diff --git a/hermes_cli/sessions_cmd.py b/hermes_cli/sessions_cmd.py
index 714201b624..16c50dcdc4 100644
--- a/hermes_cli/sessions_cmd.py
+++ b/hermes_cli/sessions_cmd.py
@@ -942,16 +942,14 @@ def cmd_sessions(args, sessions_parser=None):
             filters["archived"] = False
 
         candidates = db.list_prune_candidates(**filters)
-        skipped_open = (
-            db.count_open_prune_matches(**filters) if action == "prune" else 0
-        )
+        skipped_open = db.count_open_prune_matches(**filters)
         if skipped_open:
             suffix = "" if skipped_open == 1 else "s"
             print(
                 f"Note: {skipped_open} open session{suffix} also match these "
-                "filters but will be skipped because prune only deletes ended "
-                "sessions. Use `hermes sessions delete <id>` to remove one "
-                "explicitly."
+                f"filters but will be skipped because bulk {action} only "
+                "affects ended sessions. Use `hermes sessions delete <id>` "
+                "to remove one explicitly."
             )
         verb = "Delete" if action == "prune" else "Archive"
         if not candidates:
diff --git a/hermes_state.py b/hermes_state.py
index 188edd33a4..84a61fe3ee 100644
--- a/hermes_state.py
+++ b/hermes_state.py
@@ -11657,6 +11657,20 @@ class SessionDB(SessionSearchMixin, SessionSchemaMixin, SessionPortabilityMixin)
             clauses.append("s.archived = 0")
         return " AND ".join(clauses), params
 
+    @staticmethod
+    def _apply_prune_age_filter(
+        older_than_days: Optional[float], filters: Dict[str, Any]
+    ) -> None:
+        """Translate the legacy age window into the shared activity filter."""
+        if (
+            filters.get("last_active_before") is None
+            and filters.get("started_before") is None
+            and older_than_days is not None
+        ):
+            filters["last_active_before"] = time.time() - (
+                older_than_days * 86400
+            )
+
     def list_prune_candidates(
         self,
         older_than_days: Optional[float] = None,
@@ -11674,14 +11688,7 @@ class SessionDB(SessionSearchMixin, SessionSchemaMixin, SessionPortabilityMixin)
         threshold: it uses the latest message timestamp, falling back to
         ``started_at`` for sessions without messages.
         """
-        if (
-            filters.get("last_active_before") is None
-            and filters.get("started_before") is None
-            and older_than_days is not None
-        ):
-            filters["last_active_before"] = time.time() - (
-                older_than_days * 86400
-            )
+        self._apply_prune_age_filter(older_than_days, filters)
         where, params = self._prune_filter_where(source=source, **filters)
         with self._lock:
             cursor = self._conn.execute(
@@ -11711,14 +11718,7 @@ class SessionDB(SessionSearchMixin, SessionSchemaMixin, SessionPortabilityMixin)
         why an otherwise matching session was skipped without making live
         sessions eligible for destructive pruning.
         """
-        if (
-            filters.get("last_active_before") is None
-            and filters.get("started_before") is None
-            and older_than_days is not None
-        ):
-            filters["last_active_before"] = time.time() - (
-                older_than_days * 86400
-            )
+        self._apply_prune_age_filter(older_than_days, filters)
         where, params = self._prune_filter_where(source=source, **filters)
         ended_guard = "s.ended_at IS NOT NULL"
         if not where.startswith(ended_guard):
diff --git a/tests/hermes_cli/test_sessions_delete.py b/tests/hermes_cli/test_sessions_delete.py
index 7650a9bbef..538f344acd 100644
--- a/tests/hermes_cli/test_sessions_delete.py
+++ b/tests/hermes_cli/test_sessions_delete.py
@@ -39,8 +39,10 @@ def test_sessions_delete_accepts_unique_id_prefix(monkeypatch, capsys):
     assert "Deleted session '20260315_092437_c9a6ff'." in output
 
 
-def _run_prune(monkeypatch, capsys, argv_tail, candidates=None, skipped_open=0):
-    """Run `hermes sessions prune <argv_tail>` against a FakeDB, capturing
+def _run_prune(
+    monkeypatch, capsys, argv_tail, candidates=None, skipped_open=0, action="prune"
+):
+    """Run `hermes sessions <action> <argv_tail>` against a FakeDB, capturing
     the filter kwargs passed to list_prune_candidates. Auto-confirms."""
     import hermes_cli.main as main_mod
     import hermes_state
@@ -81,12 +83,15 @@ def _run_prune(monkeypatch, capsys, argv_tail, candidates=None, skipped_open=0):
         def prune_sessions(self, **kwargs):
             return len(rows)
 
