diff --git a/src/hooks.server.ts b/src/hooks.server.ts
index bb510a6..5fe5093 100644
--- a/src/hooks.server.ts
+++ b/src/hooks.server.ts
@@ -54,16 +54,33 @@ export const handle: Handle = async ({ event, resolve }) => {
     rateLimitType = 'search';
   }
 
+  // Extract user pubkey for rate limiting (authenticated users get higher limits)
+  const userPubkey = event.request.headers.get('X-User-Pubkey') || 
+                     event.request.headers.get('x-user-pubkey') ||
+                     url.searchParams.get('userPubkey') || 
+                     null;
+  
+  // Use user pubkey as identifier if authenticated, otherwise use IP
+  // This allows authenticated users to have per-user limits (can't bypass by changing IP)
+  // and anonymous users are limited by IP (prevents abuse)
+  const rateLimitIdentifier = userPubkey ? `user:${userPubkey}` : `ip:${clientIp}`;
+  const isAnonymous = !userPubkey;
+
   // Check rate limit (skip for Vite internal requests)
   const rateLimitResult = isViteInternalRequest 
     ? { allowed: true, resetAt: Date.now() }
-    : rateLimiter.check(rateLimitType, clientIp);
+    : rateLimiter.check(rateLimitType, rateLimitIdentifier, isAnonymous);
   if (!rateLimitResult.allowed) {
     auditLogger.log({
       ip: clientIp,
       action: `rate_limit.${rateLimitType}`,
       result: 'denied',
-      metadata: { path: url.pathname }
+      metadata: { 
+        path: url.pathname,
+        identifier: rateLimitIdentifier,
+        isAnonymous,
+        userPubkey: userPubkey || null
+      }
     });
     return error(429, `Rate limit exceeded. Try again after ${new Date(rateLimitResult.resetAt).toISOString()}`);
   }
@@ -75,6 +92,27 @@ export const handle: Handle = async ({ event, resolve }) => {
   try {
     const response = await resolve(event);
     
+    // Add security headers
+    response.headers.set('X-Content-Type-Options', 'nosniff');
+    response.headers.set('X-Frame-Options', 'DENY');
+    response.headers.set('X-XSS-Protection', '1; mode=block');
+    response.headers.set('Referrer-Policy', 'strict-origin-when-cross-origin');
+    response.headers.set('Permissions-Policy', 'geolocation=(), microphone=(), camera=()');
+    
+    // Add CSP header (Content Security Policy)
+    const csp = [
+      "default-src 'self'",
+      "script-src 'self' 'unsafe-inline' 'unsafe-eval'", // unsafe-eval needed for Svelte
+      "style-src 'self' 'unsafe-inline'",
+      "img-src 'self' data: https:",
+      "font-src 'self' data:",
+      "connect-src 'self' wss: https:",
+      "frame-ancestors 'none'",
+      "base-uri 'self'",
+      "form-action 'self'"
+    ].join('; ');
+    response.headers.set('Content-Security-Policy', csp);
+    
     // Log successful request if it's a security-sensitive operation
     if (url.pathname.startsWith('/api/')) {
       const duration = Date.now() - startTime;
diff --git a/src/lib/components/NavBar.svelte b/src/lib/components/NavBar.svelte
index fbd3203..7424bb7 100644
--- a/src/lib/components/NavBar.svelte
+++ b/src/lib/components/NavBar.svelte
@@ -1,16 +1,35 @@
 <script lang="ts">
   import { page } from '$app/stores';
+  import { goto } from '$app/navigation';
   import { getPublicKeyWithNIP07, isNIP07Available } from '../services/nostr/nip07-signer.js';
   import { nip19 } from 'nostr-tools';
   import ThemeToggle from './ThemeToggle.svelte';
   import UserBadge from './UserBadge.svelte';
   import { onMount } from 'svelte';
+  import { userStore } from '../stores/user-store.js';
+  import { clearActivity, updateActivity } from '../services/activity-tracker.js';
 
   let userPubkey = $state<string | null>(null);
   let mobileMenuOpen = $state(false);
 
   onMount(async () => {
     await checkAuth();
+    // Update activity on mount
+    updateActivity();
+    
+    // Set up activity tracking for user interactions
+    const updateActivityOnInteraction = () => updateActivity();
+    
+    // Track various user interactions
+    document.addEventListener('click', updateActivityOnInteraction, { passive: true });
+    document.addEventListener('keydown', updateActivityOnInteraction, { passive: true });
+    document.addEventListener('scroll', updateActivityOnInteraction, { passive: true });
+    
+    return () => {
+      document.removeEventListener('click', updateActivityOnInteraction);
+      document.removeEventListener('keydown', updateActivityOnInteraction);
+      document.removeEventListener('scroll', updateActivityOnInteraction);
+    };
   });
 
   function toggleMobileMenu() {
@@ -46,6 +65,12 @@
 
   function logout() {
     userPubkey = null;
+    // Reset user store
+    userStore.reset();
+    // Clear activity tracking
+    clearActivity();
+    // Navigate to home page to reset all component state to anonymous
+    goto('/');
   }
 
