check front face specifically for type legality

src/lib/__tests__/test-cards.json

···
 	"Barkchannel Pathway": "59d22de5-e310-44d7-89cf-ef3529e40cef",
 	"Basking Broodscale": "a7c69802-99c4-4778-934e-cc09ba58c267",
 	"Beastcaller Savant": "e28227eb-b3b5-42fa-b597-1fefd2a70186",
+	"Behold the Unspeakable": "464372ef-0b16-4b8d-ba6f-fbf5c905c479",
 	"Beloved Chaplain": "a07406b7-faa1-4ed3-ab84-314c40f3f7f1",
 	"Bird Admirer": "58bd02ae-2676-4c9c-b24e-2bd51be8bde7",
 	"Birds of Paradise": "d3a0b660-358c-41bd-9cd2-41fbf3491b1a",

src/lib/deck-validation/__tests__/rules.test.ts

···
 			const violations = commanderUncommonRule.validate(ctx);
 			expect(violations).toHaveLength(0);
 		});
+
+		it("rejects DFC saga that transforms into creature (front face check)", async () => {
+			// Behold the Unspeakable has an uncommon printing and transforms into
+			// a legendary creature, but the FRONT face is a Saga - not legal for PDH
+			const behold = await cards.get("Behold the Unspeakable");
+			const deck = makeDeck([makeCard(behold, "commander")], "paupercommander");
+			const printingsMap = new Map<OracleId, Card[]>();
+			printingsMap.set(behold.oracle_id, [
+				mockPrinting(behold, "uncommon", ["paper"]),
+			]);
+			const ctx = await makeContextWithCards(
+				deck,
+				[behold],
+				undefined,
+				printingsMap,
+			);
+			const violations = commanderUncommonRule.validate(ctx);
+			expect(violations).toHaveLength(1);
+			expect(violations[0].message).toContain("not a creature");
+		});
 	});
 
 	describe("signatureSpellRule color identity", () => {

src/lib/deck-validation/rules/commander.ts

···
 	type Violation,
 	violation,
 } from "../types";
-import { getOracleText, getTypeLine } from "../utils";
+import { getFrontFaceTypeLine, getOracleText, getTypeLine } from "../utils";
 
 /**
  * Commander required - at least one commander
···
 /**
  * Check if card has a creature type valid for commander (creature, vehicle, spacecraft with P/T).
  * Shared between regular Commander and PDH validation.
+ *
+ * For DFCs/MDFCs, checks the FRONT FACE only - a Saga that transforms into
+ * a creature (e.g., Behold the Unspeakable) is NOT a legal commander.
  */
 export function hasCommanderCreatureType(card: Card): boolean {
-	const typeLine = getTypeLine(card).toLowerCase();
+	const typeLine = getFrontFaceTypeLine(card).toLowerCase();
 
 	if (typeLine.includes("creature")) return true;
 	if (typeLine.includes("vehicle")) return true;
···
 }
 
 export function isValidCommanderType(card: Card): boolean {
-	const typeLine = getTypeLine(card).toLowerCase();
+	const frontTypeLine = getFrontFaceTypeLine(card).toLowerCase();
 	const oracleText = getOracleText(card).toLowerCase();
 
-	const isLegendary = typeLine.includes("legendary");
+	const isLegendary = frontTypeLine.includes("legendary");
 	const canBeCommander = oracleText.includes("can be your commander");
 
 	// Grist-style cards: creatures in all zones except battlefield

src/lib/deck-validation/utils.ts

···
 
 	return "";
 }
+
+/**
+ * Get the front face type line only.
+ * For DFCs/MDFCs, commander legality is determined by the front face.
+ * A Saga that transforms into a creature (e.g., Behold the Unspeakable)
+ * is NOT a legal commander because the front face is a Saga.
+ */
+export function getFrontFaceTypeLine(card: Card): string {
+	if (card.card_faces && card.card_faces.length > 0) {
+		return card.card_faces[0].type_line ?? "";
+	}
+	return card.type_line ?? "";
+}