From 98d1cfa1a89f2ecd4a976b4c0b7ad8f21a9dee91 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mar=C3=ADa=20Juaristi?=
 <127882282+juaristi22@users.noreply.github.com>
Date: Thu, 27 Aug 2026 17:16:58 +0200
Subject: [PATCH 1/3] Derive band edges from the compiled register, never the
 pruned roster
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Banded measures took each band's upper edge from the lower edges of
sibling specs in the live registry, so excluding a band silently widened
its lower neighbour to the next surviving edge (or to infinity at the
top) — the #792 movers: 12 of 361 shared measures shifted by up to +858%
when the exclusion register grew 5->47, each by exactly the mass of the
absorbed excluded siblings. materialize_target_bindings and
resolve_target_measures now accept a band_edge_registry (default: the
materialized registry, bit-identical for existing callers), and
_band_bounds refuses a spec whose own lower edge is absent from the
supplied edge set rather than guessing. Regression fence: survivors must
be bit-identical under sibling exclusion, for numeric edges and
published range labels.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 .../792-band-edges-compiled-register.fixed.md |   1 +
 .../microcosm/build/target_materialization.py |  23 ++-
 .../tests/test_target_materialization.py      | 188 ++++++++++++++++++
 3 files changed, 208 insertions(+), 4 deletions(-)
 create mode 100644 changelog.d/792-band-edges-compiled-register.fixed.md

diff --git a/changelog.d/792-band-edges-compiled-register.fixed.md b/changelog.d/792-band-edges-compiled-register.fixed.md
new file mode 100644
index 00000000..afe982e6
--- /dev/null
+++ b/changelog.d/792-band-edges-compiled-register.fixed.md
@@ -0,0 +1 @@
+Banded calibration targets now derive upper edges from the compiled pre-exclusion register, fixing microcosm#792 so excluding a banded target no longer widens its surviving lower neighbour. The materialization seam now refuses a pruned register unless callers provide its compiled band-edge source.
diff --git a/packages/microcosm-build/src/microcosm/build/target_materialization.py b/packages/microcosm-build/src/microcosm/build/target_materialization.py
index 79fdfb22..41468008 100644
--- a/packages/microcosm-build/src/microcosm/build/target_materialization.py
+++ b/packages/microcosm-build/src/microcosm/build/target_materialization.py
@@ -21,9 +21,11 @@
 # encodings are in use — a numeric lower bound (HMRC SPI income bands) and a
 # published range label (DWP award bands, in monthly units, hence
 # ``band_period_factor``) — and both reduce to one lower edge, because no
-# reference anywhere declares an upper bound. A band's upper edge is
-# therefore its sibling's lower edge within the same contract target, and the
-# top band runs to infinity.
+# reference anywhere declares an upper bound. A band's upper edge is its
+# sibling's lower edge within the same compiled contract target. Edges must
+# never derive from an exclusion-pruned roster, or excluding a band silently
+# widens its lower neighbour; only the compiled register's top band runs to
+# infinity.
 # Entity-count indicators: a value of one per record of the owning entity.
 _COUNT_VALUE_VARIABLES = frozenset(
     {"household_count", "person_count", "benunit_count"}
@@ -126,6 +128,7 @@ def resolve_target_measures(
     period: int | str,
     max_rounds: int = 8,
     contract_targets: Mapping[str, Mapping[str, Any]] | None = None,
+    band_edge_registry: TargetRegistry | None = None,
 ) -> MeasureResolution:
     """Resolve provider-computed inputs until target materialization binds.
 
@@ -159,6 +162,7 @@ def resolve_target_measures(
             registry,
             contract,
             period=period,
+            band_edge_registry=band_edge_registry,
         )
         skipped = tuple(result.skipped)
         round_receipt = {
@@ -414,6 +418,13 @@ def _band_bounds(
             f"groupby_variable {binding['groupby_variable']!r} but its spec "
             "carries no readable band edge"
         )
+    if lower not in band_edges:
+        raise ValueError(
+            f"banded measure {getattr(spec, 'measure', '?')!r} carries band lower edge "
+            f"{lower!r} that is absent from its contract target's band-edge set "
+            f"{list(band_edges)!r}; the band-edge register does not cover this spec's "
+            "band — pass the compiled (pre-exclusion) register this spec was pruned from."
+        )
     upper = math.inf
     for edge in band_edges:
         if edge > lower:
@@ -429,11 +440,15 @@ def materialize_target_bindings(
     *,
     period: int | str,
     providers: Mapping[str, Provider] | None = None,
+    band_edge_registry: TargetRegistry | None = None,
 ) -> TargetMaterializationResult:
     """Prepare measure columns declared by compiled Ledger target specs."""
 
     provider_registry = {**default_provider_registry(), **(providers or {})}
-    band_edges = _band_edges_by_group(registry, contract_targets)
+    band_edges = _band_edges_by_group(
+        registry if band_edge_registry is None else band_edge_registry,
+        contract_targets,
+    )
     skipped: list[MaterializationSkip] = []
     for spec in registry.specs:
         if hasattr(adapter, "has_column") and adapter.has_column(
diff --git a/packages/microcosm-build/tests/test_target_materialization.py b/packages/microcosm-build/tests/test_target_materialization.py
index b4af50fb..1d726f3c 100644
--- a/packages/microcosm-build/tests/test_target_materialization.py
+++ b/packages/microcosm-build/tests/test_target_materialization.py
@@ -512,6 +512,63 @@ def test_bands_slice_the_population_and_partition_it():
     assert list(total) == [1.0, 1.0, 1.0]
 
