fix(frontend): EEG default path points at fixture (HF container has no data/raw/eeg.fif)

src/frontend/app.py

@@ -1197,7 +1197,15 @@ def _render_eeg_tab() -> None:
         "ICA decomposition, and extracts per-band PSD + statistical features "
         "across fixed-duration epochs.",
     )
-    eeg_in = st.text_input("Input FIF/EDF path", "data/raw/eeg.fif", key="eeg_in")
+    eeg_in = st.text_input(
+        "Input FIF/EDF path",
+        "tests/fixtures/eeg_sample.fif",
+        key="eeg_in",
+        help=(
+            "Defaults to the bundled EEG fixture so the demo runs out of "
+            "the box. Replace with your own .fif/.edf path on a real run."
+        ),
+    )
     eeg_out = st.text_input(
         "Output Parquet path",
         "data/processed/eeg_features.parquet",

tests/frontend/test_app_defaults.py

@@ -0,0 +1,44 @@
+"""Defaults shown in the Streamlit UI must point at files that actually exist
+in the deployed image. The HF container does not seed `data/raw/eeg.fif`
+unless we explicitly do so in the Dockerfile, so the EEG tab default must
+either be a fixture file (always present) or be seeded server-side.
+"""
+from __future__ import annotations
+
+from pathlib import Path
+import re
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+APP_PY = REPO_ROOT / "src" / "frontend" / "app.py"
+
+
+def _eeg_default_path() -> str:
+    """Extract the default value passed to the EEG `input_path` text_input.
+
+    The line looks like:
+        eeg_in = st.text_input("Input FIF/EDF path", "tests/fixtures/eeg_sample.fif", key="eeg_in")
+    We pull the second positional arg (the default value).
+    """
+    text = APP_PY.read_text()
+    match = re.search(
+        r'st\.text_input\(\s*"Input FIF/EDF path"\s*,\s*"([^"]+)"',
+        text,
+    )
+    assert match is not None, "could not locate EEG text_input default in app.py"
+    return match.group(1)
+
+
+def test_eeg_default_path_points_at_existing_file() -> None:
+    default = _eeg_default_path()
+    abs_path = REPO_ROOT / default
+    assert abs_path.exists(), (
+        f"EEG default path {default!r} resolves to {abs_path} which does "
+        f"not exist on disk. The HF container does not seed this path "
+        f"either, so users get an HTTP 404 the moment they click Run."
+    )
+
+
+def test_eeg_default_path_is_eeg_sample_fixture() -> None:
+    """Pin the exact fix: default must be the canonical fixture so both
+    local dev and the deployed image agree."""
+    assert _eeg_default_path() == "tests/fixtures/eeg_sample.fif"