diff --git a/internal/service/adult_image_crop.go b/internal/service/adult_image_crop.go
index 411f99d..31c41bf 100644
--- a/internal/service/adult_image_crop.go
+++ b/internal/service/adult_image_crop.go
@@ -73,17 +73,17 @@ func CropAdultCoverPosterForCode(data []byte, code string) ([]byte, string, erro
 	}
 	src, format, err := image.Decode(bytes.NewReader(data))
 	if err != nil {
-		return data, format, err
+		return data, imageMIMEForFormat(format), err
 	}
 	bounds := src.Bounds()
 	width := bounds.Dx()
 	height := bounds.Dy()
 	if width <= 0 || height <= 0 {
-		return data, format, nil
+		return data, imageMIMEForFormat(format), nil
 	}
 	// If the image is already portrait or square, keep it as-is.
 	if float64(width) <= float64(height)*1.15 {
-		return data, format, nil
+		return data, imageMIMEForFormat(format), nil
 	}
 
 	position := 1.0
@@ -101,6 +101,26 @@ func CropAdultCoverPosterForCode(data []byte, code string) ([]byte, string, erro
 	return buf.Bytes(), "image/jpeg", nil
 }
 
+// imageMIMEForFormat maps the format name returned by image.Decode ("jpeg" / "png" / "webp" …) to a MIME
+// type. The sidecar extension is derived from the MIME type, so handing back the bare format name made
+// every already-portrait poster fall through to the legacy ".img" extension.
+func imageMIMEForFormat(format string) string {
+	switch strings.ToLower(strings.TrimSpace(format)) {
+	case "jpeg", "jpg":
+		return "image/jpeg"
+	case "png":
+		return "image/png"
+	case "webp":
+		return "image/webp"
+	case "gif":
+		return "image/gif"
+	case "avif":
+		return "image/avif"
+	default:
+		return ""
+	}
+}
+
 // adultCoverNeedsFaceDetection reports whether the cover composition has to be probed with the face
 // detector, mirroring upstream MetaTube: only "special" numbers (FC2 / HEYZO / 素人 / 无码) qualify,
 // regular DVD numbers are always cropped at the right-most panel.
diff --git a/internal/service/adult_image_crop_test.go b/internal/service/adult_image_crop_test.go
index 4eead39..25cfe03 100644
--- a/internal/service/adult_image_crop_test.go
+++ b/internal/service/adult_image_crop_test.go
@@ -167,10 +167,14 @@ func TestCropAdultCoverPosterKeepsPortrait(t *testing.T) {
 	// Create an already vertical portrait image (500x700)
 	origBytes := createTestImage(500, 700, color.RGBA{R: 255, A: 255}, color.RGBA{B: 255, A: 255})
 
-	croppedBytes, _, err := CropAdultCoverPoster(origBytes)
+	croppedBytes, ctype, err := CropAdultCoverPoster(origBytes)
 	if err != nil {
 		t.Fatalf("CropAdultCoverPoster error: %v", err)
 	}
+	// 未裁剪时必须回传真正的 MIME（image/jpeg），否则侧车文件扩展名会退化成 .img。
+	if ctype != "image/jpeg" {
+		t.Fatalf("portrait ctype = %q, want image/jpeg", ctype)
+	}
 
