constitution firewall

specs/001-ai-docs/research.md

@@ -54,3 +54,8 @@
 - **Decision**: Standardize Nix structure so single-child attribute sets are flattened into dotted attrpaths, siblings that share a parent are merged into one nested attribute set, simple leaf assignments appear before nested attribute sets, `inherit` statements appear first within a set, boolean leaves appear before other leaves, and module bodies place `options` before `config`.
 - **Rationale**: This keeps modules scan-friendly, reduces unnecessary indentation, and makes the high-signal contract (`options`) appear before implementation (`config`) consistently across the repo.
 - **Alternatives considered**: (a) Leave structure to formatter defaults only (rejected: formatters do not enforce these semantic grouping rules); (b) prefer fully flattened attrpaths everywhere (rejected: harms readability once a parent has multiple children); (c) keep `config` before `options` when it was written first (rejected: makes module interfaces harder to scan).
+
+## Decision 12 (2026-04-01): Host-local firewall files
+- **Decision**: Any host that owns firewall rules MUST keep firewall-related logic in `hosts/<name>/firewall.nix`, with `hosts/<name>/configuration.nix` importing that file rather than accumulating the firewall logic inline.
+- **Rationale**: Firewall behavior is a distinct host concern that becomes hard to review and maintain when mixed into general host assembly. A dedicated `firewall.nix` preserves ownership boundaries and makes networking changes easier to audit.
+- **Alternatives considered**: (a) Keep firewall rules inline in `configuration.nix` (rejected: mixes host assembly with a dense, security-sensitive subsystem); (b) centralize all firewall logic under `modules/network/` (rejected: hides host-specific rule ownership and deployment context).