multica-ai/multica · error

read --%s-stdin: %w

Error message

read --%s-stdin: %w

What it means

Thrown when reading the --<prefix>-stdin stream with io.ReadAll fails. This means the operating system or shell failed while delivering stdin — not that the content is invalid. The underlying error is wrapped with %w so the OS cause (e.g. broken pipe, I/O error) is visible in the chain.

Source

Thrown at server/cmd/multica/cmd_agent.go:1403

	switch {
	case count == 0:
		return nil, false, nil
	case count > 1:
		return nil, false, fmt.Errorf("--%s, --%s-stdin, and --%s-file are mutually exclusive; pick one", prefix, prefix, prefix)
	}

	clearHint := ""
	if allowNull {
		clearHint = "; pass 'null' to clear"
	}
	var raw string
	switch {
	case inline:
		raw, _ = cmd.Flags().GetString(prefix)
	case fromStdin:
		buf, err := io.ReadAll(cmd.InOrStdin())
		if err != nil {
			return nil, false, fmt.Errorf("read --%s-stdin: %w", prefix, err)
		}
		raw = string(buf)
		if strings.TrimSpace(raw) == "" {
			return nil, false, fmt.Errorf("--%s-stdin: empty input%s", prefix, clearHint)
		}
	case fromFile:
		if filePath == "" {
			return nil, false, fmt.Errorf("--%s-file: path must not be empty", prefix)
		}
		buf, err := os.ReadFile(filePath)
		if err != nil {
			// Filesystem errors may include the path but not the contents —
			// safe to surface via %w.
			return nil, false, fmt.Errorf("read --%s-file: %w", prefix, err)
		}
		raw = string(buf)
		if strings.TrimSpace(raw) == "" {
			return nil, false, fmt.Errorf("--%s-file %q: empty contents%s", prefix, filePath, clearHint)

View on GitHub (pinned to 2c0912b6ec)

Solutions

1. Fix the upstream command in the pipe — run it alone and confirm it exits 0 before piping into the CLI
2. Write the payload to a file and use --<prefix>-file instead, which removes the pipe dependency
3. Pass the value inline with --<prefix> if it is small enough

Example fix

# before
curl -s https://example.com/cfg.json | multica agent update <id> --mcp-config-stdin
# after
curl -fsS https://example.com/cfg.json -o /tmp/cfg.json && multica agent update <id> --mcp-config-file /tmp/cfg.json

In Go code embedding the CLI or equivalent pipe logic: data, err := io.ReadAll(stdin); if err != nil { log.Fatalf("read stdin: %v", err) } — always branch on the error instead of assuming pipes deliver data.

When it happens

Trigger: Running `multica agent update <id> --mcp-config-stdin` where the producer of stdin dies mid-write (e.g. `curl ... | multica ... --mcp-config-stdin` and curl fails), reading from a closed pipe, or stdin being a descriptor in an error state.

Common situations: Piping a failing curl/jq/cat into the CLI; running under a process supervisor that closes stdin unexpectedly; a CI runner that provides no usable stdin and the pipe errors instead of staying open.

Related errors

• read stdin for --content-stdin: %w
• --%s-stdin: empty input%s
• read --%s-file: %w
• read stdin for --%s: %w
• --months-back=%d would skip buckets before %s (oldest availa

AI-assisted analysis of multica-ai/multica@2c0912b6ec (2026-08-15). Data as JSON: /api/errors/fc97f0a1d3e0a8ba. Report an issue: GitHub.