Fix live multi-turn: pass the resolved drug, stop did-you-mean garbage

apps/ai-service/rag/routing.py

@@ -181,12 +181,10 @@ class QueryRoutingService:
         self._retrieval = retrieval
         self._resolver = resolver
 
-    def retrieve(
-        self,
-        query: str,
-        subject_scope: SubjectScope = SubjectScope.UNKNOWN,
-        intent: QueryIntent = QueryIntent.UNKNOWN,
-    ) -> RetrievalResult:
+    @staticmethod
+    def _scope_gate(
+        subject_scope: SubjectScope, intent: QueryIntent
+    ) -> RetrievalResult | None:
         # Scope comes from the API/policy layer. Unknown is deliberately
         # fail-closed; retrieval must not infer clinical scope from keywords.
         if subject_scope == SubjectScope.NON_HUMAN:
@@ -197,6 +195,41 @@ class QueryRoutingService:
             return RetrievalResult(EvidenceDecision.ABSTAIN, "recommendation_out_of_scope")
         if intent == QueryIntent.UNKNOWN:
             return RetrievalResult(EvidenceDecision.ABSTAIN, "query_intent_unknown")
+        return None
+
+    def retrieve_for_drug(
+        self,
+        query: str,
+        drug_id: str,
+        subject_scope: SubjectScope = SubjectScope.UNKNOWN,
+        intent: QueryIntent = QueryIntent.UNKNOWN,
+    ) -> RetrievalResult:
+        """Retrieve for an ALREADY-resolved drug, skipping name resolution.
+
+        The conversational layer has already resolved (and possibly inherited)
+        the drug; re-resolving from the rewritten turn text is what produced the
+        `drug_resolution_ambiguous` empty answers on follow-ups. The query text
+        still drives section routing and the intro/overview decision.
+        """
+        gate = self._scope_gate(subject_scope, intent)
+        if gate is not None:
+            return gate
+        result = self._retrieval.retrieve(query, drug_id)
+        return replace(
+            result,
+            resolved_drug_id=drug_id,
+            drug_resolution_status=DrugResolutionStatus.RESOLVED,
+        )
+
+    def retrieve(
+        self,
+        query: str,
+        subject_scope: SubjectScope = SubjectScope.UNKNOWN,
+        intent: QueryIntent = QueryIntent.UNKNOWN,
+    ) -> RetrievalResult:
+        gate = self._scope_gate(subject_scope, intent)
+        if gate is not None:
+            return gate
         resolution = self._resolver.resolve(query)
         if resolution.status == DrugResolutionStatus.NOT_FOUND:
             return RetrievalResult(