 
+def test_band_measures_are_roster_invariant_under_sibling_exclusion():
+    registry = _banded_registry()
+    full_adapter = StubAdapter()
+
+    result = materialize_target_bindings(
+        full_adapter, registry, _BANDED_CONTRACT, period=2025
+    )
+
+    assert result.skipped == ()
+    snapshots = {
+        label: full_adapter.tables["person"][f"income_band_{label}"].copy()
+        for label in ("0", "20", "40")
+    }
+
+    middle_pruned = TargetRegistry(
+        [spec for spec in registry.specs if spec.name != "band_20"],
+        country="uk",
+    )
+    middle_adapter = StubAdapter()
+
+    result = materialize_target_bindings(
+        middle_adapter,
+        middle_pruned,
+        _BANDED_CONTRACT,
+        period=2025,
+        band_edge_registry=registry,
+    )
+
+    assert result.skipped == ()
+    for label in ("0", "40"):
+        assert np.array_equal(
+            middle_adapter.tables["person"][f"income_band_{label}"],
+            snapshots[label],
+        )
+
+    top_pruned = TargetRegistry(
+        [spec for spec in registry.specs if spec.name != "band_40"],
+        country="uk",
+    )
+    top_adapter = StubAdapter()
+
+    result = materialize_target_bindings(
+        top_adapter,
+        top_pruned,
+        _BANDED_CONTRACT,
+        period=2025,
+        band_edge_registry=registry,
+    )
+
+    assert result.skipped == ()
+    for label in ("0", "20"):
+        assert np.array_equal(
+            top_adapter.tables["person"][f"income_band_{label}"],
+            snapshots[label],
+        )
+
+
 def test_adjacent_bands_are_not_identical():
     # The regression that would have caught the unsliced-measure defect:
     # before banding was implemented every band returned the same unsliced
@@ -582,6 +639,137 @@ def test_published_range_labels_band_in_model_units():
     assert list(adapter.tables["person"]["award_high"]) == [0.0, 0.0, 1.0]
 
 
+def test_published_range_label_edges_survive_sibling_exclusion():
+    registry = TargetRegistry(
+        [
+            TargetSpec(
+                name="award_low",
+                entity="person",
+                measure="award_low",
+                value=1.0,
+                source="test",
+                family="dwp_universal_credit",
+                metadata={
+                    "contract_target_id": "uc.award_bands",
+                    "ledger_filter_family_type": "Single, no children",
+                    "ledger_filter_monthly_award_bands": "£1.01 to £2.00",
+                },
+            ),
+            TargetSpec(
+                name="award_high",
+                entity="person",
+                measure="award_high",
+                value=1.0,
+                source="test",
+                family="dwp_universal_credit",
+                metadata={
+                    "contract_target_id": "uc.award_bands",
+                    "ledger_filter_monthly_award_bands": "£2.01 to £3.00",
+                },
+            ),
+        ],
+        country="uk",
+    )
+    contract = {
+        "uc.award_bands": {
+            "bindings": {
+                "policyengine": {
+                    "value_variable": "person_count",
+                    "groupby_variable": "income",
+                    "from_entity": "person",
+                    "band_period_factor": 12,
+                }
+            }
+        }
+    }
+    pruned = TargetRegistry(
+        [spec for spec in registry.specs if spec.name != "award_high"],
+        country="uk",
+    )
+    adapter = StubAdapter()
+
+    result = materialize_target_bindings(
+        adapter,
+        pruned,
+        contract,
+        period=2025,
+        band_edge_registry=registry,
+    )
+
+    assert result.skipped == ()
+    assert list(adapter.tables["person"]["award_low"]) == [0.0, 1.0, 0.0]
+
+
+def test_band_bounds_refuse_a_spec_absent_from_the_band_edge_register():
+    registry = TargetRegistry([_banded_registry().specs[0]], country="uk")
+    adapter = StubAdapter()
+
+    result = materialize_target_bindings(
+        adapter,
+        registry,
+        _BANDED_CONTRACT,
+        period=2025,
+        band_edge_registry=TargetRegistry([], country="uk"),
+    )
+
+    assert len(result.skipped) == 1
+    assert result.skipped[0].name == "band_0"
+    assert "absent from its contract target's band-edge set" in result.skipped[0].reason
+    assert "income_band_0" not in adapter.tables["person"]
+
+
+def test_resolve_target_measures_threads_the_band_edge_registry():
+    class BandedInputProvider(StubMeasureProvider):
+        def compute(self, entity, variable):
+            assert (entity, variable) == ("person", "input_a")
+            return np.array([1.0, 2.0, 3.0]), "stub:person.input_a"
+
+    source = {
+        "person": pd.DataFrame(
+            {
+                "person_id": [1, 2, 3],
+                "income": [10.0, 20.0, 30.0],
+            }
+        )
+    }
+    registry = _banded_registry()
+    pruned = TargetRegistry(
+        [spec for spec in registry.specs if spec.name != "band_20"],
+        country="uk",
+    )
+    probes = []
+
+    def adapter_factory():
+        adapter = ResolutionAdapter(source)
+        probes.append(adapter)
+        return adapter
+
+    resolution = resolve_target_measures(
+        adapter_factory,
+        pruned,
+        BandedInputProvider(),
+        period=2025,
+        contract_targets={
+            "spi.income_by_band": {
+                "bindings": {
+                    "policyengine": {
+                        "value_variable": "input_a",
+                        "groupby_variable": "income",
+                        "from_entity": "person",
+                    }
+                }
+            }
+        },
+        band_edge_registry=registry,
+    )
+
+    assert resolution.receipt["attached"] == {
+        "person.input_a": "stub:person.input_a"
+    }
+    assert list(probes[-1].tables["person"]["income_band_0"]) == [1.0, 0.0, 0.0]
+    assert list(probes[-1].tables["person"]["income_band_40"]) == [0.0, 0.0, 0.0]
+
+
 def test_unreadable_band_is_skipped_not_silently_unsliced():
     adapter = StubAdapter()
     registry = TargetRegistry(

From 5958bad23a0ddac5207abc1d6348fced97f10bb8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mar=C3=ADa=20Juaristi?=
 <127882282+juaristi22@users.noreply.github.com>
Date: Thu, 27 Aug 2026 17:17:10 +0200
Subject: [PATCH 2/3] Thread the compiled band-edge register through the UK
 calibration seam
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The seam prunes measure exclusions before materialization, so the stage
only ever saw the pruned registry. run_uk_calibration now takes the
compiled pre-exclusion register as band_edge_registry and refuses, before
any artifact is written, a non-empty exclusion receipt without it — and
a register whose extra names do not exactly reconstitute the receipt
(the applier already fails exclusions that match zero specs, so
pruned + receipt == compiled is exact). The registry content hash is
recorded as run_config.band_edge_register_sha256, flowing into the build
record and identity digest. The seam tool passes compilation.registry;
census counts are unchanged — only survivors' measured values return to
published band widths. The stale prose in test_uk_measure_simulation
that read the widening artifact as the resolution mechanism is corrected.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 .../build/uk_runtime/calibration_run.py       |  49 +++++++
 .../build/uk_runtime/ledger_targets.py        |   2 +
 .../build/uk_runtime/national_calibration.py  |   7 +
 .../tests/test_uk_calibration_run.py          | 132 ++++++++++++++++++
 .../tests/test_uk_calibration_seam_driver.py  |   6 +-
 .../tests/test_uk_measure_simulation.py       |   6 +-
 .../tests/test_uk_national_calibration.py     |  38 +++++
 tools/calibrate_uk_national_dataset.py        |   1 +
 8 files changed, 237 insertions(+), 4 deletions(-)

diff --git a/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py b/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py
index 5bb27c48..28fc29ed 100644
--- a/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py
+++ b/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py
@@ -197,6 +197,7 @@ def run_uk_calibration(
     input_sha256: str,
     ledger_artifact: Any,
     register_registry: TargetRegistry,
+    band_edge_registry: TargetRegistry | None = None,
     calibration_year: int,
     exclusion_receipt: Mapping[str, Mapping[str, str]],
     doctrine: Any,
@@ -211,6 +212,15 @@ def run_uk_calibration(
 
     started_at = time.perf_counter()
     started_ts = datetime.now(UTC)
+    # Pure-argument validation precedes every environment probe: a pruned
+    # register without its compiled band-edge source must refuse identically
+    # whether or not a git checkout or Logbook chain is reachable.
+    _validate_band_edge_registry(
+        register_registry=register_registry,
+        band_edge_registry=band_edge_registry,
+        exclusion_receipt=exclusion_receipt,
+    )
+    edge_registry = band_edge_registry or register_registry
     code_pin = git_code_pin(_REPOSITORY)
     # Predecessor configuration is validated before anything is written: a
     # disagreeing chain must refuse with no artifact on disk, not after a
@@ -230,6 +240,7 @@ def run_uk_calibration(
         "ledger": _ledger_provenance(ledger_artifact),
         **dict(run_config_extra),
     }
+    run_config["band_edge_register_sha256"] = edge_registry.version
     state = AttemptState(
         # Attempts are distinct rows even when they re-run one release: both
         # the local chain and the store refuse a repeated build id.
@@ -246,6 +257,7 @@ def run_uk_calibration(
             input_sha256=input_sha256,
             ledger_artifact=ledger_artifact,
             register_registry=register_registry,
+            band_edge_registry=edge_registry,
             calibration_year=calibration_year,
             exclusion_receipt=exclusion_receipt,
             doctrine=doctrine,
@@ -287,6 +299,41 @@ def _new_calibration_attempt_id(*, timestamp: datetime) -> str:
     )
 
 
+def _validate_band_edge_registry(
+    *,
+    register_registry: TargetRegistry,
+    band_edge_registry: TargetRegistry | None,
+    exclusion_receipt: Mapping[str, Mapping[str, str]],
+) -> None:
+    if exclusion_receipt and band_edge_registry is None:
+        raise ValueError(
+            "a pruned register cannot derive published band edges from itself; "
+            "pass the compiled pre-exclusion register."
+        )
+    if band_edge_registry is None:
+        return
+    register_names = _registry_spec_names(register_registry)
+    edge_names = _registry_spec_names(band_edge_registry)
+    excluded_names = {str(name) for name in exclusion_receipt}
+    if not register_names <= edge_names:
+        missing = sorted(register_names - edge_names)
+        raise ValueError(
+            "band-edge register must include every materialized registry spec; "
+            f"missing={missing}."
+        )
+    extra = edge_names - register_names
+    if extra != excluded_names:
+        raise ValueError(
+            "band-edge register extra spec names must match the measure "
+            f"exclusion receipt; extra={sorted(extra)}, "
+            f"receipt={sorted(excluded_names)}."
+        )
+
+
+def _registry_spec_names(registry: TargetRegistry) -> set[str]:
+    return {str(spec.name) for spec in registry.specs}
+
+
 def _record_failed_attempt(
     *,
     error: BaseException,
@@ -336,6 +383,7 @@ def _run_uk_calibration_attempt(
     input_sha256: str,
     ledger_artifact: Any,
     register_registry: TargetRegistry,
+    band_edge_registry: TargetRegistry,
     calibration_year: int,
     exclusion_receipt: Mapping[str, Mapping[str, str]],
     doctrine: Any,
@@ -374,6 +422,7 @@ def _run_uk_calibration_attempt(
         period=calibration_year,
         doctrine=doctrine,
         measure_resolver=measure_resolver,
+        band_edge_registry=band_edge_registry,
     )
     calibrated = stage(frame)
     append_phase(state, "national_calibration_solved")
diff --git a/packages/microcosm-build/src/microcosm/build/uk_runtime/ledger_targets.py b/packages/microcosm-build/src/microcosm/build/uk_runtime/ledger_targets.py
index 7e3608fa..0a1f0493 100644
--- a/packages/microcosm-build/src/microcosm/build/uk_runtime/ledger_targets.py
+++ b/packages/microcosm-build/src/microcosm/build/uk_runtime/ledger_targets.py
@@ -88,6 +88,7 @@ def materialize_uk_ledger_targets(
     registry: TargetRegistry,
     *,
     period: int | str,
+    band_edge_registry: TargetRegistry | None = None,
 ) -> TargetMaterializationResult:
     """Materialize compiled UK Ledger target bindings on an adapter."""
 
@@ -102,6 +103,7 @@ def materialize_uk_ledger_targets(
             "baseline_flag_crosstab": _uk_baseline_flag_crosstab,
             "input_substitution_counterfactual": _uk_input_substitution,
         },
+        band_edge_registry=band_edge_registry,
     )
 
 
diff --git a/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py b/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py
index 4ff938bb..df294ee2 100644
--- a/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py
+++ b/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py
@@ -48,6 +48,7 @@ def __init__(
         period: int,
         doctrine: UKNationalSolveDoctrine = UK_NATIONAL_SOLVE_DOCTRINE,
         measure_resolver: object | None = None,
+        band_edge_registry: TargetRegistry | None = None,
     ) -> None:
         self.compilation = (
             registry
@@ -55,6 +56,9 @@ def __init__(
             else UKLedgerTargetCompilation(registry=registry, unsupported=())
         )
         self.registry = self.compilation.registry
+        self.band_edge_registry = (
+            band_edge_registry if band_edge_registry is not None else self.registry
+        )
         # The materialization period is the declared calibration year the
         # registry was compiled at — never the input frame's base-year
         # time_period, which lags it (survey 2024, calibration 2025).
@@ -90,6 +94,7 @@ def __call__(self, frame: Frame) -> Frame:
             adapter,
             self.registry,
             period=self.period,
+            band_edge_registry=self.band_edge_registry,
         )
         if materialized.skipped:
             skipped = [skip.__dict__ for skip in materialized.skipped]
@@ -209,12 +214,14 @@ def _resolve_measures(self, frame: Frame) -> MeasureResolution | None:
                 lambda: _CalibrationFrameAdapter(frame),
                 self.registry,
                 period=self.period,
+                band_edge_registry=self.band_edge_registry,
             )
         return resolve_target_measures(
             lambda: _CalibrationFrameAdapter(frame),
             self.registry,
             self.measure_resolver,
             period=self.period,
+            band_edge_registry=self.band_edge_registry,
         )
 
     def checkpoint_metadata(self) -> Mapping[str, object]:
diff --git a/packages/microcosm-build/tests/test_uk_calibration_run.py b/packages/microcosm-build/tests/test_uk_calibration_run.py
index 42420d26..96865c3d 100644
--- a/packages/microcosm-build/tests/test_uk_calibration_run.py
+++ b/packages/microcosm-build/tests/test_uk_calibration_run.py
@@ -87,6 +87,16 @@ def _registry():
     )
 
 
+def _paths(tmp_path: Path) -> UKCalibrationRunPaths:
+    return UKCalibrationRunPaths(
+        input_h5=tmp_path / "input.h5",
+        staging_h5=tmp_path / "staged.h5",
+        diagnostics_json=tmp_path / "diagnostics.json",
+        build_record_json=tmp_path / "build_record.json",
+        terminal_gate_json=tmp_path / "terminal_gates.json",
+    )
+
+
 def _sha(path: Path) -> str:
     return hashlib.sha256(path.read_bytes()).hexdigest()
 
@@ -265,6 +275,128 @@ def test_run_uk_calibration_writes_cross_pinned_outputs(monkeypatch, tmp_path: P
     assert result.logbook_spool.exists()
 
 
+def test_run_uk_calibration_refuses_pruned_register_without_band_edge_register(
+    tmp_path: Path,
+):
+    paths = _paths(tmp_path)
+
+    with pytest.raises(ValueError, match="compiled pre-exclusion register"):
+        run_uk_calibration(
+            paths=paths,
+            input_sha256="a" * 64,
+            ledger_artifact=object(),
+            register_registry=_registry(),
+            calibration_year=2025,
+            exclusion_receipt={"excluded.target": {"reason": "reviewed"}},
+            doctrine=UKNationalSolveDoctrine(epochs=1),
+            doctrine_overrides={},
+            measure_resolver=None,
+            source_pins={},
+            run_config_extra={},
+            release_id="pruned-without-edge-register",
+        )
+
+    assert not paths.staging_h5.exists()
+    assert not paths.diagnostics_json.exists()
+    assert not paths.build_record_json.exists()
+
+
+def test_run_uk_calibration_refuses_incoherent_band_edge_register(tmp_path: Path):
+    paths = _paths(tmp_path)
+    edge_registry = TargetRegistry(
+        [
+            *_registry().specs,
+            TargetSpec(
+                name="different.excluded",
+                entity="benunit",
+                measure="different/excluded",
+                value=1.0,
+                source="test",
+                metadata={"contract_target_id": "different.excluded"},
+            ),
+        ],
+        country="uk",
+    )
+
+    with pytest.raises(ValueError, match="exclusion receipt"):
+        run_uk_calibration(
+            paths=paths,
+            input_sha256="a" * 64,
+            ledger_artifact=object(),
+            register_registry=_registry(),
+            band_edge_registry=edge_registry,
+            calibration_year=2025,
+            exclusion_receipt={"other.excluded": {"reason": "reviewed"}},
+            doctrine=UKNationalSolveDoctrine(epochs=1),
+            doctrine_overrides={},
+            measure_resolver=None,
+            source_pins={},
+            run_config_extra={},
+            release_id="incoherent-edge-register",
+        )
+
+    assert not paths.staging_h5.exists()
+    assert not paths.diagnostics_json.exists()
+    assert not paths.build_record_json.exists()
+
+
+def test_run_uk_calibration_records_band_edge_register_sha256(
+    monkeypatch, tmp_path: Path
+):
+    pytest.importorskip("tables")  # pandas HDF backend
+    monkeypatch.setattr(
+        calibration_run,
+        "uk_aggregate_admin_totals",
+        lambda frame, manifest: (_admin_anchor_values(), []),
+    )
+    input_h5 = tmp_path / "input.h5"
+    frame = _frame()
+    write_uk_national_frame(frame, input_h5)
+    _write_spine_sidecar(input_h5, frame)
+    paths = _paths(tmp_path)
+    register = _registry()
+    edge_registry = TargetRegistry(
+        [
+            TargetSpec(
+                name="dwp.uc.households",
+                entity="benunit",
+                measure="dwp/uc/households",
+                value=99.0,
+                source="test",
+                family="dwp_universal_credit",
+                metadata={"contract_target_id": "dwp.uc.households"},
+            )
+        ],
+        country="uk",
+    )
+
+    result = run_uk_calibration(
+        paths=paths,
+        input_sha256=_sha(input_h5),
+        ledger_artifact=object(),
+        register_registry=register,
+        band_edge_registry=edge_registry,
+        calibration_year=2025,
+        exclusion_receipt={},
+        doctrine=UKNationalSolveDoctrine(epochs=5),
+        doctrine_overrides={},
+        measure_resolver=None,
+        source_pins={
+            "input_h5": {
+                "sha256": _sha(input_h5),
+                "size_bytes": input_h5.stat().st_size,
+            }
+        },
+        run_config_extra={},
+        release_id="band-edge-provenance",
+    )
+
+    assert (
+        result.build_record["run_config"]["band_edge_register_sha256"]
+        == edge_registry.version
+    )
+
+
 def test_run_uk_calibration_refuses_input_sha_before_outputs(tmp_path: Path):
     pytest.importorskip("tables")  # pandas HDF backend
     input_h5 = tmp_path / "input.h5"
diff --git a/packages/microcosm-build/tests/test_uk_calibration_seam_driver.py b/packages/microcosm-build/tests/test_uk_calibration_seam_driver.py
index 8ed5850e..f8cf5b3a 100644
--- a/packages/microcosm-build/tests/test_uk_calibration_seam_driver.py
+++ b/packages/microcosm-build/tests/test_uk_calibration_seam_driver.py
@@ -129,6 +129,7 @@ def test_driver_threads_registry_exclusions_resolver_and_overrides(monkeypatch,
     driver = _load_driver_module()
     calls = []
     registry = _registry()
+    pruned_registry = TargetRegistry([], country="uk")
     artifact = SimpleNamespace(
         path=tmp_path / "ledger",
         facts=({"fact": 1},),
@@ -152,7 +153,7 @@ def test_driver_threads_registry_exclusions_resolver_and_overrides(monkeypatch,
     monkeypatch.setattr(
         driver,
         "apply_uk_calibration_measure_exclusions",
-        lambda reg, exclusions: (reg, {"excluded": "reviewed"}),
+        lambda reg, exclusions: (pruned_registry, {"excluded": "reviewed"}),
     )
 
     class FakeResolver:
@@ -183,7 +184,8 @@ def fake_run(**kwargs):
 
     assert result == 0
     call = calls[0]
-    assert call["register_registry"] is registry
+    assert call["register_registry"] is pruned_registry
+    assert call["band_edge_registry"] is registry
     assert call["calibration_year"] == 2025
     assert call["exclusion_receipt"] == {"excluded": "reviewed"}
     assert call["doctrine"].epochs == 128
diff --git a/packages/microcosm-build/tests/test_uk_measure_simulation.py b/packages/microcosm-build/tests/test_uk_measure_simulation.py
index 4e380007..59ba0648 100644
--- a/packages/microcosm-build/tests/test_uk_measure_simulation.py
+++ b/packages/microcosm-build/tests/test_uk_measure_simulation.py
@@ -289,8 +289,10 @@ def test_packaged_exclusions_load():
             assert entry["tracking"] == "microcosm#791", entry["name"]
 
     # The lever targets are deliberately NOT excluded: the six UC
-    # caseload / two-child-limit cells ride the would_claim_uc lever run,
-    # and the two expected-to-resolve cells ride the exclusion re-run.
+    # caseload / two-child-limit cells ride the would_claim_uc lever run.
+    # Exclusions cannot move surviving cells because band edges are pinned
+    # to the compiled register (#792); the non-excluded cells are expected
+    # to pass at published band widths on the next seam run.
     excluded = set(names)
     for riding in (
         "dwp.uc.households",
diff --git a/packages/microcosm-build/tests/test_uk_national_calibration.py b/packages/microcosm-build/tests/test_uk_national_calibration.py
index 1886242e..099c577b 100644
--- a/packages/microcosm-build/tests/test_uk_national_calibration.py
+++ b/packages/microcosm-build/tests/test_uk_national_calibration.py
@@ -21,6 +21,7 @@
     UK_NATIONAL_TARGET_LOSS_CAP,
     UK_NATIONAL_TARGET_WEIGHT_RULE,
     UKNationalSolveDoctrine,
+    national_calibration,
     uk_doctrine_with_overrides,
     uk_national_target_loss_weights,
 )
@@ -372,6 +373,43 @@ def test_stage_manifest_omits_measure_resolution_without_resolver() -> None:
     assert "measure_resolution" not in stage.manifest
 
 
+def test_stage_threads_band_edge_registry_to_materialization(monkeypatch) -> None:
+    captured = []
+    real_materialize = national_calibration.materialize_uk_ledger_targets
+
+    def capture_materialize(*args, **kwargs):
+        captured.append(kwargs)
+        return real_materialize(*args, **kwargs)
+
+    monkeypatch.setattr(
+        national_calibration,
+        "materialize_uk_ledger_targets",
+        capture_materialize,
+    )
+    sentinel = TargetRegistry([], country="uk")
+    stage = UKNationalCalibrationStage(
+        _registry(),
+        period=2025,
+        doctrine=UKNationalSolveDoctrine(epochs=1),
+        band_edge_registry=sentinel,
+    )
+
+    stage(_frame())
+
+    assert captured[-1]["band_edge_registry"] is sentinel
+
+    captured.clear()
+    default_stage = UKNationalCalibrationStage(
+        _registry(),
+        period=2025,
+        doctrine=UKNationalSolveDoctrine(epochs=1),
+    )
+
+    default_stage(_frame())
+
+    assert captured[-1]["band_edge_registry"] is default_stage.registry
+
+
 def test_activated_unresolvable_compiled_reference_aborts_loudly() -> None:
     stage = UKNationalCalibrationStage(
         UKLedgerTargetCompilation(
diff --git a/tools/calibrate_uk_national_dataset.py b/tools/calibrate_uk_national_dataset.py
index 2f969784..c6e2118a 100644
--- a/tools/calibrate_uk_national_dataset.py
+++ b/tools/calibrate_uk_national_dataset.py
@@ -98,6 +98,7 @@ def main(argv: list[str] | None = None) -> int:
         input_sha256=args.input_sha256,
         ledger_artifact=artifact,
         register_registry=registry,
+        band_edge_registry=compilation.registry,
         calibration_year=calibration_year,
         exclusion_receipt=exclusion_receipt,
         doctrine=doctrine,

From 2a445b86c8080c2eee65b508597c0c63c3ad8c4b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mar=C3=ADa=20Juaristi?=
 <127882282+juaristi22@users.noreply.github.com>
Date: Fri, 28 Aug 2026 11:35:39 +0200
Subject: [PATCH 3/3] Disposition the #803 review: required band-edge register,
 refusing coverage fence

Findings 1 and 3 (vahid-ahmadi): band_edge_registry is now REQUIRED at
UKNationalCalibrationStage and run_uk_calibration - never defaulted. The
stage cannot tell a pruned registry from a full one, so the old fallback
to self.registry restated #792 for any direct caller holding a pruned
roster, and gating the run-level check on receipt truthiness let an
empty-but-present receipt skip reconciliation entirely. The
reconciliation now always runs: an empty receipt is a claim that nothing
was pruned, so the rosters must be name-identical. Receipt keys are spec
names by the applier's construction (it raises on zero-match exclusions
and builds the receipt from matched spec names), documented at the check
(finding 4's key-space concern).

