diff --git a/apps/backend/hub_platform/ai/api_errors.py b/apps/backend/hub_platform/ai/api_errors.py
new file mode 100644
index 0000000..a36e089
--- /dev/null
+++ b/apps/backend/hub_platform/ai/api_errors.py
@@ -0,0 +1,14 @@
+from django.core.exceptions import ValidationError
+from rest_framework.response import Response
+
+
+def validation_error_response(error: ValidationError) -> Response:
+    if hasattr(error, "message_dict"):
+        detail = "; ".join(
+            message
+            for messages in error.message_dict.values()
+            for message in messages
+        )
+    else:
+        detail = "; ".join(error.messages)
+    return Response({"detail": detail}, status=400)
diff --git a/apps/backend/hub_platform/ai/category_views.py b/apps/backend/hub_platform/ai/category_views.py
new file mode 100644
index 0000000..eca54ca
--- /dev/null
+++ b/apps/backend/hub_platform/ai/category_views.py
@@ -0,0 +1,148 @@
+from django.core.exceptions import ValidationError
+from rest_framework.request import Request
+from rest_framework.response import Response
+from rest_framework.views import APIView
+
+from hub_platform.ai.api_errors import validation_error_response
+from hub_platform.ai.knowledge_categories import (
+    create_category,
+    delete_category,
+    update_category,
+)
+from hub_platform.ai.knowledge_policy import require_category_manage
+from hub_platform.ai.models import KnowledgeCategory
+from hub_platform.ai.selectors import category_tree_for_employee
+from hub_platform.ai.serializers import category_payload
+from hub_platform.api.permissions import HasCapability, HasEntitlement
+from hub_platform.identity.audit import record_audit_event
+
+
+def _integer(value: object, field: str) -> int:
+    if isinstance(value, bool):
+        raise ValidationError({field: "Integer required"})
+    try:
+        return int(value)
+    except (TypeError, ValueError) as error:
+        raise ValidationError({field: "Integer required"}) from error
+
+
+def _category(request: Request, category_id: int) -> KnowledgeCategory:
+    return KnowledgeCategory.objects.select_related("parent").get(
+        organization_id=request.tenant_context.organization_id,
+        id=category_id,
+    )
+
+
+def _parent(
+    request: Request, value: object, *, field_present: bool
+) -> KnowledgeCategory | None:
+    if not field_present or value is None:
+        return None
+    parent_id = _integer(value, "parentId")
+    try:
+        return _category(request, parent_id)
+    except KnowledgeCategory.DoesNotExist as error:
+        raise ValidationError({"parentId": "Parent category not found"}) from error
+
+
+def _audit(
+    request: Request,
+    action: str,
+    category: KnowledgeCategory,
+    *,
+    object_id: int | None = None,
+) -> None:
+    record_audit_event(
+        action=f"ai.knowledge_category_{action}",
+        actor=request.user,
+        organization=request.tenant_context.organization,
+        object_type="KnowledgeCategory",
+        object_id=str(object_id if object_id is not None else category.id),
+        request=request,
+    )
+
+
+def _category_payload(request: Request, category_id: int) -> dict[str, object]:
+    category = next(
+        item
+        for item in category_tree_for_employee(context=request.tenant_context)
+        if item.id == category_id
+    )
+    return category_payload(category)
+
+
+class KnowledgeCategoryListCreateView(APIView):
+    permission_classes = [HasEntitlement, HasCapability]
+    required_entitlement = "knowledge_base"
+    required_capabilities = {"GET": "ai.view", "POST": "ai.manage"}
+
+    def get(self, request: Request) -> Response:
+        categories = category_tree_for_employee(context=request.tenant_context)
+        return Response({"items": [category_payload(item) for item in categories]})
+
+    def post(self, request: Request) -> Response:
+        try:
+            require_category_manage(context=request.tenant_context)
+            parent = _parent(
+                request,
+                request.data.get("parentId"),
+                field_present="parentId" in request.data,
+            )
+            category = create_category(
+                context=request.tenant_context,
+                name=str(request.data.get("name", "")),
+                parent=parent,
+                sort_order=_integer(request.data.get("sortOrder", 0), "sortOrder"),
+            )
+        except ValidationError as error:
+            return validation_error_response(error)
+        _audit(request, "created", category)
+        return Response(
+            {"category": _category_payload(request, category.id)}, status=201
+        )
+
+
+class KnowledgeCategoryDetailView(APIView):
+    permission_classes = [HasEntitlement, HasCapability]
+    required_entitlement = "knowledge_base"
+    required_capability = "ai.manage"
+
+    def patch(self, request: Request, category_id: int) -> Response:
+        try:
+            require_category_manage(context=request.tenant_context)
+            category = _category(request, category_id)
+        except KnowledgeCategory.DoesNotExist:
+            return Response({"detail": "Category not found"}, status=404)
+        try:
+            parent = (
+                _parent(request, request.data.get("parentId"), field_present=True)
+                if "parentId" in request.data
+                else category.parent
+            )
+            updated = update_category(
+                context=request.tenant_context,
+                category=category,
+                name=str(request.data.get("name", category.name)),
+                parent=parent,
+                sort_order=_integer(
+                    request.data.get("sortOrder", category.sort_order), "sortOrder"
+                ),
+            )
+        except ValidationError as error:
+            return validation_error_response(error)
+        _audit(request, "updated", updated)
+        return Response({"category": _category_payload(request, updated.id)})
+
+    def delete(self, request: Request, category_id: int) -> Response:
+        try:
+            require_category_manage(context=request.tenant_context)
+            category = _category(request, category_id)
+        except KnowledgeCategory.DoesNotExist:
+            return Response({"detail": "Category not found"}, status=404)
+        try:
+            deleted_id = category.id
+            delete_category(context=request.tenant_context, category=category)
+        except ValidationError as error:
+            return validation_error_response(error)
+        _audit(request, "deleted", category, object_id=deleted_id)
+        return Response(status=204)
diff --git a/apps/backend/hub_platform/ai/knowledge_api_inputs.py b/apps/backend/hub_platform/ai/knowledge_api_inputs.py
new file mode 100644
index 0000000..8b4e19f
--- /dev/null
+++ b/apps/backend/hub_platform/ai/knowledge_api_inputs.py
@@ -0,0 +1,116 @@
+from django.core.exceptions import ValidationError
+from rest_framework.request import Request
+
+from hub_platform.ai.knowledge_types import KnowledgeVisibility
+from hub_platform.ai.knowledge_services import KnowledgeInput
+from hub_platform.ai.models import Knowledge
+from hub_platform.ai.selectors import KnowledgeFilters
+
+
+def _positive_id(value: object, field: str) -> int:
+    if isinstance(value, bool):
+        raise ValidationError({field: "Positive integer id required"})
+    try:
+        parsed = int(value)
+    except (TypeError, ValueError) as error:
+        raise ValidationError({field: "Integer id required"}) from error
+    if parsed <= 0:
+        raise ValidationError({field: "Positive integer id required"})
+    return parsed
+
+
+def _optional_query_id(value: str | None, field: str) -> int | None:
+    return None if value in (None, "") else _positive_id(value, field)
+
+
+def _category_id(body: dict[str, object], current: Knowledge | None) -> int | None:
+    if "categoryId" in body:
+        return _positive_id(body["categoryId"], "category")
+    if "category" not in body:
+        return current.category_id if current else None
+    raw = body["category"]
+    if isinstance(raw, dict):
+        raw = raw.get("id")
+    return _positive_id(raw, "category")
+
+
+def _department_ids(body: dict[str, object], current: Knowledge | None) -> tuple[int, ...]:
+    if "departmentIds" in body:
+        raw_items = body["departmentIds"]
+    elif "departments" in body:
+        raw_items = body["departments"]
+    elif current is not None:
+        return tuple(
+            current.department_links.values_list("department_id", flat=True)
+        )
+    else:
+        return ()
+    if not isinstance(raw_items, list):
+        raise ValidationError({"departments": "List of department ids required"})
+    normalized: list[int] = []
+    for item in raw_items:
+        raw_id = item.get("id") if isinstance(item, dict) else item
+        department_id = _positive_id(raw_id, "departments")
+        if department_id not in normalized:
+            normalized.append(department_id)
+    return tuple(normalized)
+
+
+def knowledge_input(
+    body: dict[str, object], *, current: Knowledge | None = None
+) -> KnowledgeInput:
+    raw_enabled = body.get("isEnabled", current.is_enabled if current else True)
+    if not isinstance(raw_enabled, bool):
+        raise ValidationError({"isEnabled": "Boolean required"})
+    visibility = str(
+        body.get(
+            "visibility",
+            current.visibility if current else KnowledgeVisibility.ORGANIZATION,
+        )
+    )
+    if visibility not in KnowledgeVisibility.values:
+        raise ValidationError({"visibility": "Unknown knowledge visibility"})
+    department_ids = _department_ids(body, current)
+    if (
+        visibility == KnowledgeVisibility.ORGANIZATION
+        and "departmentIds" not in body
+        and "departments" not in body
+    ):
+        department_ids = ()
+    return KnowledgeInput(
+        title=str(body.get("title", current.title if current else "")),
+        description=str(
+            body.get("description", current.description if current else "")
+        ),
+        content=str(body.get("content", current.content if current else "")),
+        is_enabled=raw_enabled,
+        category_id=_category_id(body, current),
+        visibility=visibility,
+        department_ids=department_ids,
+    )
+
+
+def knowledge_filters(request: Request) -> KnowledgeFilters:
+    visibility = request.query_params.get("visibility") or None
+    if visibility is not None and visibility not in KnowledgeVisibility.values:
+        raise ValidationError({"visibility": "Unknown knowledge visibility"})
+    raw_enabled = request.query_params.get("isEnabled")
+    if raw_enabled in (None, ""):
+        is_enabled = None
+    elif raw_enabled.lower() == "true":
+        is_enabled = True
+    elif raw_enabled.lower() == "false":
+        is_enabled = False
+    else:
+        raise ValidationError({"isEnabled": "Boolean required"})
+    return KnowledgeFilters(
+        category_id=_optional_query_id(
+            request.query_params.get("category"), "category"
+        ),
+        department_id=_optional_query_id(
+            request.query_params.get("department"), "department"
+        ),
+        visibility=visibility,
+        is_enabled=is_enabled,
+        search=request.query_params.get("search", ""),
+    )
diff --git a/apps/backend/hub_platform/ai/knowledge_categories.py b/apps/backend/hub_platform/ai/knowledge_categories.py
index a736fae..30f7dec 100644
--- a/apps/backend/hub_platform/ai/knowledge_categories.py
+++ b/apps/backend/hub_platform/ai/knowledge_categories.py
@@ -92,6 +92,33 @@ def move_category(
     return locked
 
