Cache Plutonium runtime files on hosts

agent/ec_agent.py

@@ -33,7 +33,7 @@ import urllib.parse
 import urllib.request
 import uuid
 
-VERSION = "1.7.0"
+VERSION = "1.8.0"
 LABEL = "io.electric-cherry"
 MAX_FILE = 32 * 1024 * 1024
 MANIFEST_MAX_ENTRIES = 10000
@@ -42,6 +42,10 @@ MANIFEST_MAX_SECONDS = 15
 MANIFEST_MAX_DEPTH = 64
 LIBRARY_DOWNLOAD_WORKERS = 4
 HEALTH_LOCK_TIMEOUT_SECONDS = 5
+PLUTONIUM_MANIFEST_URL = "https://cdn.plutoniummod.com/updater/prod/info.json"
+PLUTONIUM_MANIFEST_LIMIT = 2 * 1024 * 1024
+PLUTONIUM_FILE_LIMIT = 512 * 1024 * 1024
+PLUTONIUM_CACHE_LIMIT = 4 * 1024 * 1024 * 1024
 ID_RE = re.compile(r"^[A-Za-z0-9][A-Za-z0-9_-]{0,127}$")
 AGENT_CONFIG = Path("/etc/electric-cherry/agent.json")
 AGENT_EXECUTABLE = Path("/usr/local/libexec/electric-cherry-agent.py")
@@ -487,6 +491,34 @@ def managed_write(root, value, content, uid=1000, gid=1000):
                 os.unlink(temp_name, dir_fd=parent)
 
 
+def managed_copy(root, value, source, uid=1000, gid=1000):
+    """Copy a private file, using Linux reflinks when supported, never hardlinks."""
+    with managed_open(Path(source).parent, Path(source).name) as incoming:
+        with managed_parent(root, value, create=True, uid=uid, gid=gid) as (parent, name):
+            temp_name = ".ec-" + uuid.uuid4().hex
+            fd = os.open(temp_name, os.O_WRONLY | os.O_CREAT | os.O_EXCL | os.O_NOFOLLOW, 0o600, dir_fd=parent)
+            try:
+                os.fchmod(fd, 0o644)
+                if os.geteuid() == 0:
+                    os.fchown(fd, uid, gid)
+                try:
+                    if not sys.platform.startswith("linux"):
+                        raise OSError("Reflinks unavailable")
+                    fcntl.ioctl(fd, 0x40049409, incoming.fileno())  # FICLONE
+                except OSError:
+                    os.ftruncate(fd, 0)
+                    with os.fdopen(fd, "wb", closefd=False) as outgoing:
+                        shutil.copyfileobj(incoming, outgoing, 1024 * 1024)
+                        outgoing.flush()
+                os.fsync(fd)
+                os.replace(temp_name, name, src_dir_fd=parent, dst_dir_fd=parent)
+                os.fsync(parent)
+            finally:
+                os.close(fd)
+                with contextlib.suppress(FileNotFoundError):
+                    os.unlink(temp_name, dir_fd=parent)
+
+
 class ReadWriteGate:
     """Let observations run together; global mutations wait for existing readers."""
     def __init__(self):
@@ -921,11 +953,13 @@ class Agent:
         self.read_claims = set()
         self.health_probe_gate = threading.BoundedSemaphore(2)
         self.cancelled_creations = frozenset()
+        self.defer_plutonium_preparation = False
         self.observation_keep_days = 0  # Older controllers do not authorize cleanup.
         self.library_progress = {}
         self.library_transfers = {}
         self.inventory_manifest_cache = {}
         self.inventory_manifest_lock = threading.Lock()
+        self.plutonium_lock = threading.RLock()
         self.config_path = config.get("configPath", "/etc/electric-cherry/agent.json")
         self.executing_id = None
         self.lane_lock = threading.Lock()
@@ -1360,8 +1394,9 @@ class Agent:
                 if line.startswith("PRETTY_NAME="):
                     os_name = line.split("=", 1)[1].strip('"')
         update = self.update_inventory()
-        capabilities = ["library.remove", "instance.cancel-create", "instance.safety-override", "instance.autoscaling-remove", "operations.read-lane", "operations.health-lane", "rcon.status-batch", "instance.heartbeat-state", "files.manifest", "files.blobs"] + (["host.decommission"] if self.can_uninstall() else []) + (["agent.update"] if update["enabled"] else [])
+        capabilities = ["library.remove", "plutonium.cache", "instance.cancel-create", "instance.safety-override", "instance.autoscaling-remove", "operations.read-lane", "operations.health-lane", "rcon.status-batch", "instance.heartbeat-state", "files.manifest", "files.blobs"] + (["host.decommission"] if self.can_uninstall() else []) + (["agent.update"] if update["enabled"] else [])
-        return {"hostname": socket.gethostname(), "agentVersion": VERSION, "protocolVersion": 1, "capabilities": capabilities, "agentUpdate": update, "agentLanes": self.lane_inventory(), "os": os_name, "osVersion": platform.release(), "architecture": platform.machine(), "cpu": platform.processor() or platform.machine(), "cpuCount": os.cpu_count() or 0, **resources, **({"cpuUsagePercent": cpu_usage} if cpu_usage is not None else {}), "memoryTotal": memory.get("MemTotal", 0), "memoryAvailable": memory.get("MemAvailable", 0), "storageTotal": usage.total, "storageAvailable": usage.free, "dockerVersion": docker_version, "dockerRunning": docker_running, "directoriesWritable": os.access(self.root, os.W_OK), "runtimeImages": sorted(set(images)), "libraries": libraries, "libraryCaches": caches, "currentOperation": self.current_operation, "portRange": self.config.get("portRange", {"min": 28960, "max": 29060})}
+        plutonium_cache = self.plutonium_cache_inventory()
+        return {"hostname": socket.gethostname(), "agentVersion": VERSION, "protocolVersion": 1, "capabilities": capabilities, "agentUpdate": update, "agentLanes": self.lane_inventory(), "os": os_name, "osVersion": platform.release(), "architecture": platform.machine(), "cpu": platform.processor() or platform.machine(), "cpuCount": os.cpu_count() or 0, **resources, **({"cpuUsagePercent": cpu_usage} if cpu_usage is not None else {}), "memoryTotal": memory.get("MemTotal", 0), "memoryAvailable": memory.get("MemAvailable", 0), "storageTotal": usage.total, "storageAvailable": usage.free, "dockerVersion": docker_version, "dockerRunning": docker_running, "directoriesWritable": os.access(self.root, os.W_OK), "runtimeImages": sorted(set(images)), **({"plutoniumCache": plutonium_cache} if plutonium_cache else {}), "libraries": libraries, "libraryCaches": caches, "currentOperation": self.current_operation, "portRange": self.config.get("portRange", {"min": 28960, "max": 29060})}
 
     def safe_to_disrupt(self, instance_id, generation):
         health = self.inspect(instance_id, generation)
@@ -1510,6 +1545,223 @@ class Agent:
                 raise Rejected("Initial files exceed the 64 MiB operation limit")
         return game, library, image, port, bind, env
 
+    @staticmethod
+    def plutonium_manifest(data):
+        """Validate the official updater format before using any paths or URLs."""
+        if len(data) > PLUTONIUM_MANIFEST_LIMIT:
+            raise AgentError("Plutonium manifest is too large")
+        try:
+            manifest = json.loads(data)
+        except (ValueError, UnicodeError):
+            raise AgentError("Invalid Plutonium manifest") from None
+        if not isinstance(manifest, dict) or manifest.get("product") != "plutonium-core-prod":
+            raise AgentError("Invalid Plutonium production manifest")
+        revision = manifest.get("revision")
+        if type(revision) is not int or not 1 <= revision <= 2147483647:
+            raise AgentError("Invalid Plutonium revision")
+        base = manifest.get("baseUrl")
+        if not isinstance(base, str) or not re.fullmatch(r"https://cdn\.plutoniummod\.com/updater/prod/(?:[A-Za-z0-9_-]+/)*", base):
+            raise AgentError("Plutonium downloads must use the official production CDN")
+        entries = manifest.get("files")
+        if not isinstance(entries, list) or not 1 <= len(entries) <= 4096:
+            raise AgentError("Invalid Plutonium file list")
+        names, total = set(), 0
+        for entry in entries:
+            if not isinstance(entry, dict):
+                raise AgentError("Invalid Plutonium file entry")
+            name, size, checksum = entry.get("name"), entry.get("size"), entry.get("hash")
+            if not isinstance(name, str) or len(name) > 512 or re.search(r'[\x00-\x1f\x7f\\:*?"<>|]', name):
+                raise AgentError("Invalid Plutonium file path")
+            path = PurePosixPath(name)
+            if not path.parts or path.is_absolute() or str(path) != name or any(part in (".", "..") or part.endswith((".", " ")) for part in path.parts) or name.lower() == "cdn_info.json":
+                raise AgentError("Invalid Plutonium file path")
+            if name.lower() in names:
+                raise AgentError("Duplicate Plutonium file path")
+            names.add(name.lower())
+            if type(size) is not int or not 0 <= size <= PLUTONIUM_FILE_LIMIT:
+                raise AgentError("Invalid Plutonium file size")
+            if not isinstance(checksum, str) or not re.fullmatch(r"[a-f0-9]{40}", checksum):
+                raise AgentError("Invalid Plutonium file hash")
+            total += size
+            if total > PLUTONIUM_CACHE_LIMIT:
+                raise AgentError("Plutonium cache exceeds the size limit")
+        for name in names:
+            if any(str(parent) in names for parent in PurePosixPath(name).parents if str(parent) != "."):
+                raise AgentError("Conflicting Plutonium file paths")
+        if "bin/plutonium-bootstrapper-win32.exe" not in {entry["name"] for entry in entries}:
+            raise AgentError("Plutonium manifest is missing the server bootstrapper")
+        # Match plutonium-updater's default: launcher assets are optional.
+        return manifest, [entry for entry in entries if not entry["name"].startswith("launcher")]
+
+    @staticmethod
+    def plutonium_file_matches(root, entry):
+        try:
+            with managed_open(root, entry["name"]) as stream:
+                if os.fstat(stream.fileno()).st_size != entry["size"]:
+                    return False
+                checksum = hashlib.sha1()
+                for chunk in iter(lambda: stream.read(1024 * 1024), b""):
+                    checksum.update(chunk)
+                return checksum.hexdigest() == entry["hash"]
+        except (OSError, AgentError):
+            return False
+
+    def plutonium_open(self, url):
+        if not isinstance(url, str) or not re.fullmatch(r"https://cdn\.plutoniummod\.com/updater/prod/[A-Za-z0-9_./-]+", url):
+            raise AgentError("Plutonium downloads must use the official production CDN")
+        class NoRedirect(urllib.request.HTTPRedirectHandler):
+            def redirect_request(self, req, fp, code, msg, hdrs, newurl):
+                raise AgentError("Plutonium download redirects are not allowed")
+        # Never send the controller's host credentials to the public CDN.
+        return urllib.request.build_opener(NoRedirect()).open(url, timeout=30)
+
+    def plutonium_snapshot(self):
+        root = scoped(self.root / "agent", "plutonium-cache")
+        pointer = json.loads(managed_read(root, "current.json") or b"null")
+        if not isinstance(pointer, dict) or not isinstance(pointer.get("key"), str) or not re.fullmatch(r"[a-f0-9]{64}", pointer["key"]):
+            raise AgentError("Plutonium cache is not prepared")
+        content = scoped(root, pointer["key"] + "/content")
+        raw = managed_read(content, "cdn_info.json")
+        if raw is None or digest(raw) != pointer["key"]:
+            raise AgentError("Plutonium cache manifest is invalid")
+        manifest, files = self.plutonium_manifest(raw)
+        if pointer.get("revision") != manifest["revision"] or pointer.get("bytes") != sum(entry["size"] for entry in files):
+            raise AgentError("Plutonium cache metadata is invalid")
+        # Heartbeat checks are cheap. Every file is hashed before it is seeded.
+        for entry in files:
+            info = scoped(content, entry["name"]).lstat()
+            if not stat_module.S_ISREG(info.st_mode) or info.st_size != entry["size"]:
+                raise AgentError("Plutonium cache files are incomplete")
+        return pointer, content, raw, files
+
+    def plutonium_cache_inventory(self):
+        with self.plutonium_lock:
+            try:
+                pointer, _, _, _ = self.plutonium_snapshot()
+                return {"revision": pointer["revision"], "bytes": pointer["bytes"]}
+            except (OSError, ValueError, AgentError):
+                return None
+
+    def prepare_plutonium(self, payload):
+        target, reserve = payload.get("revision", 0), payload.get("minimumFreeBytes", 0)
+        if type(target) is not int or not 0 <= target <= 2147483647 or type(reserve) is not int or reserve < 0:
+            raise Rejected("Invalid Plutonium preparation request")
+        root = scoped(self.root / "agent", "plutonium-cache")
+        root.mkdir(mode=0o700, exist_ok=True)
+        os.chmod(root, 0o700)
+        deadline = time.monotonic() + 1800
+        def active():
+            if self.stopping.is_set() or time.monotonic() >= deadline:
+                raise AgentError("Plutonium cache preparation was interrupted or timed out")
+            if self.defer_plutonium_preparation:
+                raise Held("Plutonium cache preparation is waiting for other host operations")
+        active()
+        try:
+            with self.plutonium_open(PLUTONIUM_MANIFEST_URL) as response:
+                raw = response.read(PLUTONIUM_MANIFEST_LIMIT + 1)
+            manifest, files = self.plutonium_manifest(raw)
+            if manifest["revision"] < target:
+                raise AgentError("Plutonium CDN has not reached the requested revision")
+            key = digest(raw)
+            previous = None
+            with self.plutonium_lock:
+                with contextlib.suppress(OSError, ValueError, AgentError):
+                    _, previous, _, _ = self.plutonium_snapshot()
+            if previous is not None and previous.parent.name == key and all(self.plutonium_file_matches(previous, entry) for entry in files):
+                return {"revision": manifest["revision"], "bytes": sum(entry["size"] for entry in files)}
+            staging = scoped(root, key + ".partial/content")
+            staging.mkdir(parents=True, exist_ok=True)
+            expected = {entry["name"] for entry in files}
+            # SIGKILL/power loss bypasses download/copy finally blocks. Remove
+            # abandoned temporary files before counting space or publishing.
+            for directory, subdirs, filenames in os.walk(staging, followlinks=False):
+                for name in subdirs + filenames:
+                    path = Path(directory) / name
+                    if path.is_symlink() or (name in filenames and path.relative_to(staging).as_posix() not in expected):
+                        path.unlink()
+            # Keep at most the current snapshot and this resumable preparation.
+            current_key = previous.parent.name if previous is not None else None
+            for directory in root.iterdir():
+                if re.fullmatch(r"[a-f0-9]{64}(?:\.partial)?", directory.name) and directory.name not in (current_key, key + ".partial"):
+                    if directory.is_symlink():
+                        directory.unlink()
+                    else:
+                        shutil.rmtree(directory)
+            missing = sum(entry["size"] for entry in files if not self.plutonium_file_matches(staging, entry))
+            if shutil.disk_usage(root).free < reserve + missing + len(raw):
+                raise AgentError("Insufficient free storage for the Plutonium cache and host reserve")
+            for entry in files:
+                active()
+                if self.plutonium_file_matches(staging, entry):
+                    continue
+                if previous is not None and self.plutonium_file_matches(previous, entry):
+                    managed_copy(staging, entry["name"], scoped(previous, entry["name"]), os.geteuid(), os.getegid())
+                    continue
+                destination = scoped(staging, entry["name"])
+                destination.parent.mkdir(parents=True, exist_ok=True)
+                temporary = destination.with_name(".download-" + uuid.uuid4().hex)
+                try:
+                    with self.plutonium_open(manifest["baseUrl"] + entry["hash"]) as incoming, temporary.open("xb") as outgoing:
+                        size, checksum = 0, hashlib.sha1()
+                        while True:
+                            active()
+                            chunk = incoming.read(min(1024 * 1024, entry["size"] - size + 1))
+                            if not chunk:
+                                break
+                            size += len(chunk)
+                            if size > entry["size"]:
+                                raise AgentError("Plutonium download exceeds its expected size")
+                            checksum.update(chunk)
+                            outgoing.write(chunk)
+                        if size != entry["size"] or checksum.hexdigest() != entry["hash"]:
+                            raise AgentError("Plutonium download failed size or checksum verification")
+                        outgoing.flush()
+                        os.fsync(outgoing.fileno())
+                    os.replace(temporary, destination)
+                    sync_parent(destination)
+                finally:
+                    with contextlib.suppress(FileNotFoundError):
+                        temporary.unlink()
+            # Publish metadata last. Interrupted transfers can never claim ready.
+            active()
+            atomic_bytes(staging / "cdn_info.json", raw)
+            pointer = {"key": key, "revision": manifest["revision"], "bytes": sum(entry["size"] for entry in files)}
+            with self.plutonium_lock:
+                final = scoped(root, key)
+                if final.exists():
+                    # Invalidate before replacing a damaged/same-revision cache.
+                    if current_key == key:
+                        (root / "current.json").unlink(missing_ok=True)
+                    shutil.rmtree(final)
+                os.replace(staging.parent, final)
+                sync_parent(final)
+                atomic_json(root / "current.json", pointer)
+                if previous is not None and current_key != key:
+                    shutil.rmtree(previous.parent)
+            return {"revision": pointer["revision"], "bytes": pointer["bytes"]}
+        except (urllib.error.URLError, TimeoutError, http.client.HTTPException):
+            raise AgentError("Plutonium CDN download is unavailable; the previous cache is retained") from None
+
+    def seed_plutonium(self, app, image):
+        if not re.fullmatch(r"ghcr\.io/ayymoss/plutainer(?::[A-Za-z0-9_.-]+)?(?:@sha256:[a-f0-9]{64})?", image):
+            return False
+        with self.plutonium_lock:
+            try:
+                _, content, raw, files = self.plutonium_snapshot()
+                if not all(self.plutonium_file_matches(content, entry) for entry in files):
+                    scoped(self.root / "agent", "plutonium-cache/current.json").unlink(missing_ok=True)
+                    raise AgentError("Plutonium cache checksum verification failed")
+            except (OSError, ValueError, AgentError):
+                return False
+            uid, gid = int(self.config.get("runtimeUid", 1000)), int(self.config.get("runtimeGid", 1000))
+            marker = "runtime/plutonium/cdn_info.json"
+            managed_write(app, marker, None, uid, gid)
+            for entry in files:
+                self.check_creation_cancellation()
+                managed_copy(app, "runtime/plutonium/" + entry["name"], scoped(content, entry["name"]), uid, gid)
+            managed_write(app, marker, raw, uid, gid)
+            return True
+
     def create(self, instance_id, generation, payload):
         self.check_creation_cancellation()
         directory = self.instance_dir(instance_id, generation)
@@ -1527,6 +1779,7 @@ class Agent:
         app = directory / "app"
         app.mkdir(parents=True, exist_ok=True)
         self.make_writable(app, directory=True)
+        self.seed_plutonium(app, image)
         self.write_initial_files(app, payload.get("files", []))
         atomic_json(directory / "spec.json", payload)
         env_path = directory / "environment"
@@ -2184,6 +2437,8 @@ class Agent:
             return {"image": image, "ready": True}
         if kind == "host.inspect":
             return self.inventory()
+        if kind == "plutonium.prepare":
+            return self.prepare_plutonium(payload)
         if kind == "rcon.status-batch":
             return self.rcon_status_batch(operation)
         if kind == "library.download":
@@ -2290,7 +2545,7 @@ class Agent:
                 if not self.config.get("pendingCredential") or self.recover_credential():
                     return self.journal.update(operation["id"], "completed", {"rotated": True, "reconciled": True})
                 return row
-            if kind == "runtime.pull":
+            if kind in ("runtime.pull", "plutonium.prepare"):
                 # Docker resumes already downloaded layers. Pull again under
                 # the same operation ID: an existing tag can still refer to an
                 # older image and cannot prove an interrupted pull completed.
@@ -2298,6 +2553,8 @@ class Agent:
                 try:
                     result = self.dispatch(operation)
                     return self.journal.update(operation["id"], "completed", {**result, "reconciled": True})
+                except Held as err:
+                    return self.journal.update(operation["id"], "accepted", {"blocked": "host-busy", "message": str(err)})
                 except Exception:
                     return self.journal.update(operation["id"], "failed", error="Interrupted runtime download could not be resumed")
             if kind == "library.import":
@@ -2407,6 +2664,7 @@ class Agent:
         # Only the heartbeat thread replaces this immutable snapshot; it never
         # mutates the operation journal or races Docker cleanup against create.
         self.cancelled_creations = frozenset(value for value in response.get("cancelledCreations", []) if isinstance(value, str))
+        self.defer_plutonium_preparation = response.get("deferPlutoniumPreparation") is True
         keep_days = response.get("observationKeepDays")
         self.observation_keep_days = keep_days if valid_observation_keep_days(keep_days) else 0
         host = response.get("host", {})

agent/tests/test_plutonium_cache.py

@@ -0,0 +1,506 @@
+import base64
+import copy
+import hashlib
+import json
+from pathlib import Path
+import unittest
+from unittest.mock import patch
+import urllib.error
+
+import test_agent as fixtures
+
+
+module = fixtures.module
+AgentError = fixtures.AgentError
+IMAGE = "ghcr.io/ayymoss/plutainer:latest"
+BOOTSTRAPPER = "bin/plutonium-bootstrapper-win32.exe"
+BASE_URL = "https://cdn.plutoniummod.com/updater/prod/files/"
+
+
+class PlutoniumCacheTests(unittest.TestCase):
+    tearDown = fixtures.AgentTests.tearDown
+    operation = fixtures.AgentTests.operation
+    create = fixtures.AgentTests.create
+
+    def setUp(self):
+        fixtures.AgentTests.setUp(self)
+        network = patch.object(self.agent, "plutonium_open", side_effect=AssertionError("Unexpected vendor request"), create=True)
+        network.start()
+        self.addCleanup(network.stop)
+
+    def release(self, revision=5354, contents=None):
+        contents = contents or {
+            BOOTSTRAPPER: b"bootstrapper",
+            "bin/plutonium.dll": b"runtime",
+            "storage/t5/zone/plutonium.ff": b"zone-data",
+            "storage/iw5/images/~weapon_ak47_iw5_spc-rgb&weap~fa48e615.iwi": b"texture-data",
+            "launcher/plutonium.exe": b"launcher-not-needed",
+        }
+        manifest = {
+            "product": "plutonium-core-prod",
+            "revision": revision,
+            "baseUrl": BASE_URL,
+            "files": [
+                {"name": name, "size": len(content), "hash": hashlib.sha1(content).hexdigest()}
+                for name, content in contents.items()
+            ],
+        }
+        return manifest, contents
+
+    def opener(self, manifest, contents, calls=None):
+        calls = calls if calls is not None else []
+
+        def open_url(url):
+            calls.append(url)
+            if url == module.PLUTONIUM_MANIFEST_URL:
+                return fixtures.Response(json.dumps(manifest).encode())
+            self.assertTrue(url.startswith(BASE_URL), url)
+            name = next(entry["name"] for entry in manifest["files"] if url == BASE_URL + entry["hash"])
+            return fixtures.Response(contents[name])
+
+        return open_url
+
+    def file_url(self, content):
+        return BASE_URL + hashlib.sha1(content).hexdigest()
+
+    def prepare(self, revision=5354, contents=None):
+        manifest, contents = self.release(revision, contents)
+        calls = []
+        with patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents, calls)):
+            result = self.agent.prepare_plutonium({"revision": revision})
+        return manifest, contents, calls, result
+
+    def cache_content(self):
+        root = self.agent.root / "agent" / "plutonium-cache"
+        pointer = json.loads((root / "current.json").read_text())
+        return root / pointer["key"] / "content"
+
+    def app(self, name="app"):
+        app = Path(self.temp.name) / name
+        app.mkdir(exist_ok=True)
+        return app
+
+    def assert_runtime(self, app, manifest, contents):
+        runtime = app / "runtime" / "plutonium"
+        self.assertEqual(json.loads((runtime / "cdn_info.json").read_text()), manifest)
+        for name, content in contents.items():
+            if name.startswith("launcher"):
+                self.assertFalse((runtime / name).exists())
+            else:
+                self.assertEqual((runtime / name).read_bytes(), content)
+
+    def test_cold_preparation_verifies_downloads_and_reports_inventory(self):
+        self.assertIsNone(self.agent.plutonium_cache_inventory())
+        manifest, contents, calls, result = self.prepare()
+        expected_bytes = sum(len(content) for name, content in contents.items() if not name.startswith("launcher"))
+        self.assertEqual(result, {"revision": 5354, "bytes": expected_bytes})
+        self.assertEqual(self.agent.plutonium_cache_inventory(), result)
+        self.assertEqual(calls[0], module.PLUTONIUM_MANIFEST_URL)
+        self.assertEqual(set(calls[1:]), {self.file_url(content) for name, content in contents.items() if not name.startswith("launcher")})
+        self.assertEqual(json.loads((self.cache_content() / "cdn_info.json").read_text()), manifest)
+        self.assertEqual((self.agent.root / "agent" / "plutonium-cache").stat().st_mode & 0o077, 0)
+
+    def test_warm_preparation_only_fetches_manifest_and_dispatches(self):
+        manifest, contents, _, first = self.prepare()
+        calls = []
+        with patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents, calls)):
+            result = self.agent.dispatch({"kind": "plutonium.prepare", "payload": {"revision": 5354}})
+        self.assertEqual(result, first)
+        self.assertEqual(calls, [module.PLUTONIUM_MANIFEST_URL])
+
+    def test_refresh_downloads_changed_files_and_reuses_verified_unchanged_files(self):
+        _, contents, _, _ = self.prepare()
+        changed = {**contents, "bin/plutonium.dll": b"new-runtime", "storage/t6/new.ff": b"new-zone"}
+        manifest, changed, calls, result = self.prepare(5355, changed)
+        self.assertEqual(result["revision"], 5355)
+        self.assertEqual(set(calls[1:]), {self.file_url(changed["bin/plutonium.dll"]), self.file_url(changed["storage/t6/new.ff"])})
+        app = self.app()
+        self.assertTrue(self.agent.seed_plutonium(app, IMAGE))
+        self.assert_runtime(app, manifest, changed)
+
+    def test_changed_manifest_is_refreshed_even_when_revision_number_is_unchanged(self):
+        _, contents, _, _ = self.prepare()
+        previous = self.cache_content()
+        manifest, changed, calls, result = self.prepare(5354, {**contents, "bin/plutonium.dll": b"corrected-runtime"})
+        self.assertEqual(result["revision"], 5354)
+        self.assertNotEqual(self.cache_content(), previous)
+        self.assertEqual(calls[1:], [self.file_url(changed["bin/plutonium.dll"])])
+        app = self.app()
+        self.assertTrue(self.agent.seed_plutonium(app, IMAGE))
+        self.assert_runtime(app, manifest, changed)
+
+    def test_failed_refresh_preserves_the_older_complete_cache(self):
+        manifest, contents, _, result = self.prepare()
+        previous = self.cache_content()
+        next_manifest, next_contents = self.release(5355, {**contents, "bin/plutonium.dll": b"new-runtime"})
+        next_contents["bin/plutonium.dll"] = b"bad-runtime"
+        with patch.object(self.agent, "plutonium_open", side_effect=self.opener(next_manifest, next_contents)):
+            with self.assertRaises(AgentError):
+                self.agent.prepare_plutonium({"revision": 5355})
+        self.assertEqual(self.cache_content(), previous)
+        self.assertEqual(self.agent.plutonium_cache_inventory(), result)
+        app = self.app()
+        self.assertTrue(self.agent.seed_plutonium(app, IMAGE))
+        self.assert_runtime(app, manifest, contents)
+
+    def test_interrupted_preparation_resumes_without_advertising_a_partial_cache(self):
+        manifest, contents = self.release()
+        open_url = self.opener(manifest, contents)
+
+        def interrupted_open(url):
+            if url == self.file_url(contents["bin/plutonium.dll"]):
+                raise urllib.error.URLError("simulated network interruption")
+            return open_url(url)
+
+        with patch.object(self.agent, "plutonium_open", side_effect=interrupted_open):
+            with self.assertRaises(AgentError):
+                self.agent.prepare_plutonium({})
+        self.assertIsNone(self.agent.plutonium_cache_inventory())
+        self.assertFalse((self.agent.root / "agent/plutonium-cache/current.json").exists())
+        _, _, calls, result = self.prepare()
+        self.assertNotIn(self.file_url(contents[BOOTSTRAPPER]), calls)
+        self.assertEqual(result["revision"], manifest["revision"])
+
+    def test_agent_restart_reconciles_preparation_instead_of_accepting_an_older_cache(self):
+        _, contents, _, _ = self.prepare()
+        operation = {"id": "prepare-new-release", "kind": "plutonium.prepare", "payload": {"revision": 5355}}
+        self.agent.journal.accept(operation)
+        self.agent.journal.update(operation["id"], "running")
+        self.agent.journal.close()
+        self.agent = fixtures.Agent(self.config, self.docker)
+        self.assertEqual(self.agent.journal.get(operation["id"])["state"], "unknown")
+        manifest, contents = self.release(5355, {**contents, "bin/plutonium.dll": b"new-runtime"})
+        calls = []
+        with patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents, calls)):
+            result = self.agent.execute(operation)
+        self.assertEqual(result["state"], "completed", result)
+        self.assertEqual(json.loads(result["result"])["revision"], 5355)
+        self.assertTrue(json.loads(result["result"])["reconciled"])
+        self.assertEqual(self.agent.plutonium_cache_inventory()["revision"], 5355)
+        self.assertEqual(calls, [module.PLUTONIUM_MANIFEST_URL, self.file_url(contents["bin/plutonium.dll"])])
+        with patch.object(self.agent, "plutonium_open", side_effect=AssertionError("Completed operation repeated")):
+            self.assertEqual(self.agent.execute(operation)["result"], result["result"])
+
+    def test_heartbeat_defers_preparation_only_for_explicit_true(self):
+        self.assertFalse(self.agent.defer_plutonium_preparation)
+        for response, expected in (
+            ({"deferPlutoniumPreparation": True}, True),
+            ({}, False),
+            ({"deferPlutoniumPreparation": False}, False),
+            ({"deferPlutoniumPreparation": 1}, False),
+            ({"deferPlutoniumPreparation": "true"}, False),
+            ({"deferPlutoniumPreparation": None}, False),
+        ):
+            self.agent.defer_plutonium_preparation = not expected
+            with self.subTest(response=response), patch.object(self.agent, "request", return_value=response), patch.object(self.agent, "inventory", return_value={}), patch.object(self.agent, "record_health"):
+                self.agent.heartbeat()
+            self.assertIs(self.agent.defer_plutonium_preparation, expected)
+
+    def assert_preparation_yields_and_resumes(self, *, restarted):
+        manifest, contents = self.release()
+        operation = {"id": "cooperative-prepare", "kind": "plutonium.prepare", "payload": {"revision": 5354}}
+        if restarted:
+            self.agent.journal.accept(operation)
+            self.agent.journal.update(operation["id"], "running")
+            self.agent.journal.close()
+            self.agent = fixtures.Agent(self.config, self.docker)
+            self.assertEqual(self.agent.journal.get(operation["id"])["state"], "unknown")
+        agent = self.agent
+        open_url = self.opener(manifest, contents)
+
+        class BusyResponse(fixtures.Response):
+            def read(self, size=-1):
+                chunk = super().read(size)
+                if chunk:
+                    agent.defer_plutonium_preparation = True
+                return chunk
+
+        def become_busy_during_download(url):
+            if url == self.file_url(contents["bin/plutonium.dll"]):
+                return BusyResponse(contents["bin/plutonium.dll"])
+            return open_url(url)
+
+        with patch.object(self.agent, "plutonium_open", side_effect=become_busy_during_download):
+            result = self.agent.execute(operation)
+        self.assertEqual(result["state"], "accepted", result)
+        self.assertIn("waiting for other host operations", json.loads(result["result"])["message"])
+        self.assertIsNone(self.agent.executing_id)
+        self.assertIsNone(self.agent.plutonium_cache_inventory())
+        self.assertTrue(self.agent.defer_plutonium_preparation)
+        # A yielded preparation must let other mutations finish before retrying.
+        self.create()
+        self.assertTrue(self.agent.inspect(fixtures.INSTANCE, 1)["running"])
+        self.agent.defer_plutonium_preparation = False
+        calls = []
+        with patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents, calls)):
+            result = self.agent.execute(operation)
+        self.assertEqual(result["state"], "completed", result)
+        self.assertEqual(result["id"], operation["id"])
+        self.assertNotIn(self.file_url(contents[BOOTSTRAPPER]), calls)
+        self.assertIn(self.file_url(contents["bin/plutonium.dll"]), calls)
+        self.assertEqual(self.agent.plutonium_cache_inventory()["revision"], 5354)
+
+    def test_busy_host_yields_mid_download_and_resumes_completed_files(self):
+        self.assert_preparation_yields_and_resumes(restarted=False)
+
+    def test_reconciled_preparation_yields_mid_download_and_resumes_same_operation(self):
+        self.assert_preparation_yields_and_resumes(restarted=True)
+
+    def test_resumption_removes_orphans_before_storage_check_and_publication(self):
+        manifest, contents = self.release()
+        raw = json.dumps(manifest).encode()
+        staging = self.agent.root / "agent/plutonium-cache" / (module.digest(raw) + ".partial/content")
+        bootstrapper = staging / BOOTSTRAPPER
+        bootstrapper.parent.mkdir(parents=True)
+        bootstrapper.write_bytes(contents[BOOTSTRAPPER])
+        orphans = [staging / ".download-abandoned", staging / "bin/.ec-abandoned", staging / "unlisted/extra.dat", staging / "cdn_info.json"]
+        for orphan in orphans:
+            orphan.parent.mkdir(parents=True, exist_ok=True)
+            orphan.write_bytes(b"orphaned bytes")
+        outside = Path(self.temp.name) / "outside-cache"
+        outside.mkdir()
+        (outside / "untouched").write_bytes(b"private outside bytes")
+        link = staging / "outside-link"
+        link.symlink_to(outside, target_is_directory=True)
+        original_disk_usage = module.shutil.disk_usage
+
+        def checked_storage(path):
+            for orphan in orphans:
+                self.assertFalse(orphan.exists(), "orphan must be removed before storage accounting")
+            self.assertFalse(link.is_symlink())
+            return original_disk_usage(path)
+
+        calls = []
+        with patch.object(module.shutil, "disk_usage", side_effect=checked_storage), patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents, calls)):
+            result = self.agent.prepare_plutonium({})
+        content = self.cache_content()
+        expected = {name for name in contents if not name.startswith("launcher")}
+        actual = {path.relative_to(content).as_posix() for path in content.rglob("*") if path.is_file()}
+        self.assertEqual(actual, expected | {"cdn_info.json"})
+        self.assertEqual(result["bytes"], sum(len(contents[name]) for name in expected))
+        self.assertEqual(sum(path.stat().st_size for path in content.rglob("*") if path.is_file()), result["bytes"] + len(raw))
+        self.assertNotIn(self.file_url(contents[BOOTSTRAPPER]), calls)
+        self.assertEqual((outside / "untouched").read_bytes(), b"private outside bytes")
+        app = self.app()
+        self.assertTrue(self.agent.seed_plutonium(app, IMAGE))
+        self.assert_runtime(app, manifest, contents)
+        self.assertFalse((app / "runtime/plutonium/unlisted/extra.dat").exists())
+
+    def test_public_downloads_reject_other_origins_and_never_send_host_credentials(self):
+        # Call the class method to bypass the fixture's default network blocker;
+        # the underlying opener is mocked, so no request reaches the network.
+        with patch.object(module.urllib.request, "build_opener") as build:
+            for url in (
+                "http://cdn.plutoniummod.com/updater/prod/info.json",
+                "https://attacker.example/updater/prod/info.json",
+                "https://cdn.plutoniummod.com.attacker.example/updater/prod/info.json",
+                "https://secret@cdn.plutoniummod.com/updater/prod/info.json",
+                "https://cdn.plutoniummod.com/updater/dev/info.json",
+            ):
+                with self.subTest(url=url), self.assertRaises(AgentError):
+                    fixtures.Agent.plutonium_open(self.agent, url)
+            build.assert_not_called()
+            fixtures.Agent.plutonium_open(self.agent, module.PLUTONIUM_MANIFEST_URL)
+            build.return_value.open.assert_called_once_with(module.PLUTONIUM_MANIFEST_URL, timeout=30)
+            handler = build.call_args.args[0]
+            for redirect in (module.PLUTONIUM_MANIFEST_URL, "https://attacker.example/collect"):
+                with self.subTest(redirect=redirect), self.assertRaises(AgentError):
+                    handler.redirect_request(None, None, 302, "Found", {}, redirect)
+
+    def test_rejects_revision_downgrade_and_invalid_preparation_arguments(self):
+        self.prepare()
+        manifest, contents = self.release(5353)
+        with patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents)):
+            with self.assertRaises(AgentError):
+                self.agent.prepare_plutonium({"revision": 5354})
+        for payload in ({"revision": -1}, {"revision": True}, {"revision": "5354"},
+                        {"minimumFreeBytes": -1}, {"minimumFreeBytes": True}, {"minimumFreeBytes": "10"}):
+            with self.subTest(payload=payload), self.assertRaises(AgentError):
+                self.agent.prepare_plutonium(payload)
+
+    def test_disk_reserve_failure_leaves_existing_cache_usable(self):
+        _, contents, _, result = self.prepare()
+        manifest, contents = self.release(5355, {**contents, "bin/plutonium.dll": b"new-runtime"})
+        calls = []
+        usage = type(module.shutil.disk_usage(self.agent.root))(10000, 9900, 100)
+        with patch.object(module.shutil, "disk_usage", return_value=usage), patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents, calls)):
+            with self.assertRaises(AgentError):
+                self.agent.prepare_plutonium({"minimumFreeBytes": 1000})
+        self.assertEqual(calls, [module.PLUTONIUM_MANIFEST_URL])
+        self.assertEqual(self.agent.plutonium_cache_inventory(), result)
+
+    def test_malformed_manifest_never_publishes_a_cache(self):
+        good, contents = self.release()
+        malformed = [
+            None, [], {},
+            {**good, "product": "other-product"},
+            {**good, "revision": 0},
+            {**good, "revision": True},
+            {**good, "revision": "5354"},
+            {**good, "baseUrl": "http://cdn.plutoniummod.com/updater/prod/"},
+            {**good, "baseUrl": "https://attacker.example/"},
+            {**good, "files": []},
+            {**good, "files": {}},
+            {**good, "files": good["files"][1:]},
+            {**good, "files": good["files"] + [good["files"][0]]},
+        ]
+        for manifest in malformed:
+            with self.subTest(manifest=manifest), patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents)):
+                with self.assertRaises(AgentError):
+                    self.agent.prepare_plutonium({})
+                self.assertIsNone(self.agent.plutonium_cache_inventory())
+
+    def test_manifest_rejects_unsafe_paths_sizes_and_hashes_before_downloading(self):
+        good, contents = self.release()
+        bad_entries = [
+            {"name": name} for name in (
+                ".", "../escape", "/absolute", "bin/../../escape", "bin//file", "bin/./file",
+                "bin\\file", "C:/escape", "bin/file\x00", "cdn_info.json",
+            )
+        ] + [
+            {"size": size} for size in (-1, True, "5", None)
+        ] + [
+            {"hash": value} for value in ("", "0" * 39, "z" * 40, None)
+        ]
+        for override in bad_entries:
+            manifest = copy.deepcopy(good)
+            manifest["files"][1].update(override)
+            calls = []
+            with self.subTest(override=override), patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, contents, calls)):
+                with self.assertRaises(AgentError):
+                    self.agent.prepare_plutonium({})
+                self.assertEqual(calls, [module.PLUTONIUM_MANIFEST_URL])
+                self.assertIsNone(self.agent.plutonium_cache_inventory())
+
+    def test_short_oversize_and_wrong_hash_downloads_are_not_published(self):
+        manifest, contents = self.release()
+        for body in (b"short", contents[BOOTSTRAPPER] + b"extra", b"X" * len(contents[BOOTSTRAPPER])):
+            with self.subTest(body=body), patch.object(self.agent, "plutonium_open", side_effect=self.opener(manifest, {**contents, BOOTSTRAPPER: body})):
+                with self.assertRaises(AgentError):
+                    self.agent.prepare_plutonium({})
+                self.assertIsNone(self.agent.plutonium_cache_inventory())
+
+    def test_seeds_are_private_and_preserve_existing_lobby_state(self):
+        manifest, contents, _, _ = self.prepare()
+        first, second = self.app("first"), self.app("second")
+        private = {
+            "configs/server.cfg": b"secret config",
+            "runtime/plutonium/plugins/private.dll": b"private plugin",
+            "runtime/plutonium/storage/t5/logs/games_mp.log": b"lobby log",
+        }
+        for name, body in private.items():
+            target = first / name
+            target.parent.mkdir(parents=True, exist_ok=True)
+            target.write_bytes(body)
+        self.assertTrue(self.agent.seed_plutonium(first, IMAGE))
+        self.assertTrue(self.agent.seed_plutonium(second, IMAGE))
+        self.assert_runtime(first, manifest, contents)
+        self.assert_runtime(second, manifest, contents)
+        for name, body in private.items():
+            self.assertEqual((first / name).read_bytes(), body)
+            self.assertFalse((second / name).exists())
+        first_file = first / "runtime/plutonium" / BOOTSTRAPPER
+        second_file = second / "runtime/plutonium" / BOOTSTRAPPER
+        cached_file = self.cache_content() / BOOTSTRAPPER
+        self.assertNotEqual(first_file.stat().st_ino, second_file.stat().st_ino)
+        self.assertNotEqual(first_file.stat().st_ino, cached_file.stat().st_ino)
+        first_file.write_bytes(b"container-updated")
+        self.assertEqual(second_file.read_bytes(), contents[BOOTSTRAPPER])
+        self.assertEqual(cached_file.read_bytes(), contents[BOOTSTRAPPER])
+
+    def test_absent_or_corrupt_cache_and_unsupported_image_fall_back(self):
+        app = self.app()
+        self.assertFalse(self.agent.seed_plutonium(app, IMAGE))
+        self.assertFalse((app / "runtime/plutonium/cdn_info.json").exists())
+        self.prepare()
+        for image in ("example.invalid/plutainer:latest", "ghcr.io/ayymoss/plutainer-other:latest", "ghcr.io/attacker/plutainer:latest"):
+            with self.subTest(image=image):
+                self.assertFalse(self.agent.seed_plutonium(app, image))
+        (self.cache_content() / BOOTSTRAPPER).write_bytes(b"broken-cache")
+        self.assertFalse(self.agent.seed_plutonium(app, IMAGE))
+        self.assertFalse((app / "runtime/plutonium/cdn_info.json").exists())
+        self.assertIsNone(self.agent.plutonium_cache_inventory())
+
+    def test_interrupted_seed_does_not_install_revision_marker_and_can_retry(self):
+        manifest, contents, _, _ = self.prepare()
+        app = self.app()
+        marker = app / "runtime/plutonium/cdn_info.json"
+        marker.parent.mkdir(parents=True)
+        marker.write_text(json.dumps({"revision": 5353}))
+        copy_file = module.managed_copy
+        copied = []
+
+        def interrupted_copy(root, name, source, *args, **kwargs):
+            self.assertFalse(marker.exists(), "revision marker must be installed only after all files")
+            if copied:
+                raise OSError("simulated full disk")
+            copied.append(name)
+            return copy_file(root, name, source, *args, **kwargs)
+
+        with patch.object(module, "managed_copy", side_effect=interrupted_copy):
+            with self.assertRaises((AgentError, OSError)):
+                self.agent.seed_plutonium(app, IMAGE)
+        self.assertFalse(marker.exists())
+        self.assertTrue(copied)
+        self.assertTrue(self.agent.seed_plutonium(app, IMAGE))
+        self.assert_runtime(app, manifest, contents)
+
+    def test_failed_seed_prevents_container_start(self):
+        self.prepare()
+        with patch.object(module, "managed_copy", side_effect=OSError("simulated full disk")):
+            payload = {"game": "t5", "libraryId": self.library_id, "image": IMAGE, "port": 28960, "env": {}}
+            result = self.agent.execute(self.operation("instance.create", payload, "failed-seed"))
+        self.assertEqual(result["state"], "failed", result)
+        self.assertFalse(any(call[:2] == ("container", "start") for call in self.docker.calls))
+        self.assertFalse((self.agent.instance_dir(fixtures.INSTANCE, 1) / "app/runtime/plutonium/cdn_info.json").exists())
+
+    def test_symlink_in_cache_cannot_seed_outside_data(self):
+        _, contents, _, _ = self.prepare()
+        cached = self.cache_content() / BOOTSTRAPPER
+        outside = Path(self.temp.name) / "outside"
+        outside.write_bytes(contents[BOOTSTRAPPER])
+        cached.unlink()
+        cached.symlink_to(outside)
+        app = self.app()
+        self.assertFalse(self.agent.seed_plutonium(app, IMAGE))
+        self.assertFalse((app / "runtime/plutonium/cdn_info.json").exists())
+
+    def test_create_applies_initial_overlay_after_seed_and_starts_without_cache(self):
+        self.create()
+        self.assertTrue(self.agent.inspect(fixtures.INSTANCE, 1)["running"])
+        self.assertFalse((self.agent.instance_dir(fixtures.INSTANCE, 1) / "app/runtime/plutonium/cdn_info.json").exists())
+        manifest, contents, _, _ = self.prepare()
+        payload = self.agent.spec(fixtures.INSTANCE, 1)
+        payload["port"] += 1
+        payload["files"].append({"path": "runtime/plutonium/" + BOOTSTRAPPER, "contentBase64": base64.b64encode(b"custom-overlay").decode()})
+        other_id = "00000000-0000-4000-8000-000000000002"
+        result = self.agent.execute({**self.operation("instance.create", payload, "second-create"), "instanceId": other_id})
+        self.assertEqual(result["state"], "completed", result)
+        app = self.agent.instance_dir(other_id, 1) / "app"
+        self.assertEqual((app / "runtime/plutonium" / BOOTSTRAPPER).read_bytes(), b"custom-overlay")
+        self.assertEqual(json.loads((app / "runtime/plutonium/cdn_info.json").read_text()), manifest)
+        self.assertEqual((app / "configs/server.cfg").read_bytes(), b"original")
+
+    def test_rebuild_seeds_the_new_generation_from_current_cache(self):
+        payload = self.create()
+        manifest, contents, _, _ = self.prepare()
+        self.agent.rcon = lambda *_: {"ok": True, "players": 0}
+        result = self.agent.execute(self.operation("instance.rebuild", {**payload, "nextGeneration": 2}, "rebuild"))
+        self.assertEqual(result["state"], "completed", result)
+        self.assertTrue(self.agent.inspect(fixtures.INSTANCE, 2)["running"])
+        self.assert_runtime(self.agent.instance_dir(fixtures.INSTANCE, 2) / "app", manifest, contents)
+
+    def test_restart_preserves_the_instances_downloaded_runtime(self):
+        self.prepare()
+        self.create()
+        runtime_file = self.agent.instance_dir(fixtures.INSTANCE, 1) / "app/runtime/plutonium" / BOOTSTRAPPER
+        runtime_file.write_bytes(b"container-updated-runtime")
+        self.agent.rcon = lambda *_: {"ok": True, "players": 0}
+        with patch.object(self.agent, "seed_plutonium", side_effect=AssertionError("Restart must retain its runtime")):
+            result = self.agent.execute(self.operation("instance.restart", op_id="restart"))
+        self.assertEqual(result["state"], "completed", result)
+        self.assertEqual(runtime_file.read_bytes(), b"container-updated-runtime")
+
+
+if __name__ == "__main__":
+    unittest.main()

