Three CrisperWhisper models were configured and they stacked: each is a resident
Whisper-large in its own process, so the card held two of them plus the server's
text and embedding models until one OOMed inside the encoder's softmax. Nothing
here was the model's fault.

The reservation taken before a load was a hard-coded 3 GB -- roughly the fp16
weights, and about a third of what a verbatim word-timestamp pass peaks at, since
that holds the encoder's attention for a whole 30s window. The worker now reports
its own peak and the figure is recorded as a high-water mark, so the next
reservation is measured rather than guessed.

The eviction ladder had no way to reach a worker's VRAM: it lives in another
process, and acquire_stt_backend pops the model pool, so the manager's busy
signal cannot see a transcription either. There is an external releaser now --
idle workers go at once, a busy one is waited out to the drain budget and only
then taken -- and asking for one model stops its idle siblings.

A cold start was invisible while it lasted. Free VRAM comes from the driver, so a
worker downloading its shards looks like room; live traffic loaded into it and the
transcription OOMed on a card nobody over-committed on purpose. The load window
holds a reservation now.

whisper-server already evicts and knows when it is idle, but it sized itself at
file size x 1.1, which counts the weights and not whisper.cpp's compute buffers.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014T3rZnLhydX9QqUcfBbqLu