swarm-ui: move dynamic agent-term tabs into the top nav bar

mara, PR review: "the dynamic tab should be in the top bar, not a new
one below". Moves the .shell-tabs group from its own sticky row under
the header into .shell-nav itself, right after the nav indicator.

Also adds a third re-measure effect for the sliding nav indicator,
keyed on tabs.length: with tabs inline in the same flex row the
indicator measures, closing a background tab (no navigation) can
shrink the row without the hop effect's own re-measure ever firing.
Same reflow-not-navigation reasoning as the existing resize-listener
effect.

frontend/packages/shared/src/icons.tsx

@@ -57,6 +57,32 @@ export function LinkIcon() {
   );
 }
 
+// Four corner-arrows, the standard "expand to fullscreen" glyph — added
+// for the terminal-preview-to-full-tab trigger (`AgentTermPreview`'s own
+// expand affordance). Same size/stroke recipe as `LinkIcon`/`GearIcon`
+// above, not a smaller variant like `FilterIcon` — this one sits as a
+// standalone `Badge` trigger, not inside a table header cell.
+export function ExpandIcon() {
+  return (
+    <svg
+      width="1.3em"
+      height="1.3em"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      stroke-width="2"
+      stroke-linecap="round"
+      stroke-linejoin="round"
+      aria-hidden="true"
+    >
+      <polyline points="15 3 21 3 21 9" />
+      <polyline points="9 21 3 21 3 15" />
+      <line x1="21" y1="3" x2="14" y2="10" />
+      <line x1="3" y1="21" x2="10" y2="14" />
+    </svg>
+  );
+}
+
 // A funnel, the standard "filter" glyph — smaller than the other two
 // (1em not 1.3em) since its first caller sits inside a table header
 // cell, not a nav trigger button; scale via the caller's own

frontend/packages/swarm-ui/src/App.tsx

@@ -3,6 +3,7 @@
 import { Route, Switch } from "wouter-preact";
 import { Shell } from "./shell/Shell.js";
 import { AgentsPage } from "./pages/agents/AgentsPage.js";
+import { AgentTerminalPage } from "./pages/agents/AgentTerminalPage.js";
 import { ComponentsPage } from "./pages/ComponentsPage.js";
 import { JobsPage } from "./pages/JobsPage.js";
 import { HivesPage } from "./pages/HivesPage.js";
@@ -23,6 +24,7 @@ export function App() {
       <Switch>
         <Route path="/" component={HivesPage} />
         <Route path="/agents" component={AgentsPage} />
+        <Route path="/agents/:name/terminal" component={AgentTerminalPage} />
         <Route path="/jobs" component={JobsPage} />
         <Route path="/issues" component={IssueReportPage} />
         <Route path="/components" component={ComponentsPage} />

frontend/packages/swarm-ui/src/pages/agents/AgentTermPreview.css

@@ -8,14 +8,60 @@
   margin-block-start: 1rem;
 }
 
-.ui-agent-term-preview-status {
+/* Holds the connection-status badge + (unless `fullHeight`) the
+   expand-to-fullscreen trigger — `margin-left: auto` targets the expand
+   trigger by its OWN class, not `:last-child` (tried that first; it
+   silently broke when `fullHeight` hides the expand trigger, since the
+   status badge then becomes the `:last-child` too and gets pushed to
+   the right edge instead of staying flush left — caught by actually
+   rendering the `fullHeight` case, not just reasoning about the CSS).
+   Same split-row intent `Shell.css`'s `.shell-header-actions` already
+   uses for its own pair of triggers, just addressed directly instead of
+   positionally. */
+.ui-agent-term-preview-toolbar {
+  display: flex;
+  align-items: center;
   margin-block-end: 0.5rem;
 }
+.ui-agent-term-preview-expand {
+  margin-left: auto;
+}
 
