fix(feishu): address PR #1000 review comments from @xiaket

- Consolidate extractImageKey/extractFileKey/extractFileName into shared
  extractJSONStringField helper to reduce code duplication
- Move mentionPlaceholderRegex to package-level position after imports
- Rename feishuCfg field to config for clarity within FeishuChannel
- Replace @_user_1 heuristic with GET /open-apis/bot/v3/info API call
  at startup for reliable bot @mention detection
- Fix double close on file handle in downloadResource by removing defer
  and using explicit close in both success and error paths
- Add unit tests for common.go and feishu_64.go helpers (53 test cases)

pkg/channels/feishu/common.go

@@ -8,6 +8,9 @@ import (
 	larkim "github.com/larksuite/oapi-sdk-go/v3/service/im/v1"
 )
 
+// mentionPlaceholderRegex matches @_user_N placeholders inserted by Feishu for mentions.
+var mentionPlaceholderRegex = regexp.MustCompile(`@_user_\d+`)
+
 // stringValue safely dereferences a *string pointer.
 func stringValue(v *string) string {
 	if v == nil {
@@ -37,43 +40,34 @@ func buildMarkdownCard(content string) (string, error) {
 	return string(data), nil
 }
 
-// extractImageKey extracts the image_key from a Feishu image message content JSON.
-// Format: {"image_key": "img_xxx"}
-func extractImageKey(content string) string {
-	var payload struct {
-		ImageKey string `json:"image_key"`
-	}
-	if err := json.Unmarshal([]byte(content), &payload); err != nil {
+// extractJSONStringField unmarshals content as JSON and returns the value of the given string field.
+// Returns "" if the content is invalid JSON or the field is missing/empty.
+func extractJSONStringField(content, field string) string {
+	var m map[string]json.RawMessage
+	if err := json.Unmarshal([]byte(content), &m); err != nil {
 		return ""
 	}
-	return payload.ImageKey
+	raw, ok := m[field]
+	if !ok {
+		return ""
+	}
+	var s string
+	if err := json.Unmarshal(raw, &s); err != nil {
+		return ""
+	}
+	return s
 }
 
+// extractImageKey extracts the image_key from a Feishu image message content JSON.
+// Format: {"image_key": "img_xxx"}
+func extractImageKey(content string) string { return extractJSONStringField(content, "image_key") }
+
 // extractFileKey extracts the file_key from a Feishu file/audio message content JSON.
 // Format: {"file_key": "file_xxx", "file_name": "...", ...}
-func extractFileKey(content string) string {
-	var payload struct {
-		FileKey string `json:"file_key"`
-	}
-	if err := json.Unmarshal([]byte(content), &payload); err != nil {
-		return ""
-	}
-	return payload.FileKey
-}
+func extractFileKey(content string) string { return extractJSONStringField(content, "file_key") }
 
 // extractFileName extracts the file_name from a Feishu file message content JSON.
-func extractFileName(content string) string {
-	var payload struct {
-		FileName string `json:"file_name"`
-	}
-	if err := json.Unmarshal([]byte(content), &payload); err != nil {
-		return ""
-	}
-	return payload.FileName
-}
-
-// mentionPlaceholderRegex matches @_user_N placeholders inserted by Feishu for mentions.
-var mentionPlaceholderRegex = regexp.MustCompile(`@_user_\d+`)
+func extractFileName(content string) string { return extractJSONStringField(content, "file_name") }
 
 // stripMentionPlaceholders removes @_user_N placeholders from the text content.
 // These are inserted by Feishu when users @mention someone in a message.

pkg/channels/feishu/common_test.go

@@ -0,0 +1,292 @@
+package feishu
+
+import (
+	"encoding/json"
+	"testing"
+
+	larkim "github.com/larksuite/oapi-sdk-go/v3/service/im/v1"
+)
+
+func TestExtractJSONStringField(t *testing.T) {
+	tests := []struct {
+		name    string
+		content string
+		field   string
+		want    string
+	}{
+		{
+			name:    "valid field",
+			content: `{"image_key": "img_v2_xxx"}`,
+			field:   "image_key",
+			want:    "img_v2_xxx",
+		},
+		{
+			name:    "missing field",
+			content: `{"image_key": "img_v2_xxx"}`,
+			field:   "file_key",
+			want:    "",
+		},
+		{
+			name:    "invalid JSON",
+			content: `not json at all`,
+			field:   "image_key",
+			want:    "",
+		},
+		{
+			name:    "empty content",
+			content: "",
+			field:   "image_key",
+			want:    "",
+		},
+		{
+			name:    "non-string field value",
+			content: `{"count": 42}`,
+			field:   "count",
+			want:    "",
+		},
+		{
+			name:    "empty string value",
+			content: `{"image_key": ""}`,
+			field:   "image_key",
+			want:    "",
+		},
+		{
+			name:    "multiple fields",
+			content: `{"file_key": "file_xxx", "file_name": "test.pdf"}`,
+			field:   "file_name",
+			want:    "test.pdf",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractJSONStringField(tt.content, tt.field)
+			if got != tt.want {
+				t.Errorf("extractJSONStringField(%q, %q) = %q, want %q", tt.content, tt.field, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestExtractImageKey(t *testing.T) {
+	tests := []struct {
+		name    string
+		content string
+		want    string
+	}{
+		{
+			name:    "normal",
+			content: `{"image_key": "img_v2_abc123"}`,
+			want:    "img_v2_abc123",
+		},
+		{
+			name:    "missing key",
+			content: `{"file_key": "file_xxx"}`,
+			want:    "",
+		},
+		{
+			name:    "malformed JSON",
+			content: `{broken`,
+			want:    "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractImageKey(tt.content)
+			if got != tt.want {
+				t.Errorf("extractImageKey(%q) = %q, want %q", tt.content, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestExtractFileKey(t *testing.T) {
+	tests := []struct {
+		name    string
+		content string
+		want    string
+	}{
+		{
+			name:    "normal",
+			content: `{"file_key": "file_v2_abc123", "file_name": "test.doc"}`,
+			want:    "file_v2_abc123",
+		},
+		{
+			name:    "missing key",
+			content: `{"image_key": "img_xxx"}`,
+			want:    "",
+		},
+		{
+			name:    "malformed JSON",
+			content: `not json`,
+			want:    "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractFileKey(tt.content)
+			if got != tt.want {
+				t.Errorf("extractFileKey(%q) = %q, want %q", tt.content, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestExtractFileName(t *testing.T) {
+	tests := []struct {
+		name    string
+		content string
+		want    string
+	}{
+		{
+			name:    "normal",
+			content: `{"file_key": "file_xxx", "file_name": "report.pdf"}`,
+			want:    "report.pdf",
+		},
+		{
+			name:    "missing name",
+			content: `{"file_key": "file_xxx"}`,
+			want:    "",
+		},
+		{
+			name:    "malformed JSON",
+			content: `{bad`,
+			want:    "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractFileName(tt.content)
+			if got != tt.want {
+				t.Errorf("extractFileName(%q) = %q, want %q", tt.content, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestBuildMarkdownCard(t *testing.T) {
+	tests := []struct {
+		name    string
+		content string
+	}{
+		{
+			name:    "normal content",
+			content: "Hello **world**",
+		},
+		{
+			name:    "empty content",
+			content: "",
+		},
+		{
+			name:    "special characters",
+			content: `Code: "foo" & <bar> 'baz'`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := buildMarkdownCard(tt.content)
+			if err != nil {
+				t.Fatalf("buildMarkdownCard(%q) unexpected error: %v", tt.content, err)
+			}
+
+			// Verify valid JSON
+			var parsed map[string]any
+			if err := json.Unmarshal([]byte(result), &parsed); err != nil {
+				t.Fatalf("buildMarkdownCard(%q) produced invalid JSON: %v", tt.content, err)
+			}
+
+			// Verify schema
+			if parsed["schema"] != "2.0" {
+				t.Errorf("schema = %v, want %q", parsed["schema"], "2.0")
+			}
+
+			// Verify body.elements[0].content == input
+			body, ok := parsed["body"].(map[string]any)
+			if !ok {
+				t.Fatal("missing body in card JSON")
+			}
+			elements, ok := body["elements"].([]any)
+			if !ok || len(elements) == 0 {
+				t.Fatal("missing or empty elements in card JSON")
+			}
+			elem, ok := elements[0].(map[string]any)
+			if !ok {
+				t.Fatal("first element is not an object")
+			}
+			if elem["tag"] != "markdown" {
+				t.Errorf("tag = %v, want %q", elem["tag"], "markdown")
+			}
+			if elem["content"] != tt.content {
+				t.Errorf("content = %v, want %q", elem["content"], tt.content)
+			}
+		})
+	}
+}
+
+func TestStripMentionPlaceholders(t *testing.T) {
+	strPtr := func(s string) *string { return &s }
+
+	tests := []struct {
+		name     string
+		content  string
+		mentions []*larkim.MentionEvent
+		want     string
+	}{
+		{
+			name:     "no mentions",
+			content:  "Hello world",
+			mentions: nil,
+			want:     "Hello world",
+		},
+		{
+			name:    "single mention",
+			content: "@_user_1 hello",
+			mentions: []*larkim.MentionEvent{
+				{Key: strPtr("@_user_1")},
+			},
+			want: "hello",
+		},
+		{
+			name:    "multiple mentions",
+			content: "@_user_1 @_user_2 hey",
+			mentions: []*larkim.MentionEvent{
+				{Key: strPtr("@_user_1")},
+				{Key: strPtr("@_user_2")},
+			},
+			want: "hey",
+		},
+		{
+			name:     "empty content",
+			content:  "",
+			mentions: []*larkim.MentionEvent{{Key: strPtr("@_user_1")}},
+			want:     "",
+		},
+		{
+			name:     "empty mentions slice",
+			content:  "@_user_1 test",
+			mentions: []*larkim.MentionEvent{},
+			want:     "@_user_1 test",
+		},
+		{
+			name:    "mention with nil key",
+			content: "@_user_1 test",
+			mentions: []*larkim.MentionEvent{
+				{Key: nil},
+			},
+			want: "test",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := stripMentionPlaceholders(tt.content, tt.mentions)
+			if got != tt.want {
+				t.Errorf("stripMentionPlaceholders(%q, ...) = %q, want %q", tt.content, got, tt.want)
+			}
+		})
+	}
+}

