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frontend: guard hive-menu/hive-agent-menu connectedCallback against reconnect

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Fixes hyperhive#2893: 'Element.attachShadow: Unable to re-attach to
existing ShadowDOM', crashing swarm.js's live-update render path.

A custom element's connectedCallback fires again on a same-document
*move* (insertBefore/append repositioning an already-connected node
runs the removal + insertion steps for its whole subtree), not just
on a fresh mount. swarm.js's row-fingerprint cache reuses + reorders
existing <li> subtrees on live updates -- reordering an unchanged,
cached row moves its already-initialised <hive-agent-menu>/<hive-menu>
without ever really detaching it from the document, so connectedCallback
re-runs full setup on an instance that's already set up. attachShadow()
throws unconditionally if the host already has a shadow root, and
HiveAgentMenu's unconditional child-menu creation would have appended a
second <hive-menu> on top of the first, doubling the dropdown, once the
shadow-attach crash itself was out of the way.

Both connectedCallbacks now bail early if already initialised
(shadowRoot present / _menu already built). Reproduced the crash and
duplicate-menu bug with an unguarded control copy of both files driven
via headless Chromium (simulating the exact row-reorder move), then
confirmed the guarded version throws nothing, keeps the same shadowRoot
object identity across the move, and doesn't duplicate the dropdown.
This commit is contained in:
iris 2026-08-01 01:38:45 +02:00 • committed by mara
commit 38aa5f77f4
2 changed files with 17 additions and 0 deletions
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7
frontend/packages/dashboard/src/agent-menu/hive-agent-menu.js
View file

@ -49,6 +49,13 @@ async function agentMenuPost(actionPath, name, body, graceful) {
class HiveAgentMenu extends HTMLElement {
connectedCallback() {
// Same reconnect-without-detach hazard as <hive-menu> (see its
// connectedCallback comment) — swarm.js's row cache can move an
// already-built <li> subtree without a real detach. Without this
// guard a reconnect would append a second <hive-menu> on top of the
// first, doubling the dropdown.
if (this._menu) return;
const { c, forgeBase } = this._opts || {};
const btn = el('button', {

10
frontend/packages/shared/src/hive-menu/hive-menu.js
View file

@ -65,6 +65,16 @@ document.addEventListener('keydown', (e) => {
class HiveMenu extends HTMLElement {
connectedCallback() {
// A custom element's connectedCallback fires again on a same-document
// *move* (insertBefore/append repositioning an already-connected node
// runs the removal + insertion steps for its whole subtree), not just
// on a fresh mount — swarm.js's row-fingerprint cache reuses/reorders
// existing <li> subtrees, which can move an already-initialised
// <hive-menu> without ever detaching it from the document. Guard
// against re-running setup (attachShadow throws if the host already
// has a shadow root) on that reconnect.
if (this.shadowRoot) return;
const { trigger, content } = this._opts || {};
const root = attachShadowCss(this, hiveMenuCss);