chore(devops): move lint coverage to oxlint

.oxlintrc.json

@@ -6,10 +6,12 @@
   },
   "ignorePatterns": [
     "src/server/gatekeeper/**",
-    "tests/pathfinding/playground/**"
+    "tests/pathfinding/playground/**",
+    ".claude/**"
   ],
+  "plugins": ["eslint", "typescript", "oxc", "import"],
   "categories": {
-    "correctness": "off",
+    "correctness": "error",
     "suspicious": "off",
     "pedantic": "off",
     "perf": "off",
@@ -22,9 +24,19 @@
   },
   "rules": {
     "typescript/no-explicit-any": "off",
+    "typescript/no-floating-promises": "off",
+    "typescript/restrict-template-expressions": "off",
+    "typescript/unbound-method": "off",
+    "typescript/no-base-to-string": "off",
+    "typescript/no-misused-spread": "off",
+    "typescript/require-array-sort-compare": "off",
+    "typescript/no-redundant-type-constituents": "off",
+    "typescript/await-thenable": "off",
+    "typescript/no-useless-default-assignment": "off",
     "typescript/prefer-nullish-coalescing": "error",
     "eqeqeq": "error",
     "no-case-declarations": "error",
+    "import/no-duplicates": "error",
     "no-unused-vars": [
       "error",
       {
@@ -36,5 +48,123 @@
         }
       }
     ]
-  }
+  },
+  "jsPlugins": [{ "name": "eslint-js", "specifier": "oxlint-plugin-eslint" }],
+  "overrides": [
+    {
+      "files": [
+        "packages/engine/src/**/*.ts",
+        "packages/engine-api/src/**/*.ts",
+        "packages/engine-lib/src/**/*.ts"
+      ],
+      "excludeFiles": ["packages/engine-lib/src/DetMath.ts"],
+      "rules": {
+        "eslint/no-restricted-properties": [
+          "error",
+          {
+            "object": "Math",
+            "property": "exp",
+            "message": "Math.exp differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "expm1",
+            "message": "Math.expm1 differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "log",
+            "message": "Math.log differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "log1p",
+            "message": "Math.log1p differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "log2",
+            "message": "Math.log2 differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "log10",
+            "message": "Math.log10 differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "pow",
+            "message": "Math.pow differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "sin",
+            "message": "Math.sin differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "cos",
+            "message": "Math.cos differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "tan",
+            "message": "Math.tan differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "asin",
+            "message": "Math.asin differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "acos",
+            "message": "Math.acos differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "atan",
+            "message": "Math.atan differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "atan2",
+            "message": "Math.atan2 differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "sinh",
+            "message": "Math.sinh differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "cosh",
+            "message": "Math.cosh differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "tanh",
+            "message": "Math.tanh differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "cbrt",
+            "message": "Math.cbrt differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          },
+          {
+            "object": "Math",
+            "property": "hypot",
+            "message": "Math.hypot differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          }
+        ],
+        "eslint-js/no-restricted-syntax": [
+          "error",
+          {
+            "selector": "BinaryExpression[operator='**']:not([right.type='Literal'][right.value=2])",
+            "message": "`**` with a non-2 exponent differs between JS engines; use packages/engine-lib/src/DetMath.ts to keep the simulation deterministic."
+          }
+        ]
+      }
+    }
+  ]
 }

src/client/HostLobbyModal.ts

@@ -36,6 +36,8 @@ import { CopyButton } from "./components/CopyButton";
 import "./components/GameConfigSettings";
 import "./components/InputCard";
 import "./components/InsufficientCurrencyDialog";
+// The type import below is erased at runtime; keep this to register the dialog.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
 import "./components/ListLobbyDialog";
 import { ListLobbyOptions } from "./components/ListLobbyDialog";
 import "./components/LobbyPlayerView";

src/client/InGameModal.ts

@@ -1,3 +1,5 @@
+// The type-only use below is erased at runtime; keep this to register the dialog.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
 import "./components/ConfirmDialog";
 import { ConfirmDialog } from "./components/ConfirmDialog";
 import { gamePortal } from "./GamePortal";

src/client/LangSelector.ts

@@ -2,6 +2,8 @@ import { assetUrl } from "@openfront/shared/AssetUrls";
 import { LitElement, html } from "lit";
 import { customElement, state } from "lit/decorators.js";
 import { desktopSteamLocale } from "./DesktopShell";
+// The type-only use below is erased at runtime; keep this to register the modal.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
 import "./LanguageModal";
 import { LanguageModal } from "./LanguageModal";
 import { formatDebugTranslation } from "./Utils";

src/client/Main.ts

@@ -67,7 +67,6 @@ import {
 } from "./DesktopShell";
 import "./FeaturedStream";
 import { loadGameClient, prefetchGameClient } from "./GameClientLoader";
-import "./GameModeSelector";
 import {
   GameModeSelector,
   joinIsGateable,
@@ -83,6 +82,8 @@ import type { HomepagePromos } from "./HomepagePromos";
 import type { HostLobbyModal as HostPrivateLobbyModal } from "./HostLobbyModal";
 import { showInGameAlert, showInGameConfirm } from "./InGameModal";
 import type { JoinLobbyModal } from "./JoinLobbyModal";
+// The LangSelector class is used as a type; retain this for registration.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
 import "./LangSelector";
 import { LangSelector } from "./LangSelector";
 import { initLayout } from "./Layout";
@@ -152,8 +153,10 @@ import {
 // Before the first userMeResponse, for the modals that load after it.
 import "./UserMeBroadcast";
 import { classicReplayHref } from "./replay/ReplayEntry";
-import "./UsernameInput";
 import { parseReplayViewerHash } from "./replay/ReplayViewerRoute";
+// The UsernameInput class is used as a type; retain this for registration.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
+import "./UsernameInput";
 import { UsernameInput } from "./UsernameInput";
 import { UserSettings } from "./UserSettings";
 import "./components/BannedModal";

src/client/SinglePlayerModal.ts

@@ -22,7 +22,6 @@ import "./components/baseComponents/Button";
 import "./components/baseComponents/Modal";
 import { BaseModal } from "./components/BaseModal";
 import "./components/GameConfigSettings";
-import "./components/SavedGamesPanel";
 import { MEDAL_ORDER, medalIcon } from "./components/map/Medals";
 import {
   type LoadSavedGameDetail,

src/client/Store.ts

@@ -23,7 +23,6 @@ import type { InlineCheckout } from "./components/InlineCheckout";
 import "./components/NotLoggedInWarning";
 import "./components/PackContentsDialog";
 import { ProgressiveList } from "./components/ProgressiveList";
-import "./components/PurchaseButton";
 import { alignPurchaseRows } from "./components/PurchaseButton";
 import "./components/TribesPanel";
 import { modalHeader } from "./components/ui/ModalHeader";

src/client/UserSettingModal.ts

@@ -2,9 +2,13 @@ import type { MapLayer } from "@openfront/engine-api/game/MapFiles";
 import { html, nothing } from "lit";
 import { customElement, state } from "lit/decorators.js";
 import { formatKeyForDisplay, translateText } from "../client/Utils";
+// This type is erased at runtime; retain the import to register the setting.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
 import "./components/baseComponents/setting/SettingKeybind";
 import { SettingKeybind } from "./components/baseComponents/setting/SettingKeybind";
 import "./components/baseComponents/setting/SettingNumber";
+// This type is erased at runtime; retain the import to register the setting.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
 import "./components/baseComponents/setting/SettingSelect";
 import { SettingSelect } from "./components/baseComponents/setting/SettingSelect";
 import "./components/baseComponents/setting/SettingSlider";

src/client/components/NavAccountMenu.ts

@@ -26,7 +26,6 @@ import {
 import { steamSDK } from "../SteamSDK";
 import { playerProfileUrl } from "../utilities/PlayerProfileUrl";
 import { copyToClipboard, showToast, translateText } from "../Utils";
-import "./LevelBadge";
 import { levelBadgeLabel } from "./LevelBadge";
 import { xpBar, xpProgressText } from "./XpBar";
 

src/client/components/ProfileCard.ts

@@ -11,7 +11,6 @@ import { customElement, property, state } from "lit/decorators.js";
 import { clampPrestige, levelFraction } from "../Progression";
 import { prefersReducedMotion } from "../utilities/ReducedMotion";
 import { translateText } from "../Utils";
-import "./LevelBadge";
 import { levelBadgeAccent } from "./LevelBadge";
 import { splitAccountUsername, usernameText } from "./ui/UsernameText";
 import { formatXp, xpProgressText } from "./XpBar";

src/client/replay/ReplayViewer.ts

@@ -22,7 +22,6 @@ import "../hud/layers/PlayerInfoOverlay";
 import type { PlayerInfoOverlay } from "../hud/layers/PlayerInfoOverlay";
 import "../hud/layers/PlayerStats";
 import type { PlayerStats } from "../hud/layers/PlayerStats";
-import "../hud/layers/SettingsModal";
 import {
   ShowSettingsModalEvent,
   type SettingsModal,

tests/ColumnPicker.test.ts

@@ -33,10 +33,10 @@ describe("ColumnPicker", () => {
       selection = (event as CustomEvent<ColumnId[]>).detail;
     });
     // Registry order: index 0 is clan, 1 is playerType, 2 is tiles, 3 is gold.
-    (popup?.querySelectorAll("input")[3] as HTMLInputElement).click();
+    (popup!.querySelectorAll("input")[3] as HTMLInputElement).click();
     expect(selection).toEqual(["tiles", "gold"]);
 
