diff --git a/src/backend/api/routers/measurements.py b/src/backend/api/routers/measurements.py
index 4e631b6..bb466d9 100644
--- a/src/backend/api/routers/measurements.py
+++ b/src/backend/api/routers/measurements.py
@@ -357,7 +357,8 @@ async def export_measurements_csv(
     # Rows
     for m in measurements:
         # Format decimals with configured separator
-        value_str = str(m.value).replace(".", decimal_separator)
+        # #118: quota non misurata dalla visione -> NaN
+        value_str = "NaN" if m.value is None else str(m.value).replace(".", decimal_separator)
         deviation_str = (
             str(m.deviation).replace(".", decimal_separator)
             if m.deviation is not None
diff --git a/src/backend/api/routers/statistics.py b/src/backend/api/routers/statistics.py
index da67f0a..b785b6e 100644
--- a/src/backend/api/routers/statistics.py
+++ b/src/backend/api/routers/statistics.py
@@ -146,7 +146,8 @@ async def get_capability(
         date_from, date_to, operator_id, lot_number, serial_number,
         production_run_id=production_run_id,  # #58
     )
-    values = [float(m.value) for m in measurements]
+    # #118: le quote NaN (value None) non entrano nei calcoli
+    values = [float(m.value) for m in measurements if m.value is not None]
     tol = await _get_subtask_tolerances(db, subtask_id)
     return compute_capability(values, tol["utl"], tol["ltl"], tol["nominal"])
 
@@ -171,6 +172,8 @@ async def get_control_chart(
         date_from, date_to, operator_id, lot_number, serial_number,
         production_run_id=production_run_id,  # #58
     )
+    # #118: le quote NaN (value None) si saltano, valori e istanti restano allineati
+    measurements = [m for m in measurements if m.value is not None]
     values = [float(m.value) for m in measurements]
     timestamps = [m.measured_at for m in measurements]
     tol = await _get_subtask_tolerances(db, subtask_id)
@@ -201,7 +204,8 @@ async def get_histogram(
         date_from, date_to, operator_id, lot_number, serial_number,
         production_run_id=production_run_id,  # #58
     )
-    values = [float(m.value) for m in measurements]
+    # #118: le quote NaN (value None) non entrano nell'istogramma
+    values = [float(m.value) for m in measurements if m.value is not None]
     return compute_histogram(values, n_bins)
 
 
diff --git a/src/backend/api/routers/vision.py b/src/backend/api/routers/vision.py
index 626619a..9917567 100644
--- a/src/backend/api/routers/vision.py
+++ b/src/backend/api/routers/vision.py
@@ -162,7 +162,10 @@ async def execute(
         engine_version=result.engine_version,
         measurements=[
             VisionMeasurementResult(
-                subtask_id=m.subtask_id, value=float(m.value), pass_fail=m.pass_fail,
+                subtask_id=m.subtask_id,
+                # #118: None = quota non prodotta, il frontend la mostra NaN
+                value=float(m.value) if m.value is not None else None,
+                pass_fail=m.pass_fail,
             )
             for m in saved
         ],
diff --git a/src/backend/migrations/versions/022_measurement_value_nullable.py b/src/backend/migrations/versions/022_measurement_value_nullable.py
new file mode 100644
index 0000000..117d6aa
--- /dev/null
+++ b/src/backend/migrations/versions/022_measurement_value_nullable.py
@@ -0,0 +1,39 @@
+"""measurements.value nullable (#118)
+
+measurements.value: NULL = quota che il grafo di visione non ha prodotto
+(l'operatore la vede come NaN, esito sempre `fail`, deviazione NULL). Prima
+execute rifiutava con 422 l'intera acquisizione. measurements.deviation era
+gia' nullable.
+
+Downgrade: torna NOT NULL; FALLISCE se esistono righe con value NULL (vanno
+cancellate o valorizzate prima).
+
+Revision ID: 022_measurement_value_nullable
+Revises: 021_task_acquisition
+Create Date: 2026-10-28
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '022_measurement_value_nullable'
+down_revision: Union[str, None] = '021_task_acquisition'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # batch_alter_table come nelle migrazioni vicine: serve a SQLite
+    with op.batch_alter_table('measurements') as batch:
+        batch.alter_column(
+            'value', existing_type=sa.DECIMAL(12, 6), nullable=True,
+        )
+
+
+def downgrade() -> None:
+    with op.batch_alter_table('measurements') as batch:
+        batch.alter_column(
+            'value', existing_type=sa.DECIMAL(12, 6), nullable=False,
+        )
diff --git a/src/backend/models/api/measurement.py b/src/backend/models/api/measurement.py
index 11ec194..c7418b4 100644
--- a/src/backend/models/api/measurement.py
+++ b/src/backend/models/api/measurement.py
@@ -43,7 +43,7 @@ class MeasurementResponse(BaseModel):
     subtask_id: int
     version_id: int
     measured_by: int
-    value: float
+    value: Optional[float] = None  # #118: null = quota non prodotta dalla visione (NaN)
     pass_fail: str
     deviation: Optional[float] = None
     lot_number: Optional[str] = None
@@ -108,7 +108,7 @@ class CycleMeasurementResponse(BaseModel):
     """One quote already measured in the cycle under way."""
 
