diff --git a/applications/ara_first_run/handler.py b/applications/ara_first_run/handler.py
index b944227b..c0df86a9 100644
--- a/applications/ara_first_run/handler.py
+++ b/applications/ara_first_run/handler.py
@@ -1,12 +1,36 @@
 from __future__ import annotations
 
+import os
 from typing import Any, Protocol
 
+from sqlmodel import Session
+
 from applications.ara_first_run.ara_first_run_trigger_body import (
     AraFirstRunTriggerBody,
 )
+from domain.baseline.rebaseliner import StubRebaseliner
+from infrastructure.postgres.config import PostgresConfig
+from infrastructure.postgres.engine import make_engine
+from orchestration.baseline_orchestrator import BaselineOrchestrator
 from orchestration.first_run_pipeline import FirstRunPipeline
+from orchestration.ingestion_orchestrator import (
+    EpcFetcher,
+    IngestionOrchestrator,
+    SolarFetcher,
+)
+from orchestration.modelling_orchestrator import ModellingOrchestrator
 from orchestration.task_orchestrator import TaskOrchestrator
+from repositories.baseline.baseline_postgres_repository import (
+    BaselinePostgresRepository,
+)
+from repositories.epc.epc_postgres_repository import EpcPostgresRepository
+from repositories.geospatial.geospatial_repository import GeospatialRepository
+from repositories.materials.materials_repository import MaterialsRepository
+from repositories.property.property_postgres_repository import (
+    PropertyPostgresRepository,
+)
+from repositories.scenario.scenario_repository import ScenarioRepository
+from repositories.solar.solar_postgres_repository import SolarPostgresRepository
 from utilities.aws_lambda.subtask_handler import subtask_handler
 
 
@@ -19,16 +43,79 @@ class _RunsFirstRun(Protocol):
 def dispatch_first_run(body: dict[str, Any], *, pipeline: _RunsFirstRun) -> None:
     """Validate the raw event body and hand the command to the pipeline.
 
-    The handler's entire job — kept as a named seam so it is exercised without
-    the Lambda runtime. No business logic lives here: validate, then delegate
-    (issue #1130).
+    The handler's entire decision logic — kept as a named seam so it is
+    exercised without the Lambda runtime. No business logic lives here: validate,
+    then delegate (issue #1130/#1136).
     """
     trigger = AraFirstRunTriggerBody.model_validate(body)
     pipeline.run(trigger)
 
