Merged. Root cause first: `publishers.models.list` was called with `pageSize=1000` against Google's hard maximum of 300, so every publisher answered 400 and discovery silently fell back to the stale static catalog. On top of that the PR separates API-key from Service-Account capabilities correctly (keys cannot list Model Garden — project-scoped curated catalog; SA tokens can — live catalog), stops treating the expected generativelanguage rejection of a Service Account as a discovery failure, replaces the speculative partner IDs with documented MaaS IDs, and rejects OAuth client-config JSON with a clear message instead of a misleading one.
The 5 ESLint errors flagged during the earlier fix sweep were fixed in your own follow-up commits; the branch was reconciled with the release tip and the 42 locale files were checked for lost keys before this merge.
Validated as a combined board first (this PR merged with the 4 siblings of the JxnLexn wave on the release tip): eslint with the frozen suppressions, typecheck:core, check:open-sse-typecheck, complexity, cognitive-complexity, changelog-integrity, docs-sync, migration-numbering, provider-consistency and a duplicate-identifier audit all green, plus 77 passing / 0 failing focused node:test cases across the test files the wave touches. The wave's i18n fill (new keys carried to all 66 locales), free-tier doc counts and file-size rebaseline land in one follow-up PR right after the wave, as with #13904.
Thank you — the credential-capability distinction and the retired/non-chat filtering are what make the Vertex listing trustworthy.
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