diff --git a/tests/unit/auth-config.spec.ts b/tests/unit/auth-config.spec.ts
deleted file mode 100644
index 24fb496..0000000
--- a/tests/unit/auth-config.spec.ts
+++ /dev/null
@@ -1,119 +0,0 @@
-import { test, expect } from '@playwright/test';
-import { isAnonymousAuthSessionsEnabled, isGithubAuthEnabled } from '../../src/lib/server/auth/config';
-
-const ORIGINAL_BASE_URL = process.env.BASE_URL;
-const ORIGINAL_AUTH_SECRET = process.env.AUTH_SECRET;
-const ORIGINAL_USE_ANON = process.env.USE_ANONYMOUS_AUTH_SESSIONS;
-const ORIGINAL_GITHUB_CLIENT_ID = process.env.GITHUB_CLIENT_ID;
-const ORIGINAL_GITHUB_CLIENT_SECRET = process.env.GITHUB_CLIENT_SECRET;
-
-function restoreEnv() {
-  if (ORIGINAL_BASE_URL === undefined) delete process.env.BASE_URL;
-  else process.env.BASE_URL = ORIGINAL_BASE_URL;
-
-  if (ORIGINAL_AUTH_SECRET === undefined) delete process.env.AUTH_SECRET;
-  else process.env.AUTH_SECRET = ORIGINAL_AUTH_SECRET;
-
-  if (ORIGINAL_USE_ANON === undefined) delete process.env.USE_ANONYMOUS_AUTH_SESSIONS;
-  else process.env.USE_ANONYMOUS_AUTH_SESSIONS = ORIGINAL_USE_ANON;
-
-  if (ORIGINAL_GITHUB_CLIENT_ID === undefined) delete process.env.GITHUB_CLIENT_ID;
-  else process.env.GITHUB_CLIENT_ID = ORIGINAL_GITHUB_CLIENT_ID;
-
-  if (ORIGINAL_GITHUB_CLIENT_SECRET === undefined) delete process.env.GITHUB_CLIENT_SECRET;
-  else process.env.GITHUB_CLIENT_SECRET = ORIGINAL_GITHUB_CLIENT_SECRET;
-}
-
-function setAuthEnabledEnv() {
-  process.env.BASE_URL = 'http://localhost:3003';
-  process.env.AUTH_SECRET = 'test-secret';
-}
-
-test.describe('auth config anonymous-session flag', () => {
-  test.afterEach(() => {
-    restoreEnv();
-  });
-
-  test('returns false when auth is disabled', () => {
-    delete process.env.BASE_URL;
-    delete process.env.AUTH_SECRET;
-    process.env.USE_ANONYMOUS_AUTH_SESSIONS = 'true';
-
-    expect(isAnonymousAuthSessionsEnabled()).toBe(false);
-  });
-
-  test('defaults to false when env var is unset', () => {
-    setAuthEnabledEnv();
-    delete process.env.USE_ANONYMOUS_AUTH_SESSIONS;
-
-    expect(isAnonymousAuthSessionsEnabled()).toBe(false);
-  });
-
-  test('returns true only when env var is true', () => {
-    setAuthEnabledEnv();
-    process.env.USE_ANONYMOUS_AUTH_SESSIONS = 'true';
-
-    expect(isAnonymousAuthSessionsEnabled()).toBe(true);
-  });
-
-  test('returns false when env var is false', () => {
-    setAuthEnabledEnv();
-    process.env.USE_ANONYMOUS_AUTH_SESSIONS = 'false';
-
-    expect(isAnonymousAuthSessionsEnabled()).toBe(false);
-  });
-
-  test('falls back to false for invalid values', () => {
-    setAuthEnabledEnv();
-    process.env.USE_ANONYMOUS_AUTH_SESSIONS = '1';
-
-    expect(isAnonymousAuthSessionsEnabled()).toBe(false);
-  });
-});
-
-test.describe('auth config github-auth flag', () => {
-  test.afterEach(() => {
-    restoreEnv();
-  });
-
-  test('returns false when auth is disabled', () => {
-    delete process.env.BASE_URL;
-    delete process.env.AUTH_SECRET;
-    process.env.GITHUB_CLIENT_ID = 'some-id';
-    process.env.GITHUB_CLIENT_SECRET = 'some-secret';
-
-    expect(isGithubAuthEnabled()).toBe(false);
-  });
-
-  test('returns false when GITHUB_CLIENT_ID is missing', () => {
-    setAuthEnabledEnv();
-    delete process.env.GITHUB_CLIENT_ID;
-    process.env.GITHUB_CLIENT_SECRET = 'some-secret';
-
-    expect(isGithubAuthEnabled()).toBe(false);
-  });
-
-  test('returns false when GITHUB_CLIENT_SECRET is missing', () => {
-    setAuthEnabledEnv();
-    process.env.GITHUB_CLIENT_ID = 'some-id';
-    delete process.env.GITHUB_CLIENT_SECRET;
-
-    expect(isGithubAuthEnabled()).toBe(false);
-  });
-
-  test('returns false when both GitHub env vars are missing', () => {
-    setAuthEnabledEnv();
