What causes "Method not allowed" in argoproj/argo-workflows?

Send the request with method POST: curl -X POST -F "file=@my-artifact.txt"

Method not allowed

Error message

Method not allowed

What it means

UploadInputArtifact handles multipart artifact uploads at /upload-artifacts/{namespace}/{workflowTemplateName}/{artifactName} and only accepts POST. Any other HTTP verb (GET, PUT, DELETE...) is rejected with 405 "Method not allowed" and the handler returns without processing.

Source

Thrown at server/artifacts/artifact_server.go:84

func (a *ArtifactServer) GetOutputArtifact(w http.ResponseWriter, r *http.Request) {
	a.getArtifact(w, r, false)
}

//nolint:contextcheck
func (a *ArtifactServer) GetInputArtifact(w http.ResponseWriter, r *http.Request) {
	a.getArtifact(w, r, true)
}

// UploadInputArtifact handles file uploads for workflow input artifacts
// Path: /upload-artifacts/{namespace}/{workflowTemplateName}/{artifactName}
// Method: POST
// Body: multipart/form-data with "file" field
// Response: JSON with artifact location information
//
//nolint:contextcheck
func (a *ArtifactServer) UploadInputArtifact(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	// Parse path: /upload-artifacts/{namespace}/{workflowTemplateName}/{artifactName}
	requestPath := strings.SplitN(r.URL.Path, "/", 5)
	if len(requestPath) < 5 {
		http.Error(w, "Invalid path. Expected: /upload-artifacts/{namespace}/{workflowTemplateName}/{artifactName}", http.StatusBadRequest)
		return
	}
	namespace := requestPath[2]
	workflowTemplateName := requestPath[3]
	artifactName := requestPath[4]

	// Authenticate and authorize
	ctx, err := a.gateKeeping(r, types.NamespaceHolder(namespace))
	if err != nil {
		a.unauthorizedError(w)
		return

View on GitHub (pinned to 35bff19146)

Solutions

Send the request with method POST: curl -X POST -F "file=@my-artifact.txt" <url>
Use curl -F (multipart form) rather than -d, which defaults to POST anyway but ensure verb is POST
Update any client code/health checks to use POST or a different endpoint

Example fix

# before
curl https://argo-server:2746/upload-artifacts/default/my-tmpl/my-artifact
# after
curl -X POST -F "file=@data.bin" https://argo-server:2746/upload-artifacts/default/my-tmpl/my-artifact

Defensive patterns

Strategy: try-catch

Validate before calling

if (method !== 'POST') {
  throw new Error(`upload-artifacts requires POST, got ${method}`);
}

Try / catch

resp, err := http.Post(url, "", body)
if err != nil { return err }
if resp.StatusCode == http.StatusMethodNotAllowed {
    return fmt.Errorf("endpoint requires POST; check client method")
}

Prevention

Always send POST with a multipart body to this endpoint
Do not probe upload endpoints with GET health checks
Document the endpoint verb in client SDKs

When it happens

Trigger: Issuing a GET or PUT to the upload-artifacts endpoint instead of a POST multipart/form-data request; curl without -X POST or --upload-file defaults; a proxy/health-checker probing the endpoint with GET.

Common situations: Testing the URL in a browser (GET), scripts reusing a generic HTTP helper that defaults to GET, API gateways that rewrite methods.

Related errors

AI-assisted analysis of argoproj/argo-workflows@35bff19146 (2026-09-03). Data as JSON: /api/errors/bf5067ac8eb13893. Report an issue: GitHub.