diff --git a/internal/channels/feishu/bot_policy.go b/internal/channels/feishu/bot_policy.go
index a4862195..f91724da 100644
--- a/internal/channels/feishu/bot_policy.go
+++ b/internal/channels/feishu/bot_policy.go
@@ -151,7 +151,7 @@ func (c *Channel) sendPairingReply(senderID, chatID string) {
 
 	// Debounce
 	if lastSent, ok := c.pairingDebounce.Load(senderID); ok {
-		if time.Since(lastSent.(time.Time)) < pairingDebounceTime {
+		if t, ok := lastSent.(time.Time); ok && time.Since(t) < pairingDebounceTime {
 			return
 		}
 	}
diff --git a/internal/channels/feishu/feishu.go b/internal/channels/feishu/feishu.go
index 94c70ac4..294ce98a 100644
--- a/internal/channels/feishu/feishu.go
+++ b/internal/channels/feishu/feishu.go
@@ -440,10 +440,9 @@ func shouldUseCard(text string) bool {
 func (c *Channel) isDuplicate(messageID string) bool {
 	_, loaded := c.dedup.LoadOrStore(messageID, struct{}{})
 	if !loaded {
-		go func() {
-			time.Sleep(5 * time.Minute)
+		time.AfterFunc(5*time.Minute, func() {
 			c.dedup.Delete(messageID)
-		}()
+		})
 	}
 	return loaded
 }
diff --git a/internal/channels/feishu/larkclient_messaging.go b/internal/channels/feishu/larkclient_messaging.go
index f828c733..ce568958 100644
--- a/internal/channels/feishu/larkclient_messaging.go
+++ b/internal/channels/feishu/larkclient_messaging.go
@@ -30,7 +30,9 @@ func (c *LarkClient) SendMessage(ctx context.Context, receiveIDType, receiveID,
 		return nil, fmt.Errorf("send message: code=%d msg=%s", resp.Code, resp.Msg)
 	}
 	var data SendMessageResp
-	json.Unmarshal(resp.Data, &data)
+	if err := json.Unmarshal(resp.Data, &data); err != nil {
+		return nil, fmt.Errorf("unmarshal response: %w", err)
+	}
 	return &data, nil
 }
 
@@ -55,7 +57,9 @@ func (c *LarkClient) UploadImage(ctx context.Context, data io.Reader) (string, e
 	var result struct {
 		ImageKey string `json:"image_key"`
 	}
-	json.Unmarshal(resp.Data, &result)
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return "", fmt.Errorf("unmarshal response: %w", err)
+	}
 	return result.ImageKey, nil
 }
 
@@ -79,7 +83,9 @@ func (c *LarkClient) UploadFile(ctx context.Context, data io.Reader, fileName, f
 	var result struct {
 		FileKey string `json:"file_key"`
 	}
-	json.Unmarshal(resp.Data, &result)
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return "", fmt.Errorf("unmarshal response: %w", err)
+	}
 	return result.FileKey, nil
 }
 
@@ -106,7 +112,9 @@ func (c *LarkClient) CreateCard(ctx context.Context, cardType, data string) (str
 	var result struct {
 		CardID string `json:"card_id"`
 	}
-	json.Unmarshal(resp.Data, &result)
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return "", fmt.Errorf("unmarshal response: %w", err)
+	}
 	return result.CardID, nil
 }
 
@@ -165,7 +173,9 @@ func (c *LarkClient) AddMessageReaction(ctx context.Context, messageID, emojiTyp
 	var result struct {
 		ReactionID string `json:"reaction_id"`
 	}
-	json.Unmarshal(resp.Data, &result)
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return "", fmt.Errorf("unmarshal response: %w", err)
+	}
 	return result.ReactionID, nil
 }
 
@@ -200,7 +210,9 @@ func (c *LarkClient) GetBotInfo(ctx context.Context) (string, error) {
 			OpenID string `json:"open_id"`
 		} `json:"bot"`
 	}
-	json.Unmarshal(resp.Data, &result)
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return "", fmt.Errorf("unmarshal response: %w", err)
+	}
 	return result.Bot.OpenID, nil
 }
 
@@ -220,6 +232,8 @@ func (c *LarkClient) GetUser(ctx context.Context, userID, userIDType string) (st
 			Name string `json:"name"`
 		} `json:"user"`
 	}
-	json.Unmarshal(resp.Data, &result)
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return "", fmt.Errorf("unmarshal response: %w", err)
+	}
 	return result.User.Name, nil
 }
diff --git a/internal/channels/feishu/larkevents.go b/internal/channels/feishu/larkevents.go
index c786d744..ccb3e9d8 100644
--- a/internal/channels/feishu/larkevents.go
+++ b/internal/channels/feishu/larkevents.go
@@ -105,6 +105,7 @@ func NewWebhookHandler(verificationToken, encryptKey string, onMessage func(even
 		}
 