Finding 2: the coverage fence in _band_bounds now raises
BandEdgeCoverageError, a RuntimeError the per-spec skip catch does not
swallow - a register that cannot bound a spec is a wrong-register
problem for the whole run, and the target must never quietly drop out of
the solve. The refusal test asserts propagation instead of a skip, and
new tests pin the TypeError on omission and the empty-receipt
reconciliation.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 .../792-band-edges-compiled-register.fixed.md |  2 +-
 .../microcosm/build/target_materialization.py | 13 +++++-
 .../build/uk_runtime/calibration_run.py       | 28 ++++++-----
 .../build/uk_runtime/national_calibration.py  | 10 ++--
 .../tests/test_target_materialization.py      | 25 ++++++----
 .../tests/test_uk_calibration_run.py          | 46 ++++++++++++++++++-
 .../tests/test_uk_national_calibration.py     | 33 +++++++++----
 7 files changed, 117 insertions(+), 40 deletions(-)

diff --git a/changelog.d/792-band-edges-compiled-register.fixed.md b/changelog.d/792-band-edges-compiled-register.fixed.md
index afe982e6..cf46b53f 100644
--- a/changelog.d/792-band-edges-compiled-register.fixed.md
+++ b/changelog.d/792-band-edges-compiled-register.fixed.md
@@ -1 +1 @@
-Banded calibration targets now derive upper edges from the compiled pre-exclusion register, fixing microcosm#792 so excluding a banded target no longer widens its surviving lower neighbour. The materialization seam now refuses a pruned register unless callers provide its compiled band-edge source.
+Banded calibration targets now derive upper edges from the compiled pre-exclusion register, fixing microcosm#792 so excluding a banded target no longer widens its surviving lower neighbour. The band-edge register is a required argument of the UK calibration stage and run seam — never defaulted, always reconciled against the materialized roster and the exclusion receipt (an empty receipt demands name-identical rosters) — and a register that cannot bound a spec refuses the run rather than letting the target drop out of the solve.
diff --git a/packages/microcosm-build/src/microcosm/build/target_materialization.py b/packages/microcosm-build/src/microcosm/build/target_materialization.py
index 41468008..a64f787a 100644
--- a/packages/microcosm-build/src/microcosm/build/target_materialization.py
+++ b/packages/microcosm-build/src/microcosm/build/target_materialization.py
@@ -75,6 +75,17 @@ class MeasureResolution:
     receipt: Mapping[str, Any]
 
 
+class BandEdgeCoverageError(RuntimeError):
+    """A supplied band-edge register does not cover a materialized spec.
+
+    Deliberately not a :class:`ValueError`: the per-spec materialization loop
+    converts ValueErrors into :class:`MaterializationSkip` entries, and a
+    register that cannot bound a spec is a wrong-register problem for the
+    whole run, not a per-spec data defect — it must refuse, never let the
+    target quietly drop out of the solve (#792 review finding 2).
+    """
+
+
 class MeasureResolutionError(RuntimeError):
     """Raised when simulated measure resolution cannot bind the registry."""
 
@@ -419,7 +430,7 @@ def _band_bounds(
             "carries no readable band edge"
         )
     if lower not in band_edges:
-        raise ValueError(
+        raise BandEdgeCoverageError(
             f"banded measure {getattr(spec, 'measure', '?')!r} carries band lower edge "
             f"{lower!r} that is absent from its contract target's band-edge set "
             f"{list(band_edges)!r}; the band-edge register does not cover this spec's "
diff --git a/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py b/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py
index 28fc29ed..6e7cdfcc 100644
--- a/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py
+++ b/packages/microcosm-build/src/microcosm/build/uk_runtime/calibration_run.py
@@ -197,7 +197,7 @@ def run_uk_calibration(
     input_sha256: str,
     ledger_artifact: Any,
     register_registry: TargetRegistry,
-    band_edge_registry: TargetRegistry | None = None,
+    band_edge_registry: TargetRegistry,
     calibration_year: int,
     exclusion_receipt: Mapping[str, Mapping[str, str]],
     doctrine: Any,
@@ -212,15 +212,15 @@ def run_uk_calibration(
 
     started_at = time.perf_counter()
     started_ts = datetime.now(UTC)
-    # Pure-argument validation precedes every environment probe: a pruned
-    # register without its compiled band-edge source must refuse identically
+    # Pure-argument validation precedes every environment probe: an
+    # incoherent register/receipt/band-edge triple must refuse identically
     # whether or not a git checkout or Logbook chain is reachable.
     _validate_band_edge_registry(
         register_registry=register_registry,
         band_edge_registry=band_edge_registry,
         exclusion_receipt=exclusion_receipt,
     )
-    edge_registry = band_edge_registry or register_registry
+    edge_registry = band_edge_registry
     code_pin = git_code_pin(_REPOSITORY)
     # Predecessor configuration is validated before anything is written: a
     # disagreeing chain must refuse with no artifact on disk, not after a
@@ -302,16 +302,20 @@ def _new_calibration_attempt_id(*, timestamp: datetime) -> str:
 def _validate_band_edge_registry(
     *,
     register_registry: TargetRegistry,
-    band_edge_registry: TargetRegistry | None,
+    band_edge_registry: TargetRegistry,
     exclusion_receipt: Mapping[str, Mapping[str, str]],
 ) -> None:
-    if exclusion_receipt and band_edge_registry is None:
-        raise ValueError(
-            "a pruned register cannot derive published band edges from itself; "
-            "pass the compiled pre-exclusion register."
-        )
-    if band_edge_registry is None:
-        return
+    """Require the band-edge register to reconstitute the compiled roster.
+
+    The reconciliation always runs — an empty receipt is a claim that nothing
+    was pruned, so the two rosters must then be name-identical; it is never
+    permission to skip the check. Receipt keys are spec names by the
+    applier's construction: ``apply_uk_calibration_measure_exclusions``
+    builds the receipt from the matched ``spec.name`` set and raises on any
+    exclusion matching zero registry specs, so ``pruned + receipt keys ==
+    compiled`` is an exact identity, not a heuristic.
+    """
+
     register_names = _registry_spec_names(register_registry)
     edge_names = _registry_spec_names(band_edge_registry)
     excluded_names = {str(name) for name in exclusion_receipt}
diff --git a/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py b/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py
index df294ee2..e27be91f 100644
--- a/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py
+++ b/packages/microcosm-build/src/microcosm/build/uk_runtime/national_calibration.py
@@ -48,7 +48,7 @@ def __init__(
         period: int,
         doctrine: UKNationalSolveDoctrine = UK_NATIONAL_SOLVE_DOCTRINE,
         measure_resolver: object | None = None,
-        band_edge_registry: TargetRegistry | None = None,
+        band_edge_registry: TargetRegistry,
     ) -> None:
         self.compilation = (
             registry
@@ -56,9 +56,11 @@ def __init__(
             else UKLedgerTargetCompilation(registry=registry, unsupported=())
         )
         self.registry = self.compilation.registry
-        self.band_edge_registry = (
-            band_edge_registry if band_edge_registry is not None else self.registry
-        )
+        # Required, never defaulted: the stage cannot tell a pruned registry
+        # from a full one, so a fallback to self.registry would quietly
+        # restate #792 for any caller holding an exclusion-pruned roster.
+        # A caller whose registry is unpruned passes it explicitly.
+        self.band_edge_registry = band_edge_registry
         # The materialization period is the declared calibration year the
         # registry was compiled at — never the input frame's base-year
         # time_period, which lags it (survey 2024, calibration 2025).
diff --git a/packages/microcosm-build/tests/test_target_materialization.py b/packages/microcosm-build/tests/test_target_materialization.py
index 1d726f3c..c9865cb9 100644
--- a/packages/microcosm-build/tests/test_target_materialization.py
+++ b/packages/microcosm-build/tests/test_target_materialization.py
@@ -3,6 +3,7 @@
 import pytest
 