   function isActive(path: string): boolean {
diff --git a/src/lib/services/activity-tracker.ts b/src/lib/services/activity-tracker.ts
new file mode 100644
index 0000000..903966f
--- /dev/null
+++ b/src/lib/services/activity-tracker.ts
@@ -0,0 +1,75 @@
+/**
+ * Activity tracker for user sessions
+ * Tracks ONLY the last activity timestamp (no information about what the user did)
+ * Used for 24-hour auto-logout after inactivity
+ * 
+ * SECURITY: Only stores a single timestamp value. No activity details are stored.
+ */
+
+const LAST_ACTIVITY_KEY = 'gitrepublic_last_activity';
+const SESSION_TIMEOUT_MS = 24 * 60 * 60 * 1000; // 24 hours in milliseconds
+
+/**
+ * Update the last activity timestamp
+ * 
+ * SECURITY: Only stores the timestamp (Date.now()). No information about
+ * what the user did is stored. Previous timestamp is overwritten.
+ */
+export function updateActivity(): void {
+  if (typeof window === 'undefined') return;
+  
+  // Only store the timestamp - no activity details
+  const now = Date.now();
+  localStorage.setItem(LAST_ACTIVITY_KEY, now.toString());
+}
+
+/**
+ * Get the last activity timestamp
+ */
+export function getLastActivity(): number | null {
+  if (typeof window === 'undefined') return null;
+  
+  const timestamp = localStorage.getItem(LAST_ACTIVITY_KEY);
+  return timestamp ? parseInt(timestamp, 10) : null;
+}
+
+/**
+ * Check if the session has expired (24 hours since last activity)
+ */
+export function isSessionExpired(): boolean {
+  if (typeof window === 'undefined') return false;
+  
+  const lastActivity = getLastActivity();
+  if (!lastActivity) return false;
+  
+  const now = Date.now();
+  const timeSinceActivity = now - lastActivity;
+  
+  return timeSinceActivity >= SESSION_TIMEOUT_MS;
+}
+
+/**
+ * Clear activity tracking (on logout)
+ */
+export function clearActivity(): void {
+  if (typeof window === 'undefined') return;
+  
+  localStorage.removeItem(LAST_ACTIVITY_KEY);
+}
+
+/**
+ * Get time until session expires (in milliseconds)
+ * Returns 0 if expired or no activity
+ */
+export function getTimeUntilExpiry(): number {
+  if (typeof window === 'undefined') return 0;
+  
+  const lastActivity = getLastActivity();
+  if (!lastActivity) return 0;
+  
+  const now = Date.now();
+  const timeSinceActivity = now - lastActivity;
+  const timeUntilExpiry = SESSION_TIMEOUT_MS - timeSinceActivity;
+  
+  return Math.max(0, timeUntilExpiry);
+}
diff --git a/src/lib/services/nostr/relay-write-proof.ts b/src/lib/services/nostr/relay-write-proof.ts
index 4d24b6b..5281fd4 100644
--- a/src/lib/services/nostr/relay-write-proof.ts
+++ b/src/lib/services/nostr/relay-write-proof.ts
@@ -1,6 +1,10 @@
 /**
  * Service for verifying that a user can write to at least one default relay
- * This replaces rate limiting by requiring proof of relay write capability
+ * This is a trust mechanism - only users who can write to trusted default relays
+ * get unlimited access. This limits access to trusted npubs.
+ * 
+ * The user only needs to be able to write to ONE of the default relays, not all.
+ * If the proof event is found on any default relay, access is granted.
  * 
  * Accepts NIP-98 events (kind 27235) as proof, since publishing a NIP-98 event
  * to a relay proves the user can write to that relay.
@@ -32,7 +36,7 @@ export async function verifyRelayWriteProof(
   proofEvent: NostrEvent,
   userPubkey: string,
   relays: string[] = DEFAULT_NOSTR_RELAYS
-): Promise<{ valid: boolean; error?: string; relay?: string }> {
+): Promise<{ valid: boolean; error?: string; relay?: string; relayDown?: boolean }> {
   // Verify the event signature
   if (!verifyEvent(proofEvent)) {
     return { valid: false, error: 'Invalid event signature' };
@@ -81,6 +85,8 @@ export async function verifyRelayWriteProof(
   }
 
   // Try to verify the event exists on at least one default relay
+  // User only needs write access to ONE of the default relays, not all
+  // This is a trust mechanism - if they can write to any trusted relay, they're trusted
   const nostrClient = new NostrClient(relays);
   try {
     const events = await nostrClient.fetchEvents([
@@ -92,7 +98,7 @@ export async function verifyRelayWriteProof(
     ]);
 
     if (events.length === 0) {
-      return { valid: false, error: 'Proof event not found on any default relay' };
+      return { valid: false, error: 'Proof event not found on any default relay. User must be able to write to at least one default relay.' };
     }
 
     // Verify the fetched event matches
@@ -101,12 +107,17 @@ export async function verifyRelayWriteProof(
       return { valid: false, error: 'Fetched event does not match proof event' };
     }
 
