diff --git a/docs/development/CENTRAL.md b/docs/development/CENTRAL.md
index aa2da36..cbf1b6e 100644
--- a/docs/development/CENTRAL.md
+++ b/docs/development/CENTRAL.md
@@ -140,3 +140,4 @@
 - [Strict Cache Structure](./devlog/2025-12-18-213300_strict_cache_structure.md): Completed. Enforced cache structure `/cards/[code]/full` and `/cards/[code]/crop`, removing the `images` subdirectory and ensuring strict local file usage.
 - [Implicit Image Caching](./devlog/2025-12-18-213900_implicit_image_caching.md): Completed. Updated API routes `/api/sets/:code/cards` and `/api/cards/parse` to implicitly trigger and await image caching, ensuring assets are available immediately for generators.
 - [Restore Images Subdirectory](./devlog/2025-12-18-214300_restore_images_subdir.md): Completed. Corrected cache folder structure to `/cards/images/[set]/full` and `/cards/images/[set]/crop` as per user request.
+- [Fix Build Unused Variables](./devlog/2025-12-19-011500_fix_build_unused_vars.md): Completed. Resolved TS6133 errors in RulesEngine, PersistenceManager, and CardService to fix Docker build failure.
diff --git a/docs/development/devlog/2025-12-19-011500_fix_build_unused_vars.md b/docs/development/devlog/2025-12-19-011500_fix_build_unused_vars.md
new file mode 100644
index 0000000..36d0653
--- /dev/null
+++ b/docs/development/devlog/2025-12-19-011500_fix_build_unused_vars.md
@@ -0,0 +1,24 @@
+# Fix Build Unused Variables
+
+## Objective
+Fix Typescript errors preventing `npm run build` execution in the Docker container.
+The errors were `TS6133` (unused variables) in:
+- `server/game/RulesEngine.ts`
+- `server/managers/PersistenceManager.ts`
+- `server/services/CardService.ts`
+
+## Changes
+1. **RulesEngine.ts**:
+   - Removed unused imports: `PlayerState`, `StackObject`.
+   - Renamed unused parameter `playerId` to `_playerId` in `cleanupStep`.
+   - (Also fixed an accidental comment injection during the process).
+
+2. **PersistenceManager.ts**:
+   - Removed unused `__dirname` and `__filename` definitions.
+   - Removed unused `fileURLToPath` import.
+
+3. **CardService.ts**:
+   - Removed unused `fs` import.
+
+## Verification
+- Ran `npx tsc --noEmit` in `src` directory. Result: Exit code 0 (Success).
diff --git a/src/client/dev-dist/sw.js b/src/client/dev-dist/sw.js
index 4c4fa65..8961311 100644
--- a/src/client/dev-dist/sw.js
+++ b/src/client/dev-dist/sw.js
@@ -82,7 +82,7 @@ define(['./workbox-5a5d9309'], (function (workbox) { 'use strict';
     "revision": "3ca0b8505b4bec776b69afdba2768812"
   }, {
     "url": "index.html",
-    "revision": "0.56865l1cj5s"
+    "revision": "0.l4u3i9b5p1c"
   }], {});
   workbox.cleanupOutdatedCaches();
   workbox.registerRoute(new workbox.NavigationRoute(workbox.createHandlerBoundToURL("index.html"), {
diff --git a/src/server/game/RulesEngine.ts b/src/server/game/RulesEngine.ts
index 9381426..405ba35 100644
--- a/src/server/game/RulesEngine.ts
+++ b/src/server/game/RulesEngine.ts
@@ -1,5 +1,5 @@
 
-import { StrictGameState, PlayerState, Phase, Step, StackObject } from './types';
+import { StrictGameState, Phase, Step } from './types';
 
 export class RulesEngine {
   public state: StrictGameState;
@@ -561,7 +561,7 @@ export class RulesEngine {
     }
   }
 
-  private cleanupStep(playerId: string) {
+  private cleanupStep(_playerId: string) {
     // Remove damage, discard down to 7
     console.log(`Cleanup execution.`);
     Object.values(this.state.cards).forEach(c => {
diff --git a/src/server/managers/PersistenceManager.ts b/src/server/managers/PersistenceManager.ts
index d5e9715..53164a7 100644
--- a/src/server/managers/PersistenceManager.ts
+++ b/src/server/managers/PersistenceManager.ts
@@ -4,12 +4,10 @@ import path from 'path';
 import { RoomManager } from './RoomManager';
 import { DraftManager } from './DraftManager';
 import { GameManager } from './GameManager';
-import { fileURLToPath } from 'url';
+
 import { RedisClientManager } from './RedisClientManager';
 
-// Handling __dirname in ESM
-const __filename = fileURLToPath(import.meta.url);
-const __dirname = path.dirname(__filename);
+
 
 // Store data in src/server/data so it persists (assuming not inside a dist that gets wiped, but user root)
 const DATA_DIR = path.resolve(process.cwd(), 'server-data');
diff --git a/src/server/services/CardService.ts b/src/server/services/CardService.ts
index 89eaa45..cc09194 100644
--- a/src/server/services/CardService.ts
+++ b/src/server/services/CardService.ts
@@ -1,5 +1,5 @@
 
-import fs from 'fs';
+
 import path from 'path';
 import { fileURLToPath } from 'url';
 import { fileStorageManager } from '../managers/FileStorageManager';