diff --git a/apps/web/src/layouts/AccountLayout.astro b/apps/web/src/layouts/AccountLayout.astro
index 3772de75..c9829598 100644
--- a/apps/web/src/layouts/AccountLayout.astro
+++ b/apps/web/src/layouts/AccountLayout.astro
@@ -229,47 +229,16 @@ const sidebarSeedJson = JSON.stringify(sidebarProps).replace(/</g, "\\u003c");
     />
     <script>
       import { onAstroPageLoad, requireElement, resolveSessionGate } from "../lib/account-shell";
-      import { createElement } from "react";
-      import { hydrateRoot, type Root } from "react-dom/client";
-      import { detectIdentifierPrefix } from "../lib/react-island";
+      import { createIslandMounter } from "../lib/react-island";
       import type { ShellSidebarIslandProps } from "../components/shell/ShellSidebar";
 
-      let sidebarRoot: Root | null = null;
-
-      function teardownSidebar(): void {
-        if (!sidebarRoot) return;
-        try {
-          sidebarRoot.unmount();
-        } catch {
-          // Container may already be gone after a body swap.
-        }
-        sidebarRoot = null;
-      }
-
-      function readSidebarSeed(): ShellSidebarIslandProps | null {
-        const el = document.getElementById("shell-sidebar-seed");
-        if (!el?.textContent) return null;
-        try {
-          return JSON.parse(el.textContent) as ShellSidebarIslandProps;
-        } catch {
-          return null;
-        }
-      }
-
-      // Same manual SSR + hydrateRoot mechanism the workspace files table uses
+      // Same manual SSR + hydrateRoot mechanism the workspace islands use
       // (`client:*` is banned repo-wide, see astro.config.mjs).
-      async function bootSidebar(): Promise<void> {
-        const mount = document.getElementById("shell-sidebar");
-        const seed = readSidebarSeed();
-        if (!mount || !seed) return;
-        document.addEventListener("astro:before-swap", teardownSidebar, { once: true });
-        const { ShellSidebar } = await import("../components/shell/ShellSidebar");
-        if (!document.contains(mount)) return;
-        teardownSidebar();
-        sidebarRoot = hydrateRoot(mount, createElement(ShellSidebar, seed), {
-          identifierPrefix: detectIdentifierPrefix(mount.innerHTML),
-        });
-      }
+      const bootSidebar = createIslandMounter<ShellSidebarIslandProps>({
+        mountId: "shell-sidebar",
+        seedId: "shell-sidebar-seed",
+        load: () => import("../components/shell/ShellSidebar").then((m) => m.ShellSidebar),
+      });
 
       onAstroPageLoad(() => {
         if (!document.getElementById("app")) return;
diff --git a/apps/web/src/layouts/AdminLayout.astro b/apps/web/src/layouts/AdminLayout.astro
index 9eed08ef..5c002b0e 100644
--- a/apps/web/src/layouts/AdminLayout.astro
+++ b/apps/web/src/layouts/AdminLayout.astro
@@ -143,42 +143,15 @@ const sidebarSeedJson = JSON.stringify(sidebarProps).replace(/</g, "\\u003c");
         requireElement,
         resolveSessionGate,
       } from "../lib/account-shell";
-      import { createElement } from "react";
-      import { hydrateRoot, type Root } from "react-dom/client";
-      import { detectIdentifierPrefix } from "../lib/react-island";
+      import { createIslandMounter } from "../lib/react-island";
       import type { ShellSidebarIslandProps } from "../components/shell/ShellSidebar";
 
-      let sidebarRoot: Root | null = null;
-
-      function teardownSidebar(): void {
-        if (!sidebarRoot) return;
-        try {
-          sidebarRoot.unmount();
-        } catch {
-          // Container may already be gone after a body swap.
-        }
-        sidebarRoot = null;
-      }
-
       // Same manual SSR + hydrateRoot mechanism AccountLayout uses.
-      async function bootSidebar(): Promise<void> {
-        const mount = document.getElementById("shell-sidebar");
-        const seedEl = document.getElementById("shell-sidebar-seed");
-        if (!mount || !seedEl?.textContent) return;
-        let seed: ShellSidebarIslandProps;
-        try {
-          seed = JSON.parse(seedEl.textContent) as ShellSidebarIslandProps;
-        } catch {
-          return;
-        }
-        document.addEventListener("astro:before-swap", teardownSidebar, { once: true });
-        const { ShellSidebar } = await import("../components/shell/ShellSidebar");
-        if (!document.contains(mount)) return;
-        teardownSidebar();
-        sidebarRoot = hydrateRoot(mount, createElement(ShellSidebar, seed), {
-          identifierPrefix: detectIdentifierPrefix(mount.innerHTML),
-        });
-      }
+      const bootSidebar = createIslandMounter<ShellSidebarIslandProps>({
+        mountId: "shell-sidebar",
+        seedId: "shell-sidebar-seed",
+        load: () => import("../components/shell/ShellSidebar").then((m) => m.ShellSidebar),
+      });
 