-    // Determine which relay(s) have the event (we can't know for sure, but we verified it exists)
+    // Event found on at least one default relay - user has write access
+    // We can't determine which specific relay(s) have it, but that's fine
+    // The important thing is they can write to at least one trusted relay
     return { valid: true, relay: relays[0] }; // Return first relay as indication
   } catch (error) {
+    // Relay connection failed - this is a network/relay issue, not an auth failure
+    // Return a special error that indicates we should check cache
     return {
       valid: false,
-      error: `Failed to verify proof on relays: ${error instanceof Error ? error.message : String(error)}`
+      error: `Failed to verify proof on relays: ${error instanceof Error ? error.message : String(error)}`,
+      relayDown: true // Flag to indicate relay connectivity issue
     };
   }
 }
diff --git a/src/lib/services/nostr/user-level-service.ts b/src/lib/services/nostr/user-level-service.ts
new file mode 100644
index 0000000..075c3d4
--- /dev/null
+++ b/src/lib/services/nostr/user-level-service.ts
@@ -0,0 +1,132 @@
+/**
+ * Service for determining user access level based on relay write capability
+ * 
+ * SECURITY: User level verification is done server-side via API endpoint.
+ * Client-side checks are only for UI purposes and can be bypassed.
+ * 
+ * Three tiers:
+ * - unlimited: Users with write access to default relays
+ * - rate_limited: Logged-in users without write access
+ * - strictly_rate_limited: Not logged-in users
+ */
+
+import { signEventWithNIP07, isNIP07Available } from './nip07-signer.js';
+import { KIND } from '../../types/nostr.js';
+import { createProofEvent } from './relay-write-proof.js';
+import { nip19 } from 'nostr-tools';
+
+export type UserLevel = 'unlimited' | 'rate_limited' | 'strictly_rate_limited';
+
+export interface UserLevelResult {
+  level: UserLevel;
+  userPubkey: string | null;
+  userPubkeyHex: string | null;
+  error?: string;
+}
+
+/**
+ * Check if a user can write to default relays by creating and verifying a proof event
+ * SECURITY: This creates the proof event client-side, but verification is done server-side
+ */
+export async function checkRelayWriteAccess(
+  userPubkeyHex: string
+): Promise<{ hasAccess: boolean; error?: string }> {
+  if (!isNIP07Available()) {
+    return { hasAccess: false, error: 'NIP-07 extension not available' };
+  }
+
+  try {
+    // Create a proof event (kind 1 text note)
+    const proofEventTemplate = createProofEvent(
+      userPubkeyHex,
+      `gitrepublic-write-proof-${Date.now()}`
+    );
+
+    // Sign the event with NIP-07
+    const signedEvent = await signEventWithNIP07(proofEventTemplate);
+
+    // Verify server-side via API endpoint (secure)
+    const response = await fetch('/api/user/level', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json'
+      },
+      body: JSON.stringify({
+        proofEvent: signedEvent,
+        userPubkeyHex
+      })
+    });
+
+    if (!response.ok) {
+      const errorData = await response.json().catch(() => ({ error: 'Unknown error' }));
+      return {
+        hasAccess: false,
+        error: errorData.error || `Server error: ${response.status}`
+      };
+    }
+
+    const result = await response.json();
+    
+    return {
+      hasAccess: result.level === 'unlimited',
+      error: result.error
+    };
+  } catch (error) {
+    return {
+      hasAccess: false,
+      error: error instanceof Error ? error.message : 'Unknown error checking relay write access'
+    };
+  }
+}
+
+/**
+ * Determine user level based on authentication and relay write access
+ * This is the main function to call to get user level
+ */
+export async function determineUserLevel(
+  userPubkey: string | null,
+  userPubkeyHex: string | null
+): Promise<UserLevelResult> {
+  // Not logged in
+  if (!userPubkey || !userPubkeyHex) {
+    return {
+      level: 'strictly_rate_limited',
+      userPubkey: null,
+      userPubkeyHex: null
+    };
+  }
+
+  // Check if user has write access to default relays
+  const writeAccess = await checkRelayWriteAccess(userPubkeyHex);
+  
+  if (writeAccess.hasAccess) {
+    return {
+      level: 'unlimited',
+      userPubkey,
+      userPubkeyHex
+    };
+  }
+
+  // Logged in but no write access
+  return {
+    level: 'rate_limited',
+    userPubkey,
+    userPubkeyHex,
+    error: writeAccess.error
+  };
+}
+
+/**
+ * Helper to decode npub to hex if needed
+ */
+export function decodePubkey(pubkey: string): string | null {
+  try {
+    const decoded = nip19.decode(pubkey);
+    if (decoded.type === 'npub') {
+      return decoded.data as string;
+    }
+    return pubkey; // Assume it's already hex
+  } catch {
+    return pubkey; // Assume it's already hex
+  }
+}
diff --git a/src/lib/services/security/rate-limiter.ts b/src/lib/services/security/rate-limiter.ts
index afcecb7..552bbfb 100644
--- a/src/lib/services/security/rate-limiter.ts
+++ b/src/lib/services/security/rate-limiter.ts
@@ -66,14 +66,22 @@ export class RateLimiter {
 
   /**
    * Get rate limit configuration for operation type
+   * @param type - Operation type
+   * @param isAnonymous - Whether the user is anonymous (stricter limits)
    */
-  private getLimitForType(type: string): number {
-    const envKey = `RATE_LIMIT_${type.toUpperCase()}_MAX`;
+  private getLimitForType(type: string, isAnonymous: boolean = false): number {
+    // Anonymous users get stricter limits (50% of authenticated limits)
+    const anonymousMultiplier = isAnonymous ? 0.5 : 1.0;
+    
+    const envKey = isAnonymous 
+      ? `RATE_LIMIT_${type.toUpperCase()}_ANON_MAX`
+      : `RATE_LIMIT_${type.toUpperCase()}_MAX`;
+    
     const defaultLimits: Record<string, number> = {
-      git: 60,      // Git operations: 60/min
-      api: 120,     // API requests: 120/min
-      file: 30,     // File operations: 30/min
-      search: 20    // Search requests: 20/min
+      git: 60,      // Git operations: 60/min (authenticated), 30/min (anonymous)
+      api: 120,     // API requests: 120/min (authenticated), 60/min (anonymous)
+      file: 30,     // File operations: 30/min (authenticated), 15/min (anonymous)
+      search: 20    // Search requests: 20/min (authenticated), 10/min (anonymous)
     };
 
     const envValue = process.env[envKey];
@@ -81,14 +89,18 @@ export class RateLimiter {
       return parseInt(envValue, 10);
     }
 
-    return defaultLimits[type] || 60;
+    const baseLimit = defaultLimits[type] || 60;
+    return Math.floor(baseLimit * anonymousMultiplier);
   }
 
