feat: port entity schema to gen-schema

CLAUDE.md

@@ -17,7 +17,7 @@ nix/                       — all library and flake-module code
         aspect/            — children, normalize, provide
         policy/            — policy dispatch and effects
     entities/              — host.nix, home.nix entity kind definitions
-    diag/                  — diagram generation (c4, mermaid, dot, fleet views)
+    diag/capture.nix       — trace capture (graph/rendering moved to denful/den-diagram)
   nixModule/               — den.aspects, den.policies, den.lib option declarations
 modules/                   — NixOS-module-style option declarations and batteries
   options.nix              — den.hosts, den.homes, den.schema, den.classes, den.quirks
@@ -129,6 +129,35 @@ New test files must be `git add`'d before nix can evaluate them. Use `--override
 
 - **den-debugging** (`.claude/skills/den-debugging.md`) — structured workflow for reproducing, isolating, and fixing bugs. Guides through: understand report → trace code path → write failing test → fix → validate. Includes an entry point table mapping symptoms to source files.
 
+## Diagrams (den-diagram)
+
+Diagram rendering lives in a separate repo: [denful/den-diagram](https://github.com/denful/den-diagram). Den keeps only the capture layer (`nix/lib/diag/capture.nix`) which runs the fx pipeline with tracing handlers.
+
+**Capture** stays in den — `den.lib.capture.*`:
+
+- `capture`, `captureAll`, `captureWithPaths`, `captureWithPathsWith`, `captureFleet`
+
+**Rendering** lives in den-diagram — added as `inputs.den-diagram` in templates that need it:
+
+```nix
+diagram = inputs.den-diagram.lib;
+
+# Two-step: capture in den, render in den-diagram
+captured = den.lib.capture.captureWithPathsWith {
+  classes = [ "nixos" "homeManager" ];
+  root = den.lib.resolveEntity "host" { inherit host; };
+  ctx = { inherit host; };
+};
+g = diagram.context {
+  entries = captured.entries;
+  ctxTrace = captured.ctxTrace;
+  name = host.name;
+};
+rendered = diagram.toMermaid g;
+```
+
+Templates using den-diagram: `diagram-demo`, `fleet-demo`. Den's core flake and CI have no den-diagram dependency.
+
 ## Debugging and tracing
 
 For pipeline debugging, use `builtins.trace` temporarily to inspect values flowing through handlers:

