readme updates

README.md

@@ -2,8 +2,21 @@
 
 ComfyUI-Subworkflow adds reusable workflow boundaries to ComfyUI. It lets one workflow expose named inputs and outputs, then lets another workflow execute it through a single `Subworkflow` node.
 
+![Example workflow used as inner workflow in Subworkflow node](./assets/readme_usage.png)
+
+## Subworkflow vs Subgraph
+
+*Subworkflows are fundametally different from subgraphs. Subworkflow offers a way to reuse entire workflows as nodes in other workflows, while subgraphs are a way to reuse a group of nodes within the same workflow.*
+
+In the example below you can see several workflows are used, and the image to video workflow is used several times:
+
+![Example workflow with several Subworkflow nodes with loaded inner workflows](./assets/readme_wf1.png)
+*Example workflow with several Subworkflow nodes with loaded inner workflows*
+
 ## Custom Nodes
 
+To control the workflow boundaries, this extension adds several custom nodes: `Subworkflow`, `Subworkflow Input`, and `Subworkflow Output`. These nodes work together to load and execute inner workflows while exposing their inputs and outputs on the outer workflow.
+
 ### Subworkflow
 
 Loads a workflow from `ComfyUI/user/default/workflows` and expands it into the current prompt at execution time. The selected inner workflow determines the visible input and output slots on the node.
@@ -14,11 +27,25 @@ Inputs:
 
 Outputs are dynamic and are inferred from the inner workflow's `Subworkflow Output` nodes.
 
+### Subworkflow (from URL)
+
+Loads a workflow from a URL and expands it into the current prompt at execution time. The selected inner workflow determines the visible input and output slots on the node.
+
+Inputs:
+- `url`: absolute `http://` or `https://` URL that returns a workflow JSON file.
+- `at execution`: controls whether the inner workflow URL is reloaded on every execution or a loaded workflow instance is kept.
+- `verify ssl`: controls whether HTTPS certificate validation is enforced while loading from URL.
+
+Outputs are dynamic and are inferred from the inner workflow's `Subworkflow Output` nodes.
+
 ### Subworkflow Input
 
 Marks an input boundary inside a reusable workflow. The `slot_name` widget controls the label shown on the outer `Subworkflow` node. The value type is inferred from the connected node.
 
-When used directly in a normal workflow, `Subworkflow Input` must have its `value` input linked. It may be unlinked only when used as a boundary inside an inner workflow executed by `Subworkflow`.
+When used directly in a normal workflow, `Subworkflow Input` must have its `value` input linked for correct execution.
+That linked node is ignored when used as inner workflow inside `Subworkflow`, and the value is instead provided by the outer `Subworkflow` node input. 
+If no linked node is attached to the `Subworkflow` input, the linked node of the `Subworkflow Input` is used as fallback. This allows for optional inputs on the inner workflow.
+This structure allows for default values to be set on the input, and to use the same workflow as standalone or as inner workflow without changes.
 
 ### Subworkflow Output
 
@@ -26,6 +53,9 @@ Marks an output boundary inside a reusable workflow. The `slot_name` widget cont
 
 `Subworkflow Output` also behaves as a passthrough when other nodes inside the same inner workflow consume its output.
 
+![Example workflow with input and output nodes](./assets/readme_upscale.png)
+*Example workflow setup with (green) input and output nodes for usage as inner workflow.*
+
 ## Features
 
 Create reusable workflow components with named inputs and outputs, then compose them from other workflows. Inner workflows can be loaded fresh for every execution or kept loaded between executions, which allows ComfyUI-style widget state changes such as randomize-after-processing to persist while reload is disabled. UI and API workflow formats are supported, including native ComfyUI subgraphs in UI-format workflows.
@@ -89,6 +119,8 @@ Since the SSL certificate handling of ComfyUI's Python environment may not suppo
 - The `Subworkflow Output` node will not pass through values to it's output when it's used as inner workflow. When the workflow is executed standalone, it will pass through values transparently as expected. 
 - The `Subworkflow Input` will ignore any linked nodes to the input values when used as inner workflow. When the workflow is executed standalone, it will use the linked values transparently as expected.
 - If the input of a corresponding `Subworkflow Input` on the `Subworkflow` node is not linked, the inner workflow will use the linked node of the `Subworkflow Input` node. This allows for optional inputs on the inner workflow.
+- The `Subworkflow` node loads the values from the selected inner workflow as is; including seed numbers. When `at execution` is set to `keep loaded`, the seed value will be updated by the inner workflow if it has a randomize-after-processing node linked to the `Subworkflow Input`. This allows for workflows that need to update their own input values, such as a seed that should randomize on every execution but also be exposed for linking to other nodes.
+- The `Subworkflow` node will keep the loaded file untouched, it will never save any changes to the inner workflow back to the file. 
 
 ## Known Issues
 
@@ -131,4 +163,4 @@ set COMFYUI_SUBWORKFLOW_DEBUG=1
 
 ```js
 localStorage.setItem("swf_debug", "1")
-```
+```