On iOS 27.0, PrivateCloudComputeLanguageModel refuses a large share of harmless requests, and the same requests often succeed when simply re-run.
Our app writes a short, general-audience explanation of what a song is about. When the cloud model refuses, the on-device model with .permissiveContentTransformations answers the same prompt without trouble. PCC has no guardrail configuration, so there's nothing on our side to adjust.
• Two refusals came within the first sentence of plainly benign text: "Tiny Dancer" (Elton John) at 167 characters, and "In the Ghetto" (Elvis Presley) at 169 characters, while describing snow on a Chicago morning.
• Others include "Already Gone" (Eagles), "Do Ya" (ELO) and "We Didn't Start the Fire" (Billy Joel).
• It's non-deterministic: "Question" (The Moody Blues) was refused, then succeeded 52 seconds later with an identical request.
• Most failures are "Streamed response may contain sensitive or unsafe content", arriving mid-generation, so the rejection seems to target the model's own output rather than the input.
• Rewording the instructions to steer the model toward mainstream, general-audience language didn't change the refusal rate.
Filed as FB24938334 with 8 logFeedbackAttachment captures (.triggeredGuardrailUnexpectedly), each including the rolled-back rejected draft. Siri language English (US), iPhone 16 Pro.
Is PCC's guardrail policy expected to be tuned for content-transformation tasks like this, or is there a recommended pattern for them?