     subtask_id: int
-    value: float
+    value: Optional[float] = None  # #118: null = NaN
     pass_fail: str
     measured_at: UtcDateTime
 
diff --git a/src/backend/models/api/vision.py b/src/backend/models/api/vision.py
index 155f78e..b025dcc 100644
--- a/src/backend/models/api/vision.py
+++ b/src/backend/models/api/vision.py
@@ -7,7 +7,7 @@ from pydantic import BaseModel, ConfigDict
 class VisionMeasurementResult(BaseModel):
     """One quote's outcome, as much of it as the client needs to show."""
     subtask_id: int
-    value: float
+    value: float | None  # #118: null = quota non prodotta dal grafo (NaN), pass_fail "fail"
     pass_fail: str
 
 
diff --git a/src/backend/models/orm/measurement.py b/src/backend/models/orm/measurement.py
index 1020fd7..5726416 100644
--- a/src/backend/models/orm/measurement.py
+++ b/src/backend/models/orm/measurement.py
@@ -26,7 +26,8 @@ class Measurement(Base):
     )
 
     # Measurement data
-    value: Mapped[float] = mapped_column(DECIMAL(12, 6), nullable=False)
+    # #118: NULL = quota che il grafo di visione non ha prodotto (mostrata NaN, sempre fail)
+    value: Mapped[Optional[float]] = mapped_column(DECIMAL(12, 6), nullable=True)
     pass_fail: Mapped[str] = mapped_column(
         Enum("pass", "warning", "fail", name="pass_fail_enum"), nullable=False
     )
diff --git a/src/backend/services/measurement_service.py b/src/backend/services/measurement_service.py
index 456249b..5324a05 100644
--- a/src/backend/services/measurement_service.py
+++ b/src/backend/services/measurement_service.py
@@ -302,7 +302,7 @@ async def current_cycle_measurements(
     return [
         {
             "subtask_id": m.subtask_id,
-            "value": float(m.value),
+            "value": float(m.value) if m.value is not None else None,  # #118: NaN
             "pass_fail": m.pass_fail,
             "measured_at": m.measured_at,
         }
@@ -355,7 +355,7 @@ async def save_measurement(
     subtask_id: int,
     version_id: int,
     measured_by: int,
-    value: float,
+    value: float | None,
     lot_number: str | None = None,
     serial_number: str | None = None,
     input_method: str = "manual",
@@ -372,8 +372,12 @@ async def save_measurement(
     batch of quotes taken at the same instant (see Ruling R10 / vision_service):
     the gate models "moving on" between measurements taken one after another,
     which does not exist inside a single camera acquisition.
+
+    #118: ``value=None`` is a quote the vision graph did not produce (shown as
+    NaN): saved as a ``fail`` with no deviation. Only the vision path passes it.
     """
-    _validate_measured_value(value)
+    if value is not None:  # #118: una quota non misurata non ha un valore da validare
+        _validate_measured_value(value)
 
     # Get subtask for tolerance values
     result = await db.execute(
@@ -421,8 +425,12 @@ async def save_measurement(
     # Rounded once, here, so the stored value is exactly the one the verdict
     # above was computed on - calculate_pass_fail rounds internally too, but
     # matching it here keeps the persisted row from disagreeing with itself.
-    value = round(value, 6)
-    pass_fail, deviation = calculate_pass_fail(value, subtask)
+    if value is None:
+        # #118: quota non prodotta dal grafo -> NaN: fail, nessuna deviazione
+        pass_fail, deviation = "fail", None
+    else:
+        value = round(value, 6)
+        pass_fail, deviation = calculate_pass_fail(value, subtask)
 
     measurement = Measurement(
         subtask_id=subtask_id,
diff --git a/src/backend/services/monitor_service.py b/src/backend/services/monitor_service.py
index 81533b0..7944cb1 100644
--- a/src/backend/services/monitor_service.py
+++ b/src/backend/services/monitor_service.py
@@ -96,7 +96,12 @@ async def list_open_runs(db: AsyncSession) -> list[MonitorRun]:
             per_sub[row.subtask_id].append(row)
         subtasks = []
         for sid, group in sorted(per_sub.items()):
-            mean = sum(float(g.value) for g in group) / len(group)
+            # #118: le quote NaN (value None) non entrano nella media; senza
+            # nessun valore numerico la quota non ha una media da mostrare
+            numeric = [float(g.value) for g in group if g.value is not None]
+            if not numeric:
+                continue
+            mean = sum(numeric) / len(numeric)
             first = group[0]
             subtasks.append(MonitorSubtask(
                 subtask_id=sid, description=first.description, unit=first.unit,
diff --git a/src/backend/services/production_export_service.py b/src/backend/services/production_export_service.py
index 4d7acdb..c547f87 100644
--- a/src/backend/services/production_export_service.py
+++ b/src/backend/services/production_export_service.py
@@ -159,7 +159,7 @@ async def build_statistics_csv(db: AsyncSession, run: ProductionRun) -> str:
             subtask.marker_number if subtask else "",
             neutralise_csv_cell(subtask.description) if subtask else "",
             number(subtask.nominal) if subtask else "",
-            number(measurement.value),
+            number(measurement.value) if measurement.value is not None else "NaN",  # #118
             number(measurement.deviation),
             measurement.pass_fail,
             number(subtask.ltl) if subtask else "",
diff --git a/src/backend/services/report_service.py b/src/backend/services/report_service.py
index a032084..2c78fdd 100644
--- a/src/backend/services/report_service.py
+++ b/src/backend/services/report_service.py
@@ -318,8 +318,10 @@ async def generate_spc_report(
 
     # 2. Compute SPC data
     pass_fail_values = [m.pass_fail for m in measurements]
-    values = [float(m.value) for m in measurements]
-    timestamps = [m.measured_at for m in measurements]
+    # #118: le quote NaN (value None) contano nell'esito ma non nei calcoli
+    numeric = [m for m in measurements if m.value is not None]
+    values = [float(m.value) for m in numeric]
+    timestamps = [m.measured_at for m in numeric]
 
     summary = compute_summary(pass_fail_values)
 
@@ -426,7 +428,7 @@ async def generate_measurement_report(
         rows.append({
             "num": i,
             "subtask": f"#{st_info.get('marker_number', '?')} — {st_info.get('description', '?')}",
-            "value": f"{float(m.value):.4f}",
+            "value": f"{float(m.value):.4f}" if m.value is not None else "NaN",  # #118
             "unit": st_info.get("unit", "mm"),
             "pass_fail": m.pass_fail,
             "measured_at": to_local(m.measured_at).strftime("%Y-%m-%d %H:%M"),
diff --git a/src/backend/services/vision_service.py b/src/backend/services/vision_service.py
index e2ae9f8..a01d7de 100644
--- a/src/backend/services/vision_service.py
+++ b/src/backend/services/vision_service.py
@@ -693,23 +693,13 @@ async def execute_task(
     )
     outputs = report["outputs"]
 