 	croppedImg, _, err := image.Decode(bytes.NewReader(croppedBytes))
 	if err != nil {
diff --git a/internal/service/adult_scraper_routing_test.go b/internal/service/adult_scraper_routing_test.go
index 36e0e29..f754b94 100644
--- a/internal/service/adult_scraper_routing_test.go
+++ b/internal/service/adult_scraper_routing_test.go
@@ -96,7 +96,8 @@ func TestAdultProviderRouting(t *testing.T) {
 	if len(candidates) != 1 {
 		t.Fatalf("expected 1 candidate, got %d", len(candidates))
 	}
-	wantPoster := mtServer.URL + "/v1/images/primary/javdb/999?auto=true&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fposter.jpg"
+	// SSIS-001 是常规番号：MetaTube 代理不得开启人脸定位，固定取最右侧封面面板。
+	wantPoster := mtServer.URL + "/v1/images/primary/javdb/999?auto=false&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fposter.jpg"
 	wantBackdrop := mtServer.URL + "/v1/images/backdrop/javdb/999?quality=90"
 	if candidates[0].PosterURL != wantPoster || candidates[0].BackdropURL != wantBackdrop {
 		t.Fatalf("candidate artwork was not enriched: %#v", candidates[0])
@@ -170,8 +171,8 @@ func TestBuiltinAdultScrapeUsesMetaTubeFaceAwareArtwork(t *testing.T) {
 	if match == nil {
 		t.Fatal("expected built-in match")
 	}
-	wantPoster := metaTubeServer.URL + "/v1/images/primary/AVE/999?auto=true&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fwide-cover.jpg"
+	wantPoster := metaTubeServer.URL + "/v1/images/primary/AVE/999?auto=false&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fwide-cover.jpg"
 	if match.PosterURL != wantPoster {
-		t.Fatalf("built-in poster = %q, want face-aware URL %q", match.PosterURL, wantPoster)
+		t.Fatalf("built-in poster = %q, want MetaTube-processed URL %q", match.PosterURL, wantPoster)
 	}
 }
diff --git a/internal/service/manual_scrape_test.go b/internal/service/manual_scrape_test.go
index 22d7743..f18ae77 100644
--- a/internal/service/manual_scrape_test.go
+++ b/internal/service/manual_scrape_test.go
@@ -93,7 +93,7 @@ func TestManualAdultMatchUsesSelectedMetaTubeDetailsAndRealBackdrop(t *testing.T
 	if detailCalls.Load() != 1 {
 		t.Fatalf("selected MetaTube detail calls = %d, want 1", detailCalls.Load())
 	}
-	wantPoster := upstream.URL + "/v1/images/primary/AVE/94600?auto=true&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fposter.jpg"
+	wantPoster := upstream.URL + "/v1/images/primary/AVE/94600?auto=false&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fposter.jpg"
 	if match.PosterURL != wantPoster {
 		t.Fatalf("selected poster = %q, want %q", match.PosterURL, wantPoster)
 	}
diff --git a/internal/service/metatube.go b/internal/service/metatube.go
index d3fb3b3..12a51fa 100644
--- a/internal/service/metatube.go
+++ b/internal/service/metatube.go
@@ -352,7 +352,7 @@ func (p *MetaTubeProvider) convertSearchResultToMatch(cfg MetaTubeConfig, query
 	year := parseYearFromDate(res.ReleaseDate)
 
 	posterSource := firstNonEmpty(res.BigCoverURL, res.CoverURL, res.BigThumbURL, res.ThumbURL)
-	posterURL, backdropURL := metaTubeArtworkURLs(cfg, res.Provider, res.ID, posterSource)
+	posterURL, backdropURL := metaTubeArtworkURLs(cfg, res.Provider, res.ID, posterSource, code)
 	if posterURL == "" {
 		posterURL = firstNonEmpty(res.BigThumbURL, res.ThumbURL, res.BigCoverURL, res.CoverURL)
 	}
@@ -396,7 +396,7 @@ func (p *MetaTubeProvider) convertMovieInfoToMatch(cfg MetaTubeConfig, movie *Me
 	year := parseYearFromDate(movie.ReleaseDate)
 
 	posterSource := firstNonEmpty(movie.BigCoverURL, movie.CoverURL, movie.BigThumbURL, movie.ThumbURL)
-	posterURL, backdropURL := metaTubeArtworkURLs(cfg, movie.Provider, movie.ID, posterSource)
+	posterURL, backdropURL := metaTubeArtworkURLs(cfg, movie.Provider, movie.ID, posterSource, code)
 	if posterURL == "" {
 		posterURL = firstNonEmpty(movie.BigThumbURL, movie.ThumbURL, movie.BigCoverURL, movie.CoverURL)
 	}
@@ -440,7 +440,13 @@ func (p *MetaTubeProvider) convertMovieInfoToMatch(cfg MetaTubeConfig, movie *Me
 	}
 }
 
