Address PR #367 R1 review (1 P3)

R1 P3 — forward-looking docs were internally inconsistent about
Phase 4.5 C survey support for yatchew_hr_test. TODO.md correctly
distinguishes Rao-Wu (Stute family) from weighted-OLS+weighted-variance
(Yatchew); the new C0 docs in had_pretests.py, REGISTRY.md, and
CHANGELOG.md described the whole linearity family as Rao-Wu-based,
which would mislead the next implementer (Yatchew 1997 is a closed-form
variance-ratio test, not bootstrap-based).

Updated all three new docs to spell out the per-test mechanism
explicitly: Rao-Wu rescaled bootstrap for stute_test +
stute_joint_pretest + joint_pretrends_test + joint_homogeneity_test;
weighted OLS residuals + weighted variance estimator for
yatchew_hr_test. Now consistent with TODO.md.

Test message-text assertions still pass (assert "Rao-Wu" in msg holds
because Stute family still uses Rao-Wu).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: igerber

CHANGELOG.md

@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
-- **`qug_test` and `did_had_pretest_workflow` survey-aware NotImplementedError gates (Phase 4.5 C0 decision gate).** `qug_test(d, *, survey=None, weights=None)` and `did_had_pretest_workflow(..., *, survey=None, weights=None)` now accept the two kwargs as keyword-only with default `None`. Passing either non-`None` raises `NotImplementedError` with an educational message naming the methodology rationale and pointing users to joint Stute (Phase 4.5 C, planned) as the survey-compatible alternative. Mutex guard on `survey=` + `weights=` mirrors `HeterogeneousAdoptionDiD.fit()` at `had.py:2890`. **QUG-under-survey is permanently deferred** — the test statistic uses extreme order statistics `D_{(1)}, D_{(2)}` which are NOT smooth functionals of the empirical CDF, so standard survey machinery (Binder-TSL linearization, Rao-Wu rescaled bootstrap, Krieger-Pfeffermann (1997) EDF tests) does not yield a calibrated test; under cluster sampling the `Exp(1)/Exp(1)` limit law's independence assumption breaks; and the EVT-under-unequal-probability-sampling literature (Quintos et al. 2001, Beirlant et al.) addresses tail-index estimation, not boundary tests. The workflow's gate is **temporary** — Phase 4.5 C will close it for the linearity-family pretests (`stute_test`, `yatchew_hr_test`, joint variants) via Rao-Wu rescaled bootstrap. Sister pretests (`stute_test`, `yatchew_hr_test`, `stute_joint_pretest`, `joint_pretrends_test`, `joint_homogeneity_test`) keep their closed signatures in this release — Phase 4.5 C will add kwargs and implementation together to avoid API churn. Unweighted `qug_test(d)` and `did_had_pretest_workflow(...)` calls are bit-exact pre-PR (kwargs are keyword-only after `*`; positional path unchanged). New tests at `tests/test_had_pretests.py::TestQUGTest` (5 rejection / mutex / message / regression tests) and the new `TestHADPretestWorkflowSurveyGuards` class (6 tests covering both kwarg paths, mutex, methodology pointer, both aggregate paths, and unweighted regression). See `docs/methodology/REGISTRY.md` § "QUG Null Test" — Note (Phase 4.5 C0) for the full methodology rationale plus a sketch of the (out-of-scope) theoretical bridge that combines endpoint-estimation EVT (Hall 1982, Aarssen-de Haan 1994, Hall-Wang 1999, Beirlant-de Wet-Goegebeur 2006), survey-aware functional CLTs (Boistard-Lopuhaä-Ruiz-Gazen 2017, Bertail-Chautru-Clémençon 2017), and tail-empirical-process theory (Drees 2003) — publishable methodology research, not engineering work.
+- **`qug_test` and `did_had_pretest_workflow` survey-aware NotImplementedError gates (Phase 4.5 C0 decision gate).** `qug_test(d, *, survey=None, weights=None)` and `did_had_pretest_workflow(..., *, survey=None, weights=None)` now accept the two kwargs as keyword-only with default `None`. Passing either non-`None` raises `NotImplementedError` with an educational message naming the methodology rationale and pointing users to joint Stute (Phase 4.5 C, planned) as the survey-compatible alternative. Mutex guard on `survey=` + `weights=` mirrors `HeterogeneousAdoptionDiD.fit()` at `had.py:2890`. **QUG-under-survey is permanently deferred** — the test statistic uses extreme order statistics `D_{(1)}, D_{(2)}` which are NOT smooth functionals of the empirical CDF, so standard survey machinery (Binder-TSL linearization, Rao-Wu rescaled bootstrap, Krieger-Pfeffermann (1997) EDF tests) does not yield a calibrated test; under cluster sampling the `Exp(1)/Exp(1)` limit law's independence assumption breaks; and