diff --git a/backend/app/api/endpoints/accounts.py b/backend/app/api/endpoints/accounts.py
index ea2e8624..c211a4e0 100644
--- a/backend/app/api/endpoints/accounts.py
+++ b/backend/app/api/endpoints/accounts.py
@@ -23,9 +23,17 @@ from app.schemas.account import AccountResponse, AccountUpdate, AccountInviteCre
 from app.schemas.subscription import SubscriptionResponse, PlanLimitsResponse, UsageResponse, SubscriptionDetails
 from app.schemas.user import UserResponse, AccountRoleUpdate, CoverageUpdate
 from app.core.security import verify_password
-from app.api.deps import get_current_active_user, require_account_owner, require_engineer_or_admin
+from app.api.deps import (
+    get_current_active_user,
+    require_account_owner,
+    require_account_owner_or_admin,
+    require_engineer_or_admin,
+    require_l1_or_above,
+)
+from app.services import l1_category_service
 from app.services.seat_enforcement import check_seat_available, get_seat_usage
 from app.schemas.seat_enforcement import SeatUsage
+from app.schemas.l1_categories import L1CategoriesResponse, L1CategoriesUpdate
 
 _SEAT_CHECKED_ROLES = frozenset({"engineer", "l1_tech"})
 
@@ -164,6 +172,45 @@ async def get_my_account_seat_usage(
     return SeatUsage(engineer=engineer, l1_tech=l1_tech)
 
 
+@router.get("/me/l1-categories", response_model=L1CategoriesResponse)
+async def get_l1_categories(
+    db: Annotated[AsyncSession, Depends(get_db)],
+    current_user: Annotated[User, Depends(require_l1_or_above)],
+):
+    """The account's enabled L1 AI-build categories + the available + hard-floor lists.
+
+    Readable by any L1-or-above user (the walker needs to know what's buildable);
+    only owners/admins may change it (PATCH below).
+    """
+    enabled = await l1_category_service.get_enabled_categories(current_user.account_id, db)
+    return L1CategoriesResponse(
+        enabled=enabled,
+        available=l1_category_service.DEFAULT_L1_CATEGORIES,
+        hard_floor=l1_category_service.HARD_FLOOR_FORBIDDEN,
+    )
+
+
+@router.patch("/me/l1-categories", response_model=L1CategoriesResponse)
+async def set_l1_categories(
+    payload: L1CategoriesUpdate,
+    db: Annotated[AsyncSession, Depends(get_db)],
+    current_user: Annotated[User, Depends(require_account_owner_or_admin)],
+):
+    """Set the account's enabled L1 categories (owner/admin only).
+
+    Unknown and hard-floored keys are dropped by the service before persisting.
+    """
+    enabled = await l1_category_service.set_enabled_categories(
+        current_user.account_id, payload.enabled, db
+    )
+    await db.commit()
+    return L1CategoriesResponse(
+        enabled=enabled,
+        available=l1_category_service.DEFAULT_L1_CATEGORIES,
+        hard_floor=l1_category_service.HARD_FLOOR_FORBIDDEN,
+    )
+
+
 @router.patch("/me", response_model=AccountResponse)
 async def update_my_account(
     data: AccountUpdate,
diff --git a/backend/app/schemas/l1_categories.py b/backend/app/schemas/l1_categories.py
new file mode 100644
index 00000000..5b5180c0
--- /dev/null
+++ b/backend/app/schemas/l1_categories.py
@@ -0,0 +1,14 @@
+"""Schemas for the account L1 AI-build category settings surface (Phase 2A)."""
+from pydantic import BaseModel
+
+
+class L1CategoriesResponse(BaseModel):
+    """Current enabled set + the full available list + the read-only hard floor."""
+    enabled: list[str]
+    available: list[str]
+    hard_floor: list[str]
+
+
+class L1CategoriesUpdate(BaseModel):
+    """Owner/admin write: the new enabled set (unknown/hard-floored keys dropped)."""
+    enabled: list[str]
diff --git a/backend/tests/test_l1_categories_api.py b/backend/tests/test_l1_categories_api.py
new file mode 100644
index 00000000..fe838f0a
--- /dev/null
+++ b/backend/tests/test_l1_categories_api.py
@@ -0,0 +1,119 @@
+"""Tests for the account L1 AI-build category settings API (Phase 2A).
+
+GET /accounts/me/l1-categories — readable by L1-or-above.
+PATCH /accounts/me/l1-categories — owner/admin only; drops unknown/hard-floored keys.
+"""
+import uuid
+
+import pytest
+from httpx import AsyncClient
+from sqlalchemy import delete, select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.subscription import Subscription
+from app.models.user import User
+
+
+async def _register(client: AsyncClient, *, email: str) -> dict:
+    resp = await client.post(
+        "/api/v1/auth/register",
+        json={"email": email, "password": "TestPassword123!", "name": "Test User"},
+    )
+    assert resp.status_code in (200, 201), resp.text
+    return resp.json()
+
+
+async def _login(client: AsyncClient, *, email: str) -> dict:
+    resp = await client.post(
+        "/api/v1/auth/login/json",
+        json={"email": email, "password": "TestPassword123!"},
+    )
+    assert resp.status_code == 200, resp.text
+    return {"Authorization": f"Bearer {resp.json()['access_token']}"}
+
+
+async def _ensure_subscription(db: AsyncSession, account_id: uuid.UUID) -> None:
+    await db.execute(delete(Subscription).where(Subscription.account_id == account_id))
+    db.add(Subscription(account_id=account_id, plan="pro", status="active"))
+    await db.commit()
+
+
+async def _make_user(client: AsyncClient, db: AsyncSession, *, email: str, account_role: str) -> dict:
+    """Register → promote role → ensure subscription → login (after the role change)."""
+    data = await _register(client, email=email)
+    uid = uuid.UUID(data["id"])
+    acct_id = uuid.UUID(data["account_id"])
+    user = (await db.execute(select(User).where(User.id == uid))).scalar_one()
+    user.account_role = account_role
+    await db.commit()
+    await _ensure_subscription(db, acct_id)
+    headers = await _login(client, email=email)
+    return {"headers": headers, "account_id": acct_id, "user_id": uid}
+
+
+@pytest.mark.asyncio
+async def test_get_categories_returns_enabled_available_hard_floor(client: AsyncClient, test_db: AsyncSession):
+    info = await _make_user(client, test_db, email="cat_owner_get@example.com", account_role="owner")
+    r = await client.get("/api/v1/accounts/me/l1-categories", headers=info["headers"])
+    assert r.status_code == 200, r.text
+    body = r.json()
+    assert "enabled" in body and "available" in body and "hard_floor" in body
+    # New account defaults to the full available allowlist (10 keys).
+    assert len(body["available"]) == 10
+    assert "password_reset" in body["available"]
+    assert "registry_edit" in body["hard_floor"]
+
+
+@pytest.mark.asyncio
+async def test_get_categories_readable_by_l1_tech(client: AsyncClient, test_db: AsyncSession):
+    info = await _make_user(client, test_db, email="cat_l1_get@example.com", account_role="l1_tech")
+    r = await client.get("/api/v1/accounts/me/l1-categories", headers=info["headers"])
+    assert r.status_code == 200, r.text
+
+
+@pytest.mark.asyncio
+async def test_patch_categories_owner_can_set(client: AsyncClient, test_db: AsyncSession):
+    info = await _make_user(client, test_db, email="cat_owner_patch@example.com", account_role="owner")
+    r = await client.patch(
+        "/api/v1/accounts/me/l1-categories",
+        json={"enabled": ["printer", "vpn_connect"]},
+        headers=info["headers"],
+    )
+    assert r.status_code == 200, r.text
+    assert set(r.json()["enabled"]) == {"printer", "vpn_connect"}
+
+
+@pytest.mark.asyncio
+async def test_patch_categories_drops_unknown_and_hard_floored(client: AsyncClient, test_db: AsyncSession):
+    info = await _make_user(client, test_db, email="cat_owner_drop@example.com", account_role="owner")
+    r = await client.patch(
+        "/api/v1/accounts/me/l1-categories",
+        json={"enabled": ["printer", "registry_edit", "bogus_key"]},
+        headers=info["headers"],
+    )
+    assert r.status_code == 200, r.text
+    # registry_edit (hard floor) and bogus_key (unknown) are dropped.
+    assert r.json()["enabled"] == ["printer"]
+
+
+@pytest.mark.asyncio
+async def test_patch_categories_forbidden_for_l1_tech(client: AsyncClient, test_db: AsyncSession):
+    info = await _make_user(client, test_db, email="cat_l1_patch@example.com", account_role="l1_tech")
+    r = await client.patch(
+        "/api/v1/accounts/me/l1-categories",
+        json={"enabled": ["printer"]},
+        headers=info["headers"],
+    )
+    assert r.status_code == 403, r.text
+
+
+@pytest.mark.asyncio
+async def test_patch_categories_forbidden_for_engineer(client: AsyncClient, test_db: AsyncSession):
+    """Write is owner/admin only — engineers (who pass require_engineer_or_admin) are blocked."""
+    info = await _make_user(client, test_db, email="cat_eng_patch@example.com", account_role="engineer")
+    r = await client.patch(
+        "/api/v1/accounts/me/l1-categories",
+        json={"enabled": ["printer"]},
+        headers=info["headers"],
+    )
+    assert r.status_code == 403, r.text