-func metaTubeArtworkURLs(cfg MetaTubeConfig, provider, id, posterSource string) (string, string) {
+// metaTubeArtworkURLs 构造 MetaTube 图片代理地址。
+//
+// auto（服务端人脸定位）只能对特殊番号（FC2 / HEYZO / 素人 / 无码）开启，这与 MetaTube
+// 官方插件的默认行为一致：常规 DVD 番号的封套是 [封底 | 书脊 | 封面] 横图，封底那半张是样本
+// 剧照拼贴、密布人脸，服务端的人脸主簇会落到拼贴/书脊上，裁出来就是「半张封底」。
+// 常规番号固定 pos=1（最右侧封面面板）才能拿到正确封面。
+func metaTubeArtworkURLs(cfg MetaTubeConfig, provider, id, posterSource, code string) (string, string) {
 	serverURL := strings.TrimRight(strings.TrimSpace(cfg.ServerURL), "/")
 	provider = strings.TrimSpace(provider)
 	id = strings.TrimSpace(id)
@@ -459,7 +465,7 @@ func metaTubeArtworkURLs(cfg MetaTubeConfig, provider, id, posterSource string)
 			}
 			if cfg.CropCover {
 				values.Set("pos", "1")
-				values.Set("auto", "true")
+				values.Set("auto", strconv.FormatBool(adultCoverNeedsFaceDetection(code)))
 			} else {
 				values.Set("pos", "-1")
 				values.Set("auto", "false")
diff --git a/internal/service/metatube_test.go b/internal/service/metatube_test.go
index 1dd32d1..4803cda 100644
--- a/internal/service/metatube_test.go
+++ b/internal/service/metatube_test.go
@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 
 	"go.uber.org/zap"
@@ -137,7 +138,8 @@ func TestMetaTubeProviderGetMovie(t *testing.T) {
 	if match.Overview != "超绝美少女相沢みなみ出道作品！" {
 		t.Errorf("unexpected overview: %s", match.Overview)
 	}
-	if want := server.URL + "/v1/images/primary/javdb/123456?auto=true&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fbig_cover.jpg"; match.PosterURL != want {
+	// IPX-235 是常规 DVD 番号：服务端不得开启人脸定位（auto=false），否则主簇会落到封底的剧照拼贴。
+	if want := server.URL + "/v1/images/primary/javdb/123456?auto=false&pos=1&quality=90&ratio=-1&url=https%3A%2F%2Fexample.com%2Fbig_cover.jpg"; match.PosterURL != want {
 		t.Errorf("poster URL = %q, want %q", match.PosterURL, want)
 	}
 	if want := server.URL + "/v1/images/backdrop/javdb/123456?quality=90"; match.BackdropURL != want {
@@ -187,3 +189,30 @@ func TestMetaTubeProviderTestConnection(t *testing.T) {
 		t.Fatalf("expected failure for wrong token, got %v", resFail)
 	}
 }
+
+// MetaTube 代理的 auto 参数决定服务端是否用 Pigo 做人脸定位裁切。
+// 常规 DVD 番号的封套封底是剧照拼贴、密布人脸，开启 auto 会裁出「半张封底」；
+// 只有 FC2 / HEYZO / 素人 / 无码这类构图不固定的封面才应该开启。
+func TestMetaTubeArtworkURLsFaceDetectionPolicy(t *testing.T) {
+	cfg := MetaTubeConfig{ServerURL: "https://mt.example", CropCover: true}
+	cases := []struct {
+		code     string
+		wantAuto string
+	}{
+		{"IPX-235", "false"},
+		{"SSNI-677", "false"},
+		{"NGOD-361", "false"},
+		{"FC2-PPV-482896", "true"},
+		{"HEYZO-1234", "true"},
+		{"123456-789", "true"},
+	}
+	for _, c := range cases {
+		poster, _ := metaTubeArtworkURLs(cfg, "javdb", "123456", "https://example.com/pl.jpg", c.code)
+		if !strings.Contains(poster, "auto="+c.wantAuto) {
+			t.Errorf("%s: poster URL = %q, want auto=%s", c.code, poster, c.wantAuto)
+		}
+		if !strings.Contains(poster, "pos=1") {
+			t.Errorf("%s: poster URL = %q, want pos=1", c.code, poster)
+		}
+	}
+}
diff --git a/internal/service/scraper_write_metadata_files.go b/internal/service/scraper_write_metadata_files.go
index 3d63f5e..bb860c9 100644
--- a/internal/service/scraper_write_metadata_files.go
+++ b/internal/service/scraper_write_metadata_files.go
@@ -140,7 +140,10 @@ func (s *ScraperService) downloadArtworkToPathWithOptions(ctx context.Context, d
 	if cropAdultPoster {
 		if cropped, croppedType, err := CropAdultCoverPosterForCode(data, adultCode); err == nil && len(cropped) > 0 {
 			data = cropped
-			ctype = croppedType
+			// 裁剪函数在“无需裁剪”时会原样返回，类型可能为空：此时保留 sniff 出来的 MIME。
+			if strings.TrimSpace(croppedType) != "" {
+				ctype = croppedType
+			}
 		}
 	}
 	return s.writeArtworkDataToPath(dir, name, ctype, data)
@@ -197,9 +200,25 @@ func (s *ScraperService) writeArtworkDataToPath(dir, name, ctype string, data []
 		return ""
 	}
 	s.log.Debug("scrape artwork written", zap.String("dst", dst))
+	s.removeLegacyArtworkImg(dir, name, dst)
 	return dst
 }
 