-    # Every quote or none. A half-measured piece read as a whole one is worse
-    # than a piece not measured at all. A quote counts as produced only if its
-    # output is present *and* a finite, non-bool number: the in-process runner
-    # already drops NaN/inf itself (see src/vision/runner.py), but the worker
-    # is reached over HTTP - a different implementation of it, or a malformed
-    # response, could still hand back None or a non-finite float for a mapped
-    # key instead of omitting it outright.
-    missing = [q.vision_output for q in quotes if not _is_measurable(outputs.get(q.vision_output))]
-    if missing:
-        failed = ", ".join(f["tool_name"] for f in report["failures"])
-        raise HTTPException(
-            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
-            detail=(
-                f"the graph did not produce {', '.join(missing)}"
-                + (f" (tools that failed: {failed})" if failed else "")
-            ),
-        )
+    # #118: una quota che il grafo non produce non blocca piu' l'esecuzione
+    # (prima 422 "the graph did not produce"): viene salvata con value NULL,
+    # mostrata NaN, sempre `fail`; i motivi restano nei `failures` del risultato.
+    # Una quota conta come prodotta solo se l'uscita c'e' *ed* e' un numero
+    # finito non-bool: il worker risponde via HTTP, un'altra implementazione o
+    # una risposta malformata potrebbe dare None o un non finito per una chiave
+    # mappata invece di ometterla.
 
     overlay = report.get("overlay") or []
     image_path, overlay_path = save_result_files(task.id, image_bytes, overlay, image_ext)
@@ -737,7 +727,11 @@ async def execute_task(
             subtask_id=quote.id,
             version_id=version_id,
             measured_by=measured_by,
-            value=float(outputs[quote.vision_output]),
+            # #118: None = quota non prodotta (NaN), salvata come fail
+            value=(
+                float(outputs[quote.vision_output])
+                if _is_measurable(outputs.get(quote.vision_output)) else None
+            ),
             lot_number=lot_number,
             serial_number=serial_number,
             input_method="camera",
@@ -762,8 +756,9 @@ async def check_task(
     VisionResult, niente file, niente misure. L'esito per quota usa
     calculate_pass_fail sulle quote con vision_output, nell'ordine di
     marker_number come execute. Le quote che il grafo non produce (pezzo non
-    ancora in posizione) restano fuori da `measurements` e il perche' sta in
-    `failures`: un'anteprima non deve dare 422 a ogni frame.
+    ancora in posizione) entrano in `measurements` con `value` None (NaN) e
+    `pass_fail` "fail" (#118, come execute); il perche' sta in `failures`:
+    un'anteprima non deve dare 422 a ogni frame.
     """
     if task.task_type not in VISION_TASK_TYPES:
         raise HTTPException(
@@ -809,6 +804,7 @@ async def check_task(
         **worker_kwargs,
     )
     outputs = report["outputs"]
+    # #118: una voce per ogni quota, in ordine di marker_number; non prodotta -> NaN/fail
     measurements = [
         {
             "subtask_id": q.id,
@@ -816,8 +812,10 @@ async def check_task(
             "pass_fail": measurement_service.calculate_pass_fail(
                 float(outputs[q.vision_output]), q,
             )[0],
+        } if _is_measurable(outputs.get(q.vision_output)) else {
+            "subtask_id": q.id, "value": None, "pass_fail": "fail",
         }
-        for q in quotes if _is_measurable(outputs.get(q.vision_output))
+        for q in quotes
     ]
     return {
         "outcome": report.get("outcome"),
diff --git a/src/backend/tests/test_migrations.py b/src/backend/tests/test_migrations.py
index e124a82..57b8b30 100644
--- a/src/backend/tests/test_migrations.py
+++ b/src/backend/tests/test_migrations.py
@@ -360,3 +360,22 @@ class TestTaskAcquisitionMigration:
         assert "camera_url" in cols("stations")  # la 020 resta
         command.upgrade(cfg, "head")  # e di nuovo su
         assert "acquisition_json" in cols("recipe_tasks")
+
+
+class TestMeasurementValueNullableMigration:
+    """022_measurement_value_nullable: measurements.value accetta NULL, su e giu (#118)."""
+
+    def test_022_upgrade_and_downgrade(self, sqlite_database_url):
+        db_path, _ = sqlite_database_url
+        cfg = _alembic_config()
+
+        def value_nullable():
+            cols = _inspect(db_path).get_columns("measurements")
+            return {c["name"]: c["nullable"] for c in cols}["value"]
+
+        command.upgrade(cfg, "head")
+        assert value_nullable() is True
+        command.downgrade(cfg, "021_task_acquisition")
+        assert value_nullable() is False
+        command.upgrade(cfg, "head")  # e di nuovo su
+        assert value_nullable() is True
diff --git a/src/backend/tests/test_nan_measurements.py b/src/backend/tests/test_nan_measurements.py
new file mode 100644
index 0000000..a0d43be
--- /dev/null
+++ b/src/backend/tests/test_nan_measurements.py
@@ -0,0 +1,114 @@
+"""#118: una quota non misurata dalla visione e' una misura con value NULL (NaN), sempre fail.
+
+Il valore NULL non deve far cadere statistiche, report, CSV e liste, e non entra
+nei calcoli numerici (medie, indici, istogramma); conta solo nell'esito.
+"""
+import csv
+
+from httpx import AsyncClient
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from src.backend.models.orm.measurement import Measurement
+from src.backend.models.orm.user import User
+from src.backend.services import measurement_service
+from src.backend.tests.conftest import auth_headers, create_test_recipe
+from src.backend.tests.test_statistics import _seed_measurements
+
+
+async def _recipe_with_nan(client, db_session, tec_user):
+    """Una ricetta con tre misure numeriche e una NaN (value NULL, fail)."""
+    recipe = await create_test_recipe(db_session, tec_user.id)
+    subtask_id, version_id = await _seed_measurements(
+        client, tec_user, recipe.id, [10.0, 10.1, 9.9],
+    )
+    nan = await measurement_service.save_measurement(
+        db_session, subtask_id=subtask_id, version_id=version_id,
+        measured_by=tec_user.id, value=None, input_method="camera",
+        enforce_tolerance_gate=False,
+    )
+    await db_session.commit()
+    return recipe, subtask_id, version_id, nan
+
+
+async def test_save_measurement_none_is_fail_without_deviation(
+    client: AsyncClient, db_session: AsyncSession, measurement_tec_user: User,
+):
+    _, _, _, nan = await _recipe_with_nan(client, db_session, measurement_tec_user)
+    assert nan.value is None
+    assert nan.pass_fail == "fail"
+    assert nan.deviation is None
+
+
+async def test_manual_create_still_requires_a_value(
+    client: AsyncClient, db_session: AsyncSession, measurement_tec_user: User,
+):
+    """Solo il percorso visione puo' produrre NaN: la creazione manuale resta float."""
+    recipe = await create_test_recipe(db_session, measurement_tec_user.id)
+    subtask_id, version_id = await _seed_measurements(
+        client, measurement_tec_user, recipe.id, [],
+    )
+    resp = await client.post(
+        "/api/measurements/", headers=auth_headers(measurement_tec_user),
+        json={"subtask_id": subtask_id, "version_id": version_id, "value": None},
+    )
+    assert resp.status_code == 422
+
+
+async def test_statistics_skip_the_nan_measurement(
+    client: AsyncClient, db_session: AsyncSession,
+    measurement_tec_user: User, metrologist_user: User,
+):
+    recipe, subtask_id, _, _ = await _recipe_with_nan(
+        client, db_session, measurement_tec_user,
+    )
+    params = {"recipe_id": recipe.id, "subtask_id": subtask_id}
+    headers = auth_headers(metrologist_user)
+
+    cap = await client.get("/api/statistics/capability", headers=headers, params=params)
+    assert cap.status_code == 200
+    assert cap.json()["n"] == 3
+    assert abs(cap.json()["mean"] - 10.0) < 1e-9
+
+    chart = await client.get("/api/statistics/control-chart", headers=headers, params=params)
+    assert chart.status_code == 200
+    assert len(chart.json()["values"]) == 3
+
+    hist = await client.get("/api/statistics/histogram", headers=headers, params=params)
+    assert hist.status_code == 200
+
+    summary = await client.get(
+        "/api/statistics/summary", headers=headers, params={"recipe_id": recipe.id},
+    )
+    assert summary.status_code == 200
+
+
+async def test_measurement_list_returns_null_value(
+    client: AsyncClient, db_session: AsyncSession, measurement_tec_user: User,
+):
+    _, _, version_id, nan = await _recipe_with_nan(client, db_session, measurement_tec_user)
+    resp = await client.get(
+        "/api/measurements/", headers=auth_headers(measurement_tec_user),
+        params={"version_id": version_id, "per_page": 50},
+    )
+    assert resp.status_code == 200
+    rows = {m["id"]: m for m in resp.json()["items"]}
+    assert rows[nan.id]["value"] is None
+    assert rows[nan.id]["pass_fail"] == "fail"
+    assert rows[nan.id]["deviation"] is None
+
+
+async def test_csv_export_writes_nan(
+    client: AsyncClient, db_session: AsyncSession, measurement_tec_user: User,
+):
+    _, _, _, nan = await _recipe_with_nan(client, db_session, measurement_tec_user)
+    resp = await client.get(
+        "/api/measurements/export/csv", headers=auth_headers(measurement_tec_user),
+    )
+    assert resp.status_code == 200
+    rows = list(csv.reader(resp.text.splitlines()))
+    header = rows[0]
+    by_id = {r[header.index("id")]: r for r in rows[1:]}
+    row = by_id[str(nan.id)]
+    assert row[header.index("value")] == "NaN"
+    assert row[header.index("pass_fail")] == "fail"
+    assert row[header.index("deviation")] == ""
diff --git a/src/backend/tests/test_vision_execute.py b/src/backend/tests/test_vision_execute.py
index 2073bf9..49b3d6b 100644
--- a/src/backend/tests/test_vision_execute.py
+++ b/src/backend/tests/test_vision_execute.py
@@ -134,72 +134,124 @@ async def test_the_execution_records_which_engine_produced_it(
     assert result.graph_snapshot == task.vision_json
 