-    delete process.env.GITHUB_CLIENT_ID;
-    delete process.env.GITHUB_CLIENT_SECRET;
-
-    expect(isGithubAuthEnabled()).toBe(false);
-  });
-
-  test('returns true when auth is enabled and both GitHub env vars are set', () => {
-    setAuthEnabledEnv();
-    process.env.GITHUB_CLIENT_ID = 'some-id';
-    process.env.GITHUB_CLIENT_SECRET = 'some-secret';
-
-    expect(isGithubAuthEnabled()).toBe(true);
-  });
-});
diff --git a/tests/unit/auth-config.vitest.spec.ts b/tests/unit/auth-config.vitest.spec.ts
new file mode 100644
index 0000000..eac330d
--- /dev/null
+++ b/tests/unit/auth-config.vitest.spec.ts
@@ -0,0 +1,111 @@
+import { describe, expect, test } from 'vitest';
+import { getAuthBaseUrl, isAnonymousAuthSessionsEnabled, isAuthEnabled, isGithubAuthEnabled } from '../../src/lib/server/auth/config';
+import { withEnv } from './support/env';
+
+describe('auth config contract', () => {
+  test('auth is enabled only when AUTH_SECRET and BASE_URL are both set', async () => {
+    await withEnv(
+      {
+        AUTH_SECRET: undefined,
+        BASE_URL: undefined,
+      },
+      async () => {
+        expect(isAuthEnabled()).toBe(false);
+        expect(getAuthBaseUrl()).toBeNull();
+      },
+    );
+
+    await withEnv(
+      {
+        AUTH_SECRET: 'unit-secret',
+        BASE_URL: 'http://localhost:3003',
+      },
+      async () => {
+        expect(isAuthEnabled()).toBe(true);
+        expect(getAuthBaseUrl()).toBe('http://localhost:3003');
+      },
+    );
+  });
+
+  test.each([
+    { envValue: undefined, expected: false },
+    { envValue: 'true', expected: true },
+    { envValue: 'false', expected: false },
+    { envValue: '1', expected: false },
+    { envValue: 'TRUE', expected: true },
+  ])(
+    'anonymous sessions honor strict boolean parsing when auth is enabled (value: $envValue)',
+    async ({ envValue, expected }) => {
+      await withEnv(
+        {
+          AUTH_SECRET: 'unit-secret',
+          BASE_URL: 'http://localhost:3003',
+          USE_ANONYMOUS_AUTH_SESSIONS: envValue,
+        },
+        async () => {
+          expect(isAnonymousAuthSessionsEnabled()).toBe(expected);
+        },
+      );
+    },
+  );
+
+  test('anonymous sessions are always disabled when auth is disabled', async () => {
+    await withEnv(
+      {
+        AUTH_SECRET: undefined,
+        BASE_URL: undefined,
+        USE_ANONYMOUS_AUTH_SESSIONS: 'true',
+      },
+      async () => {
+        expect(isAnonymousAuthSessionsEnabled()).toBe(false);
+      },
+    );
+  });
+
+  test.each([
+    {
+      title: 'returns false when auth is disabled',
+      env: {
+        AUTH_SECRET: undefined,
+        BASE_URL: undefined,
+        GITHUB_CLIENT_ID: 'id',
+        GITHUB_CLIENT_SECRET: 'secret',
+      },
+      expected: false,
+    },
+    {
+      title: 'returns false when GitHub client id is missing',
+      env: {
+        AUTH_SECRET: 'unit-secret',
+        BASE_URL: 'http://localhost:3003',
+        GITHUB_CLIENT_ID: undefined,
+        GITHUB_CLIENT_SECRET: 'secret',
+      },
+      expected: false,
+    },
+    {
+      title: 'returns false when GitHub client secret is missing',
+      env: {
+        AUTH_SECRET: 'unit-secret',
+        BASE_URL: 'http://localhost:3003',
+        GITHUB_CLIENT_ID: 'id',
+        GITHUB_CLIENT_SECRET: undefined,
+      },
+      expected: false,
+    },
+    {
+      title: 'returns true when auth is enabled and GitHub credentials are present',
+      env: {
+        AUTH_SECRET: 'unit-secret',
+        BASE_URL: 'http://localhost:3003',
+        GITHUB_CLIENT_ID: 'id',
+        GITHUB_CLIENT_SECRET: 'secret',
+      },
+      expected: true,
+    },
+  ])('$title', async ({ env, expected }) => {
+    await withEnv(env, async () => {
