What causes "preceding tag (%s) not found" in golang/go?

Verify the base tag exists: `git tag --list ' v1.2.3*'` in the source repo.

preceding tag (%s) not found

Error message

preceding tag (%s) not found

What it means

validatePseudoVersion (coderepo.go:765-785) calls r.code.Tags(ctx, tagPrefix+base) to enumerate tags matching the base version and walks them. If none of the returned tags has a version equal to base, lastTag stays empty and this error fires: the pseudo-version claims a preceding tag (its base) that does not exist anywhere in the repo.

Source

Thrown at src/cmd/go/internal/modfetch/coderepo.go:784

	if err != nil {
		return err
	}

	var lastTag string // Prefer to log some real tag rather than a canonically-equivalent base.
	ancestorFound := false
	for _, tag := range tags.List {
		versionOnly := strings.TrimPrefix(tag.Name, tagPrefix)
		if semver.Compare(versionOnly, base) == 0 {
			lastTag = tag.Name
			ancestorFound, err = r.code.DescendsFrom(ctx, info.Name, tag.Name)
			if ancestorFound {
				break
			}
		}
	}

	if lastTag == "" {
		return fmt.Errorf("preceding tag (%s) not found", base)
	}

	if !ancestorFound {
		if err != nil {
			return err
		}
		rev, err := module.PseudoVersionRev(version)
		if err != nil {
			return fmt.Errorf("not a descendent of preceding tag (%s)", lastTag)
		}
		return fmt.Errorf("revision %s is not a descendent of preceding tag (%s)", rev, lastTag)
	}
	return nil
}

func (r *codeRepo) revToRev(rev string) string {
	if semver.IsValid(rev) {
		if module.IsPseudoVersion(rev) {

View on GitHub (pinned to b6b368adc5)

Solutions

Verify the base tag exists: `git tag --list '<tagPrefix>v1.2.3*'` in the source repo.
Re-derive the pseudo-version from the real nearest ancestor tag (`go get <module>@<commit>`).
If you own the repo, restore or recreate the missing tag.
For subdirectory modules, confirm the tag prefix matches the module path major subdirectory.

Example fix

// before (base v1.2.3 never tagged)
require example.com/m v1.2.4-0.20240101120000-e3702bed3d42

// after (base on a real ancestor tag)
require example.com/m v1.2.3-0.20240101120000-e3702bed3d42   // if v1.2.3 exists
// or pin to the real tag
require example.com/m v1.2.3

Defensive patterns

Strategy: validation

Validate before calling

// Confirm the base tag exists before referencing a pseudo-version.
// bash:
//   git tag --list '<tagPrefix>v1.2.3*'
//   # if empty, the base does not exist; re-derive or recreate the tag
//
// Go: re-derive via tooling
//   go get example.com/m@<commit>   // picks the highest real ancestor tag as base

Prevention

Never delete upstream tags that old pseudo-versions reference.
Use `go get @<commit>` so the tool finds a real ancestor tag.
For subdirectory modules, ensure tags are namespaced under the module path.

When it happens

Trigger: A pseudo-version embeds a base like v1.2.3 but the repo never had a v1.2.3 tag (e.g. it was deleted, or the base was fabricated). The tag-prefix lookup (for subdirectory modules, e.g. foo/v1.2.3) also fails.

Common situations: Upstream deleted a tag that older pseudo-versions referenced; pseudo-version was hand-built with an invented base; tags exist only under a different prefix (subdirectory module path mismatch).

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/8c161b42807a8e15. Report an issue: GitHub.