test: stabilize bun coverage reporting

src/anki-integration/known-word-cache.test.ts

@@ -85,13 +85,15 @@ test('KnownWordCacheManager startLifecycle keeps fresh persisted cache without i
     },
   };
   const { manager, calls, statePath, cleanup } = createKnownWordCacheHarness(config);
+  const originalDateNow = Date.now;
 
   try {
+    Date.now = () => 120_000;
     fs.writeFileSync(
       statePath,
       JSON.stringify({
         version: 2,
-        refreshedAtMs: Date.now(),
+        refreshedAtMs: 120_000,
         scope: '{"refreshMinutes":60,"scope":"is:note","fieldsWord":""}',
         words: ['猫'],
         notes: {
@@ -102,12 +104,20 @@ test('KnownWordCacheManager startLifecycle keeps fresh persisted cache without i
     );
 
     manager.startLifecycle();
-    await new Promise((resolve) => setTimeout(resolve, 25));
 
     assert.equal(manager.isKnownWord('猫'), true);
     assert.equal(calls.findNotes, 0);
     assert.equal(calls.notesInfo, 0);
+    assert.equal(
+      (
+        manager as unknown as {
+          getMsUntilNextRefresh: () => number;
+        }
+      ).getMsUntilNextRefresh() > 0,
+      true,
+    );
   } finally {
+    Date.now = originalDateNow;
     manager.stopLifecycle();
     cleanup();
   }
@@ -124,13 +134,15 @@ test('KnownWordCacheManager startLifecycle immediately refreshes stale persisted
     },
   };
   const { manager, calls, statePath, clientState, cleanup } = createKnownWordCacheHarness(config);
+  const originalDateNow = Date.now;
 
   try {
+    Date.now = () => 120_000;
     fs.writeFileSync(
       statePath,
       JSON.stringify({
         version: 2,
-        refreshedAtMs: Date.now() - 61_000,
+        refreshedAtMs: 59_000,
         scope: '{"refreshMinutes":1,"scope":"is:note","fieldsWord":"Word"}',
         words: ['猫'],
         notes: {
@@ -156,6 +168,7 @@ test('KnownWordCacheManager startLifecycle immediately refreshes stale persisted
     assert.equal(manager.isKnownWord('猫'), false);
     assert.equal(manager.isKnownWord('犬'), true);
   } finally {
+    Date.now = originalDateNow;
     manager.stopLifecycle();
     cleanup();
   }

src/anki-integration/polling.test.ts

@@ -4,35 +4,41 @@ import test from 'node:test';
 import { PollingRunner } from './polling';
 
 test('polling runner records newly added cards after initialization', async () => {
+  const originalDateNow = Date.now;
   const recordedCards: number[] = [];
   let tracked = new Set<number>();
   const responses = [
     [10, 11],
     [10, 11, 12, 13],
   ];
-  const runner = new PollingRunner({
-    getDeck: () => 'Mining',
-    getPollingRate: () => 250,
-    findNotes: async () => responses.shift() ?? [],
-    shouldAutoUpdateNewCards: () => true,
-    processNewCard: async () => undefined,
-    recordCardsAdded: (count) => {
-      recordedCards.push(count);
-    },
-    isUpdateInProgress: () => false,
-    setUpdateInProgress: () => undefined,
-    getTrackedNoteIds: () => tracked,
-    setTrackedNoteIds: (noteIds) => {
-      tracked = noteIds;
-    },
-    showStatusNotification: () => undefined,
-    logDebug: () => undefined,
-    logInfo: () => undefined,
-    logWarn: () => undefined,
-  });
+  try {
+    Date.now = () => 120_000;
+    const runner = new PollingRunner({
+      getDeck: () => 'Mining',
+      getPollingRate: () => 250,
+      findNotes: async () => responses.shift() ?? [],
+      shouldAutoUpdateNewCards: () => true,
+      processNewCard: async () => undefined,
+      recordCardsAdded: (count) => {
+        recordedCards.push(count);
+      },
+      isUpdateInProgress: () => false,
+      setUpdateInProgress: () => undefined,
+      getTrackedNoteIds: () => tracked,
+      setTrackedNoteIds: (noteIds) => {
+        tracked = noteIds;
+      },
+      showStatusNotification: () => undefined,
+      logDebug: () => undefined,
+      logInfo: () => undefined,
+      logWarn: () => undefined,
+    });
 