+      expect(isGithubAuthEnabled()).toBe(expected);
+    });
+  });
+});
diff --git a/tests/unit/rate-limit-runtime-settings.spec.ts b/tests/unit/rate-limit-runtime-settings.vitest.spec.ts
similarity index 76%
rename from tests/unit/rate-limit-runtime-settings.spec.ts
rename to tests/unit/rate-limit-runtime-settings.vitest.spec.ts
index df7748d..b39f3e9 100644
--- a/tests/unit/rate-limit-runtime-settings.spec.ts
+++ b/tests/unit/rate-limit-runtime-settings.vitest.spec.ts
@@ -1,8 +1,8 @@
-import { expect, test } from '@playwright/test';
+import { describe, expect, test } from 'vitest';
 
 import { RUNTIME_CONFIG_SCHEMA } from '../../src/lib/server/admin/settings';
 
-test.describe('TTS rate limit runtime config seeds', () => {
+describe('TTS rate limit runtime config seeds', () => {
   test('defaults disable TTS daily rate limiting', () => {
     expect(RUNTIME_CONFIG_SCHEMA.disableTtsRateLimit.default).toBe(true);
   });
@@ -12,6 +12,9 @@ test.describe('TTS rate limit runtime config seeds', () => {
     expect(RUNTIME_CONFIG_SCHEMA.disableTtsRateLimit.parseEnv('false')).toBe(false);
     expect(RUNTIME_CONFIG_SCHEMA.disableTtsRateLimit.parseEnv('1')).toBe(true);
     expect(RUNTIME_CONFIG_SCHEMA.disableTtsRateLimit.parseEnv('0')).toBe(false);
+    expect(RUNTIME_CONFIG_SCHEMA.disableTtsRateLimit.parseEnv('on')).toBe(true);
+    expect(RUNTIME_CONFIG_SCHEMA.disableTtsRateLimit.parseEnv('no')).toBe(false);
+    expect(RUNTIME_CONFIG_SCHEMA.disableTtsRateLimit.parseEnv('invalid')).toBeUndefined();
   });
 
   test('daily limit values are runtime-only (no env seed vars)', () => {
diff --git a/tests/unit/server-error-contract.spec.ts b/tests/unit/server-error-contract.vitest.spec.ts
similarity index 62%
rename from tests/unit/server-error-contract.spec.ts
rename to tests/unit/server-error-contract.vitest.spec.ts
index 84307d7..e489af3 100644
--- a/tests/unit/server-error-contract.spec.ts
+++ b/tests/unit/server-error-contract.vitest.spec.ts
@@ -1,4 +1,4 @@
-import { expect, test } from '@playwright/test';
+import { describe, expect, test } from 'vitest';
 import {
   ServerAppError,
   createServerAppError,
@@ -7,10 +7,12 @@ import {
   toApiErrorBody,
   toHttpStatus,
 } from '../../src/lib/server/errors/contract';
+import { makeServerAppErrorInput } from './support/factories';
 
-test.describe('server error contract', () => {
+describe('server error contract', () => {
   test('normalizes unknown throwable to fallback shape', () => {
     const normalized = normalizeServerError('boom');
+
     expect(normalized.code).toBe('UNKNOWN_SERVER_ERROR');
     expect(normalized.errorClass).toBe('unknown');
     expect(normalized.httpStatus).toBe(500);
@@ -19,15 +21,17 @@ test.describe('server error contract', () => {
   });
 
   test('preserves ServerAppError metadata', () => {
-    const err = createServerAppError({
+    const err = createServerAppError(makeServerAppErrorInput({
       code: 'USER_PROGRESS_UPDATE_FAILED',
       message: 'Failed to update progress',
       errorClass: 'db',
       retryable: true,
       httpStatus: 500,
       details: { operation: 'update_progress' },
-    });
+    }));
+
     const normalized = normalizeServerError(err);
+
     expect(isServerAppError(err)).toBe(true);
     expect(normalized.code).toBe('USER_PROGRESS_UPDATE_FAILED');
     expect(normalized.errorClass).toBe('db');
@@ -36,6 +40,22 @@ test.describe('server error contract', () => {
     expect(normalized.details?.operation).toBe('update_progress');
   });
 
+  test('normalizes partially-shaped thrown errors with code sanitization', () => {
+    const thrown = Object.assign(new Error('Timed out waiting for storage read'), {
+      code: 'not_valid_code',
+      errorClass: 'timeout',
