ram pool map

packages/node/meshnet_node/startup.py

@@ -372,6 +372,27 @@ def _start_heartbeat(
         except Exception:
             return False
 
+    def _register_additional_assignment(applied: dict) -> None:
+        model_id = str(applied.get("model") or register_payload.get("hf_repo") or register_payload.get("model"))
+        extra_payload = {
+            **register_payload,
+            "model": model_id.split("/")[-1],
+            "hf_repo": model_id if "/" in model_id else register_payload.get("hf_repo"),
+            "shard_start": applied["shard_start"],
+            "shard_end": applied["shard_end"],
+            "quantization": applied.get("quantization", register_payload.get("quantization")),
+            "tracker_mode": bool(applied.get("tracker_mode", False)),
+            "managed_assignment": True,
+        }
+        try:
+            reg_resp = _post_json(f"{tracker_url}/v1/nodes/register", extra_payload)
+            print(
+                f"  [node] registered additional model — node ID: {reg_resp.get('node_id')}",
+                flush=True,
+            )
+        except Exception as exc:
+            print(f"  [node] WARNING: additional model registration failed: {exc}", flush=True)
+
     def _apply_directives(directives: list[dict]) -> None:
         if not directives:
             return
@@ -384,6 +405,9 @@ def _start_heartbeat(
             print(f"  [node] WARNING: failed to apply tracker directives: {exc}", flush=True)
             return
         if applied:
+            if applied.get("action") == "ADD_SHARD":
+                _register_additional_assignment(applied)
+                return
             model_id = applied.get("model", register_payload.get("hf_repo") or register_payload.get("model"))
             register_payload["model"] = str(model_id).split("/")[-1]
             register_payload["hf_repo"] = model_id
@@ -423,11 +447,12 @@ def _start_heartbeat(
                 new_asgn = resp.get("new_assignment")
                 if new_asgn:
                     print(
-                        f"  [node] tracker reassignment received: "
+                        f"  [node] tracker assignment received: "
-                        f"model={new_asgn.get('model')!r} "
+                        f"action={new_asgn.get('action')!r} model={new_asgn.get('model')!r} "
                         f"shards={new_asgn.get('shard_start')}-{new_asgn.get('shard_end')}",
                         flush=True,
                     )
+                    _apply_directives([new_asgn])
             except urllib.error.HTTPError as exc:
                 if exc.code == 404:
                     # Node was purged (e.g. long gap before restart noticed) — re-register now.
@@ -668,6 +693,7 @@ def run_startup(
             route_timeout=route_timeout,
             cache_dir=cache_dir,
             debug=debug,
+            max_loaded_shards=max_loaded_shards,
         )
         _node_start_time = time.monotonic()
         actual_port = node.start()
@@ -810,6 +836,7 @@ def run_startup(
             route_timeout=route_timeout,
             cache_dir=cache_dir,
             debug=debug,
+            max_loaded_shards=max_loaded_shards,
         )
         _node_start_time = time.monotonic()
         actual_port = node.start()
@@ -883,13 +910,13 @@ def run_startup(
         )
         return node
 
-    if model != "stub-model":
+    if not assigned_hf_repo and model is None:
         raise RuntimeError(
             "Tracker did not assign a model. Join a network that already serves one, "
             "or start with --model <HF_REPO>."
         )
 
-    # 3b. Stub preset path (tests / explicit stub-model only)
+    # 3b. Stub preset path (tests / explicit stub-model) or named preset models.
     print("Querying tracker for shard assignment...", flush=True)
     assign_qs = urllib.parse.urlencode({
         "model": model or "stub-model",

packages/node/meshnet_node/torch_server.py

@@ -75,20 +75,39 @@ class _TorchHTTPServer(http.server.HTTPServer):
         tracker_url: str | None = None,
         route_timeout: float = 30.0,
         debug: bool = False,
+        max_loaded_shards: int = 1,
     ):
         super().__init__(addr, handler)
         self.backend = backend
+        self.backends: dict[str, TorchModelShard] = {backend.model_id: backend}
         self.received_activations = False
         self.forward_chunk_count = 0
         self.tracker_mode = tracker_mode
         self.tracker_url = tracker_url
         self.route_timeout = route_timeout
         self.debug = debug
+        self.max_loaded_shards = max(1, max_loaded_shards)
         self.total_requests: int = 0
         self.failed_requests: int = 0
         self.queue_depth: int = 0
         self._stats_lock = threading.Lock()
 