-  await runner.pollOnce();
-  await runner.pollOnce();
+    await runner.pollOnce();
+    await runner.pollOnce();
 
-  assert.deepEqual(recordedCards, [2]);
+    assert.deepEqual(recordedCards, [2]);
+  } finally {
+    Date.now = originalDateNow;
+  }
 });

src/ci-workflow.test.ts

@@ -5,6 +5,10 @@ import { resolve } from 'node:path';
 
 const ciWorkflowPath = resolve(__dirname, '../.github/workflows/ci.yml');
 const ciWorkflow = readFileSync(ciWorkflowPath, 'utf8');
+const packageJsonPath = resolve(__dirname, '../package.json');
+const packageJson = JSON.parse(readFileSync(packageJsonPath, 'utf8')) as {
+  scripts: Record<string, string>;
+};
 
 test('ci workflow lints changelog fragments', () => {
   assert.match(ciWorkflow, /bun run changelog:lint/);
@@ -18,3 +22,17 @@ test('ci workflow checks pull requests for required changelog fragments', () =>
 test('ci workflow verifies generated config examples stay in sync', () => {
   assert.match(ciWorkflow, /bun run verify:config-example/);
 });
+
+test('package scripts expose a sharded maintained source coverage lane with lcov output', () => {
+  assert.equal(
+    packageJson.scripts['test:coverage:src'],
+    'bun run scripts/run-coverage-lane.ts bun-src-full --coverage-dir coverage/test-src',
+  );
+});
+
+test('ci workflow runs the maintained source coverage lane and uploads lcov output', () => {
+  assert.match(ciWorkflow, /name: Coverage suite \(maintained source lane\)/);
+  assert.match(ciWorkflow, /run: bun run test:coverage:src/);
+  assert.match(ciWorkflow, /name: Upload coverage artifact/);
+  assert.match(ciWorkflow, /path: coverage\/test-src\/lcov\.info/);
+});

src/config/config.test.ts

@@ -4,7 +4,7 @@ import * as fs from 'fs';
 import * as os from 'os';
 import * as path from 'path';
 import { ConfigService, ConfigStartupParseError } from './service';
-import { DEFAULT_CONFIG, RUNTIME_OPTION_REGISTRY } from './definitions';
+import { DEFAULT_CONFIG, RUNTIME_OPTION_REGISTRY, deepMergeRawConfig } from './definitions';
 import { generateConfigTemplate } from './template';
 
 function makeTempDir(): string {
@@ -1032,6 +1032,61 @@ test('reloadConfigStrict parse failure does not mutate raw config or warnings',
   assert.deepEqual(service.getWarnings(), beforeWarnings);
 });
 
