feat: workspaces shell + cwd-lsp rename + mcp/settings/system-prompt features + app wiring

- workspaces: URL-driven conversation grouping (home listing at /, routing,
  store, http adapter, WorkspaceCard) wired into the App.svelte shell
- rename features/workspace -> features/cwd-lsp (the cwd/lsp status feature)
- new features: mcp (status view), settings (chat-limit field), system-prompt
  (prompt builder), all rendered via the generic surface host
- chat: store + ChatView updates
- tabs: tabs-store updates
- app wiring: ErrorModal (full-screen error surface), app/App.svelte + store.svelte

This commit makes HEAD typecheck clean for the first time: the prior HEAD
(c95cc77) imported features/settings from app/App.svelte but never committed
the feature, so only the full working tree was green.

5 files changed, 678 insertions, 42 deletions

diff --git a/src/app/App.svelte b/src/app/App.svelte
index 9225cc7..18be3ea 100644
--- a/src/app/App.svelte
+++ b/src/app/App.svelte
@@ -22,6 +22,11 @@
 	import { manifest as conversationCacheManifest } from "../features/conversation-cache";
 	import { manifest as markdownManifest } from "../features/markdown";
 	import {
+		McpStatusView,
+		manifest as mcpManifest,
+		type McpStatusResult,
+	} from "../features/mcp";
+	import {
 		ChatLimitField,
 		manifest as settingsManifest,
 		type ChatLimitSaveResult,
@@ -42,9 +47,17 @@
 		type CwdSaveResult,
 		LspStatusView,
 		type LspStatusResult,
-		manifest as workspaceManifest,
-	} from "../features/workspace";
+		manifest as cwdLspManifest,
+	} from "../features/cwd-lsp";
+	import {
+		SystemPromptBuilder,
+		type LoadSystemPrompt as LoadSystemPromptAlias,
+		type LoadSystemPromptVariables as LoadSystemPromptVariablesAlias,
+		type SaveSystemPrompt as SaveSystemPromptAlias,
+		manifest as systemPromptManifest,
+	} from "../features/system-prompt";
 	import type { AppStore } from "./store.svelte";
+	import ErrorModal from "./ErrorModal.svelte";
 	import { createLocalStore } from "../adapters/local-storage";
 	import { untrack } from "svelte";
 
@@ -67,10 +80,12 @@
 	const viewKinds = [
 		{ id: "model", label: "Model" },
 		{ id: "lsp", label: "Language Servers" },
+		{ id: "mcp", label: "MCP Servers" },
 		{ id: "extensions", label: "Extensions" },
 		{ id: "cache-warming", label: "Cache Warming" },
 		{ id: "tasks", label: "Tasks" },
 		{ id: "compaction", label: "Compaction" },
+		{ id: "system-prompt", label: "System Prompt" },
 		{ id: "settings", label: "Settings" },
 	] as const;
 
@@ -99,9 +114,11 @@
 		conversationCacheManifest,
 		markdownManifest,
 		cacheWarmingManifest,
-		workspaceManifest,
+		cwdLspManifest,
+		mcpManifest,
 		smartScrollManifest,
 		settingsManifest,
+		systemPromptManifest,
 	].map((m) => [m.name, m.description] as const);
 
 	// Smart-scroll: keep the transcript pinned to the bottom while it streams,
@@ -187,6 +204,7 @@
 	});
 	const storedSidebarOpen = sidebarOpenStore.load();
 	let sidebarOpen = $state(storedSidebarOpen ?? (typeof window !== "undefined" ? window.innerWidth >= WIDE_BREAKPOINT : true));
+	let systemPromptModalOpen = $state(false);
 
 	$effect(() => {
 		sidebarOpenStore.save(sidebarOpen);
@@ -278,7 +296,7 @@
 			: { ok: false, error: result.error };
 	}
 
-	// Adapt the store's cwd/LSP results to the workspace feature's ports.
+	// Adapt the store's cwd/LSP results to the cwd-lsp feature's ports.
 	async function saveCwd(cwd: string): Promise<CwdSaveResult | null> {
 		const result = await store.setCwd(cwd);
 		if (result === null) return null;
@@ -292,6 +310,22 @@
 			? { ok: true, cwd: result.response.cwd, servers: result.response.servers }
 			: { ok: false, error: result.error };
 	}
+
+	async function loadMcpStatus(): Promise<McpStatusResult | null> {
+		const result = await store.mcpStatus();
+		if (result === null) return null;
+		return result.ok
+			? { ok: true, cwd: result.response.cwd, servers: result.response.servers }
+			: { ok: false, error: result.error };
+	}
+
+	// Adapt the store's system prompt results to the system-prompt feature's ports.
+	const loadSystemPromptPrompt: LoadSystemPromptAlias = () => store.loadSystemPrompt();
+
+	const loadSystemPromptVariablesPrompt: LoadSystemPromptVariablesAlias = () =>
+		store.loadSystemPromptVariables();
+
+	const saveSystemPromptPrompt: SaveSystemPromptAlias = (template) => store.setSystemPrompt(template);
 </script>
 
 <main class="relative flex h-screen overflow-hidden">
@@ -365,6 +399,7 @@
 							hasEarlier={store.activeChat.hasEarlier}
 							onShowEarlier={handleShowEarlier}
 							thinkingKeyBase={store.activeChat.thinkingKeyBase}
+							providerRetry={store.activeChat.providerRetry}
 						/>
 					{/key}
 				</div>
@@ -435,6 +470,19 @@
 	{/if}
 </main>
 
+{#if store.fatalError}
+	<ErrorModal error={store.fatalError} onDismiss={() => store.clearFatalError()} />
+{/if}
+
+{#if systemPromptModalOpen}
+	<SystemPromptBuilder
+		loadPrompt={loadSystemPromptPrompt}
+		savePrompt={saveSystemPromptPrompt}
+		loadVariables={loadSystemPromptVariablesPrompt}
+		onClose={() => (systemPromptModalOpen = false)}
+	/>
+{/if}
+
 {#snippet viewContent(kind: string)}
 	{#if kind === "model"}
 		<div class="flex flex-col gap-3">
@@ -452,6 +500,11 @@
 		{#key store.currentConversationId}
 			<LspStatusView cwd={store.cwd} canView={true} load={loadLspStatus} />
 		{/key}
+	{:else if kind === "mcp"}
+		<!-- Re-mount per conversation (incl. draft) so the loaded server list is isolated. -->
+		{#key store.currentConversationId}
+			<McpStatusView cwd={store.cwd} canView={true} load={loadMcpStatus} />
+		{/key}
 	{:else if kind === "extensions"}
 		<section>
 			<h3 class="mb-1 text-xs font-semibold uppercase opacity-60">Frontend modules</h3>
@@ -493,6 +546,21 @@
 				savePercent={saveCompactPercent}
 			/>
 		{/key}
+	{:else if kind === "system-prompt"}
+		<!-- Global system prompt template. Opens a full-page modal editor (half
+		     template / half variable palette). Not conversation-scoped (no {#key}). -->
+		<div class="flex flex-col gap-2">
+			<p class="text-xs opacity-60">
+				Edit the global system prompt template with variable placeholders. Opens a full-page editor.
+			</p>
+			<button
+				type="button"
+				class="btn btn-primary btn-sm"
+				onclick={() => (systemPromptModalOpen = true)}
+			>
+				Open builder
+			</button>
+		</div>
 	{:else if kind === "settings"}
 		<!-- FE-local settings. Not conversation-scoped (no {#key}: the chat limit is
 		     global), so the field stays mounted across tab switches. -->
diff --git a/src/app/App.test.ts b/src/app/App.test.ts
index 6a39296..1a93948 100644
--- a/src/app/App.test.ts
+++ b/src/app/App.test.ts
@@ -1,4 +1,4 @@
-import type { WsServerMessage } from "@dispatch/transport-contract";
+import type { SetCwdRequest, WsServerMessage } from "@dispatch/transport-contract";
 import type { SurfaceServerMessage } from "@dispatch/ui-contract";
 import { render, screen } from "@testing-library/svelte";
 import userEvent from "@testing-library/user-event";
@@ -62,6 +62,9 @@ function fakeFetchImpl(): typeof fetch {
 				status: 200,
 			});
 		}
+		if (url.includes("/conversations?status=")) {
+			return new Response(JSON.stringify({ conversations: [] }), { status: 200 });
+		}
 		if (url.endsWith("/cwd")) {
 			return new Response(JSON.stringify({ conversationId: "c", cwd: null }), { status: 200 });
 		}
@@ -415,4 +418,107 @@ describe("App component interaction tests", () => {
 
 		store.dispose();
 	});
+
+	it("shows a full-screen error modal when fetchOpenConversations fails", async () => {
+		// A fetch that throws for the conversations list endpoint (simulating a
+		// network failure / unreachable backend on a new device).
+		const failingFetch = async (input: string | URL | Request): Promise<Response> => {
+			const url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
+			if (url.endsWith("/models")) {
+				return new Response(JSON.stringify({ models: ["opencode/deepseek-v4-flash"] }), {
+					status: 200,
+				});
+			}
+			if (url.includes("/conversations?status=")) {
+				throw new TypeError("Failed to fetch: network error");
+			}
+			if (url.endsWith("/cwd")) {
+				return new Response(JSON.stringify({ conversationId: "c", cwd: null }), { status: 200 });
+			}
+			if (url.endsWith("/lsp")) {
+				return new Response(JSON.stringify({ conversationId: "c", cwd: null, servers: [] }), {
+					status: 200,
+				});
+			}
+			return new Response(JSON.stringify({ chunks: [], latestSeq: 0 }), { status: 200 });
+		};
+
+		const ws = fakeSocket();
+		const store = createAppStore({
+			socketFactory: () => ws,
+			fetchImpl: failingFetch,
+			localStorage: createFakeStorage(),
+		});
+		ws.resolveOpen();
+
+		render(App, { props: { store } });
+
+		// The modal should appear with the error text
+		const dialog = await screen.findByRole("dialog", { name: "Error" }, { timeout: 3000 });
+		expect(dialog).toBeInTheDocument();
+		expect(dialog).toHaveTextContent("Failed to load conversations");
+		expect(dialog).toHaveTextContent("TypeError");
+		expect(dialog).toHaveTextContent("network error");
+
+		// Dismiss button clears the modal
+		const dismissBtn = screen.getByRole("button", { name: "Dismiss error" });
+		await userEvent.setup().click(dismissBtn);
+		expect(store.fatalError).toBeNull();
+
+		store.dispose();
+	});
+
+	it("does not show the error modal when fetchOpenConversations succeeds", async () => {
+		const ws = fakeSocket();
+		const store = createAppStore({
+			socketFactory: () => ws,
+			fetchImpl: fakeFetchImpl(), // returns valid empty conversations list
+			localStorage: createFakeStorage(),
+		});
+		ws.resolveOpen();
+
+		render(App, { props: { store } });
+
+		// Wait a tick for boot async to settle
+		await new Promise((resolve) => setTimeout(resolve, 200));
+
+		expect(store.fatalError).toBeNull();
+
+		store.dispose();
+	});
+
+	it("sends workspaceId when setting cwd", async () => {
+		let capturedBody: SetCwdRequest | undefined;
+		const fetchWithCapture = async (
+			input: string | URL | Request,
+			init?: RequestInit,
+		): Promise<Response> => {
+			const url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
+			if (url.endsWith("/cwd") && init?.method === "PUT") {
+				capturedBody = JSON.parse(init.body as string) as SetCwdRequest;
+				return new Response(JSON.stringify({ conversationId: "c", cwd: capturedBody.cwd }), {
+					status: 200,
+				});
+			}
+			return fakeFetchImpl()(input);
+		};
+
+		const ws = fakeSocket();
+		const store = createAppStore({
+			socketFactory: () => ws,
+			fetchImpl: fetchWithCapture,
+			localStorage: createFakeStorage(),
+			workspaceId: "my-team",
+		});
+		ws.resolveOpen();
+
+		// Let async boot settle before mutating cwd.
+		await new Promise((resolve) => setTimeout(resolve, 50));
+
+		const result = await store.setCwd("arch-rewrite");
+		expect(result).toMatchObject({ ok: true, cwd: "arch-rewrite" });
+		expect(capturedBody).toEqual({ cwd: "arch-rewrite", workspaceId: "my-team" });
+
+		store.dispose();
+	});
 });
diff --git a/src/app/ErrorModal.svelte b/src/app/ErrorModal.svelte
new file mode 100644
index 0000000..7fc09a6
--- /dev/null
+++ b/src/app/ErrorModal.svelte
@@ -0,0 +1,151 @@
+<script lang="ts">
+	/**
+	 * Full-screen error modal — surfaces critical errors that would otherwise be
+	 * silently swallowed (e.g. the cross-device tab-restore fetch failing). Shows
+	 * the full error text + stack trace in a scrollable `<pre>`, a Copy button
+	 * (clipboard), and an X to dismiss. Pure presentation: the error string and
+	 * dismiss callback are injected as props.
+	 */
+	let {
+		error,
+		onDismiss,
+	}: {
+		error: string;
+		onDismiss: () => void;
+	} = $props();
+
+	let copied = $state(false);
+	let copyTimer: ReturnType<typeof setTimeout> | undefined;
+
+	async function handleCopy(): Promise<void> {
+		try {
+			await navigator.clipboard.writeText(error);
+			copied = true;
+			clearTimeout(copyTimer);
+			copyTimer = setTimeout(() => {
+				copied = false;
+			}, 2000);
+		} catch {
+			// Clipboard API may be unavailable (non-secure context). Fallback:
+			// select the text so the user can Ctrl+C manually.
+			const pre = document.getElementById("error-modal-text");
+			if (pre !== null) {
+				const range = document.createRange();
+				range.selectNodeContents(pre);
+				const selection = window.getSelection();
+				selection?.removeAllRanges();
+				selection?.addRange(range);
+			}
+		}
+	}
+
+	function handleKeydown(event: KeyboardEvent): void {
+		if (event.key === "Escape") {
+			event.preventDefault();
+			onDismiss();
+		}
+	}
+</script>
+
+<svelte:window onkeydown={handleKeydown} />
+
+<!-- Full-screen overlay: fixed, high z-index, semi-transparent backdrop. -->
+<!-- svelte-ignore a11y_no_static_element_interactions -->
+<div
+	class="fixed inset-0 z-50 flex items-center justify-center bg-black/60 p-4"
+	role="dialog"
+	aria-modal="true"
+	aria-label="Error"
+>
+	<div class="flex max-h-[80vh] w-full max-w-2xl flex-col rounded-lg bg-base-100 shadow-xl">
+		<!-- Header -->
+		<div class="flex items-center justify-between border-b border-base-300 px-4 py-3">
+			<div class="flex items-center gap-2">
+				<svg
+					xmlns="http://www.w3.org/2000/svg"
+					fill="none"
+					viewBox="0 0 24 24"
+					stroke-width="2"
+					stroke="currentColor"
+					class="size-5 text-error"
+					aria-hidden="true"
+				>
+					<path
+						stroke-linecap="round"
+						stroke-linejoin="round"
+						d="M12 9v3.75m-9.303 3.376c-.866 1.5.217 3.374 1.948 3.374h14.71c1.73 0 2.813-1.874 1.948-3.374L13.949 3.378c-.866-1.5-3.032-1.5-3.898 0L2.697 16.126ZM12 15.75h.007v.008H12v-.008Z"
+					/>
+				</svg>
+				<h2 class="text-lg font-semibold text-error">Something went wrong</h2>
+			</div>
+			<button
+				type="button"
+				class="btn btn-ghost btn-sm btn-square"
+				aria-label="Dismiss error"
+				onclick={onDismiss}
+			>
+				<svg
+					xmlns="http://www.w3.org/2000/svg"
+					fill="none"
+					viewBox="0 0 24 24"
+					stroke-width="2"
+					stroke="currentColor"
+					class="size-5"
+					aria-hidden="true"
+				>
+					<path stroke-linecap="round" stroke-linejoin="round" d="M6 18 18 6M6 6l12 12" />
+				</svg>
+			</button>
+		</div>
+
+		<!-- Body: scrollable error text -->
+		<div class="overflow-auto p-4">
+			<pre
+				id="error-modal-text"
+				class="whitespace-pre-wrap break-words font-mono text-xs leading-relaxed opacity-80"
+			>{error}</pre>
+		</div>
+
+		<!-- Footer: copy button -->
+		<div class="flex items-center justify-between gap-2 border-t border-base-300 px-4 py-3">
+			<span class="text-xs opacity-50">Press Esc to dismiss</span>
+			<button
+				type="button"
+				class="btn btn-sm {copied ? 'btn-success' : 'btn-outline'}"
+				onclick={handleCopy}
+			>
+				{#if copied}
+					<svg
+						xmlns="http://www.w3.org/2000/svg"
+						fill="none"
+						viewBox="0 0 24 24"
+						stroke-width="2"
+						stroke="currentColor"
+						class="size-4"
+						aria-hidden="true"
+					>
+						<path stroke-linecap="round" stroke-linejoin="round" d="m4.5 12.75 6 6 9-13.5" />
+					</svg>
+					Copied
+				{:else}
+					<svg
+						xmlns="http://www.w3.org/2000/svg"
+						fill="none"
+						viewBox="0 0 24 24"
+						stroke-width="2"
+						stroke="currentColor"
+						class="size-4"
+						aria-hidden="true"
+					>
+						<path
+							stroke-linecap="round"
+							stroke-linejoin="round"
+							d="M15.75 17.25v3.375c0 .621-.504 1.125-1.125 1.125h-9.75a1.125 1.125 0 0 1-1.125-1.125V7.875c0-.621.504-1.125 1.125-1.125H6.75a9.06 9.06 0 0 1 1.5.124m7.5 10.376h3.375c.621 0 1.125-.504 1.125-1.125V11.25c0-4.46-3.243-8.161-7.5-8.876a9.06 9.06 0 0 0-1.5-.124H9.375c-.621 0-1.125.504-1.125 1.125v3.5m7.5 10.375H9.375a1.125 1.125 0 0 1-1.125-1.125v-9.25m18 3.75h-3.75m3.75 0-2.25 2.25m2.25-2.25 2.25 2.25M4.5 6.75 6.75 4.5"
+						/>
+					</svg>
+					Copy
+				{/if}
+			</button>
+		</div>
+	</div>
+</div>
diff --git a/src/app/store.svelte.ts b/src/app/store.svelte.ts
index 6cff5f8..daba83f 100644
--- a/src/app/store.svelte.ts
+++ b/src/app/store.svelte.ts
@@ -11,19 +11,27 @@ import type {
 	ConversationStatusChangedMessage,
 	CwdResponse,
 	LspStatusResponse,
+	McpStatusResponse,
 	ModelMetadata,
+	ModelResponse,
 	ModelsResponse,
 	ReasoningEffort,
 	ReasoningEffortResponse,
 	SetCompactPercentRequest,
 	SetCwdRequest,
+	SetModelRequest,
 	SetReasoningEffortRequest,
+	SetSystemPromptTemplateRequest,
 	SetTitleRequest,
+	SystemPromptTemplateResponse,
+	SystemPromptVariable,
+	SystemPromptVariablesResponse,
 	WarmRequest,
 	WarmResponse,
 } from "@dispatch/transport-contract";
 import type { SubscribeMessage, SurfaceServerMessage, SurfaceSpec } from "@dispatch/ui-contract";
 import type { ConversationStatus } from "@dispatch/wire";
+import { untrack } from "svelte";
 import { createIdbChunkStore } from "../adapters/idb";
 import { createLocalStore } from "../adapters/local-storage";
 import type { WebSocketLike } from "../adapters/ws";
@@ -65,6 +73,11 @@ export type LspResult =
 	| { readonly ok: true; readonly response: LspStatusResponse }
 	| { readonly ok: false; readonly error: string };
 
+/** Outcome of `GET /conversations/:id/mcp`. */
+export type McpResult =
+	| { readonly ok: true; readonly response: McpStatusResponse }
+	| { readonly ok: false; readonly error: string };
+
 /** Outcome of `PUT /conversations/:id/reasoning-effort`. */
 export type ReasoningEffortResult =
 	| { readonly ok: true; readonly reasoningEffort: ReasoningEffort }
@@ -80,6 +93,19 @@ export type CompactPercentResult =
 	| { readonly ok: true; readonly percent: number }
 	| { readonly ok: false; readonly error: string };
 
+/** Outcome of `GET /system-prompt` (global template load). */
+export type SystemPromptLoadResult =
+	| { readonly ok: true; readonly template: string }
+	| { readonly ok: false; readonly error: string };
+
+/** Outcome of `PUT /system-prompt` (global template save). */
+export type SystemPromptSaveResult = SystemPromptLoadResult;
+
+/** Outcome of `GET /system-prompt/variables` (variable catalog). */
+export type SystemPromptVariablesResult =
+	| { readonly ok: true; readonly variables: readonly SystemPromptVariable[] }
+	| { readonly ok: false; readonly error: string };
+
 /** Outcome of persisting a chat-limit setting (localStorage; FE-local). */
 export type ChatLimitResult =
 	| { readonly ok: true; readonly chatLimit: number }
@@ -88,6 +114,8 @@ export type ChatLimitResult =
 export interface AppStore {
 	readonly tabs: readonly Tab[];
 	readonly activeConversationId: string | null;
+	/** The workspace currently in view (URL slug); tabs are filtered to it. */
+	readonly activeWorkspaceId: string;
 	readonly activeChat: ChatStore;
 	readonly models: readonly string[];
 	/** Per-model metadata (contextWindow, etc.) from `GET /models`. */
@@ -113,6 +141,8 @@ export interface AppStore {
 	queueMessage(text: string): void;
 	selectModel(model: string): void;
 	newDraft(): void;
+	/** Switch the active workspace (on route change) + reset to a fresh draft in it. */
+	setActiveWorkspace(workspaceId: string): void;
 	selectTab(conversationId: string): void;
 	closeTab(conversationId: string): void;
 	renameTab(conversationId: string, title: string): void;
@@ -174,6 +204,30 @@ export interface AppStore {
 	 * The backend lazily spawns servers, so this may take a moment on the first call for a cwd.
 	 */
 	lspStatus(): Promise<LspResult | null>;
+	/**
+	 * Fetch the workspace conversation's MCP server status (`GET /conversations/:id/mcp`).
+	 * Mirrors the LSP status endpoint: returns `{cwd, servers}` with empty `servers`
+	 * when no cwd is set; the backend lazily connects servers, so this may take a
+	 * moment on the first call for a cwd.
+	 */
+	mcpStatus(): Promise<McpResult | null>;
+	/**
+	 * Load the global system prompt template (`GET /system-prompt`). The template is
+	 * conversation-agnostic; it is resolved once per conversation on first turn and
+	 * persisted for prompt-cache safety.
+	 */
+	loadSystemPrompt(): Promise<SystemPromptLoadResult>;
+	/**
+	 * Persist the global system prompt template (`PUT /system-prompt`). Changes apply
+	 * to new conversations on their first turn; existing conversations keep their
+	 * resolved system prompt until compaction.
+	 */
+	setSystemPrompt(template: string): Promise<SystemPromptSaveResult>;
+	/**
+	 * Load the static catalog of available system prompt variables (`GET /system-prompt/variables`).
+	 * Used by the builder to render the variable selector buttons.
+	 */
+	loadSystemPromptVariables(): Promise<SystemPromptVariablesResult>;
 	/** The persisted chat limit (max loaded chunks per conversation). */
 	readonly chatLimit: number;
 	/**
@@ -199,6 +253,14 @@ export interface AppStore {
 	 * bottom).
 	 */
 	attachUnloadGate(gate: () => boolean): void;
+	/**
+	 * A critical error that blocks normal operation (e.g. the cross-device tab
+	 * restore fetch failed). When non-null, a full-screen modal is shown with the
+	 * error details. Cleared by `clearFatalError` (the modal's dismiss button).
+	 */
+	readonly fatalError: string | null;
+	/** Dismiss the fatal error (called by the error modal's X button). */
+	clearFatalError(): void;
 	dispose(): void;
 }
 
