Implement client cost attribution

.custodian-brief.md

@@ -2,20 +2,19 @@
 # Custodian Brief — fin-hub
 
 **Domain:** financials  
-**Last synced:** 2026-08-10 18:08 UTC  
+**Last synced:** 2026-08-10 18:32 UTC  
 **State Hub:** http://127.0.0.1:8000 *(adjust if running on a remote machine)*
 
 ## Active Workstreams
 
 ### Client attribution and billing basis
-Progress: 1/6 done  |  workplan_id: `ebc1d2de-ae11-4cde-b860-047922fc74b9`
+Progress: 2/6 done  |  workplan_id: `ebc1d2de-ae11-4cde-b860-047922fc74b9`
 
 **Open tasks:**
-- ! Add engagement revenue and margin reporting  `f917bb0b`
 - ! Define shared-infrastructure allocation  `899a5c29`
 - ! Export a per-client billing basis  `b5886131`
 - ! Select the external invoicing system  `d30b606f`
-- · Add client attribution  `904e9edc`
+- · Add engagement revenue and margin reporting  `f917bb0b`
 
 ---
 ## MCP Orientation (when available)

README.md

@@ -32,8 +32,22 @@ uv run finhub ops-costs tests/fixtures/hosteurope.csv
 Cross-hub coupling (`--emit`) posts non-secret progress events to dev-hub when
 `STATE_HUB_API` is reachable.
 
+## Client cost attribution
+
+HostEurope CSV rows may include `client_id`, `application_id`, and
+`app_instance_id`. All three must be present together. Fin-hub validates them
+as external identifiers and derives the stable key
+`client:<client_id>|app:<application_id>|instance:<app_instance_id>`; callers
+must not invent a second key format. Rows without all three columns remain
+explicitly unattributed for backward compatibility.
+
+The SQLite ledger adds the attribution columns automatically when an existing
+ledger is opened. The `ops-costs` report retains its per-service view and adds
+an `attributions` view separated by currency. Client and application identity
+remain authoritative outside fin-hub.
+
 ## Related Workplans
 
 - `the-custodian/workplans/CUST-WP-0025-fos-hub-bootstrap.md` — umbrella
 - `canon/constitution/bootstrap-protocol_v0.1.md` — funding and roles
-- `canon/projects/railiance/business-model-canvas_v0.1.md` — monetization path
+- `canon/projects/railiance/business-model-canvas_v0.1.md` — monetization path

WORK-RECORDS.md

@@ -24,8 +24,8 @@
 | task | FIN-WP-0001-T05 | done | — | workplans/FIN-WP-0001-runway-operations-lane.md |
 | task | FIN-WP-0001-T06 | done | — | workplans/FIN-WP-0001-runway-operations-lane.md |
 | task | FIN-WP-0002-T00 | done | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |
-| task | FIN-WP-0002-T01 | todo | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |
-| task | FIN-WP-0002-T02 | wait | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |
+| task | FIN-WP-0002-T01 | done | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |
+| task | FIN-WP-0002-T02 | todo | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |
 | task | FIN-WP-0002-T03 | wait | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |
 | task | FIN-WP-0002-T04 | wait | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |
 | task | FIN-WP-0002-T05 | wait | — | workplans/FIN-WP-0002-client-attribution-and-billing-basis.md |