+      httpStatus: 604,
+      retryable: true,
+    });
+
+    const normalized = normalizeServerError(thrown);
+
+    expect(normalized.code).toBe('UNKNOWN_SERVER_ERROR');
+    expect(normalized.errorClass).toBe('timeout');
+    expect(normalized.httpStatus).toBe(599);
+    expect(normalized.retryable).toBe(true);
+  });
+
   test('maps normalized errors to API body + status', () => {
     const normalized = normalizeServerError(
       new ServerAppError({
@@ -44,7 +64,9 @@ test.describe('server error contract', () => {
         errorClass: 'upstream',
       }),
     );
+
     const body = toApiErrorBody(normalized, { includeDetails: false });
+
     expect(body).toEqual({
       error: 'Upstream failure',
       errorCode: 'UPSTREAM_TTS_ERROR',
@@ -52,4 +74,12 @@ test.describe('server error contract', () => {
     });
     expect(toHttpStatus(normalized)).toBe(502);
   });
+
+  test('rejects invalid server error code at creation boundary', () => {
+    expect(() => createServerAppError(makeServerAppErrorInput({
+      code: 'bad-code',
+      message: 'Invalid',
+      errorClass: 'validation',
+    }))).toThrow(/Invalid ServerAppError code/i);
+  });
 });
diff --git a/tests/unit/server-error-response.spec.ts b/tests/unit/server-error-response.spec.ts
deleted file mode 100644
index a5ed779..0000000
--- a/tests/unit/server-error-response.spec.ts
+++ /dev/null
@@ -1,43 +0,0 @@
-import { expect, test } from '@playwright/test';
-import { errorResponse } from '../../src/lib/server/errors/next-response';
-import { createServerAppError } from '../../src/lib/server/errors/contract';
-
-test.describe('server error response helper', () => {
-  test('returns mapped 4xx response with explicit app code', async () => {
-    const response = errorResponse(
-      createServerAppError({
-        code: 'AUTH_UNAUTHORIZED',
-        message: 'Unauthorized',
-        errorClass: 'auth',
-        httpStatus: 401,
-        retryable: false,
-      }),
-      {
-        apiErrorMessage: 'Unauthorized',
-      },
-    );
-
-    expect(response.status).toBe(401);
-    await expect(response.json()).resolves.toEqual({
-      error: 'Unauthorized',
-      errorCode: 'AUTH_UNAUTHORIZED',
-      retryable: false,
-    });
-  });
-
-  test('normalizes unknown errors to safe 500 without stack leakage', async () => {
-    const response = errorResponse(new Error('sensitive internal details'), {
-      apiErrorMessage: 'Internal Server Error',
-      normalize: { code: 'UNKNOWN_SERVER_ERROR', errorClass: 'unknown' },
-    });
-    const body = await response.json();
-    expect(response.status).toBe(500);
-    expect(body).toEqual({
-      error: 'Internal Server Error',
-      errorCode: 'UNKNOWN_SERVER_ERROR',
-      retryable: false,
-    });
-    expect(JSON.stringify(body)).not.toContain('stack');
-    expect(JSON.stringify(body)).not.toContain('cause');
-  });
-});
diff --git a/tests/unit/server-error-response.vitest.spec.ts b/tests/unit/server-error-response.vitest.spec.ts
new file mode 100644
index 0000000..5bfba1d
--- /dev/null
+++ b/tests/unit/server-error-response.vitest.spec.ts
@@ -0,0 +1,90 @@
+import { describe, expect, test } from 'vitest';
+import { createServerAppError } from '../../src/lib/server/errors/contract';
+import { asRouteErrorContext, errorResponse, withErrorBoundary } from '../../src/lib/server/errors/next-response';
+import { createServerLoggerStub } from './support/server-stubs';
+import { makeServerAppErrorInput } from './support/factories';
+
+describe('server error response helper', () => {
+  test('returns mapped 4xx response with explicit app code', async () => {
+    const response = errorResponse(
+      createServerAppError(makeServerAppErrorInput({
+        code: 'AUTH_UNAUTHORIZED',
+        message: 'Unauthorized',
+        errorClass: 'auth',
+        httpStatus: 401,
+        retryable: false,
+      })),
+      {
+        apiErrorMessage: 'Unauthorized',
+      },
+    );
+
+    expect(response.status).toBe(401);
+    await expect(response.json()).resolves.toEqual({
+      error: 'Unauthorized',
+      errorCode: 'AUTH_UNAUTHORIZED',
+      retryable: false,
+    });
+  });
+
+  test('normalizes unknown errors to safe 500 without stack leakage', async () => {
+    const response = errorResponse(new Error('sensitive internal details'), {
+      apiErrorMessage: 'Internal Server Error',
+      normalize: { code: 'UNKNOWN_SERVER_ERROR', errorClass: 'unknown' },
+    });
+    const body = await response.json();
+    expect(response.status).toBe(500);
+    expect(body).toEqual({
+      error: 'Internal Server Error',
+      errorCode: 'UNKNOWN_SERVER_ERROR',
+      retryable: false,
+    });
+    expect(JSON.stringify(body)).not.toContain('stack');
+    expect(JSON.stringify(body)).not.toContain('cause');
+  });
+
+  test('withErrorBoundary returns normalized error response and emits a structured log', async () => {
+    const logger = createServerLoggerStub();
+    const handler = withErrorBoundary(
+      async () => {
+        throw new Error('storage dependency timed out');
+      },
+      {
+        route: '/api/unit-test',
+        logger: logger as never,
+        event: 'unit_test.route.failed',
+        msg: 'Route failed',
+        normalize: {
+          code: 'DOCUMENT_BLOB_FETCH_FAILED',
+          errorClass: 'storage',
+        },
+        apiErrorMessage: 'Failed to fetch document blob',
+      },
+    );
+
+    const response = await handler();
+    const body = await response.json();
+
+    expect(response.status).toBe(503);
+    expect(body).toEqual({
+      error: 'Failed to fetch document blob',
+      errorCode: 'DOCUMENT_BLOB_FETCH_FAILED',
+      retryable: true,
+    });
+    expect(logger.error).toHaveBeenCalledTimes(1);
+  });
+
+  test('asRouteErrorContext derives method and request id consistently', () => {
+    const context = asRouteErrorContext({
+      request: { method: 'PATCH' } as never,
+      route: '/api/runtime-config',
+      requestId: 'req-123',
+    });
+
+    expect(context).toEqual({
+      route: '/api/runtime-config',
+      method: 'PATCH',
+      requestId: 'req-123',
+    });
+  });
+});
diff --git a/tests/unit/server-route-error-mappings.spec.ts b/tests/unit/server-route-error-mappings.spec.ts
deleted file mode 100644
index ac1a131..0000000
--- a/tests/unit/server-route-error-mappings.spec.ts
+++ /dev/null
@@ -1,78 +0,0 @@
-import { expect, test } from '@playwright/test';
-import { errorResponse } from '../../src/lib/server/errors/next-response';
-import { AdminProviderError } from '../../src/lib/server/admin/providers';
-
-test.describe('route error mapping contract', () => {
-  test('admin provider validation errors map to 4xx via route normalize policy', async () => {
-    const adminError = new AdminProviderError('slug is required', 400);
-    const response = errorResponse(adminError, {
-      apiErrorMessage: adminError.message,
-      normalize: {
-        code: 'ADMIN_PROVIDERS_CREATE_REQUEST_FAILED',
-        errorClass: 'validation',
-        httpStatus: adminError.status,
-        retryable: false,
-      },
-    });
-
-    expect(response.status).toBe(400);
-    await expect(response.json()).resolves.toEqual({
-      error: 'slug is required',
-      errorCode: 'ADMIN_PROVIDERS_CREATE_REQUEST_FAILED',
-      retryable: false,
-    });
-  });
-
-  test('documents storage failures map to retryable 503', async () => {
-    const response = errorResponse(new Error('blobstore timeout'), {
-      apiErrorMessage: 'Failed to fetch document blob',
-      normalize: {
-        code: 'DOCUMENT_BLOB_FETCH_FAILED',
-        errorClass: 'storage',
-      },
-    });
-
-    expect(response.status).toBe(503);
-    await expect(response.json()).resolves.toEqual({
-      error: 'Failed to fetch document blob',
-      errorCode: 'DOCUMENT_BLOB_FETCH_FAILED',
-      retryable: true,
-    });
-  });
-
-  test('audiobook upstream failures map to retryable 502', async () => {
-    const response = errorResponse(new Error('provider overloaded'), {
-      apiErrorMessage: 'Failed to process audio chapter',
-      normalize: {
-        code: 'AUDIOBOOK_CHAPTER_PROCESS_FAILED',
-        errorClass: 'upstream',
-      },
-    });
-
-    expect(response.status).toBe(502);
-    await expect(response.json()).resolves.toEqual({
-      error: 'Failed to process audio chapter',
-      errorCode: 'AUDIOBOOK_CHAPTER_PROCESS_FAILED',
-      retryable: true,
-    });
-  });
-
-  test('user export auth initialization failure maps to 500 auth classification', async () => {
-    const response = errorResponse(new Error('Auth not initialized'), {
-      apiErrorMessage: 'Auth not initialized',
-      normalize: {
-        code: 'USER_EXPORT_AUTH_NOT_INITIALIZED',
-        errorClass: 'auth',
-        httpStatus: 500,
-        retryable: false,
-      },
-    });
-
-    expect(response.status).toBe(500);
-    await expect(response.json()).resolves.toEqual({
-      error: 'Auth not initialized',
-      errorCode: 'USER_EXPORT_AUTH_NOT_INITIALIZED',
-      retryable: false,
-    });
-  });
-});
diff --git a/tests/unit/server-route-error-mappings.vitest.spec.ts b/tests/unit/server-route-error-mappings.vitest.spec.ts
new file mode 100644
index 0000000..6d5bb23
--- /dev/null
+++ b/tests/unit/server-route-error-mappings.vitest.spec.ts
@@ -0,0 +1,80 @@
+import { describe, expect, test } from 'vitest';
+import { AdminProviderError } from '../../src/lib/server/admin/providers';
+import { errorResponse } from '../../src/lib/server/errors/next-response';
+import { makeServerErrorContext } from './support/factories';
+
+describe('route error mapping contract', () => {
+  test('admin provider validation errors map to 4xx via route normalize policy', async () => {
+    const adminError = new AdminProviderError('slug is required', 400);
+    const response = errorResponse(adminError, {
+      apiErrorMessage: adminError.message,
+      normalize: makeServerErrorContext({
+        code: 'ADMIN_PROVIDERS_CREATE_REQUEST_FAILED',
+        errorClass: 'validation',
+        httpStatus: adminError.status,
+        retryable: false,
+      }),
+    });
+
+    expect(response.status).toBe(400);
+    await expect(response.json()).resolves.toEqual({
+      error: 'slug is required',
+      errorCode: 'ADMIN_PROVIDERS_CREATE_REQUEST_FAILED',
+      retryable: false,
+    });
+  });
+
+  test.each([
+    {
+      name: 'documents storage failures map to retryable 503',
+      thrown: new Error('blobstore timeout'),
+      apiErrorMessage: 'Failed to fetch document blob',
+      normalize: makeServerErrorContext({
+        code: 'DOCUMENT_BLOB_FETCH_FAILED',
+        errorClass: 'storage',
+      }),
+      expectedStatus: 503,
+      expectedBody: {
+        error: 'Failed to fetch document blob',
+        errorCode: 'DOCUMENT_BLOB_FETCH_FAILED',
+        retryable: true,
+      },
+    },
+    {
+      name: 'audiobook upstream failures map to retryable 502',
+      thrown: new Error('provider overloaded'),
+      apiErrorMessage: 'Failed to process audio chapter',
+      normalize: makeServerErrorContext({
+        code: 'AUDIOBOOK_CHAPTER_PROCESS_FAILED',
+        errorClass: 'upstream',
+      }),
+      expectedStatus: 502,