@@ -210,6 +272,8 @@ export interface CreateAppStoreOptions {
 	indexedDB?: IDBFactory;
 	conversationId?: string;
 	localStorage?: Storage;
+	/** The workspace to scope to at boot (its URL slug); "default" if absent. */
+	workspaceId?: string;
 }
 
 function createHistorySync(httpBase: string, fetchImpl: typeof fetch): HistorySync {
@@ -241,6 +305,12 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 	let models = $state<readonly string[]>([]);
 	let modelInfo = $state<Readonly<Record<string, ModelMetadata>>>({});
 	let activeModel = $state(DEFAULT_MODEL);
+	let fatalError = $state<string | null>(null);
+
+	// The workspace currently in view (its URL slug); "default" until routing
+	// sets it. Tabs are filtered to this workspace; a new conversation is stamped
+	// with it on `chat.send`.
+	let activeWorkspaceId = $state<string>(opts?.workspaceId ?? "default");
 
 	const wsLocation = typeof location !== "undefined" ? location : undefined;
 	const wsUrl =
@@ -297,10 +367,11 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 
 	const chatStores = new Map<string, ChatStore>();
 
-	function createChatFor(conversationId: string, model: string): ChatStore {
+	function createChatFor(conversationId: string, model: string, workspaceId: string): ChatStore {
 		return createChatStore({
 			conversationId,
 			model,
+			workspaceId,
 			transport: {
 				send(msg) {
 					socket?.send(msg);
@@ -315,11 +386,22 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			// `setChatLimit`.
 			chatLimit: normalizeChatLimit(chatLimitStore.load()),
 			canUnload: () => (unloadGate === null ? true : unloadGate()),
+			onError: (context, err) => {
+				reportError(`${context} (conversation: ${conversationId})`, err);
+			},
 		});
 	}
 
 	const initialDraftId = randomId();
-	let draftStore: ChatStore = createChatFor(initialDraftId, DEFAULT_MODEL);
+	// Read `activeWorkspaceId` with untrack to suppress Svelte's
+	// `state_referenced_locally` warning — this intentionally captures the
+	// INITIAL workspace for the boot draft. When the workspace changes later,
+	// `setActiveWorkspace` creates a fresh draft store with the new id.
+	let draftStore: ChatStore = createChatFor(
+		initialDraftId,
+		DEFAULT_MODEL,
+		untrack(() => activeWorkspaceId),
+	);
 	let draftConversationId: string = initialDraftId;
 
 	let activeChat = $state<ChatStore>(draftStore as ChatStore);
@@ -337,8 +419,31 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			const data = (await res.json()) as CwdResponse;
 			// Guard a slow response losing a race with a conversation switch.
 			if (workspaceConversationId() === id) cwd = data.cwd ?? null;
-		} catch {
-			// Non-fatal: a cwd fetch failure just leaves the prior value.
+		} catch (err) {
+			reportError("Failed to load working directory", err);
+		}
+	}
+
+	/** Refetch the workspace conversation's persisted model (works for a draft too). */
+	async function refreshModel(): Promise<void> {
+		const id = workspaceConversationId();
+		try {
+			const res = await fetchImpl(`${httpBase}/conversations/${encodeURIComponent(id)}/model`);
+			if (!res.ok) return;
+			const data = (await res.json()) as ModelResponse;
+			if (workspaceConversationId() !== id) return;
+			if (typeof data.model === "string" && data.model.length > 0) {
+				activeModel = data.model;
+				const activeId = tabsStore.activeConversationId;
+				if (activeId !== null) {
+					tabsStore.setModel(activeId, data.model);
+					chatStores.get(activeId)?.setModel(data.model);
+				} else {
+					draftStore.setModel(data.model);
+				}
+			}
+		} catch (err) {
+			reportError("Failed to load model", err);
 		}
 	}
 
@@ -360,8 +465,8 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			const data = (await res.json()) as ReasoningEffortResponse;
 			// Guard a slow response losing a race with a conversation switch.
 			if (workspaceConversationId() === id) reasoningEffort = data.reasoningEffort ?? null;
-		} catch {
-			// Non-fatal: an effort fetch failure just leaves the default rendering.
+		} catch (err) {
+			reportError("Failed to load reasoning effort", err);
 		}
 	}
 
@@ -380,8 +485,8 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			if (!res.ok) return;
 			const data = (await res.json()) as CompactPercentResponse;
 			if (workspaceConversationId() === id) compactPercent = data.threshold;
-		} catch {
-			// Non-fatal: a percent fetch failure just leaves null.
+		} catch (err) {
+			reportError("Failed to load compact percent", err);
 		}
 	}
 
