diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..5a34bea
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,4 @@
+[tool.pytest.ini_options]
+pythonpath = [
+  "."
+]
diff --git a/scripts/tests/test_distill.py b/scripts/tests/test_distill.py
index 7f3a3d1..ecb52c8 100644
--- a/scripts/tests/test_distill.py
+++ b/scripts/tests/test_distill.py
@@ -5,7 +5,7 @@
 # Add the scripts directory to sys.path to allow importing distill
 sys.path.append(str(pathlib.Path(__file__).parent.parent))
 
-from distill import clean_signal
+from distill import clean_signal, is_durable_signal
 
 @pytest.mark.parametrize("input_line, expected", [
     # Basic cases
@@ -49,3 +49,44 @@
 ])
 def test_clean_signal(input_line, expected):
     assert clean_signal(input_line) == expected
+
+
+@pytest.mark.parametrize(
+    "line,expected",
+    [
+        # Empty
+        ("", False),
+
+        # Length < 12
+        ("short", False),
+        ("12345678901", False),
+
+        # Starts with # or > [!
+        ("# A heading that is long enough", False),
+        ("> [!info] Some info", False),
+        ("> [!warning] warning", False),
+
+        # NOISE_RE matches
+        ("ok          ", False),
+        ("okay.", False),
+        ("yes!", False),
+        ("understood!!!", False),
+
+        # SHELL_NOISE_RE matches
+        ("$ python3 script.py", False),
+        ("Running test: xyz", False),
+        ("Traceback (most recent call last):", False),
+        ("Exception: Something went wrong", False),
+        ("FAIL: test_something", False),
+        ("error: must read the pane correctly", False),
+        ("[tmux-bridge error]", False),
+
+        # Valid durable signals (Happy paths)
+        ("123456789012", True),
+        ("We decided to keep distill.py dry-run and let Claude own writes.", True),
+        ("This is a valid durable signal that should be captured.", True),
+        ("Next action: implement tests for distill.py.", True),
+    ]
+)
+def test_is_durable_signal(line, expected):
+    assert is_durable_signal(line) is expected