       onAstroPageLoad(() => {
         if (!document.getElementById("dashboard")) return;
diff --git a/apps/web/src/lib/react-island.ts b/apps/web/src/lib/react-island.ts
index 2d98c740..e76d4441 100644
--- a/apps/web/src/lib/react-island.ts
+++ b/apps/web/src/lib/react-island.ts
@@ -1,3 +1,6 @@
+import { createElement, type ComponentType } from "react";
+import { hydrateRoot, type Root } from "react-dom/client";
+
 /**
  * Manual-island hydration helper (`client:*` is banned repo-wide; see
  * astro.config.mjs, so React components are SSR'd plain and `hydrateRoot`-ed
@@ -26,3 +29,68 @@ const SSR_USE_ID_RE = /_(r\d+)R_[0-9a-v]/;
 export function detectIdentifierPrefix(html: string): string {
   return SSR_USE_ID_RE.exec(html)?.[1] ?? "";
 }
+
+export interface IslandMounterOptions<P extends object> {
+  /** id of the element wrapping the SSR'd island markup. */
+  mountId: string;
+  /** id of the `<script type="application/json">` carrying the seed props. */
+  seedId: string;
+  /**
+   * Lazily resolves the component to hydrate. Keep the `import()` specifier
+   * inline (`() => import("./X").then((m) => m.X)`) so the bundler can still
+   * code-split it — a static top-level import would defeat the point, and a
+   * dev Fast-Refresh glitch in one island shouldn't block the page's other
+   * scripts.
+   */
+  load: () => Promise<ComponentType<P>>;
+}
+
+/**
+ * Builds the boot function for a manually-hydrated island, factoring the
+ * read-seed → teardown-on-swap → lazy-import → `hydrateRoot` lifecycle that
+ * every mount site otherwise hand-writes. Call once at a `<script>`'s top
+ * level (so its `root` persists across ClientRouter soft-navs) and invoke the
+ * returned boot from `onAstroPageLoad` — which fires on first load and on
+ * every nav, so one registration both mounts and remounts.
+ *
+ * Returns without mounting when the element or seed is absent (a page that
+ * doesn't carry this island), so a layout can call it unconditionally. The
+ * component must compose its own `IslandErrorBoundary`, as the app's islands
+ * do, so the hydrated tree matches the SSR'd markup exactly.
+ */
+export function createIslandMounter<P extends object>(
+  opts: IslandMounterOptions<P>,
+): () => Promise<void> {
+  let root: Root | null = null;
+
+  function teardown(): void {
+    if (!root) return;
+    try {
+      root.unmount();
+    } catch {
+      // Container may already be gone after a body swap.
+    }
+    root = null;
+  }
+
+  return async function boot(): Promise<void> {
+    const mount = document.getElementById(opts.mountId);
+    const seedEl = document.getElementById(opts.seedId);
+    if (!mount || !seedEl?.textContent) return;
+    let seed: P;
+    try {
+      seed = JSON.parse(seedEl.textContent) as P;
+    } catch {
+      return;
+    }
+    // Tear down before Astro swaps the body away. {once:true} auto-clears, so
+    // repeated astro:page-load events from ClientRouter never stack listeners.
+    document.addEventListener("astro:before-swap", teardown, { once: true });
+    const Component = await opts.load();
+    if (!document.contains(mount)) return;
+    teardown();
+    root = hydrateRoot(mount, createElement(Component, seed), {
+      identifierPrefix: detectIdentifierPrefix(mount.innerHTML),
+    });
+  };
+}
diff --git a/apps/web/src/pages/account/workspaces/[name]/files.astro b/apps/web/src/pages/account/workspaces/[name]/files.astro
index 7c825e2f..7998cfcb 100644
--- a/apps/web/src/pages/account/workspaces/[name]/files.astro
+++ b/apps/web/src/pages/account/workspaces/[name]/files.astro
@@ -116,9 +116,7 @@ const filesSeedJson = JSON.stringify({
 
