---
id: BR-4
family: RT-BR
level: core
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/rt-br/br-4
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# BR-4 — An outcome matching no branch is loud, never a silent gate-off

*RT-BR (Part II) · level: core · profiles: runtime · added in 1.0*

A gateway whose configured branches do not cover the value it produced used to emit a branch name no port carried, gating off everything downstream with nothing said. The target is that this cannot happen quietly.

## The rule

> **Normative.** This is the rule.
>
> 1. A gateway's branch authority is its configured branches, each an entry pairing a name with a value; an entry whose name is not a non-empty string is discarded before any matching.
>
> 2. Matching an outcome to a branch is type-aware and never a loose cast: a boolean outcome matches only a branch whose configured value denotes a boolean: a boolean, the integer `0` or `1`, or the strings `true`, `false`, `1` or `0` without regard to case.
>
> 3. Two strings compare without regard to case, and anything else must be equal in both type and value.
>
> 4. A gateway must not emit a branch name that no port of the node carries: where no configured branch matches the outcome, either the gateway declares a default branch port that receives it, or the node fails with an error output that an error edge can route (ERR-7).

## Why

Recorded under OPEN-15.

## Related rules

- Names: BR-2, BR-3
- Referenced by: BR-2

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.