src/fin_hub/attribution.py

@@ -0,0 +1,59 @@
+"""Stable external client/application/instance attribution keys."""
+
+from __future__ import annotations
+
+import re
+from dataclasses import dataclass
+
+_PART_PATTERN = re.compile(r"^[A-Za-z0-9][A-Za-z0-9._:-]{0,127}$")
+
+
+def _validate_part(name: str, value: str) -> str:
+    normalized = value.strip()
+    if not _PART_PATTERN.fullmatch(normalized):
+        raise ValueError(
+            f"{name} must be 1-128 characters using letters, digits, '.', '_', ':', or '-'"
+        )
+    return normalized
+
+
+@dataclass(frozen=True)
+class ClientAttribution:
+    """External identity seam; fin-hub does not own these identities."""
+
+    client_id: str
+    application_id: str
+    app_instance_id: str
+
+    def __post_init__(self) -> None:
+        object.__setattr__(self, "client_id", _validate_part("client_id", self.client_id))
+        object.__setattr__(
+            self, "application_id", _validate_part("application_id", self.application_id)
+        )
+        object.__setattr__(
+            self, "app_instance_id", _validate_part("app_instance_id", self.app_instance_id)
+        )
+
+    @property
+    def key(self) -> str:
+        return (
+            f"client:{self.client_id}|app:{self.application_id}|"
+            f"instance:{self.app_instance_id}"
+        )
+
+
+def optional_attribution(
+    client_id: str | None,
+    application_id: str | None,
+    app_instance_id: str | None,
+) -> ClientAttribution | None:
+    """Return an attribution or reject ambiguous partially attributed input."""
+
+    values = (client_id, application_id, app_instance_id)
+    if all(value is None or not value.strip() for value in values):
+        return None
+    if any(value is None or not value.strip() for value in values):
+        raise ValueError(
+            "client_id, application_id, and app_instance_id must be supplied together"
+        )
+    return ClientAttribution(client_id or "", application_id or "", app_instance_id or "")

src/fin_hub/cli.py

@@ -87,6 +87,10 @@ def _cmd_ops_costs(args: argparse.Namespace) -> int:
             amount=row.amount,
             currency=row.currency,
             source=row.source,
+            client_id=row.client_id,
+            application_id=row.application_id,
+            app_instance_id=row.app_instance_id,
+            cost_attribution_key=row.cost_attribution_key,
         )
         for row in parse_hosteurope_csv(Path(args.path))
     ]
@@ -256,4 +260,4 @@ def main(argv: list[str] | None = None) -> int:
 
 
 if __name__ == "__main__":
-    sys.exit(main())
+    sys.exit(main())

src/fin_hub/coupling/ops_hub.py

@@ -6,6 +6,8 @@ from collections import defaultdict
 from dataclasses import dataclass
 from typing import Iterable
 
+from fin_hub.attribution import optional_attribution
+
 
 @dataclass(frozen=True)
 class ServiceCostLine:
@@ -15,6 +17,19 @@ class ServiceCostLine:
     amount: float
     currency: str
     source: str
+    client_id: str | None = None
+    application_id: str | None = None
+    app_instance_id: str | None = None
+    cost_attribution_key: str | None = None
+
+    def __post_init__(self) -> None:
+        attribution = optional_attribution(
+            self.client_id, self.application_id, self.app_instance_id
+        )
+        expected_key = attribution.key if attribution else None
+        if self.cost_attribution_key not in (None, expected_key):
+            raise ValueError("cost_attribution_key does not match its attribution dimensions")
+        object.__setattr__(self, "cost_attribution_key", expected_key)
 
 
 def build_service_cost_report(
@@ -22,6 +37,7 @@ def build_service_cost_report(
 ) -> dict:
     by_service: dict[str, dict] = {}
     totals_by_month: dict[str, float] = defaultdict(float)
+    by_attribution: dict[tuple[str, str], dict] = {}
     for line in lines:
         bucket = by_service.setdefault(
             line.service_id,
@@ -37,11 +53,31 @@ def build_service_cost_report(
         bucket["months"][line.period_month] = month_total
         bucket["total"] += line.amount
         totals_by_month[line.period_month] += line.amount
+        key = (line.cost_attribution_key or "unattributed", line.currency)
+        attribution = by_attribution.setdefault(
+            key,
+            {
+                "cost_attribution_key": line.cost_attribution_key,
+                "client_id": line.client_id,
+                "application_id": line.application_id,
+                "app_instance_id": line.app_instance_id,
+                "currency": line.currency,
+                "months": {},
+                "total": 0.0,
+            },
+        )
+        attribution["months"][line.period_month] = (
+            attribution["months"].get(line.period_month, 0.0) + line.amount
+        )
+        attribution["total"] += line.amount
     services = sorted(by_service.values(), key=lambda item: item["total"], reverse=True)
     return {
         "source_hub": "fin-hub",
         "target_hub": "ops-hub",
         "signal": "service_cost_attribution",
         "services": services,
+        "attributions": sorted(
+            by_attribution.values(), key=lambda item: item["total"], reverse=True
+        ),
         "totals_by_month": dict(sorted(totals_by_month.items())),
-    }
+    }

src/fin_hub/ingest/hosteurope.py

@@ -6,6 +6,7 @@ from dataclasses import dataclass
 from datetime import date
 from pathlib import Path
 
