From d423c47ca612c2adb82acae7c08db7692dcfb16b Mon Sep 17 00:00:00 2001
From: stroblme <stroblme@posteo.de>
Date: Wed, 14 Oct 2026 23:31:54 +0200
Subject: [PATCH] Socket snapshot carries the nodes waiting for a machine, so a
 reconnecting browser restores their queued dots

---
 backend/fluksio/api/routes/flows.py           |  4 ++++
 backend/tests/flow/test_placement.py          | 20 +++++++++++++++++++
 frontend/src/components/Flow/useFlowSocket.ts | 10 ++++++++++
 3 files changed, 34 insertions(+)

diff --git a/backend/fluksio/api/routes/flows.py b/backend/fluksio/api/routes/flows.py
index d4f2a6f..2150ba8 100644
--- a/backend/fluksio/api/routes/flows.py
+++ b/backend/fluksio/api/routes/flows.py
@@ -907,6 +907,8 @@ def snapshot_payload(
     two have to agree, so they build the message here rather than each their
     own. ``emits`` is what the bus counted while nobody was listening — a
     client that reconnects between two pages would otherwise start from zero.
+    ``queued`` is the nodes waiting for a machine, for the same reason: the bus
+    announces a wait once, and a client that missed it would draw the node idle.
 
     ``only`` bounds it to a set of message names, which is what a wall panel
     gets: the values its own dashboards draw, and none of the rest — no node
@@ -925,6 +927,7 @@ def snapshot_payload(
             "paused": [],
             "logs": [],
             "emits": {},
+            "queued": [],
         }
     return {
         "type": "snapshot",
@@ -934,6 +937,7 @@ def snapshot_payload(
         "paused": controller.paused_flows(),
         "logs": list(event_bus.recent_logs),
         "emits": dict(event_bus.emits),
+        "queued": controller.placer.snapshot()["waiting"] if controller.placer else [],
     }
 
 
diff --git a/backend/tests/flow/test_placement.py b/backend/tests/flow/test_placement.py
index 73dabf5..27705ed 100644
--- a/backend/tests/flow/test_placement.py
+++ b/backend/tests/flow/test_placement.py
@@ -193,6 +193,26 @@ def test_a_node_waits_for_a_busy_machine_and_says_so(loop):
     assert placer.snapshot()["waiting"] == []
 
 
+def test_a_reconnecting_client_is_told_what_is_waiting(tmp_path):
+    """The wait is announced once, so the socket's snapshot carries it again.
+
+    A panel is sent none of it, the same as node status.
+    """
+    from fluksio.api.routes.flows import snapshot_payload
+    from fluksio.flow.controller import FlowController
+    from fluksio.flow.store import FlowStore
+
+    placer = Placer(local=ResourceAccountant(cpus=2))
+    placer._announce("study.b", "r1", time.monotonic(), "waiting for 2 cpu(s)")
+    controller = FlowController(FlowStore(tmp_path / "flows"), placer=placer)
+
+    queued = snapshot_payload(controller)["queued"]
+    assert [(e["node"], e["reason"]) for e in queued] == [
+        ("study.b", "waiting for 2 cpu(s)")
+    ]
+    assert snapshot_payload(controller, set())["queued"] == []
+
+
 def test_a_worker_attaching_wakes_what_was_waiting_for_one(loop):
     """A node waiting inside one machine's books could not hear this."""
     hub = RemoteWorkerHub()
diff --git a/frontend/src/components/Flow/useFlowSocket.ts b/frontend/src/components/Flow/useFlowSocket.ts
index 43b1a0f..7f5c364 100644
--- a/frontend/src/components/Flow/useFlowSocket.ts
+++ b/frontend/src/components/Flow/useFlowSocket.ts
@@ -43,6 +43,8 @@ type FlowEvent =
       logs?: LogLine[]
       /** Emission counts per qualified node. Absent on older instances. */
       emits?: Record<string, number>
+      /** Nodes waiting for a machine. Absent on older instances. */
+      queued?: { node: string; reason: string; seconds: number }[]
     }
   | {
       type: "message_value"
@@ -275,6 +277,14 @@ function open(url: string) {
         // Missing against an instance older than this bundle; the graph
         // then starts from zero the way it always did.
         liveStore.setEmits(message.emits ?? {})
+        // `node_queued` is announced once per wait, so a socket that opens
+        // mid-wait learns of it here or draws the node idle.
+        for (const entry of message.queued ?? []) {
+          liveStore.setStatus(entry.node, {
+            status: "queued",
+            detail: entry.reason,
+          })
+        }
         break
       case "message_value":
         liveStore.setValue(message.name, {