feat(cloud): harden multi-tenant runtime resources

tests/unit_tests/platform/test_matrix_limits.py

@@ -0,0 +1,21 @@
+from __future__ import annotations
+
+import pytest
+
+from langbot.pkg.platform.sources import matrix
+
+
+def test_matrix_base64_decode_is_bounded(monkeypatch):
+    monkeypatch.setattr(matrix, '_MAX_MATRIX_MEDIA_BYTES', 4)
+
+    with pytest.raises(ValueError, match='exceeds'):
+        matrix._decode_matrix_base64_limited('A' * 12)
+
+
+def test_matrix_local_file_read_is_bounded(tmp_path, monkeypatch):
+    monkeypatch.setattr(matrix, '_MAX_MATRIX_MEDIA_BYTES', 4)
+    path = tmp_path / 'large.bin'
+    path.write_bytes(b'12345')
+
+    with pytest.raises(ValueError, match='exceeds'):
+        matrix._read_matrix_file_limited(str(path))