+test('SM-012 config paths do not use JSON serialize-clone helpers', () => {
+  const definitionsSource = fs.readFileSync(
+    path.join(process.cwd(), 'src/config/definitions.ts'),
+    'utf-8',
+  );
+  const serviceSource = fs.readFileSync(path.join(process.cwd(), 'src/config/service.ts'), 'utf-8');
+
+  assert.equal(definitionsSource.includes('JSON.parse(JSON.stringify('), false);
+  assert.equal(serviceSource.includes('JSON.parse(JSON.stringify('), false);
+});
+
+test('getRawConfig returns a detached clone', () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, 'config.jsonc'),
+    `{
+      "ankiConnect": {
+        "tags": ["SubMiner"]
+      }
+    }`,
+    'utf-8',
+  );
+
+  const service = new ConfigService(dir);
+  const raw = service.getRawConfig();
+  raw.ankiConnect!.tags!.push('mutated');
+
+  assert.deepEqual(service.getRawConfig().ankiConnect?.tags, ['SubMiner']);
+});
+
+test('deepMergeRawConfig returns a detached merged clone', () => {
+  const base = {
+    ankiConnect: {
+      tags: ['SubMiner'],
+      behavior: {
+        autoUpdateNewCards: true,
+      },
+    },
+  };
+
+  const merged = deepMergeRawConfig(base, {
+    ankiConnect: {
+      behavior: {
+        autoUpdateNewCards: false,
+      },
+    },
+  });
+
+  merged.ankiConnect!.tags!.push('mutated');
+  merged.ankiConnect!.behavior!.autoUpdateNewCards = true;
+
+  assert.deepEqual(base.ankiConnect?.tags, ['SubMiner']);
+  assert.equal(base.ankiConnect?.behavior?.autoUpdateNewCards, true);
+});
+
 test('warning emission order is deterministic across reloads', () => {
   const dir = makeTempDir();
   const configPath = path.join(dir, 'config.jsonc');

src/config/definitions.ts

@@ -84,11 +84,11 @@ export const CONFIG_OPTION_REGISTRY = [
 export { CONFIG_TEMPLATE_SECTIONS };
 
 export function deepCloneConfig(config: ResolvedConfig): ResolvedConfig {
-  return JSON.parse(JSON.stringify(config)) as ResolvedConfig;
+  return structuredClone(config);
 }
 
 export function deepMergeRawConfig(base: RawConfig, patch: RawConfig): RawConfig {
-  const clone = JSON.parse(JSON.stringify(base)) as Record<string, unknown>;
+  const clone = structuredClone(base) as Record<string, unknown>;
   const patchObject = patch as Record<string, unknown>;
 
   const mergeInto = (target: Record<string, unknown>, source: Record<string, unknown>): void => {

src/config/service.ts

@@ -61,7 +61,7 @@ export class ConfigService {
   }
 
   getRawConfig(): RawConfig {
-    return JSON.parse(JSON.stringify(this.rawConfig)) as RawConfig;
+    return structuredClone(this.rawConfig);
   }
 
   getWarnings(): ConfigValidationWarning[] {

src/core/services/immersion-tracker/maintenance.test.ts

@@ -8,7 +8,6 @@ import {
   pruneRawRetention,
   pruneRollupRetention,
   runOptimizeMaintenance,
-  toMonthKey,
 } from './maintenance';
 import { ensureSchema } from './storage';
 
@@ -31,9 +30,9 @@ test('pruneRawRetention uses session retention separately from telemetry retenti
 
   try {
     ensureSchema(db);
-    const nowMs = 90 * 86_400_000;
-    const staleEndedAtMs = nowMs - 40 * 86_400_000;
-    const keptEndedAtMs = nowMs - 5 * 86_400_000;
+    const nowMs = 1_000_000_000;
+    const staleEndedAtMs = nowMs - 400_000_000;
+    const keptEndedAtMs = nowMs - 50_000_000;
 
     db.exec(`
       INSERT INTO imm_videos (
@@ -49,14 +48,14 @@ test('pruneRawRetention uses session retention separately from telemetry retenti
       INSERT INTO imm_session_telemetry (
         session_id, sample_ms, total_watched_ms, active_watched_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES
-        (1, ${nowMs - 2 * 86_400_000}, 0, 0, ${nowMs}, ${nowMs}),
-        (2, ${nowMs - 12 * 60 * 60 * 1000}, 0, 0, ${nowMs}, ${nowMs});
+        (1, ${nowMs - 200_000_000}, 0, 0, ${nowMs}, ${nowMs}),
+        (2, ${nowMs - 10_000_000}, 0, 0, ${nowMs}, ${nowMs});
     `);
 
     const result = pruneRawRetention(db, nowMs, {
-      eventsRetentionMs: 7 * 86_400_000,
-      telemetryRetentionMs: 1 * 86_400_000,
-      sessionsRetentionMs: 30 * 86_400_000,
+      eventsRetentionMs: 120_000_000,
+      telemetryRetentionMs: 80_000_000,
+      sessionsRetentionMs: 300_000_000,
     });
 
     const remainingSessions = db
@@ -88,9 +87,9 @@ test('raw retention keeps rollups and rollup retention prunes them separately',
 
   try {
     ensureSchema(db);
-    const nowMs = Date.UTC(2026, 2, 16, 12, 0, 0, 0);
-    const oldDay = Math.floor((nowMs - 90 * 86_400_000) / 86_400_000);
-    const oldMonth = toMonthKey(nowMs - 400 * 86_400_000);
+    const nowMs = 1_000_000_000;
+    const oldDay = Math.floor((nowMs - 200_000_000) / 86_400_000);
+    const oldMonth = 196912;
 
     db.exec(`
       INSERT INTO imm_videos (
@@ -101,12 +100,12 @@ test('raw retention keeps rollups and rollup retention prunes them separately',
       INSERT INTO imm_sessions (
         session_id, session_uuid, video_id, started_at_ms, ended_at_ms, status, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, 'session-1', 1, ${nowMs - 90 * 86_400_000}, ${nowMs - 90 * 86_400_000 + 1_000}, 2, ${nowMs}, ${nowMs}
+        1, 'session-1', 1, ${nowMs - 200_000_000}, ${nowMs - 199_999_000}, 2, ${nowMs}, ${nowMs}
       );
       INSERT INTO imm_session_telemetry (
         session_id, sample_ms, total_watched_ms, active_watched_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, ${nowMs - 90 * 86_400_000}, 0, 0, ${nowMs}, ${nowMs}
+        1, ${nowMs - 200_000_000}, 0, 0, ${nowMs}, ${nowMs}
       );
       INSERT INTO imm_daily_rollups (
         rollup_day, video_id, total_sessions, total_active_min, total_lines_seen,
@@ -123,9 +122,9 @@ test('raw retention keeps rollups and rollup retention prunes them separately',
     `);
 
     pruneRawRetention(db, nowMs, {
-      eventsRetentionMs: 7 * 86_400_000,
-      telemetryRetentionMs: 30 * 86_400_000,
-      sessionsRetentionMs: 30 * 86_400_000,
+      eventsRetentionMs: 120_000_000,
+      telemetryRetentionMs: 120_000_000,
+      sessionsRetentionMs: 120_000_000,
     });
 
     const rollupsAfterRawPrune = db
@@ -139,8 +138,8 @@ test('raw retention keeps rollups and rollup retention prunes them separately',
     assert.equal(monthlyAfterRawPrune?.total, 1);
 
     const rollupPrune = pruneRollupRetention(db, nowMs, {
-      dailyRollupRetentionMs: 30 * 86_400_000,
-      monthlyRollupRetentionMs: 365 * 86_400_000,
+      dailyRollupRetentionMs: 120_000_000,
+      monthlyRollupRetentionMs: 1,
     });
 
     const rollupsAfterRollupPrune = db

src/core/services/immersion-tracker/maintenance.ts

@@ -61,19 +61,19 @@ export function pruneRawRetention(
   const sessionsCutoff = nowMs - policy.sessionsRetentionMs;
 
   const deletedSessionEvents = (
-    db.prepare(`DELETE FROM imm_session_events WHERE ts_ms < ?`).run(eventCutoff) as {
+    db.prepare(`DELETE FROM imm_session_events WHERE ts_ms < ?`).run(toDbMs(eventCutoff)) as {
       changes: number;
     }
   ).changes;
   const deletedTelemetryRows = (
-    db.prepare(`DELETE FROM imm_session_telemetry WHERE sample_ms < ?`).run(telemetryCutoff) as {
-      changes: number;
-    }
+    db
+      .prepare(`DELETE FROM imm_session_telemetry WHERE sample_ms < ?`)
+      .run(toDbMs(telemetryCutoff)) as { changes: number }
   ).changes;
   const deletedEndedSessions = (
     db
       .prepare(`DELETE FROM imm_sessions WHERE ended_at_ms IS NOT NULL AND ended_at_ms < ?`)
-      .run(sessionsCutoff) as { changes: number }
+      .run(toDbMs(sessionsCutoff)) as { changes: number }
   ).changes;
 
   return {

src/core/services/jellyfin-remote.test.ts

@@ -263,7 +263,9 @@ test('reportProgress posts timeline payload and treats failure as non-fatal', as
     audioStreamIndex: 1,
     subtitleStreamIndex: 2,
   });
-  const expectedPostedPayload = JSON.parse(JSON.stringify(expectedPayload));
+  const expectedPostedPayload = Object.fromEntries(
+    Object.entries(structuredClone(expectedPayload)).filter(([, value]) => value !== undefined),
+  );
 
   const ok = await service.reportProgress({
     itemId: 'movie-2',

src/core/services/tokenizer/yomitan-parser-runtime.test.ts

@@ -1255,7 +1255,7 @@ test('dictionary settings helpers upsert and remove dictionary entries without r
   const deps = createDeps(async (script) => {
     scripts.push(script);
     if (script.includes('optionsGetFull')) {
-      return JSON.parse(JSON.stringify(optionsFull));
+      return structuredClone(optionsFull);
     }
     if (script.includes('setAllSettings')) {
       return true;

src/main/controller-config-update.test.ts

@@ -1,8 +1,18 @@
 import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import path from 'node:path';
 import test from 'node:test';
 
 import { applyControllerConfigUpdate } from './controller-config-update.js';
 
+test('SM-012 controller config update path does not use JSON serialize-clone helpers', () => {
+  const source = fs.readFileSync(
+    path.join(process.cwd(), 'src/main/controller-config-update.ts'),
+    'utf-8',
+  );
+  assert.equal(source.includes('JSON.parse(JSON.stringify('), false);
+});
+
 test('applyControllerConfigUpdate replaces binding descriptors instead of deep-merging them', () => {
   const next = applyControllerConfigUpdate(
     {
@@ -52,3 +62,16 @@ test('applyControllerConfigUpdate merges buttonIndices while replacing only upda
   assert.deepEqual(next.bindings?.toggleLookup, { kind: 'button', buttonIndex: 0 });
   assert.deepEqual(next.bindings?.closeLookup, { kind: 'none' });
 });
+
+test('applyControllerConfigUpdate detaches updated binding values from the patch object', () => {
+  const update = {
+    bindings: {
+      toggleLookup: { kind: 'button' as const, buttonIndex: 7 },
+    },
+  };
+
+  const next = applyControllerConfigUpdate(undefined, update);
+  update.bindings.toggleLookup.buttonIndex = 99;
+
+  assert.deepEqual(next.bindings?.toggleLookup, { kind: 'button', buttonIndex: 7 });
+});

src/main/controller-config-update.ts

@@ -28,7 +28,7 @@ export function applyControllerConfigUpdate(
       [keyof RawControllerBindings, RawControllerBindings[keyof RawControllerBindings] | undefined]
     >) {
       if (value === undefined) continue;
-      (nextBindings as Record<string, unknown>)[key] = JSON.parse(JSON.stringify(value));
+      (nextBindings as Record<string, unknown>)[key] = structuredClone(value);
     }
 
     nextController.bindings = nextBindings;

src/main/runtime/anilist-post-watch-main-deps.test.ts

@@ -21,7 +21,7 @@ test('process next anilist retry update main deps builder maps callbacks', async
     now: () => 7,
   })();
 
