What it is
A new gate resolves MCP discovery projection to legacy-only, all or off, and defaults to off.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.259.
Presence across releases
1Build by build
19One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
First cited
1The earliest release whose published evidence quoted tengu_mcp_discover_projection_prior was v2.1.259, 2 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table above.
Gate readings
1| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.259 read on another version | Not enough to say | no value returned | no value returned | no gate table built for this version |
Two arms, because they disagree: this account is the one account this site reads and anonymous is a baseline with no identity attached. A reading says nothing about your account, and off cannot rule out a rollout both readings sit outside of. What these readings can and cannot show.
Names beside it
Every feature flag in the inventory starting tengu_mcp_discover, up to twelve of them.
tengu_mcp_discovery_cacheThe /mcp view now counts cached servers separately so you can tell them from live connections. v2.1.221
tengu_mcp_discovery_cache_enableCalling a tool on a disabled MCP server would tell you to re-enable it, but that path is off. v2.1.238
tengu_mcp_discovery_sourceStartup no longer dials cached HTTP or SSE MCP servers; they restore from cache and connect on first use. 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.