What
For MCP servers configured with type http, the fallback behavior for protocol-version negotiation changed: it now defaults to auto mode (attempting version probing/auto-negotiation) instead of going straight to legacy mode. This is controlled by the gate tengu_mcp_protocol_negotiation_http, which now defaults to enabled (true) unless explicitly turned off. Other MCP connection types (claudeai, stdio, ccr-proxy) are unaffected and still default to legacy fallback.
Why
Auto-negotiation lets Claude Code and an HTTP-based MCP server agree on the best protocol version to use, rather than always assuming the older legacy protocol. This can improve compatibility and unlock newer protocol features automatically for HTTP MCP servers, without any configuration change needed.
tengu_mcp_protocol_negotiation_http On for this account, and not off by defaultThe flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.
This account: on · anonymous baseline: on · compiled default in v2.1.274: on
These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.
Read once, for one account on one subscription tier, against v2.1.274. It isn't a statement about your account. What a flag value here can and cannot tell you
A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.