helm/helm · error

error merging %s: %w

Error message

error merging %s: %w

What it means

With PostRenderStrategySeparate, Helm runs the post-renderer once per group of rendered files (per chart/subchart group) instead of one combined stream. For each group it first calls annotateAndMerge on that group's files; this error wraps that merge failure for the named group. The underlying cause is one of the merge-stage failures (parse, annotate, or write) inside a single group's files.

Source

Thrown at pkg/action/action.go:411

			for _, group := range groups {
				if len(group.files) == 0 {
					continue
				}

				if !group.postRender {
					for k, v := range group.files {
						if existing, ok := files[k]; ok {
							files[k] = existing + "\n---\n" + v
						} else {
							files[k] = v
						}
					}
					continue
				}

				merged, err := annotateAndMerge(group.files)
				if err != nil {
					return hs, b, notes, fmt.Errorf("error merging %s: %w", group.name, err)
				}

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

				rendered, err := splitAndDeannotate(postRendered.String(), group.name)
				if err != nil {
					return hs, b, notes, fmt.Errorf("error while parsing post rendered output for %s: %w", group.name, err)
				}

				for k, v := range rendered {
					if existing, ok := files[k]; ok {
						files[k] = existing + "\n---\n" + v
					} else {
						files[k] = v
					}

View on GitHub (pinned to 2a29f1770b)

Solutions

1. Render the named group's chart alone to isolate the bad file: helm template ./charts/<group>
2. Validate each rendered document with a strict YAML parser or yamllint and fix the failing template
3. Rename non-manifest helper files in templates/ with a _ prefix so they are skipped
4. Temporarily switch to the combined strategy to confirm the failure is file content, not strategy wiring

// pre-validate each chart/subchart that will be post-rendered separately
for _, sub := range append([]*chart.Chart{root}, root.Dependencies()...) {
	out, err := renderSubchart(sub)
	if err != nil {
		return err
	}
	if _, err := kio.ParseAll(out); err != nil {
		return fmt.Errorf("subchart %s output fails strict parse: %w", sub.Name(), err)
	}
}

if err != nil && strings.Contains(err.Error(), "error merging") {
	// the named group identifies which chart/subchart failed; render it alone to isolate the file
}

When it happens

Trigger: An install/upgrade/template with postRenderStrategy = PostRenderStrategySeparate where a rendered file inside the named group produces invalid YAML or a non-annotatable document: malformed templates, bad indentation, or scalar documents in the group.

Common situations: Switching from the combined strategy to separate to give each subchart its own post-render pass, which then surfaces an invalid template in one subchart; subchart dependencies (including third-party ones) rendering YAML that strict parsing rejects.

Related errors

• error while parsing post rendered output for %s: %w
• error merging manifests: %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/9786bc0b7f5d9efa. Report an issue: GitHub.