+    def resolve_backend(self, model_name: str | None) -> TorchModelShard | None:
+        if not model_name:
+            return self.backend
+        wanted = model_name.strip().lower()
+        for key, shard_backend in self.backends.items():
+            key_l = key.lower()
+            if key_l == wanted or key_l.rsplit("/", 1)[-1] == wanted:
+                return shard_backend
+        return self.backend
+
+    def chat_enabled(self) -> bool:
+        return any(
+            shard_backend.is_head
+            for shard_backend in self.backends.values()
+        )
+
 
 class _TorchHandler(http.server.BaseHTTPRequestHandler):
     def log_message(self, fmt, *args):  # noqa: suppress request logs in tests
@@ -100,7 +119,7 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
             self._handle_forward()
         elif self.path == "/v1/infer":
             self._handle_infer()
-        elif self.path == "/v1/chat/completions" and server.tracker_mode:
+        elif self.path == "/v1/chat/completions" and server.chat_enabled():
             self._handle_chat_completions()
         else:
             self.send_response(404)
@@ -284,22 +303,26 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
             messages = []
         stream = bool(body.get("stream", False))
         model_name = str(body.get("model", ""))
+        backend = server.resolve_backend(model_name)
+        if backend is None or not backend.is_head:
+            self._send_json(400, {"error": "model not loaded on this node"})
+            return
         max_tokens = int(body.get("max_tokens") or body.get("max_new_tokens") or 256)
         temperature = float(body.get("temperature") or 1.0)
         top_p = float(body.get("top_p") or 1.0)
 
         # Fast path: this node owns the complete model — use HF generate() with KV cache.
         # Avoids the single-token-per-forward-pass limitation of the distributed path.
-        if server.backend.is_head and server.backend.is_tail:
+        if backend.is_head and backend.is_tail:
             try:
                 if stream:
                     self._stream_openai_response(
-                        server.backend.generate_text_streaming(messages, max_tokens, temperature, top_p),
+                        backend.generate_text_streaming(messages, max_tokens, temperature, top_p),
                         model_name,
                     )
                 else:
-                    text = server.backend.generate_text(messages, max_tokens, temperature, top_p)
+                    text = backend.generate_text(messages, max_tokens, temperature, top_p)
-                    self._send_openai_response(text, model_name, False, messages)
+                    self._send_openai_response(text, model_name, False, messages, backend=backend)
             except Exception as exc:
                 self._record_failed_request()
                 self._send_json(500, {"error": f"generation failed: {exc}"})
@@ -309,7 +332,7 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
         # We do N single-step forward passes (no cross-node KV cache), which is slow
         # but correct. Each step: head encodes current sequence → forwards through route
         # → tail returns the next token string → append → repeat.
-        remaining_route = self._get_remaining_route(model_name)
+        remaining_route = self._get_remaining_route(model_name, backend=backend)
         print(
             f"  [node] chat route model={model_name!r} max_tokens={max_tokens} "
             f"downstream={remaining_route}",
@@ -318,11 +341,10 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
         if not remaining_route:
             self._send_openai_response(
                 "error: no downstream route — check tracker connectivity",
-                model_name, False, messages,
+                model_name, False, messages, backend=backend,
             )
             return
 
-        backend = server.backend
         # Format with chat template so the model knows it's in assistant mode.
         try:
             if hasattr(backend.tokenizer, "apply_chat_template"):
@@ -352,7 +374,7 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
             except Exception as exc:
                 print(f"  [node] distributed encode error: {exc}", flush=True)
                 break
-            token_str = self._run_downstream_pipeline(payload, remaining_route)
+            token_str = self._run_downstream_pipeline(payload, remaining_route, backend=backend)
             if not token_str:
                 break
             # Stop on error responses or EOS.
@@ -369,9 +391,9 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
         if stream_emit is not None:
             stream_emit(None)
             return
-        self._send_openai_response(result_text, model_name, stream, messages)
+        self._send_openai_response(result_text, model_name, stream, messages, backend=backend)
 
-    def _get_remaining_route(self, model: str) -> list[dict]:
+    def _get_remaining_route(self, model: str, *, backend: TorchModelShard | None = None) -> list[dict]:
         """Return downstream hops as dicts with endpoint, start_layer, and optional relay_addr.
 