pkg/channels/feishu/feishu_64.go

@@ -7,12 +7,14 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"net/http"
 	"os"
 	"path/filepath"
 	"sync"
 	"sync/atomic"
 
 	lark "github.com/larksuite/oapi-sdk-go/v3"
+	larkcore "github.com/larksuite/oapi-sdk-go/v3/core"
 	larkdispatcher "github.com/larksuite/oapi-sdk-go/v3/event/dispatcher"
 	larkim "github.com/larksuite/oapi-sdk-go/v3/service/im/v1"
 	larkws "github.com/larksuite/oapi-sdk-go/v3/ws"
@@ -28,9 +30,9 @@ import (
 
 type FeishuChannel struct {
 	*channels.BaseChannel
-	feishuCfg config.FeishuConfig
-	client    *lark.Client
-	wsClient  *larkws.Client
+	config   config.FeishuConfig
+	client   *lark.Client
+	wsClient *larkws.Client
 
 	botOpenID atomic.Value // stores string; populated lazily for @mention detection
 
@@ -46,7 +48,7 @@ func NewFeishuChannel(cfg config.FeishuConfig, bus *bus.MessageBus) (*FeishuChan
 
 	ch := &FeishuChannel{
 		BaseChannel: base,
-		feishuCfg:   cfg,
+		config:      cfg,
 		client:      lark.NewClient(cfg.AppID, cfg.AppSecret),
 	}
 	ch.SetOwner(ch)
@@ -54,13 +56,18 @@ func NewFeishuChannel(cfg config.FeishuConfig, bus *bus.MessageBus) (*FeishuChan
 }
 
 func (c *FeishuChannel) Start(ctx context.Context) error {
-	if c.feishuCfg.AppID == "" || c.feishuCfg.AppSecret == "" {
+	if c.config.AppID == "" || c.config.AppSecret == "" {
 		return fmt.Errorf("feishu app_id or app_secret is empty")
 	}
 
