diff --git a/backend/app/auth.py b/backend/app/auth.py
index 5bfe4b5..6ca66fb 100644
--- a/backend/app/auth.py
+++ b/backend/app/auth.py
@@ -103,15 +103,17 @@ async def _verify_token(token: str) -> dict:
 class UserContext:
     user: User
     role: str | None
-    project_id: object | None  # uuid.UUID | None
+    project_id: object | None  # uuid.UUID | None — default (first) project of a PM
+    project_ids: list  # every project this PM manages (1:N — empty for non-PMs)
     display_name: str
 
 
 async def context_from_claims(claims: dict, db: AsyncSession) -> UserContext:
-    """Auto-provision the `users` row from token claims; resolve role + PM project.
+    """Auto-provision the `users` row from token claims; resolve role + PM projects.
 
     First login: creates the row with role NULL (an admin assigns it later).
-    PMs: resolves their single project via projects.pm_user_id.
+    PMs: resolves EVERY project they manage (projects.pm_user_id = user);
+    `project_id` stays the first one (oldest) for backward compatibility.
     """
     casdoor_id = str(claims.get("sub") or claims.get("id") or "")
     if not casdoor_id:
@@ -134,13 +136,38 @@ async def context_from_claims(claims: dict, db: AsyncSession) -> UserContext:
         db.add(user)
         await db.flush()
 
-    project_id = None
+    project_ids: list = []
     if user.role == "pm":
-        project = await db.scalar(select(Project).where(Project.pm_user_id == user.id))
-        project_id = project.id if project else None
+        projects = (
+            await db.execute(
+                select(Project)
+                .where(Project.pm_user_id == user.id)
+                .order_by(Project.created_at, Project.id)
+            )
+        ).scalars().all()
+        project_ids = [p.id for p in projects]
+    project_id = project_ids[0] if project_ids else None
 
     display_name = f"{user.first_name} {user.last_name}".strip() or user.casdoor_id
-    return UserContext(user=user, role=user.role, project_id=project_id, display_name=display_name)
+    return UserContext(
+        user=user,
+        role=user.role,
+        project_id=project_id,
+        project_ids=project_ids,
+        display_name=display_name,
+    )
+
+
+async def pm_project_ids(db: AsyncSession, user: User) -> list:
+    """Every project id managed by the given PM user (oldest first)."""
+    rows = (
+        await db.execute(
+            select(Project.id)
+            .where(Project.pm_user_id == user.id)
+            .order_by(Project.created_at, Project.id)
+        )
+    ).scalars().all()
+    return list(rows)
 
 
 async def get_optional_user(request: Request, db: AsyncSession) -> UserContext | None:
diff --git a/backend/app/db/init_db.py b/backend/app/db/init_db.py
index 1b38eaf..5201498 100644
--- a/backend/app/db/init_db.py
+++ b/backend/app/db/init_db.py
@@ -302,6 +302,11 @@ _V26_DDL = [
     """
     CREATE INDEX IF NOT EXISTS idx_suppliers_category_id ON suppliers(category_id)
     """,
+    # PM → projects is 1:N (a PM may manage several projects). No UNIQUE on
+    # pm_user_id — just a lookup index for "projects of this PM" queries.
+    """
+    CREATE INDEX IF NOT EXISTS idx_projects_pm_user_id ON projects(pm_user_id)
+    """,
     # supplier_materials (v2.5) + its triggers (functions are CREATE OR REPLACE below).
     """
     CREATE TABLE IF NOT EXISTS supplier_materials (
diff --git a/backend/app/routers/auth.py b/backend/app/routers/auth.py
index 96dba62..616810b 100644
--- a/backend/app/routers/auth.py
+++ b/backend/app/routers/auth.py
@@ -20,7 +20,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from app.auth import _verify_token, context_from_claims
 from app.config import settings
 from app.db.engine import get_db
-from app.routers.users import _user_project, user_to_dict
+from app.routers.users import _user_projects, user_to_dict
 from app.utils.errors import ServiceUnavailableError, UnauthorizedError
 
 logger = logging.getLogger("procurement.auth")
@@ -74,12 +74,12 @@ async def login(payload: LoginRequest, db: AsyncSession = Depends(get_db)):
     # the app-side user (auto-provision on first login).
     claims = await _verify_token(access_token)
     ctx = await context_from_claims(claims, db)
-    project = await _user_project(db, ctx.user) if ctx.role == "pm" else None
+    projects = await _user_projects(db, ctx.user)
     return {
         "data": {
             "access_token": access_token,
             "token_type": "bearer",
             "expires_in": body.get("expires_in"),
-            "user": user_to_dict(ctx.user, project),
+            "user": user_to_dict(ctx.user, projects),
         }
     }
diff --git a/backend/app/routers/inventory.py b/backend/app/routers/inventory.py
index 8fe5602..c75f210 100644
--- a/backend/app/routers/inventory.py
+++ b/backend/app/routers/inventory.py
@@ -59,10 +59,18 @@ class Scope:
     actor: str | None
 
 
-async def inventory_scope(request: Request, db: AsyncSession = Depends(get_db)) -> Scope:
-    """Resolve the caller role/project — Casdoor JWT first, dev headers as fallback."""
-    # Primary path: Casdoor JWT. Role from users.role; PM project from
-    # projects.pm_user_id (single PM per project).
+async def inventory_scope(
+    request: Request,
+    project_id: uuid.UUID | None = Query(default=None, description="پروژه فعال (PM: داده‌های همین پروژه)"),
+    db: AsyncSession = Depends(get_db),
+) -> Scope:
+    """Resolve the caller role/project — Casdoor JWT first, dev headers as fallback.
+
+    The active project is explicit via `?project_id=…`. For a PM the backend
+    verifies they manage that project (projects.pm_user_id, 1:N); without the
+    param it falls back to their first assigned project. Admin / procurement
+    manager may pass it as a filter (no param = all projects).
+    """
     if request.headers.get("authorization"):
         user: UserContext = await get_optional_user(request, db)
         if user is not None:
@@ -70,16 +78,21 @@ async def inventory_scope(request: Request, db: AsyncSession = Depends(get_db))
                 raise ForbiddenError("نقش شما هنوز در سیستم تعیین نشده است")
             # v2.6: مدیر تدارکات = ادمین دفتر — دسترسی فقط‌خواندنی به پنل انبار.
             if user.role == "procurement_manager":
-                return Scope(role="admin", project_id=None, actor=user.display_name)
+                return Scope(role="admin", project_id=project_id, actor=user.display_name)
             if user.role not in ("pm", "admin"):
                 raise ValidationError("نقش نامعتبر است — فقط pm یا admin برای موجودی", field="role")
             if user.role == "pm":
-                if user.project_id is None:
+                allowed = list(user.project_ids or [])
+                if project_id is not None:
+                    if project_id not in allowed:
+                        raise ForbiddenError("این پروژه به شما تخصیص داده نشده است")
+                    return Scope(role="pm", project_id=project_id, actor=user.display_name)
+                if not allowed:
                     raise ValidationError(
                         "کاربر PM به هیچ پروژه‌ای متصل نیست (projects.pm_user_id)", field="project_id"
                     )
-                return Scope(role="pm", project_id=user.project_id, actor=user.display_name)
-            return Scope(role="admin", project_id=None, actor=user.display_name)
+                return Scope(role="pm", project_id=allowed[0], actor=user.display_name)
+            return Scope(role="admin", project_id=project_id, actor=user.display_name)
 
     # Dev fallback: header-based identity (fork's placeholder mode) — only
     # when an explicit X-User-Role header is sent. No auth info at all → 401.
@@ -90,13 +103,14 @@ async def inventory_scope(request: Request, db: AsyncSession = Depends(get_db))
         role = ROLE_ADMIN  # مدیر تدارکات = ادمین (فقط‌خواندنی)
     if role not in (ROLE_PM, ROLE_ADMIN):
         raise ValidationError("نقش نامعتبر است — فقط pm یا admin", field="X-User-Role")
-    raw_project = request.headers.get("x-project-id") or settings.INVENTORY_DEFAULT_PROJECT_ID
-    project_id = None
-    if raw_project:
-        try:
-            project_id = uuid.UUID(str(raw_project))
-        except ValueError:
-            raise ValidationError("شناسه پروژه نامعتبر است", field="X-Project-Id")
+    # The explicit query param wins; otherwise the dev header carries it.
+    if project_id is None:
+        raw_project = request.headers.get("x-project-id") or settings.INVENTORY_DEFAULT_PROJECT_ID
+        if raw_project:
+            try:
+                project_id = uuid.UUID(str(raw_project))
+            except ValueError:
+                raise ValidationError("شناسه پروژه نامعتبر است", field="X-Project-Id")
     if role == ROLE_PM and project_id is None:
         raise ValidationError(
             "برای نقش PM هدر X-Project-Id (پروژه مسئول) الزامی است", field="X-Project-Id"
diff --git a/backend/app/routers/pm.py b/backend/app/routers/pm.py
index 67b31f7..d5ea10f 100644
--- a/backend/app/routers/pm.py
+++ b/backend/app/routers/pm.py
@@ -29,7 +29,7 @@ from contextlib import nullcontext
 from dataclasses import dataclass
 from decimal import Decimal
 
-from fastapi import APIRouter, Depends, Request
+from fastapi import APIRouter, Depends, Query, Request
 from sqlalchemy import func, select
 from sqlalchemy.dialects.postgresql import insert as pg_insert
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -66,14 +66,20 @@ NULL_BRAND_SENTINEL = "00000000-0000-0000-0000-000000000000"
 class ArrivalScope:
     role: str  # "pm" | "admin" (admin = admin or procurement_manager)
     user_id: uuid.UUID | None
-    project_id: uuid.UUID | None  # PM's single project; None for admin
+    project_id: uuid.UUID | None  # PM's active project; admin: optional filter
     display_name: str
 
 
-async def arrivals_scope(request: Request, db: AsyncSession = Depends(get_db)) -> ArrivalScope:
+async def arrivals_scope(
+    request: Request,
+    project_id: uuid.UUID | None = Query(default=None, description="پروژه فعال (PM: الزامی برای داده‌های پروژه)"),
+    db: AsyncSession = Depends(get_db),
+) -> ArrivalScope:
     """Resolve the arrivals caller — Casdoor JWT first, dev headers as fallback.
 
-    PM → scoped to his own project. Admin / procurement manager → all projects.
+    PM → scoped to the requested project, which must be one they manage
+    (projects.pm_user_id, 1:N); without the param, their first project.
+    Admin / procurement manager → all projects (param = optional filter).
     """
     if request.headers.get("authorization"):
         ctx: UserContext | None = await get_optional_user(request, db)
@@ -81,11 +87,16 @@ async def arrivals_scope(request: Request, db: AsyncSession = Depends(get_db)) -
             if ctx.role is None:
                 raise ForbiddenError("نقش شما هنوز در سیستم تعیین نشده است")
             if ctx.role == "pm":
-                if ctx.project_id is None:
+                allowed = list(ctx.project_ids or [])
+                if project_id is not None:
+                    if project_id not in allowed:
+                        raise ForbiddenError("این پروژه به شما تخصیص داده نشده است")
+                    return ArrivalScope(role="pm", user_id=ctx.user.id, project_id=project_id, display_name=ctx.display_name)
+                if not allowed:
                     raise ForbiddenError("شما به هیچ پروژه‌ای متصل نیستید (projects.pm_user_id)")
-                return ArrivalScope(role="pm", user_id=ctx.user.id, project_id=ctx.project_id, display_name=ctx.display_name)
+                return ArrivalScope(role="pm", user_id=ctx.user.id, project_id=allowed[0], display_name=ctx.display_name)
             if ctx.role in ("admin", "procurement_manager"):
-                return ArrivalScope(role="admin", user_id=ctx.user.id, project_id=None, display_name=ctx.display_name)
+                return ArrivalScope(role="admin", user_id=ctx.user.id, project_id=project_id, display_name=ctx.display_name)
             raise ForbiddenError("این بخش فقط برای مدیر پروژه یا مدیر تدارکات است")
     # Dev fallback: X-User-Role: pm | admin (procurement_manager maps to admin)
     if not request.headers.get("x-user-role"):
@@ -95,8 +106,8 @@ async def arrivals_scope(request: Request, db: AsyncSession = Depends(get_db)) -
         role = "admin"
     if role not in ("pm", "admin"):
         raise ForbiddenError("این بخش فقط برای مدیر پروژه یا مدیر تدارکات است — هدر X-User-Role را بفرستید")
-    project_id = None
-    if role == "pm":
+    # The explicit query param wins; otherwise the dev header carries it.
+    if project_id is None and role == "pm":
         raw_project = request.headers.get("x-project-id")
         if not raw_project:
             raise ForbiddenError("هدر X-Project-Id (پروژه مسئول) الزامی است")
@@ -172,9 +183,10 @@ async def pm_on_the_way(
         .outerjoin(Project, Project.id == ItemDecision.project_id)
         .where(ItemDecision.status == "chosen")
     )
-    if ctx.role == "pm":
-        if ctx.project_id is None:
-            raise ForbiddenError("شما به هیچ پروژه‌ای متصل نیستید (projects.pm_user_id)")
+    if ctx.role == "pm" and ctx.project_id is None:
+        raise ForbiddenError("شما به هیچ پروژه‌ای متصل نیستید (projects.pm_user_id)")
+    if ctx.project_id is not None:
+        # PM: active project; admin/manager: optional project filter
         stmt = stmt.where(ItemDecision.project_id == ctx.project_id)
     decisions = (await db.execute(stmt.order_by(ItemDecision.decided_at.desc().nulls_last()))).all()
 
@@ -238,8 +250,8 @@ async def pm_confirm_receipt(
         decision = await db.get(ItemDecision, payload.item_decision_id)
         if decision is None or decision.status != "chosen":
             raise NotFoundError("تصمیم خرید یافت نشد", field="item_decision_id")
-        if ctx.role == "pm" and decision.project_id != ctx.project_id:
-            raise ForbiddenError("این قلم متعلق به پروژه شما نیست")
+        if ctx.project_id is not None and decision.project_id != ctx.project_id:
+            raise ForbiddenError("این قلم متعلق به پروژه فعال نیست")
 
         li = await db.get(LineItem, decision.line_item_id)
         quote = await db.get(Quote, li.quote_id)
@@ -436,9 +448,10 @@ async def pm_receipts(
         .join(Quote, Quote.id == LineItem.quote_id)
         .join(Project, Project.id == ItemDecision.project_id)
     )
-    if ctx.role == "pm":
-        if ctx.project_id is None:
-            raise ForbiddenError("شما به هیچ پروژه‌ای متصل نیستید (projects.pm_user_id)")
+    if ctx.role == "pm" and ctx.project_id is None:
+        raise ForbiddenError("شما به هیچ پروژه‌ای متصل نیستید (projects.pm_user_id)")
+    if ctx.project_id is not None:
+        # PM: active project; admin/manager: optional project filter
         stmt = stmt.where(ItemDecision.project_id == ctx.project_id)
     rows = (await db.execute(stmt.order_by(ItemReceipt.received_at.desc()))).all()
     receipts = [r.ItemReceipt for r in rows]
diff --git a/backend/app/routers/projects.py b/backend/app/routers/projects.py
index 3cc921b..2ebd785 100644
--- a/backend/app/routers/projects.py
+++ b/backend/app/routers/projects.py
@@ -1,19 +1,25 @@
 """Projects CRUD + per-project stats."""
-from fastapi import APIRouter, Depends, Query
+from fastapi import APIRouter, Depends, Query, Request
 from sqlalchemy import func, or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app.auth import UserContext, get_optional_user
 from app.db.engine import get_db
 from app.models.procurement import Project, Quote, User
 from app.schemas.procurement import ProjectCreate, ProjectUpdate
 from app.services.quote_service import project_stats
-from app.utils.errors import ConflictError, NotFoundError
+from app.utils.errors import ConflictError, ForbiddenError, NotFoundError, ValidationError
 from app.utils.pagination import paginate, sort_query
 from app.utils.serialization import to_date, to_iso
 
 router = APIRouter(prefix="/projects", tags=["projects"])
 
 
+async def _optional_ctx(request: Request, db: AsyncSession = Depends(get_db)) -> UserContext | None:
+    """JWT caller when present — used for RBAC on PM assignment (PATCH)."""
+    return await get_optional_user(request, db)
+
+
 async def _pm_map(db: AsyncSession, projects: list[Project]) -> dict:
     """project_id -> pm brief (v2.6: the single PM of the project)."""
     pm_ids = {p.pm_user_id for p in projects if p.pm_user_id}
@@ -91,7 +97,13 @@ async def get_project(project_id, db: AsyncSession = Depends(get_db)):
 