   <script>
     import { onAstroPageLoad } from "../../../../lib/account-shell";
-    import { createElement } from "react";
-    import { hydrateRoot, type Root } from "react-dom/client";
-    import { detectIdentifierPrefix } from "../../../../lib/react-island";
+    import { createIslandMounter } from "../../../../lib/react-island";
     import type { ListingState } from "../../../../components/WorkspaceFileTable";
     import type { WorkspaceInfoStatus } from "../../../../lib/workspace-file-row";
 
@@ -130,52 +128,14 @@ const filesSeedJson = JSON.stringify({
       initialInfo?: WorkspaceInfoStatus;
     }
 
-    let filesTableRoot: Root | null = null;
-
-    function teardown(): void {
-      if (!filesTableRoot) return;
-      try {
-        filesTableRoot.unmount();
-      } catch {
-        // Container may already be gone after a body swap.
-      }
-      filesTableRoot = null;
-    }
-
-    function readSeed(): FilesSeed | null {
-      const el = document.getElementById("ws-files-seed");
-      if (!el?.textContent) return null;
-      try {
-        return JSON.parse(el.textContent) as FilesSeed;
-      } catch {
-        return null;
-      }
-    }
-
-    async function boot(): Promise<void> {
-      const mount = document.getElementById("ws-files-table");
-      const seed = readSeed();
-      if (!mount || !seed) return;
-
-      // Tear down the previous mount before Astro swaps this page's body away
-      // (registered once per boot() call — {once:true} auto-clears itself so
-      // repeated astro:page-load events from ClientRouter never stack listeners).
-      document.addEventListener("astro:before-swap", teardown, { once: true });
-
-      // Lazy, not a static top-level import: keeps a Fast-Refresh/HMR dev
-      // glitch in this component from blocking the rest of the page's
-      // scripts — same reasoning every sibling workspace-tab mount uses.
-      const { WorkspaceFileTable } = await import("../../../../components/WorkspaceFileTable");
-      if (!document.contains(mount)) return;
-      teardown();
-      // `WorkspaceFileTable` already composes `IslandErrorBoundary`
-      // internally (plan 005 Phase A) — mounting it directly, with no extra
-      // wrapper, matches the SSR'd tree exactly, so `hydrateRoot` reconciles
-      // without warnings.
-      filesTableRoot = hydrateRoot(mount, createElement(WorkspaceFileTable, seed), {
-        identifierPrefix: detectIdentifierPrefix(mount.innerHTML),
-      });
-    }
+    // `WorkspaceFileTable` composes its own IslandErrorBoundary, so mounting it
+    // directly matches the SSR'd tree and hydrateRoot reconciles cleanly.
+    const boot = createIslandMounter<FilesSeed>({
+      mountId: "ws-files-table",
+      seedId: "ws-files-seed",
+      load: () =>
+        import("../../../../components/WorkspaceFileTable").then((m) => m.WorkspaceFileTable),
+    });
 
     // astro:page-load fires on the initial load too (same as every sibling
     // tab), so this single registration mounts on first load and on nav —
diff --git a/apps/web/src/pages/account/workspaces/[name]/screenshots.astro b/apps/web/src/pages/account/workspaces/[name]/screenshots.astro
index ad62cac6..d6d0cae3 100644
--- a/apps/web/src/pages/account/workspaces/[name]/screenshots.astro
+++ b/apps/web/src/pages/account/workspaces/[name]/screenshots.astro
@@ -112,9 +112,7 @@ const screenshotsSeedJson = JSON.stringify({
 
   <script>
     import { onAstroPageLoad } from "../../../../lib/account-shell";
-    import { createElement } from "react";
-    import { hydrateRoot, type Root } from "react-dom/client";
-    import { detectIdentifierPrefix } from "../../../../lib/react-island";
+    import { createIslandMounter } from "../../../../lib/react-island";
     import type { OverviewState } from "../../../../components/ScreenshotsByPath";
     import type { WorkspaceInfoStatus } from "../../../../lib/workspace-file-row";
 
@@ -126,51 +124,14 @@ const screenshotsSeedJson = JSON.stringify({
       initialInfo?: WorkspaceInfoStatus;
     }
 
