feat(workspace,smart-scroll): per-conversation cwd + LSP view; smart auto-scroll

workspace ([email protected]): a cwd field in the Model sidebar view (GET/PUT /conversations/:id/cwd) + a new 'Language Servers' view (GET /conversations/:id/lsp) with per-server connected/starting/error badges, spinner, error text, and refresh. Store-owned reactive cwd, re-seeded on focus change; works for DRAFTS too (targets the draft's client-minted id, which survives promotion, so turn 1 runs in the chosen cwd). Network seam normalizes the untyped LSP body.

smart-scroll: pure stick-to-bottom reducer + injected controller shell (scroll/scrollend + a ResizeObserver on the content so the view follows async height changes — markdown/highlight, images, collapses, viewport reflow), plus a floating scroll-to-bottom button. FIX: restore the transcript scrollbar — the refactor moved overflow-y-auto to an inner child, so the flex-1 container needed min-h-0 to constrain instead of growing to content.

harness: vitest-setup polyfills Element.scrollTo + ResizeObserver (jsdom implements neither), fixing App component tests. docs: backend-handoff pruned (CR-3 resolved/removed); added cwd/LSP verification courier (backend confirmed all 6 asks ✅); removed the resolved cache-warming-timer courier.

Verified: svelte-check 0 errors, biome clean, 523 tests pass, vite build OK.

3 files changed, 204 insertions, 7 deletions

diff --git a/src/app/App.svelte b/src/app/App.svelte
index dae6177..daab953 100644
--- a/src/app/App.svelte
+++ b/src/app/App.svelte
@@ -9,9 +9,21 @@
 	import { ChatView, Composer, manifest as chatManifest, ModelSelector } from "../features/chat";
 	import { manifest as conversationCacheManifest } from "../features/conversation-cache";
 	import { manifest as markdownManifest } from "../features/markdown";
+	import {
+		createSmartScrollController,
+		manifest as smartScrollManifest,
+		ScrollToBottom,
+	} from "../features/smart-scroll";
 	import { manifest as surfaceHostManifest, SurfaceView } from "../features/surface-host";
 	import { manifest as tabsManifest, TabBar } from "../features/tabs";
 	import { manifest as viewsManifest, ViewSidebar } from "../features/views";
+	import {
+		CwdField,
+		type CwdSaveResult,
+		LspStatusView,
+		type LspStatusResult,
+		manifest as workspaceManifest,
+	} from "../features/workspace";
 	import type { AppStore } from "./store.svelte";
 
 	let { store }: { store: AppStore } = $props();
@@ -26,12 +38,13 @@
 	// `viewContent` snippet below maps each kind id to its renderer.
 	const viewKinds = [
 		{ id: "model", label: "Model" },
+		{ id: "lsp", label: "Language Servers" },
 		{ id: "extensions", label: "Extensions" },
 		{ id: "cache-warming", label: "Cache Warming" },
 	] as const;
 
-	// Default sidebar layout: a Model panel on top, then Extensions, then Cache Warming.
-	const initialViews = ["model", "extensions", "cache-warming"] as const;
+	// Default sidebar layout: Model panel on top, then Language Servers, Extensions, Cache Warming.
+	const initialViews = ["model", "lsp", "extensions", "cache-warming"] as const;
 
 	// Frontend module list for the "Loaded Modules" view, AGGREGATED from each
 	// feature's public `manifest` export so it can't drift from what's actually
@@ -47,8 +60,38 @@
 		conversationCacheManifest,
 		markdownManifest,
 		cacheWarmingManifest,
+		workspaceManifest,
+		smartScrollManifest,
 	].map((m) => [m.name, m.description] as const);
 