 from microcosm.build.target_materialization import (
+    BandEdgeCoverageError,
     MeasureResolutionError,
     assert_calibration_input_finite,
     materialize_target_bindings,
@@ -701,20 +702,24 @@ def test_published_range_label_edges_survive_sibling_exclusion():
 
 
 def test_band_bounds_refuse_a_spec_absent_from_the_band_edge_register():
+    # A register that cannot bound a spec is a wrong-register problem for the
+    # whole run: it must propagate as a refusal, never degrade into a skipped
+    # target that quietly drops out of the solve (#803 review finding 2).
     registry = TargetRegistry([_banded_registry().specs[0]], country="uk")
     adapter = StubAdapter()
 
-    result = materialize_target_bindings(
-        adapter,
-        registry,
-        _BANDED_CONTRACT,
-        period=2025,
-        band_edge_registry=TargetRegistry([], country="uk"),
-    )
+    with pytest.raises(
+        BandEdgeCoverageError,
+        match="absent from its contract target's band-edge set",
+    ):
+        materialize_target_bindings(
+            adapter,
+            registry,
+            _BANDED_CONTRACT,
+            period=2025,
+            band_edge_registry=TargetRegistry([], country="uk"),
+        )
 
-    assert len(result.skipped) == 1
-    assert result.skipped[0].name == "band_0"
-    assert "absent from its contract target's band-edge set" in result.skipped[0].reason
     assert "income_band_0" not in adapter.tables["person"]
 
 
diff --git a/packages/microcosm-build/tests/test_uk_calibration_run.py b/packages/microcosm-build/tests/test_uk_calibration_run.py
index 96865c3d..5781eb77 100644
--- a/packages/microcosm-build/tests/test_uk_calibration_run.py
+++ b/packages/microcosm-build/tests/test_uk_calibration_run.py
@@ -218,6 +218,7 @@ def test_run_uk_calibration_writes_cross_pinned_outputs(monkeypatch, tmp_path: P
         input_sha256=_sha(input_h5),
         ledger_artifact=object(),
         register_registry=_registry(),
+        band_edge_registry=_registry(),
         calibration_year=2025,
         exclusion_receipt={},
         doctrine=UKNationalSolveDoctrine(epochs=5),
@@ -275,12 +276,15 @@ def test_run_uk_calibration_writes_cross_pinned_outputs(monkeypatch, tmp_path: P
     assert result.logbook_spool.exists()
 
 
-def test_run_uk_calibration_refuses_pruned_register_without_band_edge_register(
+def test_run_uk_calibration_requires_the_band_edge_register(
     tmp_path: Path,
 ):
+    # Required, never defaulted: an empty receipt is a claim that nothing was
+    # pruned, not permission to skip the reconciliation, so the seam takes no
+    # register-without-edges path at all (#803 review findings 1 and 3).
     paths = _paths(tmp_path)
 
-    with pytest.raises(ValueError, match="compiled pre-exclusion register"):
+    with pytest.raises(TypeError, match="band_edge_registry"):
         run_uk_calibration(
             paths=paths,
             input_sha256="a" * 64,
@@ -301,6 +305,37 @@ def test_run_uk_calibration_refuses_pruned_register_without_band_edge_register(
     assert not paths.build_record_json.exists()
 
