Tree

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<div class="hm-measure">
  <div class="tree" data-tree>
    <details class="tree-node" open>
      <summary class="tree-summary"><span class="tree-label">Engineering</span><span class="tree-count">2</span></summary>
      <div class="tree-children">
        <details class="tree-node">
          <summary class="tree-summary"><span class="tree-label">Platform</span><span class="tree-count">1</span></summary>
          <div class="tree-children">
            <div class="tree-leaf"><span class="tree-label">Build tooling</span></div>
          </div>
        </details>
        <details class="tree-node">
          <summary class="tree-summary"><span class="tree-label">Design systems</span><span class="tree-count">1</span></summary>
          <div class="tree-children">
            <div class="tree-leaf"><span class="tree-label">Tokens</span></div>
          </div>
        </details>
      </div>
    </details>
  </div>
</div>

Server exchange

This Hyperpart has no server exchange — it is presentation or client chrome only. htmx does not issue a request on this part's behalf. If you put an affordance (hx-*) on a control that uses this markup, that action's exchange belongs to the action, not this part. See Swap contract for host-owned envelopes.

Swap contract

Agent-visible HTMX topology (ADR-0054 / decision 0012). exchange envelope = what the response may re-emit relative to the persistent slot (body_only | outer | none | host_owned | document). dual-lock validates part markup only — not this envelope. Stem: stems/morph-safe-hypermedia.md; decision: docs/decisions/0012-swap-identity-contract.md.

No host HTMX exchange on this part — presentation or client chrome only. exchange envelope: n/a.

If a host wraps this markup in hx-*, that host owns the swap contract (sole identity + envelope). Prefer innerMorph / outerMorph for stable slots; replacement for flash; body-only responses under inner swaps.

Envelope response examples

This part has no owned exchange (envelope n/a). If a host adds hx-*, that host’s envelope applies — typically body_only:

<!-- Host wraps this presentation part with hx-* (host owns envelope) -->
<!-- Prefer: hx-swap="innerMorph" hx-target="#panel-body" -->
<!-- Server returns body_only interior for #panel-body -->
<div class="dz-stack">content…</div>

Do not re-own the slot:

<!-- WRONG: server returns the presentation root with a new id every poll -->
<div id="tree-root" data-dz-region>…</div>

How to use it

Seams

• `[data-tree]` / `.tree` forest root (dual-lock)
• `details.tree-node` + `summary.tree-summary` for branches (label + count only; chevron is CSS)
• `.tree-leaf` for nodes with no children

Do / Don't

Pitfalls

• Do not put chevron SVG/span in the summary — disclosure chrome belongs in CSS (::before on branches)
• Do not wrap leaves in empty <details> — that still shows a rotating arrow UX with nothing to expand
• Do not ship exclusive-open or name= exclusivity on tree peers
• Gallery may mount a second forest under .hm-contract-live__preview — interaction checks use .hm-preview only
• Not menubar/nav chrome — no outside-dismiss controller

Keyboard / AT

• Native details/summary expand/collapse
• Keyboard: Enter/Space on summary

DOM contract

What the emitted HTML must satisfy — the table is the required surface; Python under contracts/ is the package-internal dual-lock CI runs (tests/test_contracts.py), not an app route. Standalone HTMX4: implement the API so responses match this markup. Dazzle: the agent emits SSR that already satisfies it. Do not invent attrs outside these tables. For request/response wiring see Server exchange.

contracts/tree.py

Required in the DOM: root [data-tree] (part tree). Emit only these attributes — inventing extras is fine only if controllers ignore them; omitting required ones fails CI (tests/test_contracts.py).

Ingestion model Tree

Server-side shape before render — one normalisation boundary for producers.

Exemplar render()

Executable in CI: the Python below is render(); the boxed preview is render(EXEMPLARS[0]) — the first fixture the dual-lock tests emit, not a separate widget and not gallery mock data.

def render(t: Tree) -> str:
    """Model → tree region root."""
    return f'<div class="dz-tree" data-dz-tree>{t.body_html}</div>'

Notes

Source files

Canonical registration in the registry. No dedicated controller — CSS for this part lives in the layered bundle.

site/registry.py · contracts/tree.py