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Per-Aspect Settings in Den — a beginner-friendly (simplified English) guide to the host/aspect settings pattern

Per-Aspect Settings in Den — A Beginner-Friendly Guide

Hi! 👋 This guide teaches you a really useful pattern used in a Nix framework called Den. Don't worry if you're new to Nix — we'll explain everything slowly, in plain language, with examples.

Who is this for? Anyone learning about Nix/NixOS who knows a little but isn't an expert yet. If

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Den में Per-Aspect Settings — शुरुआती लोगों के लिए आसान हिंदी गाइड (Hindi beginner's guide to the host/aspect settings pattern in Den)

Den में Per-Aspect Settings — शुरुआती लोगों के लिए आसान गाइड

नमस्ते! 👋 यह गाइड आपको एक बहुत उपयोगी pattern सिखाएगी जो Den नाम के एक Nix framework में इस्तेमाल होती है। चिंता मत कीजिए अगर आप Nix में नए हैं — हम हर चीज़ को धीरे-धीरे, आसान भाषा में, उदाहरणों के साथ समझाएँगे।

किसके लिए है यह गाइड? उन लोगों के लिए जो Computer Science पढ़ रहे हैं और Nix/NixOS के बारे में थोड़ा-बहुत

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Typed per-aspect settings in Den

A how-to for giving shared aspects per-host knobs. If you build configurations with Den (or any dendritic / aspect-oriented Nix setup), this guide shows how to let an aspect expose a few typed values — a disk device id, a kernel optimization target, a BGP AS number — that each host fills in, without forking the aspect.

It is written to be replicated in your own configuration, not just read as a description of one repo. It has two parts:

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den delivery-edge unification — net behavior changes

Branch feat/entity-gen-schema-port, commits e71860b7..d3c74242 (the delivery-half rewrite: nine ad-hoc delivery mechanisms collapsed into one (S, T, P, M) edge algebra). This document enumerates every net runtime behavior change versus the pre-rewrite baseline, with justification. Spec + plan + deviation ledger live in den-architecture/{specs,plans}/2026-06-12-delivery-edge-unification-*.

TL;DR

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Delivery-edge unification — v1 delivery-half debt elimination

• Date: 2026-06-12
• Status: Design approved (sectioned review with maintainer); pending spec review + implementation plan.
• Scope: den v1 fx-pipeline, delivery/collection half. Full sweep, audit-driven. Public API free to improve, with route/provides retained as shims (see §4).
• Strategic premise: v2/HOAG timing is uncertain — v1 is the product and must be as correct as possible. This completes the stabilization the binding-half decoupling (2026-06-12 core-resolver spec) started: that effort purified who binds what, where emission lands; this one purifies how content reaches instantiation roots.
• Baseline: branch feat/entity-gen-schema-port @ b1619a47 (rebased on vic/den main fe63b4bf), CI 947/947, nix-config parity green.

1. Problem — the delivery half is legacy debt

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Core-resolver host/user decoupling — class-local relationship resolution

• Date: 2026-06-12
• Status: Design approved; not implementable until Phase 0 (carrier census) closes.
• Scope: den v1 (soon-legacy) fx-pipeline. Stabilize and shrink before HOAG so v1↔v2 parity is assertable.
• Triggers: denful/den#609 (host-included homeManager silently delivered only when the aspect is user-parametric) + an audit finding that the core resolver hardcodes host/user/homeManager.

1. Problem

1.1 The bug (denful/den#609)

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Entity-isolation-aware subtree extraction (den core)

Date: 2026-06-11 Status: Design — approved for planning Target: den core (feat/delivered-child-host-lazy, off 4f317c5a which nix-config pins) Unblocks: Task 4 of 2026-06-10-delivered-child-host-foundation-plan.md (cortex-cuda rewire)

Problem

extractSubtreeModules (den nix/lib/aspects/fx/resolve.nix ~215-254) builds a

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Nixidy generic transforms — design

Date: 2026-06-09 Status: Approved design, pre-implementation Repos: github:sini/nixidy (fork, branch feat/crd-native-module or successor), sini/nix-config

Problem

nix-config renders Kubernetes manifests with nixidy, then post-processes the

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Projected hasAspect (v1 patch, HOAG-aligned)

Status: approved (conversational, 2026-06-09). Scope: minimal v1 patch whose semantics match den-v2 HOAG, so it is not throwaway design — only its carrier is.

Problem

user.hasAspect aspectX returns false when aspectX is delivered into the user's scope via provides/policy (e.g. igloo.provides.tux.includes = [ aspectX ]), even though the config genuinely applies. Cause: entity hasAspect

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# Regression: a quirk (pipe) emitted by a SHARED aspect imported on every host
# leaks across host scopes. Quirks are scope-local by default — without an
# explicit pipe.collect policy, host A's consumer must see ONLY host A's emitted
# value. Reported: three hosts each emitting one `persist` entry, but every
# host's collector sees all three merged.
#
# Every existing pipe-scope test emits via DISTINCTLY-named per-host aspects
# (den.aspects.igloo, den.aspects.iceberg). This exercises the uncovered path:
# one shared aspect emitting the same pipe on multiple host scopes.
{ denTest, lib, ... }: