fix: deduplicate rectification question regeneration

frontend/src/lib/rectification-v4/case-service.ts

@@ -13,8 +13,17 @@ import { calculationSpecHash, evidenceSetHash } from "./fingerprints.ts";
 import { openingQuestion } from "./opening-question.ts";
 import type { RectificationV4Store } from "./store.ts";
 
-export function createRectificationV4CaseService(store: RectificationV4Store, options: { readonly now?: () => Date } = {}) {
+const regenerationInFlight = new Map<string, Promise<RectificationV4Case | null>>();
+
+export function createRectificationV4CaseService(
+  store: RectificationV4Store,
+  options: {
+    readonly now?: () => Date;
+    readonly regenerateQuestion?: typeof regenerateQuestionRealization;
+  } = {},
+) {
   const now = options.now ?? (() => new Date());
+  const realizeQuestion = options.regenerateQuestion ?? regenerateQuestionRealization;
 
   async function response(userId: string, caseValue: RectificationV4Case, jobId?: string): Promise<RectificationV4ApiResponse> {
     const [events, turns] = await Promise.all([
@@ -95,32 +104,45 @@ export function createRectificationV4CaseService(store: RectificationV4Store, op
       readonly actionId: string;
       readonly expectedCaseVersion: number;
     }) {
-      const current = await store.loadCase(input.userId, input.caseId);
-      if (!current?.currentQuestion || current.deploymentMode !== "v5_agent") return null;
-      const validated = await store.loadLatestValidatedDecision(input.userId, input.caseId);
-      const opportunity = validated?.selectedOpportunity;
-      if (!opportunity) return null;
-      const [events, turns] = await Promise.all([
-        store.loadEvents(input.userId, input.caseId),
-        store.loadTurns(input.userId, input.caseId),
-      ]);
-      const prompt = await regenerateQuestionRealization({
-        caseValue: current,
-        currentPrompt: current.currentQuestion.prompt,
-        latestAnswer: turns.at(-1)?.answer ?? "",
-        acceptedEvents: events,
-        opportunity,
-      });
-      const nextQuestion = {
-        ...current.currentQuestion,
-        id: randomUUID(),
-        prompt,
-      };
-      return response(input.userId, await store.replaceCurrentQuestion({
-        ...input,
-        question: nextQuestion,
-        now: now().toISOString(),
-      }));
+      const replay = await store.loadActionCase(input.userId, input.actionId);
+      if (replay) return response(input.userId, replay);
+
+      const key = `${input.userId}:${input.actionId}`;
+      let pending = regenerationInFlight.get(key);
+      if (!pending) {
+        pending = (async () => {
+          const secondReplay = await store.loadActionCase(input.userId, input.actionId);
+          if (secondReplay) return secondReplay;
+          const current = await store.loadCase(input.userId, input.caseId);
+          if (!current?.currentQuestion || current.deploymentMode !== "v5_agent") return null;
+          const validated = await store.loadLatestValidatedDecision(input.userId, input.caseId);
+          const opportunity = validated?.selectedOpportunity;
+          if (!opportunity) return null;
+          const [events, turns] = await Promise.all([
+            store.loadEvents(input.userId, input.caseId),
+            store.loadTurns(input.userId, input.caseId),
+          ]);
+          const prompt = await realizeQuestion({
+            caseValue: current,
+            currentPrompt: current.currentQuestion.prompt,
+            latestAnswer: turns.at(-1)?.answer ?? "",
+            acceptedEvents: events,
+            opportunity,
+          });
+          return store.replaceCurrentQuestion({
+            ...input,
+            question: { ...current.currentQuestion, id: randomUUID(), prompt },
+            now: now().toISOString(),
+          });
+        })();
+        regenerationInFlight.set(key, pending);
+      }
+      try {
+        const saved = await pending;
+        return saved ? response(input.userId, saved) : null;
+      } finally {
+        if (regenerationInFlight.get(key) === pending) regenerationInFlight.delete(key);
+      }
     },
 
     async reviseEvent(input: {

frontend/src/lib/rectification-v4/memory-store.ts

@@ -77,6 +77,10 @@ export function createRectificationV4MemoryStore(): RectificationV4Store & {
         .sort((left, right) => right.caseVersion - left.caseVersion || right.createdAt.localeCompare(left.createdAt))[0];
       return latest ? validatedDecisions.get(latest.jobId) ?? latest.validatedDecision : null;
     },
+    async loadActionCase(userId, actionId) {
+      const replay = actionResults.get(`${userId}:${actionId}`);
+      return replay ? owned(userId, replay.caseId) : null;
+    },
     async createCase(input) {
       const replay = actionResults.get(`${input.case.userId}:${input.actionId}`);
       if (replay) return owned(input.case.userId, replay.caseId);

frontend/src/lib/rectification-v4/store.ts

@@ -46,6 +46,7 @@ export interface RectificationV4Store {
   loadEvents(userId: string, caseId: string): Promise<readonly LifeEventRevision[]>;
   loadTurns(userId: string, caseId: string): Promise<readonly RectificationV4Turn[]>;
   loadLatestValidatedDecision(userId: string, caseId: string): Promise<ValidatedDecision | null>;
+  loadActionCase(userId: string, actionId: string): Promise<RectificationV4Case | null>;
   createCase(input: { readonly case: RectificationV4Case; readonly actionId: string }): Promise<RectificationV4Case>;
   replaceCurrentQuestion(input: {
     readonly userId: string;

frontend/src/lib/rectification-v4/supabase-store.ts

@@ -208,6 +208,12 @@ export function createRectificationV4SupabaseStore(supabase: SupabaseClient): Re
       if (error) throw storeError(error);
       return data ? validatedDecisionSchema.parse((data as Row).validated_decision_json) : null;
     },
+    async loadActionCase(userId, actionId) {
+      const { data, error } = await supabase.from("birth_time_rectification_v4_actions")
+        .select("case_id").eq("user_id", userId).eq("action_id", actionId).maybeSingle();
+      if (error) throw storeError(error);
+      return data ? loadCaseById(userId, String((data as Row).case_id)) : null;
+    },
     async createCase(input) {
       const id = String(await rpc("create_birth_time_rectification_v5_case", {
         p_user_id: input.case.userId,