diff --git a/app/routes/keys.py b/app/routes/keys.py
index 2d1ca86..380b845 100644
--- a/app/routes/keys.py
+++ b/app/routes/keys.py
@@ -5,7 +5,7 @@
 from datetime import datetime, timezone
 
 from fastapi import APIRouter, Depends, HTTPException, Response
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -20,16 +20,46 @@
 
 class CreateKey(BaseModel):
     name: str
+    # Optional restrictions for child keys. Only reachable by unrestricted
+    # callers (require_unrestricted above), so a restricted key can never
+    # mint a sibling with looser limits than its own — it can't mint at all.
+    model_allowlist: list[str] | None = None
+    budget_limit_cents: int | None = Field(default=None, gt=0)
+
+
+def require_unrestricted(kc: KeyContext) -> None:
+    """Key management is reserved for unrestricted keys.
+
+    A key that carries any restriction (`model_allowlist` or
+    `budget_limit_cents`) must not be able to mint, list, or revoke other
+    keys — otherwise it could create a sibling with no restrictions and
+    trivially bypass its own allowlist/budget. Unrestricted keys already
+    hold the maximum privilege this single-workspace edition exposes
+    (same trust level as PUT /v1/providers/*), so denying restricted keys
+    here grants nothing to anyone; it only closes the escalation path.
+    """
+    if kc.model_allowlist is not None or kc.budget_limit_cents is not None:
+        raise HTTPException(
+            status_code=403,
+            detail=(
+                "Restricted API keys cannot manage keys. "
+                "Use an unrestricted key."
+            ),
+        )
 
 
 @router.get("")
 async def list_keys(
-    _kc: KeyContext = Depends(get_key_context),
+    kc: KeyContext = Depends(get_key_context),
     db: AsyncSession = Depends(get_db),
 ) -> dict:
+    require_unrestricted(kc)
     rows = (
         await db.execute(
-            select(ApiKey).where(ApiKey.is_deleted == 0).order_by(ApiKey.created_at)
+            select(ApiKey).where(
+                ApiKey.workspace_id == kc.workspace_id,
+                ApiKey.is_deleted == 0,
+            ).order_by(ApiKey.created_at)
         )
     ).scalars().all()
     return {
@@ -54,12 +84,15 @@ async def create_key(
     kc: KeyContext = Depends(get_key_context),
     db: AsyncSession = Depends(get_db),
 ) -> dict:
+    require_unrestricted(kc)
     full_key, key_hash, key_prefix = generate_api_key()
     row = ApiKey(
         workspace_id=kc.workspace_id,
         name=body.name,
         key_hash=key_hash,
         key_prefix=key_prefix,
+        model_allowlist=body.model_allowlist,
+        budget_limit_cents=body.budget_limit_cents,
     )
     db.add(row)
     await db.commit()
@@ -70,18 +103,28 @@ async def create_key(
         "name": row.name,
         "key_prefix": row.key_prefix,
         "api_key": full_key,  # plaintext shown ONCE
+        "model_allowlist": row.model_allowlist,
+        "budget_limit_cents": row.budget_limit_cents,
     }
 
 
 @router.delete("/{key_id}", status_code=204)
 async def revoke_key(
     key_id: str,
-    _kc: KeyContext = Depends(get_key_context),
+    kc: KeyContext = Depends(get_key_context),
     db: AsyncSession = Depends(get_db),
 ) -> Response:
+    require_unrestricted(kc)
     row = (
         await db.execute(
-            select(ApiKey).where(ApiKey.id == key_id, ApiKey.is_deleted == 0)
+            select(ApiKey).where(
+                ApiKey.id == key_id,
+                # Workspace scoping: without this, any key could revoke any
+                # other workspace's keys (the write path has always been
+                # scoped; the read/delete paths were not).
+                ApiKey.workspace_id == kc.workspace_id,
+                ApiKey.is_deleted == 0,
+            )
         )
     ).scalar_one_or_none()
     if row is None:
diff --git a/tests/integration/test_keys_authz.py b/tests/integration/test_keys_authz.py
new file mode 100644
index 0000000..b0a7965
--- /dev/null
+++ b/tests/integration/test_keys_authz.py
@@ -0,0 +1,221 @@
+"""Key-management authorization tests.