docs/guides/native-hosts.md

@@ -55,8 +55,10 @@ enrollment; inspect `systemctl status docker` and `journalctl -u docker`.
 The controller reconciles automatic setup on agent heartbeats. Command polls only
 deliver work already queued. Setup first pulls `PLUTAINER_IMAGE` (default
 `ghcr.io/ayymoss/plutainer:latest`), then prepares the latest verified upload for
-T5 and for T6 when available, one setup operation at a time. Uploading new files
+T5 and for T6 when available, one setup operation at a time. After those prerequisites,
-or enrolling another host needs no manual propagation. Setup waits for an active, connected,
+capable agents also prepare the optional Plutonium runtime cache described below.
+Uploading new files or enrolling another host needs no manual propagation.
+Setup waits for an active, connected,
 healthy host with sufficient storage. Failed operations retry automatically with
 backoff from one minute to fifteen minutes; their errors remain visible in the
 host's setup panel and **Hosts → Operation history**. This shared history lists
@@ -90,6 +92,50 @@ cached mutable image tag. Advanced controls on the
 host and game-file pages can explicitly pull a custom runtime, prepare an older
 upload or retry preparation immediately.
 
+### Plutonium runtime cache
+
+Agent 1.8.0 adds a host cache for the files Plutainer normally downloads from
+Plutonium on a new container's first start. This is separate from the cached
+Docker image and uploaded base game libraries. Automatic preparation warms it
+after the image and libraries are ready and refreshes it for new production
+revisions. The controller only queues this work for agents that advertise support.
+Cache preparation is optional: a missing or corrupt cache does not prevent a
+launch from using Plutainer's normal download path.
+
+Cache preparation has lower priority than deployments and other host changes.
+If work arrives during a download, the next heartbeat tells the agent to yield
+between transfer steps. Preparation resumes under the same operation ID after
+that work finishes, reusing files that have already passed verification.
+
+The agent downloads the official production manifest and its listed vendor files,
+verifies the SHA-1 hashes published in that manifest, and makes a snapshot
+available only after the complete set passes verification. It keeps the cache
+under `agent/plutonium-cache` within the host data directory. It does not populate
+the cache from existing lobbies, so lobby configuration, keys, custom scripts,
+plugins and runtime state are not collected into it. Preparation retains the
+current snapshot and the resumable download, removes older snapshots, and clears
+abandoned temporary files before checking available storage or publishing the
+new snapshot. A failed refresh preserves the previous complete cache.
+
+For new instances and rebuilds using `ghcr.io/ayymoss/plutainer` image references,
+the agent seeds `app/runtime/plutonium` from a valid snapshot, including its
+matching `cdn_info.json`, before applying the instance's launch files. Each
+instance receives its own writable copy; changes made by a lobby or its updater
+cannot change the host cache or another lobby. Custom runtime images keep their
+existing startup behavior.
+
+Plutainer's updater remains enabled. When a cached revision is current, it can
+skip the initial vendor-file download; when production is newer, it can download
+the update normally. Launch readiness still verifies the running Plutonium
+revision against production. Refreshing the cache does not restart or update
+running lobbies. Ordinary restarts retain the instance's existing files and do
+not need to seed from the cache again.
+
+Deleting a lobby preserves the host cache for subsequent launches. Deleting the
+host removes it with the rest of the managed data directory. This is intended to
+reduce repeated first-start downloads; deployment-time improvements still need
+measurement on a real Debian/Docker/Plutonium host.
+
 ### Storage layout
 
 The default host root is `/var/lib/electric-cherry`; installer `--data-dir` changes
@@ -698,6 +744,15 @@ game hosts. Run:
   loss and host reboot during update. Verify updater protocol mismatch requests
   an installer rerun.
 - T5 and T6 deployments and a mixed collection from a fresh destination host.
+- Warm the Plutonium runtime cache, then create and rebuild T5 and T6 lobbies;
+  verify the running revision and compare first-start downloads and launch times
+  with an empty cache. Test missing, corrupt and interrupted cache preparation,
+  a newer production revision, and a custom runtime image. Confirm launch-file
+  overrides survive seeding, lobby writes cannot alter the cache or another lobby,
+  and cache refresh leaves running lobbies unchanged. Queue a deployment during
+  preparation and verify that downloading yields and later resumes. Interrupt
+  preparation by stopping the agent and verify that retry removes abandoned
+  temporary files while retaining completed downloads.
 - Start, stop, restart, rebuild, destroy; verify RCON, map and runtime revision.
 - Read console and game logs, including Plutainer's relative game-log links.
 - File campaign and rollback, with a player joining between controller check and

src/lib/hosts.ts

@@ -82,6 +82,7 @@ export interface HostInventory {
     directoriesWritable?: boolean; runtimeImages?: string[]; libraries?: HostLibrary[];
     currentOperation?: string | null; [key: string]: unknown;
     capabilities?: string[];
+    plutoniumCache?: { revision: number; bytes: number };
     agentUpdate?: HostAgentUpdate;
     agentLanes?: HostAgentLane[];
     instanceResources?: InstanceResources[];
@@ -146,7 +147,7 @@ export interface HostOperationHistoryPage {
 }
 
 export interface HostPreparationItem {
-    kind: 'runtime' | 'library'; label: string;
+    kind: 'runtime' | 'library' | 'plutonium'; label: string;
     state: 'waiting' | 'preparing' | 'ready' | 'blocked'; detail: string;
     operationId?: string; bytesDownloaded?: number; bytesTotal?: number;
     cache?: HostLibraryCache;

src/lib/server/hosts/index.ts

@@ -277,6 +277,12 @@ export function validateInventory(value: unknown): HostInventory {
     for (const key of ['dockerRunning','directoriesWritable']) if (inventory[key] !== undefined && typeof inventory[key] !== 'boolean') throw new Error(`Invalid inventory ${key}.`);
     if (inventory.runtimeImages !== undefined && (!Array.isArray(inventory.runtimeImages) || inventory.runtimeImages.some(image => typeof image !== 'string'))) throw new Error('Invalid runtime image inventory.');
     if (inventory.capabilities !== undefined && (!Array.isArray(inventory.capabilities) || inventory.capabilities.length > 32 || inventory.capabilities.some(value => typeof value !== 'string' || value.length > 80))) throw new Error('Invalid agent capability inventory.');
+    if (inventory.plutoniumCache !== undefined) {
+        const cache = inventory.plutoniumCache;
+        if (!cache || typeof cache !== 'object' || Array.isArray(cache) || !Number.isSafeInteger(cache.revision) || cache.revision < 1
+            || !Number.isSafeInteger(cache.bytes) || cache.bytes < 0) throw new Error('Invalid Plutonium cache inventory.');
+        inventory.plutoniumCache = { revision: cache.revision, bytes: cache.bytes };
+    }
     if (inventory.agentUpdate !== undefined) {
         const update = inventory.agentUpdate;
         const version = (value: unknown) => typeof value === 'string' && value.length <= 80 && /^\d+\.\d+\.\d+$/.test(value);
@@ -396,6 +402,14 @@ export type OperationDeliveryRow = Omit<OperationRow, 'payload'>;
 export type HostOperationStatus = Omit<HostOperation, 'payload'>;
 const operationStatusColumns = 'o.id,o.host_id,o.kind,o.instance_id,o.generation,o.state,o.result,o.error,o.created_at,o.updated_at';
 const operationPayloadSql = 'COALESCE((SELECT p.payload FROM ec_host_operation_payloads p WHERE p.operation_id=o.id),o.payload)';
+const readOnlyOperationSql = `(o.kind IN ('host.inspect','instance.inspect','rcon.status-batch','files.read','files.list','files.stat','files.manifest','logs.read')
+    OR (o.kind='rcon.execute' AND COALESCE(json_extract(${operationPayloadSql},'$.command') IN ('status','getstatus','version'),0)))`;
+/** Optional cache downloads yield their write lane to deployments and host changes. */
+export function shouldDeferPlutoniumPreparation(hostId: string): boolean {
+    return !!database().prepare(`SELECT 1 FROM ec_host_operations o WHERE o.host_id=?
+        AND o.state IN ('pending','accepted','running','unknown') AND o.kind!='plutonium.prepare'
+        AND NOT ${readOnlyOperationSql} LIMIT 1`).get(hostId);
+}
 function operationStatusFromRow(row: Omit<OperationRow, 'payload'>): HostOperationStatus { return { id: row.id, hostId: row.host_id, kind: row.kind, instanceId: row.instance_id, generation: row.generation, state: row.state, result: row.result === null ? null : JSON.parse(row.result), error: row.error, createdAt: row.created_at, updatedAt: row.updated_at }; }
 function operationFromRow(row: OperationRow): HostOperation { const status = operationStatusFromRow(row); return { ...status, result: unpackFileJson(status.result), payload: unpackFileJson(JSON.parse(row.payload)) }; }
 export function getHostOperation(id: string): HostOperation | null {
@@ -483,7 +497,7 @@ function enqueueHostOperation(hostId: string, kind: string, payload: string | Bu
             }
         }
         if (['instance.create','create'].includes(kind)) requireReadyHost(hostId);
-        if (host.mode === 'disabled' && kind !== 'instance.cancel-create' && !(host.enablingSince && ['runtime.pull','library.download','host.inspect'].includes(kind))) throw new Error('Host is disabled. Enable it before requesting operations.');
+        if (host.mode === 'disabled' && kind !== 'instance.cancel-create' && !(host.enablingSince && ['runtime.pull','library.download','plutonium.prepare','host.inspect'].includes(kind))) throw new Error('Host is disabled. Enable it before requesting operations.');
         const requestHash = createHash('sha256').update(payload).digest('hex');
         const packed = packFileJson(JSON.parse(payload.toString()));
         payload = JSON.stringify(packed.value);
@@ -523,12 +537,10 @@ export function pendingHostOperationRows(hostId: string, lane: OperationLane = '
         WHERE host_id=? AND kind='instance.cancel-create' AND state IN ('pending','accepted','running','unknown') LIMIT 1`).get(hostId)) return [];
     // Accepted/running/unknown commands keep the same immutable ID. The agent
     // consults its durable journal before acknowledging or executing a replay.
-    const readOnly = `(kind IN ('host.inspect','instance.inspect','rcon.status-batch','files.read','files.list','files.stat','files.manifest','logs.read')
-        OR (kind='rcon.execute' AND json_extract(${operationPayloadSql},'$.command') IN ('status','getstatus','version')))`;
     const healthOnly = `(kind IN ('instance.inspect','rcon.status-batch') OR (kind='rcon.execute' AND json_extract(${operationPayloadSql},'$.command') IN ('status','getstatus','version')))`;
     const healthLane = host.inventory.capabilities?.includes('operations.health-lane');
     const laneFilter = lane === 'all' ? '' : lane === 'health' ? ` AND ${healthOnly}`
-        : ` AND ${lane === 'write' ? 'NOT ' : ''}${readOnly}${lane === 'read' && healthLane ? ` AND NOT ${healthOnly}` : ''}`;
+        : ` AND ${lane === 'write' ? 'NOT ' : ''}${readOnlyOperationSql}${lane === 'read' && healthLane ? ` AND NOT ${healthOnly}` : ''}`;
     // Health never queues behind a delivered file batch. Keep background reads
     // in small batches to amortize delivery without handing out a long backlog.
     const limit = healthLane ? lane === 'health' ? 1 : lane === 'read' ? 4 : 25 : 25;
@@ -536,13 +548,14 @@ export function pendingHostOperationRows(hostId: string, lane: OperationLane = '
         const columns = includePayload ? `${operationStatusColumns},${operationPayloadSql} AS payload` : operationStatusColumns;
         const rows = database().prepare(`SELECT ${columns} FROM ec_host_operations o WHERE host_id=? AND state IN ('pending','accepted','running','unknown')
             ${laneFilter}
-            ${host.mode === 'disabled' ? "AND kind IN ('runtime.pull','library.download','host.inspect')" : ''}
+            ${host.mode === 'disabled' ? "AND kind IN ('runtime.pull','library.download','plutonium.prepare','host.inspect')" : ''}
             AND (? OR state != 'pending' OR kind NOT IN ('instance.create','create'))
             AND (kind!='instance.cancel-create' OR ?)
             AND NOT EXISTS (SELECT 1 FROM ec_host_operations cancellation WHERE cancellation.host_id=o.host_id
                 AND cancellation.kind='instance.cancel-create' AND json_extract(cancellation.payload,'$.createOperationId')=o.id)
             ${lane === 'health' ? "AND (state NOT IN ('accepted','running') OR MAX(updated_at,COALESCE(last_delivered_at,'')) <= ?)" : ''}
-            ORDER BY CASE WHEN kind='instance.cancel-create' THEN 0 ELSE 1 END,COALESCE(last_delivered_at,''),created_at,rowid LIMIT ${limit}`)
+            ORDER BY CASE WHEN kind='instance.cancel-create' THEN 0 WHEN kind='plutonium.prepare' THEN 2 ELSE 1 END,
+                COALESCE(last_delivered_at,''),created_at,rowid LIMIT ${limit}`)
             // A short replay lease avoids handing the idle health lane its busy
             // sibling's work, but still recovers a lost receipt or agent restart.
             .all(hostId, Number(host.readiness === 'ready' || host.mode === 'draining'), Number(host.inventory.capabilities?.includes('instance.cancel-create') ?? false),

