diff --git a/frontend/packages/dashboard/src/common.js b/frontend/packages/dashboard/src/common.js
index 6d34c7a7..7637d161 100644
--- a/frontend/packages/dashboard/src/common.js
+++ b/frontend/packages/dashboard/src/common.js
@@ -6,6 +6,7 @@
 import { linkify as termLinkify } from '@hive/shared/terminal.js';
 import { el } from '@hive/shared/dom.js';
 import '@hive/shared/side-panel.js'; // registers <hive-side-panel> — side-effect import
+import '@hive/shared/hive-warn.js'; // registers <hive-warn> — side-effect import
 import DOMPurify from 'dompurify';
 
 // ─── helpers ────────────────────────────────────────────────────────────
diff --git a/frontend/packages/dashboard/src/core.js b/frontend/packages/dashboard/src/core.js
index 3f056d6c..f0bc9e8f 100644
--- a/frontend/packages/dashboard/src/core.js
+++ b/frontend/packages/dashboard/src/core.js
@@ -50,7 +50,7 @@ function renderTombstones(s) {
   // Wording is deliberately about what the list *is* rather than what it
   // isn't: nothing records a destroy, so "container absent" is the only thing
   // the backend can actually tell.
-  const warn = el('p', { class: 'tombstone-warn' });
+  const warn = el('hive-warn', {});
   warn.append(
     el('strong', {}, 'shows every agent whose container is absent'),
     ' — not only destroyed ones. An agent part-way through being spawned ' +
diff --git a/frontend/packages/dashboard/src/credentials.css b/frontend/packages/dashboard/src/credentials.css
index fc1a9f13..becd1d94 100644
--- a/frontend/packages/dashboard/src/credentials.css
+++ b/frontend/packages/dashboard/src/credentials.css
@@ -27,15 +27,6 @@ body.cred-shell {
 
 .cred-pane[hidden] { display: none; }
 
-.cred-warning {
-  border: 1px solid var(--amber);
-  border-radius: 4px;
-  padding: 0.7rem 0.9rem;
-  margin: 0.6rem 0 1.1rem;
-  font-size: 0.9rem;
-  background: color-mix(in srgb, var(--amber) 10%, transparent);
-}
-
 .gh-status { margin: 0.5rem 0 1.2rem; }
 .gh-status-line {
   display: flex;
diff --git a/frontend/packages/dashboard/src/credentials.html b/frontend/packages/dashboard/src/credentials.html
index c30ac25a..98042d12 100644
--- a/frontend/packages/dashboard/src/credentials.html
+++ b/frontend/packages/dashboard/src/credentials.html
@@ -90,7 +90,7 @@
          Security-warning banner + a link to generate a PAT. -->
     <section class="cred-pane" id="cred-pane-github" data-tab-pane="github"
              role="tabpanel" aria-labelledby="cred-tab-github" hidden>
-      <div class="cred-warning">
+      <hive-warn>
         ⚠ use a <strong>dedicated bot account</strong>, not a human's &mdash;
         and a <strong>minimally-scoped</strong> personal access token (only
         the repos/scopes the agent actually needs, e.g. <code>repo</code> +
@@ -98,7 +98,7 @@
         anything within the token's scopes is reachable if the agent is
         ever compromised. the token is injected into the agent's state dir
         and is <strong>never displayed back</strong> on this page.
-      </div>
+      </hive-warn>
 
       <h3>◇ status</h3>
       <div id="gh-status" class="gh-status"><p class="meta">select an agent to see its github credential status.</p></div>
diff --git a/frontend/packages/dashboard/src/dashboard.css b/frontend/packages/dashboard/src/dashboard.css
index 4bfa11c7..8615b003 100644
--- a/frontend/packages/dashboard/src/dashboard.css
+++ b/frontend/packages/dashboard/src/dashboard.css
@@ -444,33 +444,14 @@ hive-agent-menu {
 }
 .container-row.tombstone .name { color: var(--muted); }
 