README.md

@@ -13,7 +13,7 @@
 
 **Write a feature once. Run it on every host, user, and platform you have — and share it with anyone, flake or not.**
 
-Den turns Nix configuration into composable **features** instead of per-host piles of modules. A Den *aspect* is a plain function: give it context (your hosts and users) and it returns configuration for every Nix class it touches — `nixos`, `darwin`, `homeManager`, `hjem`, or a class you invent.
+Den turns Nix configuration into composable **features** instead of per-host piles of modules. A Den _aspect_ is a plain function: give it context (your hosts and users) and it returns configuration for every Nix class it touches — `nixos`, `darwin`, `homeManager`, `hjem`, or a class you invent.
 
 ```nix
 # An aspect is a function of context that returns
@@ -33,8 +33,8 @@ That one idea — **a feature as a function** — is what makes the rest possibl
 ## What Den makes possible
 
 - **One feature, everywhere, in one place.** Stop scattering a single concern across separate `nixos`, `darwin`, and `homeManager` files. An aspect holds all of it together.
-- **Reuse across hosts, users — and across projects.** Share aspects between machines, between people, and between *flake and non-flake* setups, without forcing everyone to download each other's inputs.
-- **No `mkIf` / `enable` clutter.** The shape of the context *is* the condition — a function that asks for `{ host, user }` simply doesn't run where there's no user. Conditionals disappear.
+- **Reuse across hosts, users — and across projects.** Share aspects between machines, between people, and between _flake and non-flake_ setups, without forcing everyone to download each other's inputs.
+- **No `mkIf` / `enable` clutter.** The shape of the context _is_ the condition — a function that asks for `{ host, user }` simply doesn't run where there's no user. Conditionals disappear.
 - **Hosts shape their users, users shape their hosts.** Cross-entity configuration flows both ways, without coupling them together.
 - **Add a capability in one line; remove it by deleting that line.** Hosts just pick the aspects they want.
 - **Bring your own classes and whole pipelines.** Custom Nix classes, machine fleets, MicroVM guests, terranix, standalone neovim — if you can walk it as data, Den can configure it.
@@ -43,10 +43,10 @@ That one idea — **a feature as a function** — is what makes the rest possibl
 
 Four concepts, one job each:
 
-- **Entity** — *what exists*: a host, user, or home.
-- **Aspect** — *what it does*: a feature, spanning Nix classes.
-- **Policy** — *how entities relate*: topology and routing between them.
-- **Quirk** — *structured data aspects share*, without coupling.
+- **Entity** — _what exists_: a host, user, or home.
+- **Aspect** — _what it does_: a feature, spanning Nix classes.
+- **Policy** — _how entities relate_: topology and routing between them.
+- **Quirk** — _structured data aspects share_, without coupling.
 
 **Feature-first, not host-first.** Traditional setups start from hosts and push modules down; Den [flips that](https://den.denful.dev/explanation/core-principles/) — features are primary, hosts just select them.
 
@@ -75,11 +75,13 @@ nix run github:denful/den
 ## [Documentation](https://den.denful.dev)
 
 **Start here**
+
 - [From Zero to Den](https://den.denful.dev/guides/from-zero-to-den/)
 - [From Flake to Den](https://den.denful.dev/guides/from-flake-to-den/)
 - [Core Principles](https://den.denful.dev/explanation/core-principles/)
 
 **Go further**
+
 - [Custom Nix Classes](https://den.denful.dev/guides/custom-classes/)
 - [Homes Integration](https://den.denful.dev/guides/home-manager/)
 - [Batteries](https://den.denful.dev/guides/batteries/)
@@ -89,6 +91,7 @@ nix run github:denful/den
 - [Tests as Code Examples](https://den.denful.dev/tutorials/ci/)
 
 **Project**
+
 - [Motivation](https://den.denful.dev/motivation/)
 - [Versioning](https://den.denful.dev/releases/)
 - [Community](https://den.denful.dev/community/)

checkmate/modules/formatter.nix

@@ -6,6 +6,7 @@
     "docs/*"
     "Justfile"
     "AGENT*.md"
+    "CLAUDE.md"
     "*.txt"
     "*.svg"
     "ci.bash"

docs/astro.config.mjs

@@ -178,7 +178,7 @@ export default defineConfig({
 						{ label: 'den.policies', slug: 'reference/policies' },
 						{ label: 'den.lib', slug: 'reference/lib' },
 						{ label: 'den.lib', slug: 'reference/lib-deprecated', badge: { text: 'legacy', variant: 'note' } },
-						{ label: 'den.lib.diag', slug: 'reference/diag' },
+						{ label: 'den.lib.capture & den-diagram', slug: 'reference/diag' },
 						{ label: 'flake.*', slug: 'reference/output' },
 						{ label: 'Glossary', slug: 'reference/glossary' },
 					],

docs/src/content/docs/explanation/diagrams.mdx

@@ -1,12 +1,13 @@
 ---
 title: Diagrams
-description: Visualizing aspect resolution graphs with den.lib.diag.
+description: Visualizing aspect resolution graphs with den-diagram.
 ---
 
 import { Aside } from '@astrojs/starlight/components';
 
 <Aside title="Source" icon="github">
-[`nix/lib/diag/`](https://github.com/denful/den/tree/main/nix/lib/diag)
+Capture: [`nix/lib/diag/capture.nix`](https://github.com/denful/den/blob/main/nix/lib/diag/capture.nix)
+Rendering: [`denful/den-diagram`](https://github.com/denful/den-diagram)
 </Aside>
 
 ## What it does

docs/src/content/docs/guides/debug.md

@@ -58,15 +58,21 @@ This returns a set of matching policies with their targets, routing type, and so
 
 ## Trace Aspect Includes
 
-The resolution pipeline includes built-in tracing via the `diag` library.
-Use `den.lib.diag.hostContext` to capture a full trace of which aspects are
-included and how they resolve. See [Diagrams](/explanation/diagrams/) for details.
+The resolution pipeline includes built-in tracing via `den.lib.capture` and the
+[den-diagram](https://github.com/denful/den-diagram) library. Capture trace data
+in den, then render with den-diagram. See [Diagrams](/explanation/diagrams/) for details.
 
 ```nix
-# In a REPL:
-diag = den.lib.diag
-g = diag.hostContext { host = den.hosts.x86_64-linux.laptop; }
-diag.toMermaid g  # renders the full aspect graph
+# In a REPL (with den-diagram available as `diagram`):
+diagram = inputs.den-diagram.lib;
+host = den.hosts.x86_64-linux.laptop;
+captured = den.lib.capture.captureWithPathsWith {
+  classes = [ "nixos" "homeManager" ];
+  root = den.lib.resolveEntity "host" { inherit host; };
+  ctx = { inherit host; };
+};
+g = diagram.context { entries = captured.entries; name = host.name; };
+diagram.toMermaid g  # renders the full aspect graph
 ```
 
 ## Trace Context

docs/src/content/docs/overview.mdx

@@ -74,7 +74,7 @@ Option namespaces and library functions.
   <LinkCard title="den.policies" href="/reference/policies/" description="Policy effects, combinators, and built-in policies." />
   <LinkCard title="den.ctx (compat)" href="/explanation/context-system/" description="Legacy compatibility shim." />
   <LinkCard title="den.lib" href="/reference/lib/" description="Core library: aspect resolution, __findFile, policy constructors, nh wrappers." />
-  <LinkCard title="den.lib.diag" href="/reference/diag/" description="Diagram generation and graph introspection." />
+  <LinkCard title="den.lib.capture" href="/reference/diag/" description="Trace capture for diagram rendering (see den-diagram)." />
   <LinkCard title="flake.*" href="/reference/output/" description="Output generation and instantiation." />
   <LinkCard title="Glossary" href="/reference/glossary/" description="Definitions for Den-specific terms." />
 </CardGrid>