 		// Handle encrypted events
+		eventBody := body
 		if envelope.Encrypt != "" && encryptKey != "" {
 			decrypted, err := decryptEvent(envelope.Encrypt, encryptKey)
 			if err != nil {
@@ -112,6 +113,7 @@ func NewWebhookHandler(verificationToken, encryptKey string, onMessage func(even
 				http.Error(w, "decrypt failed", http.StatusBadRequest)
 				return
 			}
+			eventBody = decrypted
 			// Re-parse decrypted content
 			if err := json.Unmarshal(decrypted, &envelope); err != nil {
 				http.Error(w, "invalid decrypted json", http.StatusBadRequest)
@@ -128,14 +130,6 @@ func NewWebhookHandler(verificationToken, encryptKey string, onMessage func(even
 
 		// Parse as message event
 		var event MessageEvent
-		// Re-unmarshal the original (or decrypted) body as a full event
-		eventBody := body
-		if envelope.Encrypt != "" && encryptKey != "" {
-			decrypted, _ := decryptEvent(envelope.Encrypt, encryptKey)
-			if decrypted != nil {
-				eventBody = decrypted
-			}
-		}
 
 		if err := json.Unmarshal(eventBody, &event); err != nil {
 			slog.Debug("feishu webhook parse event failed", "error", err)
diff --git a/internal/channels/feishu/larkws.go b/internal/channels/feishu/larkws.go
index 02ec451e..603ab603 100644
--- a/internal/channels/feishu/larkws.go
+++ b/internal/channels/feishu/larkws.go
@@ -189,7 +189,8 @@ func (c *WSClient) getWSEndpoint(ctx context.Context) (string, error) {
 	}
 	req.Header.Set("Content-Type", "application/json")
 
-	resp, err := http.DefaultClient.Do(req)
+	client := &http.Client{Timeout: 30 * time.Second}
+	resp, err := client.Do(req)
 	if err != nil {
 		return "", fmt.Errorf("ws endpoint request: %w", err)
 	}
diff --git a/internal/channels/feishu/media.go b/internal/channels/feishu/media.go
index 1d388ffc..8615a8dc 100644
--- a/internal/channels/feishu/media.go
+++ b/internal/channels/feishu/media.go
@@ -2,6 +2,7 @@ package feishu
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"io"
 	"os"
@@ -35,8 +36,11 @@ func (c *Channel) uploadFile(ctx context.Context, data io.Reader, fileName, file
 
 // sendImage sends an image message using an image_key.
 func (c *Channel) sendImage(ctx context.Context, chatID, receiveIDType, imageKey string) error {
-	content := fmt.Sprintf(`{"image_key":"%s"}`, imageKey)
-	_, err := c.client.SendMessage(ctx, receiveIDType, chatID, "image", content)
+	contentBytes, err := json.Marshal(map[string]string{"image_key": imageKey})
+	if err != nil {
+		return fmt.Errorf("marshal image content: %w", err)
+	}
+	_, err = c.client.SendMessage(ctx, receiveIDType, chatID, "image", string(contentBytes))
 	if err != nil {
 		return fmt.Errorf("feishu send image: %w", err)
 	}
@@ -49,8 +53,11 @@ func (c *Channel) sendFile(ctx context.Context, chatID, receiveIDType, fileKey,
 	if msgType == "" {
 		msgType = "file"
 	}
-	content := fmt.Sprintf(`{"file_key":"%s"}`, fileKey)
-	_, err := c.client.SendMessage(ctx, receiveIDType, chatID, msgType, content)
+	contentBytes, err := json.Marshal(map[string]string{"file_key": fileKey})
+	if err != nil {
+		return fmt.Errorf("marshal file content: %w", err)
+	}
+	_, err = c.client.SendMessage(ctx, receiveIDType, chatID, msgType, string(contentBytes))
 	if err != nil {
 		return fmt.Errorf("feishu send file: %w", err)
 	}
diff --git a/internal/channels/telegram/reactions.go b/internal/channels/telegram/reactions.go
index 4f59b9d6..d6b1e2fa 100644
--- a/internal/channels/telegram/reactions.go
+++ b/internal/channels/telegram/reactions.go
@@ -137,7 +137,7 @@ func (rc *StatusReactionController) SetStatus(ctx context.Context, status string
 
 		emoji := resolveReactionEmoji(rc.lastStatus, nil)
 		if emoji != "" {
-			rc.applyReaction(ctx, emoji)
+			rc.applyReaction(context.Background(), emoji)
 		}
 	})
 }
@@ -180,7 +180,7 @@ func (rc *StatusReactionController) applyReaction(ctx context.Context, emoji str
 }
 
