Retain working file name and handle across sessions

src/lib/schema/fileOps.ts

@@ -34,6 +34,7 @@ import { nodeRegistry } from '$lib/nodes';
 import { NODE_TYPES } from '$lib/constants/nodeTypes';
 import {
 	AUTOSAVE_KEY,
+	LAST_FILE_KEY,
 	kvDelete,
 	kvGet,
 	kvHas,
@@ -85,6 +86,40 @@ export function getCurrentFileName(): string | null {
 export function clearCurrentFile(): void {
 	currentFileHandle = null;
 	currentFileNameStore.set(null);
+	void kvDelete(LAST_FILE_KEY);
+}
+
+/**
+ * Persist the current file reference (name + handle, when one exists) so a
+ * restored session keeps saving to the file the user was working on. Handles
+ * are structured-cloneable, so IDB stores them as-is (same mechanism as the
+ * recents list); writing resumes after the browser's permission re-prompt.
+ */
+function persistFileRef(): void {
+	const name = getCurrentFileName();
+	if (!name && !currentFileHandle) return;
+	void kvSet(LAST_FILE_KEY, {
+		name,
+		handle: currentFileHandle ?? undefined
+	}).catch(() => {});
+}
+
+/**
+ * Restore the persisted file reference after an autosave snapshot was loaded.
+ * `fallbackName` (e.g. the snapshot's metadata name) applies when no
+ * reference was persisted. No-op when nothing is known.
+ */
+export async function restoreFileRef(fallbackName?: string): Promise<void> {
+	try {
+		const ref = await kvGet<{ name: string | null; handle?: FileSystemFileHandle }>(LAST_FILE_KEY);
+		const name = ref?.name || fallbackName;
+		if (ref?.handle && hasFileSystemAccess()) {
+			currentFileHandle = ref.handle;
+		}
+		if (name) currentFileNameStore.set(name);
+	} catch {
+		if (fallbackName) currentFileNameStore.set(fallbackName);
+	}
 }
 
 /**
@@ -355,7 +390,9 @@ export async function installToolboxesForCurrentGraph(): Promise<void> {
  */
 export async function autoSave(): Promise<void> {
 	try {
-		const file = createGraphFile('Autosave');
+		// Keep the working file's name in the snapshot so a restored session
+		// suggests it again ('Autosave' only for never-saved graphs).
+		const file = createGraphFile(getCurrentFileName() || 'Autosave');
 		await kvSet(AUTOSAVE_KEY, file);
 	} catch (error) {
 		console.warn('Autosave failed:', error);
@@ -412,6 +449,7 @@ export async function loadAutoSave(): Promise<boolean> {
 		}
 
 		await loadGraphFile(file);
+		await restoreFileRef(file.metadata?.name !== 'Autosave' ? file.metadata?.name : undefined);
 		return true;
 	} catch (error) {
 		console.warn('Failed to restore autosave, clearing:', error);
@@ -488,6 +526,7 @@ export async function saveAsFile(): Promise<boolean> {
 			// Update current file reference
 			currentFileHandle = handle;
 			currentFileNameStore.set(name);
+			persistFileRef();
 			void rememberRecent(handle);
 			return true;
 		} catch (error: any) {
@@ -514,6 +553,7 @@ function downloadGraphFile(filename: string): void {
 
 	// Set current file name for subsequent saves
 	currentFileNameStore.set(name);
+	persistFileRef();
 }
 
 /**
@@ -748,6 +788,7 @@ async function importModel(
 		componentFile.metadata.name ||
 		null
 	);
+	persistFileRef();
 	if (currentFileHandle) void rememberRecent(currentFileHandle);
 
 	return { success: true, type: 'model' };

src/lib/schema/handleStore.ts

@@ -17,6 +17,9 @@ const RECENTS_STORE = 'recents';
 const RECENTS_LIMIT = 10;
 
 export const AUTOSAVE_KEY = 'autosave';
+// Name + handle of the file the user is working on, persisted next to the
+// autosave blob so a restored session keeps saving to the same file.
+export const LAST_FILE_KEY = 'lastFile';
 
 export interface RecentFile {
 	id: string;

src/routes/+page.svelte

@@ -12,7 +12,7 @@
 	import { themeStore, type Theme } from '$lib/stores/theme';
 	import { toggleThemeWithTransition } from '$lib/utils/themeTransition';
 	import { AUTOSAVE_KEY, kvGet, hasFileSystemAccess, type RecentFile } from '$lib/schema/handleStore';
-	import { loadGraphFile, listRecentFiles, openRecentFile, removeRecentFile } from '$lib/schema/fileOps';
+	import { loadGraphFile, restoreFileRef, listRecentFiles, openRecentFile, removeRecentFile } from '$lib/schema/fileOps';
 	import type { GraphFile } from '$lib/nodes/types';
 	import { triggerFitView } from '$lib/stores/viewActions';
 	import { consoleStore } from '$lib/stores/console';
@@ -105,6 +105,11 @@
 					// Python backend) deferred; missing blocks render as
 					// placeholders in the preview and upgrade in the editor.
 					await loadGraphFile(snapshot, { deferToolboxInstall: true, backendReady: new Promise(() => {}) });
+					// Re-attach the session's file reference (name + handle):
+					// clicking through to the editor skips the restore prompt
+					// (graph already populated), so this is where Save gets its
+					// target back.
+					await restoreFileRef(snapshot.metadata?.name !== 'Autosave' ? snapshot.metadata?.name : undefined);
 					preview = 'session';
 				} else {
 					const res = await fetch(`${base}/examples/${DEFAULT_EXAMPLE.filename}`);

src/routes/editor/+page.svelte

@@ -48,7 +48,7 @@
 	import { resolveBackend } from '$lib/pyodide/backend';
 	import { runGraphStreamingSimulation, validateGraphSimulation, exportToPython } from '$lib/pyodide/pathsimRunner';
 	import { consoleStore } from '$lib/stores/console';
-	import { newGraph, saveFile, saveAsFile, setupAutoSave, clearAutoSave, debouncedAutoSave, openImportDialog, importFromUrl, currentFileName, loadGraphFile, listRecentFiles, openRecentFile, removeRecentFile, installToolboxesForCurrentGraph } from '$lib/schema/fileOps';
+	import { newGraph, saveFile, saveAsFile, setupAutoSave, clearAutoSave, debouncedAutoSave, openImportDialog, importFromUrl, currentFileName, loadGraphFile, restoreFileRef, listRecentFiles, openRecentFile, removeRecentFile, installToolboxesForCurrentGraph } from '$lib/schema/fileOps';
 	import { AUTOSAVE_KEY, kvGet, hasFileSystemAccess, type RecentFile } from '$lib/schema/handleStore';
 	import type { GraphFile } from '$lib/nodes/types';
 	import { confirmationStore } from '$lib/stores/confirmation';
@@ -730,6 +730,9 @@
 			if (ok) {
 				try {
 					await loadGraphFile(snapshot);
+					// Re-attach the file the session was working on (name +
+					// handle), so Save targets it again instead of a default.
+					await restoreFileRef(snapshot.metadata?.name !== 'Autosave' ? snapshot.metadata?.name : undefined);
 					setTimeout(() => triggerFitView(), 100);
 				} catch (e) {
 					console.warn('Failed to restore autosave:', e);