refactor(telegram): reduce code duplication and improve readability

- Extract parseTelegramTarget helper to consolidate duplicated @username
  vs numeric chat ID parsing from 6+ locations (builder functions,
  sendTelegramTextReturnMessage, sendTelegramAttachmentImpl)
- Extract Config.baseURL() to eliminate duplicate base URL resolution
  between apiEndpoint() and fileEndpoint()
- Refactor stream.go Push method: extract resetStreamState(),
  deliverFinalText(), and per-event-type sub-methods (pushDelta,
  pushFinal, pushToolCallStart, pushAttachment, pushPhaseEnd,
  pushError), reducing the 200-line switch-case to a clean dispatcher
- Use pushFinal's existing getBot() instead of duplicating parseConfig +
  getOrCreateBot
- Replace sort.SliceStable with slices.SortStableFunc + cmp.Compare
- Replace strings.Index + manual slicing with strings.Cut in
  decodeDataURLBytes, ResolveAttachment, and parseTelegramUserInput

internal/channel/adapters/telegram/config.go

@@ -15,22 +15,23 @@ type Config struct {
 	APIBaseURL string // Reverse proxy base URL for regions where Telegram is blocked (e.g. China mainland)
 }
 
-// apiEndpoint returns the Sprintf-formatted API endpoint derived from the base URL.
-func (c Config) apiEndpoint() string {
+// baseURL returns the effective base URL with trailing slashes removed.
+func (c Config) baseURL() string {
 	base := c.APIBaseURL
 	if base == "" {
 		base = defaultAPIBaseURL
 	}
-	return strings.TrimRight(base, "/") + "/bot%s/%s"
+	return strings.TrimRight(base, "/")
+}
+
+// apiEndpoint returns the Sprintf-formatted API endpoint derived from the base URL.
+func (c Config) apiEndpoint() string {
+	return c.baseURL() + "/bot%s/%s"
 }
 
 // fileEndpoint returns the Sprintf-formatted file download endpoint derived from the base URL.
 func (c Config) fileEndpoint() string {
-	base := c.APIBaseURL
-	if base == "" {
-		base = defaultAPIBaseURL
-	}
-	return strings.TrimRight(base, "/") + "/file/bot%s/%s"
+	return c.baseURL() + "/file/bot%s/%s"
 }
 
 // UserConfig holds the identifiers used to target a Telegram user or group.

internal/channel/adapters/telegram/directory.go

@@ -222,11 +222,9 @@ func parseTelegramUserInput(input string) (chatID, userID int64) {
 	if input == "" {
 		return 0, 0
 	}
-	if idx := strings.Index(input, ":"); idx >= 0 {
-		left := strings.TrimSpace(input[:idx])
-		right := strings.TrimSpace(input[idx+1:])
-		cid, err1 := strconv.ParseInt(left, 10, 64)
-		uid, err2 := strconv.ParseInt(right, 10, 64)
+	if left, right, ok := strings.Cut(input, ":"); ok {
+		cid, err1 := strconv.ParseInt(strings.TrimSpace(left), 10, 64)
+		uid, err2 := strconv.ParseInt(strings.TrimSpace(right), 10, 64)
 		if err1 == nil && err2 == nil && cid != 0 && uid != 0 {
 			return cid, uid
 		}

internal/channel/adapters/telegram/stream.go

@@ -265,6 +265,188 @@ func (s *telegramOutboundStream) sendPermanentMessage(ctx context.Context, text
 	return sendTelegramText(bot, s.target, text, replyTo, parseMode)
 }
 
+// resetStreamState clears the streaming message state so a fresh message will
+// be created on the next delta. Must be called without holding s.mu.
+func (s *telegramOutboundStream) resetStreamState() {
+	s.mu.Lock()
+	s.streamMsgID = 0
+	if !s.isPrivateChat {
+		s.streamChatID = 0
+	}
+	s.lastEdited = ""
+	s.lastEditedAt = time.Time{}
+	s.buf.Reset()
+	s.mu.Unlock()
+}
+
+// deliverFinalText sends or edits the final text depending on chat mode.
+func (s *telegramOutboundStream) deliverFinalText(ctx context.Context, text, parseMode string) error {
+	if s.isPrivateChat {
+		return s.sendPermanentMessage(ctx, text, parseMode)
+	}
+	if err := s.ensureStreamMessage(ctx, text); err != nil {
+		return err
+	}
+	return s.editStreamMessageFinal(ctx, text)
+}
+
+func (s *telegramOutboundStream) pushToolCallStart(ctx context.Context) error {
+	s.mu.Lock()
+	bufText := strings.TrimSpace(s.buf.String())
+	hasMsg := s.streamMsgID != 0
+	s.mu.Unlock()
+	if s.isPrivateChat {
+		// In draft mode, send buffered text as a permanent message before tool execution.
+		if bufText != "" {
+			if err := s.sendPermanentMessage(ctx, bufText, ""); err != nil {
+				if s.adapter != nil && s.adapter.logger != nil {
+					s.adapter.logger.Warn("telegram: draft permanent message failed", slog.Any("error", err))
+				}
+			}
+		}
+	} else if hasMsg && bufText != "" {
+		_ = s.editStreamMessageFinal(ctx, bufText)
+	}
+	s.resetStreamState()
+	return nil
+}
+
+func (s *telegramOutboundStream) pushAttachment(ctx context.Context, event channel.StreamEvent) error {
+	if len(event.Attachments) == 0 {
+		return nil
+	}
+	bot, replyTo, err := s.getBotAndReply(ctx)
+	if err != nil {
+		return err
+	}
+	for _, att := range event.Attachments {
+		if sendErr := sendTelegramAttachmentWithAssets(ctx, bot, s.target, att, "", replyTo, "", s.adapter.assets); sendErr != nil {
+			if s.adapter != nil && s.adapter.logger != nil {
+				s.adapter.logger.Warn("telegram: stream attachment send failed",
+					slog.String("config_id", s.cfg.ID),
+					slog.String("type", string(att.Type)),
+					slog.Any("error", sendErr),
+				)
+			}
+		}
+	}
+	return nil
+}
+
+func (s *telegramOutboundStream) pushPhaseEnd(ctx context.Context, event channel.StreamEvent) error {
+	if event.Phase != channel.StreamPhaseText {
+		return nil
+	}
+	// In draft mode, skip phase-end finalization; StreamEventFinal sends the
+	// permanent formatted message.
+	if s.isPrivateChat {
+		return nil
+	}
+	s.mu.Lock()
+	finalText := strings.TrimSpace(s.buf.String())
+	s.mu.Unlock()
+	if finalText != "" {
+		if err := s.ensureStreamMessage(ctx, finalText); err != nil {
+			return err
+		}
+		return s.editStreamMessageFinal(ctx, finalText)
+	}
+	return nil
+}
+
+func (s *telegramOutboundStream) pushDelta(ctx context.Context, event channel.StreamEvent) error {
+	if event.Delta == "" || event.Phase == channel.StreamPhaseReasoning {
+		return nil
+	}
+	s.mu.Lock()
+	s.buf.WriteString(event.Delta)
+	content := s.buf.String()
+	s.mu.Unlock()
+	if s.isPrivateChat {
+		return s.sendDraft(ctx, content)
+	}
+	if err := s.ensureStreamMessage(ctx, content); err != nil {
+		return err
+	}
+	return s.editStreamMessage(ctx, content)
+}
+
+func (s *telegramOutboundStream) pushFinal(ctx context.Context, event channel.StreamEvent) error {
+	// In draft mode, read and reset buffer atomically to prevent duplicate
+	// permanent messages when multiple StreamEventFinal events fire
+	// (one per assistant output in multi-tool-call responses).
+	s.mu.Lock()
+	bufText := strings.TrimSpace(s.buf.String())
+	if s.isPrivateChat {
+		s.buf.Reset()
+	}
+	s.mu.Unlock()
+
+	if event.Final == nil || event.Final.Message.IsEmpty() {
+		if bufText != "" {
+			if err := s.deliverFinalText(ctx, bufText, ""); err != nil {
+				if s.adapter != nil && s.adapter.logger != nil {
+					s.adapter.logger.Warn("telegram: deliver buffered final text failed", slog.Any("error", err))
+				}
+			}
+		}
+		return nil
+	}
+
+	msg := event.Final.Message
+	finalText := bufText
+	if finalText == "" && !s.isPrivateChat {
+		finalText = strings.TrimSpace(msg.PlainText())
+	}
+
+	// Convert markdown to Telegram HTML for the final message.
+	formatted, pm := formatTelegramOutput(finalText, msg.Format)
+	if pm != "" {
+		s.mu.Lock()
+		s.parseMode = pm
+		s.mu.Unlock()
+		finalText = formatted
+	}
+
+	if err := s.deliverFinalText(ctx, finalText, s.parseMode); err != nil {
+		return err
+	}
+
+	if len(msg.Attachments) > 0 {
+		bot, err := s.getBot(ctx)
+		if err != nil {
+			return err
+		}
+		replyTo := parseReplyToMessageID(s.reply)
+		parseMode := resolveTelegramParseMode(msg.Format)
+		for i, att := range msg.Attachments {
+			to := replyTo
+			if i > 0 {
+				to = 0
+			}
+			if err := sendTelegramAttachmentWithAssets(ctx, bot, s.target, att, "", to, parseMode, s.adapter.assets); err != nil && s.adapter.logger != nil {
+				s.adapter.logger.Error("stream final attachment failed", slog.String("config_id", s.cfg.ID), slog.Any("error", err))
+			}
+		}
+	}
+	return nil
+}
+
+func (s *telegramOutboundStream) pushError(ctx context.Context, event channel.StreamEvent) error {
+	errText := strings.TrimSpace(event.Error)
+	if errText == "" {
+		return nil
+	}
+	display := "Error: " + errText
+	if s.isPrivateChat {
+		return s.sendPermanentMessage(ctx, display, "")
+	}
+	if err := s.ensureStreamMessage(ctx, display); err != nil {
+		return err
+	}
+	return s.editStreamMessage(ctx, display)
+}
+
 func (s *telegramOutboundStream) Push(ctx context.Context, event channel.StreamEvent) error {
 	if s == nil || s.adapter == nil {
 		return errors.New("telegram stream not configured")
@@ -278,196 +460,21 @@ func (s *telegramOutboundStream) Push(ctx context.Context, event channel.StreamE
 	default:
 	}
 	switch event.Type {
-	case channel.StreamEventStatus:
-		return nil
 	case channel.StreamEventToolCallStart:
-		s.mu.Lock()
-		bufText := strings.TrimSpace(s.buf.String())
-		hasMsg := s.streamMsgID != 0
-		s.mu.Unlock()
-		if s.isPrivateChat {
-			// In draft mode, send buffered text as a permanent message before tool execution.
-			if bufText != "" {
-				if err := s.sendPermanentMessage(ctx, bufText, ""); err != nil {
-					if s.adapter != nil && s.adapter.logger != nil {
-						s.adapter.logger.Warn("telegram: draft permanent message failed", slog.Any("error", err))
-					}
-				}
-			}
-		} else if hasMsg && bufText != "" {
-			_ = s.editStreamMessageFinal(ctx, bufText)
-		}
-		s.mu.Lock()
-		s.streamMsgID = 0
-		if !s.isPrivateChat {
-			s.streamChatID = 0
-		}
-		s.lastEdited = ""
-		s.lastEditedAt = time.Time{}
-		s.buf.Reset()
-		s.mu.Unlock()
-		return nil
+		return s.pushToolCallStart(ctx)
 	case channel.StreamEventToolCallEnd:
-		s.mu.Lock()
-		s.streamMsgID = 0
-		if !s.isPrivateChat {
-			s.streamChatID = 0
-		}
-		s.lastEdited = ""
-		s.lastEditedAt = time.Time{}
-		s.buf.Reset()
-		s.mu.Unlock()
+		s.resetStreamState()
 		return nil
 	case channel.StreamEventAttachment:
-		if len(event.Attachments) == 0 {
-			return nil
-		}
-		bot, replyTo, err := s.getBotAndReply(ctx)
-		if err != nil {
-			return err
-		}
-		for _, att := range event.Attachments {
-			if sendErr := sendTelegramAttachmentWithAssets(ctx, bot, s.target, att, "", replyTo, "", s.adapter.assets); sendErr != nil {
-				if s.adapter != nil && s.adapter.logger != nil {
-					s.adapter.logger.Warn("telegram: stream attachment send failed",
-						slog.String("config_id", s.cfg.ID),
-						slog.String("type", string(att.Type)),
-						slog.Any("error", sendErr),
-					)
-				}
-			}
-		}
-		return nil
-	case channel.StreamEventPhaseStart:
-		return nil
+		return s.pushAttachment(ctx, event)
 	case channel.StreamEventPhaseEnd:
-		if event.Phase == channel.StreamPhaseText {
-			// In draft mode, skip phase-end finalization; StreamEventFinal sends the
-			// permanent formatted message.
-			if s.isPrivateChat {
-				return nil
-			}
-			s.mu.Lock()
-			finalText := strings.TrimSpace(s.buf.String())
-			s.mu.Unlock()
-			if finalText != "" {
-				if err := s.ensureStreamMessage(ctx, finalText); err != nil {
-					return err
-				}
-				return s.editStreamMessageFinal(ctx, finalText)
-			}
-		}
-		return nil
-	case channel.StreamEventProcessingFailed, channel.StreamEventAgentStart, channel.StreamEventAgentEnd, channel.StreamEventProcessingStarted, channel.StreamEventProcessingCompleted:
-		return nil
+		return s.pushPhaseEnd(ctx, event)
 	case channel.StreamEventDelta:
-		if event.Delta == "" || event.Phase == channel.StreamPhaseReasoning {
-			return nil
-		}
-		s.mu.Lock()
-		s.buf.WriteString(event.Delta)
-		content := s.buf.String()
-		s.mu.Unlock()
-		if s.isPrivateChat {
-			return s.sendDraft(ctx, content)
-		}
-		if err := s.ensureStreamMessage(ctx, content); err != nil {
-			return err
-		}
-		return s.editStreamMessage(ctx, content)
+		return s.pushDelta(ctx, event)
 	case channel.StreamEventFinal:
-		// In draft mode, read and reset buffer atomically to prevent duplicate
-		// permanent messages when multiple StreamEventFinal events fire
-		// (one per assistant output in multi-tool-call responses).
-		s.mu.Lock()
-		bufText := strings.TrimSpace(s.buf.String())
-		if s.isPrivateChat {
-			s.buf.Reset()
-		}
-		s.mu.Unlock()
-		if event.Final == nil || event.Final.Message.IsEmpty() {
-			if bufText != "" {
-				if s.isPrivateChat {
-					if err := s.sendPermanentMessage(ctx, bufText, ""); err != nil {
-						if s.adapter != nil && s.adapter.logger != nil {
-							s.adapter.logger.Warn("telegram: draft final permanent message failed", slog.Any("error", err))
-						}
-					}
-				} else {
-					if err := s.ensureStreamMessage(ctx, bufText); err != nil {
-						if s.adapter != nil && s.adapter.logger != nil {
-							s.adapter.logger.Warn("telegram: ensure stream message failed", slog.Any("error", err))
-						}
-					}
-					if err := s.editStreamMessageFinal(ctx, bufText); err != nil {
-						if s.adapter != nil && s.adapter.logger != nil {
-							s.adapter.logger.Warn("telegram: edit stream message failed", slog.Any("error", err))
-						}
-					}
-				}
-			}
-			return nil
-		}
-		msg := event.Final.Message
-		finalText := bufText
-		if finalText == "" && !s.isPrivateChat {
-			finalText = strings.TrimSpace(msg.PlainText())
-		}
-		// Convert markdown to Telegram HTML for the final message.
-		formatted, pm := formatTelegramOutput(finalText, msg.Format)
-		if pm != "" {
-			s.mu.Lock()
-			s.parseMode = pm
-			s.mu.Unlock()
-			finalText = formatted
-		}
-		if s.isPrivateChat {
-			if err := s.sendPermanentMessage(ctx, finalText, s.parseMode); err != nil {
-				return err
-			}
-		} else {
-			if err := s.ensureStreamMessage(ctx, finalText); err != nil {
-				return err
-			}
-			if err := s.editStreamMessageFinal(ctx, finalText); err != nil {
-				return err
-			}
-		}
-		if len(msg.Attachments) > 0 {
-			replyTo := parseReplyToMessageID(s.reply)
-			telegramCfg, err := parseConfig(s.cfg.Credentials)
-			if err != nil {
-				return err
-			}
-			bot, err := s.adapter.getOrCreateBot(telegramCfg, s.cfg.ID)
-			if err != nil {
-				return err
-			}
-			parseMode := resolveTelegramParseMode(msg.Format)
-			for i, att := range msg.Attachments {
-				to := replyTo
-				if i > 0 {
-					to = 0
-				}
-				if err := sendTelegramAttachmentWithAssets(ctx, bot, s.target, att, "", to, parseMode, s.adapter.assets); err != nil && s.adapter.logger != nil {
-					s.adapter.logger.Error("stream final attachment failed", slog.String("config_id", s.cfg.ID), slog.Any("error", err))
-				}
-			}
-		}
-		return nil
+		return s.pushFinal(ctx, event)
 	case channel.StreamEventError:
-		errText := strings.TrimSpace(event.Error)
-		if errText == "" {
-			return nil
-		}
-		display := "Error: " + errText
-		if s.isPrivateChat {
-			return s.sendPermanentMessage(ctx, display, "")
-		}
-		if err := s.ensureStreamMessage(ctx, display); err != nil {
-			return err
-		}
-		return s.editStreamMessage(ctx, display)
+		return s.pushError(ctx, event)
 	default:
 		return nil
 	}