 
+@transaction.atomic
+def update_category(
+    *,
+    context: TenantContext,
+    category: KnowledgeCategory,
+    name: str,
+    parent: KnowledgeCategory | None,
+    sort_order: int,
+) -> KnowledgeCategory:
+    _validate_category_context(context=context, category=category)
+    _validate_parent(context=context, parent=parent)
+    if category.is_system:
+        raise ValidationError({"category": "System category is immutable"})
+    locked_categories = {
+        item.pk: item
+        for item in KnowledgeCategory.objects.select_for_update().filter(
+            organization_id=context.organization_id
+        )
+    }
+    locked = locked_categories[category.pk]
+    locked.name = name
+    locked.parent = locked_categories[parent.pk] if parent is not None else None
+    locked.sort_order = sort_order
+    locked.save(update_fields=["name", "parent", "sort_order"])
+    return locked
+
+
 @transaction.atomic
 def delete_category(*, context: TenantContext, category: KnowledgeCategory) -> None:
     _validate_category_context(context=context, category=category)
diff --git a/apps/backend/hub_platform/ai/knowledge_policy.py b/apps/backend/hub_platform/ai/knowledge_policy.py
index 689cd45..695adad 100644
--- a/apps/backend/hub_platform/ai/knowledge_policy.py
+++ b/apps/backend/hub_platform/ai/knowledge_policy.py
@@ -143,6 +143,11 @@ def require_knowledge_create(
         raise PermissionDenied("Knowledge scope is not manageable")
 