 
+# #118: una quota che il grafo non produce non e' piu' un 422: e' NaN (value
+# NULL), `fail`, salvata con le altre.
+async def _assert_nan_saved(client, db_session, user, task, first, second):
+    response = await client.post(
+        "/api/vision/execute",
+        headers=auth_headers(user),
+        files={"image": ("p.png", an_image(), "image/png")},
+        data={"task_id": str(task.id)},
+    )
+    assert response.status_code == 200
+    body = response.json()
+    assert [m["subtask_id"] for m in body["measurements"]] == [first.id, second.id]
+    assert body["measurements"][0]["value"] is None
+    assert body["measurements"][0]["pass_fail"] == "fail"
+    assert body["measurements"][1]["value"] == GOOD
+    rows = (await db_session.execute(
+        select(Measurement).order_by(Measurement.subtask_id)
+    )).scalars().all()
+    assert len(rows) == 2
+    assert rows[0].value is None
+    assert rows[0].pass_fail == "fail"
+    assert rows[0].deviation is None
+    assert rows[0].vision_result_id is not None
+    assert rows[1].value is not None and rows[1].pass_fail == "pass"
+
+
 @pytest.mark.asyncio
-async def test_a_missing_output_names_itself(
+async def test_a_missing_output_is_saved_as_nan(
     client, db_session, measurement_tec_user, worker_says,
 ):
-    """No half measurement: if an output is missing, the error names it."""
+    """#118: output assente -> 200, misura NULL/fail, le altre quote salvate."""
     recipe = await create_test_recipe(db_session, measurement_tec_user.id)
-    version, task, subtask = await recipe_parts(db_session, recipe.id)
-    task.task_type = "camera_measure"
-    task.vision_json = {"schema_version": 1, "name": "p", "tools": []}
-    subtask.vision_output = "t1.diameter"
-    await db_session.commit()
-    worker_says({"t1.radius": 5.0})
+    version, task, first, second = await two_vision_quotes(db_session, recipe.id)
+    worker_says({"t1.radius": GOOD}, failures=[{"tool_name": "arco_tr"}])
+    await _assert_nan_saved(client, db_session, measurement_tec_user, task, first, second)
+
+
+@pytest.mark.asyncio
+async def test_all_outputs_missing_still_saves_every_quote(
+    client, db_session, measurement_tec_user, worker_says,
+):
+    """#118: anche senza nessuna uscita, una misura NaN per quota."""
+    recipe = await create_test_recipe(db_session, measurement_tec_user.id)
+    version, task, first, second = await two_vision_quotes(db_session, recipe.id)
+    worker_says({})
 
     response = await client.post(
         "/api/vision/execute",
         headers=auth_headers(measurement_tec_user),
         files={"image": ("p.png", an_image(), "image/png")},
-        data={"task_id": str(task.id), "lot_number": "L1"},
+        data={"task_id": str(task.id)},
     )
 