+// removeLegacyArtworkImg 清理同名历史 "<name>.img" 文件。
+//
+// 早期版本把 image.Decode 的格式名（"jpeg"/"webp"）当作 MIME 写进扩展名映射，
+// 导致这些海报全部以 .img 落盘。现在写出正确扩展名后，旧 .img 只会是孤立垃圾，
+// 但 local_metadata_artwork 仍会扫到它，所以一并清掉。
+func (s *ScraperService) removeLegacyArtworkImg(dir, name, dst string) {
+	legacy := filepath.Join(dir, name+".img")
+	if strings.EqualFold(legacy, dst) {
+		return
+	}
+	if err := os.Remove(legacy); err == nil {
+		s.log.Debug("scrape artwork removed legacy .img", zap.String("dst", legacy))
+	}
+}
+
 // artworkFileUnchanged 报告 path 是否已经就是 data 这些字节。
 //
 // 刮削在刷新海报地址时会无条件重写 sidecar 图片，即使下载回来的字节一模一样。
diff --git a/internal/service/scraper_write_metadata_files_test.go b/internal/service/scraper_write_metadata_files_test.go
index 9cf945b..4ae98c4 100644
--- a/internal/service/scraper_write_metadata_files_test.go
+++ b/internal/service/scraper_write_metadata_files_test.go
@@ -172,6 +172,31 @@ func TestDownloadArtworkMigratesLocalImgToCanonicalCroppedJPEG(t *testing.T) {
 	}
 }
 
+// 已经裁好的竖版海报（例如 MetaTube 服务端裁好的 2:3 图）再次写入时不能再退化成 .img：
+// 早期版本把 image.Decode 的格式名当 MIME 用，落盘扩展名就成了 .img。
+func TestDownloadArtworkKeepsCanonicalExtensionForPortraitSource(t *testing.T) {
+	scraper := &ScraperService{log: zap.NewNop()}
+	dir := t.TempDir()
+	src := filepath.Join(dir, "movie-poster-src.jpg")
+	portrait := createTestImage(400, 600, color.RGBA{R: 255, A: 255}, color.RGBA{B: 255, A: 255})
+	if err := os.WriteFile(src, portrait, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	// 模拟历史遗留的 .img 退格式文件。
+	legacy := filepath.Join(dir, "movie-poster.img")
+	if err := os.WriteFile(legacy, portrait, 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	dst := scraper.downloadArtworkToPathWithOptions(t.Context(), dir, "movie-poster", src, true, "SSNI-677")
+	if filepath.Base(dst) != "movie-poster.jpg" {
+		t.Fatalf("destination = %q, want canonical .jpg (not .img)", dst)
+	}
+	if _, err := os.Stat(legacy); !os.IsNotExist(err) {
+		t.Fatalf("legacy .img should be cleaned up, stat err = %v", err)
+	}
+}
+
 // TestWriteMediaArtworkFilesAfterScrapeSkipsCloud verifies that cloud media
 // never has artwork written anywhere.
 func TestWriteMediaArtworkFilesAfterScrapeSkipsCloud(t *testing.T) {