-	// Bot open_id for @mention detection is populated lazily from the first mention event.
+	// Fetch bot open_id via API for reliable @mention detection.
+	if err := c.fetchBotOpenID(ctx); err != nil {
+		logger.ErrorCF("feishu", "Failed to fetch bot open_id, @mention detection may not work", map[string]any{
+			"error": err.Error(),
+		})
+	}
 
-	dispatcher := larkdispatcher.NewEventDispatcher(c.feishuCfg.VerificationToken, c.feishuCfg.EncryptKey).
+	dispatcher := larkdispatcher.NewEventDispatcher(c.config.VerificationToken, c.config.EncryptKey).
 		OnP2MessageReceiveV1(c.handleMessageReceive)
 
 	runCtx, cancel := context.WithCancel(ctx)
@@ -68,8 +75,8 @@ func (c *FeishuChannel) Start(ctx context.Context) error {
 	c.mu.Lock()
 	c.cancel = cancel
 	c.wsClient = larkws.NewClient(
-		c.feishuCfg.AppID,
-		c.feishuCfg.AppSecret,
+		c.config.AppID,
+		c.config.AppSecret,
 		larkws.WithEventHandler(dispatcher),
 	)
 	wsClient := c.wsClient
@@ -147,14 +154,14 @@ func (c *FeishuChannel) EditMessage(ctx context.Context, chatID, messageID, cont
 // SendPlaceholder implements channels.PlaceholderCapable.
 // Sends an interactive card with placeholder text and returns its message ID.
 func (c *FeishuChannel) SendPlaceholder(ctx context.Context, chatID string) (string, error) {
-	if !c.feishuCfg.Placeholder.Enabled {
+	if !c.config.Placeholder.Enabled {
 		logger.DebugCF("feishu", "Placeholder disabled, skipping", map[string]any{
 			"chat_id": chatID,
 		})
 		return "", nil
 	}
 
-	text := c.feishuCfg.Placeholder.Text
+	text := c.config.Placeholder.Text
 	if text == "" {
 		text = "Thinking..."
 	}
@@ -409,6 +416,40 @@ func (c *FeishuChannel) handleMessageReceive(ctx context.Context, event *larkim.
 
 // --- Internal helpers ---
 
+// fetchBotOpenID calls the Feishu bot info API to retrieve and store the bot's open_id.
+func (c *FeishuChannel) fetchBotOpenID(ctx context.Context) error {
+	resp, err := c.client.Do(ctx, &larkcore.ApiReq{
+		HttpMethod:                http.MethodGet,
+		ApiPath:                   "/open-apis/bot/v3/info",
+		SupportedAccessTokenTypes: []larkcore.AccessTokenType{larkcore.AccessTokenTypeTenant},
+	})
+	if err != nil {
+		return fmt.Errorf("bot info request: %w", err)
+	}
+
+	var result struct {
+		Code int `json:"code"`
+		Bot  struct {
+			OpenID string `json:"open_id"`
+		} `json:"bot"`
+	}
+	if err := json.Unmarshal(resp.RawBody, &result); err != nil {
+		return fmt.Errorf("bot info parse: %w", err)
+	}
+	if result.Code != 0 {
+		return fmt.Errorf("bot info api error (code=%d)", result.Code)
+	}
+	if result.Bot.OpenID == "" {
+		return fmt.Errorf("bot info: empty open_id")
+	}
+
+	c.botOpenID.Store(result.Bot.OpenID)
+	logger.InfoCF("feishu", "Fetched bot open_id from API", map[string]any{
+		"open_id": result.Bot.OpenID,
+	})
+	return nil
+}
+
 // isBotMentioned checks if the bot was @mentioned in the message.
 func (c *FeishuChannel) isBotMentioned(message *larkim.EventMessage) bool {
 	if message.Mentions == nil {
@@ -416,23 +457,16 @@ func (c *FeishuChannel) isBotMentioned(message *larkim.EventMessage) bool {
 	}
 