         Fast path reads X-Meshnet-Route header injected by the tracker.
@@ -404,9 +426,10 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
 
         # Slow path: query the tracker (direct node-to-node calls, or tracker didn't inject).
         server: _TorchHTTPServer = self.server  # type: ignore[assignment]
+        active_backend = backend or server.backend
         if server.tracker_url is None:
             return []
-        route_model = getattr(server.backend, "model_id", None) or model
+        route_model = getattr(active_backend, "model_id", None) or model
         try:
             url = f"{server.tracker_url}/v1/route?model={urllib.parse.quote(route_model)}"
             with urllib.request.urlopen(url, timeout=server.route_timeout) as r:
@@ -433,18 +456,19 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
             print(f"  [node] WARNING: route lookup failed for {route_model!r}: {exc}", flush=True)
             return []
 
-    def _run_downstream_pipeline(self, payload: object, route: list[dict]) -> str:
+    def _run_downstream_pipeline(self, payload: object, route: list[dict], *, backend: TorchModelShard | None = None) -> str:
         server: _TorchHTTPServer = self.server  # type: ignore[assignment]
+        active_backend = backend or server.backend
         if not route:
             # Partial shard at tail: decode the activation from the previous node.
             # Full single-node (head+tail) is handled before entering this method.
-            if server.backend.is_tail:
+            if active_backend.is_tail:
                 try:
-                    tensor = server.backend.torch.frombuffer(
+                    tensor = active_backend.torch.frombuffer(
                         bytearray(payload.body),  # type: ignore[union-attr]
-                        dtype=server.backend.torch.bfloat16,
+                        dtype=active_backend.torch.bfloat16,
-                    ).reshape(payload.shape).to(server.backend.device)  # type: ignore[union-attr]
+                    ).reshape(payload.shape).to(active_backend.device)  # type: ignore[union-attr]
-                    return server.backend.decode_tail(tensor)
+                    return active_backend.decode_tail(tensor)
                 except Exception as exc:
                     return f"decode error: {exc}"
             return "no downstream route available for non-tail shard"
@@ -591,11 +615,13 @@ class _TorchHandler(http.server.BaseHTTPRequestHandler):
         model: str,
         stream: bool,
         messages: list[dict] | None = None,
+        backend: TorchModelShard | None = None,
     ) -> None:
         chunk_id = "chatcmpl-node"
         created = int(time.time())
+        active_backend = backend or self.server.backend  # type: ignore[attr-defined]
         if not stream:
-            usage = _usage_for_response(self.server.backend, messages or [], text)  # type: ignore[attr-defined]
+            usage = _usage_for_response(active_backend, messages or [], text)
             self._send_json(200, {
                 "id": chunk_id,
                 "object": "chat.completion",
@@ -706,9 +732,11 @@ class TorchNodeServer:
         route_timeout: float = 30.0,
         cache_dir: Path | None = None,
         debug: bool = False,
+        max_loaded_shards: int = 1,
     ) -> None:
         self._host = host
         self._requested_port = port
+        self._max_loaded_shards = max(1, max_loaded_shards)
         self._backend = backend or _load_backend(
             model_id,
             shard_start,
@@ -716,6 +744,7 @@ class TorchNodeServer:
             quantization,
             cache_dir,
         )
+        self._backends: dict[str, TorchModelShard] = {self._backend.model_id: self._backend}
         # Auto-detect tracker mode: enabled when shard_start == 0 or explicitly set
         self._tracker_mode = tracker_mode if tracker_mode is not None else (shard_start == 0)
         self._tracker_url = tracker_url
@@ -754,41 +783,64 @@ class TorchNodeServer:
     def queue_depth(self) -> int:
         return self._server.queue_depth if self._server is not None else 0
 
+    @property
+    def loaded_model_ids(self) -> list[str]:
+        return list(self._backends.keys())
+
     def apply_tracker_directives(self, directives: list[dict]) -> dict | None:
-        """Apply tracker LOAD_SHARD directives by hot-swapping the loaded backend."""
+        """Apply tracker shard directives (LOAD_SHARD replace, ADD_SHARD load-more)."""
+        add_directive = next(
+            (directive for directive in reversed(directives) if directive.get("action") == "ADD_SHARD"),
+            None,
+        )
         load_directive = next(
             (directive for directive in reversed(directives) if directive.get("action") == "LOAD_SHARD"),
             None,
         )
-        if load_directive is None:
+        directive = add_directive or load_directive
+        if directive is None:
             return None
-        shard_start = int(load_directive["shard_start"])
+        shard_start = int(directive["shard_start"])
-        shard_end = int(load_directive["shard_end"])
+        shard_end = int(directive["shard_end"])
-        quantization = str(load_directive.get("quantization") or self._backend.quantization)
+        quantization = str(directive.get("quantization") or self._backend.quantization)
-        model_id = str(load_directive.get("model") or self._backend.model_id)
+        model_id = str(directive.get("model") or self._backend.model_id)
+        replacing = directive.get("action") == "LOAD_SHARD"
+        if not replacing and len(self._backends) >= self._max_loaded_shards:
+            print(
+                f"  [node] WARNING: ignoring ADD_SHARD for {model_id!r} — "
+                f"loaded {len(self._backends)}/{self._max_loaded_shards} slots full",
+                flush=True,
+            )
+            return None
+        action_label = "reassigned" if replacing else "additional"
         print(
-            f"  [node] loading reassigned shard: {model_id} layers {shard_start}-{shard_end}",
+            f"  [node] loading {action_label} shard: {model_id} layers {shard_start}-{shard_end}",
             flush=True,
         )
         try:
             new_backend = _load_backend(model_id, shard_start, shard_end, quantization, self._cache_dir)
         except TypeError:
             new_backend = _load_backend(model_id, shard_start, shard_end, quantization)
-        self._backend = new_backend
+        self._backends[model_id] = new_backend
-        self._tracker_mode = shard_start == 0
+        if replacing or shard_start == 0:
-        if self._server is not None:
+            self._backend = new_backend
-            self._server.backend = new_backend
+            self._tracker_mode = shard_start == 0
-            self._server.tracker_mode = self._tracker_mode
         print(
-            f"  [node] loaded reassigned shard: {model_id} layers {shard_start}-{shard_end}",
+            f"  [node] loaded {action_label} shard: {model_id} layers {shard_start}-{shard_end}",
             flush=True,
         )
+        if self._server is not None:
+            self._server.backends = dict(self._backends)
+            if replacing or shard_start == 0:
+                self._server.backend = new_backend
+                self._server.tracker_mode = self._tracker_mode
         return {
+            "action": directive.get("action"),
             "model": model_id,
             "shard_start": shard_start,
             "shard_end": shard_end,
             "quantization": quantization,
-            "tracker_mode": self._tracker_mode,
+            "tracker_mode": shard_start == 0,
         }
 
     def start(self) -> int:
@@ -802,7 +854,9 @@ class TorchNodeServer:
             self._tracker_url,
             self._route_timeout,
             self._debug,
+            self._max_loaded_shards,
         )
+        self._server.backends = dict(self._backends)
         self.port = self._server.server_address[1]
         self._thread = threading.Thread(target=self._server.serve_forever, daemon=True)
         self._thread.start()

packages/tracker/meshnet_tracker/server.py

@@ -944,6 +944,20 @@ def _pool_summary(nodes: list[_NodeEntry], preset: dict | None = None) -> dict:
     }
 
 
+def _repo_demand_rpm(
+    server: "_TrackerHTTPServer",
+    repo: str,
+    local_rpms: dict[str, dict],
+) -> float:
+    """Look up recent request rate by hf_repo or preset alias."""
+    if repo in local_rpms:
+        return float(local_rpms[repo].get("rpm_last_hour", 0.0) or 0.0)
+    resolved_name, _preset = _resolve_model_preset(server.model_presets, repo)
+    if resolved_name and resolved_name in local_rpms:
+        return float(local_rpms[resolved_name].get("rpm_last_hour", 0.0) or 0.0)
+    return 0.0
+
+
 def _preset_for_node(server: "_TrackerHTTPServer", node: _NodeEntry) -> dict | None:
     if node.hf_repo:
         _resolved, preset = _resolve_model_preset(server.model_presets, node.hf_repo)
@@ -1392,20 +1406,6 @@ def _assign_redundant_managed_nodes(
         _emit_shard_change_directives(node, model, previous_range, preset)
 
