The diagnostic logging just added (cf42152) immediately paid off: the
second laptop's real error, for all five fallback models, was google-auth's
own "Your default credentials were not found" — raised client-side before
any request reaches Google. This laptop has no service account JSON and
has never run `gcloud auth application-default login`; it was never about
Vertex AI Model Garden rollout at all.
The bug was mine: that message contains the literal substring "not
found", so _is_model_not_found_error's naive check misread "you have no
Google credentials on this machine" as "this specific model doesn't
exist" — retrying all five models for an identical, unfixable-by-retrying
failure, then still reporting the wrong final message ("model does not
exist or is not available") because _gemini_error_message made the same
substring mistake.
_is_missing_credentials_error checks for this specific error first, in
both places: the fallback loop now fails fast on the first model instead
of wasting four more identical round trips, and the final message tells
the operator exactly what is actually true — no Google Cloud credentials
exist on this machine, it is per-machine state, and there are two ways to
fix it (paste a service account JSON, or run the gcloud login command
locally) — not that a model is unavailable, which was never the case.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