 
+def test_run_uk_calibration_reconciles_an_empty_receipt_as_no_prunes(
+    tmp_path: Path,
+):
+    # A pruned register handed in with an empty receipt must refuse: with
+    # nothing declared excluded, the two rosters have to be name-identical.
+    paths = _paths(tmp_path)
+    full = _registry()
+    pruned = TargetRegistry([], country="uk")
+
+    with pytest.raises(ValueError, match="exclusion receipt"):
+        run_uk_calibration(
+            paths=paths,
+            input_sha256="a" * 64,
+            ledger_artifact=object(),
+            register_registry=pruned,
+            band_edge_registry=full,
+            calibration_year=2025,
+            exclusion_receipt={},
+            doctrine=UKNationalSolveDoctrine(epochs=1),
+            doctrine_overrides={},
+            measure_resolver=None,
+            source_pins={},
+            run_config_extra={},
+            release_id="empty-receipt-pruned-register",
+        )
+
+    assert not paths.staging_h5.exists()
+    assert not paths.diagnostics_json.exists()
+    assert not paths.build_record_json.exists()
+
+
 def test_run_uk_calibration_refuses_incoherent_band_edge_register(tmp_path: Path):
     paths = _paths(tmp_path)
     edge_registry = TargetRegistry(
@@ -414,6 +449,7 @@ def test_run_uk_calibration_refuses_input_sha_before_outputs(tmp_path: Path):
             input_sha256="0" * 64,
             ledger_artifact=object(),
             register_registry=_registry(),
+            band_edge_registry=_registry(),
             calibration_year=2025,
             exclusion_receipt={},
             doctrine=UKNationalSolveDoctrine(epochs=1),
@@ -447,6 +483,7 @@ def test_run_uk_calibration_refuses_absent_input_sidecar(tmp_path: Path):
             input_sha256=_sha(input_h5),
             ledger_artifact=object(),
             register_registry=_registry(),
+            band_edge_registry=_registry(),
             calibration_year=2025,
             exclusion_receipt={},
             doctrine=UKNationalSolveDoctrine(epochs=1),
@@ -499,6 +536,7 @@ def test_run_uk_calibration_refuses_unbound_input_sidecar(
             input_sha256=_sha(input_h5),
             ledger_artifact=object(),
             register_registry=_registry(),
+            band_edge_registry=_registry(),
             calibration_year=2025,
             exclusion_receipt={},
             doctrine=UKNationalSolveDoctrine(epochs=1),
@@ -567,6 +605,7 @@ def test_seam_never_modifies_data_variables(monkeypatch, tmp_path: Path):
         input_sha256=_sha(input_h5),
         ledger_artifact=object(),
         register_registry=pulling_registry,
+        band_edge_registry=pulling_registry,
         calibration_year=2025,
         exclusion_receipt={},
         doctrine=UKNationalSolveDoctrine(epochs=50),
@@ -697,6 +736,7 @@ def test_refusal_records_a_failed_attempt_and_stages_nothing(tmp_path: Path):
             input_sha256="0" * 64,
             ledger_artifact=object(),
             register_registry=_registry(),
+            band_edge_registry=_registry(),
             calibration_year=2025,
             exclusion_receipt={},
             doctrine=UKNationalSolveDoctrine(epochs=1),
@@ -758,6 +798,7 @@ def test_attempt_ids_are_unique_across_reruns_of_one_release(
             input_sha256=_sha(input_h5),
             ledger_artifact=object(),
             register_registry=_registry(),
+            band_edge_registry=_registry(),
             calibration_year=2025,
             exclusion_receipt={},
             doctrine=UKNationalSolveDoctrine(epochs=5),
@@ -809,6 +850,7 @@ def test_verified_ledger_identity_reaches_the_run_evidence(monkeypatch, tmp_path
         input_sha256=_sha(input_h5),
         ledger_artifact=artifact,
         register_registry=_registry(),
+        band_edge_registry=_registry(),
         calibration_year=2025,
         exclusion_receipt={},
         doctrine=UKNationalSolveDoctrine(epochs=5),
diff --git a/packages/microcosm-build/tests/test_uk_national_calibration.py b/packages/microcosm-build/tests/test_uk_national_calibration.py
index 099c577b..58a0a8c2 100644
--- a/packages/microcosm-build/tests/test_uk_national_calibration.py
+++ b/packages/microcosm-build/tests/test_uk_national_calibration.py
@@ -291,6 +291,7 @@ def test_uc_calibration_compiles_and_moves_weighted_count_towards_fact() -> None
     frame = _frame()
     stage = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=200, learning_rate=0.05),
     )
@@ -323,6 +324,7 @@ def test_uc_calibration_stage_accepts_benunit_grain_reference_on_nested_frame()
     frame = _nested_frame()
     stage = UKNationalCalibrationStage(
         _registry(value=60.0),
+        band_edge_registry=_registry(value=60.0),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -343,6 +345,7 @@ def test_stage_measure_resolver_injects_columns_then_restores_pristine_output()
     original_columns = {entity: set(frame.table(entity).columns) for entity in frame.entities}
     stage = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
         measure_resolver=resolver,
@@ -364,6 +367,7 @@ def test_stage_measure_resolver_injects_columns_then_restores_pristine_output()
 def test_stage_manifest_omits_measure_resolution_without_resolver() -> None:
     stage = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -398,16 +402,14 @@ def capture_materialize(*args, **kwargs):
 
     assert captured[-1]["band_edge_registry"] is sentinel
 
-    captured.clear()
-    default_stage = UKNationalCalibrationStage(
-        _registry(),
-        period=2025,
-        doctrine=UKNationalSolveDoctrine(epochs=1),
-    )
-
-    default_stage(_frame())
-
-    assert captured[-1]["band_edge_registry"] is default_stage.registry
+    # The parameter is required, never defaulted: a stage cannot tell a
+    # pruned registry from a full one (#803 review finding 1).
+    with pytest.raises(TypeError, match="band_edge_registry"):
+        UKNationalCalibrationStage(
+            _registry(),
+            period=2025,
+            doctrine=UKNationalSolveDoctrine(epochs=1),
+        )
 
 
 def test_activated_unresolvable_compiled_reference_aborts_loudly() -> None:
@@ -422,6 +424,7 @@ def test_activated_unresolvable_compiled_reference_aborts_loudly() -> None:
                 },
             ),
         ),
+        band_edge_registry=TargetRegistry([], country="uk"),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=1),
     )
@@ -501,6 +504,7 @@ def test_packaged_binding_classes_materialize_through_national_stage() -> None:
     resolver.contract_targets = _uk_contract_targets()
     stage = UKNationalCalibrationStage(
         registry,
+        band_edge_registry=registry,
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=1, learning_rate=0.01),
         measure_resolver=resolver,
@@ -561,6 +565,7 @@ def test_packaged_materialization_skip_aborts_national_stage() -> None:
     )
     stage = UKNationalCalibrationStage(
         registry,
+        band_edge_registry=registry,
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=1),
     )
@@ -573,6 +578,7 @@ def test_calibration_preserves_entity_ids_and_national_integrity() -> None:
     frame = _frame()
     stage = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -589,6 +595,7 @@ def test_checkpoint_metadata_round_trips_calibration_evidence() -> None:
     frame = _frame()
     stage = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -598,6 +605,7 @@ def test_checkpoint_metadata_round_trips_calibration_evidence() -> None:
 
     resumed = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -609,6 +617,7 @@ def test_checkpoint_metadata_round_trips_calibration_evidence() -> None:
 
     drifted = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -617,6 +626,7 @@ def test_checkpoint_metadata_round_trips_calibration_evidence() -> None:
 
     empty = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -634,6 +644,7 @@ def test_checkpoint_metadata_round_trips_calibration_evidence() -> None:
 
     unrun = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -645,6 +656,7 @@ def test_prepared_slash_columns_are_not_returned_to_the_writer(tmp_path) -> None
     pytest.importorskip("tables")
     stage = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5),
     )
@@ -826,6 +838,7 @@ def capturing_calibrate(*args, **kwargs):
     )
     stage = UKNationalCalibrationStage(
         _registry(),
+        band_edge_registry=_registry(),
         period=2025,
         doctrine=UKNationalSolveDoctrine(epochs=5, target_weight_rule=rule),
     )