Resolve fixed switch selections during preflight

README.md

@@ -100,13 +100,13 @@ Every variation is checked on the selected Deadline worker after input staging,
 
 - validates every `class_type` against that worker's live `/object_info`;
 - rejects missing staged inputs and known browser-interactive nodes;
-- removes fixed `ImpactSwitch`, `LatentSwitch`, and `SEGSSwitch` pass-through nodes by reconnecting consumers to the selected upstream input;
+- resolves fixed selections from literal values or safe primitive value nodes, then removes `ImpactSwitch`, `LatentSwitch`, and `SEGSSwitch` pass-through nodes by reconnecting consumers to the selected upstream input;
 - sends the complete submitted `extra_pnginfo.workflow` to metadata-aware nodes;
 - verifies that ComfyUI history reports the expected output nodes and that every reported file exists;
 - permits the exact `DeadlineWorkerRegistration` control prompt when both worker and distributed modes are enabled; this prompt completes through history and intentionally produces no file;
 - turns prompt-validation errors, execution exceptions, early process exits, HTTP timeouts, missing output, and Deadline task timeouts into task failures.
 
-Dynamic/connected switch selections are not rewritten. Browser-driven chooser/picker/preview-bridge nodes (`FL_ImagePicker`, `easy imageChooser`, `ImageChooser`, `PreviewChooser`, `PreviewBridge`, and `ImpactPreviewBridge`) are rejected because a farm render has no user to answer them. Other nodes using `PROMPT`, `DYNPROMPT`, `UNIQUE_ID`, or `EXTRA_PNGINFO` remain supported when the worker has the node and the submission includes full workflow metadata. Unknown third-party interactive nodes cannot be identified from `/object_info` alone; add their exact `class_type` to `KNOWN_UI_DEPENDENT_NODE_TYPES` after confirming that they wait for frontend state.
+Dynamic switch selections are accepted when their selector is driven by a safe fixed-value node such as `PrimitiveInt`; the selected branch is resolved while submitting. Selectors driven by runtime or interactive nodes are rejected because a farm render has no user to answer them. Browser-driven chooser/picker/preview-bridge nodes (`FL_ImagePicker`, `easy imageChooser`, `ImageChooser`, `PreviewChooser`, `PreviewBridge`, and `ImpactPreviewBridge`) are rejected for the same reason. Other nodes using `PROMPT`, `DYNPROMPT`, `UNIQUE_ID`, or `EXTRA_PNGINFO` remain supported when the worker has the node and the submission includes full workflow metadata. Unknown third-party interactive nodes cannot be identified from `/object_info` alone; add their exact `class_type` to `KNOWN_UI_DEPENDENT_NODE_TYPES` after confirming that they wait for frontend state.
 
 ## Maintenance Scripts
 

plugins/ComfyUI/ComfyUI.py

@@ -84,6 +84,21 @@ FIXED_SWITCH_SPECS = {
     "SEGSSwitch": {"select": "select", "input": "input{index}"},
 }
 
+# These nodes expose a literal value through output 0.  They are safe to
+# evaluate during submission because their value is part of the API prompt;
+# they do not depend on frontend interaction or worker runtime state.
+FIXED_VALUE_NODE_TYPES = {
+    "PrimitiveBoolean",
+    "PrimitiveFloat",
+    "PrimitiveInt",
+    "PrimitiveString",
+    "PrimitiveNode",
+    "easy boolean",
+    "easy float",
+    "easy int",
+    "easy string",
+}
+
 FILE_OUTPUT_GROUPS = ("images", "gifs", "videos", "audio")
 
 def get_distributed_config_for_plugin(plugin) -> Tuple[bool, bool, bool]:
@@ -1516,8 +1531,44 @@ sys.exit(0 if result.get('success') else 1)
     def _is_link(value):
         return isinstance(value, (list, tuple)) and len(value) == 2 and str(value[0]) != ""
 
+    def _resolve_fixed_value(self, prompt, value, workflow_metadata=None, visited=None):
+        """Resolve a switch selector connected to a literal-value node."""
+        if not self._is_link(value):
+            return value, None
+
+        source_id = str(value[0])
+        try:
+            output_index = int(value[1])
+        except (TypeError, ValueError):
+            return None, None
+        if output_index != 0:
+            return None, None
+
+        visited = set() if visited is None else set(visited)
+        if source_id in visited:
+            return None, None
+        visited.add(source_id)
+
+        source = prompt.get(source_id)
+        if not isinstance(source, dict) or source.get("class_type") not in FIXED_VALUE_NODE_TYPES:
+            return None, None
+
+        source_inputs = source.get("inputs", {})
+        if not isinstance(source_inputs, dict) or "value" not in source_inputs:
+            return None, None
+
+        resolved, resolved_from = self._resolve_fixed_value(
+            prompt,
+            source_inputs["value"],
+            workflow_metadata,
+            visited,
+        )
+        if resolved_from is None and resolved is not None:
+            resolved_from = source_id
+        return resolved, resolved_from
+
     def _resolve_fixed_switches(self, prompt, workflow_metadata=None):
-        """Remove supported constant-selection switches and reconnect consumers."""
+        """Remove supported fixed-selection switches and reconnect consumers."""
         for switch_id, switch in list(prompt.items()):
             if not isinstance(switch, dict):
                 continue
@@ -1527,13 +1578,21 @@ sys.exit(0 if result.get('success') else 1)
                 continue
             inputs = switch.get("inputs", {})
             raw_select = inputs.get(spec["select"])
-            if self._is_link(raw_select):
+            selected_index, selected_from = self._resolve_fixed_value(
+                prompt, raw_select, workflow_metadata
+            )
+            if selected_from is not None:
+                self.LogInfo(
+                    f"Headless preflight resolved {class_type} node {switch_id} "
+                    f"selection from fixed value node {selected_from}: {selected_index}."
+                )
+            elif self._is_link(raw_select):
                 raise ComfyUIError(
                     f"Headless preflight rejected dynamic switch {self._node_context(switch_id, prompt, workflow_metadata)}: "
-                    "the selection is connected and cannot be proven fixed."
+                    "the selection is connected to a non-fixed value."
                 )
             try:
-                selected_index = int(raw_select)
+                selected_index = int(selected_index)
             except (TypeError, ValueError):
                 raise ComfyUIError(
                     f"Headless preflight rejected {self._node_context(switch_id, prompt, workflow_metadata)}: "

tests/test_headless_preflight.py

@@ -31,6 +31,10 @@ def object_info():
             "input": {"required": {}, "hidden": {"extra_pnginfo": "EXTRA_PNGINFO", "unique_id": "UNIQUE_ID"}},
             "output_node": False,
         },
+        "PrimitiveInt": {
+            "input": {"required": {"value": [["INT", {}]]}, "hidden": {}},
+            "output_node": False,
+        },
         "FL_ImagePicker": {"input": {"required": {}, "hidden": {"unique_id": "UNIQUE_ID"}}, "output_node": False},
         "Explode": {"input": {"required": {}, "hidden": {}}, "output_node": False},
         "DeadlineWorkerRegistration": {
@@ -79,6 +83,37 @@ class HeadlessPreflightTests(unittest.TestCase):
             self.assertEqual(result["2"]["inputs"]["images"], ["4", 0])
             self.assertEqual(result["2"]["inputs"]["label"], "input2")
 
+    def test_switch_selection_from_fixed_primitive_is_resolved(self):
+        with tempfile.TemporaryDirectory() as temp:
+            plugin = self.make_plugin(Path(temp))
+            prompt = {
+                "3": {"class_type": "Explode", "inputs": {}},
+                "4": {"class_type": "Explode", "inputs": {}},
+                "5": {
+                    "class_type": "ImpactSwitch",
+                    "inputs": {"select": ["6", 0], "input1": ["3", 0], "input2": ["4", 0]},
+                },
+                "6": {"class_type": "PrimitiveInt", "inputs": {"value": 2}},
+                "2": {"class_type": "SaveImage", "inputs": {"images": ["5", 0]}},
+            }
+            result, _ = plugin._preflight_worker_payload(prompt, WORKFLOW)
+            self.assertNotIn("5", result)
+            self.assertEqual(result["2"]["inputs"]["images"], ["4", 0])
+
+    def test_dynamic_switch_value_node_is_still_rejected(self):
+        with tempfile.TemporaryDirectory() as temp:
+            plugin = self.make_plugin(Path(temp))
+            with self.assertRaisesRegex(ComfyUIError, "connected to a non-fixed value"):
+                plugin._preflight_worker_payload({
+                    "3": {"class_type": "Explode", "inputs": {}},
+                    "4": {"class_type": "Explode", "inputs": {}},
+                    "5": {
+                        "class_type": "ImpactSwitch",
+                        "inputs": {"select": ["3", 0], "input1": ["3", 0], "input2": ["4", 0]},
+                    },
+                    "2": {"class_type": "SaveImage", "inputs": {"images": ["5", 0]}},
+                }, WORKFLOW)
+
     def test_gui_dependent_node_is_rejected_with_context(self):
         with tempfile.TemporaryDirectory() as temp:
             plugin = self.make_plugin(Path(temp))