-  assert.deepEqual(deps.nextReady(), { key: 'k', title: 't', episode: 1 });
+  assert.deepEqual(deps.nextReady(), { key: 'k', title: 't', season: null, episode: 1 });
   deps.refreshRetryQueueState();
   deps.setLastAttemptAt(1);
   deps.setLastError('x');

src/main/runtime/anilist-setup.test.ts

@@ -84,51 +84,63 @@ test('findAnilistSetupDeepLinkArgvUrl returns null when missing', () => {
 });
 
 test('consumeAnilistSetupCallbackUrl persists token and closes window for callback URL', () => {
+  const originalDateNow = Date.now;
   const events: string[] = [];
-  const handled = consumeAnilistSetupCallbackUrl({
-    rawUrl: 'https://anilist.subminer.moe/#access_token=saved-token',
-    saveToken: (value: string) => events.push(`save:${value}`),
-    setCachedToken: (value: string) => events.push(`cache:${value}`),
-    setResolvedState: (timestampMs: number) =>
-      events.push(`state:${timestampMs > 0 ? 'ok' : 'bad'}`),
-    setSetupPageOpened: (opened: boolean) => events.push(`opened:${opened}`),
-    onSuccess: () => events.push('success'),
-    closeWindow: () => events.push('close'),
-  });
+  try {
+    Date.now = () => 120_000;
+    const handled = consumeAnilistSetupCallbackUrl({
+      rawUrl: 'https://anilist.subminer.moe/#access_token=saved-token',
+      saveToken: (value: string) => events.push(`save:${value}`),
+      setCachedToken: (value: string) => events.push(`cache:${value}`),
+      setResolvedState: (timestampMs: number) =>
+        events.push(`state:${timestampMs > 0 ? 'ok' : 'bad'}`),
+      setSetupPageOpened: (opened: boolean) => events.push(`opened:${opened}`),
+      onSuccess: () => events.push('success'),
+      closeWindow: () => events.push('close'),
+    });
 
-  assert.equal(handled, true);
-  assert.deepEqual(events, [
-    'save:saved-token',
-    'cache:saved-token',
-    'state:ok',
-    'opened:false',
-    'success',
-    'close',
-  ]);
+    assert.equal(handled, true);
+    assert.deepEqual(events, [
+      'save:saved-token',
+      'cache:saved-token',
+      'state:ok',
+      'opened:false',
+      'success',
+      'close',
+    ]);
+  } finally {
+    Date.now = originalDateNow;
+  }
 });
 
 test('consumeAnilistSetupCallbackUrl persists token for subminer deep link URL', () => {
+  const originalDateNow = Date.now;
   const events: string[] = [];
-  const handled = consumeAnilistSetupCallbackUrl({
-    rawUrl: 'subminer://anilist-setup?access_token=saved-token',
-    saveToken: (value: string) => events.push(`save:${value}`),
-    setCachedToken: (value: string) => events.push(`cache:${value}`),
-    setResolvedState: (timestampMs: number) =>
-      events.push(`state:${timestampMs > 0 ? 'ok' : 'bad'}`),
-    setSetupPageOpened: (opened: boolean) => events.push(`opened:${opened}`),
-    onSuccess: () => events.push('success'),
-    closeWindow: () => events.push('close'),
-  });
+  try {
+    Date.now = () => 120_000;
+    const handled = consumeAnilistSetupCallbackUrl({
+      rawUrl: 'subminer://anilist-setup?access_token=saved-token',
+      saveToken: (value: string) => events.push(`save:${value}`),
+      setCachedToken: (value: string) => events.push(`cache:${value}`),
+      setResolvedState: (timestampMs: number) =>
+        events.push(`state:${timestampMs > 0 ? 'ok' : 'bad'}`),
+      setSetupPageOpened: (opened: boolean) => events.push(`opened:${opened}`),
+      onSuccess: () => events.push('success'),
+      closeWindow: () => events.push('close'),
+    });
 