-    let screenshotsRoot: Root | null = null;
-
-    function teardown(): void {
-      if (!screenshotsRoot) return;
-      try {
-        screenshotsRoot.unmount();
-      } catch {
-        // Container may already be gone after a body swap.
-      }
-      screenshotsRoot = null;
-    }
-
-    function readSeed(): ScreenshotsSeed | null {
-      const el = document.getElementById("ws-screenshots-seed");
-      if (!el?.textContent) return null;
-      try {
-        return JSON.parse(el.textContent) as ScreenshotsSeed;
-      } catch {
-        return null;
-      }
-    }
-
-    async function boot(): Promise<void> {
-      const mount = document.getElementById("ws-screenshots");
-      const seed = readSeed();
-      if (!mount || !seed) return;
-
-      // Tear down the previous mount before Astro swaps this page's body away
-      // (registered once per boot() call — {once:true} auto-clears itself so
-      // repeated astro:page-load events from ClientRouter never stack listeners).
-      document.addEventListener("astro:before-swap", teardown, { once: true });
-
-      // Lazy, not a static top-level import: keeps a Fast-Refresh/HMR dev
-      // glitch in this component from blocking the rest of the page's
-      // scripts — same reasoning every sibling workspace-tab mount uses.
-      const { ScreenshotsByPath } = await import("../../../../components/ScreenshotsByPath");
-      if (!document.contains(mount)) return;
-      teardown();
-      // `ScreenshotsByPath` already composes `IslandErrorBoundary` internally
-      // (plan 006) — mounting it directly, with no extra wrapper, matches the
-      // SSR'd tree exactly, so `hydrateRoot` reconciles without warnings.
-      screenshotsRoot = hydrateRoot(mount, createElement(ScreenshotsByPath, seed), {
-        identifierPrefix: detectIdentifierPrefix(mount.innerHTML),
-      });
-    }
+    // `ScreenshotsByPath` composes its own IslandErrorBoundary, so mounting it
+    // directly matches the SSR'd tree and hydrateRoot reconciles cleanly.
+    const boot = createIslandMounter<ScreenshotsSeed>({
+      mountId: "ws-screenshots",
+      seedId: "ws-screenshots-seed",
+      load: () =>
+        import("../../../../components/ScreenshotsByPath").then((m) => m.ScreenshotsByPath),
+    });
 
     // astro:page-load fires on the initial load too (same as every sibling
     // tab), so this single registration mounts on first load and on nav —
diff --git a/apps/web/src/pages/admin/index.astro b/apps/web/src/pages/admin/index.astro
index d8d6480b..14d26452 100644
--- a/apps/web/src/pages/admin/index.astro
+++ b/apps/web/src/pages/admin/index.astro
@@ -32,50 +32,15 @@ const seedJson = JSON.stringify({ apiOrigin }).replace(/</g, "\\u003c");
 
   <script>
     import { onAstroPageLoad } from "../../lib/account-shell";
-    import { createElement } from "react";
-    import { hydrateRoot, type Root } from "react-dom/client";
-    import { detectIdentifierPrefix } from "../../lib/react-island";
+    import { createIslandMounter } from "../../lib/react-island";
     import type { AdminWorkspacesTableProps } from "../../components/admin/AdminWorkspacesTable";
 
-    let tableRoot: Root | null = null;
-
-    function teardown(): void {
-      if (!tableRoot) return;
-      try {
-        tableRoot.unmount();
-      } catch {
-        // Container may already be gone after a body swap.
-      }
-      tableRoot = null;
-    }
-
-    function readSeed(): AdminWorkspacesTableProps | null {
-      const el = document.getElementById("admin-workspaces-seed");
-      if (!el?.textContent) return null;
-      try {
-        return JSON.parse(el.textContent) as AdminWorkspacesTableProps;
-      } catch {
-        return null;
-      }
-    }
-
-    async function boot(): Promise<void> {
-      const mount = document.getElementById("admin-workspaces-mount");
-      const seed = readSeed();
-      if (!mount || !seed) return;
-
-      document.addEventListener("astro:before-swap", teardown, { once: true });
-
-      // Lazy import (not top-level) mirrors the sibling islands: keeps a dev
-      // Fast-Refresh glitch in this component from blocking the page's other
-      // scripts.
-      const { AdminWorkspacesTable } = await import("../../components/admin/AdminWorkspacesTable");
-      if (!document.contains(mount)) return;
-      teardown();
-      tableRoot = hydrateRoot(mount, createElement(AdminWorkspacesTable, seed), {
-        identifierPrefix: detectIdentifierPrefix(mount.innerHTML),
-      });
-    }
+    const boot = createIslandMounter<AdminWorkspacesTableProps>({
+      mountId: "admin-workspaces-mount",
+      seedId: "admin-workspaces-seed",
+      load: () =>
+        import("../../components/admin/AdminWorkspacesTable").then((m) => m.AdminWorkspacesTable),
+    });
 
     onAstroPageLoad(() => void boot());
   </script>