diff --git a/.agent/logs/refactor-journal.md b/.agent/logs/refactor-journal.md
index 5de6053..e6a3959 100644
--- a/.agent/logs/refactor-journal.md
+++ b/.agent/logs/refactor-journal.md
@@ -15,3 +15,14 @@
     - `src/utils/pyodide/runner.ts`: Split testing logic into dedicated private helper functions.
 - **🧹 Architectural Gain:** SRP — `runPythonCode` now orchestrates execution and simply delegates validation to focused helper functions, increasing readability and testability.
 - **🔬 Verification:** Confirmed that `npx tsc --noEmit` and `npm test` passed successfully.
+
+## 2024-05-18 — [Extract `getEndgameMissionDef` logic]
+
+- **💡 What:** Extracted duplicated logic for finding and hydrating `ENDGAME_MISSIONS` by objective type prefix into a single pure utility function `getEndgameMissionDef`.
+- **🎯 Why:** Code smell identified (DRY violation): the same string parsing `.split('_')[1]`, `.startsWith()`, and hydration logic for endgame missions was duplicated across `missionLogic.ts`, `questionLogic.ts`, and `MissionList.tsx`.
+- **📁 Files Changed:**
+    - `src/utils/gamification/missionLogic.ts`: Added helper and used it in 3 places.
+    - `src/utils/gamification/questionLogic.ts`: Replaced duplicated lookup with helper.
+    - `src/components/gamification/MissionList/MissionList.tsx`: Replaced duplicated lookup with helper.
+- **🧹 Architectural Gain:** DRY principle applied. Centralizing this logic makes modifying endgame mission ID formats or hydration rules much safer, as it only needs to be updated in one place.
+- **🔬 Verification:** Confirmed that `tsc`, `npm test`, `npm run lint`, and `npm run build` all passed.
diff --git a/src/components/gamification/MissionList/MissionList.tsx b/src/components/gamification/MissionList/MissionList.tsx
index 9ce979c..8b64227 100644
--- a/src/components/gamification/MissionList/MissionList.tsx
+++ b/src/components/gamification/MissionList/MissionList.tsx
@@ -1,7 +1,6 @@
 import type { Mission, UserMission } from '../../../types/gamification';
 import './MissionList.css';
-
-import { ENDGAME_MISSIONS } from '../../../data/gamificationData';
+import { getEndgameMissionDef } from '../../../utils/gamification/missionLogic';
 
 interface MissionListProps {
     dailyMissions: Mission[];
@@ -22,15 +21,10 @@ export function MissionList({ dailyMissions, weeklyMissions, userMissions }: Mis
     // Construct Mission objects for them
     const activeEndgameMissions: Mission[] = endgameUserMissions.map(um => {
         // Try to find matching definition
-        // ID format: endgame_{objectiveType}_{index}
-        const typePart = um.missionId.split('_')[1];
-        const def = ENDGAME_MISSIONS.find(m => m.objectiveType === typePart || (typePart === 'improve' && m.objectiveType === 'improve_stars') || (typePart === 'syntax' && m.objectiveType === 'syntax_master'));
+        const def = getEndgameMissionDef(um.missionId);
 
         if (def) {
-            return {
-                ...def,
-                id: um.missionId
-            };
+            return def;
         }
         // Fallback if not found (should not happen if data is consistent)
         return {
diff --git a/src/utils/gamification/missionLogic.ts b/src/utils/gamification/missionLogic.ts
index 80d52a7..8ac5967 100644
--- a/src/utils/gamification/missionLogic.ts
+++ b/src/utils/gamification/missionLogic.ts
@@ -6,6 +6,19 @@ import type {
 import { getLevelFromXP, ENDGAME_MISSIONS, generateDailyMissions, generateWeeklyMissions } from '../../data/gamificationData';
 import { getLocalDateStr } from '../gamificationUtils';
 
+/**
+ * Helper to find and hydrate an endgame mission definition based on its dynamic ID.
+ * Pure function.
+ */
+export function getEndgameMissionDef(missionId: string): Mission | undefined {
+    const typePart = missionId.replace(/^endgame_/, '').replace(/_\d+(_review)?$/, '');
+    const found = ENDGAME_MISSIONS.find(m => m.objectiveType === typePart || missionId.startsWith(`endgame_${m.objectiveType}`));
+    if (found) {
+        return { ...found, id: missionId } as Mission;
+    }
+    return undefined;
+}
+
 export function checkDailyAndWeeklyReset(data: UserGamification): UserGamification | null {
     const today = new Date();
     const todayStr = getLocalDateStr(today);
@@ -169,16 +182,11 @@ export function claimMissionRewardLogic(
 
     const daily = generateDailyMissions(today);
     const weekly = generateWeeklyMissions(today);
-    const allMissions = [...daily, ...weekly, ...ENDGAME_MISSIONS];
-    // For endgame missions, the ID might be constructed (e.g. endgame_speedrun_0)
-    // We need to find the definition either by exact match or by prefix for static endgame definitions
-    // Note: ENDGAME_MISSIONS do not have 'id' property in definitions, so we cast to any or handle specifically
-    let missionDef = allMissions.find(m => 'id' in m && m.id === missionId);
+    const allMissions = [...daily, ...weekly];
+    let missionDef = allMissions.find(m => m.id === missionId);
 