+      expectedBody: {
+        error: 'Failed to process audio chapter',
+        errorCode: 'AUDIOBOOK_CHAPTER_PROCESS_FAILED',
+        retryable: true,
+      },
+    },
+    {
+      name: 'user export auth initialization failure maps to 500 auth classification',
+      thrown: new Error('Auth not initialized'),
+      apiErrorMessage: 'Auth not initialized',
+      normalize: makeServerErrorContext({
+        code: 'USER_EXPORT_AUTH_NOT_INITIALIZED',
+        errorClass: 'auth',
+        httpStatus: 500,
+        retryable: false,
+      }),
+      expectedStatus: 500,
+      expectedBody: {
+        error: 'Auth not initialized',
+        errorCode: 'USER_EXPORT_AUTH_NOT_INITIALIZED',
+        retryable: false,
+      },
+    },
+  ])('$name', async ({ thrown, apiErrorMessage, normalize, expectedStatus, expectedBody }) => {
+    const response = errorResponse(thrown, { apiErrorMessage, normalize });
+    expect(response.status).toBe(expectedStatus);
+    await expect(response.json()).resolves.toEqual(expectedBody);
+  });
+});
diff --git a/tests/unit/shared-provider-selection.spec.ts b/tests/unit/shared-provider-selection.vitest.spec.ts
similarity index 85%
rename from tests/unit/shared-provider-selection.spec.ts
rename to tests/unit/shared-provider-selection.vitest.spec.ts
index a371989..69d9eb2 100644
--- a/tests/unit/shared-provider-selection.spec.ts
+++ b/tests/unit/shared-provider-selection.vitest.spec.ts
@@ -1,14 +1,11 @@
-import { expect, test } from '@playwright/test';
+import { describe, expect, test } from 'vitest';
 
 import { resolvePreferredSharedProviderSlug } from '../../src/lib/shared/shared-provider-selection';
+import { makeSharedProviders } from './support/factories';
 
-const PROVIDERS = [
-  { slug: 'shared-a' },
-  { slug: 'default-openai' },
-  { slug: 'shared-b' },
-] as const;
+const PROVIDERS = makeSharedProviders(['shared-a', 'default-openai', 'shared-b']);
 
-test.describe('resolvePreferredSharedProviderSlug', () => {
+describe('resolvePreferredSharedProviderSlug', () => {
   test('prefers requested shared slug when present', () => {
     expect(resolvePreferredSharedProviderSlug({
       providers: PROVIDERS,
diff --git a/tests/unit/signup-policy.spec.ts b/tests/unit/signup-policy.vitest.spec.ts
similarity index 76%
rename from tests/unit/signup-policy.spec.ts
rename to tests/unit/signup-policy.vitest.spec.ts
index 190ef67..a74ba83 100644
--- a/tests/unit/signup-policy.spec.ts
+++ b/tests/unit/signup-policy.vitest.spec.ts
@@ -1,9 +1,9 @@
-import { expect, test } from '@playwright/test';
+import { describe, expect, test } from 'vitest';
 
 import { RUNTIME_CONFIG_SCHEMA } from '../../src/lib/server/admin/settings';
 import { assertUserSignupAllowed } from '../../src/lib/server/auth/signup-policy';
 
-test.describe('enableUserSignups runtime config', () => {
+describe('enableUserSignups runtime config', () => {
   test('defaults to enabled', () => {
     expect(RUNTIME_CONFIG_SCHEMA.enableUserSignups.default).toBe(true);
   });
@@ -13,10 +13,13 @@ test.describe('enableUserSignups runtime config', () => {
     expect(RUNTIME_CONFIG_SCHEMA.enableUserSignups.parseEnv('false')).toBe(false);
     expect(RUNTIME_CONFIG_SCHEMA.enableUserSignups.parseEnv('1')).toBe(true);
     expect(RUNTIME_CONFIG_SCHEMA.enableUserSignups.parseEnv('0')).toBe(false);
+    expect(RUNTIME_CONFIG_SCHEMA.enableUserSignups.parseEnv('yes')).toBe(true);
+    expect(RUNTIME_CONFIG_SCHEMA.enableUserSignups.parseEnv('off')).toBe(false);
+    expect(RUNTIME_CONFIG_SCHEMA.enableUserSignups.parseEnv('maybe')).toBeUndefined();
   });
 });
 
-test.describe('signup policy enforcement', () => {
+describe('signup policy enforcement', () => {
   test('allows new non-anonymous users when signups are enabled', () => {
