From caa0847b70af6a853138f757acaabce16b99126f Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Thu, 9 Jul 2026 11:44:31 +0000
Subject: [PATCH] =?UTF-8?q?Scenario=20carries=20its=20Fabric=20First=20fla?=
 =?UTF-8?q?g=20from=20the=20scenario=20table=20=F0=9F=9F=A5?=
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Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 domain/modelling/scenario.py                  |  8 ++++++-
 .../postgres/modelling/scenario_table.py      |  3 +++
 .../test_scenario_postgres_repository.py      | 22 +++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/domain/modelling/scenario.py b/domain/modelling/scenario.py
index 6792e268d..85162d6d0 100644
--- a/domain/modelling/scenario.py
+++ b/domain/modelling/scenario.py
@@ -26,7 +26,12 @@ class Scenario:
 
     `exclusions` are the measure types the brief bars from the run (the only
     measure-scoping the live ``scenario`` table persists — there is no
-    inclusions column). Empty means nothing is barred."""
+    inclusions column). Empty means nothing is barred.
+
+    `fabric_first` constrains the Optimiser to treat the building envelope
+    first: fabric measures are optimised with the full budget, and heating /
+    renewables are only considered on top of the committed fabric when the
+    fabric alone does not meet the brief's target."""
 
     id: int
     goal: str
@@ -34,6 +39,7 @@ class Scenario:
     budget: Optional[float]
     is_default: bool
     exclusions: frozenset[MeasureType] = _NO_EXCLUSIONS
+    fabric_first: bool = False
 
     def considered_measures(self) -> Optional[frozenset[MeasureType]]:
         """The measure-type allowlist the Scenario's exclusions imply: every
diff --git a/infrastructure/postgres/modelling/scenario_table.py b/infrastructure/postgres/modelling/scenario_table.py
index 5f7197bae..5d434b3be 100644
--- a/infrastructure/postgres/modelling/scenario_table.py
+++ b/infrastructure/postgres/modelling/scenario_table.py
@@ -78,6 +78,9 @@ class ScenarioModel(SQLModel, table=True):
     exclusions: Optional[str] = Field(default=None)
     multi_plan: bool = False
     is_default: bool = False
+    # Fabric First constraint (owned by the FE Drizzle schema: boolean NOT
+    # NULL DEFAULT false — do not deploy this mirror before that migration).
+    fabric_first: bool = False
 
     # Portfolio-level aggregates stored against the Scenario.
     cost: Optional[float] = Field(default=None)
diff --git a/tests/repositories/scenario/test_scenario_postgres_repository.py b/tests/repositories/scenario/test_scenario_postgres_repository.py
index 8b5804c7d..6fc537fe1 100644
--- a/tests/repositories/scenario/test_scenario_postgres_repository.py
+++ b/tests/repositories/scenario/test_scenario_postgres_repository.py
@@ -142,6 +142,28 @@ def test_get_many_raises_on_an_exclusion_that_is_not_a_measure_type(
             ScenarioPostgresRepository(session).get_many([7])
 
 
+def test_get_many_maps_the_fabric_first_flag(db_engine: Engine) -> None:
+    # Arrange — a Fabric First brief created in the scenario-builder.
+    with Session(db_engine) as session:
+        session.add(
+            ScenarioModel(
+                id=7,
+                goal=PortfolioGoal.INCREASING_EPC,
+                goal_value="C",
+                is_default=True,
+                fabric_first=True,
+            )
+        )
+        session.commit()
+
+    # Act
+    with Session(db_engine) as session:
+        scenario: Scenario = ScenarioPostgresRepository(session).get_many([7])[0]
+
+    # Assert
+    assert scenario.fabric_first is True
+
+
 def test_get_many_raises_when_a_scenario_id_is_missing(db_engine: Engine) -> None:
     # Arrange
     with Session(db_engine) as session: