feat: enforce self-only assignment (mandatory on create, coerced silently)

Project rule: every create_task must be assigned, and only the signed-in
user can ever be the assignee. PlannerBot coerces non-self ids to self
and the preview card surfaces the coercion with a 🔒 advisory line so the
user can see exactly what was substituted before confirm.

- prompt.ts: rewrites the 할당 section — LLM must always fill assigneeUserIds
  with the isMe user on create_task, never assign others, never ask_clarify
  about non-self assignees
- PlannerBot.ts: derives selfId from plan.members, computes coerced state
  and attempted non-self names for the card, forces finalAssigneeIds to
  [selfId] on create_task and on any update_task that signals an
  assignment change
- confirmationCard.ts: ActionContext gains assignmentCoercedToSelf +
  attemptedNonSelfNames; renders the advisory as a warning line

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

src/bot/PlannerBot.ts

@@ -91,6 +91,11 @@ export class PlannerBot extends TeamsActivityHandler {
   private readonly memoryAccessor: StatePropertyAccessor<WorkingMemory | undefined>;
   private readonly rawTurnsAccessor: StatePropertyAccessor<RawTurn[] | undefined>;
   private readonly connectionName: string;
+  /** In-process cache for Graph `/users/{id}` displayName lookups so we don't
+   *  re-hit Graph for the same assignee on every preview. Lives until the
+   *  container restarts — perfectly fine since the cache is purely a perf
+   *  optimization and recovers itself on first miss. */
+  private readonly nameCache = new Map<string, string>();
 
   constructor(deps: PlannerBotDeps) {
     super();
@@ -311,10 +316,50 @@ export class PlannerBot extends TeamsActivityHandler {
       ...appliedExplicitNames,
     ]);
 
-    // --- Assignee name resolution + sanity-filter to plan members --------
+    // --- Assignment (self-only project rule) -----------------------------
+    // Project rule: every create_task MUST be assigned, and only the signed-in
+    // user can be assigned. If the LLM tried to assign anyone else, we silently
+    // coerce to self and surface that on the preview card. update_task only
+    // touches assigneeUserIds if the LLM intended a change at all.
     const memberById = new Map(plan.members.map((m) => [m.userId, m]));
-    const validAssigneeIds = (action.assigneeUserIds ?? []).filter((id) => memberById.has(id));
-    const newAssigneeNames = validAssigneeIds.map((id) => memberById.get(id)!.displayName);
+    const knownAssigneeIds = new Set<string>([
+      ...plan.members.map((m) => m.userId),
+      ...(task?.assigneeIds ?? []),
+    ]);
+    const resolveName = (id: string) => this.resolveAssigneeName(planner, memberById, id);
+
+    const selfId = plan.members.find((m) => m.isMe)?.userId;
+    const llmRequestedAssignees = action.assigneeUserIds;
+    const llmRequestedNonSelf = (llmRequestedAssignees ?? []).filter(
+      (id) => id !== selfId,
+    );
+
+    let assignmentCoercedToSelf = false;
+    let attemptedNonSelfNames: string[] | undefined;
+    if (llmRequestedNonSelf.length > 0) {
+      assignmentCoercedToSelf = true;
+      const validNonSelf = llmRequestedNonSelf.filter((id) =>
+        knownAssigneeIds.has(id),
+      );
+      if (validNonSelf.length) {
+        attemptedNonSelfNames = await Promise.all(validNonSelf.map(resolveName));
+      }
+    }
+
+    // What we'll actually write to Planner.
+    //  - create_task: always [selfId] — assignment is mandatory
+    //  - update_task: leave undefined unless the LLM signaled an assignment
+    //                 change, in which case force [selfId]
+    let finalAssigneeIds: string[] | undefined;
+    if (action.type === "create_task") {
+      finalAssigneeIds = selfId ? [selfId] : [];
+    } else if (llmRequestedAssignees !== undefined) {
+      finalAssigneeIds = selfId ? [selfId] : [];
+    }
+    const newAssigneeNames =
+      finalAssigneeIds && finalAssigneeIds.length
+        ? await Promise.all(finalAssigneeIds.map(resolveName))
+        : [];
 
