diff --git a/src/stemforge/io_utils.py b/src/stemforge/io_utils.py
index 2be9581..9c7647b 100644
--- a/src/stemforge/io_utils.py
+++ b/src/stemforge/io_utils.py
@@ -184,7 +184,11 @@ def read_json(path: PathLike) -> Any:
 def _json_default(o: Any) -> Any:
     if isinstance(o, np.ndarray):
         return o.tolist()
-    if isinstance(o, (np.floating, np.integer)):
+    # np.generic covers EVERY numpy scalar — bool_, floating, integer — across
+    # numpy 1.x and 2.x (2.0 renamed np.bool_'s repr to numpy.bool). The A1 cymbal
+    # evidence was the first path to put an np.bool_ into a manifest, which the old
+    # (np.floating, np.integer) branch missed → write_json crashed on drum teardown.
+    if isinstance(o, np.generic):
         return o.item()
     if isinstance(o, Path):
         return str(o)
diff --git a/src/stemforge/web/assets/app.js b/src/stemforge/web/assets/app.js
index 1af154f..25506d9 100644
--- a/src/stemforge/web/assets/app.js
+++ b/src/stemforge/web/assets/app.js
@@ -186,7 +186,13 @@ function showProgress(frac, msg) {
 async function poll(jobId) {
   for (;;) {
     await new Promise((r) => setTimeout(r, 400));
-    const job = await (await fetch(`/api/job/${jobId}`)).json();
+    const res = await fetch(`/api/job/${jobId}`);
+    // A dead job id (server restarted -> in-memory job store cleared) returns 404.
+    // Stop polling instead of looping forever on the missing job.
+    if (res.status === 404) {
+      return finishError("Job not found (the server was restarted). Please re-run.");
+    }
+    const job = await res.json();
     showProgress(job.progress || 0.05, job.message);
     if (job.status === "done") return renderResults(job.result);
     if (job.status === "error") return finishError(job.error || job.message);
diff --git a/src/stemforge/webapp.py b/src/stemforge/webapp.py
index d908dc4..e9421ec 100644
--- a/src/stemforge/webapp.py
+++ b/src/stemforge/webapp.py
@@ -295,7 +295,7 @@ def _safe(path_str: str) -> Path | None:
 # --------------------------------------------------------------------------- #
 def create_app():
     from fastapi import FastAPI, File, Form, HTTPException, UploadFile
-    from fastapi.responses import FileResponse, HTMLResponse, StreamingResponse
+    from fastapi.responses import FileResponse, HTMLResponse, Response, StreamingResponse
     from fastapi.staticfiles import StaticFiles
 
     app = FastAPI(title="StemForge", docs_url=None, redoc_url=None)
@@ -319,6 +319,12 @@ async def _require_token(request, call_next):
     def index() -> str:
         return (WEB_DIR / "index.html").read_text(encoding="utf-8")
 
+    @app.get("/favicon.ico")
+    def favicon() -> Response:
+        # No icon asset is shipped; return 204 so the browser stops logging a 404
+        # on every page load (console noise, not an error).
+        return Response(status_code=204)
+
     @app.get("/api/health")
     def health() -> dict[str, Any]:
         return health_status()
diff --git a/tests/test_io.py b/tests/test_io.py
index b5e2570..d1e18ad 100644
--- a/tests/test_io.py
+++ b/tests/test_io.py
@@ -1,6 +1,8 @@
+from pathlib import Path
+
 import numpy as np
 
-from stemforge.io_utils import AudioTensor, load_audio, receipt, save_audio, slugify
+from stemforge.io_utils import AudioTensor, load_audio, read_json, receipt, save_audio, slugify, write_json
 
