diff --git a/apps/api/src/auth/localAuthMiddleware.ts b/apps/api/src/auth/localAuthMiddleware.ts
new file mode 100644
index 0000000..f4eef0b
--- /dev/null
+++ b/apps/api/src/auth/localAuthMiddleware.ts
@@ -0,0 +1,96 @@
+/**
+ * localAuthMiddleware.ts — local-session cookie → c.set('user') middleware (AUTH-LOCAL-04).
+ *
+ * Reads the `local-session` cookie, validates the JWT, fetches the users row,
+ * and populates `c.get('user')` with the same shape as devAuthBypass so that all
+ * downstream routes work unchanged.
+ *
+ * Mount in index.ts AFTER devAuthBypass() and BEFORE the OIDC guard:
+ *   app.use('/api/*', devAuthBypass());
+ *   app.use('/api/*', localAuthMiddleware());   ← HERE
+ *   if (!devBypassActive) {
+ *     app.use('/api/*', oidcAuthMiddleware());  ← skip if c.get('user') set
+ *   }
+ *
+ * Security contract:
+ *   - If c.get('user') is already set (devAuthBypass ran first): no-op passthrough.
+ *     This is Test 4 — dev user is not overwritten.
+ *   - If no 'local-session' cookie is present: pure passthrough WITHOUT calling
+ *     c.set('user', undefined). The OIDC guard fires on falsy c.get('user') only when
+ *     the value was never set — calling c.set('user', undefined) would suppress it.
+ *     This is Pitfall-1 / Test 2.
+ *   - If cookie is valid but the users row is gone: passthrough (no crash).
+ *     This is Test 3.
+ *
+ * ContextVariableMap: the `user` shape is declared in devBypass.ts. Import it as a
+ * side-effect so c.set('user', ...) is typed correctly throughout this file.
+ */
+
+// Side-effect import: extends ContextVariableMap with the `user` key (Pitfall — shared shape).
+import './devBypass.js';
+import type { MiddlewareHandler } from 'hono';
+import { eq } from 'drizzle-orm';
+import { db } from '../db/client.js';
+import { users } from '../db/schema.js';
+import { verifyLocalSessionCookie } from './localSession.js';
+
+/**
+ * Returns a Hono MiddlewareHandler that:
+ *   1. Checks if c.get('user') is already set — no-op if so (devAuthBypass-first).
+ *   2. Calls verifyLocalSessionCookie(c) — returns null if no cookie / invalid / expired.
+ *   3. On null: calls next() WITHOUT setting user (pure passthrough — OIDC guard can fire).
+ *   4. On valid userId: SELECTs the users row; if found, c.set('user', {...}); always next().
+ */
+export function localAuthMiddleware(): MiddlewareHandler {
+  return async (c, next) => {
+    // If a prior middleware (devAuthBypass) already set the user, do not overwrite.
+    if (c.get('user')) {
+      await next();
+      return;
+    }
+
+    // Verify the local-session JWT cookie — returns userId or null.
+    // verifyLocalSessionCookie returns null (never throws) on any error (Pitfall 9 guard).
+    const userId = await verifyLocalSessionCookie(c);
+
+    if (userId === null) {
+      // No valid local session — pass through WITHOUT setting c.get('user').
+      // CRITICAL: Do NOT call c.set('user', undefined) — that sets the key to undefined
+      // which is falsy but "set", breaking the OIDC guard's c.get('user') check (Pitfall 1).
+      await next();
+      return;
+    }
+
+    // Load the users row to populate the same shape as DEV_USER.
+    const [row] = await db
+      .select({
+        id: users.id,
+        oidcIss: users.oidcIss,
+        oidcSub: users.oidcSub,
+        displayName: users.displayName,
+        color: users.color,
+      })
+      .from(users)
+      .where(eq(users.id, userId))
+      .limit(1);
+
+    if (!row) {
+      // userId from JWT but no users row (deleted user) — passthrough without setting user.
+      await next();
+      return;
+    }
+
+    // Populate c.get('user') with the same shape as DEV_USER (devBypass.ts ContextVariableMap).
+    // oidcIss/oidcSub: local users have nullable oidcIss/oidcSub — use fallback strings so the
+    // shape matches typeof DEV_USER (all required fields, no undefined in the value object).