+        def archive_sessions(self, **kwargs):
+            return len(rows)
+
         def close(self):
             pass
 
     monkeypatch.setattr(hermes_state, "SessionDB", lambda: FakeDB())
     monkeypatch.setattr(
-        sys, "argv", ["hermes", "sessions", "prune", *argv_tail]
+        sys, "argv", ["hermes", "sessions", action, *argv_tail]
     )
     monkeypatch.setattr("builtins.input", lambda _prompt="": "y")
     main_mod.main()
@@ -124,6 +129,21 @@ def test_sessions_prune_surfaces_matching_open_sessions(monkeypatch, capsys):
     )
 
     assert "2 open sessions also match these filters" in out
-    assert "prune only deletes ended sessions" in out
+    assert "bulk prune only affects ended sessions" in out
     assert "hermes sessions delete <id>" in out
     assert "No sessions match" in out
+
+
+def test_sessions_archive_surfaces_matching_open_sessions(monkeypatch, capsys):
+    _filters, out = _run_prune(
+        monkeypatch,
+        capsys,
+        ["--source", "cron"],
+        candidates=[],
+        skipped_open=1,
+        action="archive",
+    )
+
+    assert "1 open session also match these filters" in out
+    assert "bulk archive only affects ended sessions" in out
+    assert "No sessions match" in out
diff --git a/web/src/lib/session-prune.test.ts b/web/src/lib/session-prune.test.ts
index cab7b48e84..cedb04e6bb 100644
--- a/web/src/lib/session-prune.test.ts
+++ b/web/src/lib/session-prune.test.ts
@@ -1,17 +1,15 @@
-import { describe, expect, it } from "vitest";
+import { describe, expect, it } from 'vitest'
 
-import { formatSessionPruneResult } from "./session-prune";
+import { formatSessionPruneResult } from './session-prune'
 
-describe("formatSessionPruneResult", () => {
-  it("reports open sessions skipped by the prune safety guard", () => {
+describe('formatSessionPruneResult', () => {
+  it('reports open sessions skipped by the prune safety guard', () => {
     expect(formatSessionPruneResult({ removed: 0, skipped_open: 2 })).toBe(
-      "Pruned 0 sessions. Skipped 2 open sessions; prune only removes ended sessions.",
-    );
-  });
+      'Pruned 0 sessions. Skipped 2 open sessions; prune only removes ended sessions.'
+    )
+  })
 
-  it("keeps the existing success message when nothing was skipped", () => {
-    expect(formatSessionPruneResult({ removed: 1, skipped_open: 0 })).toBe(
-      "Pruned 1 session",
-    );
-  });
-});
\ No newline at end of file
+  it('keeps the existing success message when nothing was skipped', () => {
+    expect(formatSessionPruneResult({ removed: 1, skipped_open: 0 })).toBe('Pruned 1 session')
+  })
+})
diff --git a/web/src/lib/session-prune.ts b/web/src/lib/session-prune.ts
index 0031e43f74..5d45139c37 100644
--- a/web/src/lib/session-prune.ts
+++ b/web/src/lib/session-prune.ts
@@ -1,11 +1,11 @@
 interface SessionPruneResult {
-  removed: number;
-  skipped_open: number;
+  removed: number
+  skipped_open: number
 }
 
 export function formatSessionPruneResult(result: SessionPruneResult): string {
-  const removed = `Pruned ${result.removed} session${result.removed === 1 ? "" : "s"}`;
-  if (!result.skipped_open) return removed;
+  const removed = `Pruned ${result.removed} session${result.removed === 1 ? '' : 's'}`
+  if (!result.skipped_open) return removed
 
-  return `${removed}. Skipped ${result.skipped_open} open session${result.skipped_open === 1 ? "" : "s"}; prune only removes ended sessions.`;
-}
\ No newline at end of file
+  return `${removed}. Skipped ${result.skipped_open} open session${result.skipped_open === 1 ? '' : 's'}; prune only removes ended sessions.`
+}