fix(portfolio): tolerate consolidation WAC residue

app/core/config.py

@@ -18,7 +18,7 @@ if env_file.exists():
 
 class Settings(BaseSettings):
     app_name: str = "PortfolioHub"
-    app_version: str = "0.3.1"
+    app_version: str = "0.3.2"
     environment: str = "development"
     allowed_origins_raw: str = Field(default="http://localhost:3000", validation_alias="PORTFOLIOHUB_ALLOWED_ORIGINS")
     bootstrap_username: str = Field(default="", validation_alias="PORTFOLIOHUB_BOOTSTRAP_USERNAME")

app/domain/corporate_actions.py

@@ -6,6 +6,13 @@ import json
 from dataclasses import dataclass
 from decimal import ROUND_HALF_UP, Decimal
 
+STORAGE_QUANTUM = Decimal("0.00000001")
+
+
+def quantize_stored_decimal(value: Decimal) -> Decimal:
+    """Round a monetary value to the NUMERIC(*, 8) persistence contract."""
+    return value.quantize(STORAGE_QUANTUM, rounding=ROUND_HALF_UP)
+
 
 def canonical_payload_hash(payload: object) -> str:
     if hasattr(payload, "model_dump"):
@@ -36,11 +43,13 @@ def calculate_stock_consolidation(quantity_before: Decimal, quantity_after: Deci
         raise CorporateActionError("stock consolidation must reduce quantity")
     if q1 != q1.to_integral_value() or q0 != q0.to_integral_value():
         raise CorporateActionError("fractional result unsupported", "FRACTIONAL_RESULT_UNSUPPORTED")
-    total = (q0 * wac).quantize(Decimal("0.00000001"), rounding=ROUND_HALF_UP)
-    after = (total / q1).quantize(Decimal("0.00000001"), rounding=ROUND_HALF_UP)
-    if after * q1 != total:
-        raise CorporateActionError("fractional result unsupported", "FRACTIONAL_RESULT_UNSUPPORTED")
-    return StockConsolidation(q0, q1, wac, after, total, ratio)
+    # Preserve the authoritative pre-action total independently. A per-unit WAC
+    # rounded to the storage scale cannot always multiply back to that total
+    # exactly, and that harmless decimal residue is not a fractional share.
+    total = quantize_stored_decimal(q0 * wac)
+    before = quantize_stored_decimal(wac)
+    after = quantize_stored_decimal(total / q1)
+    return StockConsolidation(q0, q1, before, after, total, ratio)
 
 def apply_corporate_action_to_wac(quantity: Decimal, wac: Decimal, quantity_after: Decimal) -> tuple[Decimal, Decimal]:
     result = calculate_stock_consolidation(quantity, quantity_after, wac)

app/domain/pnl.py

@@ -179,7 +179,11 @@ def calculate_realized_pnl(
             if abs(running_qty - before) > 1e-9:
                 warning_triggered = True
             running_qty = after
-            running_wac = float(row.get("average_price_after", running_wac * before / after))
+            total_cost_basis = row.get("total_cost_basis")
+            if total_cost_basis is not None:
+                running_wac = float(total_cost_basis) / after
+            else:
+                running_wac = float(row.get("average_price_after", running_wac * before / after))
 
     warning: str | None = None
     if warning_triggered:
@@ -272,7 +276,11 @@ def calculate_current_wac(rows: list[dict[str, Any]]) -> CurrentWacResult:
             if abs(running_qty - before) > 1e-9:
                 warning_triggered = True
             running_qty = after
-            running_wac = float(row.get("average_price_after", running_wac * before / after))
+            total_cost_basis = row.get("total_cost_basis")
+            if total_cost_basis is not None:
+                running_wac = float(total_cost_basis) / after
+            else:
+                running_wac = float(row.get("average_price_after", running_wac * before / after))
 
     warning: str | None = None
     if warning_triggered:

app/repositories/postgres.py

@@ -14,6 +14,7 @@ from typing import Any
 import psycopg
 from psycopg import sql
 
+from app.domain.corporate_actions import calculate_stock_consolidation
 from app.domain.errors import (
     DaemonInactiveError,
     DaemonInUseError,
@@ -1668,11 +1669,14 @@ class PostgresPortfolioRepository:
                 wac = calculate_current_wac(history)
                 if Decimal(str(row[0])) != action.quantity_before or Decimal(str(wac.current_quantity)) != action.quantity_before:
                     raise ValueError("CORPORATE_ACTION_STALE_QUANTITY")
-                action.average_price_before = Decimal(str(wac.current_wac or 0))
-                action.total_cost_basis = (action.average_price_before * action.quantity_before).quantize(Decimal("0.00000001"))
-                action.average_price_after = (action.total_cost_basis / action.quantity_after).quantize(Decimal("0.00000001"))
-                if action.average_price_after * action.quantity_after != action.total_cost_basis:
-                    raise ValueError("FRACTIONAL_RESULT_UNSUPPORTED")
+                consolidation = calculate_stock_consolidation(
+                    action.quantity_before,
+                    action.quantity_after,
+                    Decimal(str(wac.current_wac or 0)),
+                )
+                action.average_price_before = consolidation.average_price_before
+                action.average_price_after = consolidation.average_price_after
+                action.total_cost_basis = consolidation.total_cost_basis
                 cur.execute("SELECT corporate_action_id, portfolio_id, asset_id, action_type, effective_date, actor_user_id, evidence_ref, idempotency_key, payload_hash, quantity_before, quantity_after, average_price_before, average_price_after, total_cost_basis, cash_balance, profit_buffer, ledger_entry_id, recorded_at FROM portfolio_corporate_actions WHERE portfolio_id=%s AND idempotency_key=%s", (portfolio_id, idempotency_key))
                 prior = cur.fetchone()
                 if prior: