tengu_mcp_negotiation_server_denylist
A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.259 and was gone by v2.1.260.
Remote config can force legacy MCP handshakes or suppress listening for named servers, matched by hostname.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.234.
In the changelogs
1Releases whose published page names tengu_mcp_negotiation_server_denylist.
-
v2.1.234
MCP protocol negotiation can be disabled per server from remote config
Remote config can force legacy MCP handshakes or suppress listening for named servers, matched by hostname.
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.
Flag server, over time
6| Read as | Reading | From | Until | Version installed |
|---|---|---|---|---|
| anonymous | ["bridge.claudeusercontent.com"] | 2026-10-17T05:30:04Z | 2026-10-22T06:25:04Z | v2.1.302 to v2.1.308 |
| this account | ["bridge.claudeusercontent.com"] | 2026-09-29T03:10:05Z | 2026-10-22T06:25:04Z | v2.1.284 to v2.1.308 |
| anonymous | no longer carried | 2026-10-17T05:25:57Z | 2026-10-17T05:25:57Z | v2.1.302 |
| anonymous | ["bridge.claudeusercontent.com"] | 2026-09-29T02:50:05Z | 2026-10-17T05:10:04Z | v2.1.284 to v2.1.302 |
| this account | [] | 2026-09-28T20:10:06Z | 2026-09-29T03:05:04Z | v2.1.284 |
| anonymous | [] | 2026-09-28T20:05:06Z | 2026-09-29T02:40:05Z | v2.1.284 |
One row per unbroken stretch of one reading, newest first, from snapshots taken every twenty-five minutes or so. No longer carried is not off: it means the flag server stopped returning the gate at all, which is what a retired experiment looks like. The version column is what was installed when the reading was taken, not what caused it.
First cited
1The earliest release whose published evidence quoted tengu_mcp_negotiation_server_denylist was v2.1.234, 17 Aug 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 below.
Presence across releases
2Build by build
45One 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.
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.