SuperCollider class names are capitalized and methods lowercase; misspelling a UGen name fails outright

SuperCollider distinguishes classes from messages by case: class names are capitalized and methods/messages are lowercase, so SinOsc.ar is Class.method. sinosc, Sinosc, and .AR all fail. Because the language has thousands of UGens, hallucinating or mis-casing a UGen/method name is the single most documented failure mode when emitting SC code. The remedy is to check candidate names against the core class library (names/ugens.txt, names/classes.txt) rather than trusting recall — and to remember that some UGens (Decimator, JPverb) live in the community sc3-plugins package, not the base install.

Examples

SinOsc.ar(440) // correct: Class capitalized, .ar method lowercase sinosc.AR(440) // fails: wrong case on both class and method

Assessment

Why do sinosc.ar and SinOsc.AR both fail in SuperCollider, and what is the recommended guard against emitting a hallucinated UGen name?