@@ -448,8 +553,8 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 	function closeConversation(conversationId: string): void {
 		void fetchImpl(`${httpBase}/conversations/${encodeURIComponent(conversationId)}/close`, {
 			method: "POST",
-		}).catch(() => {
-			// Non-fatal — see doc comment.
+		}).catch((err) => {
+			reportError("Failed to close conversation", err);
 		});
 	}
 
@@ -513,14 +618,17 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 
 	/**
 	 * Open a conversation tab — used by the `conversation.open` WS broadcast
-	 * (CLI `--open` flag). If the conversation is already open, this is a no-op;
-	 * otherwise create a chat store, load its history, subscribe to its live
+	 * (CLI `--open` flag) and by `conversation.statusChanged` when a new active
+	 * conversation is discovered. If the conversation is already open, this is a
+	 * no-op; otherwise create a chat store, load its history, subscribe to its live
 	 * turns, and add the tab WITHOUT switching the active conversation (the user
-	 * stays on their current tab; the new tab appears in the strip).
+	 * stays on their current tab; the new tab appears in the strip). The tab is
+	 * stamped with the conversation's actual `workspaceId`, NOT the viewer's
+	 * currently active workspace.
 	 */
-	function openConversation(conversationId: string): void {
+	function openConversation(conversationId: string, workspaceId: string): void {
 		if (chatStores.has(conversationId)) return;
-		const store = createChatFor(conversationId, activeModel);
+		const store = createChatFor(conversationId, activeModel, workspaceId);
 		chatStores.set(conversationId, store);
 		void store.load();
 		subscribeChat(conversationId);
@@ -528,6 +636,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			conversationId,
 			model: activeModel,
 			title: "Conversation",
+			workspaceId,
 		});
 	}
 
@@ -552,6 +661,20 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 		void refreshCompactPercent();
 	}
 
+	/**
+	 * Surface a swallowed error to the user via the full-screen error modal
+	 * (`fatalError` → `ErrorModal`). Logs to `console.error` too so the stack is
+	 * in devtools. Called from catch blocks that previously swallowed errors silently.
+	 */
+	function reportError(context: string, err: unknown): void {
+		console.error(`[reportError] ${context}`, err);
+		const detail =
+			err instanceof Error
+				? `${err.name}: ${err.message}\n\n${err.stack ?? "(no stack trace available)"}`
+				: String(err);
+		fatalError = `${context}\n\n${detail}`;
+	}
+
 	// Conversation lifecycle status (backend-owned, pushed via WS +
 	// fetched on connect). Keyed by conversationId.
 	let conversationStatuses = $state<Map<string, ConversationStatus>>(new Map());
@@ -580,7 +703,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			const existingIds = new Set(chatStores.keys());
 			for (const conv of data.conversations) {
 				if (!existingIds.has(conv.id)) {
-					const store = createChatFor(conv.id, activeModel);
+					const store = createChatFor(conv.id, activeModel, conv.workspaceId);
 					chatStores.set(conv.id, store);
 					void store.load();
 					subscribeChat(conv.id);
@@ -588,6 +711,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 						conversationId: conv.id,
 						model: activeModel,
 						title: conv.title,
+						workspaceId: conv.workspaceId,
 					});
 				} else {
 					// Already open — update the title from the backend if it differs.
@@ -602,8 +726,11 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 					removeTabLocally(tab.conversationId);
 				}
 			}
-		} catch {
-			// Non-fatal: fall back to the localStorage-restored tabs.
+		} catch (err) {
+			reportError(
+				`Failed to load conversations from the backend.\n\nURL: ${httpBase}/conversations?status=active,idle`,
+				err,
+			);
 		}
 	}
 
@@ -612,10 +739,10 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 		onMessage: handleServerMessage,
 		onChat: handleChatMessage,
 		onConversationOpen(msg: ConversationOpenMessage): void {
-			openConversation(msg.conversationId);
+			openConversation(msg.conversationId, msg.workspaceId);
 		},
 		onConversationStatusChanged(msg: ConversationStatusChangedMessage): void {
-			const { conversationId, status } = msg;
+			const { conversationId, status, workspaceId } = msg;
 			if (status === "closed") {
 				// Closed on another device (or the backend) — remove the tab locally.
 				if (chatStores.has(conversationId)) {
@@ -627,7 +754,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			conversationStatuses = new Map(conversationStatuses).set(conversationId, status);
 			// If this is a new active conversation we don't have a tab for, open one.
 			if (status === "active" && !chatStores.has(conversationId)) {
-				openConversation(conversationId);
+				openConversation(conversationId, workspaceId);
 			}
 		},
 		onConversationCompacted(msg: ConversationCompactedMessage): void {
@@ -641,7 +768,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 				store.dispose();
 			}
 			void cache.delete(cid);
-			const fresh = createChatFor(cid, activeModel);
+			const fresh = createChatFor(cid, activeModel, activeWorkspaceId);
 			chatStores.set(cid, fresh);
 			void fresh.load();
 			if (wasActive) {
@@ -692,15 +819,15 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 				}
 			}
 		})
-		.catch(() => {
-			// Model fetch failure is non-fatal; use defaults.
+		.catch((err) => {
+			reportError("Failed to load model list", err);
 		});
 
 	// Restore persisted tabs
 	const persistedState = storageAdapter.load();
 	if (persistedState !== null && persistedState.tabs.length > 0) {
 		for (const tab of persistedState.tabs) {
-			const store = createChatFor(tab.conversationId, tab.model);
+			const store = createChatFor(tab.conversationId, tab.model, tab.workspaceId);
 			chatStores.set(tab.conversationId, store);
 			void store.load();
 			// Watch each restored conversation's live turns: after a reload mid-turn the
@@ -720,6 +847,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 
 	refreshActiveChat();
 	void refreshCwd();
+	void refreshModel();
 	void refreshReasoningEffort();
 	void refreshCompactPercent();
 