 
-def _repo_demand_rpm(
-    server: "_TrackerHTTPServer",
-    repo: str,
-    local_rpms: dict[str, dict],
-) -> float:
-    """Look up recent request rate by hf_repo or preset alias."""
-    if repo in local_rpms:
-        return float(local_rpms[repo].get("rpm_last_hour", 0.0) or 0.0)
-    resolved_name, _preset = _resolve_model_preset(server.model_presets, repo)
-    if resolved_name and resolved_name in local_rpms:
-        return float(local_rpms[resolved_name].get("rpm_last_hour", 0.0) or 0.0)
-    return 0.0
-
-
 def _relay_http_request_frames(
     relay_addr: str,
     path: str,
@@ -2587,6 +2587,7 @@ class _TrackerHandler(http.server.BaseHTTPRequestHandler):
         with server.lock:
             self._purge_expired_nodes()
             nodes = list(server.registry.values())
+            memory_pool = _memory_pool_map(server)
 
         def capacity_for(node: _NodeEntry) -> dict:
             preset = None
@@ -2611,6 +2612,7 @@ class _TrackerHandler(http.server.BaseHTTPRequestHandler):
         self._send_json(200, {
             "relay_url": server.relay_url,
             "pool": _pool_summary(nodes),
+            "memory_pool": memory_pool,
             "recommended_models": [
                 {
                     "id": name,
@@ -3538,10 +3540,16 @@ class _TrackerHandler(http.server.BaseHTTPRequestHandler):
         )
         with server.lock:
             self._purge_expired_nodes()
-            # Dedup: if this endpoint is already registered, remove the old entry first.
+            # Dedup: replace the same node id or the same endpoint+model assignment.
+            endpoint_key = entry.endpoint.rstrip("/")
+            model_key = entry.hf_repo or entry.model
             stale_ids = [
                 eid for eid, e in server.registry.items()
-                if e.endpoint == entry.endpoint.rstrip("/")
+                if eid == node_id
+                or (
+                    e.endpoint.rstrip("/") == endpoint_key
+                    and (e.hf_repo or e.model) == model_key
+                )
             ]
             stale_entries: list[tuple[str, _NodeEntry]] = []
             for eid in stale_ids:
@@ -5436,6 +5444,7 @@ class TrackerServer:
             with self._lock:
                 _purge_expired_nodes_locked(server)
                 _rebalance_all_locked(server)
+                _scale_demanded_models_locked(server)
 
     def _push_to_peers(self, path: str, body: bytes) -> bool:
         """POST a hive-signed payload to every cluster peer; True if all succeeded."""

tests/test_tracker_routing.py

@@ -13,7 +13,13 @@ from meshnet_gateway.server import GatewayServer, _banned_route_wallet
 from meshnet_node.server import StubNodeServer
 from meshnet_contracts import LocalSolanaContracts
 from meshnet_tracker.auth import sign_hive_request
-from meshnet_tracker.server import TrackerServer, _NodeEntry, _registration_ban_error
+from meshnet_tracker.server import (
+    TrackerServer,
+    _NodeEntry,
+    _memory_pool_map,
+    _registration_ban_error,
+    _scale_demanded_models_locked,
+)
 
 _TEST_HIVE_SECRET = "test-hive-secret"
 
@@ -2340,6 +2346,7 @@ def test_torch_node_applies_tracker_load_shard_directive(monkeypatch):
 