 .ui-agent-term-preview-wrap.terminal-wrap {
   max-height: 12em;
 }
 
+/* `AgentTerminalPage`'s full-tab mount (`fullHeight` prop → the
+   `-full` modifier on the OUTER `.ui-agent-term-preview` root, not the
+   wrap) — self-contained flex chain, not dependent on the page around
+   it doing anything beyond giving this root a real height to fill (see
+   AgentTerminalPage.css). Column flex so the toolbar keeps its natural
+   height and the terminal-wrap below it takes the rest; `flex: 1` +
+   `min-height: 0` on the wrap (not `height: 100%`) is deliberate — a
+   flex item's `height` percentage doesn't account for a sibling
+   (the toolbar) already consuming space the way `flex: 1` does, and
+   `min-height: 0` is what actually lets the item shrink below its
+   content's natural height so `.live.terminal`'s own `overflow-y: auto`
+   (terminal.css) scrolls instead of the whole column growing past its
+   container. `!important`-free — the `max-height: none` overrides
+   below already carry one more class in the selector than the
+   un-modified rules above (`.ui-agent-term-preview-full` prefixing
+   each), so they're strictly more specific and win regardless of
+   source order. */
+.ui-agent-term-preview-full {
+  display: flex;
+  flex-direction: column;
+}
+.ui-agent-term-preview-full .ui-agent-term-preview-wrap.terminal-wrap {
+  max-height: none;
+  flex: 1;
+  min-height: 0;
+}
+.ui-agent-term-preview-full .ui-agent-term-preview-wrap .live.terminal {
+  max-height: none;
+  height: 100%;
+}
+
 /* `box-sizing: border-box`, not the browser's default `content-box` —
    `.live.terminal`'s own `padding: 0.8em 1em 0.4em` (terminal.css) is
    otherwise added ON TOP of this `max-height`, so the box renders

frontend/packages/swarm-ui/src/pages/agents/AgentTermPreview.tsx

@@ -18,9 +18,28 @@
 // here needs to be interactive. Sourced from `useSwarmAgentStateStream`,
 // not from `AgentRow` — the roster fetch `AgentsPage` already did has no
 // notion of turn_state/model/ctx/cost, only `wanted`/`snapshot.running`.
+// `showHeaderBadges` (default true) exists for a caller that already
+// shows this info elsewhere and wants this cluster suppressed — checked
+// against the original plan for this page, which proposed exactly that
+// for `AgentsPage`'s embedded usage; that page's detail panel turned out
+// NOT to duplicate any of this (`AgentRow`/`AgentTypes.ts` carry none of
+// turn_state/model/ctx/cost), so `AgentsPage` leaves this at its default
+// rather than hiding the only place swarm-ui shows it — see the commit
+// message for the full reasoning. The prop still exists because
+// suppressing it is a real, reusable need in principle, just not here.
+
+// **Expand-to-fullscreen trigger** — opens/navigates to
+// `/agents/:name/terminal` (`AgentTerminalPage`) via `useDynamicTabs`,
+// same header-tab mechanism `Shell`'s own nav row now shares. Lives here
+// (not on `AgentsPage`) so both the embedded preview and the future full
+// page mount the identical trigger without either needing to know where
+// the other one is. Suppressed via `fullHeight` — the full-page mount
+// already IS the destination, so it has nothing further to expand to.
 import { useLayoutEffect, useRef, useState } from "preact/hooks";
 import { Badge, type BadgeTone } from "@hive/shared/badge.js";
+import { ExpandIcon } from "@hive/shared/icons.js";
 import { Row } from "@hive/shared/term-row.js";
+import { useDynamicTabs } from "../../shell/useDynamicTabs.js";
 import {
   useSwarmTermStream,
   type ConnectionState,
@@ -81,13 +100,22 @@ function fmtTokens(n: number): string {
   return String(n);
 }
 
-export function AgentTermPreview({ agentName }: { agentName: string }) {
+export function AgentTermPreview({
+  agentName,
+  showHeaderBadges = true,
+  fullHeight = false,
+}: {
+  agentName: string;
+  showHeaderBadges?: boolean;
+  fullHeight?: boolean;
+}) {
   const { rows, connection } = useSwarmTermStream(
     `/api/agents/${encodeURIComponent(agentName)}/term/stream`,
   );
   const { header } = useSwarmAgentStateStream(
     `/api/agents/${encodeURIComponent(agentName)}/state/stream`,
   );
+  const { open: openTab } = useDynamicTabs();
   const logRef = useRef<HTMLDivElement>(null);
   const [stickToBottom, setStickToBottom] = useState(true);
 
@@ -110,14 +138,36 @@ export function AgentTermPreview({ agentName }: { agentName: string }) {
   }, [rows, stickToBottom]);
 
   return (
-    <div class="ui-agent-term-preview">
+    <div
+      class={
+        "ui-agent-term-preview" +
+        (fullHeight ? " ui-agent-term-preview-full" : "")
+      }
+    >
+      <div class="ui-agent-term-preview-toolbar">
         <Badge
           class="ui-agent-term-preview-status"
           tone={CONNECTION_TONE[connection]}
           value={CONNECTION_LABEL[connection]}
         />
+        {!fullHeight && (
+          <Badge
+            class="ui-agent-term-preview-expand"
+            variant="quiet"
+            icon={<ExpandIcon />}
+            value="expand"
+            title={`open ${agentName}'s terminal in its own tab`}
+            onClick={() =>
+              openTab({
+                href: `/agents/${encodeURIComponent(agentName)}/terminal`,
+                label: agentName,
+              })
+            }
+          />
+        )}
+      </div>
       <div class="terminal-wrap ui-agent-term-preview-wrap">
-        {header && (
+        {header && showHeaderBadges && (
           <div class="ui-agent-term-preview-header-badges">
             <Badge
               tone={TURN_STATE_TONE[header.turn_state] ?? "neutral"}

frontend/packages/swarm-ui/src/pages/agents/AgentTerminalPage.css

@@ -0,0 +1,29 @@
+/* <AgentTerminalPage> — gives `AgentTermPreview`'s `fullHeight` flex
+   chain (`.ui-agent-term-preview-full`, AgentTermPreview.css) something
+   real to fill. `Shell.css`'s `.shell-body` has no fixed height of its
+   own (it's a plain flow column sized by content), so without an
+   explicit height here the chain's `flex: 1` would resolve against
+   nothing and the terminal would collapse to its content's own height
+   instead of filling the viewport — the opposite of what "full-height"
+   mount means for this page specifically (the 12em-capped preview
+   inside `AgentsPage` deliberately has no such wrapper; this is the one
+   place that needs it).
+
+   `100dvh`, not `100vh` — `100vh` on a mobile browser includes the
+   address-bar chrome even while it's visibly on-screen, so the terminal
+   would render taller than the actually-visible viewport there;
+   `100dvh` tracks the real visible area instead. The subtraction below
+   is a fixed estimate (Shell.css's own `.shell-header` padding +
+   `.shell-body`'s), not a measured value — an exact fit isn't worth a
+   ResizeObserver for a single full-bleed page; a few pixels short of
+   the viewport edge reads as intentional breathing room, not a bug. */
+.ui-agent-terminal-page {
+  display: flex;
+  flex-direction: column;
+  height: calc(100dvh - 4.5em - 3em);
+}
+
+.ui-agent-terminal-page .ui-agent-term-preview-full {
+  flex: 1;
+  min-height: 0;
+}

frontend/packages/swarm-ui/src/pages/agents/AgentTerminalPage.tsx

@@ -0,0 +1,42 @@
+// <AgentTerminalPage> — the swarm terminal tab's full page, mounted at
+// `/agents/:name/terminal`. The MVP `AgentTermPreview` (below `AgentsPage`'s
+// detail panel) is explicitly capped and read-only; this is that same
+// component's `fullHeight` mount — no 12em cap, floating header badges
+// shown (there's no detail-panel `<dl>` here to duplicate them). Sending
+// input back to the agent is still explicit follow-up scope, same as the
+// preview's own file comment says — this page doesn't change that.
+//
+// Registers itself in the dynamic-tabs row on mount (not just when opened
+// via the preview's expand trigger) — a bookmark, a shared link, or a
+// plain page reload should all re-open the tab instead of landing on a
+// page with no way back into the tab row. `useDynamicTabs().open()` is
+// idempotent (dedupes by href), so this is safe to call every mount.
+import { useEffect } from "preact/hooks";
+import type { RouteComponentProps } from "wouter-preact";
+import { AgentTermPreview } from "./AgentTermPreview.js";
+import { useDynamicTabs } from "../../shell/useDynamicTabs.js";
+import "./AgentTerminalPage.css";
+
+export function AgentTerminalPage({
+  params,
+}: RouteComponentProps<{ name: string }>) {
+  const { open } = useDynamicTabs();
+  const name = decodeURIComponent(params.name);
+
+  // Runs once per mounted agent name — re-registering on every render
+  // would just be redundant work against an already-deduped list, but
+  // there's no reason to pay it more than once per identity.
+  useEffect(() => {
+    open({ href: `/agents/${encodeURIComponent(name)}/terminal`, label: name });
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- `open` is a
+    // fresh function identity every render (`useDynamicTabs` doesn't
+    // memoize it); including it would re-fire this effect every render
+    // instead of once per agent `name`.
+  }, [name]);
+
+  return (
+    <div class="ui-agent-terminal-page">
+      <AgentTermPreview agentName={name} fullHeight showHeaderBadges />
+    </div>
+  );
+}

frontend/packages/swarm-ui/src/shell/Shell.css

@@ -165,6 +165,64 @@
 .shell-nav-indicator.shell-nav-indicator-instant {
   transition: none;
 }
+/* Dynamic tabs group — inline in `.shell-nav` itself, next to the
+   static route links (mara, PR review: "the dynamic tab should be in
+   the top bar, not a new one below" — an earlier cut had this as its
+   own sticky row under the header; that version and the reasoning for
+   it are still in this file's git history if the split ever needs to
+   come back). `margin-left: 0.5em` + `border-left` reads as "a group
+   attached to the nav, not another nav item" without a second landmark
+   or a fixed pixel gap that'd fight `.shell-nav`'s own `gap`. */
+.shell-tabs {
+  display: flex;
+  align-items: center;
+  flex-wrap: wrap;
+  gap: 0.5em;
+  margin-left: 0.5em;
+  padding-left: 0.75em;
+  border-left: 1px solid var(--border);
+}
+.shell-tab {
+  display: flex;
+  align-items: center;
+  gap: 0.25em;
+  padding: 0.2em 0.4em 0.2em 0.7em;
+  border-radius: 0.3em;
+  background: var(--bg);
+  border: 1px solid var(--border);
+}
+.shell-tab-active {
+  border-color: var(--pink);
+}
+.shell-tab-link {
+  color: var(--muted);
+  text-decoration: none;
+  font-size: 0.9em;
+}
+.shell-tab-active .shell-tab-link {
+  color: var(--fg);
+}
+.shell-tab-link:hover {
+  color: var(--fg);
+}
+/* Same reset every icon-only chrome button in this codebase uses
+   (`Badge`'s own `<button>` case) — a bare `<button>` here isn't routed
+   through `Badge` since it's not a status/value pill, just a close
+   glyph, so the reset is inlined rather than reaching for a component
+   that doesn't fit this shape. */
+.shell-tab-close {
+  all: unset;
+  cursor: pointer;
+  line-height: 1;
+  padding: 0.1em 0.3em;
+  border-radius: 0.2em;
+  color: var(--muted);
+}
+.shell-tab-close:hover {
+  color: var(--fg);
+  background: color-mix(in srgb, var(--fg) 10%, transparent);
+}
+
 .shell-body {
   max-width: 60em;
   margin: 0 auto;

frontend/packages/swarm-ui/src/shell/Shell.tsx

@@ -34,6 +34,7 @@ import { UserMenu } from "./UserMenu.js";
 import { SettingsMenu } from "@hive/shared/settings-menu.js";
 import { useApplyThemeOverride } from "@hive/shared/theme-apply.js";
 import { useApplyMotionOverride } from "@hive/shared/motion-apply.js";
+import { useDynamicTabs } from "./useDynamicTabs.js";
 import "./Shell.css";
 
 // Storage keys this app owns for `@hive/shared`'s settings mechanism —
@@ -61,6 +62,20 @@ const NAV_ITEMS: { href: string; label: string; accent: string }[] = [
 // its own table view (plus the list+detail split) hits the same cap.
 const WIDE_BODY_ROUTES = new Set(["/issues", "/agents"]);
 
+// `/agents/:name/terminal` needs the same widening but can't join
+// the `Set` above — it's a parameterized path, one literal string can't
+// match every agent name. A 60em-capped terminal pane reads as cramped
+// (this is a full tab, not a sidebar preview), same reasoning as the
+// table routes above just for a different reason (a wide pane, not a
+// wide table).
+const WIDE_BODY_ROUTE_PATTERN = /^\/agents\/[^/]+\/terminal$/;
+
+function isWideBodyRoute(location: string): boolean {
+  return (
+    WIDE_BODY_ROUTES.has(location) || WIDE_BODY_ROUTE_PATTERN.test(location)
+  );
+}
+
 // Static fallback — matches `index.html`'s `<title>` default, so a page
 // never flashes something else before the fetch below resolves, and an
 // operator who never set `services.hyperhive.swarm.name` sees the exact
@@ -135,6 +150,50 @@ function NavLink({
   );
 }
 
+// One open agent-terminal tab (`useDynamicTabs`) — deliberately
+// its own small component, not folded into `NavLink` above: dynamic tabs
+// don't ride the sliding `.shell-nav-indicator` (there's no fixed set to
+// hop between — see `WIDE_BODY_ROUTE_PATTERN`'s own comment on why they
+// can't share `NAV_ITEMS`'s Set-based route list either), so "active"
+// here is a plain class toggle, not a measured position. The close ×
+// is a real sibling button, not nested inside the `<Link>` — a button
+// inside an `<a>` is invalid HTML and (worse) means a click anywhere on
+// the tab, including the ×, triggers the link navigation first.
+function DynamicTabLink({
+  href,
+  label,
+  active,
+  onClose,
+}: {
+  href: string;
+  label: string;
+  active: boolean;
+  onClose: () => void;
+}) {
+  return (
+    <span class={"shell-tab" + (active ? " shell-tab-active" : "")}>
+      <Link href={href} className="shell-tab-link">
+        {label}
+      </Link>
+      <button
+        type="button"
+        class="shell-tab-close"
+        title={`close ${label}`}
+        onClick={(e) => {
+          // Not a navigation — stop it reaching `Link`'s own click
+          // handling even though this button sits outside the anchor,
+          // since the two are visually one row and a stray bubble
+          // shouldn't be able to trigger a route change on close.
+          e.stopPropagation();
+          onClose();
+        }}
+      >
+        ×
+      </button>
+    </span>
+  );
+}
+
 export function Shell({ children }: { children: ComponentChildren }) {
   const [swarmName, setSwarmName] = useState<string | null>(null);
   const [location] = useLocation();
@@ -155,6 +214,15 @@ export function Shell({ children }: { children: ComponentChildren }) {
   // Every subsequent change (a real navigation) still animates normally.
   const [indicatorSettledOnce, setIndicatorSettledOnce] = useState(false);
 
