Rule Priority

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Rule Priority and Execution Order

Bifrost rule execution follows two principles.

1. Routing rules are exclusive: the first matched routing rule wins. Among forwarding targets, host-family operations (host/xhost/http/https/ws/wss) win over proxy by protocol precedence, regardless of file order.
2. Modification rules can merge: operations on different fields combine. For duplicate keys the behavior is protocol-specific (see below).

www.example.com host://server1.local
www.example.com host://server2.local

The request goes to server1.local because the first routing rule wins.

Duplicate-key merge semantics differ by protocol:

• reqHeaders / resHeaders: first occurrence wins — a later rule with the same header key is ignored (e.g. X-Custom=value1 then X-Custom=value2 yields value1).
• reqCookies / urlParams: last occurrence wins for the same key.
• reqBody / resBody / resCors: last matching rule overwrites earlier ones.
• statusCode: single-match — the first matching rule applies and later statusCode rules are ignored.

Note: the emitted order of merged urlParams is not guaranteed to follow definition order.