   /**
    * Check rate limit for a specific operation type
+   * @param type - Operation type
+   * @param identifier - User identifier (pubkey or IP)
+   * @param isAnonymous - Whether the user is anonymous (applies stricter limits)
    */
-  check(type: string, identifier: string): { allowed: boolean; remaining: number; resetAt: number } {
-    const maxRequests = this.getLimitForType(type);
+  check(type: string, identifier: string, isAnonymous: boolean = false): { allowed: boolean; remaining: number; resetAt: number } {
+    const maxRequests = this.getLimitForType(type, isAnonymous);
     return this.checkLimit(type, identifier, maxRequests);
   }
 
diff --git a/src/lib/services/security/user-level-cache.ts b/src/lib/services/security/user-level-cache.ts
new file mode 100644
index 0000000..317f87d
--- /dev/null
+++ b/src/lib/services/security/user-level-cache.ts
@@ -0,0 +1,121 @@
+/**
+ * Cache for user access levels
+ * Prevents users from losing access when relays are temporarily down
+ * 
+ * SECURITY:
+ * - Only caches successful verifications. Failed verifications are not cached.
+ * - Cache is keyed by pubkey, so only the user with that pubkey can use it
+ * - Users must still provide a valid proof event signed with their private key
+ * - Cache expires after 24 hours, requiring re-verification
+ * - If relays are down and no cache exists, access is denied (security-first)
+ */
+
+interface CachedUserLevel {
+  level: 'unlimited' | 'rate_limited';
+  userPubkeyHex: string;
+  cachedAt: number;
+  expiresAt: number;
+}
+
+// In-memory cache (in production, consider Redis for distributed systems)
+const userLevelCache = new Map<string, CachedUserLevel>();
+
+// Cache duration: 24 hours (users keep access even if relays are down)
+const CACHE_DURATION_MS = 24 * 60 * 60 * 1000;
+
+// Cleanup interval: remove expired entries every hour
+const CLEANUP_INTERVAL_MS = 60 * 60 * 1000;
+
+let cleanupInterval: NodeJS.Timeout | null = null;
+
+/**
+ * Start cleanup interval if not already running
+ */
+function startCleanup(): void {
+  if (cleanupInterval) return;
+  
+  cleanupInterval = setInterval(() => {
+    const now = Date.now();
+    for (const [key, entry] of userLevelCache.entries()) {
+      if (entry.expiresAt < now) {
+        userLevelCache.delete(key);
+      }
+    }
+  }, CLEANUP_INTERVAL_MS);
+}
+
+/**
+ * Get cached user level if it exists and is still valid
+ */
+export function getCachedUserLevel(userPubkeyHex: string): CachedUserLevel | null {
+  startCleanup();
+  
+  const cached = userLevelCache.get(userPubkeyHex);
+  if (!cached) {
+    return null;
+  }
+  
+  // Check if cache is still valid
+  const now = Date.now();
+  if (cached.expiresAt < now) {
+    userLevelCache.delete(userPubkeyHex);
+    return null;
+  }
+  
+  return cached;
+}
+
+/**
+ * Cache a successful user level verification
+ * Only caches successful verifications (unlimited or rate_limited)
+ * Does not cache failures (strictly_rate_limited)
+ */
+export function cacheUserLevel(
+  userPubkeyHex: string,
+  level: 'unlimited' | 'rate_limited'
+): void {
+  startCleanup();
+  
+  const now = Date.now();
+  const cached: CachedUserLevel = {
+    level,
+    userPubkeyHex,
+    cachedAt: now,
+    expiresAt: now + CACHE_DURATION_MS
+  };
+  
+  userLevelCache.set(userPubkeyHex, cached);
+}
+
+/**
+ * Clear cached user level (e.g., on logout or when access is revoked)
+ */
+export function clearCachedUserLevel(userPubkeyHex: string): void {
+  userLevelCache.delete(userPubkeyHex);
+}
+
+/**
+ * Get cache statistics (for monitoring)
+ */
+export function getCacheStats(): {
+  size: number;
+  entries: Array<{ userPubkeyHex: string; level: string; expiresAt: number }>;
+} {
+  const entries = Array.from(userLevelCache.entries()).map(([key, value]) => ({
+    userPubkeyHex: key,
+    level: value.level,
+    expiresAt: value.expiresAt
+  }));
+  
+  return {
+    size: userLevelCache.size,
+    entries
+  };
+}
+
+/**
+ * Clear all cached entries (useful for testing or manual resets)
+ */
+export function clearAllCache(): void {
+  userLevelCache.clear();
+}
diff --git a/src/lib/stores/user-store.ts b/src/lib/stores/user-store.ts
new file mode 100644
index 0000000..0bab24e
--- /dev/null
+++ b/src/lib/stores/user-store.ts
@@ -0,0 +1,53 @@
+/**
+ * User store for managing user state and access level across the application
+ */
+
+import { writable } from 'svelte/store';
+import type { UserLevel } from '../services/nostr/user-level-service.js';
+
+export interface UserState {
+  userPubkey: string | null;
+  userPubkeyHex: string | null;
+  userLevel: UserLevel;
+  checkingLevel: boolean;
+  error: string | null;
+}
+
+const initialState: UserState = {
+  userPubkey: null,
+  userPubkeyHex: null,
+  userLevel: 'strictly_rate_limited',
+  checkingLevel: false,
+  error: null
+};
+
+function createUserStore() {
+  const { subscribe, set, update } = writable<UserState>(initialState);
+
+  return {
+    subscribe,
+    set,
+    update,
+    reset: () => set(initialState),
+    setChecking: (checking: boolean) => {
+      update(state => ({ ...state, checkingLevel: checking }));
+    },
+    setUser: (
+      userPubkey: string | null,
+      userPubkeyHex: string | null,
+      userLevel: UserLevel,
+      error: string | null = null
+    ) => {
+      update(state => ({
+        ...state,
+        userPubkey,
+        userPubkeyHex,
+        userLevel,
+        checkingLevel: false,
+        error
+      }));
+    }
+  };
+}
+
+export const userStore = createUserStore();
diff --git a/src/lib/utils/input-validation.ts b/src/lib/utils/input-validation.ts
new file mode 100644
index 0000000..188047a
--- /dev/null
+++ b/src/lib/utils/input-validation.ts
@@ -0,0 +1,193 @@
+/**
+ * Input validation utilities for security
+ * Prevents injection attacks, path traversal, and other security issues
+ */
+
+/**
+ * Validate and sanitize repository name
+ * Repository names should be alphanumeric with hyphens and underscores
+ */
+export function validateRepoName(name: string): { valid: boolean; error?: string; sanitized?: string } {
+  if (!name || typeof name !== 'string') {
+    return { valid: false, error: 'Repository name is required' };
+  }
+
+  // Remove leading/trailing whitespace
+  const trimmed = name.trim();
+