+  // Open agent-terminal tabs — rendered inline in `.shell-nav` itself
+  // (mara, PR review: "the dynamic tab should be in the top bar, not a
+  // new one below" — an earlier cut had these as their own row under
+  // the header; see the git history on this file for that version and
+  // why it was reverted). Entirely separate from the fixed `NAV_ITEMS`
+  // list above, so they get their own small component (`DynamicTabLink`)
+  // rather than reusing `NavLink`.
+  const { tabs, close: closeTab } = useDynamicTabs();
+
   // Applied once here, not inside `SettingsMenu` — every route mounts
   // through this one `<Shell>`, so the override takes effect regardless
   // of which page is showing or whether the menu's ever been opened,
@@ -249,6 +317,18 @@ export function Shell({ children }: { children: ComponentChildren }) {
     return () => window.removeEventListener("resize", onResize);
   }, []);
 
+  // Same re-measure, for the same "a reflow, not a navigation" reason —
+  // now that the dynamic tabs render inline in `.shell-nav` (see the
+  // `useDynamicTabs()` comment above), *closing* a background tab (one
+  // that isn't the active route) shrinks the row without any navigation
+  // firing to trigger the hop effect's own re-measure. Opening one
+  // doesn't need this: `useDynamicTabs().open()` always navigates, so
+  // the hop effect already covers that case.
+  useEffect(() => {
+    if (settledIndexRef.current === -1) return;
+    setIndicator(measureIndex(settledIndexRef.current));
+  }, [tabs.length]);
+
   // Fetched once here, not per-page: every route mounts inside one
   // `<Shell>`, and the swarm's name doesn't change within a page
   // visit. A fetch failure is silently ignored — `swarmName` just stays
@@ -323,6 +403,30 @@ export function Shell({ children }: { children: ComponentChildren }) {
               backgroundColor: indicator?.accent ?? "transparent",
             }}
           />
+          {/* Open agent-terminal tabs — inline in the same nav row as
+              the static routes (mara's review call, see the
+              `useDynamicTabs()` comment above). Only rendered when
+              there's something to show — an always-present empty group
+              would just be dead chrome for the far more common case of
+              no open terminal tabs. `role="group"`, not a second `<nav>`:
+              there's already exactly one nav landmark in this header. */}
+          {tabs.length > 0 && (
+            <div
+              class="shell-tabs"
+              role="group"
+              aria-label="open agent terminals"
+            >
+              {tabs.map((tab) => (
+                <DynamicTabLink
+                  key={tab.href}
+                  href={tab.href}
+                  label={tab.label}
+                  active={tab.href === location}
+                  onClose={() => closeTab(tab.href)}
+                />
+              ))}
+            </div>
+          )}
         </nav>
         {/* Single `margin-left: auto` on the wrapper, not on each menu
             individually — two adjacent flex items both set to
@@ -341,8 +445,7 @@ export function Shell({ children }: { children: ComponentChildren }) {
           apply, only the max-width cap changes. */}
       <div
         class={
-          "shell-body" +
-          (WIDE_BODY_ROUTES.has(location) ? " shell-body-wide" : "")
+          "shell-body" + (isWideBodyRoute(location) ? " shell-body-wide" : "")
         }
         key={location}
       >

