Retry tracker registration when initial connect fails.

Start background re-registration when the tracker is unreachable at startup so nodes do not stay permanently unregistered.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_node_startup.py

@@ -5,8 +5,10 @@ import io
 import os
 import sys
 import tarfile
+import threading
 import time
 import types
+import urllib.error
 import urllib.request
 from pathlib import Path
 
@@ -1644,6 +1646,79 @@ def test_preset_model_startup_honors_pinned_shard_range(tmp_path, monkeypatch):
         tracker.stop()
 
 
+def test_torch_startup_retries_registration_when_tracker_unreachable(
+    tmp_path,
+    monkeypatch,
+):
+    """Failed initial registration should start background retry, not stay unregistered."""
+    import meshnet_node.startup as startup_mod
+
+    class FakeBackend:
+        total_layers = 24
+
+    class FakeTorchNodeServer:
+        def __init__(self, **kwargs):
+            self.backend = FakeBackend()
+            self.port = None
+            self.chat_completion_count = 0
+            self.tracker_node_id = None
+
+        def start(self):
+            self.port = 7000
+            return self.port
+
+        def stop(self):
+            pass
+
+    monkeypatch.setattr(
+        startup_mod,
+        "detect_hardware",
+        lambda: {"device": "cuda", "gpu_name": "Test GPU", "vram_mb": 8192, "ram_mb": 16 * 1024},
+    )
+    monkeypatch.setattr(startup_mod, "TorchNodeServer", FakeTorchNodeServer)
+    monkeypatch.setattr(
+        startup_mod,
+        "_detect_num_layers",
+        lambda *_args, **_kwargs: 24,
+    )
+
+    heartbeat_calls = []
+    monkeypatch.setattr(
+        startup_mod,
+        "_start_heartbeat",
+        lambda *args, **kwargs: heartbeat_calls.append((args, kwargs)) or threading.Thread(),
+    )
+
+    register_calls = {"count": 0}
+
+    def flaky_register(url, payload):
+        register_calls["count"] += 1
+        raise urllib.error.URLError("connection refused")
+
+    monkeypatch.setattr(startup_mod, "_post_json", flaky_register)
+
+    tracker = TrackerServer()
+    tracker_port = tracker.start()
+    tracker_url = f"http://127.0.0.1:{tracker_port}"
+    try:
+        node = run_startup(
+            tracker_url=tracker_url,
+            model_id="Qwen/Qwen2.5-0.5B-Instruct",
+            wallet_path=tmp_path / "wallet.json",
+        )
+        try:
+            assert register_calls["count"] == 1
+            assert node.tracker_node_id is None
+            assert len(heartbeat_calls) == 1
+            args, kwargs = heartbeat_calls[0]
+            assert args[1] == startup_mod._PENDING_NODE_ID
+            assert kwargs["node_ref"] is node
+        finally:
+            node.stop()
+    finally:
+        tracker.stop()
+
+
 def test_real_model_startup_registers_downloaded_inventory_without_checksum(
     tmp_path,
     monkeypatch,