 
 def test_audiotensor_shapes(sine):
@@ -40,3 +42,22 @@ def test_slugify():
     assert slugify("My Song") == "My_Song"
     assert slugify("a/b\\c") == "a_b_c"
     assert slugify("") == "song"
+
+
+def test_write_json_serializes_numpy_scalars(tmp_path):
+    """A manifest can carry any numpy scalar. np.bool_ (the A1 cymbal evidence hit
+    it first) previously crashed write_json — _json_default now covers np.generic."""
+    obj = {
+        "flag": np.bool_(True),          # the case that broke drum teardown on Windows
+        "f": np.float64(1.5),
+        "i": np.int64(7),
+        "arr": np.arange(3),             # ndarray -> list
+        "path": tmp_path / "out",        # Path -> str
+    }
+    p = write_json(tmp_path / "m.json", obj)   # must not raise
+    back = read_json(p)
+    assert back["flag"] is True
+    assert back["f"] == 1.5 and isinstance(back["f"], float)
+    assert back["i"] == 7 and isinstance(back["i"], int)
+    assert back["arr"] == [0, 1, 2]
+    assert back["path"] == str(Path(tmp_path / "out"))
diff --git a/tests/test_separation_backends.py b/tests/test_separation_backends.py
index 8529625..56b6bda 100644
--- a/tests/test_separation_backends.py
+++ b/tests/test_separation_backends.py
@@ -180,7 +180,8 @@ def test_separate_uvr_maps_and_caches(fake_uvr_cli, sine):
     assert cmd[0].endswith("audio-separator")
     assert cmd[cmd.index("--model_filename") + 1] == BS_ROFORMER_MODEL
     assert cmd[cmd.index("--output_format") + 1] == "WAV"
-    assert cmd[cmd.index("--model_file_dir") + 1].endswith("models/uvr")
+    # compare path components, not a "/"-joined suffix — portable across Windows backslashes
+    assert Path(cmd[cmd.index("--model_file_dir") + 1]).parts[-2:] == ("models", "uvr")
     assert "--use_autocast" in cmd
 
     # scratch files are cleaned up after each call
diff --git a/tests/test_tempo_evidence.py b/tests/test_tempo_evidence.py
index 1de45f5..385aee9 100644
--- a/tests/test_tempo_evidence.py
+++ b/tests/test_tempo_evidence.py
@@ -8,7 +8,9 @@
 the librosa meter is flagged assumed, and both analysis and stretch record a
 shared, sanitized EngineAttempt chain.
 
-GPU-free and deterministic (beat_this is absent, so analyze uses librosa).
+GPU-free and deterministic — analyze is driven to librosa either explicitly
+(engine="librosa") or by forcing the beat_this hop to fail, so the tests do not
+depend on whether beat_this happens to be installed.
 """
 
 from __future__ import annotations
@@ -108,10 +110,15 @@ def test_beatgrid_to_dict_carries_evidence():
     assert d["bpm_candidates"] == [60.0, 120.0, 240.0]
 
 
-def test_analyze_records_fallback_chain():
-    """beat_this is absent -> analyze records a fell_through hop with a sanitized
-    reason, then librosa used."""
-    g = analyze(_two_clicks())  # default engine="beat_this" -> falls to librosa
+def test_analyze_records_fallback_chain(monkeypatch):
+    """A beat_this failure -> analyze records a fell_through hop with a sanitized
+    reason, then librosa used. Force the failure so the test is isolated from the
+    environment (beat_this may or may not be installed — it is on Windows)."""
+    def _boom(*a, **k):
+        raise ImportError("No module named 'beat_this'")
+
+    monkeypatch.setattr(analysis, "_analyze_beat_this", _boom)
+    g = analyze(_two_clicks())  # default engine="beat_this" -> forced fallback to librosa
     assert g.engine == "librosa"
     chain = g.fallback_chain
     assert [c["engine"] for c in chain] == ["beat_this", "librosa"]
diff --git a/tests/test_webapp.py b/tests/test_webapp.py
index 0959278..7c239c3 100644
--- a/tests/test_webapp.py
+++ b/tests/test_webapp.py
@@ -192,9 +192,15 @@ def test_file_route_rejects_paths_outside_output_root(client, tmp_path):
 
 
 def test_unknown_job_is_404(client):
+    # the SPA poller relies on this 404 to stop polling a dead job after a restart
     assert client.get("/api/job/deadbeef").status_code == 404
 
 
+def test_favicon_returns_204_not_404(client):
+    # a favicon route silences the per-load 404 in the local server console
+    assert client.get("/favicon.ico").status_code == 204
+
+
 # --------------------------------------------------------------------------- #
 # Match BPM (whole-file) — stretch.match_bpm_file mocked
 # --------------------------------------------------------------------------- #