n.Parse(raw); ok {
+		return lang
+	}
+	return i18n.LangZhCN
 }
 
 // BotInfo holds bot identity metadata fetched lazily from /bot/v3/info.
diff --git a/shortcuts/common/runner_lang_test.go b/shortcuts/common/runner_lang_test.go
index 9efd0eb6..4cbe6ec8 100644
--- a/shortcuts/common/runner_lang_test.go
+++ b/shortcuts/common/runner_lang_test.go
@@ -20,7 +20,13 @@ func TestRuntimeContext_Lang(t *testing.T) {
 		{"legacy short value normalizes", "ja", i18n.LangJaJP},
 		{"legacy short zh normalizes", "zh", i18n.LangZhCN},
 		{"unset stays empty", "", ""},
-		{"unrecognized stays empty", "klingon", ""},
+		// Flipped semantics: unrecognized non-empty values are now treated
+		// as legacy storage from the pre-2026-05-28 14-language catalog
+		// and silently coerced to LangZhCN, not left empty.
+		{"unrecognized garbage coerces to zh", "klingon", i18n.LangZhCN},
+		{"legacy ko_kr coerces to zh", "ko_kr", i18n.LangZhCN},
+		{"legacy fr_fr coerces to zh", "fr_fr", i18n.LangZhCN},
+		{"legacy short ko coerces to zh", "ko", i18n.LangZhCN},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {