From 82aae32fe71f26da4a9354e14767a1015a63ed4e Mon Sep 17 00:00:00 2001
From: dj-oyu <68707227+dj-oyu@users.noreply.github.com>
Date: Fri, 20 Feb 2026 00:14:09 +0900
Subject: [PATCH] telegram: strip think blocks and split long outbound messages

---
 pkg/channels/telegram.go      | 55 +++++++++++++++++++++++++++--------
 pkg/channels/telegram_test.go | 22 ++++++++++++++
 2 files changed, 65 insertions(+), 12 deletions(-)
 create mode 100644 pkg/channels/telegram_test.go

diff --git a/pkg/channels/telegram.go b/pkg/channels/telegram.go
index 24b82b557..b318ceb56 100644
--- a/pkg/channels/telegram.go
+++ b/pkg/channels/telegram.go
@@ -45,6 +45,10 @@ func (c *thinkingCancel) Cancel() {
 	}
 }
 
+const telegramMaxMessageChars = 3900
+
+var thinkBlockPattern = regexp.MustCompile(`(?is)<think>.*?</think>`)
+
 func NewTelegramChannel(cfg *config.Config, bus *bus.MessageBus) (*TelegramChannel, error) {
 	var opts []telego.BotOption
 	telegramCfg := cfg.Channels.Telegram
@@ -157,35 +161,62 @@ func (c *TelegramChannel) Send(ctx context.Context, msg bus.OutboundMessage) err
 		c.stopThinking.Delete(msg.ChatID)
 	}
 
-	htmlContent := markdownToTelegramHTML(msg.Content)
+	cleanContent := sanitizeTelegramOutgoingContent(msg.Content)
+	chunks := utils.SplitMessage(cleanContent, telegramMaxMessageChars)
+	if len(chunks) == 0 {
+		chunks = []string{cleanContent}
+	}
 
 	// Try to edit placeholder
+	firstChunkSent := false
 	if pID, ok := c.placeholders.Load(msg.ChatID); ok {
 		c.placeholders.Delete(msg.ChatID)
-		editMsg := tu.EditMessageText(tu.ID(chatID), pID.(int), htmlContent)
+		editMsg := tu.EditMessageText(tu.ID(chatID), pID.(int), markdownToTelegramHTML(chunks[0]))
 		editMsg.ParseMode = telego.ModeHTML
 
 		if _, err = c.bot.EditMessageText(ctx, editMsg); err == nil {
-			return nil
+			firstChunkSent = true
 		}
 		// Fallback to new message if edit fails
 	}
 
-	tgMsg := tu.Message(tu.ID(chatID), htmlContent)
-	tgMsg.ParseMode = telego.ModeHTML
+	sendChunk := func(text string) error {
+		tgMsg := tu.Message(tu.ID(chatID), markdownToTelegramHTML(text))
+		tgMsg.ParseMode = telego.ModeHTML
+		if _, sendErr := c.bot.SendMessage(ctx, tgMsg); sendErr != nil {
+			logger.ErrorCF("telegram", "HTML parse failed, falling back to plain text", map[string]interface{}{
+				"error": sendErr.Error(),
+			})
+			fallbackMsg := tu.Message(tu.ID(chatID), text)
+			fallbackMsg.ParseMode = ""
+			_, sendErr = c.bot.SendMessage(ctx, fallbackMsg)
+			return sendErr
+		}
+		return nil
+	}
 
-	if _, err = c.bot.SendMessage(ctx, tgMsg); err != nil {
-		logger.ErrorCF("telegram", "HTML parse failed, falling back to plain text", map[string]interface{}{
-			"error": err.Error(),
-		})
-		tgMsg.ParseMode = ""
-		_, err = c.bot.SendMessage(ctx, tgMsg)
-		return err
+	startIdx := 0
+	if firstChunkSent {
+		startIdx = 1
+	}
+	for i := startIdx; i < len(chunks); i++ {
+		if err = sendChunk(chunks[i]); err != nil {
+			return err
+		}
 	}
 
 	return nil
 }
 
+func sanitizeTelegramOutgoingContent(content string) string {
+	cleaned := thinkBlockPattern.ReplaceAllString(content, "")
+	cleaned = strings.TrimSpace(cleaned)
+	if cleaned == "" {
+		return "(empty response)"
+	}
+	return cleaned
+}
+
 func (c *TelegramChannel) handleMessage(ctx context.Context, message *telego.Message) error {
 	if message == nil {
 		return fmt.Errorf("message is nil")
diff --git a/pkg/channels/telegram_test.go b/pkg/channels/telegram_test.go
new file mode 100644
index 000000000..7c6f9fd16
--- /dev/null
+++ b/pkg/channels/telegram_test.go
@@ -0,0 +1,22 @@
+package channels
+
+import "testing"
+
+func TestSanitizeTelegramOutgoingContent_RemovesThinkBlock(t *testing.T) {
+	in := "<think>\nsecret reasoning\n</think>\n\nユーザー向け本文"
+	got := sanitizeTelegramOutgoingContent(in)
+	want := "ユーザー向け本文"
+	if got != want {
+		t.Fatalf("sanitizeTelegramOutgoingContent() = %q, want %q", got, want)
+	}
+}
+
+func TestSanitizeTelegramOutgoingContent_EmptyAfterThink(t *testing.T) {
+	in := "<think>only reasoning</think>"
+	got := sanitizeTelegramOutgoingContent(in)
+	want := "(empty response)"
+	if got != want {
+		t.Fatalf("sanitizeTelegramOutgoingContent() = %q, want %q", got, want)
+	}
+}
+