 // resetStallTimer resets the stall detection timer (must hold mu lock).
-func (rc *StatusReactionController) resetStallTimer(ctx context.Context) {
+func (rc *StatusReactionController) resetStallTimer(_ context.Context) {
 	rc.cancelStall()
 
 	rc.stallTimer = time.AfterFunc(stallSoftMs, func() {
@@ -193,7 +193,7 @@ func (rc *StatusReactionController) resetStallTimer(ctx context.Context) {
 
 		emoji := resolveReactionEmoji("stallSoft", nil)
 		if emoji != "" {
-			rc.applyReaction(ctx, emoji)
+			rc.applyReaction(context.Background(), emoji)
 		}
 
 		// Schedule hard stall
@@ -207,7 +207,7 @@ func (rc *StatusReactionController) resetStallTimer(ctx context.Context) {
 
 			emoji := resolveReactionEmoji("stallHard", nil)
 			if emoji != "" {
-				rc.applyReaction(ctx, emoji)
+				rc.applyReaction(context.Background(), emoji)
 			}
 		})
 	})
@@ -258,7 +258,10 @@ func (c *Channel) OnReactionEvent(ctx context.Context, chatID string, messageID
 	// Key by messageID so concurrent runs in the same chat don't clash.
 	key := fmt.Sprintf("%s:%s", chatID, messageID)
 	val, _ := c.reactions.LoadOrStore(key, newStatusReactionController(c.bot, id, msgID))
-	rc := val.(*StatusReactionController)
+	rc, ok := val.(*StatusReactionController)
+	if !ok {
+		return nil
+	}
 
 	rc.SetStatus(ctx, status)
 
@@ -285,8 +288,9 @@ func (c *Channel) ClearReaction(ctx context.Context, chatID string, messageID st
 	// Stop and remove controller if exists
 	key := fmt.Sprintf("%s:%s", chatID, messageID)
 	if val, ok := c.reactions.LoadAndDelete(key); ok {
-		rc := val.(*StatusReactionController)
-		rc.Stop()
+		if rc, ok := val.(*StatusReactionController); ok {
+			rc.Stop()
+		}
 	}
 
 	// Clear reaction on the message
diff --git a/internal/channels/zalo/personal/channel.go b/internal/channels/zalo/personal/channel.go
index 156e5d7d..98d39d9b 100644
--- a/internal/channels/zalo/personal/channel.go
+++ b/internal/channels/zalo/personal/channel.go
@@ -134,7 +134,9 @@ func (c *Channel) Stop(_ context.Context) error {
 	slog.Info("stopping zalo_personal channel")
 	c.stopOnce.Do(func() { close(c.stopCh) })
 	c.typingCtrls.Range(func(key, val any) bool {
-		val.(*typing.Controller).Stop()
+		if ctrl, ok := val.(*typing.Controller); ok {
+			ctrl.Stop()
+		}
 		c.typingCtrls.Delete(key)
 		return true
 	})
diff --git a/internal/channels/zalo/personal/handlers.go b/internal/channels/zalo/personal/handlers.go
index c40f768d..910d3f39 100644
--- a/internal/channels/zalo/personal/handlers.go
+++ b/internal/channels/zalo/personal/handlers.go
@@ -147,7 +147,9 @@ func (c *Channel) startTyping(threadID string, threadType protocol.ThreadType) {
 		},
 	})
 	if prev, ok := c.typingCtrls.Load(threadID); ok {
-		prev.(*typing.Controller).Stop()
+		if ctrl, ok := prev.(*typing.Controller); ok {
+			ctrl.Stop()
+		}
 	}
 	c.typingCtrls.Store(threadID, ctrl)
 	ctrl.Start()
diff --git a/internal/channels/zalo/zalo.go b/internal/channels/zalo/zalo.go
index 2c5ce04a..88279a4b 100644
--- a/internal/channels/zalo/zalo.go
+++ b/internal/channels/zalo/zalo.go
@@ -187,6 +187,10 @@ func (c *Channel) processUpdate(update zaloUpdate) {
 
 func (c *Channel) handleTextMessage(msg *zaloMessage) {
 	senderID := msg.From.ID
+	if senderID == "" {
+		slog.Warn("zalo: dropping text message with empty sender ID", "message_id", msg.MessageID)
+		return
+	}
 	chatID := msg.Chat.ID
 	if chatID == "" {
 		chatID = senderID
@@ -218,6 +222,10 @@ func (c *Channel) handleTextMessage(msg *zaloMessage) {
 
 func (c *Channel) handleImageMessage(msg *zaloMessage) {
 	senderID := msg.From.ID
+	if senderID == "" {
+		slog.Warn("zalo: dropping image message with empty sender ID", "message_id", msg.MessageID)
+		return
+	}
 	chatID := msg.Chat.ID
 	if chatID == "" {
 		chatID = senderID