diff --git a/hermes_cli/kanban.py b/hermes_cli/kanban.py
index 11b00da59ac..a26517dbae0 100644
--- a/hermes_cli/kanban.py
+++ b/hermes_cli/kanban.py
@@ -652,6 +652,16 @@ def kanban_command(args: argparse.Namespace) -> int:
     # keeps the patch small and inherits the exact same resolution the
     # dispatcher uses for workers — consistency is a feature here.
     board_override = getattr(args, "board", None)
+    prev_board_env = os.environ.get("HERMES_KANBAN_BOARD")
+    restore_board_env = False
+
+    def _restore_board_env() -> None:
+        if not restore_board_env:
+            return
+        if prev_board_env is None:
+            os.environ.pop("HERMES_KANBAN_BOARD", None)
+        else:
+            os.environ["HERMES_KANBAN_BOARD"] = prev_board_env
     if board_override:
         try:
             normed = kb._normalize_board_slug(board_override)
@@ -671,12 +681,16 @@ def kanban_command(args: argparse.Namespace) -> int:
             )
             return 1
         os.environ["HERMES_KANBAN_BOARD"] = normed
+        restore_board_env = True
 
     # Boards management doesn't touch the DB at all — dispatch early so
     # fresh installs that haven't initialized any DB can still use
     # `hermes kanban boards create …`.
     if action == "boards":
-        return _dispatch_boards(args)
+        try:
+            return _dispatch_boards(args)
+        finally:
+            _restore_board_env()
 
     # Auto-initialize the DB before dispatching any subcommand. init_db
     # is idempotent, so running it every invocation is cheap (one
@@ -689,6 +703,7 @@ def kanban_command(args: argparse.Namespace) -> int:
         kb.init_db()
     except Exception as exc:
         print(f"kanban: could not initialize database: {exc}", file=sys.stderr)
+        _restore_board_env()
         return 1
 
     handlers = {
@@ -730,12 +745,16 @@ def kanban_command(args: argparse.Namespace) -> int:
     handler = handlers.get(action)
     if not handler:
         print(f"kanban: unknown action {action!r}", file=sys.stderr)
+        _restore_board_env()
         return 2
     try:
         return int(handler(args) or 0)
     except (ValueError, RuntimeError) as exc:
         print(f"kanban: {exc}", file=sys.stderr)
+        _restore_board_env()
         return 1
+    finally:
+        _restore_board_env()
 
 
 # ---------------------------------------------------------------------------
diff --git a/tests/hermes_cli/test_kanban_cli.py b/tests/hermes_cli/test_kanban_cli.py
index 3d88b6212cb..241016a25d8 100644
--- a/tests/hermes_cli/test_kanban_cli.py
+++ b/tests/hermes_cli/test_kanban_cli.py
@@ -392,3 +392,13 @@ def test_run_slash_missing_required_arg_friendly_error(kanban_home):
     out = kc.run_slash("show")
     assert "/kanban show" in out
     assert "task_id" in out
+
+
+def test_run_slash_board_override_restores_prior_env(kanban_home, monkeypatch):
+    kb.create_board("alpha")
+    kb.create_board("beta")
+    monkeypatch.setenv("HERMES_KANBAN_BOARD", "beta")
+
+    kc.run_slash("--board alpha list")
+
+    assert os.environ.get("HERMES_KANBAN_BOARD") == "beta"