GoogleContainerTools/skaffold · error

Sync: Auto is not supported by the build of %s

Error message

Sync: Auto is not supported by the build of %s

What it means

autoSyncItem supports auto sync only for buildpacks and jib builds. If an artifact has neither a BuildpackArtifact nor a JibArtifact (e.g. plain docker build), auto sync cannot derive what to sync, so Skaffold returns this error. The TODO notes it surfaces late — at first file change, not at startup.

Source

Thrown at pkg/skaffold/sync/sync.go:215

			return nil, fmt.Errorf("extracting sync rules from labels for %q: %w", tag, err)
		}

		return syncItem(ctx, a, tag, e, rules, cfg)

	case a.JibArtifact != nil:
		toCopy, toDelete, err := jib.GetSyncDiff(ctx, a.Workspace, a.JibArtifact, e)
		if err != nil {
			return nil, err
		}
		if toCopy == nil && toDelete == nil {
			// do a rebuild
			return nil, nil
		}
		return &Item{Image: tag, Artifact: a, Copy: toCopy, Delete: toDelete}, nil

	default:
		// TODO: this error does appear a little late in the build, perhaps it could surface at first run, rather than first sync?
		return nil, fmt.Errorf("Sync: Auto is not supported by the build of %s", a.ImageName)
	}
}

func latestTag(image string, builds []graph.Artifact) string {
	for _, build := range builds {
		if build.ImageName == image {
			return build.Tag
		}
	}
	return ""
}

func intersect(ctx context.Context, contextWd, containerWd string, syncRules []*latest.SyncRule, files []string) (syncMap, error) {
	ret := make(syncMap)
	for _, f := range files {
		relPath, err := filepath.Rel(contextWd, f)
		if err != nil {
			return nil, fmt.Errorf("changed file %s can't be found relative to context %q: %w", f, contextWd, err)

View on GitHub (pinned to a1189de023)

Solutions

1. For non-jib/buildpack artifacts, replace `sync: auto` with `sync: manual` rules (`- src: '**/*.go' dest: /app/`)
2. Or enable auto sync by building with jib or buildpacks
3. Prefer `sync: infer` for Dockerfile builds where the container layout mirrors the source layout

Example fix

// before
sync:
  auto: true
// after
sync:
  manual:
    - src: 'src/**/*.go'
      dest: /app/src/

if a.BuildpackArtifact == nil && a.JibArtifact != nil == false {
    if a.Sync != nil && a.Sync.Auto != nil && *a.Sync.Auto {
        return errors.New("sync: auto requires jib or buildpacks build; use sync.manual/infer instead")
    }
}

func autoSyncSupported(a *latest.Artifact) bool {
    return a.BuildpackArtifact != nil || a.JibArtifact != nil
}

item, err := sync.NewItem(ctx, a, tag, e, cfg, builds)
if err != nil {
    if strings.Contains(err.Error(), "Auto is not supported") {
        log.Warnf("falling back to manual sync for %s", a.ImageName)
        return syncWithManualRules(ctx, a, tag, e, cfg)
    }
    return err
}

When it happens

Trigger: An artifact built with docker/kustomize/helm-local build (no buildpacks or jib) has `sync: auto` in skaffold.yaml; a file is changed and NewItem -> autoSyncItem hits the default branch and returns the error naming a.ImageName.

Common situations: Switching an artifact from jib to docker build but leaving sync: auto; copying a jib artifact's sync block onto a Dockerfile artifact; typo in build type so Skaffold treats it as a plain build.

Related errors

• retrieving labels for %q: %w
• %q running container image %q errored during run with status
• value must be one of `always`, `missing`, or `never`
• CONFIG_REMOTE_REPO_CACHE_NOT_FOUND_ERR
• CONFIG_REMOTE_REPO_CACHE_NOT_FOUND_ERR

AI-assisted analysis of GoogleContainerTools/skaffold@a1189de023 (2026-09-05). Data as JSON: /api/errors/11e3b836ce6e730e. Report an issue: GitHub.