5 files changed, 190 insertions, 0 deletions

diff --git a/src/features/plugins/index.ts b/src/features/plugins/index.ts
index 7a9d1a0..f79ed98 100644
--- a/src/features/plugins/index.ts
+++ b/src/features/plugins/index.ts
@@ -13,6 +13,7 @@ export { autoCheckBackendPrereqs } from "./logic/prereqs";
 export type {
   PluginNode,
   PluginSection,
+  WorkspaceLayoutPort,
 } from "./logic/types";
 export { TIER_ORDER, tierLabel } from "./logic/types";
 export { groupByTier, pluginNodes, splitSections, withFrontendStates } from "./logic/view-model";
diff --git a/src/features/plugins/logic/types.ts b/src/features/plugins/logic/types.ts
index d5fa4bb..ec80c9b 100644
--- a/src/features/plugins/logic/types.ts
+++ b/src/features/plugins/logic/types.ts
@@ -51,6 +51,28 @@ export function tierLabel(tier: PluginTier): string {
 export const TIER_ORDER: readonly PluginTier[] = ["core", "providers", "standard"];
 
 /**
+ * The layout port (plan 04 §4.4) the workspace plugins modal needs for the
+ * "Reset layout to default" affordance — the modal is the natural home (it
+ * is where users manage the layout plugins themselves). Wired by the
+ * composition root over the layout store; absent → the section doesn't
+ * render (tests).
+ */
+export interface WorkspaceLayoutPort {
+  /**
+   * Whether a layout provider is active (the reset button's gate). False →
+   * the button is DISABLED with the reason shown ("no layout plugin
+   * enabled") — there is nothing to reset and no persistence to re-seed.
+   */
+  readonly providerActive: boolean;
+  /**
+   * Reset the workspace's layout to the default seed (`DELETE
+   * /workspaces/:id/layout` → re-seed → broadcast). Resolves to `null` on
+   * success or to the failure reason to display.
+   */
+  readonly reset: (workspaceId: string) => Promise<string | null>;
+}
+
+/**
  * Runtime-normalize a tier value to the canonical THREE: anything that is not
  * exactly `core` | `providers` | `standard` — a missing tier, or a value
  * outside the contract ("kernel" is NOT a tier; the kernel hosts plugins, it
diff --git a/src/features/plugins/ui/ResetLayoutConfirm.svelte b/src/features/plugins/ui/ResetLayoutConfirm.svelte
new file mode 100644
index 0000000..1f26601
--- /dev/null
+++ b/src/features/plugins/ui/ResetLayoutConfirm.svelte
@@ -0,0 +1,30 @@
+<script lang="ts">
+  /**
+   * The "Reset layout to default?" confirm (plan 04 §4.4) — the dialog copy
+   * names the consequence exactly: this workspace's layout returns to the
+   * default; plugin and dropdown customizations are lost (there is NO
+   * undo — the no-revert semantics make the reset the recovery path).
+   */
+  let {
+    onConfirm,
+    onCancel,
+  }: {
+    onConfirm: () => void;
+    onCancel: () => void;
+  } = $props();
+</script>
+
+<div class="modal modal-open" role="dialog" aria-label="Reset layout to default?">
+  <div class="modal-box max-w-md">
+    <h3 class="text-lg font-bold text-warning">Reset layout to default?</h3>
+    <p class="py-3 text-sm">
+      This workspace's layout returns to the default; plugin and dropdown customizations are lost.
+    </p>
+    <div class="modal-action">
+      <button type="button" class="btn btn-ghost btn-sm" onclick={onCancel}>Cancel</button>
+      <button type="button" class="btn btn-warning btn-sm" onclick={onConfirm}>Reset</button>
+    </div>
+  </div>
+  <!-- svelte-ignore a11y_click_events_have_key_events, a11y_no_static_element_interactions -->
+  <div class="modal-backdrop" onclick={onCancel}></div>
+</div>
diff --git a/src/features/plugins/ui/WorkspacePluginModal.svelte b/src/features/plugins/ui/WorkspacePluginModal.svelte
index bce885b..d1bb27a 100644
--- a/src/features/plugins/ui/WorkspacePluginModal.svelte
+++ b/src/features/plugins/ui/WorkspacePluginModal.svelte
@@ -2,17 +2,25 @@
   import { onMount } from "svelte";
   import type { PluginsStore } from "../store.svelte";
   import { rowBlockReason, rowChecked, rowSelectable, stateLabel } from "../logic/workspace-row";
+  import type { WorkspaceLayoutPort } from "../logic/types";
+  import ResetLayoutConfirm from "./ResetLayoutConfirm.svelte";
 