 
 @router.patch("/{project_id}")
-async def update_project(project_id, payload: ProjectUpdate, db: AsyncSession = Depends(get_db)):
+async def update_project(
+    project_id,
+    payload: ProjectUpdate,
+    request: Request,
+    ctx: UserContext | None = Depends(_optional_ctx),
+    db: AsyncSession = Depends(get_db),
+):
     project = await db.get(Project, project_id)
     if project is None:
         raise NotFoundError("پروژه یافت نشد")
@@ -101,6 +113,21 @@ async def update_project(project_id, payload: ProjectUpdate, db: AsyncSession =
         project.description = payload.description
     if payload.start_date is not None:
         project.start_date = payload.start_date
+    # PM assignment (1:N): one PM per project, a PM may own many projects.
+    # Admin / procurement manager only (same rule as the Organization panel).
+    if "pm_user_id" in payload.model_fields_set:
+        role = ctx.role if ctx else (request.headers.get("x-user-role") or "").strip().lower()
+        if role not in ("admin", "procurement_manager"):
+            raise ForbiddenError("تعیین مدیر پروژه فقط برای ادمین / مدیر تدارکات مجاز است")
+        if payload.pm_user_id is None:
+            project.pm_user_id = None
+        else:
+            pm_user = await db.get(User, payload.pm_user_id)
+            if pm_user is None:
+                raise NotFoundError("کاربر یافت نشد", field="pm_user_id")
+            if pm_user.role != "pm":
+                raise ValidationError("ابتدا نقش این کاربر را «مدیر پروژه» کنید", field="pm_user_id")
+            project.pm_user_id = pm_user.id
     await db.flush()
     return {"data": await project_to_dict(db, project)}
 
diff --git a/backend/app/routers/users.py b/backend/app/routers/users.py
index c9bef98..5e84675 100644
--- a/backend/app/routers/users.py
+++ b/backend/app/routers/users.py
@@ -1,12 +1,14 @@
 """Users — profile + role assignment + organization management (v2.6, Casdoor-backed).
 
 Organization panel endpoints (admin / procurement manager — same person):
-- GET  /users                — list every user with role + assigned project.
+- GET  /users                — list every user with role + assigned projects.
 - POST /users                — define a new user (manual identity, casdoor_id optional).
 - PATCH /users/{id}          — set/clear role; clearing (or switching away from
-                               «pm») also unassigns the user from their project.
-- POST /users/{id}/project   — assign/unassign the user's single project
-                               (project_id=None unassigns; one PM per project).
+                               «pm») also unassigns the user from every project.
+- POST /users/{id}/project   — assign/unassign ONE project (multi-project:
+                               other assignments are kept; project_id=None
+                               clears all; one PM per project).
+- GET  /users/me/projects    — every project assigned to the caller (PM).
 
 Role management is open to BOTH «admin» and «procurement_manager» (they are
 the same person in this system), unlike the plain require_role("admin").
@@ -41,7 +43,11 @@ USER_ROLE_LABELS = {
 }
 
 
-def user_to_dict(user: User, project: Project | None = None) -> dict:
+def user_to_dict(user: User, projects: list[Project] | None = None) -> dict:
+    """Serialize a user. `projects` = every project the PM manages (1:N);
+    project_id/project_name stay as the first (oldest) one for compatibility."""
+    projects = projects or []
+    first = projects[0] if projects else None
     return {
         "id": str(user.id),
         "casdoor_id": user.casdoor_id,
@@ -50,8 +56,9 @@ def user_to_dict(user: User, project: Project | None = None) -> dict:
         "phone": user.phone,
         "role": user.role,
         "role_label": USER_ROLE_LABELS.get(user.role) if user.role else None,
-        "project_id": str(project.id) if project else None,
-        "project_name": project.name if project else None,
+        "project_id": str(first.id) if first else None,
+        "project_name": first.name if first else None,
+        "projects": [{"id": str(p.id), "name": p.name} for p in projects],
         "created_at": to_iso(user.created_at),
     }
 
@@ -63,14 +70,28 @@ async def _org_manager(ctx: UserContext = Depends(get_current_user)) -> UserCont
     return ctx
 
 
-async def _user_project(db: AsyncSession, user: User) -> Project | None:
+async def _user_projects(db: AsyncSession, user: User) -> list[Project]:
+    """Every project the user manages as PM (oldest first; [] for non-PMs)."""
     if user.role != "pm":
-        return None
-    return await db.scalar(select(Project).where(Project.pm_user_id == user.id))
+        return []
+    rows = (
+        await db.execute(
+            select(Project)
+            .where(Project.pm_user_id == user.id)
+            .order_by(Project.created_at, Project.id)
+        )
+    ).scalars().all()
+    return list(rows)
+
+
+async def _user_project(db: AsyncSession, user: User) -> Project | None:
+    """First (oldest) project of a PM — legacy single-project view."""
+    projects = await _user_projects(db, user)
+    return projects[0] if projects else None
 
 
 async def _unassign_projects(db: AsyncSession, user_id) -> None:
-    """Clear the user's pm assignment on every project (one project per PM)."""
+    """Clear the user's pm assignment on every project (role revocation)."""
     await db.execute(
         update(Project).where(Project.pm_user_id == user_id).values(pm_user_id=None)
     )
@@ -104,8 +125,19 @@ async def _casdoor_users() -> list[dict]:
 
 @router.get("/me")
 async def me(ctx: UserContext = Depends(get_current_user), db: AsyncSession = Depends(get_db)):
-    project = await _user_project(db, ctx.user) if ctx.role == "pm" else None
-    return {"data": user_to_dict(ctx.user, project)}
+    projects = await _user_projects(db, ctx.user)
+    return {"data": user_to_dict(ctx.user, projects)}
+
+
+@router.get("/me/projects")
+async def my_projects(ctx: UserContext = Depends(get_current_user), db: AsyncSession = Depends(get_db)):
+    """Every project assigned to the caller (empty list for non-PM roles).
+
+    Drives the PM project switcher: the frontend validates its persisted
+    active project against this list and falls back gracefully when a
+    project is revoked."""
+    projects = await _user_projects(db, ctx.user)
+    return {"data": [{"id": str(p.id), "name": p.name} for p in projects]}
 
 
 @router.get("")
@@ -113,15 +145,22 @@ async def list_users(
     _: UserContext = Depends(_org_manager),
     db: AsyncSession = Depends(get_db),
 ):
-    """Every user (with role + assigned project) — Organization panel."""
+    """Every user (with role + assigned projects) — Organization panel."""
     users = (await db.execute(select(User).order_by(User.created_at))).scalars().all()
     pm_ids = {u.id for u in users if u.role == "pm"}
-    projects: dict = {}
+    by_user: dict = {}
     if pm_ids:
-        projs = (await db.execute(select(Project).where(Project.pm_user_id.in_(pm_ids)))).scalars().all()
-        projects = {p.pm_user_id: p for p in projs}
+        projs = (
+            await db.execute(
+                select(Project)
+                .where(Project.pm_user_id.in_(pm_ids))
+                .order_by(Project.created_at, Project.id)
+            )
+        ).scalars().all()
+        for p in projs:
+            by_user.setdefault(p.pm_user_id, []).append(p)
     return {
-        "data": [user_to_dict(u, projects.get(u.id)) for u in users],
+        "data": [user_to_dict(u, by_user.get(u.id, [])) for u in users],
         "meta": {"total": len(users)},
     }
 
@@ -166,8 +205,8 @@ async def update_user_role(
         await _unassign_projects(db, user.id)
     user.role = payload.role
     await db.flush()
-    project = await _user_project(db, user)
-    return {"data": user_to_dict(user, project)}
+    projects = await _user_projects(db, user)
+    return {"data": user_to_dict(user, projects)}
 
 
 @router.post("/sync")
@@ -204,12 +243,19 @@ async def sync_casdoor_users(
 
     users = (await db.execute(select(User).order_by(User.created_at))).scalars().all()
     pm_ids = {u.id for u in users if u.role == "pm"}
-    projects: dict = {}
+    by_user: dict = {}
     if pm_ids:
-        projs = (await db.execute(select(Project).where(Project.pm_user_id.in_(pm_ids)))).scalars().all()
-        projects = {p.pm_user_id: p for p in projs}
+        projs = (
+            await db.execute(
+                select(Project)
+                .where(Project.pm_user_id.in_(pm_ids))
+                .order_by(Project.created_at, Project.id)
+            )
+        ).scalars().all()
+        for p in projs:
+            by_user.setdefault(p.pm_user_id, []).append(p)
     return {
-        "data": [user_to_dict(u, projects.get(u.id)) for u in users],
+        "data": [user_to_dict(u, by_user.get(u.id, [])) for u in users],
         "meta": {"total": len(users), "created": created},
     }
 
@@ -221,11 +267,13 @@ async def assign_user_project(
     _: UserContext = Depends(_org_manager),
     db: AsyncSession = Depends(get_db),
 ):
-    """Assign the user as PM of one project (project_id=None unassigns).
+    """Assign the user as PM of ONE project (multi-project aware).
 
-    Rules: the user must hold the «pm» role; a PM manages ONE project at a
-    time (assignment on other projects is cleared); assigning a new PM to a
-    project replaces the previous PM there.
+    - project_id given: that project gets this PM (a previous PM there is
+      replaced); the user's OTHER project assignments are kept.
+    - project_id=None: clears ALL of the user's project assignments.
+
+    Rules: the user must hold the «pm» role; a project has at most one PM.
     """
     user = await db.get(User, user_id)
     if user is None:
@@ -233,8 +281,8 @@ async def assign_user_project(
     if user.role != "pm":
         raise ValidationError("ابتدا نقش این کاربر را «مدیر پروژه» کنید", field="role")
 
-    await _unassign_projects(db, user.id)
     if payload.project_id is None:
+        await _unassign_projects(db, user.id)
         await db.flush()
         return {"data": user_to_dict(user)}
 
@@ -243,4 +291,4 @@ async def assign_user_project(
         raise NotFoundError("پروژه یافت نشد", field="project_id")
     project.pm_user_id = user.id
     await db.flush()
-    return {"data": user_to_dict(user, project)}
+    return {"data": user_to_dict(user, await _user_projects(db, user))}
diff --git a/backend/app/schemas/procurement.py b/backend/app/schemas/procurement.py
index 352e047..4d4946b 100644
--- a/backend/app/schemas/procurement.py
+++ b/backend/app/schemas/procurement.py
@@ -52,6 +52,9 @@ class ProjectUpdate(APIModel):
     name: str | None = Field(default=None, min_length=1)
     description: str | None = None
     start_date: date | None = None
+    # PM assignment (1:N — one PM per project, a PM may own many projects).
+    # Admin / procurement manager only; None unassigns this project's PM.
+    pm_user_id: UUID | None = None
 
 
 # ---------------------------------------------------------------------------
@@ -210,7 +213,11 @@ class UserRoleUpdate(APIModel):
 
 
 class UserProjectUpdate(APIModel):
-    """Assign/unassign the user's single project (project_id=None unassigns)."""
+    """Assign the user to one project (multi-project aware).
+
+    project_id given → that project gets this PM (previous PM replaced,
+    the user's other projects kept); None → clears every assignment.
+    """
 
     project_id: UUID | None = None
 
diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index 36381ee..2b0ed8b 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -2,6 +2,7 @@ import { lazy, Suspense } from "react";
 import { Navigate, Route, Routes } from "react-router-dom";
 import { useAuthStore } from "./store/auth";
 import { ErrorBoundary } from "./components/ErrorBoundary";
+import { RequirePmProjects } from "./components/RequirePmProjects";
 
 // هر صفحه با React.lazy لود می‌شود (code splitting)
 const DashboardPage = lazy(() =>
@@ -141,7 +142,9 @@ export default function App() {
           path="/inventory"
           element={
             <RequireAuth>
-              <InventoryPage />
+              <RequirePmProjects>
+                <InventoryPage />
+              </RequirePmProjects>
             </RequireAuth>
           }
         />
@@ -149,7 +152,9 @@ export default function App() {
           path="/inventory/arrivals"
           element={
             <RequireAuth>
-              <ArrivalsPage />
+              <RequirePmProjects>
+                <ArrivalsPage />
+              </RequirePmProjects>
             </RequireAuth>
           }
         />
@@ -157,7 +162,9 @@ export default function App() {
           path="/inventory/change"
           element={
             <RequireAuth>
-              <ChangeInventoryPage />
+              <RequirePmProjects>
+                <ChangeInventoryPage />
+              </RequirePmProjects>
             </RequireAuth>
           }
         />
@@ -165,7 +172,9 @@ export default function App() {
           path="/inventory/daily"
           element={
             <RequireAuth>
-              <DailyControlPage />
+              <RequirePmProjects>
+                <DailyControlPage />
+              </RequirePmProjects>
             </RequireAuth>
           }
         />
@@ -173,7 +182,9 @@ export default function App() {
           path="/inventory/warehouses"
           element={
             <RequireAuth>
-              <WarehousesPage />
+              <RequirePmProjects>
+                <WarehousesPage />
+              </RequirePmProjects>
             </RequireAuth>
           }
         />
@@ -181,7 +192,9 @@ export default function App() {
           path="/inventory/org"
           element={
             <RequireAuth>
-              <OrganizationPage />
+              <RequirePmProjects>
+                <OrganizationPage />
+              </RequirePmProjects>
             </RequireAuth>
           }
         />
diff --git a/frontend/src/components/AppSwitcherMenu.tsx b/frontend/src/components/AppSwitcherMenu.tsx
index 395935c..0108841 100644
--- a/frontend/src/components/AppSwitcherMenu.tsx
+++ b/frontend/src/components/AppSwitcherMenu.tsx
@@ -1,9 +1,14 @@
-import { PanelMenu } from "./PanelMenu";
+import { useLocation } from "react-router-dom";
+import { PanelMenu, type MenuItem } from "./PanelMenu";
 import { useLogout } from "../pages/Inventory/panelMenu";
+import { useAuthStore } from "../store/auth";
 
 // منوی همبرگری مشترک بین دو ماژول (پنل انبار / دفتر تدارکات) —
 // دقیقاً مثل منوی دفتر: عنوان «پنل‌ها»، ماژول فعلی با استایل فعال (پر)
 // + «✓ فعلی»، ماژول دیگر به‌عنوان سوییچر، و در پایان جداکننده + خروج.
+// مدیر پروژه (1:N): زیر «مدیریت انبار» یک آکاردئون باز می‌شود که همه‌ی
+// پروژه‌های تخصیص‌یافته را نشان می‌دهد؛ پروژه‌ی فعال با «✓ فعلی» مشخص است و
+// انتخاب هر پروژه فقط «پروژه‌ی فعال» را عوض می‌کند (نشست/توکن دست‌نخورده).
 export function AppSwitcherMenu({
   activeModule,
   canSwitchToProcurement = true,
@@ -12,13 +17,28 @@ export function AppSwitcherMenu({
   canSwitchToProcurement?: boolean; // مدیر پروژه به دفتر تدارکات دسترسی ندارد
 }) {
   const logout = useLogout();
-  const items = [];
+  const { pathname } = useLocation();
+  const user = useAuthStore((s) => s.user);
+  const setActiveProject = useAuthStore((s) => s.setActiveProject);
+  const items: MenuItem[] = [];
+
+  const isPm = user?.role === "pm";
+  const pmProjects = isPm ? user?.projects ?? [] : [];
+  const projectChildren: MenuItem[] | undefined =
+    activeModule === "warehouse" && isPm
+      ? pmProjects.map((p) => ({
+          label: p.name,
+          to: pathname, // همان بخش فعلی؛ فقط پروژه عوض می‌شود
+          active: p.id === user?.project_id,
+          onClick: () => setActiveProject(p.id),
+        }))
+      : undefined;
 
   if (activeModule === "procurement") {
     items.push({ label: "مدیریت انبار", to: "/inventory" });
     items.push({ label: "مدیریت تدارکات", to: "/", active: true });
   } else {
-    items.push({ label: "مدیریت انبار", to: "/inventory", active: true });
+    items.push({ label: "مدیریت انبار", to: "/inventory", active: true, children: projectChildren });
     if (canSwitchToProcurement) {
       items.push({ label: "مدیریت تدارکات", to: "/" });
     }
diff --git a/frontend/src/components/PanelMenu.tsx b/frontend/src/components/PanelMenu.tsx
index 6b1c792..1396369 100644
--- a/frontend/src/components/PanelMenu.tsx
+++ b/frontend/src/components/PanelMenu.tsx
@@ -1,6 +1,6 @@
 import { useEffect, useRef, useState } from "react";
 import { Link } from "react-router-dom";
-import { Menu, X } from "lucide-react";
+import { ChevronDown, Menu, X } from "lucide-react";
 import { cn } from "../lib/utils";
 
 export interface MenuItem {
@@ -9,11 +9,14 @@ export interface MenuItem {
   active?: boolean;
   divider?: boolean;
   onClick?: () => void;
+  // آیتم بازشو (آکاردئونی) — مثلاً فهرست پروژه‌های مدیر پروژه زیر «مدیریت انبار»
+  children?: MenuItem[];
 }
 
 // منوی همبرگری — بالای راست صفحات؛ نمایش پنل فعلی + ناوبری بین پنل‌ها
 export function PanelMenu({ items, title }: { items: MenuItem[]; title?: string }) {
   const [open, setOpen] = useState(false);
+  const [expanded, setExpanded] = useState<number | null>(null);
   const ref = useRef<HTMLDivElement>(null);
 
   useEffect(() => {
@@ -42,11 +45,81 @@ export function PanelMenu({ items, title }: { items: MenuItem[]; title?: string
           {items.map((it, i) =>
             it.divider ? (
               <div key={i} className="my-1 border-t border-line" />
+            ) : it.children?.length ? (
+              <div key={i}>
+                <div className={cn("flex items-center rounded-lg", it.active && "bg-accent")}>
+                  {it.to ? (
+                    <Link
+                      to={it.to}
+                      onClick={() => {
+                        setOpen(false);
+                        it.onClick?.();
+                      }}
+                      className={cn(
+                        "flex flex-1 items-center justify-between gap-3 rounded-lg px-3 py-2 text-[13px] no-underline",
+                        it.active ? "font-bold text-white" : "text-ink hover:bg-slate-bg",
+                      )}
+                    >
+                      {it.label}
+                      {it.active && <span className="text-[10px] opacity-80">✓ فعلی</span>}
+                    </Link>
+                  ) : (
+                    <button
+                      type="button"
+                      onClick={() => {
+                        setOpen(false);
+                        it.onClick?.();
+                      }}
+                      className="flex flex-1 items-center gap-3 rounded-lg px-3 py-2 text-start text-[13px] text-ink hover:bg-slate-bg"
+                    >
+                      {it.label}
+                    </button>
+                  )}
+                  <button
+                    type="button"
+                    aria-label={expanded === i ? "بستن فهرست پروژه‌ها" : "نمایش پروژه‌ها"}
+                    aria-expanded={expanded === i}
+                    onClick={() => setExpanded(expanded === i ? null : i)}
+                    className={cn(
+                      "me-1 inline-flex h-7 w-7 shrink-0 cursor-pointer items-center justify-center rounded-md",
+                      it.active ? "text-white hover:bg-white/15" : "text-muted hover:bg-slate-bg",
+                    )}
+                  >
+                    <ChevronDown
+                      className={cn("h-4 w-4 transition-transform", expanded === i && "rotate-180")}
+                    />
+                  </button>
+                </div>
+                {expanded === i && (
+                  <div className="mt-0.5 flex flex-col gap-0.5 border-s border-line ps-2 ms-3">
+                    {it.children.map((c, j) => (
+                      <Link
+                        key={j}
+                        to={c.to ?? "#"}
+                        onClick={() => {
+                          setOpen(false);
+                          c.onClick?.();
+                        }}
+                        className={cn(
+                          "flex items-center justify-between gap-2 rounded-lg px-2.5 py-1.5 text-[12.5px] no-underline",
+                          c.active ? "bg-accent-bg font-bold text-accent" : "text-ink hover:bg-slate-bg",
+                        )}
+                      >
+                        <span className="truncate">{c.label}</span>
+                        {c.active && <span className="shrink-0 text-[10px]">✓ فعلی</span>}
+                      </Link>
+                    ))}
+                  </div>
+                )}
+              </div>
             ) : it.to ? (
               <Link
                 key={i}
                 to={it.to}
-                onClick={() => setOpen(false)}
+                onClick={() => {
+                  setOpen(false);
+                  it.onClick?.();
+                }}
                 className={cn(
                   "flex items-center justify-between gap-3 rounded-lg px-3 py-2 text-[13px] no-underline",
                   it.active ? "bg-accent font-bold text-white" : "text-ink hover:bg-slate-bg",
diff --git a/frontend/src/components/ProjectMultiSelect.tsx b/frontend/src/components/ProjectMultiSelect.tsx
new file mode 100644
index 0000000..a67d9e4
--- /dev/null
+++ b/frontend/src/components/ProjectMultiSelect.tsx
@@ -0,0 +1,129 @@
+import { useMemo, useRef, useState } from "react";
+import { X } from "lucide-react";
+import { normalize } from "../lib/normalize";
+import { cn } from "../lib/utils";
+import { useClickOutside } from "./useClickOutside";
+
+export interface ProjectOption {
+  id: string;
+  name: string;
+}
+
+// چند-انتخابیِ جست‌وجوپذیرِ پروژه‌ها (1:N — مدیر پروژه ↔ پروژه‌ها):
+//  - چیپ‌های پروژه با دکمه‌ی × (جداسازی فوری مدیر از پروژه)
+//  - جست‌وجوی زنده‌ی فارسی (normalize: ی/ك عربی، نیم‌فاصله و فاصله‌ها)
+//  - پروژه‌های انتخاب‌شده از فهرست پنهان می‌شوند تا انتخاب تکراری رخ ندهد
+export function ProjectMultiSelect({
+  options,
+  values,
+  onChange,
+  placeholder = "انتخاب پروژه(ها)...",
+  disabled = false,
+}: {
+  options: ProjectOption[];
+  values: string[];
+  onChange: (ids: string[]) => void;
+  placeholder?: string;
+  disabled?: boolean;
+}) {
+  const [text, setText] = useState("");
+  const [open, setOpen] = useState(false);
+  const inputRef = useRef<HTMLInputElement | null>(null);
+  const ref = useClickOutside<HTMLDivElement>(() => {
+    setOpen(false);
+    setText("");
+  });
+
+  const byId = useMemo(() => new Map(options.map((o) => [o.id, o])), [options]);
+  const selected = values.map((id) => byId.get(id)).filter(Boolean) as ProjectOption[];
+  const q = normalize(text);
+  const available = useMemo(
+    () =>
+      options.filter((o) => !values.includes(o.id) && (!q || normalize(o.name).includes(q))),
+    [options, values, q],
+  );
+
+  const add = (id: string) => {
+    onChange([...values, id]);
+    setText("");
+    inputRef.current?.focus();
+  };
+  const remove = (id: string) => onChange(values.filter((v) => v !== id));
+
+  return (
+    <div ref={ref} className="relative min-w-52">
+      <div
+        className={cn(
+          "flex min-h-9 flex-wrap items-center gap-1 rounded-lg border border-line bg-panel px-2 py-1 text-[12px]",
+          disabled ? "opacity-60" : "cursor-text",
+        )}
+        onClick={() => {
+          if (!disabled) {
+            setOpen(true);
+            inputRef.current?.focus();
+          }
+        }}
+      >
+        {selected.map((p) => (
+          <span
+            key={p.id}
+            className="inline-flex max-w-full items-center gap-1 rounded-md bg-accent-bg px-2 py-0.5 font-semibold text-accent"
+          >
+            <span className="truncate">{p.name}</span>
+            {!disabled && (
+              <button
+                type="button"
+                aria-label={`جدا کردن ${p.name}`}
+                onClick={(e) => {
+                  e.stopPropagation();
+                  remove(p.id);
+                }}
+                className="cursor-pointer rounded p-0.5 hover:bg-accent/10"
+              >
+                <X className="h-3 w-3" />
+              </button>
+            )}
+          </span>
+        ))}
+        <input
+          ref={inputRef}
+          type="text"
+          dir="rtl"
+          disabled={disabled}
+          value={text}
+          onChange={(e) => {
+            setText(e.target.value);
+            setOpen(true);
+          }}
+          onFocus={() => setOpen(true)}
+          placeholder={selected.length ? "" : placeholder}
+          className="h-7 min-w-24 flex-1 border-0 bg-transparent px-1 text-[12px] outline-none placeholder:text-muted/70"
+        />
+      </div>
+      {open && !disabled && (
+        <div className="absolute z-40 mt-1 max-h-56 w-full min-w-52 overflow-auto rounded-xl border border-line bg-panel p-1 shadow-lg">
+          {available.length ? (
+            available.map((o) => (
+              <button
+                key={o.id}
+                type="button"
+                onClick={() => add(o.id)}
+                className="flex w-full cursor-pointer items-center rounded-lg px-2.5 py-1.5 text-start text-[12.5px] text-ink hover:bg-slate-bg"
+              >
+                {o.name}
+              </button>
+            ))
+          ) : (
+            <div className="px-2.5 py-2 text-[11.5px] text-muted">
+              {options.length === 0
+                ? "پروژه‌ای وجود ندارد"
+                : q
+                  ? "پروژه‌ای یافت نشد"
+                  : "همه‌ی پروژه‌ها متصل شده‌اند"}
+            </div>
+          )}
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/frontend/src/components/RequirePmProjects.tsx b/frontend/src/components/RequirePmProjects.tsx
new file mode 100644
index 0000000..7e1707e
--- /dev/null
+++ b/frontend/src/components/RequirePmProjects.tsx
@@ -0,0 +1,80 @@
+import { useEffect, useState, type ReactNode } from "react";
+import { apiV26 } from "../lib/api";
+import { useAuthStore } from "../store/auth";
+import { useLogout } from "../pages/Inventory/panelMenu";
+
+// گیتِ پروژه‌های مدیر پروژه (PM → 1:N):
+//  - لیست پروژه‌های تخصیص‌یافته را از بک‌اند می‌گیرد و پروژه‌ی فعالِ ذخیره‌شده را
+//    اعتبارسنجی می‌کند؛ اگر پروژه باطل شده باشد به اولین پروژه برمی‌گردد
+//    (localStorage هم با همان store به‌روز می‌شود).
+//  - اگر هیچ پروژه‌ای تخصیص نیافته باشد: صفحه‌ی خالی با پیام + دکمه‌ی خروج
+//    (بدون حلقه‌ی ریدایرکت و بدون باطل‌کردن نشست).
+//  - حالت توسعه (بدون توکن) از همین پروژه‌ی انتخابیِ dev استفاده می‌کند.
+export function RequirePmProjects({ children }: { children: ReactNode }) {
+  const user = useAuthStore((s) => s.user);
+  const isDev = useAuthStore((s) => s.isDev);
+  const setProjects = useAuthStore((s) => s.setProjects);
+  const logout = useLogout();
+
+  const isPm = user?.role === "pm";
+  const [state, setState] = useState<"loading" | "ok" | "empty">(isPm ? "loading" : "ok");
+
+  useEffect(() => {
+    if (!user || user.role !== "pm") {
+      setState("ok");
+      return;
+    }
+    if (isDev) {
+      setState(user.project_id ? "ok" : "empty");
+      return;
+    }
+    let alive = true;
+    setState("loading");
+    void apiV26.users
+      .myProjects()
+      .then((list) => {
+        if (!alive) return;
+        setProjects(list); // پروژه‌ی فعال را اعتبارسنجی/جایگزین می‌کند
+        setState(list.length ? "ok" : "empty");
+      })
+      .catch(() => {
+        // خطای شبکه نباید کاربر را قفل کند — با وضعیت فعلی ادامه می‌دهیم
+        if (alive) setState("ok");
+      });
+    return () => {
+      alive = false;
+    };
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [user?.id, user?.role, isDev]);
+
+  if (state === "loading") {
+    return (
+      <div className="flex min-h-screen items-center justify-center text-sm text-muted">
+        در حال بارگذاری پروژه‌ها…
+      </div>
+    );
+  }
+
+  if (state === "empty") {
+    return (
+      <div className="flex min-h-screen items-center justify-center bg-bg px-4">
+        <div className="w-full max-w-md rounded-2xl border border-line bg-panel p-8 text-center shadow-sm">
+          <h1 className="text-[16px] font-extrabold">هیچ پروژه‌ای به شما تخصیص داده نشده است</h1>
+          <p className="mt-2 text-[12.5px] leading-6 text-muted">
+            در حال حاضر هیچ پروژه‌ای به شما تخصیص داده نشده است. برای دسترسی به پنل انبار، از مدیر
+            سیستم بخواهید پروژه‌ای را به شما اختصاص دهد.
+          </p>
+          <button
+            type="button"
+            onClick={logout}
+            className="mt-5 inline-flex h-10 w-full cursor-pointer items-center justify-center rounded-lg bg-accent px-4 text-[13px] font-bold text-white transition-colors hover:bg-accent-dark"
+          >
+            خروج از حساب
+          </button>
+        </div>
+      </div>
+    );
+  }
+
+  return <>{children}</>;
+}
diff --git a/frontend/src/lib/api.ts b/frontend/src/lib/api.ts
index b52bfde..29ebbdf 100644
--- a/frontend/src/lib/api.ts
+++ b/frontend/src/lib/api.ts
@@ -69,6 +69,19 @@ function authHeaders(init?: RequestInit): Record<string, string> {
   return headers;
 }
 