internal/channel/adapters/telegram/telegram.go

@@ -1,6 +1,7 @@
 package telegram
 
 import (
+	"cmp"
 	"context"
 	"encoding/base64"
 	"errors"
@@ -8,7 +9,7 @@ import (
 	"io"
 	"log/slog"
 	"net/http"
-	"sort"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -434,8 +435,8 @@ func (a *TelegramAdapter) buildTelegramMediaGroupInboundMessage(
 	if len(items) == 0 {
 		return channel.InboundMessage{}, false
 	}
-	sort.SliceStable(items, func(i, j int) bool {
-		return items[i].MessageID < items[j].MessageID
+	slices.SortStableFunc(items, func(a, b *tgbotapi.Message) int {
+		return cmp.Compare(a.MessageID, b.MessageID)
 	})
 	anchor := items[0]
 	text := ""
@@ -743,32 +744,25 @@ func sendTelegramTextReturnMessage(bot *tgbotapi.BotAPI, target string, text str
 	if sendTextForTest != nil {
 		return sendTextForTest(bot, target, text, replyTo, parseMode)
 	}
-	var sent tgbotapi.Message
-	if strings.HasPrefix(target, "@") {
-		message := tgbotapi.NewMessageToChannel(target, text)
-		message.ParseMode = parseMode
-		if replyTo > 0 {
-			message.ReplyToMessageID = replyTo
-		}
-		sent, err = bot.Send(message)
-		if err != nil {
-			return 0, 0, err
-		}
-	} else {
-		chatID, err = strconv.ParseInt(target, 10, 64)
-		if err != nil {
-			return 0, 0, errors.New("telegram target must be @username or chat_id")
-		}
-		message := tgbotapi.NewMessage(chatID, text)
-		message.ParseMode = parseMode
-		if replyTo > 0 {
-			message.ReplyToMessageID = replyTo
-		}
-		sent, err = bot.Send(message)
-		if err != nil {
-			return 0, 0, err
-		}
+	parsedChatID, channelUsername, parseErr := parseTelegramTarget(target)
+	if parseErr != nil {
+		return 0, 0, parseErr
 	}
+	var message tgbotapi.MessageConfig
+	if channelUsername != "" {
+		message = tgbotapi.NewMessageToChannel(channelUsername, text)
+	} else {
+		message = tgbotapi.NewMessage(parsedChatID, text)
+	}
+	message.ParseMode = parseMode
+	if replyTo > 0 {
+		message.ReplyToMessageID = replyTo
+	}
+	sent, err := bot.Send(message)
+	if err != nil {
+		return 0, 0, err
+	}
+	chatID = parsedChatID
 	if sent.Chat != nil {
 		chatID = sent.Chat.ID
 	}
@@ -875,17 +869,17 @@ func sendTelegramAttachmentImpl(ctx context.Context, bot *tgbotapi.BotAPI, targe
 	if err != nil {
 		return err
 	}
-	isChannel := strings.HasPrefix(target, "@")
+	chatID, channelUsername, targetErr := parseTelegramTarget(target)
+	if targetErr != nil {
+		return targetErr
+	}
+	isChannel := channelUsername != ""
 	switch att.Type {
 	case channel.AttachmentImage:
 		var photo tgbotapi.PhotoConfig
 		if isChannel {
-			photo = tgbotapi.NewPhotoToChannel(target, file)
+			photo = tgbotapi.NewPhotoToChannel(channelUsername, file)
 		} else {
-			chatID, err := strconv.ParseInt(target, 10, 64)
-			if err != nil {
-				return errors.New("telegram target must be @username or chat_id")
-			}
 			photo = tgbotapi.NewPhoto(chatID, file)
 		}
 		photo.Caption = caption
@@ -900,15 +894,11 @@ func sendTelegramAttachmentImpl(ctx context.Context, bot *tgbotapi.BotAPI, targe
 		if isChannel {
 			document = tgbotapi.DocumentConfig{
 				BaseFile: tgbotapi.BaseFile{
-					BaseChat: tgbotapi.BaseChat{ChannelUsername: target},
+					BaseChat: tgbotapi.BaseChat{ChannelUsername: channelUsername},
 					File:     file,
 				},
 			}
 		} else {
-			chatID, err := strconv.ParseInt(target, 10, 64)
-			if err != nil {
-				return errors.New("telegram target must be @username or chat_id")
-			}
 			document = tgbotapi.NewDocument(chatID, file)
 		}
 		document.Caption = caption
@@ -1017,8 +1007,8 @@ func resolveTelegramFile(ctx context.Context, urlRef, keyRef, base64Ref, sourceP
 
 func decodeDataURLBytes(dataURL string) ([]byte, error) {
 	value := dataURL
-	if idx := strings.Index(value, ","); idx >= 0 {
-		value = value[idx+1:]
+	if _, after, ok := strings.Cut(value, ","); ok {
+		value = after
 	}
 	return io.ReadAll(io.LimitReader(
 		base64StdDecoder(strings.NewReader(value)),
@@ -1155,56 +1145,58 @@ func buildTelegramForwardContext(msg *tgbotapi.Message) string {
 	return ""
 }
 