     // --- Build ActionContext for preview / result -------------------------
     const ctx: ActionContext = {
@@ -322,6 +367,8 @@ export class PlannerBot extends TeamsActivityHandler {
       appliedLabelNames: appliedLabelNames.length ? appliedLabelNames : undefined,
       droppedInferredLabels: dropped.length ? dropped : undefined,
       missingExplicitLabels: missing.length ? missing : undefined,
+      assignmentCoercedToSelf: assignmentCoercedToSelf || undefined,
+      attemptedNonSelfNames,
     };
 
     if (action.type === "create_task") {
@@ -341,11 +388,10 @@ export class PlannerBot extends TeamsActivityHandler {
       }
       ctx.currentPercent = task.percentComplete;
       ctx.currentPriority = task.priority;
-      if (action.assigneeUserIds) {
-        const currentNames = (task.assigneeIds ?? []).map(
-          (id) => memberById.get(id)?.displayName ?? id,
+      if (llmRequestedAssignees !== undefined) {
+        ctx.currentAssigneeNames = await Promise.all(
+          (task.assigneeIds ?? []).map(resolveName),
         );
-        ctx.currentAssigneeNames = currentNames;
         ctx.newAssigneeNames = newAssigneeNames;
       }
       if (action.addChecklistItems && action.addChecklistItems.length) {
@@ -356,9 +402,11 @@ export class PlannerBot extends TeamsActivityHandler {
     const pending: PendingAction = {
       action: {
         ...action,
-        ...(action.type === "create_task" ? { assigneeUserIds: validAssigneeIds } : {}),
-        ...(action.type === "update_task" && action.assigneeUserIds
-          ? { assigneeUserIds: validAssigneeIds }
+        ...(action.type === "create_task"
+          ? { assigneeUserIds: finalAssigneeIds }
+          : {}),
+        ...(action.type === "update_task" && llmRequestedAssignees !== undefined
+          ? { assigneeUserIds: finalAssigneeIds }
           : {}),
       } as Exclude<ClassifiedAction, { type: "ask_clarification" }>,
       ctx,
@@ -569,6 +617,28 @@ export class PlannerBot extends TeamsActivityHandler {
     await this.memoryAccessor.set(context, undefined);
     await this.rawTurnsAccessor.set(context, undefined);
   }
+
+  /** Resolve a user id to a displayName. Lookups in priority order:
+   *    1) plan's group member list (already in context, free)
+   *    2) instance-level nameCache (free after first miss)
+   *    3) Graph `/users/{id}` (needs delegated `User.ReadBasic.All`)
+   *    4) friendly short placeholder if all of the above fail */
+  private async resolveAssigneeName(
+    planner: PlannerClient,
+    memberById: Map<string, { displayName: string }>,
+    userId: string,
+  ): Promise<string> {
+    const member = memberById.get(userId);
+    if (member) return member.displayName;
+    const cached = this.nameCache.get(userId);
+    if (cached) return cached;
+    const looked = await planner.resolveUserDisplayName(userId);
+    if (looked) {
+      this.nameCache.set(userId, looked);
+      return looked;
+    }
+    return `사용자 ${userId.slice(0, 8)}…`;
+  }
 }
 
 // -------- Helpers -----------------------------------------------------------

src/cards/confirmationCard.ts

@@ -19,6 +19,11 @@ export interface ActionContext {
   // Assignment diff (update_task)
   currentAssigneeNames?: string[];
   newAssigneeNames?: string[];
+  /** Project rule: only self can be assigned. True when the LLM tried to assign
+   *  someone other than the signed-in user and the bot silently coerced it. */
+  assignmentCoercedToSelf?: boolean;
+  /** displayName 목록 — coerce 된 비-본인 후보들. preview 안내에 사용. */
+  attemptedNonSelfNames?: string[];
 
   // Update-only "before" values (for diff display)
   currentProgressLabel?: string;
@@ -145,6 +150,15 @@ function actionDetailLines(a: ClassifiedAction, ctx: ActionContext): { text: str
   }
 
   // Side-effect / advisory lines — apply to both create_task & update_task.
+  if (ctx.assignmentCoercedToSelf) {
+    const tried = ctx.attemptedNonSelfNames && ctx.attemptedNonSelfNames.length
+      ? ` (요청한 ${ctx.attemptedNonSelfNames.join(", ")} 은(는) 무시)`
+      : "";
+    lines.push({
+      text: `🔒 이 봇은 본인에게만 할당할 수 있어요 — 본인으로 자동 할당했습니다${tried}.`,
+      emphasis: "warning",
+    });
+  }
   if (ctx.droppedInferredLabels && ctx.droppedInferredLabels.length) {
     lines.push({
       text: `ℹ️ 추론 라벨 중 이 Plan에 없어 무시됨: ${ctx.droppedInferredLabels.join(", ")}`,

src/graph/plannerClient.ts

@@ -63,6 +63,25 @@ export class PlannerClient {
     return enriched;
   }
 
+  /** Best-effort displayName lookup for a single AAD user id. Used when an
+   *  assignee on a task isn't (or no longer is) in their plan's group member
+   *  list — guests, alumni, cross-tenant collaborators, etc. Requires the
+   *  delegated `User.ReadBasic.All` Graph scope; if missing or the lookup
+   *  fails we return undefined so the caller can show a friendly placeholder. */
+  async resolveUserDisplayName(userId: string): Promise<string | undefined> {
+    try {
+      const u = await this.graph
+        .api(`/users/${encodeURIComponent(userId)}`)
+        .select(["id", "displayName"])
+        .get();
+      return typeof u?.displayName === "string" && u.displayName.length > 0
+        ? u.displayName
+        : undefined;
+    } catch {
+      return undefined;
+    }
+  }
+
   /** Resolve owning M365 group's members. Falls back gracefully if owner missing. */
   private async fetchPlanMembers(
     planId: string,

src/llm/prompt.ts

@@ -11,6 +11,7 @@ export const SYSTEM_PROMPT = `당신은 사용자의 한국어 자연어 작업
 - 반드시 도구 호출(함수 호출)로만 응답하세요. 부가 설명, 코멘트, 마크다운은 출력하지 마세요.
 - create_task 의 planId/bucketId, update_task 의 taskId, assigneeUserIds 의 각 항목 — **모든 ID 값은 컨텍스트에 주어진 문자열을 한 글자도 빼거나 더하지 말고 그대로 복사**하세요. 콤마/공백/따옴표를 덧붙이지 마세요.
 - 컨텍스트에 없는 ID 를 만들지 마세요. 적절한 후보가 없으면 ask_clarification 으로 되묻습니다.
+- **사용자에게 보여지는 텍스트 필드(question, description, appendNote, newTitle, title, memoryUpdate.setTopic/setNotes/addOpenLoop 등)에 절대 GUID 형태의 userId/planId/bucketId/taskId 를 포함하지 마세요. 사람을 가리킬 때는 항상 displayName 으로, plan/bucket/task 는 제목으로 지칭하세요.** GUID 는 오직 planId/bucketId/taskId/newBucketId/assigneeUserIds 같은 ID 전용 필드에만 들어갑니다.
 - 발화에서 작업을 가리키는 단서가 모호하면(예: "그거 했어", "다 끝났어") 반드시 ask_clarification 을 사용하세요. 임의로 가장 최근 작업을 가정하지 마세요.
 
 ## 진행/상태 매핑 (progress, percentComplete)
@@ -35,11 +36,12 @@ export const SYSTEM_PROMPT = `당신은 사용자의 한국어 자연어 작업
 - 새 작업이면 checklistItems, 기존 작업에 덧붙이는 거면 addChecklistItems 를 사용.
 - 최대 20개. 그보다 많으면 앞 20개만.
 
-## 할당 (assigneeUserIds)
-- 반드시 컨텍스트의 plan members 목록 안에서 displayName 부분 매칭으로 사용자를 찾고, 그 userId 를 채웁니다.
-- "나/내가/제가" → members 중 isMe=true 항목의 userId.
-- 발화에 이름이 있는데 members 에 일치하는 사람이 없으면 ask_clarification.
-- update_task 에서는 assigneeUserIds 가 전체 교체로 동작합니다. "X 도 추가" 처럼 누적 의도가 분명하면 기존 assigneeIds + 새 사람을 모두 채워서 넣으세요.
+## 할당 (assigneeUserIds) — 본인만 할당 가능, 그리고 필수
+- **이 봇은 본인(members 중 isMe=true) 외에는 누구도 할당하지 못합니다. 무조건 본인 userId 한 개만 사용하세요.**
+- **모든 create_task 에 반드시 isMe=true 인 본인 userId 한 개를 assigneeUserIds 에 넣으세요.** 누락 금지(빈 배열·undefined 금지).
+- update_task 에서 할당을 바꾸려는 의도가 명확할 때(예: "이거 나한테 줘", "내가 할게")만 assigneeUserIds 에 본인 userId 한 개를 넣으세요. 변경 의도가 없으면 assigneeUserIds 를 통째로 생략해서 기존 할당을 유지합니다.
+- 발화에 다른 사람 이름이 나와도 무시하고 본인 userId 만 넣으세요. ask_clarification 으로 되묻지 마세요 — 봇이 preview 카드에서 "본인으로 자동 할당" 안내를 해 줍니다.
+- members 의 다른 사람 userId 를 절대 assigneeUserIds 에 넣지 마세요.
 
 ## 라벨 (inferredLabels vs explicitLabels)
 - **inferredLabels**: 사용자가 직접 라벨을 언급하지 않았지만 발화 의미가 plan 의 기존 라벨 중 하나와 명확히 매칭될 때만 채웁니다. 자신 없으면 비워두세요. plan 에 없는 이름은 절대 넣지 마세요.