+from fin_hub.attribution import optional_attribution
 from fin_hub.ingest._csv import parse_amount, pick, read_csv_rows
 
 
@@ -19,6 +20,10 @@ class HostEuropeCostRow:
     incurred_on: date | None
     environment: str = "production"
     source: str = "hosteurope"
+    client_id: str | None = None
+    application_id: str | None = None
+    app_instance_id: str | None = None
+    cost_attribution_key: str | None = None
 
 
 def parse_hosteurope_csv(path: Path, *, default_currency: str = "EUR") -> list[HostEuropeCostRow]:
@@ -38,6 +43,11 @@ def parse_hosteurope_csv(path: Path, *, default_currency: str = "EUR") -> list[H
             continue
         currency = pick(row, "currency") or default_currency
         environment = pick(row, "environment", "env") or "production"
+        attribution = optional_attribution(
+            pick(row, "client_id", "client") or None,
+            pick(row, "application_id", "app_id", "application") or None,
+            pick(row, "app_instance_id", "instance_id", "instance") or None,
+        )
         rows.append(
             HostEuropeCostRow(
                 service_id=service_id,
@@ -47,6 +57,10 @@ def parse_hosteurope_csv(path: Path, *, default_currency: str = "EUR") -> list[H
                 period_month=period[:7],
                 incurred_on=incurred_on,
                 environment=environment,
+                client_id=attribution.client_id if attribution else None,
+                application_id=attribution.application_id if attribution else None,
+                app_instance_id=attribution.app_instance_id if attribution else None,
+                cost_attribution_key=attribution.key if attribution else None,
             )
         )
-    return rows
+    return rows

src/fin_hub/models/service_cost.py

@@ -5,15 +5,25 @@ from __future__ import annotations
 import uuid
 from datetime import date
 
-from sqlalchemy import Date, Float, String
+from sqlalchemy import CheckConstraint, Date, Float, String, event
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import Mapped, mapped_column
 
 from hub_core.models.base import Base, TimestampMixin
+from fin_hub.attribution import optional_attribution
 
 
 class ServiceCost(Base, TimestampMixin):
     __tablename__ = "fin_service_costs"
+    __table_args__ = (
+        CheckConstraint(
+            "(client_id IS NULL AND application_id IS NULL AND app_instance_id IS NULL "
+            "AND cost_attribution_key IS NULL) OR "
+            "(client_id IS NOT NULL AND application_id IS NOT NULL "
+            "AND app_instance_id IS NOT NULL AND cost_attribution_key IS NOT NULL)",
+            name="ck_fin_service_costs_complete_attribution",
+        ),
+    )
 
     id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     service_id: Mapped[str] = mapped_column(String(128), nullable=False, index=True)
@@ -23,4 +33,20 @@ class ServiceCost(Base, TimestampMixin):
     currency: Mapped[str] = mapped_column(String(3), nullable=False, default="EUR")
     source: Mapped[str] = mapped_column(String(32), nullable=False)
     incurred_on: Mapped[date | None] = mapped_column(Date, nullable=True)
-    notes: Mapped[str | None] = mapped_column(String(512), nullable=True)
+    notes: Mapped[str | None] = mapped_column(String(512), nullable=True)
+    client_id: Mapped[str | None] = mapped_column(String(128), nullable=True, index=True)
+    application_id: Mapped[str | None] = mapped_column(String(128), nullable=True, index=True)
+    app_instance_id: Mapped[str | None] = mapped_column(String(128), nullable=True, index=True)
+    cost_attribution_key: Mapped[str | None] = mapped_column(String(423), nullable=True, index=True)
+
+
+@event.listens_for(ServiceCost, "before_insert")
+@event.listens_for(ServiceCost, "before_update")
+def _normalize_service_cost_attribution(_mapper, _connection, target: ServiceCost) -> None:
+    attribution = optional_attribution(
+        target.client_id, target.application_id, target.app_instance_id
+    )
+    expected_key = attribution.key if attribution else None
+    if target.cost_attribution_key not in (None, expected_key):
+        raise ValueError("cost_attribution_key does not match its attribution dimensions")
+    target.cost_attribution_key = expected_key