-    assert response.status_code == 422
-    assert "t1.diameter" in response.json()["detail"]
-    assert (await db_session.execute(select(Measurement))).scalars().all() == []
+    assert response.status_code == 200
+    assert [m["value"] for m in response.json()["measurements"]] == [None, None]
+    rows = (await db_session.execute(select(Measurement))).scalars().all()
+    assert len(rows) == 2 and all(r.value is None and r.pass_fail == "fail" for r in rows)
 
 
 @pytest.mark.asyncio
-async def test_a_null_output_counts_as_not_produced(
+async def test_a_null_output_is_saved_as_nan(
     client, db_session, measurement_tec_user, worker_says,
 ):
-    """A worker answering with the key present but null (not omitted) must not
-    reach float(None) as a bare TypeError - it is "not produced", same as a
-    missing key (#16)."""
+    """Chiave presente ma null (non omessa): NaN, non TypeError (#16, #118)."""
     recipe = await create_test_recipe(db_session, measurement_tec_user.id)
     version, task, first, second = await two_vision_quotes(db_session, recipe.id)
     worker_says({"t1.diameter": None, "t1.radius": GOOD})
-
-    response = await client.post(
-        "/api/vision/execute",
-        headers=auth_headers(measurement_tec_user),
-        files={"image": ("p.png", an_image(), "image/png")},
-        data={"task_id": str(task.id)},
-    )
-
-    assert response.status_code == 422
-    assert "t1.diameter" in response.json()["detail"]
-    assert (await db_session.execute(select(Measurement))).scalars().all() == []
+    await _assert_nan_saved(client, db_session, measurement_tec_user, task, first, second)
 
 
 @pytest.mark.asyncio
-async def test_a_non_finite_output_counts_as_not_produced(
+async def test_a_non_finite_output_is_saved_as_nan(
     client, db_session, measurement_tec_user, worker_says,
 ):
-    """NaN/inf must not become a saved measurement (#16)."""
+    """NaN/inf non diventano un valore salvato: diventano NaN (NULL) (#16, #118)."""
     recipe = await create_test_recipe(db_session, measurement_tec_user.id)
     version, task, first, second = await two_vision_quotes(db_session, recipe.id)
     worker_says({"t1.diameter": float("nan"), "t1.radius": GOOD})
+    await _assert_nan_saved(client, db_session, measurement_tec_user, task, first, second)
+
+
+@pytest.mark.asyncio
+async def test_a_nan_quote_still_blocks_the_next_acquisition(
+    client, db_session, measurement_tec_user, worker_says,
+):
+    """#118: la quota NaN e' un fail come gli altri, il blocco di tolleranza resta."""
+    recipe = await create_test_recipe(db_session, measurement_tec_user.id)
+    version, task, first, second = await two_vision_quotes(db_session, recipe.id)
+    worker_says({"t1.radius": GOOD})
+    await _assert_nan_saved(client, db_session, measurement_tec_user, task, first, second)
+
+    blocking = await measurement_service.pending_authorisation(
+        db_session, version.id, measurement_tec_user.id,
+    )
+    assert blocking is not None and blocking.subtask_id == first.id and blocking.value is None
+
+
+@pytest.mark.asyncio
+async def test_check_lists_a_missing_quote_as_nan(
+    client, db_session, measurement_tec_user, worker_says,
+):
+    """#118: check -> una voce per quota, la non prodotta e' value null / fail."""
+    recipe = await create_test_recipe(db_session, measurement_tec_user.id)
+    version, task, first, second = await two_vision_quotes(db_session, recipe.id)
+    worker_says({"t1.radius": GOOD})
 
     response = await client.post(
-        "/api/vision/execute",
+        "/api/vision/check",
         headers=auth_headers(measurement_tec_user),
         files={"image": ("p.png", an_image(), "image/png")},
         data={"task_id": str(task.id)},
     )
 
-    assert response.status_code == 422
-    assert "t1.diameter" in response.json()["detail"]
+    assert response.status_code == 200
+    assert response.json()["measurements"] == [
+        {"subtask_id": first.id, "value": None, "pass_fail": "fail"},
+        {"subtask_id": second.id, "value": GOOD, "pass_fail": "pass"},
+    ]
     assert (await db_session.execute(select(Measurement))).scalars().all() == []