@@ -730,11 +858,29 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 
 	return {
 		get tabs(): readonly Tab[] {
-			return tabsStore.tabs;
+			return tabsStore.tabs.filter((t) => t.workspaceId === activeWorkspaceId);
 		},
 		get activeConversationId(): string | null {
 			return tabsStore.activeConversationId;
 		},
+		get activeWorkspaceId(): string {
+			return activeWorkspaceId;
+		},
+		setActiveWorkspace(workspaceId: string): void {
+			activeWorkspaceId = workspaceId;
+			// Reset to a fresh draft scoped to the new workspace so a new chat is
+			// stamped with the right `workspaceId` on `chat.send`.
+			const nextDraftId = randomId();
+			draftStore = createChatFor(nextDraftId, activeModel, workspaceId);
+			draftConversationId = nextDraftId;
+			tabsStore.newDraft();
+			refreshActiveChat();
+			syncSubscriptions();
+			void refreshCwd();
+			void refreshModel();
+			void refreshReasoningEffort();
+			void refreshCompactPercent();
+		},
 		get activeChat(): ChatStore {
 			return activeChat;
 		},
@@ -796,13 +942,14 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 					conversationId,
 					model,
 					title: deriveTitle(text),
+					workspaceId: activeWorkspaceId,
 				});
 				chatStores.set(conversationId, draftStore);
 				void draftStore.load();
 
 				// Prepare next draft
 				const nextDraftId = randomId();
-				draftStore = createChatFor(nextDraftId, activeModel);
+				draftStore = createChatFor(nextDraftId, activeModel, activeWorkspaceId);
 				draftConversationId = nextDraftId;
 
 				refreshActiveChat();
@@ -834,6 +981,13 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			if (activeId !== null) {
 				tabsStore.setModel(activeId, model);
 				chatStores.get(activeId)?.setModel(model);
+				void fetchImpl(`${httpBase}/conversations/${encodeURIComponent(activeId)}/model`, {
+					method: "PUT",
+					headers: { "Content-Type": "application/json" },
+					body: JSON.stringify({ model } satisfies SetModelRequest),
+				}).catch((err) => {
+					reportError("Failed to persist model", err);
+				});
 			} else {
 				draftStore.setModel(model);
 			}
@@ -842,11 +996,12 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 		newDraft(): void {
 			tabsStore.newDraft();
 			const nextDraftId = randomId();
-			draftStore = createChatFor(nextDraftId, activeModel);
+			draftStore = createChatFor(nextDraftId, activeModel, activeWorkspaceId);
 			draftConversationId = nextDraftId;
 			refreshActiveChat();
 			syncSubscriptions();
 			void refreshCwd();
+			void refreshModel();
 			void refreshReasoningEffort();
 			void refreshCompactPercent();
 		},
@@ -860,6 +1015,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			refreshActiveChat();
 			syncSubscriptions();
 			void refreshCwd();
+			void refreshModel();
 			void refreshReasoningEffort();
 			void refreshCompactPercent();
 		},
@@ -877,8 +1033,8 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 				method: "PUT",
 				headers: { "Content-Type": "application/json" },
 				body: JSON.stringify({ title } satisfies SetTitleRequest),
-			}).catch(() => {
-				// Best-effort — the local tab is already renamed.
+			}).catch((err) => {
+				reportError("Failed to rename conversation", err);
 			});
 		},
 
@@ -918,7 +1074,10 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 
 		async setCwd(value: string): Promise<CwdResult | null> {
 			const id = workspaceConversationId();
-			const body: SetCwdRequest = { cwd: value };
+			const body: SetCwdRequest = {
+				cwd: value,
+				workspaceId: untrack(() => activeWorkspaceId),
+			};
 			try {
 				const res = await fetchImpl(`${httpBase}/conversations/${encodeURIComponent(id)}/cwd`, {
 					method: "PUT",
@@ -974,8 +1133,8 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			if (conversationId === null) return;
 			void fetchImpl(`${httpBase}/conversations/${encodeURIComponent(conversationId)}/stop`, {
 				method: "POST",
-			}).catch(() => {
-				// Non-fatal — the existing event flow handles the turn settle.
+			}).catch((err) => {
+				reportError("Failed to stop generation", err);
 			});
 		},
 
