fix(k1): stabilize repeated acquisition and live viewer recovery

src/k1link/viewer/rerun_bridge.py

@@ -1,6 +1,8 @@
 from __future__ import annotations
 
+import logging
 import math
+import socket
 import time
 from collections.abc import Callable, Mapping
 from contextlib import suppress
@@ -31,6 +33,7 @@ TRAJECTORY_MIN_DISTANCE_METERS = 0.02
 TRAJECTORY_PUBLISH_INTERVAL_NS = 500_000_000
 LIVE_GRPC_BUFFER_LIMIT = "32MiB"
 DEFAULT_GRPC_PORT = 9876
+GRPC_PORT_SEARCH_SPAN = 128
 DEFAULT_CORS_ORIGINS = (
     "http://127.0.0.1:5173",
     "http://localhost:5173",
@@ -40,6 +43,8 @@ DEFAULT_CORS_ORIGINS = (
     "http://localhost:8000",
 )
 
+logger = logging.getLogger("k1link.device_plugins.xgrids_k1.viewer_receiver")
+
 
 @dataclass(frozen=True, slots=True)
 class RerunSceneSettings:
@@ -62,6 +67,34 @@ class RerunSceneSettings:
 SettingsProvider = Callable[[], RerunSceneSettings]
 
 
+def _select_available_grpc_port(
+    preferred_port: int,
+    *,
+    search_span: int = GRPC_PORT_SEARCH_SPAN,
+) -> int:
+    """Select a local Rerun port without reusing a still-served recording."""
+
+    if not 1 <= preferred_port <= 65_535:
+        raise ValueError("Rerun gRPC port must be between 1 and 65535")
+    if search_span < 1:
+        raise ValueError("Rerun gRPC port search span must be positive")
+
+    last_port = min(preferred_port + search_span, 65_536)
+    for candidate in range(preferred_port, last_port):
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as probe:
+            try:
+                # Rerun binds all local interfaces. Probe the same address class
+                # so a previous recording retained by a late viewer is detected.
+                probe.bind(("0.0.0.0", candidate))
+            except OSError:
+                continue
+        return candidate
+    raise RuntimeError(
+        "No local Rerun gRPC port is available in "
+        f"{preferred_port}..{last_port - 1}"
+    )
+
+
 class RerunBridge:
     """Publish transport-neutral canonical envelopes to a Rerun recording."""
 
@@ -85,9 +118,20 @@ class RerunBridge:
         else:
             recording = recording_factory("nodedc_mission_core_spatial")
         try:
+            selected_grpc_port = _select_available_grpc_port(grpc_port)
+            if selected_grpc_port != grpc_port:
+                logger.info(
+                    "Mission Core selected a new Rerun port because an earlier "
+                    "viewer still owns the preferred listener",
+                    extra={
+                        "event_code": "rerun_grpc_port_rotated",
+                        "preferred_port": grpc_port,
+                        "selected_port": selected_grpc_port,
+                    },
+                )
             blueprint = _blueprint(self._settings)
             url = recording.serve_grpc(
-                grpc_port=grpc_port,
+                grpc_port=selected_grpc_port,
                 default_blueprint=blueprint,
                 # This is a reconnect cushion for the live preview, not the source
                 # of record. Raw MQTT evidence is persisted independently. A large
@@ -132,7 +176,7 @@ class RerunBridge:
         return self._url
 
     def begin_session(self, metrics: BridgeMetrics | None = None) -> None:
-        """Reset session state while keeping the process-lifetime server alive."""
+        """Initialize the one acquisition owned by this recording server."""
         if self._closed:
             raise RuntimeError("Rerun bridge is already closed")
         if metrics is not None: