invalid rule type

[Elegant996]

Experiencing a really weird issue where traefik reports an invalid rule type regardless of the rule. Our existing middleware can be seen below but please note that simplifying this down to first rule also causes the issue. Something is not sitting well with https://github.com/tomMoulard/htransformation/blob/bcfcb3b2979ac73958aad92b37cbe5680346bab9/htransformation.go#L52C21-L52C35.

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: cloudflare-headers
spec:
  plugin:
    headerTransformation:
      Rules:
        - Rule:
            Name: 'Set X-Forwarded-For'
            Header: 'X-Forwarded-For'
            HeaderPrefix: "^"
            Sep: ','
            Values:
              - '^Cf-Connecting-IP'
            Type: 'Join'
        - Rule:
            Name: 'Set X-Real-IP'
            Header: 'X-Real-IP'
            HeaderPrefix: "^"
            Value: '^Cf-Connecting-IP'
            Type: 'Set'
        - Rule:
            Name: 'Set X-Forwarded-Proto'
            Header: 'X-Forwarded-Proto'
            HeaderPrefix: "^"
            Value: '^Cf-Visitor'
            Type: 'Set'
        - Rule:
            Name: 'Rewrite X-Forwarded-Proto'
            Header: 'X-Forwarded-Proto'
            Value: '{ \"scheme\":\"$1\"}'
            ValueReplace: '$1'
            Type: 'RewriteValueRule'

[tomMoulard]

Hello @Elegant996,

Thanks for your interest in the Traefik Plugin !

Do you mind sharing a minimal Traefik configuration + debug logs that shows your issue ?

[Elegant996]

Error from traefik logs:

traefik-external-747487b54-q6wd6 {"level":"error","entryPointName":"websecure","routerName":"nextcloud-nextcloud-cloudflare-97af0abe7d176cd8dad1@kubernetescrd","error":"invalid rule type: ","time":"2025-12-26T08:47:37-05:00"}

Config is as follows (any of the rules trigger the error):

apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: cloudflare
spec:
  chain:
    middlewares:
      - name: cloudflare-headers
      # - name: cloudflare-upload-limit
---
apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: cloudflare-headers
spec:
  plugin:
    headerTransformation:
      Rules:
        - Rule:
            Name: 'Set X-Forwarded-For'
            Header: 'X-Forwarded-For'
            HeaderPrefix: "^"
            Sep: ','
            Values:
              - '^Cf-Connecting-IP'
            Type: 'Join'
        - Rule:
            Name: 'Set X-Real-IP'
            Header: 'X-Real-IP'
            HeaderPrefix: "^"
            Value: '^Cf-Connecting-IP'
            Type: 'Set'
        - Rule:
            Name: 'Set X-Forwarded-Proto'
            Header: 'X-Forwarded-Proto'
            HeaderPrefix: "^"
            Value: '^Cf-Visitor'
            Type: 'Set'
        - Rule:
            Name: 'Rewrite X-Forwarded-Proto'
            Header: 'X-Forwarded-Proto'
            Value: '{ \"scheme\":\"$1\"}'
            ValueReplace: '$1'
            Type: 'RewriteValueRule'

This is deployed using the official traefik helm chart with the follow values.yaml over the base:

experimental:
  plugins:
    headerTransformation:
      moduleName: github.com/tomMoulard/htransformation
      version: v0.3.3
ports:
  websecure:
    asDefault: true
    port: 8443
    expose:
      default: true
    exposedPort: 443
    protocol: TCP
    http3:
      enabled: true
    middlewares:
      - traefik-cloudflare@kubernetescrd