{"record":{"id":"10f3d75c642a753f","repo":"nats-io/nats-server","slug":"processleafheadermsgargs-bad-or-missing-reply-indi","errorCode":null,"errorMessage":"processLeafHeaderMsgArgs Bad or Missing Reply Indicator: '%s'","messagePattern":"processLeafHeaderMsgArgs Bad or Missing Reply Indicator: '(.+?)'","errorType":"validation","errorClass":null,"httpStatus":null,"severity":"error","filePath":"server/leafnode.go","lineNumber":3185,"sourceCode":"\t\treturn fmt.Errorf(\"processLeafHeaderMsgArgs Parse Error: '%s'\", args)\n\tcase 3:\n\t\tc.pa.reply = nil\n\t\tc.pa.queues = nil\n\t\tc.pa.hdb = args[1]\n\t\tc.pa.hdr = parseSize(args[1])\n\t\tc.pa.szb = args[2]\n\t\tc.pa.size = parseSize(args[2])\n\tcase 4:\n\t\tc.pa.reply = args[1]\n\t\tc.pa.queues = nil\n\t\tc.pa.hdb = args[2]\n\t\tc.pa.hdr = parseSize(args[2])\n\t\tc.pa.szb = args[3]\n\t\tc.pa.size = parseSize(args[3])\n\tdefault:\n\t\t// args[1] is our reply indicator. Should be + or | normally.\n\t\tif len(args[1]) != 1 {\n\t\t\treturn fmt.Errorf(\"processLeafHeaderMsgArgs Bad or Missing Reply Indicator: '%s'\", args[1])\n\t\t}\n\t\tswitch args[1][0] {\n\t\tcase '+':\n\t\t\tc.pa.reply = args[2]\n\t\tcase '|':\n\t\t\tc.pa.reply = nil\n\t\tdefault:\n\t\t\treturn fmt.Errorf(\"processLeafHeaderMsgArgs Bad or Missing Reply Indicator: '%s'\", args[1])\n\t\t}\n\t\t// Grab header size.\n\t\tc.pa.hdb = args[len(args)-2]\n\t\tc.pa.hdr = parseSize(c.pa.hdb)\n\n\t\t// Grab size.\n\t\tc.pa.szb = args[len(args)-1]\n\t\tc.pa.size = parseSize(c.pa.szb)\n\n\t\t// Grab queue names.","sourceCodeStart":3167,"sourceCodeEnd":3203,"githubUrl":"https://github.com/nats-io/nats-server/blob/3a66a489d262bf89b71a71c955c94920394532f3/server/leafnode.go#L3167-L3203","documentation":"Leaf-node protocol parse guard: for long-form header messages the reply indicator token (args[1]) is not exactly one character ('+' or '|'), so the message shape is unrecognized.","triggerScenarios":"Thrown at server/leafnode.go:3185 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["Ensure only '+' or '|' reply indicators are emitted","Check for protocol corruption between leaf peers","Upgrade mismatched server versions"],"exampleFix":null,"handlingStrategy":"validation","validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"3a66a489d262bf89b71a71c955c94920394532f3","analyzedAt":"2026-09-02T04:41:54.247Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-08T15:18:49.778Z"}