src/lib/server/hosts/observations.ts

@@ -35,6 +35,10 @@ export const importantOperationSql = `(o.routine=0 OR o.state IN ('failed','unkn
 const payloadSql = 'COALESCE((SELECT p.payload FROM ec_host_operation_payloads p WHERE p.operation_id=o.id),o.payload)';
 /** Deliberately exclude arbitrary RCON commands and all file contents/credentials. */
 export const operationTargetSql = `CASE
+    WHEN o.kind='plutonium.prepare' THEN CASE
+        WHEN json_type(${payloadSql},'$.revision')='integer' AND json_extract(${payloadSql},'$.revision')>0
+            THEN 'Production revision r' || json_extract(${payloadSql},'$.revision')
+        ELSE 'Latest production revision' END
     WHEN o.kind IN ('files.read','files.stat','files.list','logs.read') THEN
         CASE WHEN json_type(${payloadSql},'$.path')='text' THEN substr(json_extract(${payloadSql},'$.path'),1,1024) END
     WHEN o.kind='files.manifest' THEN substr((SELECT group_concat(value,', ') FROM json_each(${payloadSql},'$.roots') WHERE type='text'),1,1024)

src/lib/server/hosts/preparation.ts

@@ -1,15 +1,17 @@
 import { db } from '../db/index.js';
 import { config } from '../config.js';
-import { AGENT_PROTOCOL_VERSION, getHost, queueHostOperation } from './index.js';
+import { AGENT_PROTOCOL_VERSION, getHost, queueHostOperation, shouldDeferPlutoniumPreparation } from './index.js';
 import { getHostLibraryCache, latestPublishedLibraries, queueLibraryDownload } from '../game-files/index.js';
 import { GAME_FILE_GAMES } from '../../game-files.js';
 import type { Host, HostOperationState, HostPreparation, HostPreparationItem } from '../../hosts.js';
 import { scheduleAvailabilityRefresh } from './availability.js';
+import { readSetting } from '../maintenance/settings.js';
+import type { PlutoniumRelease } from '../../plutonium.js';
 
 const activeStates = ['pending', 'accepted', 'running', 'unknown'];
 const supersededDownload = 'Superseded by newer game files before delivery to the host.';
 type PreparationOperation = { id: string; sequence: number; last_delivered_at: string | null; state: HostOperationState; updated_at: string; error: string | null };
-type Target = { item: HostPreparationItem; image?: string; versionId?: string; requiredBytes: number; operation?: PreparationOperation };
+type Target = { item: HostPreparationItem; image?: string; versionId?: string; revision?: number; requiredBytes: number; operation?: PreparationOperation };
 type QueuedSelection = { libraryId: string };
 type LibraryTarget = Pick<ReturnType<typeof latestPublishedLibraries>[number], 'id' | 'sizeBytes' | 'manifestSha256'> & { name: string; queued?: boolean };
 
@@ -48,25 +50,27 @@ function targetLibraries(selections: QueuedSelection[]): LibraryTarget[] {
     return [...queued.values(), ...latest];
 }
 
-function latestOperation(hostId: string, kind: string, field: string, value: string): PreparationOperation | undefined {
+function latestOperation(hostId: string, kind: string, field?: string, value?: string): PreparationOperation | undefined {
     return db().prepare(`SELECT id,rowid AS sequence,last_delivered_at,state,updated_at,error FROM ec_host_operations
-        WHERE host_id=? AND kind=? AND json_extract(payload,?)=? ORDER BY created_at DESC,rowid DESC LIMIT 1`)
+        WHERE host_id=? AND kind=? ${field ? 'AND json_extract(payload,?)=?' : ''} ORDER BY created_at DESC,rowid DESC LIMIT 1`)
-        .get(hostId, kind, `$.${field}`, value) as PreparationOperation | undefined;
+        .get(hostId, kind, ...(field ? [`$.${field}`, value!] : [])) as PreparationOperation | undefined;
 }
 
 function retryAt(hostId: string, target: Target): number {
     const operation = target.operation;
     if (!operation || operation.state !== 'failed') return 0;
-    const kind = target.image ? 'runtime.pull' : 'library.download';
+    const kind = target.image ? 'runtime.pull' : target.versionId ? 'library.download' : 'plutonium.prepare';
-    const field = target.image ? '$.image' : '$.libraryVersionId';
+    const field = target.image ? '$.image' : target.versionId ? '$.libraryVersionId' : null;
-    const value = target.image ?? target.versionId!;
+    const value = target.image ?? target.versionId;
+    const match = field ? 'AND json_extract(payload,?)=?' : '';
+    const bindings = [hostId, kind, ...(field ? [field, value!] : [])];
     // Count consecutive failures, including across controller restarts. Unknown
     // operations are never retried under a new ID: their journal must reconcile.
     const { count } = db().prepare(`SELECT COUNT(*) AS count FROM ec_host_operations
-        WHERE host_id=? AND kind=? AND json_extract(payload,?)=? AND state='failed'
+        WHERE host_id=? AND kind=? ${match} AND state='failed'
         AND rowid>COALESCE((SELECT MAX(rowid) FROM ec_host_operations
-            WHERE host_id=? AND kind=? AND json_extract(payload,?)=? AND state='completed'),0)`)
+            WHERE host_id=? AND kind=? ${match} AND state='completed'),0)`)
-        .get(hostId, kind, field, value, hostId, kind, field, value) as { count: number };
+        .get(...bindings, ...bindings) as { count: number };
     return Date.parse(operation.updated_at) + Math.min(15 * 60_000, 60_000 * 2 ** Math.min(4, Math.max(0, count - 1)));
 }
 
@@ -108,6 +112,22 @@ function targets(host: Host): Target[] {
                     : ready ? 'The latest game files are downloaded and verified.' : 'The latest game files will be downloaded and verified automatically.',
                 bytesDownloaded: cache?.bytesDownloaded ?? 0, bytesTotal: version.sizeBytes, ...(cache ? { cache } : {}) } });
     }
+    if (host.inventory.capabilities?.includes('plutonium.cache')) {
+        // Read the same production release evidence as freshRelease without
+        // importing its fleet/provisioning observers into host preparation.
+        const release = readSetting<PlutoniumRelease>('plutonium_release', { revision: null, checkedAt: null, error: null });
+        const age = release.checkedAt ? Date.now() - Date.parse(release.checkedAt) : NaN;
+        const revision = !release.error && age >= 0 && age < 60 * 60_000
+            && Number.isSafeInteger(release.revision) && release.revision! > 0 ? release.revision! : 0;
+        const cache = host.inventory.plutoniumCache;
+        const ready = !!cache && cache.revision >= revision;
+        result.push({ revision, requiredBytes: host.minimumFreeBytes,
+            operation: latestOperation(host.id, 'plutonium.prepare'),
+            item: { kind: 'plutonium', label: 'Plutonium cache (optional)', state: ready ? 'ready' : 'waiting',
+                detail: ready ? `Production revision r${cache.revision} is cached for new deployments.`
+                    : cache ? `Production revision r${revision} will replace cached r${cache.revision} automatically.`
+                        : 'Plutonium files will be cached after the runtime and game files are ready.' } });
+    }
     const blocker = hostBlocker(host);
     for (const target of result) {
         if (target.item.state === 'ready') continue;
@@ -116,14 +136,15 @@ function targets(host: Host): Target[] {
         if (blocker) { Object.assign(target.item, blocker); continue; }
         if (operation && activeStates.includes(operation.state)) {
             target.item.state = 'preparing';
-            target.item.detail = !target.image && operation.state === 'pending' && !operation.last_delivered_at
+            target.item.detail = target.versionId && operation.state === 'pending' && !operation.last_delivered_at
                 ? 'Queued for game-file preparation; waiting for agent delivery or fleet preparation capacity.'
                 : operation.state === 'unknown' ? 'Waiting for the agent to reconcile interrupted preparation.'
                 : target.image ? 'Downloading the runtime automatically.'
+                : target.revision !== undefined ? 'Downloading and verifying the optional Plutonium cache.'
                 : target.item.cache?.status === 'verifying' ? 'Download complete. Verifying all game files.' : 'Downloading game files. Verification starts after all files arrive.';
         } else if (operation && Date.parse(host.lastHeartbeat!) <= Date.parse(operation.updated_at)) {
             target.item.state = 'preparing'; target.item.detail = 'Waiting for a fresh host inventory after preparation.';
-        } else if ((!enabling || (operation?.sequence ?? 0) > enabling.operation_floor) && retryAt(host.id, target) > Date.now()) {
+        } else if ((target.revision !== undefined || !enabling || (operation?.sequence ?? 0) > enabling.operation_floor) && retryAt(host.id, target) > Date.now()) {
             target.item.state = 'blocked';
             target.item.detail = `${operation?.error ?? 'Preparation failed.'} Automatic retry after ${new Date(retryAt(host.id, target)).toISOString()}.`;
         } else if (Number(host.inventory.storageAvailable ?? 0) < target.requiredBytes) {
@@ -142,16 +163,19 @@ export function hostPreparationStatus(host: Host): HostPreparation {
         }
     } else if (!items.some(item => item.kind === 'library')) items.push({ kind: 'library', label: 'Game files', state: 'waiting',
         detail: 'Upload T5 or T6 game files; hosts download the latest available files automatically.' });
-    const state = items.some(item => item.state === 'blocked') ? 'blocked'
+    // Cache health is visible, but never makes a usable host ineligible or
-        : items.some(item => item.state === 'preparing') ? 'preparing'
+    // delays re-enabling: a lobby's normal updater handles cache misses.
-        : items.some(item => item.state === 'waiting') ? 'waiting' : 'ready';
+    const required = items.filter(item => item.kind !== 'plutonium');
+    const state = required.some(item => item.state === 'blocked') ? 'blocked'
+        : required.some(item => item.state === 'preparing') ? 'preparing'
+        : required.some(item => item.state === 'waiting') ? 'waiting' : 'ready';
     return { state, items };
 }
 
 export function presentHostPreparation(host: Host): Host {
     const preparation = hostPreparationStatus(host);
     if (['needs-runtime', 'needs-game-files'].includes(host.readiness) && preparation.state === 'preparing') {
-        return { ...host, readiness: 'preparing', readinessReasons: preparation.items.filter(item => item.state !== 'ready').map(item => item.detail), preparation };
+        return { ...host, readiness: 'preparing', readinessReasons: preparation.items.filter(item => item.kind !== 'plutonium' && item.state !== 'ready').map(item => item.detail), preparation };
     }
     return { ...host, preparation };
 }
@@ -180,20 +204,26 @@ export function reconcileHostPreparation(hostId: string): HostPreparation {
         if (!host) throw new Error('Host was not found.');
         if (!hostBlocker(host)) {
             supersedeUndeliveredDownloads(hostId);
-            // Queue only one setup mutation at a time so each capacity check uses
+            // Queue one required setup mutation at a time with fresh disk
-            // fresh disk inventory. This also respects manually queued downloads.
+            // inventory. A running optional cache yields to required work via
+            // the heartbeat flag, then resumes under its original operation ID.
             const active = db().prepare(`SELECT 1 FROM ec_host_operations WHERE host_id=?
                 AND kind IN ('runtime.pull','library.download','library.import') AND state IN ('pending','accepted','running','unknown') LIMIT 1`).get(hostId);
             const finished = db().prepare(`SELECT updated_at FROM ec_host_operations WHERE host_id=?
-                AND kind IN ('runtime.pull','library.download','library.import') AND state IN ('completed','failed')
+                AND kind IN ('runtime.pull','library.download','library.import','plutonium.prepare') AND state IN ('completed','failed')
                 AND (error IS NULL OR error != ?)
                 ORDER BY updated_at DESC LIMIT 1`).get(hostId, supersededDownload) as { updated_at: string } | undefined;
             if (!active && (!finished || Date.parse(host.lastHeartbeat!) > Date.parse(finished.updated_at))) {
                 // A failed or oversized library must not prevent other libraries
                 // from preparing. The runtime still comes first when eligible.
-                const target = targets(host).find(target => target.item.state === 'waiting');
+                const candidates = targets(host);
+                const requiredReady = candidates.every(target => target.item.kind === 'plutonium' || target.item.state === 'ready');
+                const target = candidates.find(target => target.item.state === 'waiting' && (target.item.kind !== 'plutonium' || requiredReady));
                 if (target?.image) queueHostOperation(host.id, 'runtime.pull', { image: target.image });
                 else if (target?.versionId) queueLibraryDownload(host.id, target.versionId, { automatic: true });
+                else if (target?.revision !== undefined && !shouldDeferPlutoniumPreparation(host.id)) queueHostOperation(host.id, 'plutonium.prepare', {
+                    revision: target.revision, minimumFreeBytes: host.minimumFreeBytes, automatic: true
+                });
             }
         }
         const status = hostPreparationStatus(host);

src/lib/ui/components/HostPreparation.svelte

@@ -7,6 +7,7 @@
 
 <div class="preparation" aria-live="polite">
     <p>The default runtime and the latest available T5 and T6 game files are prepared automatically. Re-enabling a host requires a fresh runtime pull and verification of both BO1 (T5) and BO2 (T6) libraries before it accepts deployments. Running servers keep their current files.</p>
+    <p>Supported hosts also cache Plutonium files to speed up new deployments. This optional cache refreshes when a new production release is detected; deployments can proceed while it is unavailable.</p>
     {#if host.preparation}
         <p class="status" class:blocked={host.preparation.state === 'blocked'}>Automatic setup: {host.preparation.state === 'ready' ? 'Ready' : host.preparation.state === 'preparing' ? 'In progress' : host.preparation.state === 'blocked' ? 'Needs attention' : 'Waiting'}</p>
         <ul>

src/routes/api/agent/heartbeat/+server.ts

@@ -1,5 +1,5 @@
 import { json } from '@sveltejs/kit';
-import { heartbeat, pendingCreationCancellations } from '$lib/server/hosts/index.js';
+import { heartbeat, pendingCreationCancellations, shouldDeferPlutoniumPreparation } from '$lib/server/hosts/index.js';
 import { authenticateAgent, hostApiError, objectBody } from '$lib/server/hosts/http.js';
 import { reconcileHostPreparation } from '$lib/server/hosts/preparation.js';
 import { reconcileHostLibraryCleanup } from '$lib/server/game-files/index.js';
@@ -17,6 +17,7 @@ export async function POST({ request }: { request: Request }) {
         reconcileHostPreparation(host.id);
         reconcileHostLibraryCleanup(host.id);
         return json({ host, cancelledCreations: pendingCreationCancellations(host.id), heartbeatSeconds: 15,
+            deferPlutoniumPreparation: shouldDeferPlutoniumPreparation(host.id),
             observationKeepDays: fleetSettings().observationKeepDays, serverTime: new Date().toISOString() });
     } catch (cause) { return hostApiError(cause); }
 }

src/routes/hosts/operations/+page.svelte

@@ -90,7 +90,7 @@
                     <thead><tr><th scope="col">Operation</th><th scope="col">Host</th><th scope="col">Target</th><th scope="col">Source</th><th scope="col">State</th><th scope="col">Updated</th><th scope="col">Result</th></tr></thead>
                     <tbody>{#each history.operations as operation (operation.id)}
                         <tr>
-                            <td class="operation">{operation.kind}<small>{operation.id}</small></td>
+                            <td class="operation">{operation.kind === 'plutonium.prepare' ? 'Prepare Plutonium cache' : operation.kind}<small>{operation.id}</small></td>
                             <td>{#if operation.hostName !== null}<a href={contextHref(`/hosts/${operation.hostId}`, $page.url)}>{operation.hostName}</a>{:else}Deleted host<small>{operation.hostId}</small>{/if}</td>
                             <td class="target">
                                 <span>{operation.serverName ?? operation.instanceId ?? 'Host-level'}</span>

static/agent/ec-agent.py

@@ -33,7 +33,7 @@ import urllib.parse
 import urllib.request
 import uuid
 
-VERSION = "1.7.0"
+VERSION = "1.8.0"
 LABEL = "io.electric-cherry"
 MAX_FILE = 32 * 1024 * 1024
 MANIFEST_MAX_ENTRIES = 10000
@@ -42,6 +42,10 @@ MANIFEST_MAX_SECONDS = 15
 MANIFEST_MAX_DEPTH = 64
 LIBRARY_DOWNLOAD_WORKERS = 4
 HEALTH_LOCK_TIMEOUT_SECONDS = 5
+PLUTONIUM_MANIFEST_URL = "https://cdn.plutoniummod.com/updater/prod/info.json"
+PLUTONIUM_MANIFEST_LIMIT = 2 * 1024 * 1024
+PLUTONIUM_FILE_LIMIT = 512 * 1024 * 1024
+PLUTONIUM_CACHE_LIMIT = 4 * 1024 * 1024 * 1024
 ID_RE = re.compile(r"^[A-Za-z0-9][A-Za-z0-9_-]{0,127}$")
 AGENT_CONFIG = Path("/etc/electric-cherry/agent.json")
 AGENT_EXECUTABLE = Path("/usr/local/libexec/electric-cherry-agent.py")
@@ -487,6 +491,34 @@ def managed_write(root, value, content, uid=1000, gid=1000):
                 os.unlink(temp_name, dir_fd=parent)
 
 
+def managed_copy(root, value, source, uid=1000, gid=1000):
+    """Copy a private file, using Linux reflinks when supported, never hardlinks."""
+    with managed_open(Path(source).parent, Path(source).name) as incoming:
+        with managed_parent(root, value, create=True, uid=uid, gid=gid) as (parent, name):
+            temp_name = ".ec-" + uuid.uuid4().hex
+            fd = os.open(temp_name, os.O_WRONLY | os.O_CREAT | os.O_EXCL | os.O_NOFOLLOW, 0o600, dir_fd=parent)
+            try:
+                os.fchmod(fd, 0o644)
+                if os.geteuid() == 0:
+                    os.fchown(fd, uid, gid)
+                try:
+                    if not sys.platform.startswith("linux"):
+                        raise OSError("Reflinks unavailable")
+                    fcntl.ioctl(fd, 0x40049409, incoming.fileno())  # FICLONE
+                except OSError:
+                    os.ftruncate(fd, 0)
+                    with os.fdopen(fd, "wb", closefd=False) as outgoing:
+                        shutil.copyfileobj(incoming, outgoing, 1024 * 1024)
+                        outgoing.flush()
+                os.fsync(fd)
+                os.replace(temp_name, name, src_dir_fd=parent, dst_dir_fd=parent)
+                os.fsync(parent)
+            finally:
+                os.close(fd)
+                with contextlib.suppress(FileNotFoundError):
+                    os.unlink(temp_name, dir_fd=parent)
+
+
 class ReadWriteGate:
     """Let observations run together; global mutations wait for existing readers."""
     def __init__(self):
@@ -921,11 +953,13 @@ class Agent:
         self.read_claims = set()
         self.health_probe_gate = threading.BoundedSemaphore(2)
         self.cancelled_creations = frozenset()
+        self.defer_plutonium_preparation = False
         self.observation_keep_days = 0  # Older controllers do not authorize cleanup.
         self.library_progress = {}
         self.library_transfers = {}
         self.inventory_manifest_cache = {}
         self.inventory_manifest_lock = threading.Lock()
+        self.plutonium_lock = threading.RLock()
         self.config_path = config.get("configPath", "/etc/electric-cherry/agent.json")
         self.executing_id = None
         self.lane_lock = threading.Lock()
@@ -1360,8 +1394,9 @@ class Agent:
                 if line.startswith("PRETTY_NAME="):
                     os_name = line.split("=", 1)[1].strip('"')
         update = self.update_inventory()
-        capabilities = ["library.remove", "instance.cancel-create", "instance.safety-override", "instance.autoscaling-remove", "operations.read-lane", "operations.health-lane", "rcon.status-batch", "instance.heartbeat-state", "files.manifest", "files.blobs"] + (["host.decommission"] if self.can_uninstall() else []) + (["agent.update"] if update["enabled"] else [])
+        capabilities = ["library.remove", "plutonium.cache", "instance.cancel-create", "instance.safety-override", "instance.autoscaling-remove", "operations.read-lane", "operations.health-lane", "rcon.status-batch", "instance.heartbeat-state", "files.manifest", "files.blobs"] + (["host.decommission"] if self.can_uninstall() else []) + (["agent.update"] if update["enabled"] else [])
-        return {"hostname": socket.gethostname(), "agentVersion": VERSION, "protocolVersion": 1, "capabilities": capabilities, "agentUpdate": update, "agentLanes": self.lane_inventory(), "os": os_name, "osVersion": platform.release(), "architecture": platform.machine(), "cpu": platform.processor() or platform.machine(), "cpuCount": os.cpu_count() or 0, **resources, **({"cpuUsagePercent": cpu_usage} if cpu_usage is not None else {}), "memoryTotal": memory.get("MemTotal", 0), "memoryAvailable": memory.get("MemAvailable", 0), "storageTotal": usage.total, "storageAvailable": usage.free, "dockerVersion": docker_version, "dockerRunning": docker_running, "directoriesWritable": os.access(self.root, os.W_OK), "runtimeImages": sorted(set(images)), "libraries": libraries, "libraryCaches": caches, "currentOperation": self.current_operation, "portRange": self.config.get("portRange", {"min": 28960, "max": 29060})}
+        plutonium_cache = self.plutonium_cache_inventory()
+        return {"hostname": socket.gethostname(), "agentVersion": VERSION, "protocolVersion": 1, "capabilities": capabilities, "agentUpdate": update, "agentLanes": self.lane_inventory(), "os": os_name, "osVersion": platform.release(), "architecture": platform.machine(), "cpu": platform.processor() or platform.machine(), "cpuCount": os.cpu_count() or 0, **resources, **({"cpuUsagePercent": cpu_usage} if cpu_usage is not None else {}), "memoryTotal": memory.get("MemTotal", 0), "memoryAvailable": memory.get("MemAvailable", 0), "storageTotal": usage.total, "storageAvailable": usage.free, "dockerVersion": docker_version, "dockerRunning": docker_running, "directoriesWritable": os.access(self.root, os.W_OK), "runtimeImages": sorted(set(images)), **({"plutoniumCache": plutonium_cache} if plutonium_cache else {}), "libraries": libraries, "libraryCaches": caches, "currentOperation": self.current_operation, "portRange": self.config.get("portRange", {"min": 28960, "max": 29060})}
 
     def safe_to_disrupt(self, instance_id, generation):
         health = self.inspect(instance_id, generation)
@@ -1510,6 +1545,223 @@ class Agent:
                 raise Rejected("Initial files exceed the 64 MiB operation limit")
         return game, library, image, port, bind, env
 