 
+def build_first_run_pipeline(
+    *,
+    session: Session,
+    epc_fetcher: EpcFetcher,
+    geospatial_repo: GeospatialRepository,
+    solar_fetcher: SolarFetcher,
+) -> FirstRunPipeline:
+    """Compose the real three-stage pipeline over Postgres-backed repos.
+
+    The stages share the session's repos and hand off only ``property_ids``
+    through them (ADR-0011). The source clients are passed in rather than built
+    here because their config is not settled — see ``_source_clients_from_env``.
+    Modelling is stubbed (#1136); its Scenario / Materials ports are seams.
+    """
+    epc_repo = EpcPostgresRepository(session)
+    property_repo = PropertyPostgresRepository(session, epc_repo)
+    solar_repo = SolarPostgresRepository(session)
+    baseline_repo = BaselinePostgresRepository(session)
+    return FirstRunPipeline(
+        ingestion=IngestionOrchestrator(
+            property_repo=property_repo,
+            epc_fetcher=epc_fetcher,
+            geospatial_repo=geospatial_repo,
+            solar_fetcher=solar_fetcher,
+            epc_repo=epc_repo,
+            solar_repo=solar_repo,
+        ),
+        baseline=BaselineOrchestrator(
+            property_repo=property_repo,
+            rebaseliner=StubRebaseliner(),
+            baseline_repo=baseline_repo,
+        ),
+        modelling=ModellingOrchestrator(
+            scenario_repo=ScenarioRepository(),
+            materials_repo=MaterialsRepository(),
+        ),
+    )
+
+
+def _source_clients_from_env() -> tuple[EpcFetcher, GeospatialRepository, SolarFetcher]:
+    """The Ingestion source clients — EPC API, Google Solar, geospatial S3.
+
+    TODO(deploy): their config (EPC auth token, Google Solar API key, geospatial
+    S3 parquet reader), env-var names, and the pandas/s3fs runtime deps are not
+    settled — that wiring is a separate Terraform piece, out of scope for #1136.
+    Raises until then so the lambda fails loudly rather than half-running.
+    """
+    raise NotImplementedError(
+        "ara_first_run source-client wiring (EPC / Google Solar / geospatial) "
+        "is pending the deploy/Terraform piece; see #1136."
+    )
+
+
 @subtask_handler()
 def handler(
     body: dict[str, Any], context: Any, task_orchestrator: TaskOrchestrator
 ) -> None:
-    dispatch_first_run(body, pipeline=FirstRunPipeline())
+    engine = make_engine(PostgresConfig.from_env(dict(os.environ)))
+    epc_fetcher, geospatial_repo, solar_fetcher = _source_clients_from_env()
+    with Session(engine) as session:
+        pipeline = build_first_run_pipeline(
+            session=session,
+            epc_fetcher=epc_fetcher,
+            geospatial_repo=geospatial_repo,
+            solar_fetcher=solar_fetcher,
+        )
+        dispatch_first_run(body, pipeline=pipeline)
+        session.commit()
diff --git a/orchestration/first_run_pipeline.py b/orchestration/first_run_pipeline.py
index 1fd8839b..3d642d9e 100644
--- a/orchestration/first_run_pipeline.py
+++ b/orchestration/first_run_pipeline.py
@@ -23,14 +23,48 @@ class FirstRunCommand(Protocol):
     def scenario_ids(self) -> list[int]: ...
 
 
-class FirstRunPipeline:
-    """Composes the First Run stages end-to-end (Ingestion -> Baseline ->
-    Modelling), threading only ``property_ids`` between them through repos
-    (ADR-0011).
+class IngestionStage(Protocol):
+    """Stage 1 — acquires and persists each Property's external source data."""
 
-    Stub at this stage (#1130): ``run`` simply receives the validated command.
-    The real three-stage composition lands in #1136.
+    def run(self, property_ids: list[int]) -> None: ...
+
+
+class BaselineStage(Protocol):
+    """Stage 2 — establishes each Property's Baseline Performance."""
+
+    def run(self, property_ids: list[int]) -> None: ...
+
+
+class ModellingStage(Protocol):
+    """Stage 3 — scores each Property against its Scenarios into Plans."""
+
+    def run(self, property_ids: list[int], scenario_ids: list[int]) -> None: ...
+
+
+class FirstRunPipeline:
+    """Composes the First Run stages end-to-end: Ingestion -> Baseline ->
+    Modelling.
+
+    Threads **only** ``property_ids`` between stages (and ``scenario_ids`` into
+    Modelling, off the command — not a prior stage). The stages communicate
+    through repos, never via in-memory hand-off, which is what makes each stage
+    independently runnable for the single-property review flow (ADR-0011,
+    ADR-0003). Stage orchestrators are injected so the handler owns wiring and
+    tests substitute fakes.
     """
 
