diff --git a/packages/populace-build/src/populace/build/source_manifest.py b/packages/populace-build/src/populace/build/source_manifest.py
index 7deaa798..808809de 100644
--- a/packages/populace-build/src/populace/build/source_manifest.py
+++ b/packages/populace-build/src/populace/build/source_manifest.py
@@ -36,8 +36,12 @@
 ALLOWED_SOURCE_OPERATION_KINDS = frozenset(
     {
         "aggregate_person_to_household",
+        "aggregate_person_to_tax_unit",
         "assign_by_plan_type",
+        "assign_binary_from_rate",
+        "calibrate_binary_assignment",
         "convert_interest_to_structural_mortgage_inputs",
+        "compute_ratio",
         "derive",
         "derive_mortgage_balance_hints",
         "disaggregate_aggregate_records",
diff --git a/packages/populace-build/src/populace/build/us/__init__.py b/packages/populace-build/src/populace/build/us/__init__.py
index 4a698e6e..9b89fc91 100644
--- a/packages/populace-build/src/populace/build/us/__init__.py
+++ b/packages/populace-build/src/populace/build/us/__init__.py
@@ -219,6 +219,16 @@ def to_manifest(self) -> dict[str, object]:
         source="https://meps.ahrq.gov/mepsweb/survey_comp/Insurance.jsp",
         notes="Employer-sponsored insurance premium parameters.",
     ),
+    "aca_marketplace_inputs": DonorSpec(
+        survey="CPS ASEC + CMS Marketplace Open Enrollment PUFs",
+        source="https://www.cms.gov/marketplace/resources/data/public-use-files",
+        notes=(
+            "Marketplace take-up and selected-plan inputs: CPS reported "
+            "Marketplace coverage and premium reports anchor the records; "
+            "CMS OEP enrollment, APTC, and metal-level tables provide the "
+            "calibration targets."
+        ),
+    ),
     "prior_year_income": DonorSpec(
         survey="CPS ASEC (prior year)",
         source="https://www.census.gov/programs-surveys/cps.html",
@@ -266,6 +276,7 @@ def to_manifest(self) -> dict[str, object]:
     "acs_rent",
     "vehicle_assets",
     "entity_placement",
+    "aca_marketplace_inputs",
     "export",
 )
 
diff --git a/packages/populace-build/src/populace/build/us/source_stages.json b/packages/populace-build/src/populace/build/us/source_stages.json
index c95855f2..3e8954cd 100644
--- a/packages/populace-build/src/populace/build/us/source_stages.json
+++ b/packages/populace-build/src/populace/build/us/source_stages.json
@@ -479,6 +479,85 @@
         "household_vehicles_owned",
         "household_vehicles_value"
       ]
+    },
+    {
+      "stage": "aca_marketplace_inputs",
+      "survey": "CPS ASEC + CMS Marketplace Open Enrollment PUFs",
+      "source": "https://www.cms.gov/marketplace/resources/data/public-use-files",
+      "grain": "tax_unit",
+      "artifacts": [
+        {
+          "kind": "public_microdata",
+          "format": "census_asec",
+          "vintage": "build_year",
+          "locator": "CPS ASEC current coverage and health premium fields"
+        },
+        {
+          "kind": "administrative_table",
+          "format": "cms_public_use_file",
+          "vintage": "build_year_or_latest_available",
+          "locator": "CMS Marketplace OEP state-level, APTC, and metal-level public use files"
+        }
+      ],
+      "operations": [
+        {
+          "kind": "aggregate_person_to_tax_unit",
+          "aggregates": [
+            "has_marketplace_health_coverage_at_interview",
+            "reported_has_subsidized_marketplace_health_coverage_at_interview"
+          ],
+          "operation": "any"
+        },
+        {
+          "kind": "assign_binary_from_rate",
+          "output": "takes_up_aca_if_eligible",
+          "draw": "stable_tax_unit_draw",
+          "rate_key": "aca",
+          "reported_true_anchor": "reported_has_subsidized_marketplace_health_coverage_at_interview"
+        },
+        {
+          "kind": "calibrate_binary_assignment",
+          "variable": "takes_up_aca_if_eligible",
+          "targets": [
+            "cms_aca_aptc_recipients_by_state",
+            "cms_aca_marketplace_enrollment_by_state"
+          ],
+          "preserve_true_anchors": true
+        },
+        {
+          "kind": "compute_ratio",
+          "output": "selected_marketplace_plan_benchmark_ratio",
+          "numerator": [
+            "health_insurance_premiums_without_medicare_part_b",
+            "assigned_aca_ptc"
+          ],
+          "denominator": "slcsp",
+          "where": "takes_up_aca_if_eligible"
+        },
+        {
+          "kind": "support_clip",
+          "output": "selected_marketplace_plan_benchmark_ratio",
+          "lower": 0.5,
+          "upper": 1.5,
+          "range": "reviewed_marketplace_plan_ratio"
+        },
+        {
+          "kind": "calibrate_binary_assignment",
+          "variable": "selected_marketplace_plan_benchmark_ratio < 1.0",
+          "targets": [
+            "cms_aca_bronze_aptc_consumers_by_state"
+          ],
+          "domain": "assigned_aca_ptc > 0"
+        }
+      ],
+      "outputs": [
+        "takes_up_aca_if_eligible",
+        "selected_marketplace_plan_benchmark_ratio"
+      ],
+      "nonnegative_outputs": [
+        "selected_marketplace_plan_benchmark_ratio"
+      ],
+      "notes": "When PolicyEngine-US separates observed Marketplace coverage from simulated take-up, this stage should write the simulated take-up input while reported coverage remains a CPS-carried person-level input."
     }
   ]
 }
diff --git a/packages/populace-build/tests/test_us_plan.py b/packages/populace-build/tests/test_us_plan.py
index fd9fd693..6af9c8f5 100644
--- a/packages/populace-build/tests/test_us_plan.py
+++ b/packages/populace-build/tests/test_us_plan.py
@@ -212,6 +212,24 @@ def test_puf_stage_disaggregates_aggregate_records_before_uprating(self) -> None
         }
         assert "forbes" not in str(operation.parameters).lower()
 
+    def test_aca_stage_declares_marketplace_input_surface(self) -> None:
+        stage = US_SOURCE_MANIFEST.stage_map()["aca_marketplace_inputs"]
+        outputs = set(stage.outputs)
+        assert stage.grain == "tax_unit"
+        assert "takes_up_aca_if_eligible" in outputs
+        assert "selected_marketplace_plan_benchmark_ratio" in outputs
+        assert any(
+            operation.kind == "calibrate_binary_assignment"
+            and operation.parameters.get("variable") == "takes_up_aca_if_eligible"
+            for operation in stage.operations
+        )
+        assert any(
+            operation.kind == "compute_ratio"
+            and operation.parameters.get("output")
+            == "selected_marketplace_plan_benchmark_ratio"
+            for operation in stage.operations
+        )
+
     def test_no_incumbent_data_package_references_in_live_tree(self) -> None:
         forbidden = (
             "policyengine_" + "us_data",