+    @staticmethod
+    def plutonium_manifest(data):
+        """Validate the official updater format before using any paths or URLs."""
+        if len(data) > PLUTONIUM_MANIFEST_LIMIT:
+            raise AgentError("Plutonium manifest is too large")
+        try:
+            manifest = json.loads(data)
+        except (ValueError, UnicodeError):
+            raise AgentError("Invalid Plutonium manifest") from None
+        if not isinstance(manifest, dict) or manifest.get("product") != "plutonium-core-prod":
+            raise AgentError("Invalid Plutonium production manifest")
+        revision = manifest.get("revision")
+        if type(revision) is not int or not 1 <= revision <= 2147483647:
+            raise AgentError("Invalid Plutonium revision")
+        base = manifest.get("baseUrl")
+        if not isinstance(base, str) or not re.fullmatch(r"https://cdn\.plutoniummod\.com/updater/prod/(?:[A-Za-z0-9_-]+/)*", base):
+            raise AgentError("Plutonium downloads must use the official production CDN")
+        entries = manifest.get("files")
+        if not isinstance(entries, list) or not 1 <= len(entries) <= 4096:
+            raise AgentError("Invalid Plutonium file list")
+        names, total = set(), 0
+        for entry in entries:
+            if not isinstance(entry, dict):
+                raise AgentError("Invalid Plutonium file entry")
+            name, size, checksum = entry.get("name"), entry.get("size"), entry.get("hash")
+            if not isinstance(name, str) or len(name) > 512 or re.search(r'[\x00-\x1f\x7f\\:*?"<>|]', name):
+                raise AgentError("Invalid Plutonium file path")
+            path = PurePosixPath(name)
+            if not path.parts or path.is_absolute() or str(path) != name or any(part in (".", "..") or part.endswith((".", " ")) for part in path.parts) or name.lower() == "cdn_info.json":
+                raise AgentError("Invalid Plutonium file path")
+            if name.lower() in names:
+                raise AgentError("Duplicate Plutonium file path")
+            names.add(name.lower())
+            if type(size) is not int or not 0 <= size <= PLUTONIUM_FILE_LIMIT:
+                raise AgentError("Invalid Plutonium file size")
+            if not isinstance(checksum, str) or not re.fullmatch(r"[a-f0-9]{40}", checksum):
+                raise AgentError("Invalid Plutonium file hash")
+            total += size
+            if total > PLUTONIUM_CACHE_LIMIT:
+                raise AgentError("Plutonium cache exceeds the size limit")
+        for name in names:
+            if any(str(parent) in names for parent in PurePosixPath(name).parents if str(parent) != "."):
+                raise AgentError("Conflicting Plutonium file paths")
+        if "bin/plutonium-bootstrapper-win32.exe" not in {entry["name"] for entry in entries}:
+            raise AgentError("Plutonium manifest is missing the server bootstrapper")
+        # Match plutonium-updater's default: launcher assets are optional.
+        return manifest, [entry for entry in entries if not entry["name"].startswith("launcher")]
+
+    @staticmethod
+    def plutonium_file_matches(root, entry):
+        try:
+            with managed_open(root, entry["name"]) as stream:
+                if os.fstat(stream.fileno()).st_size != entry["size"]:
+                    return False
+                checksum = hashlib.sha1()
+                for chunk in iter(lambda: stream.read(1024 * 1024), b""):
+                    checksum.update(chunk)
+                return checksum.hexdigest() == entry["hash"]
+        except (OSError, AgentError):
+            return False
+
+    def plutonium_open(self, url):
+        if not isinstance(url, str) or not re.fullmatch(r"https://cdn\.plutoniummod\.com/updater/prod/[A-Za-z0-9_./-]+", url):
+            raise AgentError("Plutonium downloads must use the official production CDN")
+        class NoRedirect(urllib.request.HTTPRedirectHandler):
+            def redirect_request(self, req, fp, code, msg, hdrs, newurl):
+                raise AgentError("Plutonium download redirects are not allowed")
+        # Never send the controller's host credentials to the public CDN.
+        return urllib.request.build_opener(NoRedirect()).open(url, timeout=30)
+
+    def plutonium_snapshot(self):
+        root = scoped(self.root / "agent", "plutonium-cache")
+        pointer = json.loads(managed_read(root, "current.json") or b"null")
+        if not isinstance(pointer, dict) or not isinstance(pointer.get("key"), str) or not re.fullmatch(r"[a-f0-9]{64}", pointer["key"]):
+            raise AgentError("Plutonium cache is not prepared")
+        content = scoped(root, pointer["key"] + "/content")
+        raw = managed_read(content, "cdn_info.json")
+        if raw is None or digest(raw) != pointer["key"]:
+            raise AgentError("Plutonium cache manifest is invalid")
+        manifest, files = self.plutonium_manifest(raw)
+        if pointer.get("revision") != manifest["revision"] or pointer.get("bytes") != sum(entry["size"] for entry in files):
+            raise AgentError("Plutonium cache metadata is invalid")
+        # Heartbeat checks are cheap. Every file is hashed before it is seeded.
+        for entry in files:
+            info = scoped(content, entry["name"]).lstat()
+            if not stat_module.S_ISREG(info.st_mode) or info.st_size != entry["size"]:
+                raise AgentError("Plutonium cache files are incomplete")
+        return pointer, content, raw, files
+
+    def plutonium_cache_inventory(self):
+        with self.plutonium_lock:
+            try:
+                pointer, _, _, _ = self.plutonium_snapshot()
+                return {"revision": pointer["revision"], "bytes": pointer["bytes"]}
+            except (OSError, ValueError, AgentError):
+                return None
+
+    def prepare_plutonium(self, payload):
+        target, reserve = payload.get("revision", 0), payload.get("minimumFreeBytes", 0)
+        if type(target) is not int or not 0 <= target <= 2147483647 or type(reserve) is not int or reserve < 0:
+            raise Rejected("Invalid Plutonium preparation request")
+        root = scoped(self.root / "agent", "plutonium-cache")
+        root.mkdir(mode=0o700, exist_ok=True)
+        os.chmod(root, 0o700)
+        deadline = time.monotonic() + 1800
+        def active():
+            if self.stopping.is_set() or time.monotonic() >= deadline:
+                raise AgentError("Plutonium cache preparation was interrupted or timed out")
+            if self.defer_plutonium_preparation:
+                raise Held("Plutonium cache preparation is waiting for other host operations")
+        active()
+        try:
+            with self.plutonium_open(PLUTONIUM_MANIFEST_URL) as response:
+                raw = response.read(PLUTONIUM_MANIFEST_LIMIT + 1)
+            manifest, files = self.plutonium_manifest(raw)
+            if manifest["revision"] < target:
+                raise AgentError("Plutonium CDN has not reached the requested revision")
+            key = digest(raw)
+            previous = None
+            with self.plutonium_lock:
+                with contextlib.suppress(OSError, ValueError, AgentError):
+                    _, previous, _, _ = self.plutonium_snapshot()
+            if previous is not None and previous.parent.name == key and all(self.plutonium_file_matches(previous, entry) for entry in files):
+                return {"revision": manifest["revision"], "bytes": sum(entry["size"] for entry in files)}
+            staging = scoped(root, key + ".partial/content")
+            staging.mkdir(parents=True, exist_ok=True)
+            expected = {entry["name"] for entry in files}
+            # SIGKILL/power loss bypasses download/copy finally blocks. Remove
+            # abandoned temporary files before counting space or publishing.
+            for directory, subdirs, filenames in os.walk(staging, followlinks=False):
+                for name in subdirs + filenames:
+                    path = Path(directory) / name
+                    if path.is_symlink() or (name in filenames and path.relative_to(staging).as_posix() not in expected):
+                        path.unlink()
+            # Keep at most the current snapshot and this resumable preparation.
+            current_key = previous.parent.name if previous is not None else None
+            for directory in root.iterdir():
+                if re.fullmatch(r"[a-f0-9]{64}(?:\.partial)?", directory.name) and directory.name not in (current_key, key + ".partial"):
+                    if directory.is_symlink():
+                        directory.unlink()
+                    else:
+                        shutil.rmtree(directory)
+            missing = sum(entry["size"] for entry in files if not self.plutonium_file_matches(staging, entry))
+            if shutil.disk_usage(root).free < reserve + missing + len(raw):
+                raise AgentError("Insufficient free storage for the Plutonium cache and host reserve")
+            for entry in files:
+                active()
+                if self.plutonium_file_matches(staging, entry):
+                    continue
+                if previous is not None and self.plutonium_file_matches(previous, entry):
+                    managed_copy(staging, entry["name"], scoped(previous, entry["name"]), os.geteuid(), os.getegid())
+                    continue
+                destination = scoped(staging, entry["name"])
+                destination.parent.mkdir(parents=True, exist_ok=True)
+                temporary = destination.with_name(".download-" + uuid.uuid4().hex)
+                try:
+                    with self.plutonium_open(manifest["baseUrl"] + entry["hash"]) as incoming, temporary.open("xb") as outgoing:
+                        size, checksum = 0, hashlib.sha1()
+                        while True:
+                            active()
+                            chunk = incoming.read(min(1024 * 1024, entry["size"] - size + 1))
+                            if not chunk:
+                                break
+                            size += len(chunk)
+                            if size > entry["size"]:
+                                raise AgentError("Plutonium download exceeds its expected size")
+                            checksum.update(chunk)
+                            outgoing.write(chunk)
+                        if size != entry["size"] or checksum.hexdigest() != entry["hash"]:
+                            raise AgentError("Plutonium download failed size or checksum verification")
+                        outgoing.flush()
+                        os.fsync(outgoing.fileno())
+                    os.replace(temporary, destination)
+                    sync_parent(destination)
+                finally:
+                    with contextlib.suppress(FileNotFoundError):
+                        temporary.unlink()
+            # Publish metadata last. Interrupted transfers can never claim ready.
+            active()
+            atomic_bytes(staging / "cdn_info.json", raw)
+            pointer = {"key": key, "revision": manifest["revision"], "bytes": sum(entry["size"] for entry in files)}
+            with self.plutonium_lock:
+                final = scoped(root, key)
+                if final.exists():
+                    # Invalidate before replacing a damaged/same-revision cache.
+                    if current_key == key:
+                        (root / "current.json").unlink(missing_ok=True)
+                    shutil.rmtree(final)
+                os.replace(staging.parent, final)
+                sync_parent(final)
+                atomic_json(root / "current.json", pointer)
+                if previous is not None and current_key != key:
+                    shutil.rmtree(previous.parent)
+            return {"revision": pointer["revision"], "bytes": pointer["bytes"]}
+        except (urllib.error.URLError, TimeoutError, http.client.HTTPException):
+            raise AgentError("Plutonium CDN download is unavailable; the previous cache is retained") from None
+
+    def seed_plutonium(self, app, image):
+        if not re.fullmatch(r"ghcr\.io/ayymoss/plutainer(?::[A-Za-z0-9_.-]+)?(?:@sha256:[a-f0-9]{64})?", image):
+            return False
+        with self.plutonium_lock:
+            try:
+                _, content, raw, files = self.plutonium_snapshot()
+                if not all(self.plutonium_file_matches(content, entry) for entry in files):
+                    scoped(self.root / "agent", "plutonium-cache/current.json").unlink(missing_ok=True)
+                    raise AgentError("Plutonium cache checksum verification failed")
+            except (OSError, ValueError, AgentError):
+                return False
+            uid, gid = int(self.config.get("runtimeUid", 1000)), int(self.config.get("runtimeGid", 1000))
+            marker = "runtime/plutonium/cdn_info.json"
+            managed_write(app, marker, None, uid, gid)
+            for entry in files:
+                self.check_creation_cancellation()
+                managed_copy(app, "runtime/plutonium/" + entry["name"], scoped(content, entry["name"]), uid, gid)
+            managed_write(app, marker, raw, uid, gid)
+            return True
+
     def create(self, instance_id, generation, payload):
         self.check_creation_cancellation()
         directory = self.instance_dir(instance_id, generation)
@@ -1527,6 +1779,7 @@ class Agent:
         app = directory / "app"
         app.mkdir(parents=True, exist_ok=True)
         self.make_writable(app, directory=True)
+        self.seed_plutonium(app, image)
         self.write_initial_files(app, payload.get("files", []))
         atomic_json(directory / "spec.json", payload)
         env_path = directory / "environment"
@@ -2184,6 +2437,8 @@ class Agent:
             return {"image": image, "ready": True}
         if kind == "host.inspect":
             return self.inventory()
+        if kind == "plutonium.prepare":
+            return self.prepare_plutonium(payload)
         if kind == "rcon.status-batch":
             return self.rcon_status_batch(operation)
         if kind == "library.download":
@@ -2290,7 +2545,7 @@ class Agent:
                 if not self.config.get("pendingCredential") or self.recover_credential():
                     return self.journal.update(operation["id"], "completed", {"rotated": True, "reconciled": True})
                 return row
-            if kind == "runtime.pull":
+            if kind in ("runtime.pull", "plutonium.prepare"):
                 # Docker resumes already downloaded layers. Pull again under
                 # the same operation ID: an existing tag can still refer to an
                 # older image and cannot prove an interrupted pull completed.
@@ -2298,6 +2553,8 @@ class Agent:
                 try:
                     result = self.dispatch(operation)
                     return self.journal.update(operation["id"], "completed", {**result, "reconciled": True})
+                except Held as err:
+                    return self.journal.update(operation["id"], "accepted", {"blocked": "host-busy", "message": str(err)})
                 except Exception:
                     return self.journal.update(operation["id"], "failed", error="Interrupted runtime download could not be resumed")
             if kind == "library.import":
@@ -2407,6 +2664,7 @@ class Agent:
         # Only the heartbeat thread replaces this immutable snapshot; it never
         # mutates the operation journal or races Docker cleanup against create.
         self.cancelled_creations = frozenset(value for value in response.get("cancelledCreations", []) if isinstance(value, str))
+        self.defer_plutonium_preparation = response.get("deferPlutoniumPreparation") is True
         keep_days = response.get("observationKeepDays")
         self.observation_keep_days = keep_days if valid_observation_keep_days(keep_days) else 0
         host = response.get("host", {})

static/agent/manifest.json

@@ -1,8 +1,8 @@
 {
-  "version": "1.7.0",
+  "version": "1.8.0",
   "protocolVersion": 1,
   "platform": "debian-amd64",
-  "sha256": "4b40206f477dcf35f0506281b3dddca32b57214a964bcf5169c8611dc705132d",
+  "sha256": "eb36afb3113b92304da42fc78ac7f3b8218456f33c5bc1c0f57b018bbc2ad65d",
   "updaterProtocolVersion": 1,
   "updaterSha256": "066bb896726600ece9ce72697ce523c9a707cc9a621505931ba0892dec59d3c8"
 }

tests/unit/host-preparation.test.ts

@@ -47,7 +47,7 @@ function heartbeat(id: string, overrides: HostInventory = {}) {
 }
 
 function operations(id: string) {
-    return hosts.listHostOperations(id).filter(operation => ['runtime.pull', 'library.download'].includes(operation.kind));
+    return hosts.listHostOperations(id).filter(operation => ['runtime.pull', 'library.download', 'plutonium.prepare'].includes(operation.kind));
 }
 
 async function publish(game: 't5' | 't6' = 't5', bytes = content) {
@@ -85,10 +85,11 @@ describe('automatic host preparation', () => {
         } finally { cleanup.mockRestore(); }
     });
 
-    it('keeps re-enabled hosts disabled until a fresh runtime pull and both game libraries are verified', async () => {
+    it.each([false, true])('keeps re-enabled hosts disabled until required files are verified, without waiting for the optional cache (supported: %s)', async supported => {
         const t5 = await publish('t5');
         const t6 = await publish('t6');
-        const readyInventory = { runtimeImages: [runtime], libraries: [t5, t6].map(version => ({ id: version.id, state: 'ready' as const })) };
+        const readyInventory = { runtimeImages: [runtime], libraries: [t5, t6].map(version => ({ id: version.id, state: 'ready' as const })),
+            capabilities: [...inventory.capabilities!, ...(supported ? ['plutonium.cache'] : [])] };
         const id = enroll(readyInventory);
         verified(id, t5); verified(id, t6);
         const oldRuntime = hosts.queueHostOperation(id, 'runtime.pull', { image: runtime });
@@ -126,6 +127,7 @@ describe('automatic host preparation', () => {
         preparation.reconcileHostPreparation(id);
         expect(hosts.getHost(id)).toMatchObject({ mode: 'active', readiness: 'ready', enablingSince: null });
         expect(operations(id).filter(operation => operation.kind === 'library.download')).toHaveLength(2);
+        expect(operations(id).filter(operation => operation.kind === 'plutonium.prepare')).toHaveLength(supported ? 1 : 0);
     });
 
     it('requires both games when enabling even if one library is already cached', async () => {
@@ -551,3 +553,247 @@ describe('automatic host preparation', () => {
         expect(libraries.getHostLibraryCache(id, version.id)?.bytesDownloaded).toBe(80);
     });
 });
+
+describe('optional host Plutonium cache', () => {
+    const capable = { capabilities: ['host.decommission', 'plutonium.cache'] };
+    async function release(revision: number, overrides: { checkedAt?: string; error?: string | null } = {}) {
+        const { writeSetting } = await import('../../src/lib/server/maintenance/settings.js');
+        writeSetting('plutonium_release', { revision, checkedAt: new Date().toISOString(), error: null, ...overrides });
+    }
+
+    it.each(['pending', 'accepted', 'running', 'unknown'] as const)('waits to warm while a deployment is %s', state => {
+        const ready = { ...capable, runtimeImages: [runtime], libraries: [{ id: 'game-files', state: 'ready' as const }] };
+        const id = enroll(ready);
+        const deployment = hosts.queueHostOperation(id, 'instance.create', {});
+        if (state !== 'pending') hosts.reportHostOperation(id, deployment.id, { state });
+        preparation.reconcileHostPreparation(id);
+        expect(hosts.shouldDeferPlutoniumPreparation(id)).toBe(true);
+        expect(operations(id)).toEqual([]);
+        hosts.reportHostOperation(id, deployment.id, { state: 'completed' });
+        heartbeat(id, ready);
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toMatchObject([{ kind: 'plutonium.prepare' }]);
+    });
+
+    it('delivers newer deployments before queued cache work and before a cache replay', () => {
+        const id = enroll({ ...capable, runtimeImages: [runtime], libraries: [{ id: 'game-files', state: 'ready' }] });
+        preparation.reconcileHostPreparation(id);
+        const cache = operations(id)[0];
+        const deployment = hosts.queueHostOperation(id, 'instance.create', {});
+        expect(hosts.pendingHostOperations(id, 'write').map(operation => operation.id)).toEqual([deployment.id, cache.id]);
+        hosts.reportHostOperation(id, cache.id, { state: 'running' });
+        const change = hosts.queueHostOperation(id, 'files.stage', {});
+        const delivery = hosts.pendingHostOperations(id, 'write').map(operation => operation.id);
+        expect(delivery.at(-1)).toBe(cache.id);
+        expect(delivery).toContain(deployment.id);
+        expect(delivery).toContain(change.id);
+    });
+
+    it('signals deferral on heartbeats for mutations while ignoring cache work and all observation lanes', async () => {
+        const host = hosts.createHost({ name: 'Cache yielding host' });
+        const ready = { ...inventory, ...capable, runtimeImages: [runtime], libraries: [{ id: 'game-files', state: 'ready' as const }] };
+        const { credential } = hosts.enrollHost(hosts.createEnrollment(host.id).token, ready);
+        preparation.reconcileHostPreparation(host.id);
+        const cache = operations(host.id)[0];
+        hosts.reportHostOperation(host.id, cache.id, { state: 'running' });
+        for (const kind of ['host.inspect', 'instance.inspect', 'rcon.status-batch', 'files.read', 'files.list', 'files.stat', 'files.manifest', 'logs.read']) {
+            hosts.queueHostOperation(host.id, kind, {});
+        }
+        for (const command of ['status', 'getstatus', 'version']) hosts.queueHostOperation(host.id, 'rcon.execute', { command });
+        // Work belonging to another host must not pause this one's cache.
+        const other = enroll(ready);
+        hosts.queueHostOperation(other, 'instance.restart', {});
+        const { POST } = await import('../../src/routes/api/agent/heartbeat/+server.js');
+        const poll = async () => {
+            vi.setSystemTime(Date.now() + 1);
+            const response = await POST({ request: new Request('https://controller.test/api/agent/heartbeat', {
+                method: 'POST', headers: { Authorization: `Bearer ${credential}`, 'Content-Type': 'application/json' },
+                body: JSON.stringify({ inventory: ready })
+            }) });
+            expect(response.status).toBe(200);
+            return response.json();
+        };
+        expect(await poll()).toMatchObject({ deferPlutoniumPreparation: false });
+        const change = hosts.queueHostOperation(host.id, 'rcon.execute', { command: 'map_restart' });
+        expect(await poll()).toMatchObject({ deferPlutoniumPreparation: true });
+        hosts.reportHostOperation(host.id, change.id, { state: 'failed', error: 'Command rejected' });
+        expect(await poll()).toMatchObject({ deferPlutoniumPreparation: false });
+        expect(operations(host.id).filter(operation => operation.kind === 'plutonium.prepare').map(operation => operation.id)).toEqual([cache.id]);
+    });
+
+    it('lets newly published game files interrupt cache refresh, then resumes the same cache operation', async () => {
+        const version = await publish();
+        const ready = { ...capable, runtimeImages: [runtime], libraries: [{ id: version.id, state: 'ready' as const }],
+            plutoniumCache: { revision: 5354, bytes: 200 } };
+        const id = enroll(ready);
+        verified(id, version);
+        await release(5355);
+        preparation.reconcileHostPreparation(id);
+        const cache = operations(id)[0];
+        expect(cache).toMatchObject({ kind: 'plutonium.prepare', payload: { revision: 5355 } });
+        hosts.reportHostOperation(id, cache.id, { state: 'running' });
+        const latest = await publish();
+        heartbeat(id, ready);
+        preparation.reconcileHostPreparation(id);
+        const download = operations(id)[0];
+        expect(download).toMatchObject({ kind: 'library.download', payload: { libraryVersionId: latest.id } });
+        expect(hosts.shouldDeferPlutoniumPreparation(id)).toBe(true);
+        expect(hosts.pendingHostOperations(id, 'write').map(operation => operation.id)).toEqual([download.id, cache.id]);
+        verified(id, latest);
+        hosts.reportHostOperation(id, download.id, { state: 'completed' });
+        heartbeat(id, { ...ready, libraries: [{ id: latest.id, state: 'ready' }] });
+        preparation.reconcileHostPreparation(id);
+        expect(hosts.shouldDeferPlutoniumPreparation(id)).toBe(false);
+        expect(hosts.pendingHostOperations(id, 'write').map(operation => operation.id)).toEqual([cache.id]);
+        expect(operations(id).filter(operation => operation.kind === 'plutonium.prepare')).toHaveLength(1);
+    });
+
+    it('warms only after required files, preserves launch readiness, and waits for fresh cache inventory', async () => {
+        const version = await publish();
+        await release(5354);
+        const id = enroll(capable);
+        preparation.reconcileHostPreparation(id);
+        const pull = operations(id)[0];
+        expect(pull.kind).toBe('runtime.pull');
+        hosts.reportHostOperation(id, pull.id, { state: 'completed' });
+        heartbeat(id, { ...capable, runtimeImages: [runtime] });
+        preparation.reconcileHostPreparation(id);
+        const download = operations(id)[0];
+        expect(download.kind).toBe('library.download');
+        verified(id, version);
+        hosts.reportHostOperation(id, download.id, { state: 'completed' });
+        const ready = { ...capable, runtimeImages: [runtime], libraries: [{ id: version.id, state: 'ready' as const }] };
+        heartbeat(id, ready);
+        expect(preparation.reconcileHostPreparation(id).state).toBe('ready');
+        const cache = operations(id)[0];
+        expect(cache).toMatchObject({ kind: 'plutonium.prepare', payload: {
+            revision: 5354, minimumFreeBytes: hosts.getHost(id)!.minimumFreeBytes, automatic: true
+        } });
+        expect(hosts.requireReadyHost(id).readiness).toBe('ready');
+        expect(hosts.pendingHostOperations(id, 'read')).toEqual([]);
+        expect(hosts.pendingHostOperations(id, 'write').map(operation => operation.id)).toEqual([cache.id]);
+        expect(hosts.listHostOperationHistory(1, 'important', { host: id }).operations[0]).toMatchObject({
+            id: cache.id, routine: false, targetPath: 'Production revision r5354'
+        });
+        preparation.reconcileHostPreparation(id);
+        hosts.reportHostOperation(id, cache.id, { state: 'completed' });
+        const pendingInventory = preparation.reconcileHostPreparation(id);
+        expect(pendingInventory.items.find(item => item.kind === 'plutonium')).toMatchObject({ state: 'preparing' });
+        expect(operations(id)).toHaveLength(3);
+        heartbeat(id, { ...ready, plutoniumCache: { revision: 5354, bytes: 25_000 } });
+        expect(preparation.reconcileHostPreparation(id).items.find(item => item.kind === 'plutonium')).toMatchObject({
+            state: 'ready', detail: expect.stringContaining('r5354')
+        });
+        const { closeDb } = await import('../../src/lib/server/db/index.js');
+        closeDb();
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toHaveLength(3);
+    });
+
+    it('refreshes for newer production releases and reconciles an interrupted refresh without duplicates', async () => {
+        const ready = { ...capable, runtimeImages: [runtime], plutoniumCache: { revision: 5354, bytes: 25_000 } };
+        const id = enroll(ready);
+        await release(5354);
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toEqual([]);
+        await release(5355);
+        preparation.reconcileHostPreparation(id);
+        const cache = operations(id)[0];
+        expect(cache.payload.revision).toBe(5355);
+        hosts.reportHostOperation(id, cache.id, { state: 'unknown' });
+        await release(5356);
+        heartbeat(id, ready);
+        const { closeDb } = await import('../../src/lib/server/db/index.js');
+        closeDb();
+        expect(preparation.reconcileHostPreparation(id).items.find(item => item.kind === 'plutonium')).toMatchObject({
+            state: 'preparing', detail: expect.stringContaining('reconcile interrupted')
+        });
+        expect(operations(id)).toHaveLength(1);
+        expect(hosts.pendingHostOperations(id, 'write').map(operation => operation.id)).toEqual([cache.id]);
+        hosts.reportHostOperation(id, cache.id, { state: 'completed' });
+        heartbeat(id, { ...ready, plutoniumCache: { revision: 5356, bytes: 26_000 } });
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toHaveLength(1);
+        await release(5355);
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toHaveLength(1);
+    });
+
+    it.each(['missing', 'stale', 'failed'] as const)('uses the agent production manifest when release evidence is %s', async evidence => {
+        if (evidence === 'stale') await release(5354, { checkedAt: new Date(Date.now() - 60 * 60_000).toISOString() });
+        if (evidence === 'failed') await release(5354, { error: 'Manifest unavailable' });
+        const id = enroll({ ...capable, runtimeImages: [runtime] });
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)[0]).toMatchObject({ kind: 'plutonium.prepare', payload: { revision: 0 } });
+        expect(hosts.listHostOperationHistory(1, 'important', { host: id }).operations[0].targetPath).toBe('Latest production revision');
+        const cached = enroll({ ...capable, runtimeImages: [runtime], plutoniumCache: { revision: 5353, bytes: 200 } });
+        preparation.reconcileHostPreparation(cached);
+        expect(operations(cached)).toEqual([]);
+    });
+
+    it('leaves agents without the cache capability unchanged', async () => {
+        await release(5355);
+        const id = enroll({ runtimeImages: [runtime], plutoniumCache: { revision: 5354, bytes: 200 } });
+        expect(preparation.reconcileHostPreparation(id).items.some(item => item.kind === 'plutonium')).toBe(false);
+        expect(operations(id)).toEqual([]);
+    });
+
+    it('backs off failed cache work without blocking launch readiness or newly published game files', async () => {
+        const version = await publish();
+        const ready = { ...capable, runtimeImages: [runtime], libraries: [{ id: version.id, state: 'ready' as const }] };
+        const id = enroll(ready);
+        verified(id, version);
+        await release(5354);
+        preparation.reconcileHostPreparation(id);
+        const cache = operations(id)[0];
+        hosts.reportHostOperation(id, cache.id, { state: 'failed', error: 'Plutonium CDN unavailable' });
+        const failedAt = Date.now();
+        heartbeat(id, ready);
+        const status = preparation.reconcileHostPreparation(id);
+        expect(status).toMatchObject({ state: 'ready' });
+        expect(status.items.find(item => item.kind === 'plutonium')).toMatchObject({
+            state: 'blocked', detail: expect.stringContaining('Automatic retry')
+        });
+        expect(hosts.requireReadyHost(id).readiness).toBe('ready');
+        expect(operations(id)).toHaveLength(1);
+        // A changed or expired release must not bypass a failed cache's backoff.
+        await release(5355);
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toHaveLength(1);
+        const latest = await publish();
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)[0]).toMatchObject({ kind: 'library.download', payload: { libraryVersionId: latest.id } });
+        verified(id, latest);
+        hosts.reportHostOperation(id, operations(id)[0].id, { state: 'completed' });
+        heartbeat(id, ready);
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toHaveLength(2);
+        vi.setSystemTime(failedAt + 60_000);
+        heartbeat(id, ready);
+        preparation.reconcileHostPreparation(id);
+        expect(operations(id)).toHaveLength(3);
+        expect(operations(id)[0]).toMatchObject({ kind: 'plutonium.prepare', payload: { revision: 5355 } });
+    });
+
+    it('waits for required library capacity before consuming space for the optional cache', async () => {
+        const version = await publish();
+        const id = enroll({ ...capable, runtimeImages: [runtime], storageAvailable: 1_000 + version.sizeBytes - 1 });
+        hosts.updateHost(id, { minimumFreeBytes: 1_000 });
+        expect(preparation.reconcileHostPreparation(id).state).toBe('blocked');
+        expect(operations(id)).toEqual([]);
+    });
+
+    it.each([null, [], {}, { revision: 0, bytes: 1 }, { revision: 1.5, bytes: 1 }, { revision: 1, bytes: -1 }, { revision: 1, bytes: 0.5 }])(
+        'rejects invalid cache inventory %j', cache => {
+            const id = enroll();
+            expect(() => heartbeat(id, { plutoniumCache: cache as HostInventory['plutoniumCache'] })).toThrow('Invalid Plutonium cache inventory');
+        }
+    );
+
+    it('retains only revision and byte count from cache inventory and clears an omitted cache', () => {
+        const id = enroll({ plutoniumCache: { revision: 5354, bytes: 0, localPath: '/private/cache' } as HostInventory['plutoniumCache'] });
+        expect(hosts.getHost(id)?.inventory.plutoniumCache).toEqual({ revision: 5354, bytes: 0 });
+        heartbeat(id);
+        expect(hosts.getHost(id)?.inventory.plutoniumCache).toBeUndefined();
+    });
+});