[Repo Assist] eng(sanitize): promote inline regexp to package-level var; add SanitizeString benchmark

internal/logger/sanitize/sanitize.go

@@ -49,14 +49,18 @@ var SecretPatterns = []*regexp.Regexp{
 	regexp.MustCompile(`(?i)"(token|password|passwd|pwd|apikey|api_key|api-key|secret|client_secret|api_secret|authorization|auth|key|private_key|public_key|credentials|credential|access_token|refresh_token|bearer_token)"\s*:\s*"[^"]{1,}"`),
 }
 
+// keyValueSplitPattern splits a key=value or key:value match at the separator.
+// Pre-compiled to avoid per-call regexp compilation inside SanitizeString.
+var keyValueSplitPattern = regexp.MustCompile(`[=:]\s*`)
+
 // SanitizeString replaces potential secrets in a string with [REDACTED]
 func SanitizeString(message string) string {
 	result := message
 	for _, pattern := range SecretPatterns {
 		result = pattern.ReplaceAllStringFunc(result, func(match string) string {
 			// Keep the prefix (key name) but redact the value
 			if strings.Contains(match, "=") || strings.Contains(match, ":") {
-				parts := regexp.MustCompile(`[=:]\s*`).Split(match, 2)
+				parts := keyValueSplitPattern.Split(match, 2)
 				if len(parts) == 2 {
 					return parts[0] + "=[REDACTED]"
 				}

internal/logger/sanitize/sanitize_test.go

@@ -640,3 +640,22 @@ func TestSanitizeArgsDoesNotLeakSecrets(t *testing.T) {
 	assert.Contains(t, resultStr, "GITHUB_TOKEN=ghp_...", "Truncated token should be present")
 	assert.Contains(t, resultStr, "API_KEY=test...", "Truncated API key should be present")
 }
+
+// BenchmarkSanitizeString measures the per-call cost of SanitizeString across
+// a clean message (no matches) and a message containing a secret token.
+func BenchmarkSanitizeString(b *testing.B) {
+clean := "Processing request for user 42 in repository owner/repo"
+withSecret := "Authorization: ghp_aBcDeFgHiJkLmNoPqRsTuVwXyZ1234567890 is set"
+
+b.Run("no_secrets", func(b *testing.B) {
+for i := 0; i < b.N; i++ {
+_ = SanitizeString(clean)
+}
+})
+
+b.Run("with_secret", func(b *testing.B) {
+for i := 0; i < b.N; i++ {
+_ = SanitizeString(withSecret)
+}
+})
+}