HKUDS/Vibe-Trading · error · ValueError

WACCResult.wacc= does not match the weighted blend of…

Error message

WACCResult.wacc={self.wacc!r} does not match the weighted blend {expected!r} of cost_of_equity and cost_of_debt_after_tax

What it means

WACCResult.__post_init__ recomputes equity_weight*cost_of_equity + debt_weight*cost_of_debt_after_tax and raises ValueError if the stored wacc field does not match within tolerance. It enforces internal consistency of the result object (no silently inconsistent dataclass).

Solutions

Construct WACCResult via the public wacc() function rather than manually
If constructing manually, compute wacc = e_w*Ke + d_w*Kd_at and pass that exact value
Recompute the blend after any field change instead of editing wacc in isolation

Example fix

# before
WACCResult(wacc=0.10, equity_weight=.5, cost_of_equity=.12, debt_weight=.5, cost_of_debt_after_tax=.04)

# after
WACCResult(wacc=.5*.12 + .5*.04, equity_weight=.5, cost_of_equity=.12, debt_weight=.5, cost_of_debt_after_tax=.04)

Defensive patterns

Strategy: validation

Validate before calling

w = equity_weight * cost_of_equity + debt_weight * cost_of_debt_after_tax
result = WACCResult(wacc=w, equity_weight=equity_weight, ...)

Try / catch

try:
    WACCResult(...)
except ValueError as e:
    raise AssertionError(f'inconsistent WACC inputs: {e}') from e

Prevention

Always build WACCResult via wacc()
Compute wacc from the same numbers stored in the object
Don't mutate result fields independently

When it happens

Trigger: Manually constructing WACCResult(wacc=0.10, equity_weight=0.5, cost_of_equity=0.12, debt_weight=0.5, cost_of_debt_after_tax=0.04) where the blend is 0.08, not 0.10; mutating fields after construction is similarly caught on revalidation.

Common situations: Building the result object by hand in tests or adapters instead of calling wacc(); copy-paste of numbers from a stale model run.

Related errors

AI-assisted analysis of HKUDS/Vibe-Trading@80ffdda44c (2026-08-28). Data as JSON: /api/errors/1a4b8ec569155fdb. Report an issue: GitHub.

Appendix: source

Thrown at agent/src/quantlib/valuation/dcf.py:366

    debt_weight: float
    wacc: float

    def __post_init__(self) -> None:
        """Re-check the blend arithmetic and the weight identity.

        Raises:
            ValueError: If the weights do not sum to 1, or ``wacc`` is not the
                stated weighted blend of the two costs of capital.
        """
        _validate_weights(self.equity_weight, self.debt_weight, model="WACCResult")
        expected = (
            self.equity_weight * self.cost_of_equity
            + self.debt_weight * self.cost_of_debt_after_tax
        )
        if not math.isclose(
            self.wacc, expected, rel_tol=_RECONCILIATION_TOLERANCE, abs_tol=1e-12
        ):
            raise ValueError(
                f"WACCResult.wacc={self.wacc!r} does not match the weighted "
                f"blend {expected!r} of cost_of_equity and cost_of_debt_after_tax"
            )


def wacc(
    *,
    risk_free_rate: float,
    beta: float,
    equity_risk_premium: float,
    pretax_cost_of_debt: float,
    tax_rate: float,
    capital_structure_basis: str,
    market_value_of_equity: float | None = None,
    market_value_of_debt: float | None = None,
    target_equity_weight: float | None = None,
    target_debt_weight: float | None = None,
    size_premium: float = 0.0,

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