diff --git a/backend/src/lib/handlers/cards.ts b/backend/src/lib/handlers/cards.ts
index 40e60a2..957bb1b 100644
--- a/backend/src/lib/handlers/cards.ts
+++ b/backend/src/lib/handlers/cards.ts
@@ -1,60 +1,91 @@
 import { route, HandlerContext, HttpError } from '@/lib/router';
 import { getDb } from '@/lib/db';
 
+function log(method: string, path: string, steamId: string, msg: string) {
+  console.log(`[Cards] ${method} ${path} steam=${steamId} — ${msg}`);
+}
+
 route('player/:steamId/card-levels', ['GET'], (ctx: HandlerContext) => {
+  const steamId = ctx.params.steamId;
+  log('GET', 'card-levels', steamId, 'loading card levels');
   const db = getDb();
-  const row = db.prepare('SELECT card_levels FROM card_levels WHERE steam_id = ?').get(ctx.params.steamId) as any;
-  return { card_levels: row ? JSON.parse(row.card_levels) : {} };
+  const row = db.prepare('SELECT card_levels FROM card_levels WHERE steam_id = ?').get(steamId) as any;
+  const result = { card_levels: row ? JSON.parse(row.card_levels) : {} };
+  log('GET', 'card-levels', steamId, `returned ${Object.keys(result.card_levels).length} card levels`);
+  return result;
 });
 
 route('player/:steamId/card-levels', ['PUT'], (ctx: HandlerContext) => {
+  const steamId = ctx.params.steamId;
   const { card_levels } = ctx.body as any;
+  const keys = card_levels ? Object.keys(card_levels) : [];
+  log('PUT', 'card-levels', steamId, `saving ${keys.length} card levels: ${JSON.stringify(keys.slice(0, 10))}${keys.length > 10 ? '...' : ''}`);
   const db = getDb();
   db.prepare(`
     INSERT INTO card_levels (steam_id, card_levels, updated_at) VALUES (?, ?, datetime('now'))
     ON CONFLICT(steam_id) DO UPDATE SET card_levels = ?, updated_at = datetime('now')
-  `).run(ctx.params.steamId, JSON.stringify(card_levels || {}), JSON.stringify(card_levels || {}));
+  `).run(steamId, JSON.stringify(card_levels || {}), JSON.stringify(card_levels || {}));
+  log('PUT', 'card-levels', steamId, 'saved successfully');
   return { success: true };
 });
 
 route('player/:steamId/decks', ['GET'], (ctx: HandlerContext) => {
+  const steamId = ctx.params.steamId;
   const db = getDb();
-  const rows = db.prepare('SELECT * FROM decks WHERE steam_id = ? ORDER BY deck_index').all(ctx.params.steamId) as any[];
+  const rows = db.prepare('SELECT * FROM decks WHERE steam_id = ? ORDER BY deck_index').all(steamId) as any[];
   const decks: Record<string, any> = {};
   for (const r of rows) {
     decks[r.deck_index] = { name: r.name, cards: JSON.parse(r.cards || '[]') };
   }
+  log('GET', 'decks', steamId, `returned ${Object.keys(decks).length} decks: indices=[${Object.keys(decks).join(',')}]`);
   return { decks };
 });
 
 route('player/:steamId/decks/:index', ['GET'], (ctx: HandlerContext) => {
+  const steamId = ctx.params.steamId;
+  const idx = ctx.params.index;
   const db = getDb();
-  const deck = db.prepare('SELECT * FROM decks WHERE steam_id = ? AND deck_index = ?').get(ctx.params.steamId, parseInt(ctx.params.index)) as any;
-  if (!deck) return { name: 'New Deck', cards: [] };
-  return { ...deck, cards: JSON.parse(deck.cards || '[]') };
+  const deck = db.prepare('SELECT * FROM decks WHERE steam_id = ? AND deck_index = ?').get(steamId, parseInt(idx)) as any;
+  if (!deck) {
+    log('GET', `decks/${idx}`, steamId, 'not found, returning empty deck');
+    return { name: 'New Deck', cards: [] };
+  }
+  const cards = JSON.parse(deck.cards || '[]');
+  log('GET', `decks/${idx}`, steamId, `found deck="${deck.name}" with ${cards.length} cards`);
+  return { ...deck, cards };
 });
 
 route('player/:steamId/decks/:index', ['PUT'], (ctx: HandlerContext) => {
+  const steamId = ctx.params.steamId;
+  const idx = ctx.params.index;
   const { name, cards } = ctx.body as any;
+  const cardCount = Array.isArray(cards) ? cards.length : 0;
+  log('PUT', `decks/${idx}`, steamId, `saving deck="${name || 'unnamed'}" with ${cardCount} cards: ${JSON.stringify(cards?.slice(0, 10))}${cardCount > 10 ? '...' : ''}`);
   const db = getDb();
-  const idx = parseInt(ctx.params.index);
   db.prepare(`
     INSERT INTO decks (steam_id, deck_index, name, cards, updated_at) VALUES (?, ?, ?, ?, datetime('now'))
     ON CONFLICT(steam_id, deck_index) DO UPDATE SET name = ?, cards = ?, updated_at = datetime('now')
-  `).run(ctx.params.steamId, idx, name || 'My Deck', JSON.stringify(cards || []), name || 'My Deck', JSON.stringify(cards || []));
+  `).run(steamId, parseInt(idx), name || 'My Deck', JSON.stringify(cards || []), name || 'My Deck', JSON.stringify(cards || []));
+  log('PUT', `decks/${idx}`, steamId, 'saved successfully');
   return { success: true };
 });
 
 route('player/:steamId/decks/:index', ['DELETE'], (ctx: HandlerContext) => {
+  const steamId = ctx.params.steamId;
+  const idx = ctx.params.index;
+  log('DELETE', `decks/${idx}`, steamId, 'deleting deck');
   const db = getDb();
-  const idx = parseInt(ctx.params.index);
-  db.prepare('DELETE FROM decks WHERE steam_id = ? AND deck_index = ?').run(ctx.params.steamId, idx);
+  db.prepare('DELETE FROM decks WHERE steam_id = ? AND deck_index = ?').run(steamId, parseInt(idx));
+  log('DELETE', `decks/${idx}`, steamId, 'deleted successfully');
   return { success: true };
 });
 
 route('player/:steamId/decks', ['PUT'], (ctx: HandlerContext) => {
+  const steamId = ctx.params.steamId;
   const { decks: decksToSave } = ctx.body as any;
   if (!decksToSave) throw new HttpError(400, 'decks required');
+  const indices = Object.keys(decksToSave);
+  log('PUT', 'decks (batch)', steamId, `saving ${indices.length} decks: indices=[${indices.join(',')}]`);
   const db = getDb();
   const upsert = db.prepare(`
     INSERT INTO decks (steam_id, deck_index, name, cards, updated_at) VALUES (?, ?, ?, ?, datetime('now'))
@@ -63,9 +94,13 @@ route('player/:steamId/decks', ['PUT'], (ctx: HandlerContext) => {
   const tx = db.transaction(() => {
     for (const [indexStr, deck] of Object.entries(decksToSave)) {
       const d = deck as any;
-      upsert.run(ctx.params.steamId, parseInt(indexStr), d.name || 'My Deck', JSON.stringify(d.cards || []), d.name || 'My Deck', JSON.stringify(d.cards || []));
+      const cards = d.cards || [];
+      const cardCount = Array.isArray(cards) ? cards.length : 0;
+      log('PUT', `decks/${indexStr} (batch)`, steamId, `deck="${d.name || 'unnamed'}" with ${cardCount} cards`);
+      upsert.run(steamId, parseInt(indexStr), d.name || 'My Deck', JSON.stringify(cards), d.name || 'My Deck', JSON.stringify(cards));
     }
   });
   tx();
+  log('PUT', 'decks (batch)', steamId, `batch save of ${indices.length} decks completed`);
   return { success: true };
 });