+// پروژه‌ی فعالِ مدیر پروژه (چند-پروژه‌ای، 1:N): برای همه‌ی مسیرهای پنل انبار
+// صریحاً ارسال می‌شود تا بک‌اند داده‌های همان پروژه را برگرداند/اعتبارسنجی کند.
+// ادمین/مدیر تدارکات بدون پارامتر (همه‌ی پروژه‌ها) باقی می‌ماند.
+function activeProjectId(): string | null {
+  const { user } = useAuthStore.getState();
+  return user?.role === "pm" ? user.project_id : null;
+}
+
+function projectQuery(projectId?: string | null): string {
+  const pid = projectId ?? activeProjectId();
+  return pid ? `?project_id=${pid}` : "";
+}
+
 // ترجمه‌ی پیام‌های رایج اعتبارسنجی FastAPI (422) به فارسی
 const VALIDATION_FA = (msg: string): string => {
   const lower = msg.toLowerCase();
@@ -1450,6 +1463,8 @@ export interface UserRow {
   role_label: string | null;
   project_id: string | null;
   project_name: string | null;
+  // 1:N — every project this PM manages (oldest first).
+  projects?: { id: string; name: string }[];
   created_at: string;
 }
 
@@ -1476,6 +1491,7 @@ export const apiV26 = {
             role_label: string | null;
             project_id: string | null;
             project_name: string | null;
+            projects?: { id: string; name: string }[];
           };
         };
       }>("/auth/login", { method: "POST", body: JSON.stringify(body) });
@@ -1507,6 +1523,7 @@ export const apiV26 = {
         id: string; casdoor_id: string; first_name: string; last_name: string; phone: string | null;
         role: "pm" | "procurement_manager" | "admin" | null; role_label: string | null;
         project_id: string | null; project_name: string | null;
+        projects?: { id: string; name: string }[];
       }>("/users/me");
       return {
         id: data.id,
@@ -1518,9 +1535,13 @@ export const apiV26 = {
         role_label: data.role_label,
         project_id: data.project_id,
         project_name: data.project_name,
+        projects: data.projects ?? [],
         display_name: `${data.first_name} ${data.last_name}`.trim() || data.casdoor_id,
       };
     },
+    // پروژه‌های تخصیص‌یافته به کاربر جاری (PM) — مبنای سوییچر پروژه + اعتبارسنجی
+    myProjects: async (): Promise<{ id: string; name: string }[]> =>
+      getData<{ id: string; name: string }[]>("/users/me/projects"),
     // --- Organization panel (admin / procurement manager) ---
     list: async (): Promise<UserRow[]> => {
       const data = await getData<UserRow[]>("/users");
@@ -1543,33 +1564,44 @@ export const apiV26 = {
     },
   },
 
