Overview

Native rule packs are complete, Fensu-shipped policies for a particular framework or architecture. They run in Rust like core rules, but stay out of the catalogue until a repository explicitly activates them.

Use a native pack when Fensu ships an architecture policy that should replace the generic core policy for that kind of repository. Packs can combine framework-specific rules with transparent aliases of compatible core or pack rules, presenting one coherent namespace for selection, diagnostics, and generated skills.

Activation and selection

Pack activation and rule selection are separate:

rule_packs = ["dagster"]
select = ["FPDG"]

• rule_packs controls which shipped catalogues are available.
• select, warn, and ignore assign available pack identities to policy tiers.
• Activating a pack does not select it.
• A pack selector matches no identities until its pack is activated.
• Pack names must be registered and unique.

This separation lets a repository activate a catalogue while selecting one rule, one family of aliases, or the complete policy. The exact selectors belong to each pack’s reference page.

Codes and namespaces

Fensu reserves FP for shipped native packs. Each pack owns a namespace beneath that prefix. The Dagster, Rust, TypeScript, and SvelteKit packs own FPDG, FPRS, FPTS, and FPSK.

Pack-native rules append their numeric identity directly, such as FPDG022. Retained core aliases preserve the core family and number after the pack namespace: FFA001 becomes FPDGA001 in the Dagster pack. Pack-to-pack aliases follow the same rule: FPTSA001 becomes FPSKA001 in the standalone SvelteKit pack.

An alias executes the canonical native implementation while diagnostics retain the selected pack identity and disclose provenance:

FPDGA001 (alias FFA001)  function parameter 'value' must define a type annotation

The canonical code and its alias cannot occupy the same tier because that would select one implementation twice. Fensu rejects the overlap instead of emitting duplicate diagnostics.

Native execution

Pack-native rules and retained aliases execute without starting Python. They use the same deterministic discovery, caching, warning, ignore, exception, and output machinery as core rules.

Activating a native pack by itself does not require a Python interpreter. A project that also configures rule_paths, rule_modules, or custom-rule options still uses the custom-rule metadata host for those custom rules.

fensu rule shows Kind: pack, the owning pack, and any canonical alias target for an activated identity.

Available packs

Dagster

A standalone Dagster repository architecture with 23 native policies and 101 retained core aliases.

TypeScript and SvelteKit

Framework-independent TypeScript policy and a standalone SvelteKit policy with transparent TypeScript aliases.

Rust

Native Cargo workspace analysis with 117 layout, dependency, naming, shape, hygiene, and test-convention rules.