src/fin_hub/services/ledger.py

@@ -25,6 +25,10 @@ class LedgerEntry:
     period_month: str
     incurred_on: date | None
     source_path: str
+    client_id: str | None = None
+    application_id: str | None = None
+    app_instance_id: str | None = None
+    cost_attribution_key: str | None = None
 
 
 @dataclass(frozen=True)
@@ -92,6 +96,15 @@ def _ensure_schema(conn: sqlite3.Connection) -> None:
         );
         """
     )
+    columns = {row["name"] for row in conn.execute("PRAGMA table_info(ledger_entries)")}
+    for name in (
+        "client_id",
+        "application_id",
+        "app_instance_id",
+        "cost_attribution_key",
+    ):
+        if name not in columns:
+            conn.execute(f"ALTER TABLE ledger_entries ADD COLUMN {name} TEXT")
 
 
 def _utc_now() -> str:
@@ -171,6 +184,10 @@ def _entries_from_hosteurope(path: Path) -> list[LedgerEntry]:
             period_month=row.period_month,
             incurred_on=row.incurred_on,
             source_path=resolved,
+            client_id=row.client_id,
+            application_id=row.application_id,
+            app_instance_id=row.app_instance_id,
+            cost_attribution_key=row.cost_attribution_key,
         )
         for row in parse_hosteurope_csv(path)
     ]
@@ -217,8 +234,9 @@ def import_csv(
                 """
                 INSERT INTO ledger_entries (
                     source_type, category, label, amount, currency,
-                    period_month, incurred_on, source_path, imported_at
-                ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+                    period_month, incurred_on, source_path, imported_at,
+                    client_id, application_id, app_instance_id, cost_attribution_key
+                ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
                 """,
                 (
                     entry.source_type,
@@ -230,6 +248,10 @@ def import_csv(
                     entry.incurred_on.isoformat() if entry.incurred_on else None,
                     entry.source_path,
                     imported_at,
+                    entry.client_id,
+                    entry.application_id,
+                    entry.app_instance_id,
+                    entry.cost_attribution_key,
                 ),
             )
         conn.execute(
@@ -300,4 +322,4 @@ def ledger_stats(*, ledger_path: Path | None = None) -> dict:
 
 
 def ledger_stats_json(*, ledger_path: Path | None = None) -> str:
-    return json.dumps(ledger_stats(ledger_path=ledger_path), indent=2)
+    return json.dumps(ledger_stats(ledger_path=ledger_path), indent=2)

tests/test_attribution.py

@@ -0,0 +1,19 @@
+import pytest
+
+from fin_hub.attribution import ClientAttribution, optional_attribution
+
+
+def test_client_attribution_key_is_stable():
+    attribution = ClientAttribution(" acme ", "portal", "prod-01")
+    assert attribution.key == "client:acme|app:portal|instance:prod-01"
+
+
+def test_empty_attribution_is_explicitly_unattributed():
+    assert optional_attribution(None, None, None) is None
+    assert optional_attribution("", "", "") is None
+
+
+@pytest.mark.parametrize("invalid", ["has space", "has/slash", "", "x" * 129])
+def test_client_attribution_rejects_unsafe_parts(invalid: str):
+    with pytest.raises(ValueError):
+        ClientAttribution(invalid, "portal", "prod-01")

