Weighted canaries for server-rendered modes require affinity

If a server-rendered page chooses a process-wide mode and later requests use relative same-origin routes, an independent per-request split across differently configured services is invalid. A page rendered under one mode can send a later request to an incompatible instance.

Use sticky browser or session cohorts, or deterministic flow-keyed edge routing. Measure the canary percentage over eligible sessions or flows rather than raw HTTP requests. Separate services require an upstream router and release parity across both services.