 
+def require_category_manage(*, context: TenantContext) -> None:
+    if not employee_can_manage_categories(context=context):
+        raise PermissionDenied("Organization-scoped ai.manage is required")
+
+
 def knowledge_is_available_to_agent(
     *, knowledge: Knowledge, agent: AIAgent
 ) -> bool:
diff --git a/apps/backend/hub_platform/ai/knowledge_services.py b/apps/backend/hub_platform/ai/knowledge_services.py
new file mode 100644
index 0000000..36a4482
--- /dev/null
+++ b/apps/backend/hub_platform/ai/knowledge_services.py
@@ -0,0 +1,195 @@
+from dataclasses import dataclass
+
+from django.core.exceptions import ValidationError
+from django.core.files.uploadedfile import UploadedFile
+from django.db import transaction
+
+from hub_platform.ai.extraction import extract_text
+from hub_platform.ai.indexing import reindex_knowledge
+from hub_platform.ai.knowledge_categories import ensure_uncategorized_category
+from hub_platform.ai.knowledge_types import KnowledgeVisibility
+from hub_platform.ai.knowledge_visibility import replace_knowledge_visibility
+from hub_platform.ai.models import (
+    Knowledge,
+    KnowledgeAttachment,
+    KnowledgeCategory,
+)
+from hub_platform.tenancy.context import TenantContext
+from hub_platform.tenancy.storage import adjust_storage_usage
+from hub_platform.tenancy.storage_quota import (
+    finalize_storage,
+    release_storage,
+    reserve_storage,
+)
+
+
+@dataclass(frozen=True)
+class KnowledgeInput:
+    title: str
+    description: str
+    content: str
+    is_enabled: bool
+    category_id: int | None = None
+    visibility: str | None = None
+    department_ids: tuple[int, ...] | None = None
+
+
+def _knowledge_category(
+    *, context: TenantContext, category_id: int | None
+) -> KnowledgeCategory:
+    if category_id is None:
+        return ensure_uncategorized_category(context.organization)
+    try:
+        return KnowledgeCategory.objects.get(
+            organization_id=context.organization_id,
+            id=category_id,
+        )
+    except KnowledgeCategory.DoesNotExist as error:
+        raise ValidationError({"category": "Category not found"}) from error
+
+
+@transaction.atomic
+def create_knowledge(*, context: TenantContext, data: KnowledgeInput) -> Knowledge:
+    if not data.title.strip():
+        raise ValidationError({"title": "Title is required"})
+    visibility = data.visibility or KnowledgeVisibility.ORGANIZATION
+    department_ids = data.department_ids or ()
+    knowledge = Knowledge.objects.create(
+        organization=context.organization,
+        category=_knowledge_category(context=context, category_id=data.category_id),
+        title=data.title.strip(),
+        description=data.description.strip(),
+        content=data.content,
+        is_enabled=data.is_enabled,
+        visibility=visibility,
+    )
+    knowledge = replace_knowledge_visibility(
+        context=context,
+        knowledge=knowledge,
+        visibility=visibility,
+        department_ids=department_ids,
+    )
+    reindex_knowledge(knowledge)
+    return knowledge
+
+
+@transaction.atomic
+def update_knowledge(
+    *, context: TenantContext, knowledge: Knowledge, data: KnowledgeInput
+) -> Knowledge:
+    if knowledge.organization_id != context.organization_id:
+        raise ValidationError({"knowledge": "Knowledge belongs to another organization"})
+    if not data.title.strip():
+        raise ValidationError({"title": "Title is required"})
+    locked = Knowledge.objects.select_for_update().get(pk=knowledge.pk)
+    content_changed = locked.content != data.content
+    locked.title = data.title.strip()
+    locked.description = data.description.strip()
+    locked.content = data.content
+    locked.is_enabled = data.is_enabled
+    if data.category_id is not None:
+        locked.category = _knowledge_category(
+            context=context,
+            category_id=data.category_id,
+        )
+    locked.save(
+        update_fields=[
+            "title",
+            "description",
+            "content",
+            "is_enabled",
+            "category",
+            "updated_at",
+        ]
+    )
+    if data.visibility is not None or data.department_ids is not None:
+        locked = replace_knowledge_visibility(
+            context=context,
+            knowledge=locked,
+            visibility=data.visibility or locked.visibility,
+            department_ids=(
+                data.department_ids
+                if data.department_ids is not None
+                else tuple(
+                    locked.department_links.values_list("department_id", flat=True)
+                )
+            ),
+        )
+    if content_changed:
+        reindex_knowledge(locked)
+    return locked
+
+
+def delete_knowledge(*, context: TenantContext, knowledge: Knowledge) -> None:
+    if knowledge.organization_id != context.organization_id:
+        raise ValidationError({"knowledge": "Knowledge belongs to another organization"})
+    attachments = list(knowledge.attachments.all())
+    released_bytes = sum(attachment.size for attachment in attachments)
+    for attachment in attachments:
+        attachment.file.delete(save=False)
+    knowledge.delete()
+    if released_bytes:
+        adjust_storage_usage(context=context, delta_bytes=-released_bytes)
+
+
+_MAX_ATTACHMENT_BYTES = 25 * 1024 * 1024
+
+
+@transaction.atomic
+def add_attachment(
+    *, context: TenantContext, knowledge: Knowledge, upload: UploadedFile
+) -> KnowledgeAttachment:
+    if knowledge.organization_id != context.organization_id:
+        raise ValidationError({"knowledge": "Knowledge belongs to another organization"})
+    original_name = (upload.name or "").strip()
+    if not original_name:
+        raise ValidationError({"file": "File name is required"})
+    if upload.size and upload.size > _MAX_ATTACHMENT_BYTES:
+        raise ValidationError({"file": "File is too large (max 25 MB)"})
+    existing = knowledge.attachments.filter(original_name=original_name).first()
+    existing_size = existing.size if existing is not None else 0
+    data = upload.read()
+    reservation_key = f"attachment:{knowledge.id}:{original_name}"
+    reserve_storage(
+        context=context, expected_bytes=len(data), idempotency_key=reservation_key
+    )
+    try:
+        if existing is not None:
+            existing.file.delete(save=False)
+            existing.delete()
+            if existing_size:
+                adjust_storage_usage(context=context, delta_bytes=-existing_size)
+        content_type = upload.content_type or ""
+        attachment = KnowledgeAttachment(
+            organization=context.organization,
+            knowledge=knowledge,
+            original_name=original_name,
+            content_type=content_type,
+            size=len(data),
+            extracted_text=extract_text(
+                filename=original_name, content_type=content_type, data=data
+            ),
+        )
+        from django.core.files.base import ContentFile
+
+        attachment.file.save(original_name, ContentFile(data), save=True)
+    except Exception:
+        release_storage(context=context, idempotency_key=reservation_key)
+        raise
+    finalize_storage(
+        context=context, idempotency_key=reservation_key, actual_bytes=len(data)
+    )
+    reindex_knowledge(knowledge)
+    return attachment
+
+
+def delete_attachment(*, context: TenantContext, attachment: KnowledgeAttachment) -> None:
+    if attachment.knowledge.organization_id != context.organization_id:
+        raise ValidationError({"attachment": "Attachment belongs to another organization"})
+    knowledge = attachment.knowledge
+    released_bytes = attachment.size
+    attachment.file.delete(save=False)
+    attachment.delete()
+    if released_bytes:
+        adjust_storage_usage(context=context, delta_bytes=-released_bytes)
+    reindex_knowledge(knowledge)
diff --git a/apps/backend/hub_platform/ai/selectors.py b/apps/backend/hub_platform/ai/selectors.py
index ec2cd63..9d5a710 100644
--- a/apps/backend/hub_platform/ai/selectors.py
+++ b/apps/backend/hub_platform/ai/selectors.py
@@ -1,11 +1,12 @@
 from dataclasses import dataclass
 