tests/test_coupling.py

@@ -21,4 +21,59 @@ def test_build_service_cost_report_groups_by_service():
     report = build_service_cost_report(lines)
     assert report["signal"] == "service_cost_attribution"
     assert len(report["services"]) == 2
-    assert report["totals_by_month"]["2026-06"] == pytest.approx(99.8)
+    assert report["totals_by_month"]["2026-06"] == pytest.approx(99.8)
+    assert report["attributions"][0]["cost_attribution_key"] is None
+
+
+def test_build_service_cost_report_groups_by_client_attribution():
+    lines = [
+        ServiceCostLine(
+            service_id="cluster",
+            environment="production",
+            period_month="2026-07",
+            amount=42.0,
+            currency="EUR",
+            source="fixture",
+            client_id="acme",
+            application_id="portal",
+            app_instance_id="prod-01",
+            cost_attribution_key="client:acme|app:portal|instance:prod-01",
+        )
+    ]
+
+    report = build_service_cost_report(lines)
+
+    assert report["attributions"] == [
+        {
+            "cost_attribution_key": "client:acme|app:portal|instance:prod-01",
+            "client_id": "acme",
+            "application_id": "portal",
+            "app_instance_id": "prod-01",
+            "currency": "EUR",
+            "months": {"2026-07": 42.0},
+            "total": 42.0,
+        }
+    ]
+
+
+def test_client_attribution_totals_do_not_mix_currencies():
+    common = {
+        "service_id": "cluster",
+        "environment": "production",
+        "period_month": "2026-07",
+        "source": "fixture",
+        "client_id": "acme",
+        "application_id": "portal",
+        "app_instance_id": "prod-01",
+    }
+    report = build_service_cost_report(
+        [
+            ServiceCostLine(amount=42.0, currency="EUR", **common),
+            ServiceCostLine(amount=50.0, currency="USD", **common),
+        ]
+    )
+
+    assert {(row["currency"], row["total"]) for row in report["attributions"]} == {
+        ("EUR", 42.0),
+        ("USD", 50.0),
+    }

tests/test_ingest.py

@@ -1,5 +1,7 @@
 from pathlib import Path
 
+import pytest
+
 from fin_hub.ingest.anthropic import parse_anthropic_billing_csv
 from fin_hub.ingest.cloud import parse_cloud_cost_csv
 from fin_hub.ingest.hosteurope import parse_hosteurope_csv
@@ -25,4 +27,31 @@ def test_parse_hosteurope_csv():
     rows = parse_hosteurope_csv(FIXTURES / "hosteurope.csv")
     assert len(rows) == 2
     assert rows[0].service_id == "dedicated-server-m"
-    assert rows[0].period_month == "2026-06"
+    assert rows[0].period_month == "2026-06"
+
+
+def test_parse_hosteurope_client_attribution(tmp_path: Path):
+    source = tmp_path / "attributed.csv"
+    source.write_text(
+        "product,amount,currency,invoice_date,client_id,application_id,app_instance_id\n"
+        "Managed cluster,42.00,EUR,2026-07-01,acme,portal,prod-01\n",
+        encoding="utf-8",
+    )
+
+    row = parse_hosteurope_csv(source)[0]
+    assert row.client_id == "acme"
+    assert row.application_id == "portal"
+    assert row.app_instance_id == "prod-01"
+    assert row.cost_attribution_key == "client:acme|app:portal|instance:prod-01"
+
+
+def test_parse_hosteurope_rejects_partial_attribution(tmp_path: Path):
+    source = tmp_path / "partial.csv"
+    source.write_text(
+        "product,amount,currency,invoice_date,client_id\n"
+        "Managed cluster,42.00,EUR,2026-07-01,acme\n",
+        encoding="utf-8",
+    )
+
+    with pytest.raises(ValueError, match="must be supplied together"):
+        parse_hosteurope_csv(source)

tests/test_ledger.py

@@ -1,3 +1,4 @@
+import sqlite3
 from pathlib import Path
 
 import pytest
@@ -36,6 +37,53 @@ def test_ledger_import_skips_unchanged_file(tmp_path: Path):
     assert second.rows_imported == 0
 
