---
id: LANG-25
family: GR-LANG
level: extended
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/gr-lang/lang-25
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# LANG-25 — Shaper sentinels resolve before any engine is consulted

*GR-LANG (Part I) · level: extended · profiles: runtime · added in 1.0*

## The rule

> **Normative.** This is the rule.
>
> 1. A shaper source is checked for sentinels before its engine is consulted.
>
> 2. `_NOW_` yields the current timestamp in ISO 8601 form; `_NULL_` yields null; `_EMPTY_ARRAY_` yields the empty list; `_EMPTY_OBJECT_` yields the empty object; and a source prefixed `_LITERAL:` yields the rest of the string verbatim.
>
> 3. A source that does reach the engine and fails there fails the node, and the failure names the source expression and the engine.

## Related rules

- Names: LANG-29
- Referenced by: LANG-29

---

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.