tengu_vertex_upgrade_check
A Claude Code feature flag, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
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.
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.286 bundle, and it can be wrong.
In the changelogs
1Releases whose published page names tengu_vertex_upgrade_check.
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v2.1.98
Vertex AI Model Upgrade and Fallback System
gate cited by this entry, found in this entry's text
Gate readings
0No release here has a gate table behind it for this flag. Most published releases have none at all: the readings exist only for versions the pipeline captured flag state on.
First cited
0No release's published evidence quotes this name. The ledger indexes the Evidence lines of every changelog on this site, so this says nobody here has ever quoted it; it says nothing about how old the name is.
Presence across releases
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the feature flag does. All feature flags.