     assert loaded == [("Qwen/Qwen2.5-0.5B-Instruct", 0, 23, "bfloat16")]
     assert applied == {
+        "action": "LOAD_SHARD",
         "model": "Qwen/Qwen2.5-0.5B-Instruct",
         "shard_start": 0,
         "shard_end": 23,
@@ -2456,3 +2463,105 @@ def test_shard_heal_cycle_surviving_node_covers_dead_peers_gap(monkeypatch):
         )
     finally:
         tracker.stop()
+
+
+def test_network_map_exposes_memory_pool():
+    tracker = TrackerServer(model_presets={
+        "tiny-model": {
+            "total_layers": 8,
+            "bytes_per_layer": {"bfloat16": 1_000},
+            "hf_repo": "org/TinyModel",
+        },
+    })
+    tracker_port = tracker.start()
+    try:
+        _post_json(
+            f"http://127.0.0.1:{tracker_port}/v1/nodes/register",
+            {"endpoint": "http://127.0.0.1:9050", "model": "tiny-model",
+             "hf_repo": "org/TinyModel", "num_layers": 8,
+             "shard_start": 0, "shard_end": 7, "max_loaded_shards": 2,
+             "vram_bytes": 20_000, "ram_bytes": 20_000, "quantizations": ["bfloat16"],
+             "benchmark_tokens_per_sec": 1.0, "hardware_profile": {}, "score": 1.0},
+        )
+        net = _get_json(f"http://127.0.0.1:{tracker_port}/v1/network/map")
+        pool = net["memory_pool"]
+        assert pool["total_spare_slots"] == 1
+        assert pool["hosts"][0]["loaded_slots"] == 1
+        assert pool["hosts"][0]["max_loaded_shards"] == 2
+        assert pool["hosts"][0]["memory_spare_bytes"] > 0
+    finally:
+        tracker.stop()
+
+
+def test_same_endpoint_can_register_multiple_models():
+    tracker = TrackerServer()
+    tracker_port = tracker.start()
+    try:
+        base = {
+            "endpoint": "http://127.0.0.1:9055",
+            "num_layers": 24,
+            "shard_start": 0,
+            "shard_end": 23,
+            "hardware_profile": {},
+            "score": 1.0,
+            "max_loaded_shards": 2,
+            "vram_bytes": 50_000_000,
+            "ram_bytes": 50_000_000,
+        }
+        first = _post_json(
+            f"http://127.0.0.1:{tracker_port}/v1/nodes/register",
+            {**base, "model": "Qwen2.5-0.5B-Instruct", "hf_repo": "Qwen/Qwen2.5-0.5B-Instruct"},
+        )
+        second = _post_json(
+            f"http://127.0.0.1:{tracker_port}/v1/nodes/register",
+            {**base, "model": "OtherModel", "hf_repo": "org/OtherModel"},
+        )
+        assert first["node_id"] != second["node_id"]
+        assert len(tracker._registry) == 2
+    finally:
+        tracker.stop()
+
+
+def test_scale_demanded_models_queues_add_shard_on_spare_host():
+    tracker = TrackerServer(model_presets={
+        "model-a": {
+            "total_layers": 4,
+            "bytes_per_layer": {"bfloat16": 1_000},
+            "hf_repo": "org/ModelA",
+        },
+        "model-b": {
+            "total_layers": 4,
+            "bytes_per_layer": {"bfloat16": 1_000},
+            "hf_repo": "org/ModelB",
+        },
+    })
+    tracker_port = tracker.start()
+    try:
+        reg_b = _post_json(
+            f"http://127.0.0.1:{tracker_port}/v1/nodes/register",
+            {"endpoint": "http://127.0.0.1:9061", "model": "model-b",
+             "hf_repo": "org/ModelB", "num_layers": 4,
+             "shard_start": 0, "shard_end": 3, "max_loaded_shards": 2,
+             "vram_bytes": 20_000, "ram_bytes": 20_000, "quantizations": ["bfloat16"],
+             "benchmark_tokens_per_sec": 1.0, "hardware_profile": {}, "score": 1.0},
+        )
+        _post_json(
+            f"http://127.0.0.1:{tracker_port}/v1/nodes/register",
+            {"endpoint": "http://127.0.0.1:9060", "model": "model-a",
+             "hf_repo": "org/ModelA", "num_layers": 4,
+             "shard_start": 0, "shard_end": 3, "max_loaded_shards": 1,
+             "vram_bytes": 20_000, "ram_bytes": 20_000, "quantizations": ["bfloat16"],
+             "benchmark_tokens_per_sec": 1.0, "hardware_profile": {}, "score": 1.0},
+        )
+        assert tracker._stats is not None
+        for _ in range(400):
+            tracker._stats.record_request("org/ModelA")
+        with tracker._lock:
+            _scale_demanded_models_locked(tracker._server)  # type: ignore[arg-type]
+        node_b = tracker._registry[reg_b["node_id"]]
+        assignment = node_b.pending_new_assignment
+        assert assignment is not None
+        assert assignment["action"] == "ADD_SHARD"
+        assert assignment["model"] == "org/ModelA"
+    finally:
+        tracker.stop()