Resolve passives from catalog, BOM value, and Murata LQW18AN without an LLM.

Skip the model (and the credit gate) when LCSC/DigiKey already list C/V/Z, when the BOM value is a single R/C/L/FB token, or when the MPN is an LQW18AN inductor. Ferrite beads keep impedance, not invented henries; value-only specs stay out of the shared library.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_passive_from_distributor.py

@@ -40,3 +40,94 @@ def test_skips_when_no_value():
         category="",
         description="some module",
     ) is None
+
+
+def test_ferrite_bead_from_impedance():
+    model = specs_from_distributor(
+        mpn="BLM18PG121SN1D",
+        params=[
+            {"name": "Impedance @ Frequency", "value": "120 Ohms @ 100 MHz"},
+            {"name": "Package / Case", "value": "0603"},
+            {"name": "Current Rating", "value": "2 A"},
+        ],
+        category="Filters / Ferrite Beads",
+        description="FERRITE BEAD 120 OHM 0603 1LN",
+    )
+    assert model is not None
+    specs = model.specs
+    assert specs.component_subtype == "passive.ferrite_bead"
+    assert specs.impedance_ohm == 120
+    assert specs.value_henries is None
+    assert "120ohm" in specs.value_formatted
+    assert "100" in specs.value_formatted
+    assert specs.package == "0603"
+    assert specs.current_rating_a == "2 A"
+
+
+def test_specs_from_lcsc_payload():
+    from backend.services.passive_from_distributor import specs_from_lcsc_payload
+
+    model = specs_from_lcsc_payload(
+        "CL21B225KPFNNNE",
+        {
+            "package": "0805",
+            "manufacturer": "Samsung",
+            "category": "Capacitors",
+            "subcategory": "MLCC",
+            "description": "2.2uF ±10% 10V X7R 0805",
+        },
+    )
+    assert model is not None
+    assert abs(model.specs.value_farads - 2.2e-6) < 1e-12
+
+
+def test_auto_resolve_skips_llm_when_catalog_parses(monkeypatch):
+    import asyncio
+    from pathlib import Path
+
+    from backend.services.extraction import auto_resolve_specs
+
+    async def boom(*_a, **_k):
+        raise AssertionError("LLM must not run")
+
+    monkeypatch.setattr("backend.services.extraction.call_with_fallback", boom)
+    tax = Path(__file__).resolve().parents[1] / "taxonomy"
+    model = asyncio.run(
+        auto_resolve_specs(
+            mpn="CL21B225KPFNNNE",
+            digikey_params=[{"name": "Package / Case", "value": "0805"}],
+            digikey_category="Capacitors / Ceramic Capacitors",
+            digikey_description="2.2uF ±10% 10V X7R 0805",
+            component_type="passive",
+            taxonomy_dir=tax,
+        )
+    )
+    assert abs(model.specs.value_farads - 2.2e-6) < 1e-12
+
+
+def test_auto_resolve_use_llm_false_on_ferrite(monkeypatch):
+    import asyncio
+    from pathlib import Path
+
+    from backend.services.extraction import auto_resolve_specs
+
+    async def boom(*_a, **_k):
+        raise AssertionError("LLM must not run")
+
+    monkeypatch.setattr("backend.services.extraction.call_with_fallback", boom)
+    tax = Path(__file__).resolve().parents[1] / "taxonomy"
+    model = asyncio.run(
+        auto_resolve_specs(
+            mpn="BLM18PG121SN1D",
+            digikey_params=[
+                {"name": "Impedance @ Frequency", "value": "120 Ohms @ 100 MHz"},
+            ],
+            digikey_category="Filters / Ferrite Beads",
+            digikey_description="FERRITE BEAD 120 OHM 0603 1LN",
+            component_type="passive",
+            taxonomy_dir=tax,
+            use_llm=False,
+        )
+    )
+    assert model.specs.impedance_ohm == 120
+    assert model.specs.component_subtype == "passive.ferrite_bead"

tests/test_passive_from_mpn.py

@@ -38,7 +38,27 @@ def test_chip_resistor_from_mpn():
     assert abs(model.specs.value_ohms - 2200) < 0.1
 
 
-def test_skips_murata_and_bare_value():
+def test_murata_lqw18an():
+    model = specs_from_mpn("LQW18AN12NG00D")
+    assert model is not None
+    assert model.specs.specs_type == "inductor"
+    assert abs(model.specs.value_henries - 12e-9) < 1e-15
+    assert model.specs.package == "0603"
+    assert model.specs.tolerance == "±2%"
+
+    model = specs_from_mpn("LQW18AN18NJ00D")
+    assert abs(model.specs.value_henries - 18e-9) < 1e-15
+    assert model.specs.tolerance == "±5%"
+
+    model = specs_from_mpn("LQW18AN2N2D00D")
+    assert abs(model.specs.value_henries - 2.2e-9) < 1e-15
+    assert model.specs.tolerance == "±0.5nH"
+
+    model = specs_from_mpn("LQW18ANR10G00D")
+    assert abs(model.specs.value_henries - 100e-9) < 1e-15
+
+
+def test_skips_opaque_murata_and_bare_value():
     assert specs_from_mpn("GRM21A5C2J200JA01") is None
     assert specs_from_mpn("18pF") is None
     assert specs_from_mpn("CH340E") is None

tests/test_passive_from_value.py

@@ -0,0 +1,88 @@
+import asyncio
+from pathlib import Path
+
+import pytest
+
+from backend.services.passive_from_value import (
+    is_placeholder_value,
+    specs_from_bom_value,
+)
+
+
+def test_capacitor_picofarads():
+    model = specs_from_bom_value("18pF", "18pF", "C")
+    assert model is not None
+    assert model.specs.specs_type == "capacitor"
+    assert abs(model.specs.value_farads - 18e-12) < 1e-18
+
+
+def test_resistor_kilo_and_euro():
+    k = specs_from_bom_value("4.7k", "4.7k", "R")
+    assert k is not None
+    assert abs(k.specs.value_ohms - 4700) < 1e-6
+    euro = specs_from_bom_value("4k7", "4k7", "R")
+    assert euro is not None
+    assert abs(euro.specs.value_ohms - 4700) < 1e-6
+
+
+def test_inductor_uh():
+    model = specs_from_bom_value("10uH", "10uH", "L")
+    assert model is not None
+    assert abs(model.specs.value_henries - 10e-6) < 1e-12
+
+
+def test_ferrite_impedance_at_freq():
+    model = specs_from_bom_value("600R@100MHz", "600R@100MHz", "FB")
+    assert model is not None
+    assert model.specs.component_subtype == "passive.ferrite_bead"
+    assert model.specs.impedance_ohm == 600
+    assert model.specs.value_henries is None
+    assert "100MHz" in model.specs.value_formatted
+
+
+def test_placeholders_skip():
+    for raw in ("DNP", "NC", "JUMPER", "TBD", "-"):
+        assert is_placeholder_value(raw)
+        assert specs_from_bom_value(raw, raw, "R") is None
+
+
+def test_ambiguous_string_returns_none():
+    assert specs_from_bom_value("mystery", "do not stuff", "R") is None
+
+
+def test_resolve_from_value_skips_llm_when_parseable(monkeypatch):
+    from backend.services.extraction import resolve_from_value
+
+    async def boom(*_a, **_k):
+        raise AssertionError("LLM must not run")
+
+    monkeypatch.setattr("backend.services.extraction.call_with_fallback", boom)
+    tax = Path(__file__).resolve().parents[1] / "taxonomy"
+    model = asyncio.run(
+        resolve_from_value(
+            mpn="18pF",
+            value="18pF",
+            ref_prefix="C",
+            taxonomy_dir=tax,
+        )
+    )
+    assert abs(model.specs.value_farads - 18e-12) < 1e-18
+
+
+def test_resolve_from_value_placeholder_no_llm(monkeypatch):
+    from backend.services.extraction import resolve_from_value
+
+    async def boom(*_a, **_k):
+        raise AssertionError("LLM must not run")
+
+    monkeypatch.setattr("backend.services.extraction.call_with_fallback", boom)
+    tax = Path(__file__).resolve().parents[1] / "taxonomy"
+    with pytest.raises(ValueError, match="Placeholder"):
+        asyncio.run(
+            resolve_from_value(
+                mpn="DNP",
+                value="DNP",
+                ref_prefix="R",
+                taxonomy_dir=tax,
+            )
+        )

tests/test_purple_parts_resolver.py

@@ -447,9 +447,8 @@ def test_lcsc_resolve_passive_404_when_lcsc_id_missing(tmp_path, monkeypatch):
 
 @pytest.mark.asyncio
 async def test_lcsc_resolve_passive_success_and_cached(tmp_path, monkeypatch):
-    """First call resolves via auto_resolve_specs (mocked) and writes the
-    project model + library copy. Second call short-circuits with cached=True
-    and does not invoke auto_resolve_specs again."""
+    """First call parses the LCSC description without the LLM. Second call
+    short-circuits with cached=True and does not invoke auto_resolve_specs."""
     from backend.config import settings
     from backend.pinscopex.models import CapacitorSpecs, ComponentModel
     from backend.services import purple_parts
@@ -526,7 +525,7 @@ async def test_lcsc_resolve_passive_success_and_cached(tmp_path, monkeypatch):
     )
     assert resp.status_code == 200, resp.text
 
-    # First call: resolves via mocked auto_resolve_specs.
+    # First call: catalog parse, no LLM.
     resp = client.post(
         f"/api/projects/{project_id}/lcsc/resolve-passive",
         json={"lcsc_id": "C15850"},
@@ -537,7 +536,7 @@ async def test_lcsc_resolve_passive_success_and_cached(tmp_path, monkeypatch):
     assert body["lcsc_id"] == "C15850"
     assert body["cached"] is False
     assert body["model"]["mpn"] == "CL21A106KAYNNNE"
-    assert call_count["n"] == 1
+    assert call_count["n"] == 0
 
     # Library copy should exist for cross-project reuse.
     from backend.pinscopex.utils import safe_mpn
@@ -553,7 +552,7 @@ async def test_lcsc_resolve_passive_success_and_cached(tmp_path, monkeypatch):
     body = resp.json()
     assert body["cached"] is True
     assert body["model"]["mpn"] == "CL21A106KAYNNNE"
-    assert call_count["n"] == 1  # not invoked again
+    assert call_count["n"] == 0  # still no LLM
 
 
 # ---------------------------------------------------------------------------