-    (popup?.querySelectorAll("input")[0] as HTMLInputElement).click();
+    (popup!.querySelectorAll("input")[0] as HTMLInputElement).click();
     expect(selection).toEqual(["clan", "tiles"]);
 
     sidebar.remove();

tests/DesktopStatusBar.test.ts

@@ -1,7 +1,6 @@
 // @vitest-environment jsdom
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { ClientEnv } from "../src/client/ClientEnv";
-import "../src/client/components/DesktopStatusBar";
 import { barSource } from "../src/client/components/DesktopStatusBar";
 import {
   backendUnreachableConfirmed,

tests/ReachabilityGating.test.ts

@@ -7,6 +7,7 @@ import type {
 } from "@openfront/shared/WireSchemas";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { ClientEnv } from "../src/client/ClientEnv";
+// This named import also registers <game-mode-selector> as a side effect.
 import { shouldBlockMultiplayerAction } from "../src/client/GameModeSelector";
 import {
   attemptInFlight,
@@ -42,9 +43,6 @@ vi.mock("../src/client/LazyModals", async (importOriginal) => ({
   whenModalLoaded: (_tag: string, open: () => void) => open(),
 }));
 
-// Registers <game-mode-selector> as a side effect.
-import "../src/client/GameModeSelector";
-
 /**
  * OPE-439. The server-list heartbeat already knows whether the API answers;
  * this is the half that turns that into something the player can see, on the

tests/client/EffectsGrid.test.ts

@@ -300,7 +300,7 @@ describe("EffectsGrid", () => {
       await card.updateComplete;
       card.querySelector<HTMLButtonElement>("[data-cosmetic-main]")!.click();
 
-      expect((onMessage.mock.lastCall?.[0] as CustomEvent).detail.message).toBe(
+      expect((onMessage.mock.lastCall![0] as CustomEvent).detail.message).toBe(
         "Selected Localized Wake",
       );
 

tests/client/InventoryModal.test.ts

@@ -525,7 +525,7 @@ describe("InventoryModal", () => {
   it("announces flag, crown and skin selections too", async () => {
     const onMessage = vi.fn();
     const lastMessage = () =>
-      (onMessage.mock.lastCall?.[0] as CustomEvent).detail.message;
+      (onMessage.mock.lastCall![0] as CustomEvent).detail.message;
     window.addEventListener("show-message", onMessage);
     try {
       await showTab(modal, "skins");

tests/client/ListLobbyDialog.test.ts

@@ -3,6 +3,8 @@ import {
   MIN_HOSTED_LOBBY_PLAYERS,
 } from "@openfront/shared/WireSchemas";
 import { describe, expect, it } from "vitest";
+// The class is used as a type below, so this import is needed for registration.
+// oxlint-disable-next-line import/no-duplicates -- Required custom-element registration.
 import "../../src/client/components/ListLobbyDialog";
 import { ListLobbyDialog } from "../../src/client/components/ListLobbyDialog";
 

tests/client/NewsModal.test.ts

@@ -1,7 +1,6 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
-// Side-effect import registers <news-modal>; a type-only import would be
-// elided and leave the element inert.
-import "../../src/client/NewsModal";
+// The named import registers <news-modal> as a side effect; a type-only import
+// would be elided and leave the element inert.
 import { NewsModal } from "../../src/client/NewsModal";
 
 beforeEach(() => {

tests/client/clan/ClanModal.rendering.test.ts

@@ -553,12 +553,12 @@ describe("ClanModal — rendering", () => {
     it("uses the compact card variant, not the header size", async () => {
       const card = await showMyClan(makeClan({ hardBalance: "25" }));
       const cardSize = (
-        card?.querySelector("plutonium-icon") as HTMLElement & { size: number }
+        card!.querySelector("plutonium-icon") as HTMLElement & { size: number }
       ).size;
 
       const header = await openDetail(makeClan({ hardBalance: "25" }));
       const headerSize = (
-        header?.querySelector("plutonium-icon") as HTMLElement & {
+        header!.querySelector("plutonium-icon") as HTMLElement & {
           size: number;
         }
       ).size;

tests/client/graphics/layers/ChatModalShortcut.test.ts

@@ -1,6 +1,5 @@
 import { EventBus } from "@openfront/shared/EventBus";
 import { beforeEach, describe, expect, it, vi } from "vitest";
-import "../../../../src/client/hud/layers/ChatModal";
 import {
   ShowPlayerChatEvent,
   type ChatModal,

tests/client/graphics/layers/EmojiTable.test.ts

@@ -2,7 +2,6 @@ import { AllPlayers } from "@openfront/engine-api/game/GameTypes";
 import { flattenedEmojiTable } from "@openfront/engine-api/Schemas";
 import { EventBus } from "@openfront/shared/EventBus";
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
-import "../../../../src/client/hud/layers/EmojiTable";
 import {
   type EmojiTable,
   ShowPlayerEmojiMenuEvent,

tests/client/graphics/layers/SpawnTimer.test.ts

@@ -1,9 +1,8 @@
 import { GameMode, GameType } from "@openfront/engine-api/game/GameTypes";
 import { EventBus } from "@openfront/shared/EventBus";
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
-import "../../../../src/client/hud/layers/SpawnTimer";
-import type { SpawnTimer } from "../../../../src/client/hud/layers/SpawnTimer";
 import { SpawnBarVisibleEvent } from "../../../../src/client/hud/layers/SpawnTimer";
+import type { SpawnTimer } from "../../../../src/client/hud/layers/SpawnTimer";
 import type { GameView } from "../../../../src/client/view";
 
 function makePlayer(team: string | null, tiles: number) {