{"name":"tengu_vertex_fallback_check","slug":"tengu-vertex-fallback-check","family":"flag","title":"Feature flags","noun":"feature flag","description":null,"description_source":"none","described_by":null,"presence":{"first_seen":null,"removed_in":null,"in_current_build":false,"newest_mined":"2.1.309","builds":0,"mined_builds":150,"first_cited":null},"aliases":[],"entries":[{"version":"2.1.98","anchor":"vertex-ai-model-upgrade-and-fallback-system","heading":"Vertex AI Model Upgrade and Fallback System","line":null,"released_at":"2026-04-09 18:08:49","reason":"gate cited by this entry, found in this entry's text"}],"entries_total":1,"docs":[],"docs_total":0,"gates":[],"related":[{"name":"tengu_vertex_upgrade_check","slug":"tengu-vertex-upgrade-check","description":"An analytics event, not a feature flag. Claude Code logs it at the start of a check for newer default models on Vertex, when the provider is `vertex`, `CLAUDE_CODE_PROVIDER_MANAGED_BY_HOST` is unset, and at least one pinned model tier is found to check. It carries `stale_tiers`, the number of such tiers; each tier whose default model has a Vertex id is then probed and reported separately as `tengu_vertex_probe_result`."}],"url":"https:\/\/changelogs.core-directive.com\/reference\/flag\/tengu-vertex-fallback-check","family_url":"https:\/\/changelogs.core-directive.com\/reference\/flag.json"}