diff --git a/app/main.py b/app/main.py
index b7dd60f..dc24c33 100644
--- a/app/main.py
+++ b/app/main.py
@@ -106,6 +106,12 @@ def init_db():
         CREATE INDEX IF NOT EXISTS idx_at_norm ON arena_text_leaderboard(norm_name);
         CREATE INDEX IF NOT EXISTS idx_ag_norm ON arena_agent_leaderboard(norm_name);
     """)
+
+    # Миграция: текст ошибки нужен для деталей в тултипах сегментов.
+    cols = [r[1] for r in db.execute("PRAGMA table_info(checks)").fetchall()]
+    if "error" not in cols:
+        db.execute("ALTER TABLE checks ADD COLUMN error TEXT")
+
     db.commit()
     db.close()
 
@@ -354,7 +360,8 @@ def model_stats(db: sqlite3.Connection, model_id: str, hours: int = 24) -> dict:
     ).fetchone()
 
     rows = db.execute(
-        "SELECT ok FROM checks WHERE model_id=? AND checked_at > ? ORDER BY checked_at ASC",
+        "SELECT ok, latency_ms, checked_at, error FROM checks "
+        "WHERE model_id=? AND checked_at > ? ORDER BY checked_at ASC",
         (model_id, cutoff)
     ).fetchall()
 
@@ -363,7 +370,16 @@ def model_stats(db: sqlite3.Connection, model_id: str, hours: int = 24) -> dict:
     pct = round(100 * success / total) if total else None
 
     # История последних проверок (старые → новые) для сегментной витрины.
-    history = [bool(r["ok"]) for r in rows][-HISTORY_LIMIT:]
+    # Каждый элемент — детали проверки: ok, latency, время, текст ошибки.
+    history = [
+        {
+            "ok": bool(r["ok"]),
+            "latency_ms": r["latency_ms"],
+            "at": r["checked_at"],
+            "error": r["error"],
+        }
+        for r in rows[-HISTORY_LIMIT:]
+    ]
 
     return {
         "last_ok": bool(last["ok"]) if last else None,
@@ -476,6 +492,7 @@ def api_check(model_id: str):
     t0 = _t.time()
     ok = False
     latency = None
+    error = None
     try:
         body = json.dumps({
             "model": model_id,
@@ -494,15 +511,17 @@ def api_check(model_id: str):
             resp = json.loads(r.read())
             content = resp["choices"][0]["message"]["content"]
             ok = bool(content.strip())
-        latency = int((_t.time() - t0) * 1000)
     except Exception as e:
-        print(f"[check] {model_id}: {e}")
+        error = f"{type(e).__name__}: {e}"
+        print(f"[check] {model_id}: {error}")
+
+    latency = int((_t.time() - t0) * 1000)
 
     now = datetime.now(timezone.utc).isoformat()
     db = get_db()
     db.execute(
-        "INSERT INTO checks (model_id, checked_at, ok, latency_ms) VALUES (?,?,?,?)",
-        (model_id, now, int(ok), latency),
+        "INSERT INTO checks (model_id, checked_at, ok, latency_ms, error) VALUES (?,?,?,?,?)",
+        (model_id, now, int(ok), latency, error),
     )
     db.commit()
     stats = model_stats(db, model_id)
diff --git a/app/probe.py b/app/probe.py
index 9d8882d..b7f3ce2 100644
--- a/app/probe.py
+++ b/app/probe.py
@@ -19,8 +19,9 @@ TIMEOUT = int(os.environ.get("CHECK_TIMEOUT", "30"))
 CONCURRENCY = int(os.environ.get("CHECK_CONCURRENCY", "5"))
 
 
-def check_model(model_id: str) -> tuple[bool, int | None]:
+def check_model(model_id: str) -> tuple[bool, int | None, str | None]:
     t0 = time.time()
+    error = None
     try:
         body = json.dumps({
             "model": model_id,
@@ -40,10 +41,11 @@ def check_model(model_id: str) -> tuple[bool, int | None]:
             content = resp["choices"][0]["message"]["content"]
             ok = bool(content.strip())
     except Exception as e:
-        print(f"  ✗ {model_id}: {e}", file=sys.stderr)
+        error = f"{type(e).__name__}: {e}"
+        print(f"  ✗ {model_id}: {error}", file=sys.stderr)
         ok = False
-    latency = int((time.time() - t0) * 1000) if ok else None
-    return ok, latency
+    latency = int((time.time() - t0) * 1000)
+    return ok, latency, error
 
 
 def run():
@@ -56,8 +58,8 @@ def run():
     from concurrent.futures import ThreadPoolExecutor, as_completed
 
     def do(mid):
-        ok, lat = check_model(mid)
-        return mid, ok, lat
+        ok, lat, err = check_model(mid)
+        return mid, ok, lat, err
 
     db = sqlite3.connect(DB_PATH, check_same_thread=False)
     now = datetime.now(timezone.utc).isoformat()
@@ -66,10 +68,10 @@ def run():
         futs = {ex.submit(do, m): m for m in models}
         done = ok_count = 0
         for f in as_completed(futs):
-            mid, ok, lat = f.result()
+            mid, ok, lat, err = f.result()
             db.execute(
-                "INSERT INTO checks (model_id, checked_at, ok, latency_ms) VALUES (?,?,?,?)",
-                (mid, now, int(ok), lat),
+                "INSERT INTO checks (model_id, checked_at, ok, latency_ms, error) VALUES (?,?,?,?,?)",
+                (mid, now, int(ok), lat, err),
             )
             done += 1
             if ok:
diff --git a/app/static/index.html b/app/static/index.html
index 8ab1bca..6b5683c 100644
--- a/app/static/index.html
+++ b/app/static/index.html
@@ -146,6 +146,25 @@
   .uptime-seg.empty { background: transparent; border: 1px dashed var(--border); box-sizing: border-box; }
   .uptime-segs .uptime { margin-left: 6px; }
 
+  /* Тултип с деталями проверки */
+  .seg-tip {
+    position: fixed; z-index: 1000; pointer-events: none;
+    background: var(--bg2); border: 1px solid var(--border);
+    border-radius: 6px; padding: 8px 10px;
+    box-shadow: 0 6px 20px rgba(0,0,0,.45);
+    font-size: 12px; line-height: 1.45; color: var(--text);
+    max-width: 380px; white-space: pre-wrap; word-break: break-word;
+    display: none;
+  }
+  .seg-tip .tip-head { font-weight: 600; margin-bottom: 4px; }
+  .seg-tip .tip-ok   { color: var(--green); }
+  .seg-tip .tip-fail { color: var(--red); }
+  .seg-tip .tip-meta { color: var(--text2); font-size: 11px; }
+  .seg-tip .tip-err {
+    color: var(--red); font-family: Consolas, 'Fira Mono', monospace;
+    font-size: 11px; margin-top: 4px; white-space: pre-wrap;
+  }
+
   .check-btn {
     background: none; border: 1px solid var(--border); border-radius: 4px;
     color: var(--text2); padding: 3px 8px; cursor: pointer; font-size: 11px;
@@ -250,13 +269,15 @@ function uptimeCell(pct, history) {
     : (pct >= 90 ? 'uptime-high' : pct >= 70 ? 'uptime-mid' : 'uptime-low');
 
   // Сегменты: каждый — одна проверка. Слева старее, справа свежее.
-  const segs = hist.map(ok =>
-    `<span class="uptime-seg ${ok ? 'ok' : 'fail'}" title="${ok ? 'успех' : 'провал'}"></span>`
-  ).join('');
+  const segs = hist.map((h, i) => {
+    const ok = typeof h === 'boolean' ? h : h && h.ok;
+    const data = typeof h === 'boolean' ? { ok } : h;
+    return `<span class="uptime-seg ${ok ? 'ok' : 'fail'}" data-seg='${JSON.stringify(data).replace(/'/g, "&#39;")}'></span>`;
+  }).join('');
 
   const label = pct === null || pct === undefined ? '—' : `${pct}%`;
   const tip = hist.length
-    ? `title="последние ${hist.length} проверок: ${hist.filter(Boolean).length} успех"`
+    ? `title="последние ${hist.length} проверок: ${hist.filter(h => typeof h === 'boolean' ? h : h && h.ok).length} успех"`
     : '';
 
   return `<div class="uptime-segs" ${tip}>
@@ -265,6 +286,67 @@ function uptimeCell(pct, history) {
   </div>`;
 }
 
+// ─── Тултип с деталями проверки ──────────────────────────────────────────────
+let segTipEl = null;
+
+function segTip() {
+  if (!segTipEl) {
+    segTipEl = document.createElement('div');
+    segTipEl.className = 'seg-tip';
+    document.body.appendChild(segTipEl);
+  }
+  return segTipEl;
+}
+
+function fmtTime(iso) {
+  if (!iso) return '—';
+  const d = new Date(iso);
+  if (isNaN(d)) return iso;
+  return d.toLocaleString('ru', { day: '2-digit', month: '2-digit', hour: '2-digit', minute: '2-digit' });
+}
+
+function showSegTip(el) {
+  let data;
+  try { data = JSON.parse(el.dataset.seg); } catch (e) { return; }
+  const tip = segTip();
+  const ok = data.ok;
+  const lat = data.latency_ms !== null && data.latency_ms !== undefined ? `${data.latency_ms} мс` : '—';
+  tip.innerHTML = `
+    <div class="tip-head ${ok ? 'tip-ok' : 'tip-fail'}">${ok ? '✓ Успех' : '✗ Провал'}</div>
+    <div class="tip-meta">${fmtTime(data.at)} · ${lat}</div>
+    ${data.error ? `<div class="tip-err">${escapeHtml(data.error)}</div>` : ''}
+  `;
+  tip.style.display = 'block';
+  const r = el.getBoundingClientRect();
+  const tr = tip.getBoundingClientRect();
+  let left = r.left + r.width / 2 - tr.width / 2;
+  left = Math.max(8, Math.min(left, window.innerWidth - tr.width - 8));
+  let top = r.top - tr.height - 8;
+  if (top < 8) top = r.bottom + 8;
+  tip.style.left = `${left + window.scrollX}px`;
+  tip.style.top = `${top + window.scrollY}px`;
+}
+
+function hideSegTip() {
+  if (segTipEl) segTipEl.style.display = 'none';
+}
+
+function escapeHtml(s) {
+  return String(s).replace(/[&<>"']/g, c => ({
+    '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;'
+  }[c]));
+}
+
+// Делегирование: тултип на весь контейнер сегментов.
+document.addEventListener('mouseover', e => {
+  const seg = e.target.closest('.uptime-seg[data-seg]');
+  if (seg) showSegTip(seg);
+});
+document.addEventListener('mouseout', e => {
+  if (e.target.closest('.uptime-seg[data-seg]')) hideSegTip();
+});
+document.addEventListener('scroll', hideSegTip, true);
+
 function modelName(id) {
   const parts = id.split('/');
   const tail = parts[parts.length - 1];