frontend/packages/swarm-ui/src/shell/useDynamicTabs.ts

@@ -0,0 +1,87 @@
+// useDynamicTabs — the small piece of shared state behind the swarm-ui
+// header's second tab row: agent terminal tabs a user has opened, on top
+// of `Shell`'s always-present static `NAV_ITEMS`. Not a generic "any page
+// can open a tab" mechanism — the swarm-level terminal-tab work's own
+// scope note keeps this to just agent terminals for now.
+//
+// Built directly on `@hive/shared/settings-storage.js`'s `useLocalSetting`
+// — same browser-local persistence + same-tab pub/sub `theme-apply.js`/
+// `motion-apply.js` already use, so an opened terminal tab survives a
+// reload instead of vanishing (mara's own bar for "browser-local setting"
+// framing in the issue's plan comment). `Shell` is the one mount point
+// that renders the row; `AgentTermPreview`'s expand trigger and
+// `AgentTerminalPage`'s own mount effect are the two callers of `open()`.
+// See the `useEffect` below for a same-tab pub/sub race this hook works
+// around — found by actually rendering a cold terminal-tab load, not
+// just reasoning about the code.
+import { useEffect } from "preact/hooks";
+import { useLocation } from "wouter-preact";
+import {
+  readLocalSetting,
+  useLocalSetting,
+} from "@hive/shared/settings-storage.js";
+
+export interface DynamicTab {
+  href: string;
+  label: string;
+}
+
+const TABS_KEY = "swarm-ui:dynamic-tabs";
+
+export interface UseDynamicTabsResult {
+  tabs: DynamicTab[];
+  /** Adds `tab` if not already open (deduped by `href`) and navigates to it. Re-opening an already-open tab just navigates — it doesn't duplicate or reorder the row. */
+  open: (tab: DynamicTab) => void;
+  /** Removes the tab. If it was the active route, navigates to `fallbackHref` (default `/agents`, since agent terminal tabs are the only kind today). */
+  close: (href: string, fallbackHref?: string) => void;
+}
+
+export function useDynamicTabs(): UseDynamicTabsResult {
+  const [tabs, setTabs] = useLocalSetting<DynamicTab[]>(TABS_KEY, []);
+  const [location, navigate] = useLocation();
+
+  // Load-bearing, not decoration — a same-tab pub/sub race, confirmed by
+  // actually rendering a cold load of `/agents/:name/terminal` (headless
+  // chromium) and finding the tab row silently empty without this.
+  // `useLocalSetting` subscribes inside a `useEffect`, and mount effects
+  // fire children-before-parents (Preact mirrors React here). `Shell`
+  // wraps `AgentTerminalPage` as a descendant, so on a direct/reload
+  // load both mount in the same commit — `AgentTerminalPage`'s own
+  // "register this tab" effect (a call to `open()` below) can fire and
+  // notify subscribers *before* `Shell`'s own `useLocalSetting`
+  // subscription (set up in ITS mount effect, which per that ordering
+  // runs after the child's) even exists to catch it. `Shell`'s first
+  // `tabs` snapshot then silently stays stale forever, since there's no
+  // second write coming to re-trigger it.
+  //
+  // Fix: re-read storage on every `location` change, not just on a
+  // pub/sub notification. This effect is *this hook's own* mount effect,
+  // so it's guaranteed to run after any descendant's mount effect that
+  // just wrote — by the time it fires, a same-commit write from a child
+  // has already landed. Costs a redundant, idempotent write-back on
+  // every navigation across every `useDynamicTabs()` call site — traded
+  // deliberately for not touching `@hive/shared/settings-storage.ts`
+  // itself (a primitive theme/motion overrides also depend on) for a fix
+  // specific to this one hook's own race.
+  useEffect(() => {
+    setTabs(readLocalSetting(TABS_KEY, []));
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- `setTabs` is
+    // a fresh function identity every render (`useLocalSetting` doesn't
+    // memoize it); including it would re-run this every render instead
+    // of once per navigation.
+  }, [location]);
+
+  function open(tab: DynamicTab) {
+    if (!tabs.some((t) => t.href === tab.href)) {
+      setTabs([...tabs, tab]);
+    }
+    navigate(tab.href);
+  }
+
+  function close(href: string, fallbackHref = "/agents") {
+    setTabs(tabs.filter((t) => t.href !== href));
+    if (location === href) navigate(fallbackHref);
+  }
+
+  return { tabs, open, close };
+}