fix: restore manual confirm_duplicate compatibility and precision safeguards

Co-authored-by: genichin <4282227+genichin@users.noreply.github.com>

tests/test_bat025_portfolio_ledger_manual_metadata_migration.py

@@ -312,3 +312,47 @@ def test_dividend_precision_and_reversal_round_trip_on_real_postgres(
         assert cur.fetchone()[0] == "0"
 
     repo.close()
+
+
+def test_existing_high_precision_snapshot_still_allows_legacy_manual_actions(
+    isolated_settings: Settings,
+) -> None:
+    """Existing DOUBLE snapshot precision should not block unrelated manual actions."""
+    upgrade_to_head(isolated_settings)
+    repo = _repo(isolated_settings)
+    portfolio_id = _seed_portfolio(repo, "legacy-snapshot-precision")
+    with repo._connect().cursor() as cur:
+        cur.execute(
+            "UPDATE portfolios SET cash_balance = %s WHERE portfolio_id = %s",
+            (0.123456789, portfolio_id),
+        )
+
+    entry = repo.record_manual_ledger(
+        portfolio_id,
+        action="INVEST",
+        amount=Decimal("1.00000000"),
+        note="compat",
+    )
+    assert entry.action == "INVEST"
+    assert entry.price == 1.0
+    repo.close()
+
+
+def test_dividend_large_integer_with_8dp_is_rejected_to_protect_double_snapshot(
+    isolated_settings: Settings,
+) -> None:
+    """Inputs valid for NUMERIC(20,8) but unsafe for DOUBLE snapshot are rejected."""
+    upgrade_to_head(isolated_settings)
+    repo = _repo(isolated_settings)
+    portfolio_id = _seed_portfolio(repo, "double-snapshot-guard")
+
+    with pytest.raises(ValueError, match="double snapshot precision"):
+        repo.record_manual_ledger(
+            portfolio_id,
+            action="DIVIDEND",
+            amount=Decimal("1000000000.00000001"),
+            tax=Decimal("0.00000001"),
+            executed_at=datetime(2026, 9, 1, 0, 0, 0, tzinfo=timezone.utc),
+            note="too-large-for-double",
+        )
+    repo.close()

tests/test_v1_portfolios_manual_ledger.py

@@ -558,6 +558,37 @@ def test_dividend_duplicate_requires_confirmation() -> None:
     assert confirmed.status_code == 201
 
 
+def test_confirm_duplicate_false_is_accepted_for_non_dividend_actions() -> None:
+    repo = _FakeRepo(_portfolio())
+    client = _make_client(repo)
+
+    invest = client.post(
+        f"/v1/portfolios/{_PORTFOLIO_ID}/ledger/manual",
+        json={"action": "INVEST", "amount": 100, "confirm_duplicate": False},
+        headers=_auth(),
+    )
+    assert invest.status_code == 201
+
+    buy = client.post(
+        f"/v1/portfolios/{_PORTFOLIO_ID}/ledger/manual",
+        json={"action": "BUY", "quantity": 1, "price": 10, "confirm_duplicate": False},
+        headers=_auth(),
+    )
+    assert buy.status_code == 201
+
+
+def test_confirm_duplicate_true_is_rejected_for_non_dividend_actions() -> None:
+    repo = _FakeRepo(_portfolio())
+    client = _make_client(repo)
+
+    invest = client.post(
+        f"/v1/portfolios/{_PORTFOLIO_ID}/ledger/manual",
+        json={"action": "INVEST", "amount": 100, "confirm_duplicate": True},
+        headers=_auth(),
+    )
+    assert invest.status_code == 422
+
+
 def test_dividend_reversal_decreases_profit_buffer() -> None:
     repo = _FakeRepo(_portfolio(buffer=200))
     client = _make_client(repo)