fix: taking the diff drawer without a token claims it, and the classic app editor takes one

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/DiffDrawer.svelte

@@ -68,7 +68,13 @@
 		  }
 		| undefined = $state(undefined)
 
-	export function openDrawer() {
+	export function openDrawer(token?: number) {
+		// No token means the caller is taking the drawer for itself, so claim one here:
+		// every reuse (a deploy-override's "Show diff", a draft badge, a workspace
+		// comparison) then invalidates an editor opening that is still fetching, instead
+		// of being replaced by it when it lands.
+		if (token != null && token !== openingToken) return
+		if (token == null) openingToken++
 		data = undefined
 		diffType = undefined
 		diffViewer?.openDrawer()
@@ -80,9 +86,9 @@
 
 	/** Counted per opening, and counted here rather than in the editor that opens one: a
 	 *  path change remounts the editor while this drawer stays mounted, so a counter local
-	 *  to the editor is one an outlived request still matches — it would open and fill the
-	 *  drawer with the item the user just left. Every write an opening makes (the blanking
-	 *  `openDrawer` included) checks `ownsOpening` first. */
+	 *  to the editor is one an outlived request still matches, and it would open and fill
+	 *  the drawer with the item the user just left. Every write an opening makes (the
+	 *  blanking `openDrawer` included) checks `ownsOpening` first. */
 	let openingToken = 0
 
 	export function beginOpening(): number {

frontend/src/lib/components/FlowBuilder.svelte

@@ -1181,7 +1181,7 @@
 		const currentDraftTriggers = structuredClone(triggersState.getDraftTriggersSnapshot())
 		// Blanking the drawer belongs to the opening that will fill it.
 		if (!diffDrawer?.ownsOpening(opening)) return
-		diffDrawer.openDrawer()
+		diffDrawer.openDrawer(opening)
 		const currentFlow = flowStore.val
 		const versions = await deployedVersionOptions()
 		if (!diffDrawer?.ownsOpening(opening)) return

frontend/src/lib/components/ScriptBuilder.svelte

@@ -905,7 +905,7 @@
 
 		// Blanking the drawer belongs to the opening that will fill it.
 		if (!diffDrawer?.ownsOpening(opening)) return
-		diffDrawer.openDrawer()
+		diffDrawer.openDrawer(opening)
 		const headHash = (deployed as { hash?: string } | undefined)?.hash
 		const versions = await deployedVersionOptions(headHash)
 		if (!diffDrawer?.ownsOpening(opening)) return

frontend/src/lib/components/apps/editor/AppEditorHeader.svelte

@@ -32,7 +32,7 @@
 		Zap,
 		Globe
 	} from 'lucide-svelte'
-	import { getContext, untrack } from 'svelte'
+	import { getContext, onDestroy, untrack } from 'svelte'
 	import { orderedJsonStringify, type Value, replaceFalseWithUndefined } from '../../../utils'
 	import type { App, AppEditorContext, AppViewerContext } from '../types'
 	import { toStatic } from '../utils'
@@ -329,13 +329,20 @@
 		}
 	}
 
-	async function syncWithDeployed() {
+	// An opening outlives this editor when a path change remounts it mid-fetch; without
+	// this it would still open the drawer on the app the user left.
+	onDestroy(() => diffDrawer?.abandonOpening())
+
+	async function syncWithDeployed(opening?: number) {
 		const deployedApp = await AppService.getAppByPath({
 			workspace: $workspaceStore!,
 			path: $appPath!,
 			withStarredInfo: true
 		})
 
+		// A superseded opening must not write these: the current one would then render
+		// against the older deployed value.
+		if (opening != null && !diffDrawer?.ownsOpening(opening)) return
 		deployedBy = deployedApp.created_by
 
 		// Strip off extra information
@@ -624,12 +631,18 @@
 				if (!savedApp || newApp) {
 					return
 				}
+				// The fetch below is awaited, so a reopen (or a path change, which remounts
+				// this editor but not the drawer) while it runs must not have the older one
+				// land last. The drawer counts the openings for that reason.
+				const opening = diffDrawer?.beginOpening()
+				if (opening == null) return
 
 				// deployedValue should be syncronized when we open Diff
-				await syncWithDeployed()
+				await syncWithDeployed(opening)
 
-				diffDrawer?.openDrawer()
-				diffDrawer?.setDiff({
+				if (!diffDrawer?.ownsOpening(opening)) return
+				diffDrawer.openDrawer(opening)
+				diffDrawer.setDiff({
 					mode: 'normal',
 					deployed: deployedValue ?? savedApp,
 					current: {
@@ -759,12 +772,16 @@
 						if (!savedApp || newApp) {
 							return
 						}
+						// The other entry point into the same drawer, so it takes an opening too.
+						const opening = diffDrawer?.beginOpening()
+						if (opening == null) return
 						// deployedValue should be syncronized when we open Diff
-						await syncWithDeployed()
+						await syncWithDeployed(opening)
 
+						if (!diffDrawer?.ownsOpening(opening)) return
 						saveDrawerOpen = false
-						diffDrawer?.openDrawer()
-						diffDrawer?.setDiff({
+						diffDrawer.openDrawer(opening)
+						diffDrawer.setDiff({
 							mode: 'normal',
 							deployed: deployedValue ?? savedApp,
 							current: {

frontend/src/lib/components/diff_drawer.ts

@@ -53,7 +53,10 @@ export type DiffDrawerDiff =
 	  }
 
 export interface DiffDrawerI {
-	openDrawer: () => void
+	/** Pass the token from `beginOpening` to continue that opening; called without one,
+	 *  the drawer claims a fresh opening, so any reuse invalidates a fetch still in
+	 *  flight rather than being overwritten by it. */
+	openDrawer: (token?: number) => void
 	closeDrawer: () => void
 	setDiff: (diff: DiffDrawerDiff) => void
 	/** Claim the drawer for one opening. Filling it takes awaited fetches, and a path

frontend/src/lib/components/raw_apps/RawAppEditorHeader.svelte

@@ -472,7 +472,7 @@
 
 		// Blanking the drawer belongs to the opening that will fill it.
 		if (!diffDrawer?.ownsOpening(opening)) return
-		diffDrawer.openDrawer()
+		diffDrawer.openDrawer(opening)
 		const versions = await deployedVersionOptions()
 		if (!diffDrawer?.ownsOpening(opening)) return
 		diffDrawer.setDiff({
@@ -704,7 +704,7 @@
 
 						if (!diffDrawer?.ownsOpening(opening)) return
 						saveDrawerOpen = false
-						diffDrawer.openDrawer()
+						diffDrawer.openDrawer(opening)
 						diffDrawer.setDiff({
 							mode: 'normal',
 							deployed: deployedValue ?? stripRawAppDiffNoise(savedApp),