Harden prompt debug redaction

internal/promptdebug/debug_writer.go

@@ -171,7 +171,7 @@ func (w *PromptDebugWriter) WritePreparation(ref PromptDebugRef, preparation pro
 		artifact.RenderedMessages = promptDebugMessages(debug.RenderedMessages)
 		artifact.StructuredSchema = copyRawJSON(debug.StructuredSchema)
 		artifact.Endpoint = safePromptDebugEndpoint(debug.Endpoint)
-		parameters, err := redactPromptDebugParameters(debug.ParametersJSON)
+		parameters, err := safePromptDebugParameters(debug.ParametersJSON)
 		if err != nil {
 			return "", err
 		}
@@ -404,55 +404,55 @@ func copyRawJSON(value []byte) json.RawMessage {
 
 func safePromptDebugEndpoint(value string) string {
 	parsed, err := url.Parse(value)
-	if err != nil {
+	if err != nil || parsed.Scheme == "" || parsed.Host == "" {
 		return ""
 	}
-	parsed.User = nil
-	parameters := parsed.Query()
-	for key := range parameters {
-		if isPromptDebugSecretKey(key) {
-			parameters[key] = []string{"[redacted]"}
-		}
-	}
-	parsed.RawQuery = parameters.Encode()
-	parsed.Fragment = ""
-	return parsed.String()
+	return (&url.URL{Scheme: parsed.Scheme, Host: parsed.Host}).String()
 }
 
-func redactPromptDebugParameters(value []byte) (json.RawMessage, error) {
+func safePromptDebugParameters(value []byte) (json.RawMessage, error) {
 	if len(value) == 0 {
 		return nil, nil
 	}
-	var decoded any
+	var decoded map[string]json.RawMessage
 	if err := json.Unmarshal(value, &decoded); err != nil {
-		return nil, fmt.Errorf("decode prompt debug parameters: %w", err)
+		return nil, fmt.Errorf("prompt debug parameters must be a JSON object")
 	}
-	redactPromptDebugValue(decoded)
-	encoded, err := json.Marshal(decoded)
+	parameters := make(map[string]json.RawMessage)
+	for _, field := range []struct {
+		name  string
+		value func(json.RawMessage) bool
+	}{
+		{name: "temperature", value: promptDebugJSONNumber},
+		{name: "max_tokens", value: promptDebugJSONInteger},
+		{name: "top_p", value: promptDebugJSONNumber},
+		{name: "timeout_seconds", value: promptDebugJSONInteger},
+		{name: "service_tier", value: promptDebugJSONString},
+		{name: "reasoning_effort", value: promptDebugJSONString},
+	} {
+		value, ok := decoded[field.name]
+		if ok && field.value(value) {
+			parameters[field.name] = append(json.RawMessage(nil), value...)
+		}
+	}
+	encoded, err := json.Marshal(parameters)
 	if err != nil {
-		return nil, fmt.Errorf("encode prompt debug parameters: %w", err)
+		return nil, fmt.Errorf("encode safe prompt debug parameters: %w", err)
 	}
 	return encoded, nil
 }
 
-func redactPromptDebugValue(value any) {
-	switch typed := value.(type) {
-	case map[string]any:
-		for key, item := range typed {
-			if isPromptDebugSecretKey(key) {
-				typed[key] = "[redacted]"
-				continue
-			}
-			redactPromptDebugValue(item)
-		}
-	case []any:
-		for _, item := range typed {
-			redactPromptDebugValue(item)
-		}
-	}
+func promptDebugJSONNumber(value json.RawMessage) bool {
+	var decoded float64
+	return json.Unmarshal(value, &decoded) == nil
 }
 
-func isPromptDebugSecretKey(key string) bool {
-	normalized := strings.NewReplacer("_", "", "-", "", " ", "").Replace(strings.ToLower(key))
-	return strings.Contains(normalized, "credential") || strings.Contains(normalized, "secret") || strings.Contains(normalized, "password") || strings.Contains(normalized, "token") || strings.Contains(normalized, "apikey") || strings.Contains(normalized, "authorization")
+func promptDebugJSONInteger(value json.RawMessage) bool {
+	var decoded int
+	return json.Unmarshal(value, &decoded) == nil
+}
+
+func promptDebugJSONString(value json.RawMessage) bool {
+	var decoded string
+	return json.Unmarshal(value, &decoded) == nil
 }