+    def __init__(
+        self,
+        *,
+        ingestion: IngestionStage,
+        baseline: BaselineStage,
+        modelling: ModellingStage,
+    ) -> None:
+        self._ingestion = ingestion
+        self._baseline = baseline
+        self._modelling = modelling
+
     def run(self, command: FirstRunCommand) -> None:
-        return None
+        self._ingestion.run(command.property_ids)
+        self._baseline.run(command.property_ids)
+        self._modelling.run(command.property_ids, command.scenario_ids)
diff --git a/orchestration/modelling_orchestrator.py b/orchestration/modelling_orchestrator.py
new file mode 100644
index 00000000..48f70b19
--- /dev/null
+++ b/orchestration/modelling_orchestrator.py
@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from repositories.materials.materials_repository import MaterialsRepository
+from repositories.scenario.scenario_repository import ScenarioRepository
+
+
+class ModellingOrchestrator:
+    """Stage 3 — scores each baselined Property against its Scenarios, producing
+    Recommendations -> an Optimised Package per Scenario Phase -> Plans
+    (CONTEXT.md: Modelling).
+
+    Stub at this stage (#1136): ``run`` reads its inputs through repos (it takes
+    only ``property_ids`` + ``scenario_ids``, never an in-memory hand-off from
+    Baseline) but does no scoring yet. Full Modelling lands via later TDD slices
+    + per-service grills. The Scenario / Materials repos are injected now so the
+    composition and wiring are real even while the body is empty.
+    """
+
+    def __init__(
+        self,
+        *,
+        scenario_repo: ScenarioRepository,
+        materials_repo: MaterialsRepository,
+    ) -> None:
+        self._scenario_repo = scenario_repo
+        self._materials_repo = materials_repo
+
+    def run(self, property_ids: list[int], scenario_ids: list[int]) -> None:
+        return None
diff --git a/repositories/materials/__init__.py b/repositories/materials/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/repositories/materials/materials_repository.py b/repositories/materials/materials_repository.py
new file mode 100644
index 00000000..5d94f166
--- /dev/null
+++ b/repositories/materials/materials_repository.py
@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+from abc import ABC
+
+
+class MaterialsRepository(ABC):
+    """Loads the retrofit Materials catalogue the Modelling stage draws measures
+    and costs from.
+
+    Seam only at this stage (#1136): the method shape is deferred to the
+    Modelling per-service grill. Declared now so the pipeline can be composed
+    end-to-end with Modelling stubbed.
+    """
diff --git a/repositories/scenario/__init__.py b/repositories/scenario/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/repositories/scenario/scenario_repository.py b/repositories/scenario/scenario_repository.py
new file mode 100644
index 00000000..f560db14
--- /dev/null
+++ b/repositories/scenario/scenario_repository.py
@@ -0,0 +1,14 @@
+from __future__ import annotations
+
+from abc import ABC
+
+
+class ScenarioRepository(ABC):
+    """Loads the Scenarios (and Scenario Snapshots) the Modelling stage scores
+    a Property against.
+
+    Seam only at this stage (#1136): the method shape is deferred to the
+    Modelling per-service grill, where Scenario / Scenario Phase / Scenario
+    Snapshot are designed (CONTEXT.md). Declared now so the pipeline can be
+    composed end-to-end with Modelling stubbed.
+    """
diff --git a/tests/orchestration/test_first_run_pipeline.py b/tests/orchestration/test_first_run_pipeline.py
index 4b685bb2..705282ee 100644
--- a/tests/orchestration/test_first_run_pipeline.py
+++ b/tests/orchestration/test_first_run_pipeline.py
@@ -14,16 +14,51 @@ class _FakeCommand:
     scenario_ids: list[int]
 
 
-def test_run_accepts_the_validated_command() -> None:
+class _SpyIngestion:
+    def __init__(self, log: list[tuple[object, ...]]) -> None:
+        self._log = log
+
+    def run(self, property_ids: list[int]) -> None:
+        self._log.append(("ingestion", property_ids))
+
+
+class _SpyBaseline:
+    def __init__(self, log: list[tuple[object, ...]]) -> None:
+        self._log = log
+
+    def run(self, property_ids: list[int]) -> None:
+        self._log.append(("baseline", property_ids))
+
+
+class _SpyModelling:
+    def __init__(self, log: list[tuple[object, ...]]) -> None:
+        self._log = log
+
+    def run(self, property_ids: list[int], scenario_ids: list[int]) -> None:
+        self._log.append(("modelling", property_ids, scenario_ids))
+
+
+def test_run_sequences_the_three_stages_threading_only_property_ids() -> None:
     # Arrange
+    log: list[tuple[object, ...]] = []
     command: FirstRunCommand = _FakeCommand(
-        portfolio_id=42, property_ids=[101, 102], scenario_ids=[7]
+        portfolio_id=1, property_ids=[10, 11], scenario_ids=[7]
+    )
+    pipeline = FirstRunPipeline(
+        ingestion=_SpyIngestion(log),
+        baseline=_SpyBaseline(log),
+        modelling=_SpyModelling(log),
     )
-    pipeline = FirstRunPipeline()
 
