app/models/__tests__/afl-wildcard-advancement.test.ts

@@ -215,6 +215,14 @@ describe("AFL Wildcard Round advancement", () => {
     expect(row("ef2").participant2Id).toBe(seed(8));
   });
 
+  it("refuses to re-seed an Elimination Final that has already been played", async () => {
+    await winWildcard("wc1", seed(7));
+    Object.assign(row("ef2"), { isComplete: true, winnerId: seed(6), loserId: seed(7) });
+
+    await expect(winWildcard("wc1", seed(10))).rejects.toThrow(/already has a recorded result/);
+    expect(row("ef2").participant2Id).toBe(seed(7));
+  });
+
   it("leaves the bracket alone when the pairings are already right", async () => {
     await winWildcard("wc1", seed(7));
     await winWildcard("wc2", seed(8));

app/models/playoff-match.ts

@@ -942,6 +942,15 @@ async function advanceAFLWinner(
       if (occupant !== null && !wildcardParticipants.has(occupant)) {
         throw new Error(`EF ${efMatch.matchNumber} participant2 already filled`);
       }
+      // Re-seeding a game that has already been played would rewrite who contested a
+      // recorded result. Surface that (this message is not one callers swallow) rather
+      // than quietly corrupting the bracket.
+      if (occupant !== null && (efMatch.isComplete || efMatch.winnerId)) {
+        throw new Error(
+          `Elimination Finals match ${efMatch.matchNumber} already has a recorded result, ` +
+          `so its Wildcard qualifier cannot be re-seeded — clear and regenerate the bracket`
+        );
+      }
       // A Wildcard team in the wrong slot is a placement this result supersedes: a
       // corrected Wildcard winner, or one placed before the re-seeding rule existed.
       if (occupant !== null) slotsToClear.push(efMatch.id);