Workflow customization

Each plugin ships a default ComfyUI workflow JSON under resources/workflow/<plugin>.json. You can replace it with a custom workflow to swap models, add pre/post-processing, or chain effects, as long as the workflow respects the contract the plugin expects.

This page documents that contract.

What the plugin sends

When the plugin submits a job, it loads the workflow JSON from disk and substitutes a fixed set of template variables before POSTing to ComfyUI. The plugin does not otherwise modify the JSON — every node and edge in your custom workflow is preserved.

Template variables

Variable Replaced with When
${INPUT_PATH} The full path to the input EXR file on the server side. Every render.
${OUTPUT_PREFIX} The full path prefix the output EXR(s) should be written to on the server side. Every render.
${FRAME} The numeric frame index for per-frame plugins. Per-frame plugins only.
${IMAGE_LOAD_CAP} The number of frames to load in this sequence pass. Sequence plugins only.
${PROJECT_NAME} The user-facing project name (set in the plugin parameters). Every render.
${WORKFLOW_NAME} The workflow identifier (defaults to the plugin name). Every render.

Strings are substituted literally. For server paths on Windows ComfyUI hosts (UNC paths), the plugin handles backslash escaping for valid JSON automatically.

Variables that are not present in the workflow are silently ignored. Variables referenced in the workflow but unknown to the plugin remain in the JSON literally, which will likely cause ComfyUI to error.

Required nodes

A workflow must contain at least:

  1. A LoadEXR node (or equivalent) reading from ${INPUT_PATH}. For sequence plugins this node also receives ${IMAGE_LOAD_CAP} as the image_load_cap field.
  2. A SaveEXR node (or equivalent) writing to ${OUTPUT_PREFIX}. The prefix already includes the project / workflow / frame hierarchy; do not prepend or modify it.

Anything in between is your business: you can insert color management nodes, pre-processing, additional models, or post-processing.

Replacing the default workflow

  1. In ComfyUI, build and test your custom workflow until it runs end to end with manually-supplied input and output paths.
  2. Export the workflow (Workflow → Export → API Format JSON).
  3. In the exported JSON, replace your test input path with ${INPUT_PATH}, your test output prefix with ${OUTPUT_PREFIX}, and any other applicable template variables.
  4. Save the result to resources/workflow/<plugin>.json in the plugin bundle, replacing the default.
  5. Restart your host application (so the bundle is reloaded).

Alternatively, some plugins expose a Workflow Path parameter that lets you point at an external workflow JSON without modifying the bundle.

Worked example: replacing the upscaler model

Suppose you want to use a different upscaler than upscale_seedvr2 ships with, e.g. an ESRGAN variant for fast comp work where temporal consistency does not matter.

  1. Open ComfyUI and create a workflow with: LoadEXR → ESRGAN Upscale → SaveEXR.
  2. Test it manually. Confirm the EXR output looks right.
  3. Export to API format. Open the JSON in a text editor.
  4. Find the LoadEXR node’s filepath value. Replace it with ${INPUT_PATH}.
  5. Find the LoadEXR node’s image_load_cap value. Replace it with ${IMAGE_LOAD_CAP} if you want sequence behavior, or set it to 1 if you want per-frame.
  6. Find the SaveEXR node’s filename_prefix value. Replace it with ${OUTPUT_PREFIX}.
  7. Save as ~/my-custom-upscaler.json.
  8. In the plugin’s Workflow Path parameter (if exposed), point at this file.
  9. Render.

Limitations

  • The plugin does not validate the workflow before submission. A broken workflow surfaces as a ComfyUI error in the plugin’s status panel.
  • The plugin does not introspect node parameters; you cannot expose a custom node’s parameter as a host-side OFX parameter without modifying the plugin source. The recommended pattern for that is to add a new plugin instead.
  • Some custom nodes have side effects (downloading weights, writing logs, etc.) the plugin does not see. That is by design — the plugin treats ComfyUI as a black box.

For deeper integrations, see Architecture and consider authoring a new plugin.

Plugin code is BSD-3-Clause. Model weights are subject to their upstream licenses; see each plugin page. Images from upstream model authors are reproduced for documentation purposes under applicable fair-use / fair-dealing provisions with attribution; see the credits page. Built by MaGMa for Reepost Studio. Funded by CNC (Centre national du cinéma et de l'image animée).

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