Ensure ToTitle only capitalizes the first char

internal/string.go

@@ -61,5 +61,5 @@ func CharAt(s string, i int) byte {
 // to its title case.
 func ToTitle(m string) string {
 	r, size := utf8.DecodeRuneInString(m)
-	return string(unicode.ToTitle(r)) + m[size:]
+	return string(unicode.ToTitle(r)) + strings.ToLower(m[size:])
 }

strcase/sentence.go

@@ -45,15 +45,17 @@ func NewSentenceConverter(opts ...CaseOptFunc) *SentenceConverter {
 func (sc *SentenceConverter) Convert(s string) string {
 	var made []string
 
-	s = strings.ToLower(s)
-
 	ps := `[\p{N}\p{L}*]+[^\s]*`
 	if len(sc.vocab) > 0 {
 		ps = fmt.Sprintf(`\b(?:%s)\b|%s`, strings.Join(sc.vocab, "|"), ps)
 	}
 	re := regexp2.MustCompileStd(`(?i)` + ps)
 
 	tokens := re.FindAllString(s, -1)
+	// NOTE: We have to do this *after* tokenizing the string in order to
+	// respect the case of would-be exceptions.
+	s = strings.ToLower(s)
+
 	for i, token := range tokens {
 		prev := ""
 		if i-1 >= 0 {

strcase/sentence_test.go

@@ -19,6 +19,7 @@ var vocabCases = []testCase{
 	{"Getting started with vale server", "Getting started with Vale Server"},
 	{"Issue triage", "Issue triage"},
 	{"macOS 15: What's new", "macOS 15: What's new"},
+	{"Configuration", "Configuration"},
 }
 
 func TestSentence(t *testing.T) {
@@ -36,6 +37,7 @@ func TestVocab(t *testing.T) {
 		"Vale Server",
 		"I",
 		"macOS",
+		"[Cc]onfig",
 	}))
 
 	for _, test := range vocabCases {