+  if (trimmed.length === 0) {
+    return { valid: false, error: 'Repository name cannot be empty' };
+  }
+
+  if (trimmed.length > 100) {
+    return { valid: false, error: 'Repository name must be 100 characters or less' };
+  }
+
+  // Allow alphanumeric, hyphens, underscores, and dots
+  // But not starting with dot or containing consecutive dots
+  if (!/^[a-zA-Z0-9][a-zA-Z0-9._-]*[a-zA-Z0-9]$|^[a-zA-Z0-9]$/.test(trimmed)) {
+    return {
+      valid: false,
+      error: 'Repository name must contain only alphanumeric characters, hyphens, underscores, and dots. Cannot start or end with a dot.'
+    };
+  }
+
+  // Prevent path traversal attempts
+  if (trimmed.includes('..') || trimmed.includes('/') || trimmed.includes('\\')) {
+    return { valid: false, error: 'Repository name cannot contain path separators' };
+  }
+
+  return { valid: true, sanitized: trimmed };
+}
+
+/**
+ * Validate and sanitize file path
+ * Prevents path traversal attacks
+ */
+export function validateFilePath(path: string): { valid: boolean; error?: string; sanitized?: string } {
+  if (!path || typeof path !== 'string') {
+    return { valid: false, error: 'File path is required' };
+  }
+
+  // Remove leading/trailing whitespace and slashes
+  const trimmed = path.trim().replace(/^\/+|\/+$/g, '');
+
+  if (trimmed.length === 0) {
+    return { valid: false, error: 'File path cannot be empty' };
+  }
+
+  // Prevent path traversal
+  if (trimmed.includes('..')) {
+    return { valid: false, error: 'Path traversal not allowed' };
+  }
+
+  // Prevent absolute paths
+  if (trimmed.startsWith('/') || trimmed.match(/^[a-zA-Z]:/)) {
+    return { valid: false, error: 'Absolute paths not allowed' };
+  }
+
+  // Prevent null bytes
+  if (trimmed.includes('\0')) {
+    return { valid: false, error: 'Null bytes not allowed in paths' };
+  }
+
+  // Normalize path separators
+  const normalized = trimmed.replace(/\\/g, '/');
+
+  return { valid: true, sanitized: normalized };
+}
+
+/**
+ * Validate pubkey format (hex, 64 characters)
+ */
+export function validatePubkey(pubkey: string): { valid: boolean; error?: string } {
+  if (!pubkey || typeof pubkey !== 'string') {
+    return { valid: false, error: 'Pubkey is required' };
+  }
+
+  // Hex format, 64 characters
+  if (!/^[0-9a-f]{64}$/i.test(pubkey)) {
+    return { valid: false, error: 'Invalid pubkey format. Must be 64-character hex string.' };
+  }
+
+  return { valid: true };
+}
+
+/**
+ * Validate npub format (bech32 encoded)
+ */
+export function validateNpub(npub: string): { valid: boolean; error?: string } {
+  if (!npub || typeof npub !== 'string') {
+    return { valid: false, error: 'Npub is required' };
+  }
+
+  // Basic npub format check (starts with npub, bech32 encoded)
+  if (!/^npub1[ac-hj-np-z02-9]{58}$/.test(npub)) {
+    return { valid: false, error: 'Invalid npub format' };
+  }
+
+  return { valid: true };
+}
+
+/**
+ * Sanitize string input to prevent XSS
+ * Removes potentially dangerous characters
+ */
+export function sanitizeString(input: string, maxLength: number = 10000): string {
+  if (typeof input !== 'string') {
+    return '';
+  }
+
+  // Truncate to max length
+  let sanitized = input.slice(0, maxLength);
+
+  // Remove null bytes
+  sanitized = sanitized.replace(/\0/g, '');
+
+  // Remove control characters except newlines and tabs
+  sanitized = sanitized.replace(/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/g, '');
+
+  return sanitized;
+}
+
+/**
+ * Validate commit message
+ */
+export function validateCommitMessage(message: string): { valid: boolean; error?: string; sanitized?: string } {
+  if (!message || typeof message !== 'string') {
+    return { valid: false, error: 'Commit message is required' };
+  }
+
+  const trimmed = message.trim();
+
+  if (trimmed.length === 0) {
+    return { valid: false, error: 'Commit message cannot be empty' };
+  }
+
+  if (trimmed.length > 10000) {
+    return { valid: false, error: 'Commit message must be 10000 characters or less' };
+  }
+
+  // Sanitize but allow newlines
+  const sanitized = sanitizeString(trimmed, 10000);
+
+  return { valid: true, sanitized };
+}
+
+/**
+ * Validate branch name
+ */
+export function validateBranchName(branch: string): { valid: boolean; error?: string; sanitized?: string } {
+  if (!branch || typeof branch !== 'string') {
+    return { valid: false, error: 'Branch name is required' };
+  }
+
+  const trimmed = branch.trim();
+
+  if (trimmed.length === 0) {
+    return { valid: false, error: 'Branch name cannot be empty' };
+  }
+
+  if (trimmed.length > 255) {
+    return { valid: false, error: 'Branch name must be 255 characters or less' };
+  }
+
+  // Git branch name rules
+  // Cannot contain .., cannot end with ., cannot contain spaces
+  if (trimmed.includes('..') || trimmed.endsWith('.') || /\s/.test(trimmed)) {
+    return { valid: false, error: 'Invalid branch name format' };
+  }
+
+  // Prevent path traversal
+  if (trimmed.includes('/') && trimmed !== 'HEAD') {
+    // Allow forward slashes for branch paths, but validate
+    const parts = trimmed.split('/');
+    for (const part of parts) {
+      if (part === '' || part === '.' || part === '..') {
+        return { valid: false, error: 'Invalid branch name format' };
+      }
+    }
+  }
+
+  return { valid: true, sanitized: trimmed };
+}
diff --git a/src/routes/+layout.svelte b/src/routes/+layout.svelte
index b501857..2c05431 100644
--- a/src/routes/+layout.svelte
+++ b/src/routes/+layout.svelte
@@ -1,11 +1,24 @@
 <script lang="ts">
   import '../app.css';
   import { onMount, setContext } from 'svelte';
+  import { page } from '$app/stores';
+  import { goto } from '$app/navigation';
   import Footer from '$lib/components/Footer.svelte';
   import NavBar from '$lib/components/NavBar.svelte';
+  import type { Snippet } from 'svelte';
+  import { getPublicKeyWithNIP07, isNIP07Available } from '$lib/services/nostr/nip07-signer.js';
+  import { determineUserLevel, decodePubkey } from '$lib/services/nostr/user-level-service.js';
+  import { userStore } from '$lib/stores/user-store.js';
+  import { isSessionExpired, updateActivity, clearActivity } from '$lib/services/activity-tracker.js';
+
+  // Accept children as a snippet prop (Svelte 5)
+  let { children }: { children: Snippet } = $props();
 
   // Theme management - default to dark
   let theme: 'light' | 'dark' = 'dark';
+  
+  // User level checking state
+  let checkingUserLevel = $state(false);
 
   onMount(() => {
     // Check for saved theme preference or default to dark
@@ -27,7 +40,94 @@
         }
       });
     }
+    
+    // Check for session expiry (24 hours)
+    if (isSessionExpired()) {
+      // Session expired - logout user
+      userStore.reset();
+      clearActivity();
+      console.log('Session expired after 24 hours of inactivity');
+    } else {
+      // Update activity on mount
+      updateActivity();
+    }
+    
+    // Check user level if not on splash page
+    // Only check if user store is not already initialized with a logged-in user
+    if ($page.url.pathname !== '/') {
+      const currentState = $userStore;
+      // Only check if we don't have a user or if user level is strictly_rate_limited
+      if (!currentState.userPubkey || currentState.userLevel === 'strictly_rate_limited') {
+        checkUserLevel();
+      }
+    }
+    
+    // Set up periodic session expiry check (every 5 minutes)
+    const expiryCheckInterval = setInterval(() => {
+      if (isSessionExpired()) {
+        userStore.reset();
+        clearActivity();
+        console.log('Session expired after 24 hours of inactivity');
+        // Optionally redirect to home page
+        if ($page.url.pathname !== '/') {
+          goto('/');
+        }
+      }
+    }, 5 * 60 * 1000); // Check every 5 minutes
+    
+    return () => {
+      clearInterval(expiryCheckInterval);
+    };
   });
+  
+  async function checkUserLevel() {
+    // Skip if already checking or if user store is already set
+    const currentState = $userStore;
+    if (checkingUserLevel || (currentState.userPubkey && currentState.userLevel !== 'strictly_rate_limited')) {
+      return;
+    }
+    
+    checkingUserLevel = true;
+    userStore.setChecking(true);
+    
+    try {
+      let userPubkey: string | null = null;
+      let userPubkeyHex: string | null = null;
+      
+      // Try to get user pubkey if NIP-07 is available
+      if (isNIP07Available()) {
+        try {
+          userPubkey = await getPublicKeyWithNIP07();
+          userPubkeyHex = decodePubkey(userPubkey);
+        } catch (err) {
+          console.warn('Failed to get user pubkey:', err);
+        }
+      }
+      
+      // Determine user level
+      const levelResult = await determineUserLevel(userPubkey, userPubkeyHex);
+      
+      // Update user store
+      userStore.setUser(
+        levelResult.userPubkey,
+        levelResult.userPubkeyHex,
+        levelResult.level,
+        levelResult.error || null
+      );
+      
+      // Update activity if user is logged in
+      if (levelResult.userPubkey) {
+        updateActivity();
+      }
+    } catch (err) {
+      console.error('Failed to check user level:', err);
+      // Set to strictly rate limited on error
+      userStore.setUser(null, null, 'strictly_rate_limited', 'Failed to check user level');
+    } finally {
+      checkingUserLevel = false;
+      userStore.setChecking(false);
+    }
+  }
 
   function applyTheme() {
     if (theme === 'dark') {
@@ -48,10 +148,75 @@
     get theme() { return { value: theme }; },
     toggleTheme
   });
+
+  // Hide nav bar and footer on splash page (root path)
+  const isSplashPage = $derived($page.url.pathname === '/');
+  
+  // Subscribe to user store
+  const userState = $derived($userStore);
 </script>
 
-<NavBar />
+{#if !isSplashPage}
+  <NavBar />
+{/if}
 
-<slot />
+{#if !isSplashPage && checkingUserLevel}
+  <div class="user-level-check">
+    <div class="check-message">
+      <p>Checking user access level...</p>
+      <div class="spinner"></div>
+    </div>
+  </div>
+{:else}
+  {@render children()}
+{/if}
 
