tengu_repl_mcp_error_throwA Claude Code feature flag, read out of the shipped bundle.
It was in the build from v2.1.217 and was gone by v2.1.275.
The gate behind MCP error-throwing now reads under the name tengu_tranquil_fern instead of tengu_repl_mcp_error_throw
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.275 .
First seen v2.1.217 21 Jul 2026
Last seen v2.1.274 16 Sep 2026, gone by v2.1.275
Builds 49 / 149 on this box, as of v2.1.308
Written about v2.1.217 first named in a changelog, 21 Jul 2026
v2.1.217 v2.1.308
In the changelogs
2
Releases whose published page names tengu_repl_mcp_error_throw.
v2.1.275 17 Sep 2026
v2.1.217 21 Jul 2026
Gate readings
2
Release Resolved This account Anonymous Compiled default
v2.1.275 read on another version Not enough to say
no value returned
no value returned
not a boolean we can read
v2.1.217 read on another version Not enough to say
no value returned
no value returned
on
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 .
First cited
0
No 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
2
Builds How many Dates Reading
v2.1.217 – v2.1.274 49 builds 21 Jul 2026 → 16 Sep 2026 ◆ in the build
v2.1.275 – v2.1.308 31 builds 17 Sep 2026 → 22 Oct 2026 ○ not in the build
Build by build
80
One 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.
Build Date State The record behind it
v2.1.217 21 Jul 2026 · addedverdict: added · default bool:true v2.1.218 22 Jul 2026 · presentverdict: present · default bool:true v2.1.219 24 Jul 2026 · presentverdict: present · default bool:true v2.1.220 24 Jul 2026 · presentverdict: present · default bool:true v2.1.221 3 Aug 2026 · presentverdict: present · default bool:true v2.1.222 4 Aug 2026 · presentverdict: present · default bool:true v2.1.223 5 Aug 2026 · presentverdict: present · default bool:true v2.1.224 7 Aug 2026 · presentverdict: present · default bool:true v2.1.225 7 Aug 2026 · presentverdict: present · default bool:true v2.1.226 8 Aug 2026 · presentverdict: present · default bool:true v2.1.227 10 Aug 2026 · presentverdict: present · default bool:true v2.1.228 11 Aug 2026 · presentverdict: present · default bool:true v2.1.229 12 Aug 2026 · presentverdict: present · default bool:true v2.1.231 13 Aug 2026 · presentverdict: present · default bool:true v2.1.232 13 Aug 2026 · presentverdict: present · default bool:true v2.1.233 14 Aug 2026 · presentverdict: present · default bool:true v2.1.234 17 Aug 2026 · presentverdict: present · default bool:true v2.1.235 18 Aug 2026 · presentverdict: present · default bool:true v2.1.236 19 Aug 2026 · presentverdict: present · default bool:true v2.1.237 19 Aug 2026 · presentverdict: present · default bool:true v2.1.238 20 Aug 2026 · presentverdict: present · default bool:true v2.1.239 21 Aug 2026 · presentverdict: present · default bool:true v2.1.240 22 Aug 2026 · presentverdict: present · default bool:true v2.1.241 22 Aug 2026 · presentverdict: present · default bool:true v2.1.242 24 Aug 2026 · presentverdict: present · default bool:true v2.1.243 24 Aug 2026 · presentverdict: present · default bool:true v2.1.245 25 Aug 2026 · presentverdict: present · default bool:true v2.1.246 25 Aug 2026 · presentverdict: present · default bool:true v2.1.247 26 Aug 2026 · presentverdict: present · default bool:true v2.1.248 27 Aug 2026 · presentverdict: present · default bool:true v2.1.250 27 Aug 2026 · presentverdict: present · default bool:true v2.1.251 28 Aug 2026 · presentverdict: present · default bool:true v2.1.252 31 Aug 2026 · presentverdict: present · default bool:true v2.1.257 1 Sep 2026 · presentverdict: present · default bool:true v2.1.258 1 Sep 2026 · presentverdict: present · default bool:true v2.1.259 2 Sep 2026 · presentverdict: present · default bool:true v2.1.260 3 Sep 2026 · presentverdict: present · default bool:true v2.1.261 4 Sep 2026 · presentverdict: present · default bool:true v2.1.263 6 Sep 2026 · presentverdict: present · default bool:true v2.1.265 8 Sep 2026 · presentverdict: present · default bool:true v2.1.266 8 Sep 2026 · presentverdict: present · default bool:true v2.1.267 9 Sep 2026 · presentverdict: present · default bool:true v2.1.268 10 Sep 2026 · presentverdict: present · default bool:true v2.1.269 11 Sep 2026 · presentverdict: present · default bool:true v2.1.270 12 Sep 2026 · presentverdict: present · default bool:true v2.1.271 14 Sep 2026 · presentverdict: present · default bool:true v2.1.272 14 Sep 2026 · presentverdict: present · default bool:true v2.1.273 15 Sep 2026 · presentverdict: present · default bool:true v2.1.274 16 Sep 2026 · presentverdict: present · default bool:true v2.1.275 17 Sep 2026 · removedverdict: removed
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 .