 	knownID, _ := c.botOpenID.Load().(string)
+	if knownID == "" {
+		logger.DebugCF("feishu", "Bot open_id unknown, cannot detect @mention", nil)
+		return false
+	}
 
 	for _, m := range message.Mentions {
 		if m.Id == nil {
 			continue
 		}
-		// If we already know the bot's open_id, match against it.
-		if m.Id.OpenId != nil && knownID != "" && *m.Id.OpenId == knownID {
-			return true
-		}
-		// If we don't know our bot open_id yet, use a reliable heuristic:
-		// Feishu assigns @_user_1 as the key for the first mention (the bot itself)
-		// when a user @mentions the bot. Only trust this specific key.
-		if knownID == "" && m.Key != nil && *m.Key == "@_user_1" && m.Id.OpenId != nil {
-			c.botOpenID.Store(*m.Id.OpenId)
-			logger.DebugCF("feishu", "Detected bot open_id from @_user_1 mention", map[string]any{
-				"open_id": *m.Id.OpenId,
-			})
+		if m.Id.OpenId != nil && *m.Id.OpenId == knownID {
 			return true
 		}
 	}
@@ -587,7 +621,6 @@ func (c *FeishuChannel) downloadResource(
 		})
 		return ""
 	}
-	defer out.Close()
 
 	if _, copyErr := io.Copy(out, resp.File); copyErr != nil {
 		out.Close()
@@ -597,6 +630,7 @@ func (c *FeishuChannel) downloadResource(
 		})
 		return ""
 	}
+	out.Close()
 