     expect(() => assertUserSignupAllowed({ enableUserSignups: true, isAnonymous: false })).not.toThrow();
   });
diff --git a/tests/unit/support/env.ts b/tests/unit/support/env.ts
new file mode 100644
index 0000000..4f76129
--- /dev/null
+++ b/tests/unit/support/env.ts
@@ -0,0 +1,30 @@
+export type EnvPatch = Record<string, string | undefined>;
+
+export function captureEnv(keys: readonly string[]): EnvPatch {
+  const snapshot: EnvPatch = {};
+  for (const key of keys) {
+    snapshot[key] = process.env[key];
+  }
+  return snapshot;
+}
+
+export function restoreEnv(snapshot: EnvPatch): void {
+  for (const [key, value] of Object.entries(snapshot)) {
+    if (value === undefined) delete process.env[key];
+    else process.env[key] = value;
+  }
+}
+
+export async function withEnv<T>(patch: EnvPatch, run: () => T | Promise<T>): Promise<T> {
+  const keys = Object.keys(patch);
+  const snapshot = captureEnv(keys);
+  for (const [key, value] of Object.entries(patch)) {
+    if (value === undefined) delete process.env[key];
+    else process.env[key] = value;
+  }
+  try {
+    return await run();
+  } finally {
+    restoreEnv(snapshot);
+  }
+}
diff --git a/tests/unit/support/factories.ts b/tests/unit/support/factories.ts
new file mode 100644
index 0000000..cb8835b
--- /dev/null
+++ b/tests/unit/support/factories.ts
@@ -0,0 +1,30 @@
+import type { ServerErrorClass, ServerErrorContext } from '../../../src/lib/server/errors/contract';
+
+export function makeServerAppErrorInput(overrides: Partial<{
+  code: string;
+  message: string;
+  errorClass: ServerErrorClass;
+  httpStatus: number;
+  retryable: boolean;
+  details: Record<string, unknown>;
+  cause: unknown;
+}> = {}) {
+  return {
+    code: 'UNKNOWN_SERVER_ERROR',
+    message: 'Unhandled server failure',
+    errorClass: 'unknown' as const,
+    ...overrides,
+  };
+}
+
+export function makeServerErrorContext(overrides: ServerErrorContext = {}): ServerErrorContext {
+  return {
+    code: 'UNKNOWN_SERVER_ERROR',
+    errorClass: 'unknown',
+    ...overrides,
+  };
+}
+
+export function makeSharedProviders(slugs: readonly string[]): Array<{ slug: string }> {
+  return slugs.map((slug) => ({ slug }));
+}
diff --git a/tests/unit/support/server-stubs.ts b/tests/unit/support/server-stubs.ts
new file mode 100644
index 0000000..c8b7e29
--- /dev/null
+++ b/tests/unit/support/server-stubs.ts
@@ -0,0 +1,22 @@
+import type { Mock } from 'vitest';
+import { vi } from 'vitest';
+
+export interface ServerLoggerStub {
+  child: Mock;
+  debug: Mock;
+  error: Mock;
+  info: Mock;
+  warn: Mock;
+}
+
+export function createServerLoggerStub(): ServerLoggerStub {
+  const logger = {
+    error: vi.fn(),
+    warn: vi.fn(),
+    info: vi.fn(),
+    debug: vi.fn(),
+    child: vi.fn(),
+  } as ServerLoggerStub;
+  logger.child.mockReturnValue(logger);
+  return logger;
+}
diff --git a/vitest.config.ts b/vitest.config.ts
index fb32f4f..fe7ca8b 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -1,9 +1,30 @@
 import { defineConfig } from 'vitest/config';
+import { fileURLToPath } from 'node:url';
+
+const srcDir = fileURLToPath(new URL('./src/', import.meta.url));
+const alias = [
+  { find: /^@\//, replacement: `${srcDir}` },
+  { find: '@', replacement: srcDir },
+];
 
 export default defineConfig({
+  resolve: {
+    alias,
+  },
   test: {
+    alias,
     reporters: process.env.CI ? ['default', 'github'] : ['default'],
     projects: [
+      {
+        resolve: {
+          alias,
+        },
+        test: {
+          name: 'openreader',
+          environment: 'node',
+          include: ['tests/unit/**/*.vitest.spec.ts'],
+        },
+      },
       {
         test: {
           name: 'compute-core',