-from django.db.models import Count, Q, QuerySet
+from django.db.models import Count, Prefetch, Q, QuerySet
 
 from hub_platform.ai.knowledge_policy import readable_knowledge, writable_knowledge
 from hub_platform.ai.knowledge_types import KnowledgeVisibility
 from hub_platform.ai.models import AIAgent, Knowledge, KnowledgeCategory
 from hub_platform.channels.models import Channel
+from hub_platform.identity.models import Department
 from hub_platform.identity.policy import accessible_department_ids
 from hub_platform.tenancy.context import TenantContext
 
@@ -67,7 +68,13 @@ def _knowledge_base(context: TenantContext) -> QuerySet[Knowledge]:
 def _with_knowledge_relations(queryset: QuerySet[Knowledge]) -> QuerySet[Knowledge]:
     return (
         queryset.select_related("category")
-        .prefetch_related("attachments", "departments")
+        .prefetch_related(
+            "attachments",
+            Prefetch(
+                "departments",
+                queryset=Department.objects.order_by("name", "id"),
+            ),
+        )
         .annotate(agents_count=Count("agents", distinct=True))
         .order_by("title")
     )
diff --git a/apps/backend/hub_platform/ai/serializers.py b/apps/backend/hub_platform/ai/serializers.py
index f0a17ad..209c330 100644
--- a/apps/backend/hub_platform/ai/serializers.py
+++ b/apps/backend/hub_platform/ai/serializers.py
@@ -1,4 +1,10 @@
-from hub_platform.ai.models import AIAgent, Knowledge, KnowledgeAttachment
+from hub_platform.ai.models import (
+    AIAgent,
+    Knowledge,
+    KnowledgeAttachment,
+    KnowledgeCategory,
+)
+from hub_platform.identity.models import Department
 
 
 def _channel_ref(channel) -> dict[str, object]:
@@ -23,11 +29,42 @@ def attachment_payload(attachment: KnowledgeAttachment) -> dict[str, object]:
     }
 
 
+def category_ref_payload(category: KnowledgeCategory) -> dict[str, object]:
+    return {
+        "id": category.id,
+        "name": category.name,
+        "parentId": category.parent_id,
+    }
+
+
+def category_payload(category: KnowledgeCategory) -> dict[str, object]:
+    return {
+        **category_ref_payload(category),
+        "sortOrder": category.sort_order,
+        "isSystem": category.is_system,
+        "knowledgeCount": getattr(category, "knowledge_count", None),
+    }
+
+
+def department_ref_payload(department: Department) -> dict[str, object]:
+    return {
+        "id": department.id,
+        "code": department.code,
+        "name": department.name,
+    }
+
+
 def knowledge_payload(knowledge: Knowledge, *, include_content: bool = True) -> dict[str, object]:
     payload: dict[str, object] = {
         "id": knowledge.id,
         "title": knowledge.title,
         "description": knowledge.description,
+        "category": category_ref_payload(knowledge.category),
+        "visibility": knowledge.visibility,
+        "departments": [
+            department_ref_payload(department)
+            for department in knowledge.departments.all()
+        ],
         "isEnabled": knowledge.is_enabled,
         "attachments": [attachment_payload(attachment) for attachment in knowledge.attachments.all()],
         "agentsCount": getattr(knowledge, "agents_count", None),
diff --git a/apps/backend/hub_platform/ai/services.py b/apps/backend/hub_platform/ai/services.py
index 131cd44..38b4fde 100644
--- a/apps/backend/hub_platform/ai/services.py
+++ b/apps/backend/hub_platform/ai/services.py
@@ -1,27 +1,16 @@
 from dataclasses import dataclass
 
 from django.core.exceptions import ValidationError
-from django.core.files.uploadedfile import UploadedFile
 from django.db import transaction
 
-from hub_platform.ai.extraction import extract_text
-from hub_platform.ai.indexing import reindex_knowledge
-from hub_platform.ai.knowledge_categories import ensure_uncategorized_category
 from hub_platform.ai.models import (
     AIAgent,
     AIAgentStatus,
     Knowledge,
-    KnowledgeAttachment,
 )
 from hub_platform.ai.provider_selection import configure_agent_provider
 from hub_platform.channels.models import Channel
 from hub_platform.tenancy.context import TenantContext
-from hub_platform.tenancy.storage import adjust_storage_usage
-from hub_platform.tenancy.storage_quota import (
-    finalize_storage,
-    release_storage,
-    reserve_storage,
-)
 
 
 @dataclass(frozen=True)
@@ -153,126 +142,11 @@ def set_agent_active(*, context: TenantContext, agent: AIAgent, is_active: bool)
     )
 
 
-# --- Знания (ADR-HUB-0023) ---
-
-
-@dataclass(frozen=True)
-class KnowledgeInput:
-    title: str
-    description: str
-    content: str
-    is_enabled: bool
-
-
-def create_knowledge(*, context: TenantContext, data: KnowledgeInput) -> Knowledge:
-    if not data.title.strip():
-        raise ValidationError({"title": "Title is required"})
-    knowledge = Knowledge.objects.create(
-        organization=context.organization,
-        category=ensure_uncategorized_category(context.organization),
-        title=data.title.strip(),
-        description=data.description.strip(),
-        content=data.content,
-        is_enabled=data.is_enabled,
-    )
-    reindex_knowledge(knowledge)
-    return knowledge
-
-
-def update_knowledge(*, context: TenantContext, knowledge: Knowledge, data: KnowledgeInput) -> Knowledge:
-    if knowledge.organization_id != context.organization_id:
-        raise ValidationError({"knowledge": "Knowledge belongs to another organization"})
-    if not data.title.strip():
-        raise ValidationError({"title": "Title is required"})
-    content_changed = knowledge.content != data.content
-    knowledge.title = data.title.strip()
-    knowledge.description = data.description.strip()
-    knowledge.content = data.content
-    knowledge.is_enabled = data.is_enabled
-    knowledge.save(update_fields=["title", "description", "content", "is_enabled", "updated_at"])
-    if content_changed:
-        reindex_knowledge(knowledge)
-    return knowledge
-
-
-def delete_knowledge(*, context: TenantContext, knowledge: Knowledge) -> None:
-    if knowledge.organization_id != context.organization_id:
-        raise ValidationError({"knowledge": "Knowledge belongs to another organization"})
-    # Файлы вложений удаляются вместе со знанием: сначала с диска, потом запись.
-    attachments = list(knowledge.attachments.all())
-    released_bytes = sum(attachment.size for attachment in attachments)
-    for attachment in attachments:
-        attachment.file.delete(save=False)
-    knowledge.delete()
-    if released_bytes:
-        adjust_storage_usage(context=context, delta_bytes=-released_bytes)
-
-
-_MAX_ATTACHMENT_BYTES = 25 * 1024 * 1024
-
-
-@transaction.atomic
-def add_attachment(
-    *, context: TenantContext, knowledge: Knowledge, upload: UploadedFile
-) -> KnowledgeAttachment:
-    if knowledge.organization_id != context.organization_id:
-        raise ValidationError({"knowledge": "Knowledge belongs to another organization"})
-    original_name = (upload.name or "").strip()
-    if not original_name:
-        raise ValidationError({"file": "File name is required"})
-    if upload.size and upload.size > _MAX_ATTACHMENT_BYTES:
-        raise ValidationError({"file": "File is too large (max 25 MB)"})
-    # Повторная загрузка с тем же именем заменяет файл (ADR-HUB-0023: без версий).
-    existing = knowledge.attachments.filter(original_name=original_name).first()
-    existing_size = existing.size if existing is not None else 0
-    data = upload.read()
-    # C07 storage gate (SPEC §10): reserve the expected size before the write so a
-    # concurrent upload cannot exceed storage_bytes; finalize with the actual size
-    # after the object is persisted, or release on failure. Reads are never gated.
-    # Deterministic key makes a retried upload of the same file idempotent; a prior
-    # finalized/released reservation is ignored by the active-reservation filter.
-    reservation_key = f"attachment:{knowledge.id}:{original_name}"
-    reserve_storage(
-        context=context, expected_bytes=len(data), idempotency_key=reservation_key
-    )
-    try:
-        if existing is not None:
-            existing.file.delete(save=False)
-            existing.delete()
-            if existing_size:
-                adjust_storage_usage(context=context, delta_bytes=-existing_size)
-        content_type = upload.content_type or ""
-        attachment = KnowledgeAttachment(
-            organization=context.organization,
-            knowledge=knowledge,
-            original_name=original_name,
-            content_type=content_type,
-            size=len(data),
-            extracted_text=extract_text(
-                filename=original_name, content_type=content_type, data=data
-            ),
-        )
-        from django.core.files.base import ContentFile
-
-        attachment.file.save(original_name, ContentFile(data), save=True)
-    except Exception:
-        # Upload failed after reservation: release the reserved bytes (SPEC §10.4).
-        release_storage(context=context, idempotency_key=reservation_key)
-        raise
-    finalize_storage(
-        context=context, idempotency_key=reservation_key, actual_bytes=len(data)
-    )
-    reindex_knowledge(knowledge)
-    return attachment
-
-
-def delete_attachment(*, context: TenantContext, attachment: KnowledgeAttachment) -> None:
-    if attachment.knowledge.organization_id != context.organization_id:
-        raise ValidationError({"attachment": "Attachment belongs to another organization"})
-    knowledge = attachment.knowledge
-    released_bytes = attachment.size
-    attachment.file.delete(save=False)
-    attachment.delete()
-    if released_bytes:
-        adjust_storage_usage(context=context, delta_bytes=-released_bytes)
-    reindex_knowledge(knowledge)
+from hub_platform.ai.knowledge_services import (  # noqa: E402, F401
+    KnowledgeInput,
+    add_attachment,
+    create_knowledge,
+    delete_attachment,
+    delete_knowledge,
+    update_knowledge,
+)
diff --git a/apps/backend/hub_platform/ai/test_knowledge_api_v2.py b/apps/backend/hub_platform/ai/test_knowledge_api_v2.py
new file mode 100644
index 0000000..4dfe887
--- /dev/null
+++ b/apps/backend/hub_platform/ai/test_knowledge_api_v2.py
@@ -0,0 +1,170 @@
+import json
+
+from hub_platform.ai.knowledge_categories import create_category
+from hub_platform.ai.knowledge_policy_test_base import KnowledgePolicyTestBase
+from hub_platform.ai.knowledge_types import KnowledgeVisibility
+from hub_platform.ai.models import Knowledge
+from hub_platform.identity.models import Department, DepartmentStatus
+from hub_platform.subscriptions.testing import create_test_subscription
+from hub_platform.testing import TenantAPIClient
+
+
+class HierarchicalKnowledgeApiTests(KnowledgePolicyTestBase):
+    def setUp(self) -> None:
+        super().setUp()
+        create_test_subscription(self.organization)
+        self.client = TenantAPIClient()
+        self.client.force_authenticate(self.organization_manager.user)
+        self.guides = create_category(
+            context=self.system_context,
+            parent=self.products,
+            name="Guides",
+        )
+        self.disabled_department = Department.objects.create(
+            organization=self.organization,
+            code="disabled-api",
+            name="Disabled",
+            status=DepartmentStatus.DISABLED,
+        )
+
+    def _post(self, payload: dict[str, object]):
+        return self.client.post(
+            "/api/v1/ai/knowledge/",
+            data=json.dumps(payload),
+            content_type="application/json",
+        )
+
+    def test_create_and_detail_return_complete_scope_payload(self) -> None:
+        response = self._post(
+            {
+                "title": "Scoped guide",
+                "description": "For two teams",
+                "content": "Guide content",
+                "categoryId": self.guides.id,
+                "visibility": KnowledgeVisibility.DEPARTMENTS,
+                "departmentIds": [self.support.id, self.sales.id],
+            }
+        )
+
+        self.assertEqual(response.status_code, 201)
+        payload = response.json()["knowledge"]
+        self.assertEqual(
+            payload["category"],
+            {"id": self.guides.id, "name": "Guides", "parentId": self.products.id},
+        )
+        self.assertEqual(payload["visibility"], KnowledgeVisibility.DEPARTMENTS)
+        self.assertEqual(
+            [department["id"] for department in payload["departments"]],
+            [self.sales.id, self.support.id],
+        )
+        detail = self.client.get(f"/api/v1/ai/knowledge/{payload['id']}/")
+        self.assertEqual(detail.json()["knowledge"]["content"], "Guide content")
+
+    def test_update_scope_category_and_metadata_is_atomic(self) -> None:
+        knowledge = self.sales_only
+        response = self.client.patch(
+            f"/api/v1/ai/knowledge/{knowledge.id}/",
+            data=json.dumps(
+                {
+                    "title": "Moved playbook",
+                    "category": {"id": self.guides.id},
+                    "visibility": KnowledgeVisibility.DEPARTMENTS,
