diff --git a/apps/api/src/index.ts b/apps/api/src/index.ts
index ff3252a..5ac0ed4 100644
--- a/apps/api/src/index.ts
+++ b/apps/api/src/index.ts
@@ -11,6 +11,7 @@ import { listsRouter, listItemsRouter } from './routes/lists.js'
 import { pushRouter } from './routes/push.js'
 import { oidcAuthMiddleware, processOAuthCallback } from './auth/middleware.js'
 import { devAuthBypass } from './auth/devBypass.js'
+import { persistSessionCookie } from './auth/persistSessionCookie.js'
 import { startBrokerPoller } from './broker/poller.js'
 import { startOutboxWorker } from './broker/outboxWorker.js'
 import { startReminderScheduler } from './broker/reminderScheduler.js'
@@ -49,6 +50,8 @@ app.use('/api/*', devAuthBypass())
 // redirect_uri (Pitfall 1). Set it to https://familysync.<domain>.
 if (!devBypassActive) {
   app.use('/api/*', oidcAuthMiddleware())
+  // Re-issues the session-scoped oidc-auth cookie as persistent so PWA sessions survive close (AUTH-02).
+  app.use('/api/*', persistSessionCookie())
 }
 
 // Protected API routes (behind oidcAuthMiddleware)
diff --git a/apps/api/tests/auth/persistSessionCookie.test.ts b/apps/api/tests/auth/persistSessionCookie.test.ts
new file mode 100644
index 0000000..dde4403
--- /dev/null
+++ b/apps/api/tests/auth/persistSessionCookie.test.ts
@@ -0,0 +1,122 @@
+/**
+ * persistSessionCookie() middleware — unit tests.
+ *
+ * Tests the two critical behavioral properties:
+ *   A (persist path):  when oidcAuthJwt is set on context, the response includes an
+ *                      oidc-auth Set-Cookie with Max-Age, SameSite=Lax, HttpOnly, Secure.
+ *   B (guard path):    when oidcAuthJwt is NOT set, no oidc-auth Set-Cookie is emitted
+ *                      (the no-resurrection security guard).
+ *
+ * Does NOT call @hono/oidc-auth — sets the context variable directly to keep this a
+ * pure unit test that runs without MariaDB or any external service.
+ */
+
+import { describe, it, expect, afterEach } from 'vitest'
+import { Hono } from 'hono'
+import { persistSessionCookie } from '../../src/auth/persistSessionCookie.js'
+
+// Read the cookie name the same way the implementation does so the test stays correct
+// if OIDC_COOKIE_NAME is overridden in the environment.
+const COOKIE_NAME = process.env.OIDC_COOKIE_NAME ?? 'oidc-auth'
+
+afterEach(() => {
+  // Nothing to restore: these tests do not mutate process.env.
+})
+
+describe('persistSessionCookie middleware', () => {
+  describe('Test A — persist path (oidcAuthJwt truthy)', () => {
+    it('emits an oidc-auth Set-Cookie with Max-Age, SameSite=Lax, HttpOnly, and Secure', async () => {
+      const app = new Hono()
+
+      // Simulate what @hono/oidc-auth does: set a signed session JWT on context.
+      app.use('/api/*', async (c, next) => {
+        c.set('oidcAuthJwt' as never, 'header.payload.sig')
+        await next()
+      })
+
+      app.use('/api/*', persistSessionCookie())
+
+      app.get('/api/test', (c) => c.json({ ok: true }))
+
+      const res = await app.request('/api/test')
+      expect(res.status).toBe(200)
+
+      const setCookieHeader = res.headers.get('set-cookie')
+      expect(setCookieHeader).not.toBeNull()
+
+      // Cookie name must appear in the Set-Cookie value.
+      expect(setCookieHeader).toContain(COOKIE_NAME)
+
+      // Max-Age must be present (persistent cookie, not session-scoped).
+      expect(setCookieHeader?.toLowerCase()).toContain('max-age')
+
+      // SameSite=Lax must be present.
+      expect(setCookieHeader?.toLowerCase()).toContain('samesite=lax')
+
+      // HttpOnly must be present.
+      expect(setCookieHeader?.toLowerCase()).toContain('httponly')
+
+      // Secure must be present.
+      expect(setCookieHeader?.toLowerCase()).toContain('secure')
+    })
+
+    it('re-issues the same JWT value the library provided (no re-signing)', async () => {
+      const dummyJwt = 'header.payload.sig'
+      const app = new Hono()
+
+      app.use('/api/*', async (c, next) => {
+        c.set('oidcAuthJwt' as never, dummyJwt)
+        await next()
+      })
+
+      app.use('/api/*', persistSessionCookie())
+      app.get('/api/test', (c) => c.json({ ok: true }))
+
+      const res = await app.request('/api/test')
+      const setCookieHeader = res.headers.get('set-cookie') ?? ''
+
+      // The cookie value must contain the exact JWT string (URL-encoded = is fine but
+      // the JWT characters must all appear).
+      expect(setCookieHeader).toContain(dummyJwt)
+    })
+  })
+
+  describe('Test B — guard path (oidcAuthJwt falsy / absent)', () => {
+    it('emits NO oidc-auth Set-Cookie when oidcAuthJwt is not set (no resurrection)', async () => {
+      const app = new Hono()
+
+      // Do NOT set oidcAuthJwt — simulates a logged-out or unauthenticated request.
+      app.use('/api/*', persistSessionCookie())
+      app.get('/api/test', (c) => c.json({ ok: true }))
+
+      const res = await app.request('/api/test')
+      expect(res.status).toBe(200)
+
+      const setCookieHeader = res.headers.get('set-cookie')
+
+      // Either no Set-Cookie header at all, or it must not contain the oidc-auth cookie.
+      const hasOidcCookie =
+        setCookieHeader !== null && setCookieHeader.includes(COOKIE_NAME)
+      expect(hasOidcCookie).toBe(false)
+    })
+
+    it('emits NO Set-Cookie when oidcAuthJwt is explicitly set to empty string', async () => {
+      const app = new Hono()
+
+      app.use('/api/*', async (c, next) => {
+        c.set('oidcAuthJwt' as never, '')
+        await next()
+      })
+
+      app.use('/api/*', persistSessionCookie())
+      app.get('/api/test', (c) => c.json({ ok: true }))
+
+      const res = await app.request('/api/test')
+      const setCookieHeader = res.headers.get('set-cookie')
+
+      const hasOidcCookie =
+        setCookieHeader !== null && setCookieHeader.includes(COOKIE_NAME)
+      expect(hasOidcCookie).toBe(false)
+    })
+  })
+})