apps/api/src/services/prestige.ts

@@ -225,7 +225,9 @@ const buildPostPrestigeState = (
 
   const prestigeState: GameState = {
     ...freshState,
-    lastTickAt: Date.now(),
+    // Achievements are permanent — earned achievements survive all prestiges
+    achievements: currentState.achievements,
+    lastTickAt:   Date.now(),
 
     /*
      * Fold current-run totals into lifetime stats so the GameState reflects

apps/api/test/services/prestige.spec.ts

@@ -320,6 +320,20 @@ describe("buildPostPrestigeState", () => {
     expect(prestigeState.player.lifetimeAdventurersRecruited).toBe(5);
   });
 
+  it("preserves achievements from current state across prestige", () => {
+    const achievement = {
+      description: "Did a thing",
+      id:          "ach_persisted",
+      name:        "Achiever",
+      requirement: 1,
+      type:        "totalClicks" as const,
+      unlockedAt:  Date.now(),
+    };
+    const state = makeMinimalState({ achievements: [ achievement ] as GameState["achievements"] });
+    const { prestigeState } = buildPostPrestigeState(state, "Tester");
+    expect(prestigeState.achievements).toEqual([ achievement ]);
+  });
+
   it("accumulates unlocked achievements into lifetime total", () => {
     const achievement = {
       description: "Did a thing",