 	ref, err := store.Store(localPath, media.MediaMeta{
 		Filename: filename,

pkg/channels/feishu/feishu_64_test.go

@@ -0,0 +1,256 @@
+//go:build amd64 || arm64 || riscv64 || mips64 || ppc64
+
+package feishu
+
+import (
+	"testing"
+
+	larkim "github.com/larksuite/oapi-sdk-go/v3/service/im/v1"
+)
+
+func TestExtractContent(t *testing.T) {
+	tests := []struct {
+		name        string
+		messageType string
+		rawContent  string
+		want        string
+	}{
+		{
+			name:        "text message",
+			messageType: "text",
+			rawContent:  `{"text": "hello world"}`,
+			want:        "hello world",
+		},
+		{
+			name:        "text message invalid JSON",
+			messageType: "text",
+			rawContent:  `not json`,
+			want:        "not json",
+		},
+		{
+			name:        "post message returns raw JSON",
+			messageType: "post",
+			rawContent:  `{"title": "test post"}`,
+			want:        `{"title": "test post"}`,
+		},
+		{
+			name:        "image message returns empty",
+			messageType: "image",
+			rawContent:  `{"image_key": "img_xxx"}`,
+			want:        "",
+		},
+		{
+			name:        "file message with filename",
+			messageType: "file",
+			rawContent:  `{"file_key": "file_xxx", "file_name": "report.pdf"}`,
+			want:        "report.pdf",
+		},
+		{
+			name:        "file message without filename",
+			messageType: "file",
+			rawContent:  `{"file_key": "file_xxx"}`,
+			want:        "",
+		},
+		{
+			name:        "audio message with filename",
+			messageType: "audio",
+			rawContent:  `{"file_key": "file_xxx", "file_name": "recording.ogg"}`,
+			want:        "recording.ogg",
+		},
+		{
+			name:        "media message with filename",
+			messageType: "media",
+			rawContent:  `{"file_key": "file_xxx", "file_name": "video.mp4"}`,
+			want:        "video.mp4",
+		},
+		{
+			name:        "unknown message type returns raw",
+			messageType: "sticker",
+			rawContent:  `{"sticker_id": "sticker_xxx"}`,
+			want:        `{"sticker_id": "sticker_xxx"}`,
+		},
+		{
+			name:        "empty raw content",
+			messageType: "text",
+			rawContent:  "",
+			want:        "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractContent(tt.messageType, tt.rawContent)
+			if got != tt.want {
+				t.Errorf("extractContent(%q, %q) = %q, want %q", tt.messageType, tt.rawContent, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestAppendMediaTags(t *testing.T) {
+	tests := []struct {
+		name        string
+		content     string
+		messageType string
+		mediaRefs   []string
+		want        string
+	}{
+		{
+			name:        "no refs returns content unchanged",
+			content:     "hello",
+			messageType: "image",
+			mediaRefs:   nil,
+			want:        "hello",
+		},
+		{
+			name:        "empty refs returns content unchanged",
+			content:     "hello",
+			messageType: "image",
+			mediaRefs:   []string{},
+			want:        "hello",
+		},
+		{
+			name:        "image with content",
+			content:     "check this",
+			messageType: "image",
+			mediaRefs:   []string{"ref1"},
+			want:        "check this [image: photo]",
+		},
+		{
+			name:        "image empty content",
+			content:     "",
+			messageType: "image",
+			mediaRefs:   []string{"ref1"},
+			want:        "[image: photo]",
+		},
+		{
+			name:        "audio",
+			content:     "listen",
+			messageType: "audio",
+			mediaRefs:   []string{"ref1"},
+			want:        "listen [audio]",
+		},
+		{
+			name:        "media/video",
+			content:     "watch",
+			messageType: "media",
+			mediaRefs:   []string{"ref1"},
+			want:        "watch [video]",
+		},
+		{
+			name:        "file",
+			content:     "report.pdf",
+			messageType: "file",
+			mediaRefs:   []string{"ref1"},
+			want:        "report.pdf [file]",
+		},
+		{
+			name:        "unknown type",
+			content:     "something",
+			messageType: "sticker",
+			mediaRefs:   []string{"ref1"},
+			want:        "something [attachment]",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := appendMediaTags(tt.content, tt.messageType, tt.mediaRefs)
+			if got != tt.want {
+				t.Errorf(
+					"appendMediaTags(%q, %q, %v) = %q, want %q",
+					tt.content,
+					tt.messageType,
+					tt.mediaRefs,
+					got,
+					tt.want,
+				)
+			}
+		})
+	}
+}
+
+func TestExtractFeishuSenderID(t *testing.T) {
+	strPtr := func(s string) *string { return &s }
+
+	tests := []struct {
+		name   string
+		sender *larkim.EventSender
+		want   string
+	}{
+		{
+			name:   "nil sender",
+			sender: nil,
+			want:   "",
+		},
+		{
+			name:   "nil sender ID",
+			sender: &larkim.EventSender{SenderId: nil},
+			want:   "",
+		},
+		{
+			name: "userId preferred",
+			sender: &larkim.EventSender{
+				SenderId: &larkim.UserId{
+					UserId:  strPtr("u_abc123"),
+					OpenId:  strPtr("ou_def456"),
+					UnionId: strPtr("on_ghi789"),
+				},
+			},
+			want: "u_abc123",
+		},
+		{
+			name: "openId fallback",
+			sender: &larkim.EventSender{
+				SenderId: &larkim.UserId{
+					UserId:  strPtr(""),
+					OpenId:  strPtr("ou_def456"),
+					UnionId: strPtr("on_ghi789"),
+				},
+			},
+			want: "ou_def456",
+		},
+		{
+			name: "unionId fallback",
+			sender: &larkim.EventSender{
+				SenderId: &larkim.UserId{
+					UserId:  strPtr(""),
+					OpenId:  strPtr(""),
+					UnionId: strPtr("on_ghi789"),
+				},
+			},
+			want: "on_ghi789",
+		},
+		{
+			name: "all empty strings",
+			sender: &larkim.EventSender{
+				SenderId: &larkim.UserId{
+					UserId:  strPtr(""),
+					OpenId:  strPtr(""),
+					UnionId: strPtr(""),
+				},
+			},
+			want: "",
+		},
+		{
+			name: "nil userId pointer falls through",
+			sender: &larkim.EventSender{
+				SenderId: &larkim.UserId{
+					UserId:  nil,
+					OpenId:  strPtr("ou_def456"),
+					UnionId: nil,
+				},
+			},
+			want: "ou_def456",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractFeishuSenderID(tt.sender)
+			if got != tt.want {
+				t.Errorf("extractFeishuSenderID() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}