-/* K3PT ST4T3 caveat. Amber, not red like `.port-conflict`, and no pulse: this
-   is a standing "read the list this way" note, not an incident — a pulsing
-   banner that is always present just teaches you to stop seeing it.
-   Nothing records a destroy, so this list is every agent whose container is
-   absent — which includes one being spawned right now. */
-.tombstone-warn {
-  background: color-mix(in srgb, var(--amber) 8%, transparent);
-  border: 1px solid var(--amber);
-  color: var(--amber);
-  padding: 0.5em 0.8em;
-  margin-bottom: 0.6em;
-  border-radius: 4px;
-}
-.tombstone-warn strong { color: var(--amber); }
+/* K3PT ST4T3 caveat and the port-collision banner both moved to the
+   shared <hive-warn> component — amber/no-pulse for
+   the standing caveat (a pulsing banner that's always present just
+   teaches you to stop seeing it), `severity="red" pulse` for the port
+   collision (an incident, not a caveat). See core.js/swarm.js and
+   hive-warn.css for the actual styling now.
 
-/* Notification controls — sit between the banner and the containers. */
-.port-conflict {
-  background: color-mix(in srgb, var(--red) 8%, transparent);
-  border: 1px solid var(--red);
-  color: var(--red);
-  padding: 0.5em 0.8em;
-  margin-bottom: 0.6em;
-  border-radius: 4px;
-  text-shadow: 0 0 6px color-mix(in srgb, var(--red) 40%, transparent);
-  animation: questions-pulse 2.4s ease-in-out infinite;
-}
-.port-conflict strong { color: var(--red); }
+   Notification controls below sit between the banner and the containers. */
 