+	// Smart-scroll: keep the transcript pinned to the bottom while it streams,
+	// unless the reader has scrolled up (then show a "scroll to bottom" button).
+	// One controller owns the chat scroll region; effects below feed it the edges.
+	const smartScroll = createSmartScrollController();
+	let transcriptEl = $state<HTMLElement | undefined>();
+	let transcriptContentEl = $state<HTMLElement | undefined>();
+
+	// Attach/detach the controller to the live scroll element + content (disposed on
+	// unmount). The content element is observed (ResizeObserver) so the view follows
+	// height changes that aren't a transcript append.
+	$effect(() => {
+		if (!transcriptEl) return;
+		return smartScroll.attach(transcriptEl, transcriptContentEl);
+	});
+
+	// New transcript content streamed in (or messages loaded) → follow the bottom
+	// while stuck. Reads `chunks.length` so the effect re-runs on every append.
+	$effect(() => {
+		void store.activeChat.chunks.length;
+		smartScroll.contentChanged();
+	});
+
+	// Conversation/tab switch → snap to the bottom of the new transcript.
+	$effect(() => {
+		void store.activeConversationId;
+		smartScroll.reset();
+	});
+
 	// Right sidebar: open by default on wide screens (pushes the chat aside),
 	// closed by default on narrow screens (overlays the chat). Initial state is
 	// derived from the viewport width once; the hamburger toggles it thereafter.
@@ -79,6 +122,21 @@
 				}
 			: { ok: false, error: result.error };
 	}
+
+	// Adapt the store's cwd/LSP results to the workspace feature's ports.
+	async function saveCwd(cwd: string): Promise<CwdSaveResult | null> {
+		const result = await store.setCwd(cwd);
+		if (result === null) return null;
+		return result.ok ? { ok: true, cwd: result.cwd } : { ok: false, error: result.error };
+	}
+
+	async function loadLspStatus(): Promise<LspStatusResult | null> {
+		const result = await store.lspStatus();
+		if (result === null) return null;
+		return result.ok
+			? { ok: true, cwd: result.response.cwd, servers: result.response.servers }
+			: { ok: false, error: result.error };
+	}
 </script>
 
 <main class="relative flex h-screen overflow-hidden">
@@ -134,10 +192,14 @@
 			</div>
 		{/if}
 
-		<div class="relative min-w-0 flex-1 overflow-y-auto">
-			{#key store.activeConversationId}
-				<ChatView chunks={store.activeChat.chunks} turnMetrics={store.activeChat.turnMetrics} />
-			{/key}
+		<div class="relative min-h-0 min-w-0 flex-1">
+			<div bind:this={transcriptEl} class="h-full overflow-y-auto">
+				<div bind:this={transcriptContentEl}>
+					{#key store.activeConversationId}
+						<ChatView chunks={store.activeChat.chunks} turnMetrics={store.activeChat.turnMetrics} />
+					{/key}
+				</div>
+			</div>
 			{#if store.activeChat.chunks.length === 0}
 				<div
 					class="pointer-events-none absolute inset-0 flex items-center justify-center"
@@ -146,6 +208,7 @@
 					<span class="select-none text-4xl font-bold opacity-10">Dispatch</span>
 				</div>
 			{/if}
+			<ScrollToBottom show={smartScroll.showButton} onResume={() => smartScroll.resume()} />
 		</div>
 
 		<Composer onSend={handleSend} />
@@ -185,7 +248,20 @@
 
 {#snippet viewContent(kind: string)}
 	{#if kind === "model"}
-		<ModelSelector models={store.models} selected={store.activeModel} onSelect={handleSelectModel} />
+		<div class="flex flex-col gap-3">
+			<ModelSelector models={store.models} selected={store.activeModel} onSelect={handleSelectModel} />
+			<!-- Keyed on the workspace conversation (active tab OR draft) so the input
+			     re-mounts per conversation — incl. switching between drafts — and can't
+			     bleed across tabs. Editable for a draft too (cwd applies from turn 1). -->
+			{#key store.currentConversationId}
+				<CwdField cwd={store.cwd} canEdit={true} save={saveCwd} />
+			{/key}
+		</div>
+	{:else if kind === "lsp"}
+		<!-- Re-mount per conversation (incl. draft) so the loaded server list is isolated. -->
+		{#key store.currentConversationId}
+			<LspStatusView cwd={store.cwd} canView={true} load={loadLspStatus} />
+		{/key}
 	{:else if kind === "extensions"}
 		<section>
 			<h3 class="mb-1 text-xs font-semibold uppercase opacity-60">Frontend modules</h3>
diff --git a/src/app/App.test.ts b/src/app/App.test.ts
index 1534d1c..d22f84b 100644
--- a/src/app/App.test.ts
+++ b/src/app/App.test.ts
@@ -62,6 +62,14 @@ function fakeFetchImpl(): typeof fetch {
 				status: 200,
 			});
 		}
+		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 });
 	};
 }
diff --git a/src/app/store.svelte.ts b/src/app/store.svelte.ts
index c242d77..6991530 100644
--- a/src/app/store.svelte.ts
+++ b/src/app/store.svelte.ts
@@ -3,7 +3,10 @@ import type {
 	ChatErrorMessage,
 	ConversationHistoryResponse,
 	ConversationMetricsResponse,
+	CwdResponse,
+	LspStatusResponse,
 	ModelsResponse,
+	SetCwdRequest,
 	WarmRequest,
 	WarmResponse,
 } from "@dispatch/transport-contract";
@@ -38,6 +41,16 @@ export type WarmResult =
 	| { readonly ok: true; readonly response: WarmResponse }
 	| { readonly ok: false; readonly error: string };
 
+/** Outcome of `PUT /conversations/:id/cwd`. */
+export type CwdResult =
+	| { readonly ok: true; readonly cwd: string | null }
+	| { readonly ok: false; readonly error: string };
+
+/** Outcome of `GET /conversations/:id/lsp`. */
+export type LspResult =
+	| { readonly ok: true; readonly response: LspStatusResponse }
+	| { readonly ok: false; readonly error: string };
+
 export interface AppStore {
 	readonly tabs: readonly Tab[];
 	readonly activeConversationId: string | null;
@@ -61,6 +74,20 @@ export interface AppStore {
 	 * Returns null when no conversation is focused (a draft has nothing to warm).
 	 */
 	warmNow(): Promise<WarmResult | null>;
+	/** The workspace conversation's persisted working directory, or null when unset. */
+	readonly cwd: string | null;
+	/** The conversation workspace settings target: the active tab, or the pending draft's id. */
+	readonly currentConversationId: string;
+	/**
+	 * Set the workspace conversation's working directory (`PUT /conversations/:id/cwd`).
+	 * Works for a draft too (its id survives promotion), so the first turn runs in it.
+	 */
+	setCwd(cwd: string): Promise<CwdResult | null>;
+	/**
+	 * Fetch the workspace conversation's language-server status (`GET /conversations/:id/lsp`).
+	 * The backend lazily spawns servers, so this may take a moment on the first call for a cwd.
+	 */
+	lspStatus(): Promise<LspResult | null>;
 	dispose(): void;
 }
 
@@ -160,6 +187,24 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 
 	let activeChat = $state<ChatStore>(draftStore as ChatStore);
 
+	// The active conversation's persisted working directory (per-tab). Seeded from
+	// the backend on focus change; null for a draft / when unset.
+	let cwd = $state<string | null>(null);
+
+	/** Refetch the workspace conversation's cwd into reactive state (works for a draft too). */
+	async function refreshCwd(): Promise<void> {
+		const id = workspaceConversationId();
+		try {
+			const res = await fetchImpl(`${httpBase}/conversations/${encodeURIComponent(id)}/cwd`);
+			if (!res.ok) return;
+			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.
+		}
+	}
+
 	function getActiveChat(): ChatStore {
 		const activeId = tabsStore.activeConversationId;
 		if (activeId === null) {
@@ -199,6 +244,16 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 		return tabsStore.activeConversationId ?? undefined;
 	}
 
