Definition
Plain language
When one stuck job at the front of a line freezes everyone waiting behind it, even though those others are fine.
As stated in the literature
A throughput failure where a single slow or stalled request holds up all queued requests behind it; in multi-agent guardrail denial-of-service, one jammed agent forces co-located benign agents to sit idle.
Why it matters: It shows how a single stuck task can drag down an entire system's throughput, turning one local stall into a widespread slowdown.
For example, one frozen agent at the front of a shared queue leaves a dozen perfectly healthy agents stuck waiting behind it.