Warn when a node that runs no code names a device

A device on a node without source was accepted and silently ignored. The
build now reports it as ignored_device, an advisory issue.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

backend/fluksio/flow/controller.py

@@ -174,6 +174,8 @@ class LoadedNode:
     #: Published, and with no body of its own — so what runs is the new-node
     #: template, which returns nothing at all.
     missing_source: bool = False
+    #: The device this node names although its type never runs on a worker.
+    ignored_device: str = ""
 
 
 @dataclass
@@ -1041,6 +1043,8 @@ class FlowController:
             node_type = NODE_TYPES.get(node_def.type)
             if node_type is None:
                 raise ValueError(f"Unknown node type '{node_def.type}'")
+            if node_def.device and not node_type.has_source:
+                entry.ignored_device = node_def.device
 
             params = resolve_params(node_def.params)
 
@@ -1923,6 +1927,22 @@ def _collect_issues(
         for entry in loaded.values()
         if entry.missing_source
     ]
+    # Only code travels to a worker, so a device on any other node is a field
+    # nothing reads. Saying so beats a setting that looks like it took.
+    issues += [
+        ValidationIssue(
+            code="ignored_device",
+            message=(
+                f"Node '{entry.id.rpartition('.')[2]}' names device "
+                f"'{entry.ignored_device}', but only a Function node runs on a "
+                "worker. The setting is ignored."
+            ),
+            flow=entry.flow,
+            node=entry.id,
+        )
+        for entry in loaded.values()
+        if entry.ignored_device
+    ]
     return issues
 
 

backend/fluksio/flow/pipeline.py

@@ -46,7 +46,7 @@ MANUAL_RUN_PREFIX = "manual-"
 # neither the brain graph nor the health summary treats them as a fault.
 # Lives here rather than beside the controller so `ValidationIssue` can carry
 # the distinction itself, and every reader gets it for free.
-ADVISORY_ISSUES = frozenset({"unauthenticated_hook"})
+ADVISORY_ISSUES = frozenset({"unauthenticated_hook", "ignored_device"})
 
 
 class ValidationIssue(BaseModel):
@@ -61,6 +61,7 @@ class ValidationIssue(BaseModel):
         "self_loop_needs_initial",
         "missing_source",
         "node_unhealthy",
+        "ignored_device",
     ]
     message: str
     flow: str = ""

backend/tests/flow/test_drafts.py

@@ -125,6 +125,29 @@ def test_a_published_node_with_no_body_is_reported(store: FlowStore):
     assert [i for i in controller.issues if i.code == "missing_source"] == []
 
 
+def test_a_device_on_a_node_without_code_is_reported(store: FlowStore):
+    """Only code travels to a worker, so the device would be ignored silently."""
+    store.write_flow(
+        FlowDef(
+            name="heating",
+            nodes=[
+                NodeDef(
+                    id="relay",
+                    type="change",
+                    device="gpu",
+                    provides=[MessageSpec(name="temp")],
+                )
+            ],
+        )
+    )
+    controller = FlowController(store)
+
+    asyncio.run(controller.reload())
+    (issue,) = [i for i in controller.issues if i.code == "ignored_device"]
+    assert issue.node == "heating.relay"
+    assert issue.advisory
+
+
 def test_a_node_being_written_in_the_editor_is_not_reported(store: FlowStore):
     """A draft legitimately has no published body yet — that is what a draft is."""
     store.write_draft(a_flow(), 0)

docs/concepts/flows.md

@@ -132,9 +132,10 @@ The canvas reports issues on the affected nodes:
 | `missing_source` | a Function node has no saved code |
 | `node_error` | code or configuration could not load |
 | `unauthenticated_hook` | a webhook or served websocket has no shared secret; advisory |
+| `ignored_device` | a node other than a Function node names a device, which nothing reads; advisory |
 | `node_unhealthy` | a loaded node reports a runtime problem, such as a lost connection |
 
-Build issues prevent the affected flow from running. The last two are runtime
+Build issues prevent the affected flow from running. The last three are runtime
 or advisory issues: other work continues, and node health clears when the
 connection recovers.
 

frontend/src/client/schemas.gen.ts

@@ -4325,7 +4325,7 @@ export const ValidationIssueSchema = {
     properties: {
         code: {
             type: 'string',
-            enum: ['cycle', 'unconnected_input', 'missing_initial_value', 'node_error', 'unauthenticated_hook', 'self_loop_needs_initial', 'missing_source', 'node_unhealthy'],
+            enum: ['cycle', 'unconnected_input', 'missing_initial_value', 'node_error', 'unauthenticated_hook', 'self_loop_needs_initial', 'missing_source', 'node_unhealthy', 'ignored_device'],
             title: 'Code'
         },
         message: {

frontend/src/client/types.gen.ts

@@ -1406,7 +1406,7 @@ export type ValidationError = {
  * Something wrong with a flow — a fault, or merely advisory.
  */
 export type ValidationIssue = {
-    code: 'cycle' | 'unconnected_input' | 'missing_initial_value' | 'node_error' | 'unauthenticated_hook' | 'self_loop_needs_initial' | 'missing_source' | 'node_unhealthy';
+    code: 'cycle' | 'unconnected_input' | 'missing_initial_value' | 'node_error' | 'unauthenticated_hook' | 'self_loop_needs_initial' | 'missing_source' | 'node_unhealthy' | 'ignored_device';
     message: string;
     flow?: string;
     nodes?: Array<(string)>;
@@ -1419,7 +1419,7 @@ export type ValidationIssue = {
     readonly advisory: boolean;
 };
 
-export type code = 'cycle' | 'unconnected_input' | 'missing_initial_value' | 'node_error' | 'unauthenticated_hook' | 'self_loop_needs_initial' | 'missing_source' | 'node_unhealthy';
+export type code = 'cycle' | 'unconnected_input' | 'missing_initial_value' | 'node_error' | 'unauthenticated_hook' | 'self_loop_needs_initial' | 'missing_source' | 'node_unhealthy' | 'ignored_device';
 
 export type ValidationResult = {
     issues?: Array<ValidationIssue>;