Found in a production log, during a FULL VRAM CLEANUP ahead of a LoRA training
job:

  Warning in external VRAM releaser: release_f5_engine() takes 0 positional
  arguments but 1 was given

The manager calls every external releaser as `fn(needed_gb)` and sums what they
return. release_f5_engine() declared no parameter, so every call raised TypeError
straight into the manager's warning path: the cached F5-TTS engine held its VRAM
through every eviction, including the exclusive ones that exist precisely because
training needs the whole card. It failed quietly — the warning is one line in a
cleanup that otherwise reports success.

It now takes needed_gb and returns the VRAM delta it observed, like the other
four releasers.

The test checks the shape statically, across every
register_external_vram_releaser call in the tree, so the next releaser cannot be
registered with a signature the manager cannot call. Written against the real
contract: one positional argument, and a value returned. (It first asserted a
default was required too, which flagged _cosite_vram_releaser — but the manager
always passes the argument, so that was the test inventing a rule.)

11 tests. Added with -f: .gitignore ignores test_*.py by default.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0182DhR1eFNPQyGmDrpHbedY