@@ -1082,10 +1241,108 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 				};
 			}
 		},
+
+		async mcpStatus(): Promise<McpResult | null> {
+			const id = workspaceConversationId();
+			try {
+				const res = await fetchImpl(`${httpBase}/conversations/${encodeURIComponent(id)}/mcp`);
+				if (!res.ok) {
+					const errBody = (await res.json().catch(() => null)) as { error?: string } | null;
+					return { ok: false, error: errBody?.error ?? `MCP status failed (HTTP ${res.status})` };
+				}
+				// Normalize the untyped body at this network seam so a malformed/partial
+				// response can never crash the renderer (servers is guaranteed an array).
+				const data = (await res.json()) as Partial<McpStatusResponse>;
+				const response: McpStatusResponse = {
+					conversationId: data.conversationId ?? id,
+					cwd: data.cwd ?? null,
+					servers: Array.isArray(data.servers) ? data.servers : [],
+				};
+				return { ok: true, response };
+			} catch (err) {
+				return {
+					ok: false,
+					error: err instanceof Error ? err.message : "MCP status request failed",
+				};
+			}
+		},
+
+		async loadSystemPrompt(): Promise<SystemPromptLoadResult> {
+			try {
+				const res = await fetchImpl(`${httpBase}/system-prompt`);
+				if (!res.ok) {
+					const errBody = (await res.json().catch(() => null)) as { error?: string } | null;
+					return {
+						ok: false,
+						error: errBody?.error ?? `Load system prompt failed (HTTP ${res.status})`,
+					};
+				}
+				const data = (await res.json()) as SystemPromptTemplateResponse;
+				return { ok: true, template: data.template ?? "" };
+			} catch (err) {
+				return {
+					ok: false,
+					error: err instanceof Error ? err.message : "Load system prompt request failed",
+				};
+			}
+		},
+
+		async setSystemPrompt(template: string): Promise<SystemPromptSaveResult> {
+			try {
+				const body: SetSystemPromptTemplateRequest = { template };
+				const res = await fetchImpl(`${httpBase}/system-prompt`, {
+					method: "PUT",
+					headers: { "content-type": "application/json" },
+					body: JSON.stringify(body),
+				});
+				if (!res.ok) {
+					const errBody = (await res.json().catch(() => null)) as { error?: string } | null;
+					return {
+						ok: false,
+						error: errBody?.error ?? `Set system prompt failed (HTTP ${res.status})`,
+					};
+				}
+				const data = (await res.json()) as SystemPromptTemplateResponse;
+				return { ok: true, template: data.template };
+			} catch (err) {
+				return {
+					ok: false,
+					error: err instanceof Error ? err.message : "Set system prompt request failed",
+				};
+			}
+		},
+
+		async loadSystemPromptVariables(): Promise<SystemPromptVariablesResult> {
+			try {
+				const res = await fetchImpl(`${httpBase}/system-prompt/variables`);
+				if (!res.ok) {
+					const errBody = (await res.json().catch(() => null)) as { error?: string } | null;
+					return {
+						ok: false,
+						error: errBody?.error ?? `Load system prompt variables failed (HTTP ${res.status})`,
+					};
+				}
+				const data = (await res.json()) as Partial<SystemPromptVariablesResponse>;
+				return { ok: true, variables: Array.isArray(data.variables) ? data.variables : [] };
+			} catch (err) {
+				return {
+					ok: false,
+					error: err instanceof Error ? err.message : "Load system prompt variables request failed",
+				};
+			}
+		},
+
 		attachUnloadGate(gate: () => boolean): void {
 			unloadGate = gate;
 		},
 
+		get fatalError(): string | null {
+			return fatalError;
+		},
+		clearFatalError(): void {
+			fatalError = null;
+		},
+
 		dispose(): void {
 			for (const store of chatStores.values()) {
 				store.dispose();
diff --git a/src/app/store.test.ts b/src/app/store.test.ts
index db6fdaa..5711442 100644
--- a/src/app/store.test.ts
+++ b/src/app/store.test.ts
@@ -103,6 +103,7 @@ function reconnectableSocket(): ReconnectableSocket {
 interface FakeFetchOptions {
 	models?: readonly string[];
 	history?: Record<string, ConversationHistoryResponse>;
+	model?: string | null;
 }
 
 function fakeFetchImpl(opts?: FakeFetchOptions): typeof fetch {
@@ -113,6 +114,15 @@ function fakeFetchImpl(opts?: FakeFetchOptions): typeof fetch {
 		if (url.endsWith("/models")) {
 			return new Response(JSON.stringify({ models }), { status: 200 });
 		}
+		if (url.endsWith("/model")) {
+			return new Response(
+				JSON.stringify({
+					conversationId: "ignored",
+					model: opts?.model ?? null,
+				}),
+				{ status: 200 },
+			);
+		}
 		const body =
 			history[url] ?? ({ chunks: [], latestSeq: 0 } satisfies ConversationHistoryResponse);
 		return new Response(JSON.stringify(body), { status: 200 });
@@ -583,20 +593,64 @@ describe("createAppStore", () => {
 		store.dispose();
 	});
 
-	it("selecting a model updates the active tab", () => {
+	it("selecting a model persists it to the backend", () => {
 		const ws = fakeSocket();
+		const fetchImpl = fakeFetchImpl();
 		const store = createAppStore({
 			socketFactory: () => ws,
-			fetchImpl: fakeFetchImpl(),
+			fetchImpl,
 			localStorage: createFakeStorage(),
 		});
 		ws.resolveOpen();
 
 		store.send("hello");
-
 		store.selectModel("openai/gpt-4o");
 
-		expect(store.activeModel).toBe("openai/gpt-4o");
+		const put = vi.fn().mockResolvedValue(
+			new Response(JSON.stringify({ conversationId: "ignored", model: "openai/gpt-4o" }), {
+				status: 200,
+			}),
+		);
+		const capturingStore = createAppStore({
+			socketFactory: () => fakeSocket(),
+			fetchImpl: async (input, init) => {
+				const url =
+					typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
+				if (init?.method === "PUT" && url.endsWith("/model")) {
+					put(url, init);
+				}
+				return fetchImpl(input, init);
+			},
+			localStorage: createFakeStorage(),
+		});
+		capturingStore.send("hello");
+		capturingStore.selectModel("openai/gpt-4o");
+
+		expect(put).toHaveBeenCalledOnce();
+		const [callUrl, callInit] = put.mock.calls[0] as [string, RequestInit];
+		expect(callUrl.endsWith("/model")).toBe(true);
+		expect(JSON.parse(callInit.body as string)).toEqual({ model: "openai/gpt-4o" });
+
+		store.dispose();
+		capturingStore.dispose();
+	});
+
+	it("focuses a conversation with a persisted model", async () => {
+		const ws = fakeSocket();
+		const store = createAppStore({
+			socketFactory: () => ws,
+			fetchImpl: fakeFetchImpl({ model: "openai/gpt-4o" }),
+			localStorage: createFakeStorage(),
+		});
+		ws.resolveOpen();
+
+		store.send("first message");
+
+		// New tab opens with the default model until the persisted-model fetch resolves.
+		expect(store.activeModel).toBe("opencode/deepseek-v4-flash");
+
+		// Wait for the persisted model fetch to resolve.
+		await vi.waitFor(() => expect(store.activeModel).toBe("openai/gpt-4o"));
 		expect(store.tabs[0]?.model).toBe("openai/gpt-4o");
 
 		store.dispose();