Ramping on demand alone was dangerous with slow endpoints: if the 2
in-flight longbench_v2 requests hang, 'no failures + waiters queued'
kept adding +1 every 5s all the way to 96 -- piling prefills onto a
server that had not answered anything. Both ramp paths (demand-driven
and /metrics) now require at least one SUCCESSFUL completion in the
probe interval; hangs hold the gate until read-timeouts fire and the
x0.7 backoff takes over.
Unit-verified: hang 4 probe intervals with 20 waiters -> limit stays 2;
one success -> +1; one failure -> x0.7.
Co-Authored-By: Claude <noreply@anthropic.com>
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