helm/helm · error

error while parsing post rendered output: %w

Error message

error while parsing post rendered output: %w

What it means

The final stage of the combined strategy: the single post-renderer run succeeded as a process, but splitAndDeannotate cannot parse its stdout back into a file map (unparseable YAML, non-mapping documents, or annotation/rewrite failures). This error distinguishes bad renderer output from a renderer execution failure (the previous check).

Source

Thrown at pkg/action/action.go:455

			// Here, we merge the documents into a stream, post-render them, and then split
			// them back into a map of filename -> content.

			// Merge files as stream of documents for sending to post renderer
			merged, err := annotateAndMerge(files)
			if err != nil {
				return hs, b, notes, fmt.Errorf("error merging manifests: %w", err)
			}

			// Run the post renderer
			postRendered, err := pr.Run(bytes.NewBufferString(merged))
			if err != nil {
				return hs, b, notes, fmt.Errorf("error while running post render on files: %w", err)
			}

			// Use the file list and contents received from the post renderer
			files, err = splitAndDeannotate(postRendered.String(), "")
			if err != nil {
				return hs, b, notes, fmt.Errorf("error while parsing post rendered output: %w", err)
			}
		default:
			return hs, b, notes, fmt.Errorf("unknown post-render strategy: '%s'", postRenderStrategy)
		}
	}

	// Sort hooks, manifests, and partials. Only hooks and manifests are returned,
	// as partials are not used after renderer.Render. Empty manifests are also
	// removed here.
	hs, manifests, err := releaseutil.SortManifests(files, nil, releaseutil.InstallOrder)
	if err != nil {
		// By catching parse errors here, we can prevent bogus releases from going
		// to Kubernetes.
		//
		// We return the files as a big blob of data to help the user debug parser
		// errors.
		for name, content := range files {
			if strings.TrimSpace(content) == "" {

View on GitHub (pinned to 2a29f1770b)

Solutions

1. Capture and inspect the renderer output: helm template ./mychart | ./render.sh | tee out.yaml, then yq eval-all out.yaml
2. Move every non-YAML line in the renderer to stderr
3. Guarantee stdout is flushed and complete, and exit non-zero on internal errors
4. Ensure each document in the output is a mapping-shaped manifest

Example fix

# before: renderer prints a banner on stdout
printf 'kustomize wrapper v2\n'
kustomize file stdout

# after: banner on stderr, stdout stays pure YAML
printf 'kustomize wrapper v2\n' >&2
kustomize file stdout

// golden contract test: renderer stdout must parse and contain only mapping docs
out := runRendererOverSample()
docs, err := kio.ParseAll(out)
if err != nil {
	log.Fatalf("renderer output unparseable: %v", err)
}
for i, d := range docs {
	if d.YNode().Kind != yaml.MappingNode {
		log.Fatalf("renderer output doc %d is not a mapping", i)
	}
}

if err != nil && strings.Contains(err.Error(), "error while parsing post rendered output") {
	// renderer stdout polluted: capture it (helm template | ./render.sh | tee), clean logging, retry
}

When it happens

Trigger: A post-renderer whose stdout mixes non-YAML content with manifests — log lines, banners, partial output before a crash caught late — or emits documents that are not mappings, under the default combined strategy.

Common situations: Custom scripts printing to stdout instead of stderr; tools that prepend human-readable summaries; a renderer that dies mid-write without a non-zero exit; output encoding problems.

Related errors

• error parsing YAML: %w
• error while parsing post rendered output for %s: %w
• parsing %s: %w
• annotating %s: %w
• writing merged docs: %w

AI-assisted analysis of helm/helm@2a29f1770b (2026-08-15). Data as JSON: /api/errors/6d41aa61128ebc57. Report an issue: GitHub.