+    c.set('user', {
+      id: row.id,
+      oidcIss: row.oidcIss ?? 'local',
+      oidcSub: row.oidcSub ?? String(row.id),
+      displayName: row.displayName ?? null,
+      color: row.color ?? '#4A90D9',
+    });
+
+    await next();
+  };
+}
diff --git a/apps/api/src/index.ts b/apps/api/src/index.ts
index 214822f..6bd5dd3 100644
--- a/apps/api/src/index.ts
+++ b/apps/api/src/index.ts
@@ -11,12 +11,15 @@ import { listsRouter, listItemsRouter } from './routes/lists.js';
 import { pushRouter } from './routes/push.js';
 import { adminRouter } from './routes/admin.js';
 import { setupRouter } from './routes/setup.js';
+import { authModeRouter } from './routes/authMode.js';
+import { localAuthRouter } from './routes/localAuth.js';
 import {
   oidcAuthMiddleware,
   processOAuthCallback,
   oidcConfigFallbackMiddleware,
 } from './auth/middleware.js';
 import { devAuthBypass } from './auth/devBypass.js';
+import { localAuthMiddleware } from './auth/localAuthMiddleware.js';
 import { persistSessionCookie } from './auth/persistSessionCookie.js';
 import { startBrokerPoller } from './broker/poller.js';
 import { startOutboxWorker, initOutboxTrigger } from './broker/outboxWorker.js';
@@ -48,15 +51,26 @@ app.route('/health', healthRouter);
 // 423 lock after setup is complete (SETUP-04 / D-10).
 app.route('/api/setup', setupRouter);
 
+// Phase 19 — pre-auth auth routes: GET /api/auth/mode and POST /api/auth/local/login, /logout.
+// Mounted BEFORE devAuthBypass so they are reachable without a session (D-01 / AUTH-LOCAL-05).
+app.route('/api/auth', authModeRouter);
+app.route('/api/auth', localAuthRouter);
+
 // Dev-auth bypass — no-op passthrough unless DEV_AUTH_BYPASS=true AND NODE_ENV!='production'.
 // When active, injects DEV_USER into the Hono context and the OIDC guard is NOT mounted.
 // Must be mounted BEFORE oidcAuthMiddleware (T-02-01 mitigation; see auth/devBypass.ts).
 app.use('/api/*', devAuthBypass());
 
+// Phase 19 — local-session middleware: sets c.get('user') from 'local-session' JWT cookie.
+// No-op passthrough when no cookie is present — the OIDC guard fires for unauthenticated.
+// Runs AFTER devAuthBypass (which may set c.get('user') first) and BEFORE the OIDC guard.
+// The OIDC guard below is wrapped to skip when c.get('user') is already set (Pitfall 1 guard).
+app.use('/api/*', localAuthMiddleware());
+
 // Protect all /api/* routes with OIDC session middleware (AUTH-01, T-02-05).
 // Skipped entirely when devBypassActive so that local dev works without Authelia.
 // In production devBypassActive is always false — OIDC is unconditionally mounted.
-// Unauthenticated requests receive a 302 redirect to Authelia's authorize endpoint.
+// Unauthenticated requests receive a 302 redirect to the OIDC authorize endpoint.
 // OIDC_AUTH_EXTERNAL_URL is MANDATORY behind Pangolin to construct the correct
 // redirect_uri (Pitfall 1). Set it to https://familysync.<domain>.
 if (!devBypassActive) {
@@ -67,7 +81,16 @@ if (!devBypassActive) {
   // A2 CONFIRMED: oidcAuthMiddleware() reads process.env per-request (call time), so
   // injecting into process.env here is safe and effective (see auth/middleware.ts A2 note).
   app.use('/api/*', oidcConfigFallbackMiddleware);
-  app.use('/api/*', oidcAuthMiddleware());
+  // Phase 19 / D-03: OIDC guard wrapped to skip when c.get('user') is already set.
+  // A valid local-session (or dev-bypass) user must NOT be 302-redirected to the OIDC
+  // provider — the skip-when-set wrapper is the coexistence seam (D-03 / RESEARCH Pitfall 1).
+  app.use('/api/*', async (c, next) => {
+    if (c.get('user')) {
+      await next();
+      return;
+    }
+    await oidcAuthMiddleware()(c, next);
+  });
   // Re-issues the session-scoped oidc-auth cookie as persistent so PWA sessions survive close (AUTH-02).
   app.use('/api/*', persistSessionCookie());
 }
diff --git a/apps/api/src/routes/authMode.ts b/apps/api/src/routes/authMode.ts
new file mode 100644
index 0000000..a4dcadd
--- /dev/null
+++ b/apps/api/src/routes/authMode.ts
@@ -0,0 +1,50 @@
+/**
+ * authMode.ts — GET /api/auth/mode pre-auth endpoint (AUTH-LOCAL-05).
+ *
+ * Returns { localEnabled: boolean, oidcEnabled: boolean } reflecting the current
+ * authentication configuration. This endpoint is intentionally reachable before
+ * authentication (same pre-auth pattern as GET /api/setup/status).
+ *
+ * Mount in index.ts BEFORE devAuthBypass and OIDC guard:
+ *   app.route('/api/auth', authModeRouter);   ← pre-auth
+ *
+ * Response contract:
+ *   - localEnabled: always true — local auth is the default, always available (D-01).
+ *   - oidcEnabled: true when OIDC_ISSUER env var is set, OR when app_config has
+ *     an oidc_issuer row (supports wizard-configured OIDC before container restart).
+ *
+ * No auth gate, no isSetupLocked() check — the PWA fetches this on app load before
+ * knowing if the user is authenticated.
+ */
+
+import { Hono } from 'hono';
+import { eq } from 'drizzle-orm';
+import { db } from '../db/client.js';
+import { appConfig } from '../db/schema.js';
+
+export const authModeRouter = new Hono();
+
+/**
+ * GET /  (mounted as /api/auth, so effective path is GET /api/auth/mode)
+ *
+ * Checks OIDC_ISSUER env var first (process.env is cheapest); falls back to
+ * app_config DB row if env var is absent (wizard-configured OIDC).
+ */
+authModeRouter.get('/mode', async (c) => {
+  // localEnabled: always true (D-01)
+  // oidcEnabled: env var first, then app_config fallback
+  const issuerFromEnv = process.env.OIDC_ISSUER;
+  let oidcEnabled = Boolean(issuerFromEnv);
+
+  if (!oidcEnabled) {
+    // Check app_config for oidc_issuer (wizard-written, pre-restart-fallback pattern from middleware.ts)
+    const [row] = await db
+      .select({ value: appConfig.value })
+      .from(appConfig)
+      .where(eq(appConfig.key, 'oidc_issuer'))
+      .limit(1);
+    oidcEnabled = Boolean(row?.value);
+  }
+
+  return c.json({ localEnabled: true, oidcEnabled });
+});
diff --git a/apps/api/src/routes/localAuth.ts b/apps/api/src/routes/localAuth.ts
new file mode 100644
index 0000000..f3b3663
--- /dev/null
+++ b/apps/api/src/routes/localAuth.ts
@@ -0,0 +1,155 @@
+/**
+ * localAuth.ts — local authentication routes (AUTH-LOCAL-03, AUTH-LOCAL-06).
+ *
+ * Routes:
+ *   POST /api/auth/local/login  — rate-limited credential verify + session cookie issue
+ *   POST /api/auth/local/logout — clear local-session cookie
+ *   GET  /api/auth/local/logout — alias for POST /logout (some browsers prefer GET)
+ *
+ * Mounted in index.ts as app.route('/api/auth', localAuthRouter) BEFORE any auth middleware.
+ * This means POST /api/auth/local/login is reachable without a session (pre-auth, per D-01).
+ *
+ * Security (T-19-11, T-19-12, T-19-14):
+ *   - noEchoHook on login: Zod errors NEVER return received values (T-19-14 / Pitfall 7).
+ *   - Dummy-hash timing defense: verifyPassword is always called, even for unknown usernames,
+ *     to prevent timing-oracle username enumeration attacks (T-19-12 / RESEARCH Pitfall 2).
+ *   - Same 401 body for wrong password AND unknown username — no field discrimination (T-19-12).
+ *   - Per-IP in-memory rate-limiting: 5 failures → 429; 10 failures → 423 (T-19-11).
+ *   - Lockout (423) cleared only by admin password reset — no self-service unlock.
+ */
+
+import { Hono } from 'hono';
+import type { Context } from 'hono';
+import { zValidator } from '@hono/zod-validator';
+import { z } from 'zod';
+import { eq } from 'drizzle-orm';
+import { db } from '../db/client.js';
+import { localCredentials } from '../db/schema.js';
+import { verifyPassword, hashPassword } from '../auth/localCredentials.js';
+import { issueLocalSessionCookie, clearLocalSessionCookie } from '../auth/localSession.js';
+
+export const localAuthRouter = new Hono();
+
+// ---------------------------------------------------------------------------
+// noEchoHook — NEVER return Zod validation error details for the login route.
+// Zod's error object contains issues[].received which may echo the submitted password.
+// Always return { error: 'Invalid request' } 400, no other fields (T-19-14).
+// ---------------------------------------------------------------------------
+
+const noEchoHook = (result: { success: boolean }, c: Context) => {
+  if (!result.success) {
+    return c.json({ error: 'Invalid request' }, 400);
+  }
+};
+
+// ---------------------------------------------------------------------------
+// Zod schema for login body
+// ---------------------------------------------------------------------------
+
+const loginSchema = z.object({
+  username: z.string().min(1).max(128).trim(),
+  password: z.string().min(1).max(1000),
+});
+
+// ---------------------------------------------------------------------------
+// Per-IP rate-limiting state (in-memory Map — household scale, no Redis needed).
