Reject EfficientDiD covariates + survey_design combination from PR #226 review (round 11)

The DR covariate path does not thread survey weights through nuisance
estimation. Raise NotImplementedError instead of silently returning
partial results. Add test and update deferred-work table.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: igerber

diff_diff/efficient_did.py

@@ -275,6 +275,16 @@ def fit(
                 "survey_design for design-based standard errors."
             )
 
+        # Guard covariates + survey (DR path does not yet thread survey weights)
+        if covariates is not None and len(covariates) > 0 and resolved_survey is not None:
+            raise NotImplementedError(
+                "Survey weights with covariates are not yet supported for "
+                "EfficientDiD. The doubly robust covariate path does not "
+                "thread survey weights through nuisance estimation. "
+                "Use covariates=None with survey_design, or drop survey_design "
+                "when using covariates."
+            )
+
         # Normalize empty covariates list to None (use nocov path)
         if covariates is not None and len(covariates) == 0:
             covariates = None

docs/survey-roadmap.md

@@ -36,9 +36,10 @@ Phase 5 infrastructure (weighted `solve_logit()` or bootstrap+survey interaction
 | TripleDifference | IPW and DR methods + survey | Phase 5: weighted `solve_logit()` |
 | ContinuousDiD | Multiplier bootstrap + survey | Phase 5: bootstrap+survey interaction |
 | EfficientDiD | Multiplier bootstrap + survey | Phase 5: bootstrap+survey interaction |
+| EfficientDiD | Covariates (DR path) + survey | DR nuisance estimation needs survey weight threading |
 
-All four estimators raise `NotImplementedError` when the blocked combination is
-attempted, with a message pointing to the planned phase.
+All blocked combinations raise `NotImplementedError` when attempted, with a
+message pointing to the planned phase or describing the limitation.
 
 ## Phase 4: Complex Standalone Estimators
 

tests/test_survey_phase3.py

@@ -631,6 +631,24 @@ def test_bootstrap_survey_raises(self, staggered_survey_data):
                 survey_design=sd,
             )
 
+    def test_covariates_survey_raises(self, staggered_survey_data):
+        """Covariates + survey should raise NotImplementedError."""
+        from diff_diff import EfficientDiD
+
+        # Add a covariate column
+        staggered_survey_data["x1"] = np.random.randn(len(staggered_survey_data))
+        sd = SurveyDesign(weights="weight")
+        with pytest.raises(NotImplementedError, match="covariates"):
+            EfficientDiD(n_bootstrap=0).fit(
+                staggered_survey_data,
+                "outcome",
+                "unit",
+                "time",
+                "first_treat",
+                covariates=["x1"],
+                survey_design=sd,
+            )
+
     def test_survey_metadata_fields(self, staggered_survey_data):
         """survey_metadata has correct fields."""
         from diff_diff import EfficientDiD