-  assert.equal(handled, true);
-  assert.deepEqual(events, [
-    'save:saved-token',
-    'cache:saved-token',
-    'state:ok',
-    'opened:false',
-    'success',
-    'close',
-  ]);
+    assert.equal(handled, true);
+    assert.deepEqual(events, [
+      'save:saved-token',
+      'cache:saved-token',
+      'state:ok',
+      'opened:false',
+      'success',
+      'close',
+    ]);
+  } finally {
+    Date.now = originalDateNow;
+  }
 });
 
 test('consumeAnilistSetupCallbackUrl ignores non-callback URLs', () => {

src/release-workflow.test.ts

@@ -36,6 +36,13 @@ test('release workflow verifies generated config examples before packaging artif
   assert.match(releaseWorkflow, /bun run verify:config-example/);
 });
 
+test('release quality gate runs the maintained source coverage lane and uploads lcov output', () => {
+  assert.match(releaseWorkflow, /name: Coverage suite \(maintained source lane\)/);
+  assert.match(releaseWorkflow, /run: bun run test:coverage:src/);
+  assert.match(releaseWorkflow, /name: Upload coverage artifact/);
+  assert.match(releaseWorkflow, /path: coverage\/test-src\/lcov\.info/);
+});
+
 test('release build jobs install and cache stats dependencies before packaging', () => {
   assert.match(releaseWorkflow, /build-linux:[\s\S]*stats\/node_modules/);
   assert.match(releaseWorkflow, /build-macos:[\s\S]*stats\/node_modules/);

src/runtime-options.test.ts

@@ -0,0 +1,64 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import path from 'node:path';
+import test from 'node:test';
+
+import { RuntimeOptionsManager } from './runtime-options';
+
+test('SM-012 runtime options path does not use JSON serialize-clone helpers', () => {
+  const source = fs.readFileSync(path.join(process.cwd(), 'src/runtime-options.ts'), 'utf-8');
+  assert.equal(source.includes('JSON.parse(JSON.stringify('), false);
+});
+
+test('RuntimeOptionsManager returns detached effective Anki config copies', () => {
+  const baseConfig = {
+    deck: 'Mining',
+    note: 'Sentence',
+    tags: ['SubMiner'],
+    behavior: {
+      autoUpdateNewCards: true,
+      updateIntervalMs: 5000,
+    },
+    fieldMapping: {
+      sentence: 'Sentence',
+      meaning: 'Meaning',
+      audio: 'Audio',
+      image: 'Image',
+      context: 'Context',
+      source: 'Source',
+      definition: 'Definition',
+      sequence: 'Sequence',
+      contextSecondary: 'ContextSecondary',
+      contextTertiary: 'ContextTertiary',
+      primarySpelling: 'PrimarySpelling',
+      primaryReading: 'PrimaryReading',
+      wordSpelling: 'WordSpelling',
+      wordReading: 'WordReading',
+    },
+    duplicates: {
+      mode: 'note' as const,
+      scope: 'deck' as const,
+      allowedFields: [],
+    },
+    ai: {
+      enabled: false,
+      model: '',
+      systemPrompt: '',
+    },
+  };
+
+  const manager = new RuntimeOptionsManager(
+    () => structuredClone(baseConfig),
+    {
+      applyAnkiPatch: () => undefined,
+      onOptionsChanged: () => undefined,
+    },
+  );
+
+  const effective = manager.getEffectiveAnkiConnectConfig();
+  effective.tags!.push('mutated');
+  effective.behavior!.autoUpdateNewCards = false;
+
+  assert.deepEqual(baseConfig.tags, ['SubMiner']);
+  assert.equal(baseConfig.behavior.autoUpdateNewCards, true);
+});

src/runtime-options.ts

@@ -29,7 +29,7 @@ import { RUNTIME_OPTION_REGISTRY, RuntimeOptionRegistryEntry } from './config';
 type RuntimeOverrides = Record<string, unknown>;
 
 function deepClone<T>(value: T): T {
-  return JSON.parse(JSON.stringify(value)) as T;
+  return structuredClone(value);
 }
 
 function getPathValue(source: Record<string, unknown>, path: string): unknown {