What causes "inline cid is empty" in larksuite/cli?

Supply a non-empty cid, or omit cid and let generateCID create a UUID-based one

inline cid is empty

Error message

inline cid is empty

What it means

validateCID enforces that a Content-ID for an inline part is non-empty before it is used in MIME headers and HTML references. An empty cid would produce an invalid Content-ID header and an unreferenceable <img src="cid:...">, so newInlinePart/replaceInline reject it up front.

Source

Thrown at shortcuts/mail/draft/patch.go:855

}

// normalizeCID strips a single RFC 2392 angle-bracket wrapper (<...>) from the
// CID if present, and trims surrounding whitespace.  Unlike strings.Trim, it
// only removes a matched pair so that stray brackets like "test<>" are preserved
// for validation to reject.
func normalizeCID(cid string) string {
	cid = strings.TrimSpace(cid)
	if strings.HasPrefix(cid, "<") && strings.HasSuffix(cid, ">") {
		cid = cid[1 : len(cid)-1]
	}
	return cid
}

// validateCID checks that a Content-ID value is non-empty and free of
// characters that would break MIME headers or cause ambiguous references.
func validateCID(cid string) error {
	if cid == "" {
		return fmt.Errorf("inline cid is empty")
	}
	if err := validate.RejectCRLF(cid, "inline cid"); err != nil {
		return err
	}
	if strings.ContainsAny(cid, " \t<>()") {
		return fmt.Errorf("inline cid %q contains invalid characters (spaces, tabs, angle brackets, or parentheses are not allowed)", cid)
	}
	return nil
}

func ensureInlineContainerRef(partRef **Part) (*Part, error) {
	if partRef == nil || *partRef == nil {
		return nil, fmt.Errorf("body container is nil")
	}
	part := *partRef
	if strings.EqualFold(part.MediaType, "multipart/related") {
		return part, nil
	}

View on GitHub (pinned to 7fd6ef3c07)

Solutions

Supply a non-empty cid, or omit cid and let generateCID create a UUID-based one
Check your cid-producing code for empty results before building the op
Generate the cid from the image path/UUID at call time rather than a blank template

Example fix

// before
{"op":"add_inline","target":{"cid":""},"path":"img.png"}
// after
{"op":"add_inline","target":{"cid":"a1b2c3d4-uuid"},"path":"img.png"}

Defensive patterns

Strategy: validation

Validate before calling

func cidReady(cid string) bool {
	return strings.TrimSpace(cid) != ""
}
// if empty, omit cid and let generateCID assign a UUID

Type guard

func cidReady(cid string) bool {
	return strings.TrimSpace(cid) != ""
}

Try / catch

if err := applyOp(snap, op); err != nil && strings.Contains(err.Error(), "inline cid is empty") {
	// regenerate a cid (UUID) and rebuild the op
}

Prevention

Check for empty cid before building the op; auto-generate one if absent
Don't pass placeholders from templates unfilled
Extract cids from source with a fallback to UUID generation

When it happens

Trigger: Calling inline-add/replace flows with cid:"" or whitespace that trims to empty; building the cid programmatically from a variable that was never set.

Common situations: Template-driven patch generation with unfilled placeholders; passing the filename instead of a generated cid by mistake; upstream cid extraction returning empty for images without a cid.

Related errors

AI-assisted analysis of larksuite/cli@7fd6ef3c07 (2026-09-04). Data as JSON: /api/errors/342ebef90bc40edd. Report an issue: GitHub.