+                    "departments": [{"id": self.sales.id}, {"id": self.support.id}],
+                }
+            ),
+            content_type="application/json",
+        )
+        self.assertEqual(response.status_code, 200)
+        payload = response.json()["knowledge"]
+        self.assertEqual(payload["category"]["id"], self.guides.id)
+        self.assertEqual(
+            {item["id"] for item in payload["departments"]},
+            {self.sales.id, self.support.id},
+        )
+
+        invalid = self.client.patch(
+            f"/api/v1/ai/knowledge/{knowledge.id}/",
+            data=json.dumps(
+                {
+                    "title": "Must roll back",
+                    "departmentIds": [self.disabled_department.id],
+                }
+            ),
+            content_type="application/json",
+        )
+        self.assertEqual(invalid.status_code, 400)
+        knowledge.refresh_from_db()
+        self.assertEqual(knowledge.title, "Moved playbook")
+        self.assertEqual(
+            set(knowledge.departments.values_list("id", flat=True)),
+            {self.sales.id, self.support.id},
+        )
+
+        organization_scope = self.client.patch(
+            f"/api/v1/ai/knowledge/{knowledge.id}/",
+            data=json.dumps({"visibility": KnowledgeVisibility.ORGANIZATION}),
+            content_type="application/json",
+        )
+        self.assertEqual(organization_scope.status_code, 200)
+        self.assertEqual(
+            organization_scope.json()["knowledge"]["departments"], []
+        )
+
+    def test_department_manager_can_create_own_scope_but_cannot_expand_it(self) -> None:
+        self.client.force_authenticate(self.sales_employee.user)
+        created = self._post(
+            {
+                "title": "Sales only API",
+                "categoryId": self.guides.id,
+                "visibility": KnowledgeVisibility.DEPARTMENTS,
+                "departmentIds": [self.sales.id],
+            }
+        )
+        self.assertEqual(created.status_code, 201)
+        knowledge_id = created.json()["knowledge"]["id"]
+
+        denied = self.client.patch(
+            f"/api/v1/ai/knowledge/{knowledge_id}/",
+            data=json.dumps({"departmentIds": [self.sales.id, self.support.id]}),
+            content_type="application/json",
+        )
+        self.assertEqual(denied.status_code, 403)
+        self.assertEqual(
+            set(
+                Knowledge.objects.get(id=knowledge_id).departments.values_list(
+                    "id", flat=True
+                )
+            ),
+            {self.sales.id},
+        )
+
+    def test_list_filters_category_department_visibility_and_status(self) -> None:
+        created = self._post(
+            {
+                "title": "Disabled filtered guide",
+                "description": "Unique filter phrase",
+                "categoryId": self.guides.id,
+                "visibility": KnowledgeVisibility.DEPARTMENTS,
+                "departmentIds": [self.sales.id],
+                "isEnabled": False,
+            }
+        ).json()["knowledge"]
+        response = self.client.get(
+            "/api/v1/ai/knowledge/",
+            {
+                "category": self.guides.id,
+                "department": self.sales.id,
+                "visibility": KnowledgeVisibility.DEPARTMENTS,
+                "isEnabled": "false",
+                "search": "unique filter",
+            },
+        )
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(
+            [item["id"] for item in response.json()["items"]], [created["id"]]
+        )
+
+        invalid = self.client.get(
+            "/api/v1/ai/knowledge/", {"visibility": "PUBLIC"}
+        )
+        self.assertEqual(invalid.status_code, 400)
diff --git a/apps/backend/hub_platform/ai/test_knowledge_category_api.py b/apps/backend/hub_platform/ai/test_knowledge_category_api.py
new file mode 100644
index 0000000..560c182
--- /dev/null
+++ b/apps/backend/hub_platform/ai/test_knowledge_category_api.py
@@ -0,0 +1,109 @@
+import json
+
+from hub_platform.ai.knowledge_policy_test_base import KnowledgePolicyTestBase
+from hub_platform.ai.models import KnowledgeCategory
+from hub_platform.subscriptions.testing import create_test_subscription
+from hub_platform.testing import TenantAPIClient
+
+
+class KnowledgeCategoryApiTests(KnowledgePolicyTestBase):
+    def setUp(self) -> None:
+        super().setUp()
+        create_test_subscription(self.organization)
+        self.client = TenantAPIClient()
+        self.client.force_authenticate(self.organization_manager.user)
+
+    def _create(
+        self, name: str, *, parent_id: int | None = None, sort_order: int = 0
+    ):
+        payload = {"name": name, "sortOrder": sort_order}
+        if parent_id is not None:
+            payload["parentId"] = parent_id
+        return self.client.post(
+            "/api/v1/ai/knowledge/categories/",
+            data=json.dumps(payload),
+            content_type="application/json",
+        )
+
+    def test_tree_is_preordered_and_counts_only_authorized_knowledge(self) -> None:
+        child = self._create("Child", parent_id=self.products.id).json()["category"]
+
+        response = self.client.get("/api/v1/ai/knowledge/categories/")
+
+        self.assertEqual(response.status_code, 200)
+        items = response.json()["items"]
+        ids = [item["id"] for item in items]
+        self.assertLess(ids.index(self.products.id), ids.index(child["id"]))
+        products = next(item for item in items if item["id"] == self.products.id)
+        self.assertEqual(products["knowledgeCount"], 5)
+
+        self.client.force_authenticate(self.sales_employee.user)
+        restricted = self.client.get("/api/v1/ai/knowledge/categories/")
+        products = next(
+            item
+            for item in restricted.json()["items"]
+            if item["id"] == self.products.id
+        )
+        self.assertEqual(products["knowledgeCount"], 4)
+        denied = self._create("Forbidden")
+        self.assertEqual(denied.status_code, 403)
+
+    def test_create_update_move_reorder_and_cycle_validation(self) -> None:
+        root = self._create("Root", sort_order=10)
+        self.assertEqual(root.status_code, 201)
+        root_id = root.json()["category"]["id"]
+        child_id = self._create("Child", parent_id=root_id).json()["category"]["id"]
+
+        updated = self.client.patch(
+            f"/api/v1/ai/knowledge/categories/{child_id}/",
+            data=json.dumps(
+                {"name": "Renamed", "parentId": None, "sortOrder": 25}
+            ),
+            content_type="application/json",
+        )
+        self.assertEqual(updated.status_code, 200)
+        self.assertEqual(updated.json()["category"]["name"], "Renamed")
+        self.assertIsNone(updated.json()["category"]["parentId"])
+        self.assertEqual(updated.json()["category"]["sortOrder"], 25)
+
+        self.client.patch(
+            f"/api/v1/ai/knowledge/categories/{child_id}/",
+            data=json.dumps({"parentId": root_id}),
+            content_type="application/json",
+        )
+        cycle = self.client.patch(
+            f"/api/v1/ai/knowledge/categories/{root_id}/",
+            data=json.dumps({"parentId": child_id}),
+            content_type="application/json",
+        )
+        self.assertEqual(cycle.status_code, 400)
+        self.assertIsNone(KnowledgeCategory.objects.get(id=root_id).parent_id)
+
+    def test_delete_is_limited_to_empty_non_system_leaf(self) -> None:
+        empty_id = self._create("Empty").json()["category"]["id"]
+        deleted = self.client.delete(
+            f"/api/v1/ai/knowledge/categories/{empty_id}/"
+        )
+        self.assertEqual(deleted.status_code, 204)
+
+        nonempty = self.client.delete(
+            f"/api/v1/ai/knowledge/categories/{self.products.id}/"
+        )
+        self.assertEqual(nonempty.status_code, 400)
+        system = KnowledgeCategory.objects.get(
+            organization=self.organization, is_system=True
+        )
+        protected = self.client.delete(
+            f"/api/v1/ai/knowledge/categories/{system.id}/"
+        )
+        self.assertEqual(protected.status_code, 400)
+
+        other_parent = KnowledgeCategory.objects.get(
+            organization=self.other_organization, is_system=True
+        )
+        cross_tenant = self.client.post(
+            "/api/v1/ai/knowledge/categories/",
+            data=json.dumps({"name": "Invalid", "parentId": other_parent.id}),
+            content_type="application/json",
+        )
+        self.assertEqual(cross_tenant.status_code, 400)
diff --git a/apps/backend/hub_platform/ai/urls.py b/apps/backend/hub_platform/ai/urls.py
index bd664a4..b5402d1 100644
--- a/apps/backend/hub_platform/ai/urls.py
+++ b/apps/backend/hub_platform/ai/urls.py
@@ -1,6 +1,6 @@
 from django.urls import path
 
