diff --git a/cli.py b/cli.py
index f9d0abae02445..559094a527d89 100644
--- a/cli.py
+++ b/cli.py
@@ -2114,8 +2114,9 @@ def _run_state_db_auto_maintenance(session_db) -> None:
     :func:`hermes_cli.config.load_config` (the authoritative loader that
     deep-merges DEFAULT_CONFIG, so unmigrated configs still get default
     values). Honours ``auto_prune`` / ``retention_days`` /
-    ``vacuum_after_prune`` / ``min_interval_hours``, and delegates to the
-    DB. Never raises — maintenance must never block interactive startup.
+    ``vacuum_after_prune`` / ``min_vacuum_interval_days`` /
+    ``min_interval_hours``, and delegates to the DB. Never raises —
+    maintenance must never block interactive startup.
     """
     if session_db is None:
         return
@@ -2164,6 +2165,7 @@ def _run_state_db_auto_maintenance(session_db) -> None:
         session_db.maybe_auto_prune_and_vacuum(
             retention_days=int(cfg.get("retention_days", 90)),
             min_interval_hours=int(cfg.get("min_interval_hours", 24)),
+            min_vacuum_interval_days=int(cfg.get("min_vacuum_interval_days", 30)),
             vacuum=bool(cfg.get("vacuum_after_prune", True)),
             sessions_dir=_hermes_home_maint / "sessions",
         )
diff --git a/gateway/run.py b/gateway/run.py
index 905a7763c5f9d..532ff9c2a942b 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -6001,6 +6001,9 @@ def __init__(self, config: Optional[GatewayConfig] = None):
                     self._session_db._db.maybe_auto_prune_and_vacuum(
                         retention_days=int(_sess_cfg.get("retention_days", 90)),
                         min_interval_hours=int(_sess_cfg.get("min_interval_hours", 24)),
+                        min_vacuum_interval_days=int(
+                            _sess_cfg.get("min_vacuum_interval_days", 30)
+                        ),
                         vacuum=bool(_sess_cfg.get("vacuum_after_prune", True)),
                         sessions_dir=self.config.sessions_dir,
                     )
diff --git a/hermes_cli/config_defaults.py b/hermes_cli/config_defaults.py
index 80adf77ff45c1..4545575db26cd 100644
--- a/hermes_cli/config_defaults.py
+++ b/hermes_cli/config_defaults.py
@@ -2625,6 +2625,9 @@
         # 100MB, so it only runs at startup, and only when prune deleted
         # ≥1 session.
         "vacuum_after_prune": True,
+        # Minimum days between successful VACUUM rewrites. Pruning can still
+        # run on its normal cadence while SQLite reuses the freed pages.
+        "min_vacuum_interval_days": 30,
         # Minimum hours between auto-maintenance runs (avoids repeating
         # the sweep on every CLI invocation).  Tracked via state_meta in
         # state.db itself, so it's shared across all processes.
diff --git a/hermes_state.py b/hermes_state.py
index 4f7b6453461a9..90a8b43c9515f 100644
--- a/hermes_state.py
+++ b/hermes_state.py
@@ -8529,12 +8529,16 @@ def maybe_auto_prune_and_vacuum(
         min_interval_hours: int = 24,
         vacuum: bool = True,
         sessions_dir: Optional[Path] = None,
+        min_vacuum_interval_days: int = 30,
     ) -> Dict[str, Any]:
         """Idempotent auto-maintenance: prune inactive sessions + optional VACUUM.
 
         Records the last run timestamp in state_meta so subsequent calls
-        within ``min_interval_hours`` no-op. Designed to be called once at
-        startup from long-lived entrypoints (CLI, gateway, cron scheduler).
+        within ``min_interval_hours`` no-op. VACUUM has its own, typically
+        longer, throttle controlled by ``min_vacuum_interval_days`` so routine
+        pruning does not repeatedly rewrite the database. Designed to be
+        called once at startup from long-lived entrypoints (CLI, gateway, cron
+        scheduler).
 
         When *sessions_dir* is provided, on-disk transcript files
         (``.json`` / ``.jsonl`` / ``request_dump_*``) for pruned sessions
@@ -8569,12 +8573,25 @@ def maybe_auto_prune_and_vacuum(
             )
             result["pruned"] = pruned
 
-            # Only VACUUM if we actually freed rows — VACUUM on a tight DB
-            # is wasted I/O. Threshold keeps small DBs from paying the cost.
-            if vacuum and pruned > 0:
+            # Only VACUUM if we actually freed rows, and no more often than
+            # once every min_vacuum_interval_days -- a large prune (e.g. the
+            # first one to cross retention_days on a DB with tens of
+            # thousands of rows) can free enough pages that pruned > 0 fires
+            # on every subsequent startup even though a VACUUM already ran
+            # recently. VACUUM on this DB's size (FTS5 shadow tables) is not
+            # cheap -- it holds an exclusive lock for the full rewrite.
+            last_vacuum_raw = self.get_meta("last_vacuum")
+            vacuum_due = True
+            if last_vacuum_raw:
+                try:
+                    vacuum_due = (now - float(last_vacuum_raw)) >= min_vacuum_interval_days * 86400
+                except (TypeError, ValueError):
+                    vacuum_due = True
+            if vacuum and pruned > 0 and vacuum_due:
                 try:
                     self.vacuum()
                     result["vacuumed"] = True
+                    self.set_meta("last_vacuum", str(now))
                 except Exception as exc:
                     logger.warning("state.db VACUUM failed: %s", exc)
 
diff --git a/tests/test_hermes_state.py b/tests/test_hermes_state.py
index dd54682ef5d26..4c27c3adac3b2 100644
--- a/tests/test_hermes_state.py
+++ b/tests/test_hermes_state.py
@@ -1744,6 +1744,67 @@ def test_vacuum_runs_without_error(self, db):
         # Should not raise, even though there's nothing significant to reclaim.
         db.vacuum()
 
+    def test_auto_maintenance_records_successful_vacuum(self, db, monkeypatch):
+        monkeypatch.setattr(db, "prune_sessions", lambda **_kwargs: 3)
+        vacuum_calls = []
+        monkeypatch.setattr(db, "vacuum", lambda: vacuum_calls.append(True))
+
+        result = db.maybe_auto_prune_and_vacuum(min_interval_hours=0)
+
+        assert result["vacuumed"] is True
+        assert vacuum_calls == [True]
+        assert db.get_meta("last_vacuum") is not None
+
+    def test_auto_maintenance_skips_recent_vacuum(self, db, monkeypatch):
+        monkeypatch.setattr(db, "prune_sessions", lambda **_kwargs: 3)
+        db.set_meta("last_vacuum", str(time.time()))
+        vacuum_calls = []
+        monkeypatch.setattr(db, "vacuum", lambda: vacuum_calls.append(True))
+
+        result = db.maybe_auto_prune_and_vacuum(
+            min_interval_hours=0,
+            min_vacuum_interval_days=30,
+        )
+
+        assert result["vacuumed"] is False
+        assert vacuum_calls == []
+
+    def test_auto_maintenance_retries_after_vacuum_interval(self, db, monkeypatch):
+        monkeypatch.setattr(db, "prune_sessions", lambda **_kwargs: 3)
+        db.set_meta("last_vacuum", str(time.time() - 31 * 86400))
+        vacuum_calls = []
+        monkeypatch.setattr(db, "vacuum", lambda: vacuum_calls.append(True))
+
+        result = db.maybe_auto_prune_and_vacuum(
+            min_interval_hours=0,
+            min_vacuum_interval_days=30,
+        )
+
+        assert result["vacuumed"] is True
+        assert vacuum_calls == [True]
+
+    def test_auto_maintenance_retries_after_failed_vacuum(self, db, monkeypatch):
+        monkeypatch.setattr(db, "prune_sessions", lambda **_kwargs: 3)
+        vacuum_calls = []
+
+        def fail_first_vacuum():
+            vacuum_calls.append(True)
+            if len(vacuum_calls) == 1:
+                raise RuntimeError("vacuum failed")
+
+        monkeypatch.setattr(db, "vacuum", fail_first_vacuum)
+
+        first = db.maybe_auto_prune_and_vacuum(min_interval_hours=0)
+
+        assert first["vacuumed"] is False
+        assert db.get_meta("last_vacuum") is None
+
+        second = db.maybe_auto_prune_and_vacuum(min_interval_hours=0)
+
+        assert second["vacuumed"] is True
+        assert vacuum_calls == [True, True]
+        assert db.get_meta("last_vacuum") is not None
+
 