+  // 1:N تخصیص مدیر پروژه ↔ پروژه: هر پروژه حداکثر یک PM دارد؛
+  // pm_user_id=null یعنی جداسازی مدیر از پروژه. فقط ادمین/مدیر تدارکات.
+  projects: {
+    setPm: async (projectId: string, userId: string | null): Promise<void> => {
+      await patchData(`/projects/${projectId}`, { pm_user_id: userId });
+    },
+  },
+
   warehouses: {
     list: async (projectId?: string): Promise<Warehouse[]> => {
-      const qs = projectId ? `?project_id=${projectId}&page_size=100` : "?page_size=100";
+      const pid = projectId ?? activeProjectId() ?? undefined;
+      const qs = pid ? `?project_id=${pid}&page_size=100` : "?page_size=100";
       const data = await getData<Parameters<typeof rawWarehouse>[0][]>(`/inventory/warehouses${qs}`);
       return data.map(rawWarehouse);
     },
     create: async (body: { project_id: string; name: string; description?: string | null }): Promise<Warehouse> => {
-      const d = await postData<Parameters<typeof rawWarehouse>[0]>("/inventory/warehouses", body);
+      const d = await postData<Parameters<typeof rawWarehouse>[0]>(`/inventory/warehouses${projectQuery()}`, body);
       return rawWarehouse(d);
     },
     update: async (id: string, body: { name?: string; description?: string | null; project_id?: string }): Promise<Warehouse> => {
-      const d = await patchData<Parameters<typeof rawWarehouse>[0]>(`/inventory/warehouses/${id}`, body);
+      const d = await patchData<Parameters<typeof rawWarehouse>[0]>(`/inventory/warehouses/${id}${projectQuery()}`, body);
       return rawWarehouse(d);
     },
     delete: async (id: string): Promise<void> => {
-      await deleteData(`/inventory/warehouses/${id}`);
+      await deleteData(`/inventory/warehouses/${id}${projectQuery()}`);
     },
   },
 
   inventory: {
     list: async (params: { project_id?: string; category_id?: string; warehouse_id?: string; material_id?: string; sort?: string } = {}): Promise<InventoryRow[]> => {
-      const qs = new URLSearchParams({ page_size: "100", ...cleanParams(params) }).toString();
+      const pid = params.project_id ?? activeProjectId() ?? undefined;
+      const qs = new URLSearchParams({ page_size: "100", ...cleanParams({ ...params, project_id: pid }) }).toString();
       const data = await getData<Parameters<typeof rawInventory>[0][]>(`/inventory?${qs}`);
       return data.map(rawInventory);
     },
     transactions: async (params: { project_id?: string; warehouse_id?: string; transaction_type?: string; date_from?: string; date_to?: string; sort?: string } = {}): Promise<InventoryTransaction[]> => {
-      const qs = new URLSearchParams({ page_size: "100", ...cleanParams(params) }).toString();
+      const pid = params.project_id ?? activeProjectId() ?? undefined;
+      const qs = new URLSearchParams({ page_size: "100", ...cleanParams({ ...params, project_id: pid }) }).toString();
       return getData<InventoryTransaction[]>(`/inventory/transactions?${qs}`);
     },
     createTransaction: async (body: {
@@ -1578,26 +1610,34 @@ export const apiV26 = {
       physical_qty?: number | null; unit_id?: number | null; specs?: Record<string, string> | null;
       note?: string | null; transaction_date?: string | null;
     }): Promise<InventoryTransaction[]> => {
-      return postData<InventoryTransaction[]>("/inventory/transactions", body);
+      return postData<InventoryTransaction[]>(`/inventory/transactions${projectQuery()}`, body);
     },
     types: async (): Promise<{ type: TransactionType; label: string }[]> => {
       return getData<{ type: TransactionType; label: string }[]>("/inventory/meta/types");
     },
     materialOptions: async (category_id: string, warehouse_id?: string): Promise<{ id: string; name: string; brands: { id: string; name: string }[] }[]> => {
-      const qs = warehouse_id ? `?category_id=${category_id}&warehouse_id=${warehouse_id}` : `?category_id=${category_id}`;
-      return getData<{ id: string; name: string; brands: { id: string; name: string }[] }[]>(`/inventory/materials/options${qs}`);
+      const params: Record<string, string> = { category_id };
+      if (warehouse_id) params.warehouse_id = warehouse_id;
+      const pid = activeProjectId();
+      if (pid) params.project_id = pid;
+      return getData<{ id: string; name: string; brands: { id: string; name: string }[] }[]>(
+        `/inventory/materials/options?${new URLSearchParams(params).toString()}`,
+      );
     },
   },
 
   pm: {
-    onTheWay: async (): Promise<PendingArrival[]> => getData<PendingArrival[]>("/pm/on-the-way"),
+    // پروژه فعال به‌صورت صریح ارسال می‌شود؛ بک‌اند تعلق آن به PM را بررسی می‌کند
+    onTheWay: async (projectId?: string | null): Promise<PendingArrival[]> =>
+      getData<PendingArrival[]>(projectId ? `/pm/on-the-way?project_id=${projectId}` : "/pm/on-the-way"),
     confirmReceipt: async (body: {
       item_decision_id: string; received_qty: number;
       allocations: { warehouse_id: string; quantity: number }[];
       received_at?: string | null; on_time?: boolean | null; quality_note?: string | null;
-    }): Promise<{ receipt_id: string; state: string; posted_transactions: string[] }> =>
-      postData("/pm/receipts", body),
-    receipts: async (): Promise<ConfirmedReceipt[]> => getData<ConfirmedReceipt[]>("/pm/receipts"),
+    }, projectId?: string | null): Promise<{ receipt_id: string; state: string; posted_transactions: string[] }> =>
+      postData(projectId ? `/pm/receipts?project_id=${projectId}` : "/pm/receipts", body),
+    receipts: async (projectId?: string | null): Promise<ConfirmedReceipt[]> =>
+      getData<ConfirmedReceipt[]>(projectId ? `/pm/receipts?project_id=${projectId}` : "/pm/receipts"),
   },
 
   // ساخت موجودیت‌های کاتالوگ سراسری از داخل پنل انبار (موجودی اولیه):
diff --git a/frontend/src/pages/Inventory/ArrivalsPage.tsx b/frontend/src/pages/Inventory/ArrivalsPage.tsx
index 162bb22..bddd4bb 100644
--- a/frontend/src/pages/Inventory/ArrivalsPage.tsx
+++ b/frontend/src/pages/Inventory/ArrivalsPage.tsx
@@ -33,9 +33,11 @@ export function ArrivalsPage() {
 
   const load = useCallback(async () => {
     try {
+      const activeProject = isPM ? user?.project_id || undefined : undefined;
       const [arr, whs] = await Promise.all([
-        apiV26.pm.onTheWay(),
-        apiV26.warehouses.list(isPM ? user?.project_id || undefined : undefined),
+        // پروژه‌ی فعال صریحاً ارسال می‌شود؛ بک‌اند تخصیص PM را بررسی می‌کند
+        apiV26.pm.onTheWay(activeProject),
+        apiV26.warehouses.list(activeProject),
       ]);
       setItems(arr);
       setWarehouses(whs);
@@ -186,7 +188,7 @@ export function ArrivalsPage() {
           item_decision_id: it.item_decision_id,
           received_qty: draftReceivedOf(it),
           allocations,
-        });
+        }, isPM ? user?.project_id || undefined : undefined);
       }
       toast.success("رسید (کامل یا جزیی) ثبت شد و به انبارها وارد شد ✓ — اقلام باقی‌مانده همچنان در راه هستند");
       // همگام‌سازی با دفتر تدارکات: store پیشنهادها را تازه کن تا کارت‌های
diff --git a/frontend/src/pages/Inventory/OrganizationPage.tsx b/frontend/src/pages/Inventory/OrganizationPage.tsx
index 8acbbb4..b1cfb90 100644
--- a/frontend/src/pages/Inventory/OrganizationPage.tsx
+++ b/frontend/src/pages/Inventory/OrganizationPage.tsx
@@ -8,6 +8,7 @@ import { apiV26, type UserRow } from "../../lib/api";
 import { refreshProcurementStore } from "../../hooks";
 import { useInventoryData } from "./useInventoryData";
 import { faNum } from "../../lib/formatters";
+import { ProjectMultiSelect } from "../../components/ProjectMultiSelect";
 
 type Role = "pm" | "procurement_manager" | "admin" | null;
 
@@ -96,17 +97,36 @@ export function OrganizationPage() {
     }
   };
 