-from hub_platform.ai import agent_views, views
+from hub_platform.ai import agent_views, category_views, views
 
 urlpatterns = [
     path("agents/", agent_views.AIAgentListView.as_view(), name="ai-agent-list"),
@@ -9,6 +9,16 @@ urlpatterns = [
     path("agents/<int:agent_id>/activate/", agent_views.AIAgentActivateView.as_view(), name="ai-agent-activate"),
     path("agents/<int:agent_id>/deactivate/", agent_views.AIAgentDeactivateView.as_view(), name="ai-agent-deactivate"),
     path("knowledge/", views.KnowledgeListCreateView.as_view(), name="ai-knowledge-list"),
+    path(
+        "knowledge/categories/",
+        category_views.KnowledgeCategoryListCreateView.as_view(),
+        name="ai-knowledge-category-list",
+    ),
+    path(
+        "knowledge/categories/<int:category_id>/",
+        category_views.KnowledgeCategoryDetailView.as_view(),
+        name="ai-knowledge-category-detail",
+    ),
     path("knowledge/import/", views.KnowledgeImportView.as_view(), name="ai-knowledge-import"),
     path("knowledge/<int:knowledge_id>/", views.KnowledgeDetailView.as_view(), name="ai-knowledge-detail"),
     path("knowledge/<int:knowledge_id>/attachments/", views.KnowledgeAttachmentUploadView.as_view(), name="ai-knowledge-attachment-upload"),
diff --git a/apps/backend/hub_platform/ai/views.py b/apps/backend/hub_platform/ai/views.py
index bf54f80..ecf3d4b 100644
--- a/apps/backend/hub_platform/ai/views.py
+++ b/apps/backend/hub_platform/ai/views.py
@@ -4,19 +4,13 @@ from rest_framework.request import Request
 from rest_framework.response import Response
 from rest_framework.views import APIView
 
