diff --git a/server/index.mjs b/server/index.mjs
index 75b5ae8..9dd0b40 100644
--- a/server/index.mjs
+++ b/server/index.mjs
@@ -578,6 +578,9 @@ r.get('/oauth/google/yt-channels', authMiddlewareCookieAware, oauthLimiter, asyn
     const out = { error: error?.message || 'yt_channels_failed' };
     if (error?.detail) out.detail = error.detail;
     if (error?.hint) out.hint = error.hint;
+    try {
+      console.warn(`[oauth] yt-channels échec user=${req.user?.id} code=${out.error} detail=${String(error?.detail || '').slice(0, 300)}`);
+    } catch {}
     return res.status(error?.status || 502).json(out);
   }
 });
diff --git a/server/oauth.mjs b/server/oauth.mjs
index bef093d..388e461 100644
--- a/server/oauth.mjs
+++ b/server/oauth.mjs
@@ -642,13 +642,29 @@ async function getAuthedInnertube(conn, { pageId } = {}) {
   return innertube;
 }
 
-/** Détail d'erreur YouTube exposable (clé API masquée, 300 car. max, sans token). */
+/** Détail d'erreur YouTube exposable (clé/token masqués, 500 car. max). */
 function libErrorDetail(e) {
   try {
-    return String(e?.message || e || '')
+    // youtubei.js met le corps de réponse dans e.info (JSON d'erreur Google).
+    let raw = '';
+    if (e?.info && typeof e.info === 'object') {
+      try { raw = JSON.stringify(e.info); } catch { raw = String(e.info); }
+    } else if (typeof e?.info === 'string') {
+      raw = e.info;
+    }
+    const combined = [raw, String(e?.message || '')].filter(Boolean).join(' | ');
+    // Extrait le motif Google s'il existe : {"error":{"errors":[{"reason":"X"}]}}.
+    let reason = '';
+    try {
+      const parsed = JSON.parse(raw);
+      const first = parsed?.error?.errors?.[0];
+      if (first?.reason) reason = `reason=${first.reason}; msg=${String(first.message || parsed?.error?.message || '').slice(0, 200)}`;
+    } catch {}
+    const out = (reason || combined)
       .replace(/key=[^&\s]*/gi, 'key=[redacted]')
       .replace(/Bearer\s+[A-Za-z0-9._~-]+/gi, 'Bearer [redacted]')
-      .slice(0, 300) || undefined;
+      .slice(0, 500);
+    return out || undefined;
   } catch { return undefined; }
 }