the EVT-under-unequal-probability-sampling literature (Quintos et al. 2001, Beirlant et al.) addresses tail-index estimation, not boundary tests. The workflow's gate is **temporary** — Phase 4.5 C will close it for the linearity-family pretests with mechanism varying by test: Rao-Wu rescaled bootstrap for `stute_test` and the joint variants (`stute_joint_pretest`, `joint_pretrends_test`, `joint_homogeneity_test`); weighted OLS residuals + weighted variance estimator for `yatchew_hr_test` (Yatchew 1997 is a closed-form variance-ratio test, not bootstrap-based). Sister pretests (`stute_test`, `yatchew_hr_test`, `stute_joint_pretest`, `joint_pretrends_test`, `joint_homogeneity_test`) keep their closed signatures in this release — Phase 4.5 C will add kwargs and implementation together to avoid API churn. Unweighted `qug_test(d)` and `did_had_pretest_workflow(...)` calls are bit-exact pre-PR (kwargs are keyword-only after `*`; positional path unchanged). New tests at `tests/test_had_pretests.py::TestQUGTest` (5 rejection / mutex / message / regression tests) and the new `TestHADPretestWorkflowSurveyGuards` class (6 tests covering both kwarg paths, mutex, methodology pointer, both aggregate paths, and unweighted regression). See `docs/methodology/REGISTRY.md` § "QUG Null Test" — Note (Phase 4.5 C0) for the full methodology rationale plus a sketch of the (out-of-scope) theoretical bridge that combines endpoint-estimation EVT (Hall 1982, Aarssen-de Haan 1994, Hall-Wang 1999, Beirlant-de Wet-Goegebeur 2006), survey-aware functional CLTs (Boistard-Lopuhaä-Ruiz-Gazen 2017, Bertail-Chautru-Clémençon 2017), and tail-empirical-process theory (Drees 2003) — publishable methodology research, not engineering work.
 - **`HeterogeneousAdoptionDiD` mass-point `survey=` / `weights=` + event-study `aggregate="event_study"` survey composition + multiplier-bootstrap sup-t simultaneous confidence band (Phase 4.5 B).** Closes the two Phase 4.5 A `NotImplementedError` gates: `design="mass_point" + weights/survey` and `aggregate="event_study" + weights/survey`. Weighted 2SLS sandwich in `_fit_mass_point_2sls` follows the Wooldridge 2010 Ch. 12 pweight convention (`w²` in the HC1 meat, `w·u` in the CR1 cluster score, weighted bread `Z'WX`); HC1 and CR1 ("stata" `se_type`) bit-parity with `estimatr::iv_robust(..., weights=, clusters=)` at `atol=1e-10` (new cross-language golden at `benchmarks/data/estimatr_iv_robust_golden.json`, generated by `benchmarks/R/generate_estimatr_iv_robust_golden.R`; `estimatr` added to `benchmarks/R/requirements.R`). `_fit_mass_point_2sls` gains `weights=` + `return_influence=` kwargs and now always returns a 3-tuple `(beta, se, psi)` — `psi` is the per-unit IF on the β̂-scale scaled so `compute_survey_if_variance(psi, trivial_resolved) ≈ V_HC1[1,1]` at `atol=1e-10` (PR #359 IF scale convention applied uniformly; no `sum(psi²)` claims). Event-study per-horizon variance: `survey=` path composes Binder-TSL via `compute_survey_if_variance`; `weights=` shortcut uses the analytical weighted-robust SE (continuous: CCT-2014 `bc_fit.se_robust / |den|`; mass-point: weighted 2SLS pweight sandwich from `_fit_mass_point_2sls` — HC1 / classical / CR1). `survey_metadata` / `variance_formula` / `effective_dose_mean` populated in both regimes (previously hardcoded `None` at `had.py:3366`). New multiplier-bootstrap sup-t: `_sup_t_multiplier_bootstrap` reuses `diff_diff.bootstrap_utils.generate_survey_multiplier_weights_batch` for PSU-level draws with stratum centering + sqrt(n_h/(n_h-1)) small-sample correction + FPC scaling + lonely-PSU handling. On the `weights=` shortcut, sup-t calibration is routed through a synthetic trivial `ResolvedSurveyDesign` so the centered + small-sample-corrected branch fires uniformly — targets the analytical HC1 variance family (`compute_survey_if_variance(IF, trivial) ≈ V_HC1` per the PR #359 IF scale invariant) rather than the raw `sum(ψ²) = ((n-1)/n) · V_HC1` that unit-level Rademacher multipliers would produce on the HC1-scaled IF. Perturbations: `delta = weights @ IF` with NO `(1/n)` prefactor (matching `staggered_bootstrap.py:373` idiom), normalized by per-horizon analytical SE, `(1-alpha)`-quantile of the sup-t distribution. At H=1 the quantile reduces to `Φ⁻¹(1 − alpha/2) ≈ 1.96` up to MC noise (regression-locked by `TestSupTReducesToNormalAtH1`). `HeterogeneousAdoptionDiD.