     # Act
-    result = pipeline.run(command)
+    pipeline.run(command)
 
-    # Assert — the stub simply receives the command; full Ingestion -> Baseline
-    # -> Modelling composition lands in #1136.
-    assert result is None
+    # Assert — Ingestion -> Baseline -> Modelling, in order. Ingestion and
+    # Baseline receive only property_ids; Modelling additionally gets the
+    # scenario_ids (off the command, not a prior stage). Nothing else is
+    # threaded between stages — they communicate through repos (ADR-0011).
+    assert log == [
+        ("ingestion", [10, 11]),
+        ("baseline", [10, 11]),
+        ("modelling", [10, 11], [7]),
+    ]
diff --git a/tests/orchestration/test_first_run_pipeline_integration.py b/tests/orchestration/test_first_run_pipeline_integration.py
new file mode 100644
index 00000000..55ca34ed
--- /dev/null
+++ b/tests/orchestration/test_first_run_pipeline_integration.py
@@ -0,0 +1,183 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Any, Optional
+
+from datatypes.epc.domain.epc import Epc
+from datatypes.epc.domain.epc_property_data import (
+    EpcPropertyData,
+    RenewableHeatIncentive,
+)
+from domain.baseline.rebaseliner import StubRebaseliner
+from domain.geospatial.coordinates import Coordinates
+from domain.property.property import Property, PropertyIdentity
+from orchestration.baseline_orchestrator import BaselineOrchestrator
+from orchestration.first_run_pipeline import FirstRunPipeline
+from orchestration.ingestion_orchestrator import IngestionOrchestrator
+from orchestration.modelling_orchestrator import ModellingOrchestrator
+from repositories.baseline.baseline_repository import BaselineRepository
+from repositories.epc.epc_repository import EpcRepository
+from repositories.geospatial.geospatial_repository import GeospatialRepository
+from repositories.materials.materials_repository import MaterialsRepository
+from repositories.property.property_repository import PropertyRepository
+from repositories.scenario.scenario_repository import ScenarioRepository
+from repositories.solar.solar_repository import SolarRepository
+from domain.baseline.baseline_performance import BaselinePerformance
+
+
+@dataclass
+class _FakeCommand:
+    portfolio_id: int
+    property_ids: list[int]
+    scenario_ids: list[int]
+
+
+class _SharedEpcRepo(EpcRepository):
+    """Stands in for the persisted EPC slice both stages talk through."""
+
+    def __init__(self) -> None:
+        self._by_property: dict[int, EpcPropertyData] = {}
+
+    def save(
+        self,
+        data: EpcPropertyData,
+        property_id: Optional[int] = None,
+        portfolio_id: Optional[int] = None,
+    ) -> int:
+        assert property_id is not None
+        self._by_property[property_id] = data
+        return property_id
+
+    def get(self, epc_property_id: int) -> EpcPropertyData:  # pragma: no cover
+        raise NotImplementedError
+
+    def get_for_property(self, property_id: int) -> Optional[EpcPropertyData]:
+        return self._by_property.get(property_id)
+
+
+class _RepoBackedPropertyRepo(PropertyRepository):
+    """Composes the Property from its identity row + the EPC slice in the shared
+    EPC repo — mirroring PropertyPostgresRepository, so the stages genuinely
+    hand off through repo state, not in memory."""
+
+    def __init__(
+        self, identities: dict[int, PropertyIdentity], epc_repo: _SharedEpcRepo
+    ) -> None:
+        self._identities = identities
+        self._epc_repo = epc_repo
+
+    def get(self, property_id: int) -> Property:
+        return Property(
+            identity=self._identities[property_id],
+            epc=self._epc_repo.get_for_property(property_id),
+        )
+
+
+class _FakeEpcFetcher:
+    def __init__(self, epc: EpcPropertyData) -> None:
+        self._epc = epc
+
+    def get_by_uprn(self, uprn: int) -> Optional[EpcPropertyData]:
+        return self._epc
+
+
+class _NoCoordinatesGeospatialRepo(GeospatialRepository):
+    def coordinates_for(self, uprn: int) -> Optional[Coordinates]:
+        return None  # skip the solar leg — not under test here
+
+
+class _FakeSolarFetcher:
+    def get_building_insights(
+        self, longitude: float, latitude: float
+    ) -> dict[str, Any]:  # pragma: no cover
+        return {}
+
+
+class _FakeSolarRepo(SolarRepository):
+    def save(self, property_id: int, insights: dict[str, Any]) -> None:  # pragma: no cover
+        return None
+
+    def get(self, property_id: int) -> Optional[dict[str, Any]]:  # pragma: no cover
+        raise NotImplementedError
+
+
+class _CollectingBaselineRepo(BaselineRepository):
+    def __init__(self) -> None:
+        self.saved: list[tuple[BaselinePerformance, int]] = []
+
+    def save(self, baseline: BaselinePerformance, property_id: int) -> int:
+        self.saved.append((baseline, property_id))
+        return len(self.saved)
+
+    def get_for_property(
+        self, property_id: int
+    ) -> Optional[BaselinePerformance]:  # pragma: no cover
+        raise NotImplementedError
+
+
+class _FakeScenarioRepo(ScenarioRepository):
+    pass
+
+
+class _FakeMaterialsRepo(MaterialsRepository):
+    pass
+
+
+def _ingestible_epc() -> EpcPropertyData:
+    epc = object.__new__(EpcPropertyData)
+    epc.energy_rating_current = 72
+    epc.current_energy_efficiency_band = Epc.C
+    epc.co2_emissions_current = 1.8
+    epc.energy_consumption_current = 180
+    epc.sap_version = 10.2
+    epc.renewable_heat_incentive = RenewableHeatIncentive(
+        space_heating_kwh=5000.0, water_heating_kwh=2000.0
+    )
+    return epc
+
+
+def test_baseline_reads_the_epc_ingestion_persisted_through_repos() -> None:
+    # Arrange — one property; the EPC the fetcher returns is what Ingestion
+    # persists and Baseline must then read back through the shared repo.
+    epc = _ingestible_epc()
+    epc_repo = _SharedEpcRepo()
+    identities = {
+        10: PropertyIdentity(
+            portfolio_id=1, postcode="A0 0AA", address="1 Some Street", uprn=123
+        )
+    }
+    property_repo = _RepoBackedPropertyRepo(identities, epc_repo)
+    baseline_repo = _CollectingBaselineRepo()
+
+    pipeline = FirstRunPipeline(
+        ingestion=IngestionOrchestrator(
+            property_repo=property_repo,
+            epc_fetcher=_FakeEpcFetcher(epc),
+            geospatial_repo=_NoCoordinatesGeospatialRepo(),
+            solar_fetcher=_FakeSolarFetcher(),
+            epc_repo=epc_repo,
+            solar_repo=_FakeSolarRepo(),
+        ),
+        baseline=BaselineOrchestrator(
+            property_repo=property_repo,
+            rebaseliner=StubRebaseliner(),
+            baseline_repo=baseline_repo,
+        ),
+        modelling=ModellingOrchestrator(
+            scenario_repo=_FakeScenarioRepo(),
+            materials_repo=_FakeMaterialsRepo(),
+        ),
+    )
+
+    # Act
+    pipeline.run(_FakeCommand(portfolio_id=1, property_ids=[10], scenario_ids=[7]))
+
+    # Assert — a Baseline Performance landed for property 10, its Lodged half
+    # read off the very EPC Ingestion persisted. Only property_ids crossed the
+    # stage boundary; the EPC itself travelled through the repo.
+    assert len(baseline_repo.saved) == 1
+    baseline, property_id = baseline_repo.saved[0]
+    assert property_id == 10
+    assert baseline.lodged.sap_score == 72
+    assert baseline.lodged.epc_band == Epc.C
+    assert baseline.space_heating_kwh == 5000.0