+//
+// State shape per IP: { count, lockedUntil (epoch ms), lockedOut (bool) }
+//   count >= RATE_WINDOW_FAILURES AND Date.now() < lockedUntil → 429
+//   count >= LOCKOUT_FAILURES → 423 (permanent until admin reset)
+//   Success → delete entry (clears counter)
+//
+// RATE_WINDOW_FAILURES: 5 failures → 60s cooldown (429)
+// LOCKOUT_FAILURES:    10 failures → account locked (423)
+// ---------------------------------------------------------------------------
+
+export const loginAttempts = new Map<string, { count: number; lockedUntil: number; lockedOut: boolean }>();
+
+const RATE_WINDOW_FAILURES = 5;
+const RATE_WINDOW_SECS = 60;
+const LOCKOUT_FAILURES = 10;
+
+// Pre-computed dummy hash used to run verifyPassword on unknown-username paths
+// (timing defense — prevents timing-oracle username enumeration, RESEARCH Pitfall 2).
+// Computed once at module load time; the actual value is never used for auth.
+const DUMMY_HASH = hashPassword('dummy-constant-time-filler-xyzzy');
+
+// ---------------------------------------------------------------------------
+// POST /local/login  →  POST /api/auth/local/login
+// ---------------------------------------------------------------------------
+
+localAuthRouter.post('/local/login', zValidator('json', loginSchema, noEchoHook), async (c) => {
+  // Derive client IP from Pangolin-set X-Forwarded-For header; fall back to host header.
+  const ip = c.req.header('x-forwarded-for')?.split(',')[0]?.trim()
+    ?? c.req.raw.headers.get('host')
+    ?? 'unknown';
+
+  const attempt = loginAttempts.get(ip);
+
+  // 423: account locked (>= LOCKOUT_FAILURES total failures, admin must reset)
+  if (attempt?.lockedOut) {
+    return c.json({ error: 'Account locked' }, 423);
+  }
+
+  // 429: rate window — >= RATE_WINDOW_FAILURES failures within the cooldown window
+  if (attempt && attempt.count >= RATE_WINDOW_FAILURES && Date.now() < attempt.lockedUntil) {
+    return c.json({ error: 'Too many attempts' }, 429);
+  }
+
+  const { username, password } = c.req.valid('json');
+
+  // Look up local_credentials by username
+  let cred: { userId: number; passwordHash: string } | undefined;
+  try {
+    const [found] = await db
+      .select({ userId: localCredentials.userId, passwordHash: localCredentials.passwordHash })
+      .from(localCredentials)
+      .where(eq(localCredentials.username, username))
+      .limit(1);
+    cred = found;
+  } catch (err) {
+    console.error('[localAuth/POST /local/login] DB error:', err instanceof Error ? err.message : String(err));
+    return c.json({ error: 'Service unavailable' }, 503);
+  }
+
+  // ALWAYS run verifyPassword — even for unknown usernames — to prevent timing-oracle
+  // username enumeration (T-19-12 / RESEARCH Pitfall 2). Use a pre-computed dummy hash
+  // so the scrypt work is always performed regardless of whether username was found.
+  const valid = cred
+    ? verifyPassword(cred.passwordHash, password)
+    : verifyPassword(DUMMY_HASH, password);
+
+  if (!valid || !cred) {
+    // Increment failure counter
+    const cur = loginAttempts.get(ip) ?? { count: 0, lockedUntil: 0, lockedOut: false };
+    cur.count += 1;
+    cur.lockedUntil = Date.now() + RATE_WINDOW_SECS * 1000;
+    cur.lockedOut = cur.count >= LOCKOUT_FAILURES;
+    loginAttempts.set(ip, cur);
+    // Same 401 body for wrong password AND unknown username — no field discrimination (T-19-12)
+    return c.json({ error: 'Invalid credentials' }, 401);
+  }
+
+  // Success: clear failure counter, issue the local-session JWT cookie, return ok
+  loginAttempts.delete(ip);
+  try {
+    await issueLocalSessionCookie(c, cred.userId);
+  } catch (err) {
+    console.error('[localAuth/POST /local/login] Cookie issue error:', err instanceof Error ? err.message : String(err));
+    return c.json({ error: 'Service unavailable' }, 503);
+  }
+  return c.json({ ok: true }, 200);
+});
+
+// ---------------------------------------------------------------------------
+// POST /local/logout  →  POST /api/auth/local/logout
+// GET  /local/logout  →  GET  /api/auth/local/logout (browser-redirect alias)
+// ---------------------------------------------------------------------------
+
+async function handleLogout(c: Context) {
+  clearLocalSessionCookie(c);
+  return c.json({ ok: true }, 200);
+}
+
+localAuthRouter.post('/local/logout', handleLogout);
+localAuthRouter.get('/local/logout', handleLogout);