__init__` gains `n_bootstrap: int = 999` and `seed: Optional[int] = None` (CS-parity singular seed); `fit()` gains `cband: bool = True` (only consulted on weighted event-study). `HeterogeneousAdoptionDiDEventStudyResults` extended with `variance_formula`, `effective_dose_mean`, `cband_low`, `cband_high`, `cband_crit_value`, `cband_method`, `cband_n_bootstrap` (all `None` on unweighted fits); surfaced in `to_dict`, `to_dataframe`, `summary`, `__repr__`. Unweighted event-study with `cband=False` preserves pre-Phase 4.5 B numerical output bit-exactly (stability invariant, locked by regression tests). Zero-weight subpopulation convention carries over from PR #359 (filter for design decisions; preserve full ResolvedSurveyDesign for variance). Non-pweight SurveyDesigns (`aweight`, `fweight`, replicate designs) raise `NotImplementedError` on both new paths (reciprocal-guard discipline). Pretest surfaces (`qug_test`, `stute_test`, `yatchew_hr_test`, joint variants, `did_had_pretest_workflow`) remain unweighted in this release — Phase 4.5 C / C0. See `docs/methodology/REGISTRY.md` §HeterogeneousAdoptionDiD "Weighted 2SLS (Phase 4.5 B)", "Event-study survey composition", and "Sup-t multiplier bootstrap" for derivations and invariants.
 - **`HeterogeneousAdoptionDiD.fit(survey=..., weights=...)` on continuous-dose paths (Phase 4.5 survey support).** The `continuous_at_zero` (paper Design 1') and `continuous_near_d_lower` (Design 1 continuous-near-d̲) designs accept survey weights through two interchangeable kwargs: `weights=<array>` (pweight shortcut, weighted-robust SE from the CCT-2014 lprobust port) and `survey=SurveyDesign(weights, strata, psu, fpc)` (design-based inference via Binder-TSL variance using the existing `compute_survey_if_variance` helper at `diff_diff/survey.py:1802`). Point estimates match across both entry paths; SE diverges by design (pweight-only vs PSU-aggregated). `HeterogeneousAdoptionDiDResults.survey_metadata` is a repo-standard `SurveyMetadata` dataclass (weight_type / effective_n / design_effect / sum_weights / weight_range / n_strata / n_psu / df_survey); HAD-specific extras (`variance_formula` label, `effective_dose_mean`) are separate top-level result fields. `to_dict()` surfaces the full `SurveyMetadata` object plus `variance_formula` + `effective_dose_mean`; `summary()` renders `variance_formula`, `effective_n`, `effective_dose_mean`, and (when the survey= path is used) `df_survey`; `__repr__` surfaces `variance_formula` + `effective_dose_mean` when present. The HAD `mass_point` design and `aggregate="event_study"` path raise `NotImplementedError` under survey/weights (deferred to Phase 4.5 B: weighted 2SLS + event-study survey composition); the HAD pretests stay unweighted in this release (Phase 4.5 C). Parity ceiling acknowledged — no public weighted-CCF bias-corrected local-linear reference exists in any language; methodology confidence comes from (1) uniform-weights bit-parity at `atol=1e-14` on the full lprobust output struct, (2) cross-language weighted-OLS parity (manual R reference) at `atol=1e-12`, and (3) Monte Carlo oracle consistency on known-τ DGPs. `_nprobust_port.lprobust` gains `weights=` and `return_influence=` (used internally by the Binder-TSL path); `bias_corrected_local_linear` removes the Phase 1c `NotImplementedError` on `weights=` and forwards. Auto-bandwidth selection remains unweighted in this release — pass `h`/`b` explicitly for weight-aware bandwidths. See `docs/methodology/REGISTRY.md` §HeterogeneousAdoptionDiD "Weighted extension (Phase 4.5 survey support)".
 - **`stute_joint_pretest`, `joint_pretrends_test`, `joint_homogeneity_test` + `StuteJointResult`** (HeterogeneousAdoptionDiD Phase 3 follow-up). Joint Cramér-von Mises pretests across K horizons with shared-η Mammen wild bootstrap (preserves vector-valued empirical-process unit-level dependence per Delgado-Manteiga 2001 / Hlávka-Hušková 2020). The core `stute_joint_pretest` is residuals-in; two thin data-in wrappers construct per-horizon residuals for the two nulls the paper spells out: mean-independence (step 2 pre-trends, `OLS(Y_t − Y_base ~ 1)` per pre-period) and linearity (step 3 joint, `OLS(Y_t − Y_base ~ 1 + D)` per post-period). Sum-of-CvMs aggregation (`S_joint = Σ_k S_k`); per-horizon scale-invariant exact-linear short-circuit. Closes the paper Section 4.2 step-2 gap that Phase 3 `did_had_pretest_workflow` previously flagged with an "Assumption 7 pre-trends test NOT run" caveat. See `docs/methodology/REGISTRY.md` §HeterogeneousAdoptionDiD "Joint Stute tests" for algorithm, invariants, and scope exclusion of Eq 18 linear-trend detrending (deferred to Phase 4 Pierce-Schott replication).

diff_diff/had_pretests.py

@@ -2804,14 +2804,19 @@ def did_had_pretest_workflow(
        decision gate). Extreme-order-statistic tests are not smooth
        functionals of the empirical CDF and have no off-the-shelf
        survey-aware analog. See :func:`qug_test` Notes.
-    2. Survey support for the linearity-family pretests (:func:`stute_test`,
-       :func:`yatchew_hr_test`, :func:`stute_joint_pretest`,
-       :func:`joint_pretrends_test`, :func:`joint_homogeneity_test`) is
-       planned for Phase 4.5 C via Rao-Wu rescaled bootstrap. Until that
-       ships those sister pretests still raise bare ``TypeError`` on
-       ``survey=`` / ``weights=`` because their signatures are closed
-       (no kwargs added) -- adding rejection-only kwargs in C0 then
-       implementing in C is API churn for no user benefit.
+    2. Survey support for the linearity-family pretests is planned for
+       Phase 4.5 C, with mechanism varying by test: Rao-Wu rescaled
+       bootstrap for the Stute family (:func:`stute_test`,
+       :func:`stute_joint_pretest`, :func:`joint_pretrends_test`,
+       :func:`joint_homogeneity_test`) -- weighted multipliers + PSU
+       clustering in the bootstrap draw; weighted OLS residuals +
+       weighted variance estimator for :func:`yatchew_hr_test` (Yatchew
+       1997 is a closed-form variance-ratio test, not bootstrap-based).
+       Until C ships, those sister pretests still raise bare
+       ``TypeError`` on ``survey=`` / ``weights=`` because their
+       signatures are closed (no kwargs added) -- adding rejection-only
+       kwargs in C0 then implementing in C is API churn for no user
+       benefit.
 
     Until Phase 4.5 C ships, run the workflow without ``survey`` /
     ``weights`` kwargs and verify identification manually.
@@ -2848,8 +2853,13 @@ def did_had_pretest_workflow(
             "QUG-under-survey is permanently deferred (extreme-value "
             "theory under complex sampling is not a settled toolkit; see "
             "qug_test docstring for the methodology rationale). Survey "
-            "support for stute_test, yatchew_hr_test, and joint variants "
-            "is planned for Phase 4.5 C via Rao-Wu rescaled bootstrap. "
+            "support for the linearity-family pretests is planned for "
+            "Phase 4.5 C, with mechanism varying by test: Rao-Wu "
+            "rescaled bootstrap for the Stute family (stute_test, "
+            "stute_joint_pretest, joint_pretrends_test, "
+            "joint_homogeneity_test); weighted OLS residuals + weighted "
+            "variance estimator for yatchew_hr_test (Yatchew 1997 is a "
+            "closed-form variance-ratio test, not bootstrap-based). "
             "Until that ships, run the workflow without survey/weights "
             "kwargs and verify identification manually."
         )

