Welcome modal: client-side example loading + cleanups

src/lib/components/WelcomeModal.svelte

@@ -17,9 +17,10 @@
 	interface Props {
 		onNew: () => void;
 		onClose: () => void;
+		onLoadExample: (url: string) => void;
 	}
 
-	let { onNew, onClose }: Props = $props();
+	let { onNew, onClose, onLoadExample }: Props = $props();
 
 	const examples: Example[] = [
 		{ filename: 'feedback-system.json', basename: 'feedback-system', name: 'Feedback System', description: 'Linear feedback system with delayed step excitation' },
@@ -97,7 +98,7 @@
 
 	<div class="banner-content">
 		<div class="version-info">
-			PathView {PATHVIEW_VERSION} · {Object.entries(EXTRACTED_VERSIONS).map(([pkg, ver]) => `${pkg.replace('_', '-')} ${ver}`).join(' · ')}
+			pathview {PATHVIEW_VERSION} · {Object.entries(EXTRACTED_VERSIONS).map(([pkg, ver]) => `${pkg.replace('_', '-')} ${ver}`).join(' · ')}
 		</div>
 
 		<div class="header">
@@ -165,12 +166,11 @@
 		<div class="examples-section">
 			<div class="examples-grid">
 				{#each examples as example}
-					<a
-					class="example-card"
-					href="?model={base}/examples/{example.filename}"
-					data-sveltekit-reload
-					onclick={onClose}
-				>
+					<button
+						type="button"
+						class="example-card"
+						onclick={() => onLoadExample(`${base}/examples/${example.filename}`)}
+					>
 						<div class="example-info">
 							<div class="example-name">{example.name}</div>
 							<div class="example-description">{example.description}</div>
@@ -184,7 +184,7 @@
 								onerror={(e) => { (e.currentTarget as HTMLImageElement).style.display = 'none'; }}
 							/>
 						</div>
-					</a>
+					</button>
 				{/each}
 			</div>
 		</div>

src/lib/pyodide/backend/index.ts

@@ -99,6 +99,12 @@ export const replState = {
 export async function init(): Promise<void> {
 	const backend = getBackend();
 
+	// Idempotent: several callers invoke init() (auto-detect, toolbox installer,
+	// first run, helper injection). The backend init itself is a no-op once
+	// ready, but logging/callback setup ran every time, producing repeated
+	// "Initializing Python REPL..." noise. Bail early when ready.
+	if (backend.isReady()) return;
+
 	// Set up console output callbacks
 	backend.onStdout((value) => consoleStore.output(value));
 	backend.onStderr((value) => consoleStore.error(value));

src/routes/+page.svelte

@@ -44,7 +44,7 @@
 	import { openNodeDialog } from '$lib/stores/nodeDialog';
 	import { openEventDialog } from '$lib/stores/eventDialog';
 	import type { MenuItemType } from '$lib/components/ContextMenu.svelte';
-	import { pyodideState, simulationState, initPyodide, stopSimulation, continueStreamingSimulation, stageMutations } from '$lib/pyodide/bridge';
+	import { pyodideState, simulationState, initPyodide, stopSimulation, continueStreamingSimulation, stageMutations, resetSimulation } from '$lib/pyodide/bridge';
 	import { pendingMutationCount } from '$lib/pyodide/mutationQueue';
 	import { initBackendFromUrl, autoDetectBackend } from '$lib/pyodide/backend';
 	import { runGraphStreamingSimulation, validateGraphSimulation, exportToPython } from '$lib/pyodide/pathsimRunner';
@@ -203,6 +203,11 @@
 	const urlModelConfig = getUrlModelConfig();
 	let showWelcomeModal = $state(!urlModelConfig); // Hide if loading from URL
 
+	// Backend-ready promise (assigned in onMount). Component-scoped so client-
+	// side example loading can gate its toolbox install on the running worker
+	// instead of forcing a full reload + Pyodide reinit.
+	let backendReady: Promise<unknown> | undefined = $state(undefined);
+
 	// Track widths directly - initialized on first dual-panel open
 	let consolePanelWidth = $state<number | undefined>(undefined);
 	let plotPanelWidth = $state<number | undefined>(undefined);
@@ -581,7 +586,7 @@
 		// to `registryVersion` bumps, so any (missing) placeholders upgrade
 		// themselves as soon as their toolbox registers.
 		seedPreloadedToolboxes();
-		const backendReady = (async () => {
+		backendReady = (async () => {
 			try {
 				await autoDetectBackend();
 				await initBackendFromUrl();
@@ -1231,6 +1236,32 @@
 		}
 	}
 
+	// Load an example/model client-side — no page reload, so the running
+	// Pyodide worker is reused (no reinit). Reflects the model in the URL via
+	// replaceState, so deep-links (?model=) still work and the URL stays
+	// shareable. Used by the welcome modal's example cards.
+	async function loadExample(url: string): Promise<void> {
+		showWelcomeModal = false;
+		// Clear previous results / REPL state; the worker stays up.
+		await resetSimulation();
+		const result = await importFromUrl(url, {
+			deferToolboxInstall: true,
+			backendReady: backendReady ?? Promise.resolve()
+		});
+		if (result.success) {
+			try {
+				history.replaceState(history.state, '', `?model=${encodeURIComponent(url)}`);
+			} catch {
+				/* replaceState can throw in odd embedding contexts; non-fatal */
+			}
+			setTimeout(() => triggerFitView(), 100);
+		} else if (result.error) {
+			consoleStore.error(`Failed to load example: ${url}`);
+			consoleStore.error(result.error);
+			showConsole = true;
+		}
+	}
+
 	// Track placement offset for stacking prevention
 	let placementOffset = 0;
 	let lastPlacementTime = 0;
@@ -1851,6 +1882,7 @@
 		<WelcomeModal
 			onNew={handleNew}
 			onClose={() => showWelcomeModal = false}
+			onLoadExample={loadExample}
 		/>
 	{/if}
 </div>