diff --git a/tests/proxy_behavior/management/test_key_info.py b/tests/proxy_behavior/management/test_key_info.py
new file mode 100644
index 00000000000..6935d0d3bb9
--- /dev/null
+++ b/tests/proxy_behavior/management/test_key_info.py
@@ -0,0 +1,103 @@
+"""Slice 8 — actor × target authz matrix for ``GET /key/info``.
+
+Targets are three fixed seeded keys representing the canonical relations:
+
+  * **own** — the actor's own key (each actor's relation to itself).
+  * **owner_key** — OWNER actor's key in org_a / team_alpha. From any
+    other org_a / team_alpha actor's perspective this is "same-team, not
+    mine". From cross_org_user's perspective this is cross-org.
+  * **cross_org_user_key** — CROSS_ORG_USER's key in org_b / team_beta.
+    From any org_a actor's perspective this is cross-org.
+
+24 (actor × target) scenarios after applying the matrix; status codes pinned
+against current handler behavior so future PRs that change the visibility
+boundary turn the suite red.
+"""
+
+import pytest
+
+from .actors import Actor
+from .conftest import MASTER_KEY  # noqa: F401  (kept for symmetry with sibling files)
+
+pytestmark = pytest.mark.asyncio(loop_scope="session")
+
+
+# (id, actor, target_actor, expected_status)
+_SCENARIOS = [
+    # ─── target = own key ─────────────────────────────────────────────────
+    ("own/proxy_admin", Actor.PROXY_ADMIN, Actor.PROXY_ADMIN, 200),
+    ("own/org_admin", Actor.ORG_ADMIN, Actor.ORG_ADMIN, 200),
+    ("own/team_admin", Actor.TEAM_ADMIN, Actor.TEAM_ADMIN, 200),
+    ("own/internal_user", Actor.INTERNAL_USER, Actor.INTERNAL_USER, 200),
+    ("own/owner", Actor.OWNER, Actor.OWNER, 200),
+    ("own/unrelated_same_org", Actor.UNRELATED_SAME_ORG, Actor.UNRELATED_SAME_ORG, 200),
+    ("own/cross_org_user", Actor.CROSS_ORG_USER, Actor.CROSS_ORG_USER, 200),
+    ("own/service_account", Actor.SERVICE_ACCOUNT, Actor.SERVICE_ACCOUNT, 200),
+    # ─── target = OWNER's key (org_a / team_alpha) ────────────────────────
+    # NB: org_admin currently 403s on individual key info even within their own
+    # org — visibility is scoped to "your own keys" + "your team's keys", not
+    # "your org's keys". Same-team peers (internal_user, unrelated_same_org,
+    # service_account) DO see each other's keys.
+    ("owner_key/proxy_admin", Actor.PROXY_ADMIN, Actor.OWNER, 200),
+    ("owner_key/org_admin", Actor.ORG_ADMIN, Actor.OWNER, 403),
+    ("owner_key/team_admin", Actor.TEAM_ADMIN, Actor.OWNER, 200),
+    ("owner_key/internal_user", Actor.INTERNAL_USER, Actor.OWNER, 200),
+    ("owner_key/owner", Actor.OWNER, Actor.OWNER, 200),
+    ("owner_key/unrelated_same_org", Actor.UNRELATED_SAME_ORG, Actor.OWNER, 200),
+    ("owner_key/cross_org_user", Actor.CROSS_ORG_USER, Actor.OWNER, 403),
+    ("owner_key/service_account", Actor.SERVICE_ACCOUNT, Actor.OWNER, 200),
+    # ─── target = CROSS_ORG_USER's key (org_b / team_beta) ────────────────
+    ("cross_org/proxy_admin", Actor.PROXY_ADMIN, Actor.CROSS_ORG_USER, 200),
+    ("cross_org/org_admin", Actor.ORG_ADMIN, Actor.CROSS_ORG_USER, 403),
+    ("cross_org/team_admin", Actor.TEAM_ADMIN, Actor.CROSS_ORG_USER, 403),
+    ("cross_org/internal_user", Actor.INTERNAL_USER, Actor.CROSS_ORG_USER, 403),
+    ("cross_org/owner", Actor.OWNER, Actor.CROSS_ORG_USER, 403),
+    (
+        "cross_org/unrelated_same_org",
+        Actor.UNRELATED_SAME_ORG,
+        Actor.CROSS_ORG_USER,
+        403,
+    ),
+    ("cross_org/cross_org_user", Actor.CROSS_ORG_USER, Actor.CROSS_ORG_USER, 200),
+    ("cross_org/service_account", Actor.SERVICE_ACCOUNT, Actor.CROSS_ORG_USER, 403),
+]
+
+
+@pytest.mark.parametrize(
+    "actor,target_actor,expected_status",
+    [(a, t, s) for (_id, a, t, s) in _SCENARIOS],
+    ids=[s[0] for s in _SCENARIOS],
+)
+async def test_key_info_authz_matrix(
+    actor: Actor,
+    target_actor: Actor,
+    expected_status: int,
+    proxy_client,
+    world,
+):
+    caller = world.keys[actor]
+    target = world.keys[target_actor]
+
+    resp = await proxy_client.get(
+        f"/key/info?key={target.cleartext}",
+        headers={"Authorization": f"Bearer {caller.cleartext}"},
+    )
+    assert resp.status_code == expected_status, (
+        f"{actor.value} GET /key/info?key=<{target_actor.value}> → "
+        f"{resp.status_code} (expected {expected_status}). body={resp.text}"
+    )
+
+    if expected_status == 200:
+        body = resp.json()
+        # The handler echoes back whatever ``key`` was passed in the query string,
+        # so body["key"] == cleartext when we querystring it. When the auth key
+        # IS the target (no query), it returns the hashed form. Either match is
+        # fine — the canonical identity check is on info.user_id.
+        assert body.get("key") in (target.cleartext, target.hashed), (
+            f"{actor.value} → target {target_actor.value}: wrong key in response "
+            f"(got {body.get('key')!r}, expected cleartext or hashed of target)"
+        )
+        assert body["info"].get("user_id") == target.user_id, (
+            f"{actor.value} → target {target_actor.value}: wrong user_id "
+            f"(got {body['info'].get('user_id')!r}, expected {target.user_id!r})"
+        )