diff --git a/src/psyc/cockpit/federation_routes.py b/src/psyc/cockpit/federation_routes.py
index ae915a5..8d415bf 100644
--- a/src/psyc/cockpit/federation_routes.py
+++ b/src/psyc/cockpit/federation_routes.py
@@ -15,7 +15,7 @@ from fastapi.responses import HTMLResponse, JSONResponse, PlainTextResponse, Red
 from fastapi.templating import Jinja2Templates
 
 from psyc import db, log
-from psyc.lines import discovery, federation, network_view, pulse, translog
+from psyc.lines import discovery, federation, network_view, pulse, topology_export, translog
 from psyc.result import Err
 
 
@@ -39,6 +39,11 @@ _PUBLIC_NETWORK_TTL = 60.0
 _EXPLORE_CACHE: Dict[str, Any] = {"ts": 0.0, "payload": None, "domain": None}
 _EXPLORE_TTL = 60.0
 
+# Sanitized docker topology cache. The build call hits the docker-socket-proxy
+# sidecar; polled peer admin pages mustn't re-trigger that on every poke.
+_TOPOLOGY_CACHE: Dict[str, Any] = {"ts": 0.0, "payload": None}
+_TOPOLOGY_TTL = 60.0
+
 
 # Headers we slap on every public endpoint so other psyc nodes' explore
 # pages can fetch them cross-origin from the browser.
@@ -77,6 +82,16 @@ def _cached_public_network() -> Dict[str, Any]:
     return _PUBLIC_NETWORK_CACHE["payload"]
 
 
+def _cached_topology() -> Dict[str, Any]:
+    """Cached sanitized docker topology — same poll-load pattern as the feed."""
+    now = time.time()
+    if _TOPOLOGY_CACHE["payload"] is None or (now - _TOPOLOGY_CACHE["ts"]) > _TOPOLOGY_TTL:
+        export = topology_export.build_export()
+        _TOPOLOGY_CACHE["payload"] = export.model_dump(mode="json")
+        _TOPOLOGY_CACHE["ts"] = now
+    return _TOPOLOGY_CACHE["payload"]
+
+
 def _cached_explore(domain: Optional[str]) -> Dict[str, Any]:
     """Cached explore payload. Re-uses the cache when the host domain matches.
 
@@ -257,6 +272,17 @@ def register(app: FastAPI, TEMPLATES: Jinja2Templates) -> None:
         """
         return _public_json(_cached_public_network())
 
+    @app.get("/federation/topology")
+    def federation_topology_public() -> JSONResponse:
+        """Sanitized docker topology — public, for peer-side display.
+
+        Whitelist-only: container names + images + state + network names. No
+        env vars, no volume mounts, no IPs/MACs/gateways, no labels. CORS open
+        so a peer's `/admin/federation/network` page can fetch it from the
+        browser and render every node's containers alongside its own.
+        """
+        return _public_json(_cached_topology())
+
     # ---------- public vouches + transparency log --------------------
 
     @app.get("/federation/vouches")
diff --git a/tests/test_topology_export.py b/tests/test_topology_export.py
index c31f665..02b7c2a 100644
--- a/tests/test_topology_export.py
+++ b/tests/test_topology_export.py
@@ -1,24 +1,25 @@
-"""Topology export — whitelist sanitization unit tests.
+"""Topology export — whitelist sanitization + endpoint contract.
 
 The big invariant: nothing from docker_view.topology() escapes that isn't
 in the Pydantic schema. We assert via model_fields introspection AND via a
 JSON-dump scan over a fixture that contains every dangerous field.
-
-The /federation/topology endpoint contract lives in the sibling tests added
-alongside it; this module covers the builder + the sanitizer in isolation.
 """
 
 from __future__ import annotations
 
 import json
-from typing import Any, Dict
+from typing import Any, Dict, List
 from unittest.mock import patch
 
 import pytest
+from fastapi import FastAPI
+from fastapi.templating import Jinja2Templates
+from fastapi.testclient import TestClient
 from sqlalchemy import create_engine
+from starlette.middleware.sessions import SessionMiddleware
 
 from psyc import db
-from psyc.cockpit import docker_view
+from psyc.cockpit import docker_view, federation_routes
 from psyc.lines import federation, topology_export
 from psyc.lines.topology_export import (
     TopologyContainer,
@@ -50,6 +51,14 @@ def fed_dir(tmp_path, monkeypatch):
     yield d
 
 
+@pytest.fixture(autouse=True)
+def reset_topology_cache():
+    if hasattr(federation_routes, "_TOPOLOGY_CACHE"):
+        federation_routes._TOPOLOGY_CACHE["payload"] = None
+        federation_routes._TOPOLOGY_CACHE["ts"] = 0.0
+    yield
+
+
 # ---------- fixture data: hostile docker_view output --------------------
 
 # This payload has every leaky field docker_view *could* surface, plus
@@ -243,3 +252,62 @@ def test_build_export_caps_at_max_containers(fresh_db, fed_dir, monkeypatch):
     monkeypatch.setattr(docker_view, "topology", lambda: fake)
     out = build_export()
     assert out.container_count == topology_export.MAX_CONTAINERS
+
+
+# ---------- HTTP endpoint -----------------------------------------------
+
+def _mk_app() -> FastAPI:
+    app = FastAPI()
+    app.add_middleware(SessionMiddleware, secret_key="test-secret")
+    from pathlib import Path as _Path
+    here = _Path(__file__).resolve().parent.parent / "src" / "psyc" / "cockpit" / "templates"
+    templates = Jinja2Templates(directory=str(here))
+    federation_routes.register(app, templates)
+    return app
+
+
+def test_federation_topology_endpoint_returns_json_with_cors(fresh_db, fed_dir, monkeypatch):
+    monkeypatch.setattr(docker_view, "topology", lambda: _LEAKY_TOPOLOGY)
+    client = TestClient(_mk_app())
+    r = client.get("/federation/topology")
+    assert r.status_code == 200
+    assert r.headers.get("access-control-allow-origin") == "*"
+    data = r.json()
+    # Schema check.
+    for key in ("node_fingerprint", "generated_at", "host_name",
+                "container_count", "network_count", "containers", "networks"):
+        assert key in data
+    assert data["container_count"] == 2
+    assert len(data["containers"]) == 2
+    # No leaks in the wire response either.
+    blob = r.text
+    for forbidden in _FORBIDDEN_STRINGS:
+        assert forbidden not in blob, f"leak via endpoint: {forbidden!r}"
+
+
+def test_federation_topology_endpoint_resilient_when_docker_unavailable(fresh_db, fed_dir, monkeypatch):
+    def boom():
+        raise docker_view.DockerProxyError("proxy down")
+    monkeypatch.setattr(docker_view, "topology", boom)
+    client = TestClient(_mk_app())
+    r = client.get("/federation/topology")
+    assert r.status_code == 200
+    data = r.json()
+    assert data["container_count"] == 0
+    assert data["containers"] == []
+
+
+def test_federation_topology_cache_short_circuits_repeated_calls(fresh_db, fed_dir, monkeypatch):
+    """Within TTL, a second hit must not re-call docker_view."""
+    calls = {"n": 0}
+
+    def counted():
+        calls["n"] += 1
+        return _LEAKY_TOPOLOGY
+
+    monkeypatch.setattr(docker_view, "topology", counted)
+    client = TestClient(_mk_app())
+    r1 = client.get("/federation/topology")
+    r2 = client.get("/federation/topology")
+    assert r1.status_code == 200 and r2.status_code == 200
+    assert calls["n"] == 1, "cache should suppress the second docker_view call"