-<Footer />
+{#if !isSplashPage}
+  <Footer />
+{/if}
+
+<style>
+  .user-level-check {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    min-height: 50vh;
+    padding: 2rem;
+  }
+  
+  .check-message {
+    text-align: center;
+  }
+  
+  .check-message p {
+    margin-bottom: 1rem;
+    color: var(--text-primary, #1a1a1a);
+    font-size: 1.1rem;
+  }
+  
+  .spinner {
+    border: 3px solid var(--bg-secondary, #e8e8e8);
+    border-top: 3px solid var(--accent, #007bff);
+    border-radius: 50%;
+    width: 40px;
+    height: 40px;
+    animation: spin 1s linear infinite;
+    margin: 0 auto;
+  }
+  
+  @keyframes spin {
+    0% { transform: rotate(0deg); }
+    100% { transform: rotate(360deg); }
+  }
+  
+  @media (prefers-color-scheme: dark) {
+    .check-message p {
+      color: var(--text-primary, #f5f5f5);
+    }
+    
+    .spinner {
+      border-color: var(--bg-secondary, #2d2d2d);
+      border-top-color: var(--accent, #007bff);
+    }
+  }
+</style>
diff --git a/src/routes/+page.svelte b/src/routes/+page.svelte
index 5f52ead..9167d61 100644
--- a/src/routes/+page.svelte
+++ b/src/routes/+page.svelte
@@ -4,13 +4,28 @@
   import { page } from '$app/stores';
   import { getPublicKeyWithNIP07, isNIP07Available } from '../lib/services/nostr/nip07-signer.js';
   import { nip19 } from 'nostr-tools';
+  import { determineUserLevel, decodePubkey } from '../lib/services/nostr/user-level-service.js';
+  import { userStore } from '../lib/stores/user-store.js';
+  import { updateActivity } from '../lib/services/activity-tracker.js';
 
   let userPubkey = $state<string | null>(null);
   let userPubkeyHex = $state<string | null>(null);
   let checkingAuth = $state(true);
-
-  onMount(async () => {
-    await checkAuth();
+  let checkingLevel = $state(false);
+  let levelMessage = $state<string | null>(null);
+
+  onMount(() => {
+    // Prevent body scroll when splash page is shown
+    document.body.style.overflow = 'hidden';
+    
+    // Check auth asynchronously
+    checkAuth();
+    
+    // Return cleanup function
+    return () => {
+      // Re-enable scrolling when component is destroyed
+      document.body.style.overflow = '';
+    };
   });
 
   async function checkAuth() {
@@ -37,13 +52,48 @@
   async function handleLogin() {
     if (isNIP07Available()) {
       try {
+        checkingLevel = true;
+        levelMessage = 'Checking authentication...';
+        
         await checkAuth();
-        if (userPubkey) {
+        
+        if (userPubkey && userPubkeyHex) {
+          levelMessage = 'Verifying relay write access...';
+          
+          // Determine user level (checks relay write access)
+          const levelResult = await determineUserLevel(userPubkey, userPubkeyHex);
+          
+          // Update user store
+          userStore.setUser(
+            levelResult.userPubkey,
+            levelResult.userPubkeyHex,
+            levelResult.level,
+            levelResult.error || null
+          );
+          
+          // Update activity tracking on successful login
+          updateActivity();
+          
+          checkingLevel = false;
+          levelMessage = null;
+          
+          // Show appropriate message based on level
+          if (levelResult.level === 'unlimited') {
+            levelMessage = 'Unlimited access granted!';
+          } else if (levelResult.level === 'rate_limited') {
+            levelMessage = 'Logged in with rate-limited access.';
+          }
+          
           // User is logged in, go to repos page
           goto('/repos');
+        } else {
+          checkingLevel = false;
+          levelMessage = null;
         }
       } catch (err) {
         console.error('Login failed:', err);
+        checkingLevel = false;
+        levelMessage = null;
         alert('Failed to login. Please make sure you have a Nostr extension installed (like nos2x or Alby).');
       }
     } else {
@@ -101,8 +151,11 @@
     </div>
 
     <div class="splash-message">
-      {#if checkingAuth}
-        <p class="splash-text">Checking authentication...</p>
+      {#if checkingAuth || checkingLevel}
+        <p class="splash-text">{levelMessage || 'Checking authentication...'}</p>
+        {#if checkingLevel && levelMessage}
+          <p class="splash-text-secondary">This may take a few seconds...</p>
+        {/if}
       {:else if userPubkey}
         <p class="splash-text">Welcome back! You're logged in.</p>
         <p class="splash-text-secondary">You can now access all repositories you have permission to view.</p>
@@ -114,7 +167,7 @@
     </div>
 
     <div class="splash-actions">
-      {#if checkingAuth}
+      {#if checkingAuth || checkingLevel}
         <div class="splash-loading">Loading...</div>
       {:else if userPubkey}
         <button class="splash-button splash-button-primary" onclick={() => goto('/repos')}>
@@ -135,13 +188,21 @@
 
 <style>
   .splash-container {
-    min-height: 100vh;
+    position: fixed;
+    top: 0;
+    left: 0;
+    right: 0;
+    bottom: 0;
+    width: 100vw;
+    height: 100vh;
     display: flex;
     align-items: center;
     justify-content: center;
-    position: relative;
+    z-index: 9999;
     overflow: hidden;
     background: linear-gradient(135deg, var(--bg-primary, #f5f5f5) 0%, var(--bg-secondary, #e8e8e8) 100%);
+    /* Ensure it covers everything and blocks interaction */
+    pointer-events: auto;
   }
 
