nats-io/nats-server · error

processRoutedOriginClusterMsgArgs Parse Error: '%s'

Error message

processRoutedOriginClusterMsgArgs Parse Error: '%s'

What it means

processRoutedOriginClusterMsgArgs splits the route protocol's origin-cluster message arguments and hit the len(args) 0-4 case: too few tokens for even the minimal RMSG origin form, meaning the argument line is malformed (missing subject, optional reply/queues, header size or total size fields). Indicates a corrupted or incompatible route protocol message; for a routed account name an extra token is spliced in, so off-by-one token counts also land here.

Source

Thrown at server/route.go:217

				start = i
			}
		}
	}
	if start >= 0 {
		args = append(args, arg[start:])
	}

	var an []byte
	if c.kind == ROUTER {
		if an = c.route.accName; len(an) > 0 && len(args) > 2 {
			args = append(args[:2], args[1:]...)
			args[1] = an
		}
	}
	c.pa.arg = arg
	switch len(args) {
	case 0, 1, 2, 3, 4:
		return fmt.Errorf("processRoutedOriginClusterMsgArgs Parse Error: '%s'", args)
	case 5:
		c.pa.reply = nil
		c.pa.queues = nil
		c.pa.hdb = args[3]
		c.pa.hdr = parseSize(args[3])
		c.pa.szb = args[4]
		c.pa.size = parseSize(args[4])
	case 6:
		c.pa.reply = args[3]
		c.pa.queues = nil
		c.pa.hdb = args[4]
		c.pa.hdr = parseSize(args[4])
		c.pa.szb = args[5]
		c.pa.size = parseSize(args[5])
	default:
		// args[2] is our reply indicator. Should be + or | normally.
		if len(args[3]) != 1 {
			return fmt.Errorf("processRoutedOriginClusterMsgArgs Bad or Missing Reply Indicator: '%s'", args[3])

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Check for version mismatch between clustered nats-server peers (older servers emitting a different RMSG arg layout)
2. Verify no middleware/proxy is mangling the route connection payload
3. Capture the route traffic to inspect the malformed argument line

When it happens

Trigger: Thrown at server/route.go:217 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of nats-io/nats-server@3a66a489d2 (2026-09-02). Data as JSON: /api/errors/7f979380266f3a24. Report an issue: GitHub.