-func buildTelegramAudio(target string, file tgbotapi.RequestFileData) (tgbotapi.AudioConfig, error) {
+// parseTelegramTarget resolves a target string into a numeric chat ID and an
+// optional channel username. Exactly one of chatID or channelUsername will be
+// set; callers can use this to construct any message config type.
+func parseTelegramTarget(target string) (chatID int64, channelUsername string, err error) {
 	if strings.HasPrefix(target, "@") {
-		audio := tgbotapi.NewAudio(0, file)
-		audio.ChannelUsername = target
-		return audio, nil
+		return 0, target, nil
 	}
-	chatID, err := strconv.ParseInt(target, 10, 64)
+	chatID, err = strconv.ParseInt(target, 10, 64)
 	if err != nil {
-		return tgbotapi.AudioConfig{}, errors.New("telegram target must be @username or chat_id")
+		return 0, "", errors.New("telegram target must be @username or chat_id")
 	}
-	return tgbotapi.NewAudio(chatID, file), nil
+	return chatID, "", nil
+}
+
+func buildTelegramAudio(target string, file tgbotapi.RequestFileData) (tgbotapi.AudioConfig, error) {
+	chatID, channelUsername, err := parseTelegramTarget(target)
+	if err != nil {
+		return tgbotapi.AudioConfig{}, err
+	}
+	audio := tgbotapi.NewAudio(chatID, file)
+	audio.ChannelUsername = channelUsername
+	return audio, nil
 }
 
 func buildTelegramVoice(target string, file tgbotapi.RequestFileData) (tgbotapi.VoiceConfig, error) {
-	if strings.HasPrefix(target, "@") {
-		voice := tgbotapi.NewVoice(0, file)
-		voice.ChannelUsername = target
-		return voice, nil
-	}
-	chatID, err := strconv.ParseInt(target, 10, 64)
+	chatID, channelUsername, err := parseTelegramTarget(target)
 	if err != nil {
-		return tgbotapi.VoiceConfig{}, errors.New("telegram target must be @username or chat_id")
+		return tgbotapi.VoiceConfig{}, err
 	}
-	return tgbotapi.NewVoice(chatID, file), nil
+	voice := tgbotapi.NewVoice(chatID, file)
+	voice.ChannelUsername = channelUsername
+	return voice, nil
 }
 
 func buildTelegramVideo(target string, file tgbotapi.RequestFileData) (tgbotapi.VideoConfig, error) {
-	if strings.HasPrefix(target, "@") {
-		video := tgbotapi.NewVideo(0, file)
-		video.ChannelUsername = target
-		return video, nil
-	}
-	chatID, err := strconv.ParseInt(target, 10, 64)
+	chatID, channelUsername, err := parseTelegramTarget(target)
 	if err != nil {
-		return tgbotapi.VideoConfig{}, errors.New("telegram target must be @username or chat_id")
+		return tgbotapi.VideoConfig{}, err
 	}
-	return tgbotapi.NewVideo(chatID, file), nil
+	video := tgbotapi.NewVideo(chatID, file)
+	video.ChannelUsername = channelUsername
+	return video, nil
 }
 
 func buildTelegramAnimation(target string, file tgbotapi.RequestFileData) (tgbotapi.AnimationConfig, error) {
-	if strings.HasPrefix(target, "@") {
-		animation := tgbotapi.NewAnimation(0, file)
-		animation.ChannelUsername = target
-		return animation, nil
-	}
-	chatID, err := strconv.ParseInt(target, 10, 64)
+	chatID, channelUsername, err := parseTelegramTarget(target)
 	if err != nil {
-		return tgbotapi.AnimationConfig{}, errors.New("telegram target must be @username or chat_id")
+		return tgbotapi.AnimationConfig{}, err
 	}
-	return tgbotapi.NewAnimation(chatID, file), nil
+	animation := tgbotapi.NewAnimation(chatID, file)
+	animation.ChannelUsername = channelUsername
+	return animation, nil
 }
 
 func resolveTelegramParseMode(format channel.MessageFormat) string {
@@ -1424,8 +1416,8 @@ func (a *TelegramAdapter) ResolveAttachment(ctx context.Context, cfg channel.Cha
 	mime := strings.TrimSpace(attachment.Mime)
 	if mime == "" {
 		mime = strings.TrimSpace(resp.Header.Get("Content-Type"))
-		if idx := strings.Index(mime, ";"); idx >= 0 {
-			mime = strings.TrimSpace(mime[:idx])
+		if base, _, ok := strings.Cut(mime, ";"); ok {
+			mime = strings.TrimSpace(base)
 		}
 	}
 	size := attachment.Size