diff --git a/backend/internal/service/channel.go b/backend/internal/service/channel.go
index 154dd67..7f3000a 100644
--- a/backend/internal/service/channel.go
+++ b/backend/internal/service/channel.go
@@ -299,6 +299,13 @@ func normalizeRemoteModel(m upstream.RemoteModel) (ChannelModelSpec, error) {
 	default:
 		return spec, fmt.Errorf("未知类型 %q", spec.Kind)
 	}
+	if spec.Duration != nil {
+		switch spec.Duration.Mode {
+		case "options", "range":
+		default:
+			return spec, errors.New("时长模式仅支持 options / range")
+		}
+	}
 	return spec, nil
 }
 
@@ -432,6 +439,9 @@ func (s *ChannelService) ImportModels(ctx context.Context, channelID string, spe
 		if upID == "" {
 			continue
 		}
+		if spec.Duration != nil && spec.Duration.Mode != "options" && spec.Duration.Mode != "range" {
+			return fmt.Errorf("模型 %s：时长模式仅支持 options / range", upID)
+		}
 		alias := strings.TrimSpace(spec.Alias)
 		if alias == upID {
 			return fmt.Errorf("「%s」别名不能与上游模型同名，留空即可", upID)
@@ -501,9 +511,6 @@ func modelPatchFromSpec(spec ChannelModelSpec, existing *model.ModelConfig) map[
 	}
 	if d := spec.Duration; d != nil {
 		switch d.Mode {
-		case "fixed":
-			patch["durations"] = jsonArray([]string{fmt.Sprintf("%ds", d.Seconds)})
-			patch["duration_min"], patch["duration_max"] = int64(0), int64(0)
 		case "options":
 			opts := make([]string, 0, len(d.Options))
 			for _, s := range d.Options {
diff --git a/backend/internal/service/v1.go b/backend/internal/service/v1.go
index 27f79db..63114d7 100644
--- a/backend/internal/service/v1.go
+++ b/backend/internal/service/v1.go
@@ -342,8 +342,9 @@ type V1ModelItem struct {
 	RefAudioSeconds int64       `json:"refAudioSeconds,omitempty"`
 }
 
-// V1ModelDur exposes a video model's duration capability: fixed=locked seconds,
-// options=discrete list, range=continuous interval.
+// V1ModelDur exposes a video model's duration capability: options=discrete
+// list (single-choice models too — "fixed" is never emitted), range=continuous
+// interval.
 type V1ModelDur struct {
 	Mode    string  `json:"mode"`
 	Seconds int64   `json:"seconds,omitempty"`
@@ -433,20 +434,19 @@ func modelDurationSpec(item *model.ModelConfig) *V1ModelDur {
 		return &V1ModelDur{Mode: "range", Min: int64(item.DurationMin), Max: int64(item.DurationMax)}
 	}
 	opts := repo.JSONStrings(item.Durations)
-	switch len(opts) {
-	case 0:
+	if len(opts) == 0 {
 		return nil
-	case 1:
-		return &V1ModelDur{Mode: "fixed", Seconds: int64(parseDurationSeconds(opts[0]))}
-	default:
-		vals := make([]int64, 0, len(opts))
-		for _, d := range opts {
-			if n := parseDurationSeconds(d); n > 0 {
-				vals = append(vals, int64(n))
-			}
-		}
-		return &V1ModelDur{Mode: "options", Options: vals}
 	}
+	vals := make([]int64, 0, len(opts))
+	for _, d := range opts {
+		if n := parseDurationSeconds(d); n > 0 {
+			vals = append(vals, int64(n))
+		}
+	}
+	if len(vals) == 0 {
+		return nil
+	}
+	return &V1ModelDur{Mode: "options", Options: vals}
 }
 
 // UserBalance — GET /v1/balance. Re-reads the user row so the number is live.
diff --git a/backend/internal/upstream/client.go b/backend/internal/upstream/client.go
index 2810fcf..7cbf2b6 100644
--- a/backend/internal/upstream/client.go
+++ b/backend/internal/upstream/client.go
@@ -102,7 +102,7 @@ type RemoteModel struct {
 
 // RemoteDuration mirrors the duration spec of a vivid model item.
 type RemoteDuration struct {
-	Mode    string  `json:"mode"` // fixed | options | range
+	Mode    string  `json:"mode"` // options | range
 	Seconds int64   `json:"seconds,omitempty"`
 	Min     int64   `json:"min,omitempty"`
 	Max     int64   `json:"max,omitempty"`
diff --git a/frontend/src/views/ChannelsView.vue b/frontend/src/views/ChannelsView.vue
index 7617625..94663fa 100644
--- a/frontend/src/views/ChannelsView.vue
+++ b/frontend/src/views/ChannelsView.vue
@@ -126,8 +126,7 @@ function specText(s) {
   const parts = []
   if (s.qualities?.length) parts.push(s.qualities.join('/'))
   if (s.duration) {
-    if (s.duration.mode === 'fixed') parts.push(`固定 ${s.duration.seconds}s`)
-    else if (s.duration.mode === 'range') parts.push(`${s.duration.min}-${s.duration.max}s`)
+    if (s.duration.mode === 'range') parts.push(`${s.duration.min}-${s.duration.max}s`)
     else if (s.duration.mode === 'options') parts.push((s.duration.options || []).map((d) => `${d}s`).join('/'))
   }
   const refs = []