 /* Build-queue summary banner on the SW4RM tab: one compact line
    when the rebuild queue has active work, with a link to the full queue on
diff --git a/frontend/packages/dashboard/src/swarm.js b/frontend/packages/dashboard/src/swarm.js
index 120313bb..6dbcf1a9 100644
--- a/frontend/packages/dashboard/src/swarm.js
+++ b/frontend/packages/dashboard/src/swarm.js
@@ -582,7 +582,7 @@ export function renderContainers(s) {
   // rebuild. The banner sits above the agent list so it's the
   // first thing the operator sees when something's wedged.
   if (portConflicts.length) {
-    const banner = el('div', { class: 'port-conflict' },
+    const banner = el('hive-warn', { severity: 'red', pulse: '' },
       el('strong', {}, '⚠  port collision'), ' — ');
     const groups = portConflicts.map((c) =>
       `:${c.port} (${c.agents.join(' + ')})`).join('; ');
diff --git a/frontend/packages/shared/package.json b/frontend/packages/shared/package.json
index 01b05a6f..478a1cf2 100644
--- a/frontend/packages/shared/package.json
+++ b/frontend/packages/shared/package.json
@@ -22,6 +22,7 @@
     "./modal.js": "./src/modal.js",
     "./shadow-css.js": "./src/shadow-css.js",
     "./hive-menu.js": "./src/hive-menu/hive-menu.js",
+    "./hive-warn.js": "./src/hive-warn/hive-warn.js",
     "./side-panel.js": "./src/side-panel/hive-side-panel.js",
     "./jobq-graph.js": "./src/jobq-graph/hive-jobq-graph.js"
   },
diff --git a/frontend/packages/shared/src/hive-warn/hive-warn.css b/frontend/packages/shared/src/hive-warn/hive-warn.css
new file mode 100644
index 00000000..74952b2e
--- /dev/null
+++ b/frontend/packages/shared/src/hive-warn/hive-warn.css
@@ -0,0 +1,49 @@
+/* hive-warn.css — shadow-DOM stylesheet for the <hive-warn> autonomous
+   custom element (hive-warn.js). `severity` is an attribute on the HOST
+   (how callers set it, `hive-warn.js`'s own header explains why) —
+   `:host([severity="…"])` sets `color`/`border-color`/`background`,
+   which the shadow content then inherits/reads via `currentColor`, same
+   pattern as hive-btn.css's `[variant]`. Default (no `severity` set) is
+   amber — the more common case among the three call sites this replaces.
+
+   Tint is a single canonical 8% for both severities — `.cred-warning`
+   (the amber call site) was independently written at 10%, `.tombstone-warn`
+   at 8%; picking one number is the whole point of this component
+   existing (mara, on review: "so they are all themed consistently"). */
+
+:host {
+  display: block;
+  border: 1px solid var(--amber);
+  border-radius: 4px;
+  padding: 0.5em 0.8em;
+  margin-bottom: 0.6em;
+  color: var(--amber);
+  background: color-mix(in srgb, var(--amber) 8%, transparent);
+}
+:host([severity="red"]) {
+  border-color: var(--red);
+  color: var(--red);
+  background: color-mix(in srgb, var(--red) 8%, transparent);
+}
+
+/* `pulse`: opt-in, for "something is wrong right now" rather than a
+   standing caveat — deliberately not the default. A banner that's
+   always present and always pulsing just trains you to stop seeing it
+   (the reasoning on the original `.tombstone-warn`, which stays
+   non-pulsing; `.port-conflict → severity="red" pulse` is the one
+   call site that wants it). `currentColor` throughout so the glow
+   matches whichever severity is active without a second color switch. */
+:host([pulse]) {
+  text-shadow: 0 0 6px color-mix(in srgb, currentColor 40%, transparent);
+  animation: hive-warn-pulse 2.4s ease-in-out infinite;
+}
+@keyframes hive-warn-pulse {
+  0%, 100% { box-shadow: 0 0 12px -4px color-mix(in srgb, currentColor 55%, transparent); }
+  50%      { box-shadow: 0 0 22px -2px color-mix(in srgb, currentColor 95%, transparent); }
+}
+
+/* Explicit rather than relying on plain inheritance — matches what
+   every one of the three original rules declared, kept for parity. */
+::slotted(strong) {
+  color: inherit;
+}
diff --git a/frontend/packages/shared/src/hive-warn/hive-warn.js b/frontend/packages/shared/src/hive-warn/hive-warn.js
new file mode 100644
index 00000000..7fbf9aa2
--- /dev/null
+++ b/frontend/packages/shared/src/hive-warn/hive-warn.js
@@ -0,0 +1,37 @@
+// hive-warn.js — <hive-warn>, the shared inline warning-banner
+// component. Consolidates three independently-written instances of the
+// same thing: `.cred-warning` (credentials.html, static
+// markup), `.tombstone-warn` (core.js, JS-built), `.port-conflict`
+// (swarm.js, JS-built) — the first two differed only by an
+// undeliberate 10% vs 8% tint, the strongest evidence this was drift,
+// not three genuinely different needs.
+//
+// Purely presentational — no internal state, no lifecycle beyond
+// attaching its shadow root once. `severity` ('amber' | 'red', default
+// amber) and `pulse` (boolean) are read directly by hive-warn.css's
+// `:host([...])` selectors; unlike `<hive-btn>`'s `variant`/`disabled`
+// there's no inner native element that needs the attribute mirrored
+// onto it, so no `attributeChangedCallback` is needed at all.
+//
+// Content is arbitrary light-DOM children through the shadow tree's
+// single default `<slot>` — same reuse of the existing `<strong>`/
+// `<code>` markup every call site already writes, no caller-side
+// rewrite of their message content needed.
+//
+// Usage:
+//   `<hive-warn>...</hive-warn>`                    (amber, static HTML)
+//   `el('hive-warn', {}, ...)`                       (amber, JS-built)
+//   `el('hive-warn', { severity: 'red', pulse: '' }, ...)` (urgent)
+
+import { attachShadowCss } from '../shadow-css.js';
+import hiveWarnCss from './hive-warn.css';
+
+class HiveWarn extends HTMLElement {
+  connectedCallback() {
+    if (this._built) return; // re-parenting re-fires connectedCallback
+    const root = attachShadowCss(this, hiveWarnCss);
+    root.append(document.createElement('slot'));
+    this._built = true;
+  }
+}
+customElements.define('hive-warn', HiveWarn);