 
+def test_ledger_import_preserves_client_attribution(tmp_path: Path):
+    source = tmp_path / "attributed.csv"
+    source.write_text(
+        "product,amount,currency,invoice_date,client_id,application_id,app_instance_id\n"
+        "Managed cluster,42.00,EUR,2026-07-01,acme,portal,prod-01\n",
+        encoding="utf-8",
+    )
+    ledger = tmp_path / "ledger.db"
+
+    import_csv(source, "hosteurope", ledger_path=ledger)
+
+    with sqlite3.connect(ledger) as conn:
+        row = conn.execute(
+            "SELECT client_id, application_id, app_instance_id, cost_attribution_key "
+            "FROM ledger_entries"
+        ).fetchone()
+    assert row == (
+        "acme",
+        "portal",
+        "prod-01",
+        "client:acme|app:portal|instance:prod-01",
+    )
+
+
+def test_existing_ledger_schema_is_migrated_additively(tmp_path: Path):
+    ledger = tmp_path / "legacy.db"
+    with sqlite3.connect(ledger) as conn:
+        conn.execute(
+            "CREATE TABLE ledger_entries ("
+            "id INTEGER PRIMARY KEY, source_type TEXT NOT NULL, category TEXT NOT NULL, "
+            "label TEXT NOT NULL, amount REAL NOT NULL, currency TEXT NOT NULL, "
+            "period_month TEXT NOT NULL, incurred_on TEXT, source_path TEXT NOT NULL, "
+            "imported_at TEXT NOT NULL)"
+        )
+
+    monthly_summary(ledger_path=ledger)
+
+    with sqlite3.connect(ledger) as conn:
+        columns = {row[1] for row in conn.execute("PRAGMA table_info(ledger_entries)")}
+    assert {
+        "client_id",
+        "application_id",
+        "app_instance_id",
+        "cost_attribution_key",
+    }.issubset(columns)
+
+
 def test_evaluate_runway_from_ledger(tmp_path: Path):
     ledger = tmp_path / "ledger.db"
     seed_fixture_ledger(ledger_path=ledger, opening_balance=12000.0)
@@ -57,4 +105,4 @@ def test_build_runway_report_and_write_evidence(tmp_path: Path):
         opening_balance=12000.0,
     )
     assert output.exists()
-    assert "runway-dogfood-" in output.name
+    assert "runway-dogfood-" in output.name

tests/test_models.py

@@ -20,4 +20,12 @@ def test_model_classes_importable():
     assert BurnRate.__tablename__ == "fin_burn_rates"
     assert RunwayProjection.__tablename__ == "fin_runway_projections"
     assert TokenSpend.__tablename__ == "fin_token_spends"
-    assert ServiceCost.__tablename__ == "fin_service_costs"
+    assert ServiceCost.__tablename__ == "fin_service_costs"
+
+
+def test_service_cost_has_external_attribution_seam():
+    columns = ServiceCost.__table__.columns
+    assert columns["client_id"].nullable is True
+    assert columns["application_id"].nullable is True
+    assert columns["app_instance_id"].nullable is True
+    assert columns["cost_attribution_key"].nullable is True

workplans/FIN-WP-0002-client-attribution-and-billing-basis.md

@@ -68,7 +68,7 @@ authority.
 
 ```task
 id: FIN-WP-0002-T01
-status: todo
+status: done
 priority: high
 state_hub_task_id: "904e9edc-a434-41e6-a4c7-ebb407469514"
 ```
@@ -82,11 +82,19 @@ Cover unknown/unattributed values, uniqueness and period semantics,
 corrections, migrations, validation, and backward compatibility for existing
 service-level records.
 
+Completed 2026-08-10: added a canonical validated external attribution key,
+optional client/application/instance columns to `ServiceCost`, HostEurope CSV
+ingestion and the SQLite ledger, additive migration for existing ledgers, and
+currency-safe attributed reporting alongside the backward-compatible service
+view. Partial or mismatched attribution is rejected; legacy rows remain
+explicitly unattributed. Covered by the full test suite and documented in
+`README.md`.
+
 ## Add engagement revenue and margin reporting
 
 ```task
 id: FIN-WP-0002-T02
-status: wait
+status: todo
 priority: high
 state_hub_task_id: "f917bb0b-f44e-4642-9130-c1a004185180"
 ```