diff --git a/src/components/battle-calc/battle-calc-view.ts b/src/components/battle-calc/battle-calc-view.ts
index 8e50da1..3311b43 100644
--- a/src/components/battle-calc/battle-calc-view.ts
+++ b/src/components/battle-calc/battle-calc-view.ts
@@ -146,7 +146,9 @@ export class BattleCalcView implements TW2WindowView<WestCalcWindowTab>, Compone
 
     getMainDiv(): JQuery {
         if (!this.battleCalc.isAvailable()) {
-            return $('<div>Battle calc core script is not loaded, try refreshing the game.</div>');
+            // kick off a (re)load in the background so reopening this window recovers it
+            this.battleCalc.load();
+            return $('<div>Battle calc core script is not loaded yet, reopen this window in a few seconds.</div>');
         }
 
         const { west } = this.window;
diff --git a/src/components/battle-calc/battle-calc.spec.ts b/src/components/battle-calc/battle-calc.spec.ts
new file mode 100644
index 0000000..35dc26c
--- /dev/null
+++ b/src/components/battle-calc/battle-calc.spec.ts
@@ -0,0 +1,116 @@
+import { BattleCalc } from './battle-calc';
+import { BattleCalcWindow, BattleCoreCalc } from './battle-calc.types';
+import { Config } from '../config/config';
+import { ErrorTracker } from '../error-tracker/error-tracker';
+import { Logger } from '../logger/logger';
+import { Mock } from 'ts-mocks';
+
+type Behavior = 'done' | 'fail' | 'pending';
+
+/**
+ * Minimal stand-in for the jqXHR returned by `$.getScript`, with controllable
+ * resolution so we can drive the success / failure / in-flight branches.
+ */
+function fakeJqXHR(behavior: Behavior): unknown {
+    const xhr = {
+        done(cb: () => void) {
+            if (behavior === 'done') {
+                cb();
+            }
+            return xhr;
+        },
+        fail(cb: () => void) {
+            if (behavior === 'fail') {
+                cb();
+            }
+            return xhr;
+        },
+    };
+    return xhr;
+}
+
+describe('BattleCalc', () => {
+    const website = 'https://tw-calc.net';
+    const coreScriptUrl = website + '/js/battle-calculator-core.js';
+
+    let battleCalc: BattleCalc;
+    let loggerMock: Mock<Logger>;
+    let getScript: jasmine.Spy;
+    let setTimeoutSpy: jasmine.Spy;
+    let win: BattleCalcWindow & { BattleCalc?: BattleCoreCalc };
+
+    function build(behavior: Behavior): void {
+        getScript = jasmine.createSpy('getScript').and.callFake(() => fakeJqXHR(behavior));
+        // run scheduled retries synchronously so the whole chain resolves in the test
+        setTimeoutSpy = jasmine.createSpy('setTimeout').and.callFake((cb: () => void) => {
+            cb();
+            return 0;
+        });
+        loggerMock = new Mock<Logger>({ error: Mock.ANY_FUNC });
+
+        win = {
+            $: { getScript } as unknown as BattleCalcWindow['$'],
+            setTimeout: setTimeoutSpy as unknown as Window['setTimeout'],
+        } as BattleCalcWindow;
+
+        battleCalc = new BattleCalc(
+            win,
+            new Mock<Config>({ website }).Object,
+            loggerMock.Object,
+            new Mock<ErrorTracker>({ track: Mock.ANY_FUNC }).Object,
+        );
+    }
+
+    it('loads the battle calc core script on init', () => {
+        build('done');
+
+        battleCalc.init();
+
+        expect(getScript).toHaveBeenCalledTimes(1);
+        expect(getScript).toHaveBeenCalledWith(coreScriptUrl);
+    });
+
+    it('retries up to 3 times and logs each failure', () => {
+        build('fail');
+
+        battleCalc.init();
+
+        expect(getScript).toHaveBeenCalledTimes(3);
+        expect(loggerMock.Object.error).toHaveBeenCalledTimes(3);
+        // backoff is only scheduled between attempts, not after the final one
+        expect(setTimeoutSpy).toHaveBeenCalledTimes(2);
+    });
+
+    it('does not start a second load while one is already in progress', () => {
+        build('pending');
+
+        battleCalc.load();
+        battleCalc.load();
+
+        expect(getScript).toHaveBeenCalledTimes(1);
+    });
+
+    it('does not load when the core is already available', () => {
+        build('done');
+        win.BattleCalc = { coreCalc: () => ({}) } as unknown as BattleCoreCalc;
+
+        battleCalc.load();
+
+        expect(getScript).not.toHaveBeenCalled();
+    });
+
+    it('getInstance throws when the core is not loaded', () => {
+        build('pending');
+
+        expect(() => battleCalc.getInstance()).toThrowError('Battle calc core is not loaded yet!');
+    });
+
+    it('getInstance returns the core once available', () => {
+        build('done');
+        const core = { coreCalc: () => ({}) } as unknown as BattleCoreCalc;
+        win.BattleCalc = core;
+
+        expect(battleCalc.isAvailable()).toBe(true);
+        expect(battleCalc.getInstance()).toBe(core);
+    });
+});
diff --git a/src/components/battle-calc/battle-calc.ts b/src/components/battle-calc/battle-calc.ts
index fcc072b..9ccab6b 100644
--- a/src/components/battle-calc/battle-calc.ts
+++ b/src/components/battle-calc/battle-calc.ts
@@ -4,19 +4,39 @@ import { Component } from '../component.types';
 import { Config } from '../config/config';
 import { ErrorTracker } from '../error-tracker/error-tracker';
 import { inject, singleton } from 'tsyringe';
+import { Logger } from '../logger/logger';
 import { MarkRequired } from 'ts-essentials';
 
+const MAX_LOAD_ATTEMPTS = 3;
+
 @singleton()
 export class BattleCalc implements Component {
+    private loading = false;
+
     constructor(
         @inject('window') private window: BattleCalcWindow,
         private config: Config,
+        private readonly logger: Logger,
         public readonly errorTracker: ErrorTracker,
     ) {}
 
     @CatchErrors('BattleCalc.init')
     init(): void {
-        this.window.$.getScript(this.config.website + '/js/battle-calculator-core.js');
+        this.load();
+    }
+
+    /**
+     * Loads the battle calc core script from the server. A single failed or cancelled
+     * request used to leave the calc unavailable for the whole session, so failures are
+     * retried with a backoff. Safe to call again (e.g. when a view finds it unavailable):
+     * it is a no-op while already loaded or loading.
+     */
+    load(): void {
+        if (this.isAvailable() || this.loading) {
+            return;
+        }
+        this.loading = true;
+        this.attemptLoad(1);
     }
 
     isAvailable(): boolean {
@@ -30,6 +50,21 @@ export class BattleCalc implements Component {
         }
         return window['BattleCalc'];
     }
+
+    private attemptLoad(attempt: number): void {
+        this.window.$.getScript(this.config.website + '/js/battle-calculator-core.js')
+            .done(() => {
+                this.loading = false;
+            })
+            .fail(() => {
+                this.logger.error(`failed to load battle calc core (attempt ${attempt}/${MAX_LOAD_ATTEMPTS})`);
+                if (attempt < MAX_LOAD_ATTEMPTS) {
+                    this.window.setTimeout(() => this.attemptLoad(attempt + 1), attempt * 2000);
+                } else {
+                    this.loading = false;
+                }
+            });
+    }
 }
 
 function isAvailable(window: BattleCalcWindow): window is MarkRequired<BattleCalcWindow, 'BattleCalc'> {
diff --git a/src/components/battle-calc/character-view.ts b/src/components/battle-calc/character-view.ts
index ad0e6be..4eaa261 100644
--- a/src/components/battle-calc/character-view.ts
+++ b/src/components/battle-calc/character-view.ts
@@ -68,7 +68,9 @@ export class CharacterView implements TW2WindowView<WestCalcWindowTab> {
 
     getMainDiv(): JQuery {
         if (!this.battleCalc.isAvailable()) {
-            return $('<div>Battle calc core script is not loaded, try refreshing the game.</div>');
+            // kick off a (re)load in the background so reopening this window recovers it
+            this.battleCalc.load();
+            return $('<div>Battle calc core script is not loaded yet, reopen this window in a few seconds.</div>');
         }
 
         const html = $('<div id="BattleCalcCharacterView"></div>');
diff --git a/src/components/chests/chests.spec.ts b/src/components/chests/chests.spec.ts
new file mode 100644
index 0000000..3582724
--- /dev/null
+++ b/src/components/chests/chests.spec.ts
@@ -0,0 +1,74 @@
+import { Chests } from './chests';
+import { Config } from '../config/config';
+import { ErrorTracker } from '../error-tracker/error-tracker';
+import { Logger } from '../logger/logger';
+import { Mock } from 'ts-mocks';
+import { TheWestWindow } from '../../@types/the-west';
+
+/**
+ * Builds a stand-in for the game's `ItemUse.doIt` whose `toString()` returns a
+ * controlled source, so we can exercise the string-rewriting patch with both
+ * quote styles without depending on how the test bundler emits a real function.
+ */
+function doItWithSource(source: string): () => void {
+    const fn = function () {} as unknown as { toString: () => string };
+    fn.toString = () => source;
+    return fn as unknown as () => void;
+}
+
+describe('Chests', () => {
+    let chests: Chests;
+    let loggerMock: Mock<Logger>;
+    let errorTrackerMock: Mock<ErrorTracker>;
+    let itemUse: { doIt: () => void; doItOrigin?: () => void };
+
+    function setup(source: string): void {
+        itemUse = { doIt: doItWithSource(source) };
+        // eval() inside init() resolves the bare `ItemUse` identifier from the
+        // global scope, so the injected window and the global must share the object.
+        (window as unknown as { ItemUse: typeof itemUse }).ItemUse = itemUse;
+
+        loggerMock = new Mock<Logger>({ log: Mock.ANY_FUNC, error: Mock.ANY_FUNC });
+        errorTrackerMock = new Mock<ErrorTracker>({ track: Mock.ANY_FUNC });
+
+        const windowStub = { ItemUse: itemUse } as unknown as TheWestWindow;
+        chests = new Chests(windowStub, loggerMock.Object, new Mock<Config>().Object, errorTrackerMock.Object);
+    }
+
+    afterEach(() => {
+        delete (window as unknown as { ItemUse?: unknown }).ItemUse;
+    });
+
+    it('patches the chest handler when the item_used anchor uses single quotes', () => {
+        setup("function (itemId, itemCount) { EventHandler.signal('item_used', [itemId]); }");
+
+        chests.init();
+
+        const patched = itemUse.doIt.toString();
+        expect(patched).toContain('TW_Calc.trackChest(itemId,res);');
+        expect(patched.indexOf('TW_Calc.trackChest')).toBeLessThan(patched.indexOf('EventHandler.signal'));
+        expect(errorTrackerMock.Object.track).not.toHaveBeenCalled();
+    });
+
+    it('patches the chest handler when the item_used anchor uses double quotes', () => {
+        setup('function (itemId, itemCount) { EventHandler.signal("item_used", [itemId]); }');
+
+        chests.init();
+
+        const patched = itemUse.doIt.toString();
+        expect(patched).toContain('TW_Calc.trackChest(itemId,res);');
+        expect(errorTrackerMock.Object.track).not.toHaveBeenCalled();
+    });
+
+    it('tracks an error and leaves the handler untouched when the anchor is missing', () => {
+        setup("function (itemId, itemCount) { EventHandler.signal('something_else', [itemId]); }");
+        const original = itemUse.doIt;
+
+        chests.init();
+
+        // no broken eval, no rewrite — the original handler is preserved
+        expect(itemUse.doIt).toBe(original);
+        expect(itemUse.doIt.toString()).not.toContain('TW_Calc.trackChest');
+        expect(errorTrackerMock.Object.track).toHaveBeenCalled();
+    });
+});
diff --git a/src/components/chests/chests.ts b/src/components/chests/chests.ts
index fb9d3e6..366561e 100644
--- a/src/components/chests/chests.ts
+++ b/src/components/chests/chests.ts
@@ -26,7 +26,13 @@ export class Chests implements Component {
         let newStr: string | undefined;
         try {
             const str = originalFn.toString();
-            const pos = str.indexOf("EventHandler.signal('item_used'");
+            // quote-agnostic anchor: some minified builds emit the signal with double quotes
+            const match = str.match(/EventHandler\.signal\(['"]item_used['"]/);
+            if (!match || match.index === undefined) {
+                // fail loudly & harmlessly instead of building broken code from a -1 position
+                throw new Error('item_used anchor not found in ItemUse.doIt');
+            }
+            const pos = match.index;
             const body = str.substr(0, pos) + 'TW_Calc.trackChest(itemId,res);' + str.substr(pos);
             this.logger.log('patching the chest handler...', body);
             newStr = 'ItemUse.doIt = ' + body;