-from hub_platform.ai.models import Knowledge
-from hub_platform.ai.knowledge_policy import require_knowledge_create
-from hub_platform.ai.knowledge_types import KnowledgeVisibility
-from hub_platform.ai.selectors import (
-    KnowledgeFilters,
-    apply_knowledge_filters,
-    knowledge_for_context,
-    knowledge_item_for_context,
-    writable_knowledge_for_employee,
-    writable_knowledge_item_for_employee,
+from hub_platform.ai.api_errors import validation_error_response
+from hub_platform.ai.knowledge_api_inputs import knowledge_filters, knowledge_input
+from hub_platform.ai.knowledge_policy import (
+    employee_can_write_knowledge,
+    require_knowledge_create,
 )
-from hub_platform.ai.serializers import attachment_payload, knowledge_payload
-from hub_platform.ai.services import (
+from hub_platform.ai.knowledge_services import (
     KnowledgeInput,
     add_attachment,
     create_knowledge,
@@ -24,62 +18,21 @@ from hub_platform.ai.services import (
     delete_knowledge,
     update_knowledge,
 )
+from hub_platform.ai.knowledge_types import KnowledgeVisibility
+from hub_platform.ai.models import Knowledge
+from hub_platform.ai.selectors import (
+    apply_knowledge_filters,
+    knowledge_for_context,
+    knowledge_item_for_context,
+    writable_knowledge_for_employee,
+    writable_knowledge_item_for_employee,
+)
+from hub_platform.ai.serializers import attachment_payload, knowledge_payload
 from hub_platform.api.permissions import HasCapability, HasEntitlement
 from hub_platform.identity.audit import record_audit_event
 
 
-def _validation_error(error: ValidationError) -> Response:
-    detail = "; ".join(message for messages in error.message_dict.values() for message in messages) if hasattr(error, "message_dict") else "; ".join(error.messages)
-    return Response({"detail": detail}, status=400)
-
-
-# --- Знания (ADR-HUB-0023) ---
-
-
-def _knowledge_input(body: dict[str, object], *, current: Knowledge | None = None) -> KnowledgeInput:
-    is_enabled = body.get("isEnabled", current.is_enabled if current else True)
-    return KnowledgeInput(
-        title=str(body.get("title", current.title if current else "")),
-        description=str(body.get("description", current.description if current else "")),
-        content=str(body.get("content", current.content if current else "")),
-        is_enabled=bool(is_enabled),
-    )
-
-
-def _optional_id(value: str | None, field: str) -> int | None:
-    if value in (None, ""):
-        return None
-    try:
-        parsed = int(value)
-    except (TypeError, ValueError) as error:
-        raise ValidationError({field: "Integer id required"}) from error
-    if parsed <= 0:
-        raise ValidationError({field: "Positive integer id required"})
-    return parsed
-
-
-def _knowledge_filters(request: Request) -> KnowledgeFilters:
-    visibility = request.query_params.get("visibility") or None
-    if visibility is not None and visibility not in KnowledgeVisibility.values:
-        raise ValidationError({"visibility": "Unknown knowledge visibility"})
-    raw_enabled = request.query_params.get("isEnabled")
-    if raw_enabled in (None, ""):
-        is_enabled = None
-    elif raw_enabled.lower() == "true":
-        is_enabled = True
-    elif raw_enabled.lower() == "false":
-        is_enabled = False
-    else:
-        raise ValidationError({"isEnabled": "Boolean required"})
-    return KnowledgeFilters(
-        category_id=_optional_id(request.query_params.get("category"), "category"),
-        department_id=_optional_id(
-            request.query_params.get("department"), "department"
-        ),
-        visibility=visibility,
-        is_enabled=is_enabled,
-        search=request.query_params.get("search", ""),
-    )
+_validation_error = validation_error_response
 
 
 class _KnowledgeBaseView(APIView):
@@ -118,7 +71,7 @@ class _KnowledgeBaseView(APIView):
 class KnowledgeListCreateView(_KnowledgeBaseView):
     def get(self, request: Request) -> Response:
         try:
-            filters = _knowledge_filters(request)
+            filters = knowledge_filters(request)
         except ValidationError as error:
             return _validation_error(error)
         items = apply_knowledge_filters(
@@ -128,14 +81,15 @@ class KnowledgeListCreateView(_KnowledgeBaseView):
 
     def post(self, request: Request) -> Response:
         try:
+            data = knowledge_input(request.data)
             require_knowledge_create(
                 context=request.tenant_context,
-                visibility=KnowledgeVisibility.ORGANIZATION,
-                department_ids=[],
+                visibility=data.visibility or KnowledgeVisibility.ORGANIZATION,
+                department_ids=data.department_ids or (),
             )
             knowledge = create_knowledge(
                 context=request.tenant_context,
-                data=_knowledge_input(request.data),
+                data=data,
             )
         except ValidationError as error:
             return _validation_error(error)
@@ -158,10 +112,18 @@ class KnowledgeDetailView(_KnowledgeBaseView):
         except Knowledge.DoesNotExist:
             return Response({"detail": "Knowledge not found"}, status=404)
         try:
+            data = knowledge_input(request.data, current=knowledge)
+            if not employee_can_write_knowledge(
+                context=request.tenant_context,
+                knowledge=knowledge,
+                visibility=data.visibility,
+                department_ids=data.department_ids,
+            ):
+                raise PermissionDenied("Knowledge scope is not manageable")
             knowledge = update_knowledge(
                 context=request.tenant_context,
                 knowledge=knowledge,
-                data=_knowledge_input(request.data, current=knowledge),
+                data=data,
             )
         except ValidationError as error:
             return _validation_error(error)