Hydra errors either throw to the #err element or silently render a black/frozen/blown-out canvas

Hydra’s error surface has two modes. Some failures throw a JavaScript exception, which shows as hydra: <message> in the on-page #err element and freezes the canvas on the last rendered frame (hush cleared the chain; the failed eval installed nothing). Many other failures — missing .out(), NaN from an out-of-range FFT band, feedback runaway — produce no throw and no #err entry; the only signal is that the canvas goes black, frozen, or blown-out. Debugging therefore requires checking both #err and the canvas.

Examples

Typo’d source name (oscil(10)) throws and shows in #err. Missing .out() silently freezes the canvas on the previous frame.

Assessment

Name two Hydra error classes that throw to #err and two that produce no throw, and explain what the canvas shows in each case.