diff --git a/core/playlists/parse_nsp_test.go b/core/playlists/parse_nsp_test.go
index 516a5355d..d6d69866f 100644
--- a/core/playlists/parse_nsp_test.go
+++ b/core/playlists/parse_nsp_test.go
@@ -113,6 +113,20 @@ var _ = Describe("parseNSP", func() {
 		Expect(err.Error()).To(ContainSubstring("SmartPlaylist"))
 	})
 
+	It("rejects a NSP that mixes top-level 'any' and 'all' instead of silently dropping a group", func() {
+		nsp := `{
+			"name": "Overplayed Favorites",
+			"any": [{"inPlaylist": {"path": "most-played-favorites.nsp"}}],
+			"all": [{"notInPlaylist": {"path": "favorites-not-played-in-4-yrs.nsp"}}],
+			"sort": "playCount, lastPlayed"
+		}`
+		pls := &model.Playlist{}
+		err := s.parseNSP(ctx, pls, strings.NewReader(nsp))
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("SmartPlaylist"))
+		Expect(err.Error()).To(And(ContainSubstring("all"), ContainSubstring("any")))
+	})
+
 	It("gracefully handles non-string name field", func() {
 		nsp := `{"name": 123, "all": [{"is": {"loved": true}}]}`
 		pls := &model.Playlist{Name: "Original"}
diff --git a/model/criteria/criteria.go b/model/criteria/criteria.go
index 31d208d08..8c3d183a9 100644
--- a/model/criteria/criteria.go
+++ b/model/criteria/criteria.go
@@ -103,21 +103,26 @@ func (c Criteria) MarshalJSON() ([]byte, error) {
 
 func (c *Criteria) UnmarshalJSON(data []byte) error {
 	var aux struct {
-		All          unmarshalConjunctionType `json:"all"`
-		Any          unmarshalConjunctionType `json:"any"`
-		Sort         string                   `json:"sort"`
-		Order        string                   `json:"order"`
-		Limit        int                      `json:"limit"`
-		LimitPercent int                      `json:"limitPercent"`
-		Offset       int                      `json:"offset"`
+		All          optionalConjunction `json:"all"`
+		Any          optionalConjunction `json:"any"`
+		Sort         string              `json:"sort"`
+		Order        string              `json:"order"`
+		Limit        int                 `json:"limit"`
+		LimitPercent int                 `json:"limitPercent"`
+		Offset       int                 `json:"offset"`
 	}
 	if err := json.Unmarshal(data, &aux); err != nil {
 		return err
 	}
-	if len(aux.Any) > 0 {
-		c.Expression = Any(aux.Any)
-	} else if len(aux.All) > 0 {
-		c.Expression = All(aux.All)
+	// A Criteria has a single top-level group. Reject files that provide both keys
+	// (even when one is [] or null) rather than silently dropping one of them.
+	if aux.All.present && aux.Any.present {
+		return errors.New("invalid criteria json: 'all' and 'any' cannot both be used at the top level; nest one inside the other instead")
+	}
+	if len(aux.Any.rules) > 0 {
+		c.Expression = Any(aux.Any.rules)
+	} else if len(aux.All.rules) > 0 {
+		c.Expression = All(aux.All.rules)
 	} else {
 		return errors.New("invalid criteria json. missing rules (key 'all' or 'any')")
 	}
diff --git a/model/criteria/criteria_test.go b/model/criteria/criteria_test.go
index 092cfd36a..7f214e703 100644
--- a/model/criteria/criteria_test.go
+++ b/model/criteria/criteria_test.go
@@ -80,6 +80,28 @@ var _ = Describe("Criteria", func() {
 		})
 	})
 
+	Context("with both top-level 'all' and 'any'", func() {
+		It("returns an error instead of silently dropping one of the groups", func() {
+			jsonStr := `{"any":[{"inPlaylist":{"path":"a.nsp"}}],"all":[{"notInPlaylist":{"path":"b.nsp"}}]}`
+			var c Criteria
+			err := json.Unmarshal([]byte(jsonStr), &c)
+			gomega.Expect(err).To(gomega.HaveOccurred())
+			gomega.Expect(err.Error()).To(gomega.And(gomega.ContainSubstring("all"), gomega.ContainSubstring("any")))
+		})
+
+		DescribeTable("rejects both keys even when one group is present but empty",
+			func(jsonStr string) {
+				var c Criteria
+				err := json.Unmarshal([]byte(jsonStr), &c)
+				gomega.Expect(err).To(gomega.HaveOccurred())
+				gomega.Expect(err.Error()).To(gomega.And(gomega.ContainSubstring("all"), gomega.ContainSubstring("any")))
+			},
+			Entry("empty any", `{"any":[],"all":[{"is":{"loved":true}}]}`),
+			Entry("empty all", `{"all":[],"any":[{"is":{"loved":true}}]}`),
+			Entry("null any", `{"any":null,"all":[{"is":{"loved":true}}]}`),
+		)
+	})
+
 	Describe("LimitPercent", func() {
 		Describe("JSON round-trip", func() {
 			It("marshals and unmarshals limitPercent", func() {
diff --git a/model/criteria/json.go b/model/criteria/json.go
index beded9d1f..d0f453524 100644
--- a/model/criteria/json.go
+++ b/model/criteria/json.go
@@ -33,6 +33,20 @@ func (uc *unmarshalConjunctionType) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
+// optionalConjunction is a top-level "all"/"any" value that remembers whether its
+// key was present at all, so a Criteria providing both can be rejected. encoding/json
+// calls UnmarshalJSON even for a JSON null, so present is set whenever the key appears
+// — including as [] or null — while an absent key leaves it false.
+type optionalConjunction struct {
+	present bool
+	rules   unmarshalConjunctionType
+}
+
+func (o *optionalConjunction) UnmarshalJSON(data []byte) error {
+	o.present = true
+	return json.Unmarshal(data, &o.rules)
+}
+
 func unmarshalExpression(opName string, rawValue json.RawMessage) Expression {
 	m := make(map[string]any)
 	err := json.Unmarshal(rawValue, &m)