What
Setting the environment variable CLAUDE_GATEWAY_LOG_FORMAT to json makes messages from Claude Code's gateway, the ones starting with claude gateway:, come out as structured error logs instead of plain text. An environment variable is a named value you set before starting a program.
Separately, programs driving Claude Code through the SDK now receive a status update about how content links are shown, which in one case reports that a link was drawn as plain text.
Why
Gateway operators can feed the gateway's messages into tools that expect JSON logs.
Names in the bundleCLAUDE_GATEWAY_LOG_FORMAT
One source agreesOne thing we can check says the same as this entry.
The name it cites is new in this build
New in this build: CLAUDE_GATEWAY_LOG_FORMAT