### Check for existing issues - [x] I have searched the existing issues and checked that my issue is not a duplicate.

Related prior reports (same family, not an exact open Vertex re-open of the #18854 loss): - #18050 — Veo generate OK, status fails with DefaultCredentialsError (closed) - #17512 — Veo status + download still failing after generate (closed) - #16945 — Veo project/credentials handling; status/content follow-up called out (closed) - #17016 — Azure Sora generate OK, download missing API key (closed) - #33423 / #33437 — OpenAI path: status/content lose model identity / per-model key (open) - PR #18854 — fix for video status/content credential injection for wildcard models (merged into staging, then lost from main)

No open issue currently captures: Vertex Veo + proxy status/content ignore request-level `vertex_project` + #18854 absent from main.

### What happened?

LiteLLM Proxy Video API for Vertex AI (Veo):

1. `POST /v1/videos` can succeed when Vertex project/credentials are available for that call (request params, env, or deployment config). 2. `GET /v1/videos/{video_id}` (status) and `GET /v1/videos/{video_id}/content` (download) fail with:

```text vertex_project…