golang/go · critical

not in workspace mode but number of indexes is %v, not 1

Error message

not in workspace mode but number of indexes is %v, not 1

What it means

This is a panic, not a returned error. checkVendorConsistency panics when it is not in workspace mode yet receives more (or fewer) than one modFileIndex. In single-module mode exactly one index is expected; any other count means an internal invariant of the loader was violated.

Source

Thrown at src/cmd/go/internal/modload/vendor.go:159

// go 1.14) or at least does not contradict (go 1.13 or earlier) the
// requirements and replacements listed in the main module's go.mod file.
func checkVendorConsistency(ld *Loader, indexes []*modFileIndex, modFiles []*modfile.File) {
	// readVendorList only needs the main module to get the directory
	// the vendor directory is in.
	readVendorList(VendorDir(ld))

	if len(modFiles) < 1 {
		// We should never get here if there are zero modfiles. Either
		// we're in single module mode and there's a single module, or
		// we're in workspace mode, and we fail earlier reporting that
		// "no modules were found in the current workspace".
		panic("checkVendorConsistency called with zero modfiles")
	}

	pre114 := false
	if !ld.inWorkspaceMode() { // workspace mode was added after Go 1.14
		if len(indexes) != 1 {
			panic(fmt.Errorf("not in workspace mode but number of indexes is %v, not 1", len(indexes)))
		}
		index := indexes[0]
		if gover.Compare(index.goVersion, "1.14") < 0 {
			// Go versions before 1.14 did not include enough information in
			// vendor/modules.txt to check for consistency.
			// If we know that we're on an earlier version, relax the consistency check.
			pre114 = true
		}
	}

	vendErrors := new(strings.Builder)
	vendErrorf := func(mod module.Version, format string, args ...any) {
		detail := fmt.Sprintf(format, args...)
		if mod.Version == "" {
			fmt.Fprintf(vendErrors, "\n\t%s: %s", mod.Path, detail)
		} else {
			fmt.Fprintf(vendErrors, "\n\t%s@%s: %s", mod.Path, mod.Version, detail)
		}

View on GitHub (pinned to b6b368adc5)

Solutions

1. This indicates a Go toolchain bug — report at https://go.dev/issue with the panic stack and reproduction.
2. As a workaround, switch into or out of workspace mode explicitly ('go work' usage) to see if it changes the index count.
3. Run 'go clean -modcache' and 'rm vendor/modules.txt' then 'go mod vendor' to rebuild vendor state.

// Not user-preventable. Sanity-check loader state in tooling before calling vendor checks:
//   if !ld.inWorkspaceMode() && len(indexes) != 1 { panic("loader invariant violated") }

When it happens

Trigger: Vendor consistency checking runs outside workspace mode but the loader hands it a number of indexes != 1. Reachable only through a bug in loader state management or a malformed invocation path.

Common situations: Not user-triggered in normal operation. Could surface from experimental toolchain builds, corrupted build state, or a regression in cmd/go that mis-counts modules outside workspace mode.

Related errors

• internal error: main module version is not allowed: %w
• internal error: package %s is in the main module (%s), but v
• internal error: MatchPackages: %s is not a valid package pat
• internal error: MatchDirs: %s is not a valid filesystem patt
• bufio: reader returned negative count from Read

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/929be495abc8fd67. Report an issue: GitHub.