-    // If not found, try to find in ENDGAME_MISSIONS by title matching (since we construct IDs dynamically)
     if (!missionDef) {
-        // Find endgame mission definition by checking if the missionId (from user state) matches the constructed pattern
-        missionDef = ENDGAME_MISSIONS.find(m => missionId.startsWith(`endgame_${m.objectiveType}`)) as Mission;
+        missionDef = getEndgameMissionDef(missionId);
     }
 
     if (!missionDef) {
@@ -232,17 +240,15 @@ export function updateMissionProgress(
     const today = new Date();
     const daily = generateDailyMissions(today);
     const weekly = generateWeeklyMissions(today);
-    // Include Endgame missions for lookup
-    const allMissions = [...daily, ...weekly, ...ENDGAME_MISSIONS];
+    const allMissions = [...daily, ...weekly];
 
     const newActiveMissions = state.activeMissions.map(userMission => {
         if (userMission.status !== 'active') return userMission;
 
-        // Smart Lookup (duplicate logic from claimMissionRewardLogic)
-        let missionDef = allMissions.find(m => 'id' in m && m.id === userMission.missionId);
+        let missionDef = allMissions.find(m => m.id === userMission.missionId);
 
         if (!missionDef) {
-            missionDef = ENDGAME_MISSIONS.find(m => userMission.missionId.startsWith(`endgame_${m.objectiveType}`)) as Mission;
+            missionDef = getEndgameMissionDef(userMission.missionId);
         }
         if (!missionDef) return userMission;
 
@@ -399,17 +405,11 @@ export function hydrateMissions(activeMissions: UserGamification['activeMissions
                 if (found) weekly.push(isReview ? processHydration(found, um.missionId) : found);
             }
         } else if (baseId.startsWith('endgame_')) {
-            // Handle endgame hydration if needed (already static basically)
-            // But we need to match the specific endgame mission
-            // const typePart = baseId.split('_')[1];
-            const found = ENDGAME_MISSIONS.find(m => baseId.startsWith(`endgame_${m.objectiveType}`));
+            const found = getEndgameMissionDef(baseId);
             if (found) {
-                const hydrated = { ...found, id: um.missionId } as Mission; // Cast needed as ENDGAME lacks ID
-                daily.push(hydrated); // Endgame usually shown in daily or separate list? The UI splits daily/weekly.
-                // Ideally endgame is its own category. But for now put in Daily or Weekly based on... choice.
-                // Actually the UI currently only shows Daily/Weekly props.
-                // We might need to add 'endgame' prop to UI later.
-                // For now, let's just push to daily to ensure visibility.
+                // Ensure the final ID matches exactly the one in the user state (e.g. including _review)
+                const hydrated = { ...found, id: um.missionId };
+                daily.push(isReview ? processHydration(hydrated, um.missionId) : hydrated);
             }
         }
     });
diff --git a/src/utils/gamification/questionLogic.ts b/src/utils/gamification/questionLogic.ts
index 319933d..5518f6d 100644
--- a/src/utils/gamification/questionLogic.ts
+++ b/src/utils/gamification/questionLogic.ts
@@ -1,6 +1,7 @@
-import type { UserGamification, LevelInfo, Mission } from '../../types/gamification';
-import { getLevelFromXP, ENDGAME_MISSIONS, generateDailyMissions, generateWeeklyMissions } from '../../data/gamificationData';
+import type { UserGamification, LevelInfo } from '../../types/gamification';
+import { getLevelFromXP, generateDailyMissions, generateWeeklyMissions } from '../../data/gamificationData';
 import { calculateStreak } from '../gamificationUtils';
+import { getEndgameMissionDef } from './missionLogic';
 import { getInitialPet, gainPetXp } from '../petLogic';
 
 export function recordQuestionLogic(
@@ -114,11 +115,7 @@ export function recordQuestionLogic(
         let def = [...daily, ...weekly].find(m => m.id === mission.missionId);
 
         if (!def && mission.missionId.startsWith('endgame_')) {
-            const typePart = mission.missionId.split('_')[1];
-            const found = ENDGAME_MISSIONS.find(m => m.objectiveType === typePart || (typePart === 'improve' && m.objectiveType === 'improve_stars') || (typePart === 'syntax' && m.objectiveType === 'syntax_master'));
-            if (found) {
-                def = { ...found, id: mission.missionId } as Mission;
-            }
+            def = getEndgameMissionDef(mission.missionId);
         }
 
         if (!def) return mission;