   let {
     workspaceId,
     workspaceTitle,
     plugins,
+    layout,
     onClose,
   }: {
     workspaceId: string;
     /** The workspace's display title (modal heading). */
     workspaceTitle: string;
     plugins: PluginsStore;
+    /**
+     * The layout port (plan 04 §4.4) — gates + powers the "Reset layout to
+     * default" affordance. Absent → the section doesn't render (tests).
+     */
+    layout?: WorkspaceLayoutPort;
     onClose: () => void;
   } = $props();
 
@@ -31,6 +39,21 @@
   async function toggle(pluginId: string, checked: boolean): Promise<void> {
     await plugins.setWorkspaceState(workspaceId, pluginId, checked ? "enabled" : "disabled");
   }
+
+  // ── The reset affordance (plan 04 §4.4) ─────────────────────────────────
+  let resetOpen = $state(false);
+  let resetting = $state(false);
+  let resetError = $state<string | null>(null);
+
+  async function confirmReset(): Promise<void> {
+    if (layout === undefined || resetting) return;
+    resetting = true;
+    resetError = null;
+    const failure = await layout.reset(workspaceId);
+    resetting = false;
+    resetOpen = false;
+    if (failure !== null) resetError = failure;
+  }
 </script>
 
 <div class="modal modal-open" role="dialog" aria-label={`Plugins for ${workspaceTitle}`}>
@@ -101,6 +124,35 @@
       </table>
     {/if}
 
+    {#if layout}
+      <div class="mt-3 border-t border-base-300 pt-3">
+        <div class="flex items-center justify-between gap-3">
+          <div>
+            <p class="text-sm font-medium">Layout</p>
+            {#if layout.providerActive}
+              <p class="text-xs opacity-60">Managed by the active layout plugin.</p>
+            {:else}
+              <p class="text-xs opacity-60">No layout plugin enabled — no layout to reset.</p>
+            {/if}
+          </div>
+          <button
+            type="button"
+            class="btn btn-warning btn-sm"
+            disabled={!layout.providerActive || resetting}
+            title={layout.providerActive
+              ? "Restore this workspace's default layout"
+              : "No layout plugin enabled"}
+            onclick={() => (resetOpen = true)}
+          >
+            Reset layout to default
+          </button>
+        </div>
+        {#if resetError}
+          <p class="mt-1 text-xs text-error" role="alert">Resetting the layout failed: {resetError}</p>
+        {/if}
+      </div>
+    {/if}
+
     <div class="modal-action">
       <button type="button" class="btn btn-sm" onclick={onClose}>Close</button>
     </div>
@@ -108,3 +160,7 @@
   <!-- svelte-ignore a11y_click_events_have_key_events, a11y_no_static_element_interactions -->
   <div class="modal-backdrop" onclick={onClose}></div>
 </div>
+
+{#if resetOpen && layout}
+  <ResetLayoutConfirm onConfirm={() => void confirmReset()} onCancel={() => (resetOpen = false)} />
+{/if}
diff --git a/src/features/plugins/ui/WorkspacePluginModal.test.ts b/src/features/plugins/ui/WorkspacePluginModal.test.ts
index 32e88d7..6bc7179 100644
--- a/src/features/plugins/ui/WorkspacePluginModal.test.ts
+++ b/src/features/plugins/ui/WorkspacePluginModal.test.ts
@@ -3,6 +3,7 @@ import { render, screen } from "@testing-library/svelte";
 import userEvent from "@testing-library/user-event";
 import { describe, expect, it, vi } from "vitest";
 import type { PluginsHttp } from "../adapter/http";
+import type { WorkspaceLayoutPort } from "../logic/types";
 import { createPluginsStore } from "../store.svelte";
 import WorkspacePluginModal from "./WorkspacePluginModal.svelte";
 
@@ -46,6 +47,14 @@ async function renderModal(http: PluginsHttp = fakeHttp()) {
   return { store, http };
 }
 
+/** A layout port (plan 04 §4.4) scripted per test. */
+function fakeLayoutPort(
+  providerActive = true,
+  reset: WorkspaceLayoutPort["reset"] = vi.fn(async () => null),
+): WorkspaceLayoutPort {
+  return { providerActive, reset };
+}
+
 describe("WorkspacePluginModal", () => {
   it("renders the workspace's plugin rows", async () => {
     await renderModal();
@@ -122,3 +131,75 @@ describe("WorkspacePluginModal", () => {
     expect(screen.getByText(/other workspaces inherit these states/i)).toBeInTheDocument();
   });
 });
+
+describe("WorkspacePluginModal — the reset-layout affordance (plan 04 §4.4)", () => {
+  async function renderWithLayout(layout?: ReturnType<typeof fakeLayoutPort>) {
+    const store = createPluginsStore(fakeHttp());
+    await store.openWorkspace("ws");
+    render(WorkspacePluginModal, {
+      props: {
+        workspaceId: "ws",
+        workspaceTitle: "My Workspace",
+        plugins: store,
+        ...(layout ? { layout } : {}),
+        onClose: vi.fn(),
+      },
+    });
+    return layout;
+  }
+
+  it("renders an ENABLED reset button when a layout provider is active", async () => {
+    await renderWithLayout(fakeLayoutPort(true));
+    const button = screen.getByRole("button", { name: /reset layout to default/i });
+    expect(button).toBeEnabled();
+  });
+
+  it("the button is DISABLED with the 'no layout plugin enabled' reason when no provider is active", async () => {
+    await renderWithLayout(fakeLayoutPort(false));
+    const button = screen.getByRole("button", { name: /reset layout to default/i });
+    expect(button).toBeDisabled();
+    expect(button.getAttribute("title")).toMatch(/no layout plugin enabled/i);
+    expect(screen.getByText(/no layout plugin enabled/i)).toBeInTheDocument();
+  });
+
+  it("no layout port → the layout section doesn't render at all (tests / no wiring)", async () => {
+    await renderWithLayout(undefined);
+    expect(screen.queryByRole("button", { name: /reset layout to default/i })).toBeNull();
+  });
+
+  it("confirming the dialog resets the layout (and the dialog copy names the consequence)", async () => {
+    const user = userEvent.setup();
+    const reset = vi.fn(async () => null);
+    await renderWithLayout(fakeLayoutPort(true, reset));
+
+    await user.click(screen.getByRole("button", { name: /reset layout to default/i }));
+    // The confirm dialog names the consequence exactly (§4.4 copy).
+    expect(
+      screen.getByText(
+        /layout returns to the default; plugin and dropdown customizations are lost/i,
+      ),
+    ).toBeInTheDocument();
+    await user.click(screen.getByRole("button", { name: /^reset$/i }));
+    expect(reset).toHaveBeenCalledWith("ws");
+  });
+
+  it("cancelling the dialog never resets", async () => {
+    const user = userEvent.setup();
+    const reset = vi.fn(async () => null);
+    await renderWithLayout(fakeLayoutPort(true, reset));
+
+    await user.click(screen.getByRole("button", { name: /reset layout to default/i }));
+    await user.click(screen.getByRole("button", { name: /cancel/i }));
+    expect(reset).not.toHaveBeenCalled();
+  });
+
+  it("a failed reset surfaces the reason as an alert", async () => {
+    const user = userEvent.setup();
+    const reset = vi.fn(async () => "no layout plugin enabled");
+    await renderWithLayout(fakeLayoutPort(true, reset));
+
+    await user.click(screen.getByRole("button", { name: /reset layout to default/i }));
+    await user.click(screen.getByRole("button", { name: /^reset$/i }));
+    expect(await screen.findByRole("alert")).toHaveTextContent(/resetting the layout failed/i);
+  });
+});