-  const changeProject = async (u: UserRow, projectId: string) => {
+  // پروژه‌های متصل به یک کاربر (1:N) — با پشتیبانی از شکل قدیمیِ تک‌پروژه‌ای
+  const assignedProjectsOf = (u: UserRow) =>
+    u.projects ?? (u.project_id ? [{ id: u.project_id, name: u.project_name ?? "" }] : []);
+
+  // همگام‌سازی چند-انتخابیِ پروژه‌ها: افزودن/حذف هر اختلاف با یک PATCH
+  // (pm_user_id = کاربر برای اتصال، null برای جداسازی؛ مدیر قبلی جایگزین می‌شود)
+  const syncUserProjects = async (u: UserRow, nextIds: string[]) => {
+    const current = assignedProjectsOf(u).map((p) => p.id);
+    const added = nextIds.filter((id) => !current.includes(id));
+    const removed = current.filter((id) => !nextIds.includes(id));
+    if (!added.length && !removed.length) return;
     setBusyId(u.id);
     try {
-      const project = data.lookup.projects.find((p) => p.id === projectId);
-      await apiV26.users.assignProject(u.id, projectId || null);
-      toast.success(project ? `«${u.first_name} ${u.last_name}» به پروژه «${project.name}» متصل شد ✓` : "مدیر پروژه از پروژه جدا شد");
+      for (const pid of added) await apiV26.projects.setPm(pid, u.id);
+      for (const pid of removed) await apiV26.projects.setPm(pid, null);
+      const names = nextIds
+        .map((id) => data.lookup.projects.find((p) => p.id === id)?.name)
+        .filter(Boolean)
+        .join("، ");
+      toast.success(
+        nextIds.length
+          ? `پروژه‌های «${u.first_name} ${u.last_name}» به‌روزرسانی شد: ${names} ✓`
+          : `«${u.first_name} ${u.last_name}» از همه‌ی پروژه‌ها جدا شد`,
+      );
       await loadUsers();
       await data.refresh();
       refreshProcurementStore();
     } catch (err) {
-      toast.error(err instanceof Error ? err.message : "خطا در اتصال مدیر به پروژه");
+      toast.error(err instanceof Error ? err.message : "خطا در به‌روزرسانی پروژه‌ها");
+      await loadUsers(); // وضعیت واقعی سرور را برگردان
     } finally {
       setBusyId(null);
     }
@@ -149,7 +169,13 @@ export function OrganizationPage() {
     }
   };
 
-  const pmOf = (projectId: string) => users.find((u) => u.role === "pm" && u.project_id === projectId) || null;
+  // مدیرِ مسئول یک پروژه (1:N — کاربر ممکن است مدیر چند پروژه باشد)
+  const pmOf = (projectId: string) =>
+    users.find(
+      (u) =>
+        u.role === "pm" &&
+        (u.projects?.some((p) => p.id === projectId) || u.project_id === projectId),
+    ) || null;
 
   return (
     <div className="min-h-screen">
@@ -226,19 +252,14 @@ export function OrganizationPage() {
                           <small className="block text-[10px] text-muted">(تغییر نقش فقط توسط ادمین)</small>
                         )}
                       </td>
-                      <td className="py-1.5 pe-3">
+                      <td className="min-w-[240px] py-1.5 pe-3 align-top">
                         {u.role === "pm" ? (
-                          <select
-                            className="h-7 rounded-lg border border-line bg-panel px-2 text-[12px]"
-                            value={u.project_id || ""}
+                          <ProjectMultiSelect
+                            options={data.lookup.projects.map((p) => ({ id: p.id, name: p.name }))}
+                            values={assignedProjectsOf(u).map((p) => p.id)}
+                            onChange={(ids) => void syncUserProjects(u, ids)}
                             disabled={busyId === u.id}
-                            onChange={(e) => void changeProject(u, e.target.value)}
-                          >
-                            <option value="">— بدون پروژه —</option>
-                            {data.lookup.projects.map((p) => (
-                              <option key={p.id} value={p.id}>{p.name}</option>
-                            ))}
-                          </select>
+                          />
                         ) : (
                           <span className="text-[11.5px] text-muted">—</span>
                         )}
@@ -253,7 +274,9 @@ export function OrganizationPage() {
                 </tbody>
               </table>
               <div className="mt-1 text-[11px] text-muted">
-                «بدون نقش» = حذف مدیر پروژه (از پروژه هم جدا می‌شود). اتصال به یک پروژه، مدیر قبلی آن پروژه را جابه‌جا می‌کند.
+                «بدون نقش» = حذف مدیر پروژه (از همه‌ی پروژه‌ها هم جدا می‌شود). هر مدیر پروژه می‌تواند به
+                چند پروژه متصل باشد؛ حذف هر چیپ (×)، فقط همان پروژه را جدا می‌کند و اتصال به یک پروژه، مدیرِ
+                قبلیِ آن پروژه را جابه‌جا می‌کند.
               </div>
             </div>
           )}
diff --git a/frontend/src/pages/Inventory/useInventoryData.ts b/frontend/src/pages/Inventory/useInventoryData.ts
index 9f7c727..2b2b55a 100644
--- a/frontend/src/pages/Inventory/useInventoryData.ts
+++ b/frontend/src/pages/Inventory/useInventoryData.ts
@@ -54,6 +54,9 @@ export function useInventoryData(): InventoryData {
       setWarehouses(whs);
       setInventory(inv);
       setTransactions(txs);
+    } catch {
+      // پروژه‌ی فعال ممکن است همین حالا باطل شده باشد — گیتِ پروژه در سطح مسیر
+      // (RequirePmProjects) پروژه‌ی جایگزین/صفحه‌ی خالی را نشان می‌دهد.
     } finally {
       setLoading(false);
     }
diff --git a/frontend/src/store/auth.ts b/frontend/src/store/auth.ts
index 8a9d7c9..c5bc783 100644
--- a/frontend/src/store/auth.ts
+++ b/frontend/src/store/auth.ts
@@ -16,8 +16,9 @@ export interface AuthUser {
   phone: string | null;
   role: "pm" | "procurement_manager" | "admin" | null;
   role_label: string | null;
-  project_id: string | null;
+  project_id: string | null; // پروژه‌ی فعال (PM) — با سوییچر عوض می‌شود
   project_name: string | null;
+  projects?: { id: string; name: string }[]; // همه‌ی پروژه‌های تخصیص‌یافته (1:N)
   display_name: string;
 }
 
@@ -28,6 +29,11 @@ interface AuthStore {
   setToken: (token: string | null) => void;
   setUser: (user: AuthUser | null) => void;
   setDevUser: (role: "pm" | "admin" | "procurement_manager", projectId: string | null, projectName: string | null) => void;
+  // پروژه‌های تخصیص‌یافته را می‌نشاند و پروژه‌ی فعال را اعتبارسنجی می‌کند:
+  // اگر پروژه‌ی ذخیره‌شده (localStorage) باطل شده باشد، به اولین پروژه برمی‌گردد.
+  setProjects: (projects: { id: string; name: string }[]) => void;
+  // جابه‌جایی پروژه‌ی فعال بدون هیچ تغییری در نشست/توکن (بدون احراز هویت مجدد)
+  setActiveProject: (projectId: string) => void;
   logout: () => void;
 }
 
@@ -53,9 +59,30 @@ export const useAuthStore = create<AuthStore>()(
             role_label: role === "pm" ? "مدیر پروژه (آزمایشی)" : role === "procurement_manager" ? "مدیر تدارکات (آزمایشی)" : "ادمین (آزمایشی)",
             project_id: projectId,
             project_name: projectName,
+            projects: projectId ? [{ id: projectId, name: projectName || "" }] : [],
             display_name: projectId ? `کاربر آزمایشی — ${projectName || ""}` : "کاربر آزمایشی",
           },
         }),
+      setProjects: (projects) =>
+        set((s) => {
+          if (!s.user) return {};
+          const active = projects.find((p) => p.id === s.user!.project_id) ?? projects[0] ?? null;
+          return {
+            user: {
+              ...s.user,
+              projects,
+              project_id: active?.id ?? null,
+              project_name: active?.name ?? null,
+            },
+          };
+        }),
+      setActiveProject: (projectId) =>
+        set((s) => {
+          if (!s.user) return {};
+          const target = (s.user.projects ?? []).find((p) => p.id === projectId);
+          if (!target) return {};
+          return { user: { ...s.user, project_id: target.id, project_name: target.name } };
+        }),
       logout: () => set({ token: null, user: null, isDev: false }),
     }),
     { name: "procurement-auth-v1" },