What
The check for MCP_CONNECTION_NONBLOCKING now compares the parsed setting against false instead of coercing the raw environment string, so any value other than an explicit false leaves non-blocking MCP server connection enabled.
Evidence
MCP_CONNECTION_NONBLOCKING
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundleMCP_CONNECTION_NONBLOCKING
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed since
Anthropic's documentation has since written up MCP_CONNECTION_NONBLOCKING, on Environment variables.
| `MCP_CONNECTION_NONBLOCKING` | Controls whether startup waits for MCP servers to connect before the first query. MCP startup is non-blocking by default: servers connect in the background and their tools become available as they finish. S…env-vars see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up MCP_CONNECTION_NONBLOCKING, on Environment variables.