diff --git a/tests/tools/test_terminal_disk_usage.py b/tests/tools/test_terminal_disk_usage.py
new file mode 100644
index 000000000..72dcc608a
--- /dev/null
+++ b/tests/tools/test_terminal_disk_usage.py
@@ -0,0 +1,62 @@
+"""Tests for get_active_environments_info disk usage calculation."""
+
+from pathlib import Path
+from unittest.mock import patch, MagicMock
+
+import pytest
+
+from tools.terminal_tool import get_active_environments_info
+
+# 1 MiB of data so the rounded MB value is clearly distinguishable
+_1MB = b"x" * (1024 * 1024)
+
+
+@pytest.fixture()
+def fake_scratch(tmp_path):
+    """Create fake hermes scratch directories with known sizes."""
+    # Task A: 1 MiB
+    task_a_dir = tmp_path / "hermes-sandbox-aaaaaaaa"
+    task_a_dir.mkdir()
+    (task_a_dir / "data.bin").write_bytes(_1MB)
+
+    # Task B: 1 MiB
+    task_b_dir = tmp_path / "hermes-sandbox-bbbbbbbb"
+    task_b_dir.mkdir()
+    (task_b_dir / "data.bin").write_bytes(_1MB)
+
+    return tmp_path
+
+
+class TestDiskUsageGlob:
+    def test_only_counts_matching_task_dirs(self, fake_scratch):
+        """Each task should only count its own directories, not all hermes-* dirs."""
+        fake_envs = {
+            "aaaaaaaa-1111-2222-3333-444444444444": MagicMock(),
+        }
+
+        with (
+            patch("tools.terminal_tool._active_environments", fake_envs),
+            patch("tools.terminal_tool._get_scratch_dir", return_value=fake_scratch),
+        ):
+            info = get_active_environments_info()
+
+        # Task A only: ~1.0 MB. With the bug (hardcoded hermes-*),
+        # it would also count task B -> ~2.0 MB.
+        assert info["total_disk_usage_mb"] == pytest.approx(1.0, abs=0.1)
+
+    def test_multiple_tasks_no_double_counting(self, fake_scratch):
+        """With 2 active tasks, each should count only its own dirs."""
+        fake_envs = {
+            "aaaaaaaa-1111-2222-3333-444444444444": MagicMock(),
+            "bbbbbbbb-5555-6666-7777-888888888888": MagicMock(),
+        }
+
+        with (
+            patch("tools.terminal_tool._active_environments", fake_envs),
+            patch("tools.terminal_tool._get_scratch_dir", return_value=fake_scratch),
+        ):
+            info = get_active_environments_info()
+
+        # Should be ~2.0 MB total (1 MB per task).
+        # With the bug, each task globs everything -> ~4.0 MB.
+        assert info["total_disk_usage_mb"] == pytest.approx(2.0, abs=0.1)
diff --git a/tools/terminal_tool.py b/tools/terminal_tool.py
index 4f8971985..2f8ba8174 100644
--- a/tools/terminal_tool.py
+++ b/tools/terminal_tool.py
@@ -645,7 +645,7 @@ def get_active_environments_info() -> Dict[str, Any]:
         scratch_dir = _get_scratch_dir()
         for pattern in [f"hermes-*{task_id[:8]}*"]:
             import glob
-            for path in glob.glob(str(scratch_dir / "hermes-*")):
+            for path in glob.glob(str(scratch_dir / pattern)):
                 try:
                     size = sum(f.stat().st_size for f in Path(path).rglob('*') if f.is_file())
                     total_size += size