 class TestOptimizeFts:
     def test_optimize_returns_index_count(self, db):
diff --git a/tests/test_session_vacuum_config.py b/tests/test_session_vacuum_config.py
new file mode 100644
index 0000000000000..d231996b59887
--- /dev/null
+++ b/tests/test_session_vacuum_config.py
@@ -0,0 +1,41 @@
+from pathlib import Path
+from unittest.mock import MagicMock
+
+
+def test_default_config_exposes_vacuum_interval():
+    from hermes_cli.config import DEFAULT_CONFIG
+
+    assert DEFAULT_CONFIG["sessions"]["min_vacuum_interval_days"] == 30
+
+
+def test_cli_auto_maintenance_forwards_vacuum_interval(monkeypatch, tmp_path: Path):
+    import cli
+    import hermes_cli.config
+    import hermes_constants
+
+    session_db = MagicMock()
+    session_db.get_meta.return_value = "already-done"
+    monkeypatch.setattr(
+        hermes_cli.config,
+        "load_config",
+        lambda: {
+            "sessions": {
+                "auto_prune": True,
+                "retention_days": 90,
+                "vacuum_after_prune": True,
+                "min_interval_hours": 24,
+                "min_vacuum_interval_days": 17,
+            }
+        },
+    )
+    monkeypatch.setattr(hermes_constants, "get_hermes_home", lambda: tmp_path)
+
+    cli._run_state_db_auto_maintenance(session_db)
+
+    session_db.maybe_auto_prune_and_vacuum.assert_called_once_with(
+        retention_days=90,
+        min_interval_hours=24,
+        min_vacuum_interval_days=17,
+        vacuum=True,
+        sessions_dir=tmp_path / "sessions",
+    )
diff --git a/website/docs/user-guide/sessions.md b/website/docs/user-guide/sessions.md
index 71b53a23101a6..91a63a2bed4f2 100644
--- a/website/docs/user-guide/sessions.md
+++ b/website/docs/user-guide/sessions.md
@@ -714,7 +714,7 @@ Key tables in `state.db`:
 - Gateway sessions auto-reset based on the configured reset policy
 - Before reset, the agent saves memories and skills from the expiring session
 - Opt-in auto-pruning: when `sessions.auto_prune` is `true`, ended sessions inactive for `sessions.retention_days` (default 90) are pruned at CLI/gateway startup
-- After a prune that actually removed rows, `state.db` is `VACUUM`ed to reclaim disk space (SQLite does not shrink the file on plain DELETE)
+- After a prune that actually removed rows, `state.db` is `VACUUM`ed to reclaim disk space when at least `sessions.min_vacuum_interval_days` (default 30) have elapsed since the last successful `VACUUM` (SQLite does not shrink the file on plain DELETE)
 - Pruning runs at most once per `sessions.min_interval_hours` (default 24); the last-run timestamp is tracked inside `state.db` itself so it's shared across every Hermes process in the same `HERMES_HOME`
 
 Default is **off** — session history is valuable for `session_search` recall, and silently deleting it could surprise users. Enable in `~/.hermes/config.yaml`:
@@ -724,6 +724,7 @@ sessions:
   auto_prune: true          # opt in — default is false
   retention_days: 90        # keep ended sessions active within this window
   vacuum_after_prune: true  # reclaim disk space after a pruning sweep
+  min_vacuum_interval_days: 30 # don't rewrite the DB more often than this
   min_interval_hours: 24    # don't re-run the sweep more often than this
 ```
 
diff --git a/website/i18n/zh-Hans/docusaurus-plugin-content-docs/current/user-guide/sessions.md b/website/i18n/zh-Hans/docusaurus-plugin-content-docs/current/user-guide/sessions.md
index 3bc6692de231d..19c7b710ebf7d 100644
--- a/website/i18n/zh-Hans/docusaurus-plugin-content-docs/current/user-guide/sessions.md
+++ b/website/i18n/zh-Hans/docusaurus-plugin-content-docs/current/user-guide/sessions.md
@@ -579,7 +579,7 @@ state.db 后可安全删除。
 - Gateway session 根据配置的重置策略自动重置
 - 重置前，agent 保存即将过期 session 中的记忆和技能
 - 可选自动清理：当 `sessions.auto_prune` 为 `true` 时，在 CLI/gateway 启动时清理早于 `sessions.retention_days`（默认 90）天的已结束 session
-- 实际删除了行的清理操作完成后，`state.db` 会执行 `VACUUM` 以回收磁盘空间（SQLite 在普通 DELETE 后不会缩小文件）
+- 实际删除了行的清理操作完成后，如果距离上次成功执行 `VACUUM` 已达到 `sessions.min_vacuum_interval_days`（默认 30）天，`state.db` 会执行 `VACUUM` 以回收磁盘空间（SQLite 在普通 DELETE 后不会缩小文件）
 - 清理最多每 `sessions.min_interval_hours`（默认 24）小时运行一次；上次运行时间戳记录在 `state.db` 内部，因此在同一 `HERMES_HOME` 下的所有 Hermes 进程间共享
 
 默认为**关闭**——session 历史对 `session_search` 召回很有价值，静默删除可能会让用户感到意外。在 `~/.hermes/config.yaml` 中启用：
@@ -589,6 +589,7 @@ sessions:
   auto_prune: true          # 选择启用——默认为 false
   retention_days: 90        # 保留已结束 session 的天数
   vacuum_after_prune: true  # 清理后回收磁盘空间
+  min_vacuum_interval_days: 30 # 数据库重写的最短间隔天数
   min_interval_hours: 24    # 清理间隔不短于此值
 ```