   .splash-background {
diff --git a/src/routes/api/user/level/+server.ts b/src/routes/api/user/level/+server.ts
new file mode 100644
index 0000000..e979f2e
--- /dev/null
+++ b/src/routes/api/user/level/+server.ts
@@ -0,0 +1,193 @@
+/**
+ * API endpoint for verifying user level (relay write access)
+ * This must be done server-side for security - client-side checks can be bypassed
+ * 
+ * User only needs to be able to write to ONE of the default relays, not all.
+ * This is a trust mechanism - users who can write to trusted default relays
+ * get unlimited access, limiting access to trusted npubs.
+ */
+
+import { json, error } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { verifyRelayWriteProof } from '$lib/services/nostr/relay-write-proof.js';
+import { DEFAULT_NOSTR_RELAYS } from '$lib/config.js';
+import { auditLogger } from '$lib/services/security/audit-logger.js';
+import { getCachedUserLevel, cacheUserLevel } from '$lib/services/security/user-level-cache.js';
+import { extractRequestContext } from '$lib/utils/api-context.js';
+import { sanitizeError } from '$lib/utils/security.js';
+import { verifyEvent } from 'nostr-tools';
+import logger from '$lib/services/logger.js';
+
+export const POST: RequestHandler = async (event) => {
+  const requestContext = extractRequestContext(event);
+  const clientIp = requestContext.clientIp || 'unknown';
+  
+  try {
+    const body = await event.request.json();
+    const { proofEvent, userPubkeyHex } = body;
+
+    // Validate input
+    if (!proofEvent || !userPubkeyHex) {
+      auditLogger.logAuth(
+        null,
+        clientIp,
+        'NIP-98',
+        'failure',
+        'Missing proof event or user pubkey'
+      );
+      return error(400, 'Missing required fields: proofEvent and userPubkeyHex');
+    }
+
+    // Validate pubkey format (should be hex, 64 characters)
+    if (typeof userPubkeyHex !== 'string' || !/^[0-9a-f]{64}$/i.test(userPubkeyHex)) {
+      auditLogger.logAuth(
+        null,
+        clientIp,
+        'NIP-98',
+        'failure',
+        'Invalid pubkey format'
+      );
+      return error(400, 'Invalid pubkey format');
+    }
+
+    // Validate proof event structure
+    if (!proofEvent.kind || !proofEvent.pubkey || !proofEvent.created_at || !proofEvent.id) {
+      auditLogger.logAuth(
+        userPubkeyHex,
+        clientIp,
+        'NIP-98',
+        'failure',
+        'Invalid proof event structure'
+      );
+      return error(400, 'Invalid proof event structure');
+    }
+
+    // Validate proof event signature first (even if using cache, user must prove they have private key)
+    if (!verifyEvent(proofEvent)) {
+      auditLogger.logAuth(
+        userPubkeyHex,
+        clientIp,
+        'NIP-98',
+        'failure',
+        'Invalid proof event signature'
+      );
+      return error(400, 'Invalid proof event signature');
+    }
+
+    // Verify pubkey matches
+    if (proofEvent.pubkey !== userPubkeyHex) {
+      auditLogger.logAuth(
+        userPubkeyHex,
+        clientIp,
+        'NIP-98',
+        'failure',
+        'Proof event pubkey does not match user pubkey'
+      );
+      return error(400, 'Proof event pubkey does not match user pubkey');
+    }
+
+    // Check cache (if relays are down, use cached value)
+    // But user must still provide valid proof event signed with their private key
+    const cached = getCachedUserLevel(userPubkeyHex);
+    if (cached) {
+      logger.info({ userPubkeyHex, level: cached.level }, '[API] Using cached user level (proof event signature validated)');
+      return json({
+        level: cached.level,
+        userPubkeyHex,
+        verified: true,
+        cached: true
+      });
+    }
+
+    // Verify relay write proof server-side
+    const verification = await verifyRelayWriteProof(
+      proofEvent,
+      userPubkeyHex,
+      DEFAULT_NOSTR_RELAYS
+    );
+
+    // If relays are down, check cache again (might have been cached from previous request)
+    if (verification.relayDown) {
+      const cachedOnRelayDown = getCachedUserLevel(userPubkeyHex);
+      if (cachedOnRelayDown) {
+        logger.info({ userPubkeyHex, level: cachedOnRelayDown.level }, '[API] Relays down, using cached user level');
+        auditLogger.logAuth(
+          userPubkeyHex,
+          clientIp,
+          'NIP-98',
+          'success',
+          'Relays down, using cached access level'
+        );
+        return json({
+          level: cachedOnRelayDown.level,
+          userPubkeyHex,
+          verified: true,
+          cached: true,
+          relayDown: true
+        });
+      }
+      
+      // No cache available and relays are down - return error
+      auditLogger.logAuth(
+        userPubkeyHex,
+        clientIp,
+        'NIP-98',
+        'failure',
+        'Relays unavailable and no cached access level'
+      );
+      return error(503, 'Relays are temporarily unavailable. Please try again later.');
+    }
+
+    if (verification.valid) {
+      // User has write access - unlimited level
+      // Cache the successful verification
+      cacheUserLevel(userPubkeyHex, 'unlimited');
+      
+      auditLogger.logAuth(
+        userPubkeyHex,
+        clientIp,
+        'NIP-98',
+        'success',
+        'Relay write access verified'
+      );
+      
+      return json({
+        level: 'unlimited',
+        userPubkeyHex,
+        verified: true
+      });
+    } else {
+      // User is logged in but no write access - rate limited
+      // Cache this level too (so they don't lose access if relays go down)
+      cacheUserLevel(userPubkeyHex, 'rate_limited');
+      
+      auditLogger.logAuth(
+        userPubkeyHex,
+        clientIp,
+        'NIP-98',
+        'success',
+        'Authenticated but no relay write access'
+      );
+      
+      return json({
+        level: 'rate_limited',
+        userPubkeyHex,
+        verified: true,
+        error: verification.error
+      });
+    }
+  } catch (err) {
+    const errorMessage = err instanceof Error ? err.message : String(err);
+    logger.error({ error: err, clientIp }, '[API] Error verifying user level');
+    
+    auditLogger.logAuth(
+      null,
+      clientIp,
+      'NIP-98',
+      'failure',
+      sanitizeError(errorMessage)
+    );
+    
+    return error(500, 'Failed to verify user level');
+  }
+};
diff --git a/src/routes/repos/[npub]/[repo]/+page.svelte b/src/routes/repos/[npub]/[repo]/+page.svelte
index 60bf7a9..35bf82c 100644
--- a/src/routes/repos/[npub]/[repo]/+page.svelte
+++ b/src/routes/repos/[npub]/[repo]/+page.svelte
@@ -708,10 +708,6 @@
     }
   }
 
-  function logout() {
-    userPubkey = null;
-    isMaintainer = false;
-  }
 
   async function checkMaintainerStatus() {
     if (repoNotFound || !userPubkey) {