--server-max-concurrency

Caps the number of renders running at once. The server renders one request at a time by default — each in-flight request is a full browser instance, so this floor keeps load from exhausting the host. With an Enterprise license the default rises to the CPU count, logged at info level on startup. A request that arrives while the cap is full gets 429, unless --server-queue-requests is set to hold it. The value must be at least 1.

Set this to match the CPU and memory a host can give concurrent browser instances. The default floor of 1 applies below Enterprise tier; setting this flag is an Enterprise-tier capability.