+
+A restricted key (model_allowlist or budget_limit_cents set) must never be
+able to mint, list, or revoke API keys — otherwise it could mint an
+unrestricted sibling and bypass its own restrictions entirely.
+See issue: restricted-key privilege escalation via POST /v1/keys.
+"""
+
+import pytest
+
+
+@pytest.fixture
+async def seeded_keys(db_session):
+    """Seed the workspace root key plus one restricted and one budgeted key.
+
+    Returns (root_full_key, restricted_full_key, budgeted_full_key).
+    """
+    from app.seed import seed_initial_state
+    from packages.auth.hashing import generate_api_key
+    from packages.db.models.api_key import ApiKey
+
+    seed = await seed_initial_state(db_session)
+    assert seed.api_key is not None
+
+    def _make(**kwargs) -> str:
+        full_key, key_hash, key_prefix = generate_api_key()
+        row = ApiKey(
+            workspace_id="default",
+            name=kwargs.pop("name", "test"),
+            key_hash=key_hash,
+            key_prefix=key_prefix,
+            **kwargs,
+        )
+        db_session.add(row)
+        return full_key
+
+    # flush once so all rows land before any request reads them
+    restricted = _make(name="restricted", model_allowlist=["gpt-4o-mini"])
+    budgeted = _make(name="budgeted", budget_limit_cents=500)
+    await db_session.commit()
+    return seed.api_key, restricted, budgeted
+
+
+@pytest.fixture
+async def keys_app(db_session, monkeypatch):
+    """FastAPI app with auth middleware and only the /v1/keys routes mounted."""
+    monkeypatch.setenv("DATABASE_URL", str(db_session.bind.url))
+    from fastapi import FastAPI
+
+    from app.middleware.auth import AuthMiddleware
+    from packages.db import session as session_mod
+
+    class _PassthroughFactory:
+        async def __aenter__(self):
+            return db_session
+
+        async def __aexit__(self, *exc):
+            return False  # propagate, don't close — fixture owns the session
+
+    monkeypatch.setattr(session_mod, "_session_factory", lambda: _PassthroughFactory())
+
+    from app.routes.keys import router as keys_router
+
+    app = FastAPI()
+    app.add_middleware(AuthMiddleware)
+    app.include_router(keys_router)
+    return app
+
+
+async def _client(app):
+    from httpx import ASGITransport, AsyncClient
+
+    return AsyncClient(transport=ASGITransport(app=app), base_url="http://t")
+
+
+@pytest.mark.parametrize("which", [1, 2], ids=["allowlist-restricted", "budget-restricted"])
+async def test_restricted_key_cannot_create_keys(keys_app, seeded_keys, db_session, which):
+    keys, restricted, budgeted = seeded_keys
+    caller = (restricted, budgeted)[which - 1]
+    async with await _client(keys_app) as c:
+        r = await c.post(
+            "/v1/keys",
+            json={"name": "escalated"},
+            headers={"Authorization": f"Bearer {caller}"},
+        )
+    assert r.status_code == 403
+    # The escalation must not have persisted anything.
+    from sqlalchemy import func, select
+
+    from packages.db.models.api_key import ApiKey
+
+    count = (
+        await db_session.execute(select(func.count()).select_from(ApiKey))
+    ).scalar_one()
+    assert count == 3  # root + restricted + budgeted, nothing new
+
+
+@pytest.mark.parametrize("which", [1, 2], ids=["allowlist-restricted", "budget-restricted"])
+async def test_restricted_key_cannot_list_keys(keys_app, seeded_keys, which):
+    keys, restricted, budgeted = seeded_keys
+    caller = (restricted, budgeted)[which - 1]
+    async with await _client(keys_app) as c:
+        r = await c.get("/v1/keys", headers={"Authorization": f"Bearer {caller}"})
+    assert r.status_code == 403
+
+
+async def test_restricted_key_cannot_revoke_keys(keys_app, seeded_keys, db_session):
+    _, restricted, _budgeted = seeded_keys
+    from sqlalchemy import select
+
+    from packages.db.models.api_key import ApiKey
+
+    rows = (await db_session.execute(select(ApiKey))).scalars().all()
+    target_id = next(r.id for r in rows if r.name == "default")
+    async with await _client(keys_app) as c:
+        r = await c.delete(
+            f"/v1/keys/{target_id}",
+            headers={"Authorization": f"Bearer {restricted}"},
+        )
+    assert r.status_code == 403
+    target = next(r for r in rows if r.name == "default")
+    assert target.is_active  # untouched
+
+
+async def test_unrestricted_key_retains_full_management(keys_app, seeded_keys):
+    root, _restricted, _budgeted = seeded_keys
+    h = {"Authorization": f"Bearer {root}"}
+    async with await _client(keys_app) as c:
+        listed = await c.get("/v1/keys", headers=h)
+        assert listed.status_code == 200
+
+        created = await c.post("/v1/keys", json={"name": "child"}, headers=h)
+        assert created.status_code == 201
+        child_id = created.json()["id"]
+
+        revoked = await c.delete(f"/v1/keys/{child_id}", headers=h)
+        assert revoked.status_code == 204
+
+
+async def test_create_key_accepts_restrictions(keys_app, seeded_keys, db_session):
+    root, *_ = seeded_keys
+    h = {"Authorization": f"Bearer {root}"}
+    async with await _client(keys_app) as c:
+        r = await c.post(
+            "/v1/keys",
+            json={"name": "team-a", "model_allowlist": ["gpt-4o-mini"], "budget_limit_cents": 500},
+            headers=h,
+        )
+    assert r.status_code == 201, r.text
+    body = r.json()
+    assert body["model_allowlist"] == ["gpt-4o-mini"]
+    assert body["budget_limit_cents"] == 500
+
+    from sqlalchemy import select
+
+    from packages.db.models.api_key import ApiKey
+
+    row = (
+        await db_session.execute(select(ApiKey).where(ApiKey.id == body["id"]))
+    ).scalar_one()
+    assert row.budget_limit_cents == 500
+    assert row.model_allowlist == ["gpt-4o-mini"]
+
+
+# ── Workspace scoping (IDOR regression tests) ────────────────────────────
+
+
+async def _make_foreign_workspace_key(db_session) -> tuple[str, str]:
+    """A key belonging to a different workspace; returns (id, name)."""
+    from packages.auth.hashing import generate_api_key
+    from packages.db.models.api_key import ApiKey
+    from packages.db.models.workspace import Workspace
+
+    db_session.add(Workspace(id="ws-other", name="Other", slug="other"))
+    await db_session.flush()
+
+    full_key, key_hash, key_prefix = generate_api_key()
+    row = ApiKey(
+        workspace_id="ws-other",
+        name="foreign-key",
+        key_hash=key_hash,
+        key_prefix=key_prefix,
+    )
+    db_session.add(row)
+    await db_session.commit()
+    return row.id, full_key
+
+
+async def test_list_keys_hides_other_workspaces(keys_app, seeded_keys, db_session):
+    root, *_ = seeded_keys
+    foreign_id, _foreign_key = await _make_foreign_workspace_key(db_session)
+
+    async with await _client(keys_app) as c:
+        r = await c.get(
+            "/v1/keys", headers={"Authorization": f"Bearer {root}"}
+        )
+
+    assert r.status_code == 200
+    listed_ids = {k["id"] for k in r.json()["keys"]}
+    assert foreign_id not in listed_ids
+
+
+async def test_revoke_rejects_other_workspaces_key(keys_app, seeded_keys, db_session):
+    from sqlalchemy import select
+
+    from packages.db.models.api_key import ApiKey
+
+    root, *_ = seeded_keys
+    foreign_id, _foreign_key = await _make_foreign_workspace_key(db_session)
+
+    async with await _client(keys_app) as c:
+        r = await c.delete(
+            f"/v1/keys/{foreign_id}",
+            headers={"Authorization": f"Bearer {root}"},
+        )
+
+    assert r.status_code == 404
+    row = (
+        await db_session.execute(select(ApiKey).where(ApiKey.id == foreign_id))
+    ).scalar_one()
+    assert row.is_active  # untouched