If I parse the xml with the schema, it throws an error. But then if I parse it without the schema, and validate it against the schema instead, then it's successful. Anyone know why?

(hmmm... deleted my response from a minute ago...)

OK, let's try this again: riffing on your gist, our code looks more like this:

<cfscript>
    sampleXML = '<?xml version="1.0" encoding="UTF-8"?><x:response xmlns:x="<https://demo.sunapsis.iu.edu/ioffice/xml/schema/sunapsis/datalayer>" xmlns:xsi="<http://www.w3.org/2001/XMLSchema>" xsi:schemaLocation="<https://demo.sunapsis.iu.edu/ioffice/xml/schema/sunapsis/datalayer.xsd>"><header><success>false</success><responseInfo/><id>0</id></header><dataset type="null"/></x:response>';
    
    cfhttp(url = "<https://demo.sunapsis.iu.edu/ioffice/xml/schema/sunapsis/datalayer.xsd>", method = "get", result="schema");
    
    try {
        xmlObj = XmlParse(sampleXML, true, schema);
    }
    catch( any error ) {
        WriteDump(error);
        xmlObj = XmlParse(sampleXML, true);
        validation = XmlValidate(xmlObj, schema);
        WriteDump(validation);
    }
</cfscript>

... although we use a local XSD and

schema

in the call in our code points to the file on the local filesystem where the above retrieves the schema and then passes it into the XMLParse() call. There's something weird going on with the XMLParse() function's ability to actually get the schema it needs and having the schema either locally or in a variable passed into that first XMLParse() call avoids that weirdness. This brings back lots of bad memories, BTW.

... and this also works:

<cfscript>
    sampleXML = '<response><header><success>false</success><responseInfo/><id>0</id></header><dataset type="null"/></response>';
    
    cfhttp(url = "<https://demo.sunapsis.iu.edu/ioffice/xml/schema/sunapsis/datalayer.xsd>", method = "get", result="schema");
    
    try {
        xmlObj = XmlParse(sampleXML, true, schema);
    }
    catch( any error ) {
        WriteDump(error);
        xmlObj = XmlParse(sampleXML, true);
        validation = XmlValidate(xmlObj, schema);
        WriteDump(validation);
    }
</cfscript>

... and goes back to your original XML, but just pulls the schema into a local variable.

@rstewart So, in my actual code, I am using a local path to the schema. I just used the URL for the gist, thinking it wouldn't matter. And upon further reflection, I think it doesn't... I think passing the cfhttp result to XmlParse just results in the schema parameter being ignored because it's not valid. If I change it to

XmlParse(sampleXML, true, schema.fileContent)

so i actually have the schema string instead of a cfhttp struct then it starts failing again with the same message as passing a URL or a path. If I add in the prolog and the namespace/schema declarations then it does work. So I think the

lenient

idea is correct. But it looks like that param is Lucee only.