docs/methodology/REGISTRY.md

@@ -2373,7 +2373,7 @@ Tuning-parameter-free test of `H_0: d̲ = 0` versus `H_1: d̲ > 0`. Shipped in `
   1. **Extreme order statistics are not smooth functionals of the empirical CDF.** Standard survey machinery (Binder-TSL linearization via `compute_survey_if_variance`, Rao-Wu rescaled bootstrap via `bootstrap_utils.generate_rao_wu_weights`, Krieger-Pfeffermann (1997) EDF tests for complex surveys) all rely on Hadamard differentiability of the test statistic in the empirical CDF. The first two order statistics are NOT differentiable functionals — small perturbations to F near zero produce O(1) shifts in `D_{(1)}`. None of the standard survey-bootstrap or linearization tools give a calibrated test for QUG.
   2. **The `Exp(1)/Exp(1)` limit law assumes iid sampling with smooth density at zero.** Under cluster sampling, `D_{(1)}` and `D_{(2)}` may both come from the same PSU, breaking the independence required for the Poisson-process limit of rescaled spacings near the boundary. Under stratification, the smallest dose may come from a small stratum that's systematically over- or under-sampled, biasing the test.
   3. **The literature on EVT under unequal-probability sampling is sparse.** Quintos et al. (2001) and Beirlant et al. cover tail-INDEX estimation under unequal sample sizes. There is no off-the-shelf method for "test the support endpoint under complex sampling" in the standard survey-statistics toolkit. Adapting Hill / Pickands / DEdH estimators to the boundary problem would be novel research, not engineering. The de Chaisemartin et al. (2026) paper itself does not discuss survey extensions of QUG.
-  The survey-compatible alternative for HAD pretesting is **joint Stute** (a CvM cusum of regression residuals) — a smooth functional of the empirical CDF for which Krieger-Pfeffermann (1997) + Rao-Wu rescaled bootstrap give a calibrated survey-aware test. Phase 4.5 C ships this on `stute_test`, `yatchew_hr_test`, and the joint variants.
+  The survey-compatible alternative for HAD pretesting is **joint Stute** (a CvM cusum of regression residuals) — a smooth functional of the empirical CDF for which Krieger-Pfeffermann (1997) + Rao-Wu rescaled bootstrap give a calibrated survey-aware test. Phase 4.5 C ships survey support for the linearity family with mechanism varying by test: Rao-Wu rescaled bootstrap for `stute_test` and the joint variants (`stute_joint_pretest`, `joint_pretrends_test`, `joint_homogeneity_test`); weighted OLS residuals + weighted variance estimator for `yatchew_hr_test` (Yatchew 1997 is a closed-form variance-ratio test, not bootstrap-based).
   **Research direction (out of scope for diff-diff):** the bridge IS sketchable by combining (a) endpoint-estimation EVT under iid (Hall 1982, Aarssen-de Haan 1994, Hall-Wang 1999, Beirlant-de Wet-Goegebeur 2006); (b) survey-aware functional CLT for the empirical process (Boistard-Lopuhaä-Ruiz-Gazen 2017, Bertail-Chautru-Clémençon 2017); and (c) tail-empirical-process theory (Drees 2003) to define a "design-effective boundary intensity" `λ_eff = Σ_h W_h · f_h(0+)`. Under a "no boundary clumping" assumption (`P(D_{(1)}, D_{(2)}` in same PSU `| both ≤ δ) → 0`), the `Exp(1)/Exp(1)` limit law's pivotality is preserved and only the calibration needs a survey-aware bootstrap (subsampling within strata per Politis-Romano-Wolf, or Bertail et al.'s design-aware bootstrap). This is publishable methodology research — one paper, ~6-12 months for a methods PhD student. If the bridge gets built and published externally, this gate can be revisited.
 
 *Algorithm variant - TWFE linearity test via Stute (1997) Cramér-von Mises with wild bootstrap (Section 4.3, Appendix D):*