What causes "bad value for %q key: %w" in AdguardTeam/AdGuardHome?

Fetch the version.json URL manually and inspect all keys for empty values

bad value for %q key: %w

Error message

bad value for %q key: %w

What it means

Thrown while parsing the version.json response during an update check. Each value in the JSON map must be a non-empty string; validate.NotEmpty rejects empty or whitespace-only values. The offending key name is included in the message.

Source

Thrown at internal/updater/check.go:110

	data []byte,
) (vi VersionInfo, err error) {
	info := VersionInfo{
		CanAutoUpdate: aghalg.NBFalse,
	}
	versionJSON := map[string]string{
		"version":          "",
		"announcement":     "",
		"announcement_url": "",
	}
	err = json.Unmarshal(data, &versionJSON)
	if err != nil {
		return info, fmt.Errorf("version.json: %w", err)
	}

	for k, v := range versionJSON {
		err = validate.NotEmpty("version_json_value", v)
		if err != nil {
			return info, fmt.Errorf("bad value for %q key: %w", k, err)
		}
	}

	info.NewVersion = versionJSON["version"]
	info.Announcement = versionJSON["announcement"]
	info.AnnouncementURL = versionJSON["announcement_url"]

	packageURL, key, found := u.downloadURL(ctx, versionJSON)
	if !found {
		return info, fmt.Errorf("version.json: bad key %q: %w", key, errors.ErrNoValue)
	}

	isNewVersion := info.NewVersion != u.version
	if isNewVersion {
		u.logger.InfoContext(
			ctx,
			"a new version is available",
			"current_version", u.version,

View on GitHub (pinned to b41aefbe51)

Solutions

Fetch the version.json URL manually and inspect all keys for empty values
Fix the publishing pipeline so every key has a non-empty string (use a placeholder like '-' for announcement)
Switch to the default/stable update channel or official metadata URL
Retry later if the mirror content is transiently corrupted

Example fix

// before
{"version":"v0.107.0","announcement":"","announcement_url":"https://..."}
// after
{"version":"v0.107.0","announcement":"-","announcement_url":"https://..."}

Defensive patterns

Strategy: validation

Validate before calling

resp, err := http.Get(url)
// ...
var vj map[string]string
if err := json.NewDecoder(resp.Body).Decode(&vj); err != nil { /* handle */ }
for k, v := range vj {
    if strings.TrimSpace(v) == "" { /* skip/fix key before calling VersionInfo */ }
}

Try / catch

if _, err := u.VersionInfo(ctx); err != nil {
    if strings.Contains(err.Error(), "bad value for") { /* tolerate and use cached info */ }
}

Prevention

Validate version.json with a schema before feeding it to the updater
Monitor channel metadata generation so no key ships empty

When it happens

Trigger: Calling VersionInfo/parseVersionResponse against a version.json whose 'version', 'announcement', or 'announcement_url' (or any other) key has an empty string value.

Common situations: Corrupted or truncated mirror serving version.json; a CI/staging channel where announcement fields are left blank; manual editing of the channel metadata.

Related errors

AI-assisted analysis of AdguardTeam/AdGuardHome@b41aefbe51 (2026-08-27). Data as JSON: /api/errors/6e35bddcf956ece5. Report an issue: GitHub.