+	/**
+	 * The conversation id workspace settings (cwd / LSP) target: the active tab, or
+	 * the pending draft's id when in draft mode. Unlike `focusedConversationId`, this
+	 * is NEVER undefined — the draft has a stable client-minted id that survives
+	 * promotion (first send), so a cwd set on a draft carries into the real turn.
+	 */
+	function workspaceConversationId(): string {
+		return tabsStore.activeConversationId ?? draftConversationId;
+	}
+
 	function handleServerMessage(msg: SurfaceServerMessage): void {
 		protocol = applyServerMessage(protocol, msg);
 		// Surfaces are auto-expanded: whenever the catalog changes, subscribe to
@@ -298,6 +353,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 	}
 
 	refreshActiveChat();
+	void refreshCwd();
 
 	return {
 		get tabs(): readonly Tab[] {
@@ -329,6 +385,12 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 		get lastError() {
 			return protocol.lastError;
 		},
+		get cwd(): string | null {
+			return cwd;
+		},
+		get currentConversationId(): string {
+			return workspaceConversationId();
+		},
 
 		surface(surfaceId: string): SurfaceSpec | null {
 			return getSurfaceSpec(protocol, surfaceId);
@@ -356,6 +418,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 				// The draft became a real conversation: re-scope conversation-scoped
 				// surfaces (e.g. cache-warming) to its id.
 				syncSubscriptions();
+				void refreshCwd();
 				// Now send on the promoted store
 				chatStores.get(conversationId)?.send(text);
 			} else {
@@ -381,6 +444,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			draftConversationId = nextDraftId;
 			refreshActiveChat();
 			syncSubscriptions();
+			void refreshCwd();
 		},
 
 		selectTab(conversationId: string): void {
@@ -391,6 +455,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			}
 			refreshActiveChat();
 			syncSubscriptions();
+			void refreshCwd();
 		},
 
 		closeTab(conversationId: string): void {
@@ -403,6 +468,7 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 			void cache.delete(conversationId);
 			refreshActiveChat();
 			syncSubscriptions();
+			void refreshCwd();
 		},
 
 		invoke(surfaceId: string, actionId: string, payload?: unknown): void {
@@ -438,6 +504,53 @@ export function createAppStore(opts?: CreateAppStoreOptions): AppStore {
 				return { ok: false, error: err instanceof Error ? err.message : "Warm request failed" };
 			}
 		},
+
+		async setCwd(value: string): Promise<CwdResult | null> {
+			const id = workspaceConversationId();
+			const body: SetCwdRequest = { cwd: value };
+			try {
+				const res = await fetchImpl(`${httpBase}/conversations/${encodeURIComponent(id)}/cwd`, {
+					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 cwd failed (HTTP ${res.status})` };
+				}
+				const data = (await res.json()) as CwdResponse;
+				const next = data.cwd ?? null;
+				if (workspaceConversationId() === id) cwd = next;
+				return { ok: true, cwd: next };
+			} catch (err) {
+				return { ok: false, error: err instanceof Error ? err.message : "Set cwd request failed" };
+			}
+		},
+
+		async lspStatus(): Promise<LspResult | null> {
+			const id = workspaceConversationId();
+			try {
+				const res = await fetchImpl(`${httpBase}/conversations/${encodeURIComponent(id)}/lsp`);
+				if (!res.ok) {
+					const errBody = (await res.json().catch(() => null)) as { error?: string } | null;
+					return { ok: false, error: errBody?.error ?? `LSP 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<LspStatusResponse>;
+				const response: LspStatusResponse = {
+					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 : "LSP status request failed",
+				};
+			}
+		},
 		dispose(): void {
 			for (const store of chatStores.values()) {
 				store.dispose();