fix: keep unsent input, init and chat rotation safe from runtime eviction

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

frontend/src/lib/components/copilot/chat/AIChatInput.svelte

@@ -378,6 +378,7 @@
 	)
 	$effect(() => {
 		chatHost.setComposerStaged(composerKey, editingMessageIndex, stagedBytes)
+		chatHost.setComposerHasDraft(composerKey, !draft.isEmpty || pendingFileBytes > 0)
 	})
 	$effect(() => () => chatHost.clearComposerStaged(composerKey))
 

frontend/src/lib/components/copilot/chat/AIChatManager.svelte.ts

@@ -2822,6 +2822,27 @@ export class AIChatManager implements ChatViewHost {
 
 	clearComposerStaged(key: string) {
 		this.#composerStaged.delete(key)
+		this.#composersWithDraft.delete(key)
+	}
+
+	// Composers whose draft is non-empty. The draft itself is component-local, so
+	// this is the only way to know an unmount would lose unsent input.
+	#composersWithDraft = new SvelteSet<string>()
+
+	setComposerHasDraft(key: string, hasDraft: boolean) {
+		if (hasDraft) this.#composersWithDraft.add(key)
+		else this.#composersWithDraft.delete(key)
+	}
+
+	/** Unsent input an unmount of this chat would lose: a composer draft, or a
+	 *  queued message (whose text may be empty when it carries only attachments
+	 *  or context). */
+	get hasUnsentInput(): boolean {
+		return (
+			this.#composersWithDraft.size > 0 ||
+			!this.#queuedDraft.isEmpty ||
+			this.queuedContext !== undefined
+		)
 	}
 
 	/** Release the outgoing-files reservation identified by `key` (a per-send token).

frontend/src/lib/components/copilot/chat/chatViewHost.ts

@@ -85,6 +85,8 @@ export interface ChatViewHost {
 	) => void
 	dequeueMessage: () => void
 	setComposerStaged: (key: string, editingIndex: number | null, bytes: number) => void
+	/** Whether this composer holds anything unsent (text, pastes, attachments, reads in flight). */
+	setComposerHasDraft: (key: string, hasDraft: boolean) => void
 	clearComposerStaged: (key: string) => void
 	attachmentBytesExcluding: (selfKey: string) => number
 

frontend/src/lib/components/flows/conversations/flowChatViewHost.svelte.ts

@@ -470,6 +470,7 @@ export class FlowChatViewHost implements ChatViewHost {
 		return taken
 	}
 	setComposerStaged = () => {}
+	setComposerHasDraft = () => {}
 	clearComposerStaged = () => {}
 	attachmentBytesExcluding = () => 0
 

frontend/src/lib/components/sessions/sessionRuntime.svelte.ts

@@ -228,6 +228,8 @@ export interface SessionRuntime {
 }
 
 const runtimes = new SvelteMap<string, SessionRuntime>()
+// Sessions whose runtime is still restoring its chat (initRuntime pending).
+const initializing = new Set<string>()
 
 function emptyFlow(): Flow {
 	return {
@@ -990,7 +992,10 @@ export function getOrCreateRuntime(session: Session): SessionRuntime {
 	if (!runtime) {
 		runtime = createRuntime(session)
 		runtimes.set(session.id, runtime)
-		initRuntime(runtime, session).catch((e) => console.error('Failed to init session runtime', e))
+		initializing.add(session.id)
+		initRuntime(runtime, session)
+			.catch((e) => console.error('Failed to init session runtime', e))
+			.finally(() => initializing.delete(session.id))
 	}
 	return runtime
 }
@@ -1040,6 +1045,9 @@ onRemoteTurnEnd((sessionId, chatId) => {
 async function applyRemoteTurnEnd(sessionId: string, chatId: string): Promise<void> {
 	const runtime = runtimes.get(sessionId)
 	if (!runtime) {
+		// The driving tab may have rotated to a new chat; follow it, or the next
+		// read and a later runtime would open the old one.
+		setSessionChatId(sessionId, chatId)
 		peeks.delete(sessionId)
 		return
 	}
@@ -1455,10 +1463,13 @@ const visitOrder: string[] = []
 function isEvictable(runtime: SessionRuntime): boolean {
 	const m = runtime.manager
 	return (
+		// initRuntime has no cancellation: evicted mid-way, it would go on to restore
+		// the chat's jobs into a manager nothing owns, which then polls them.
+		!initializing.has(runtime.sessionId) &&
 		!m.loading &&
 		!m.sendInFlight &&
 		m.instructions.trim() === '' &&
-		m.queuedMessage.trim() === '' &&
+		!m.hasUnsentInput &&
 		!m.backgroundJobs.some(isLiveJob) &&
 		!runtime.hasEditorCells()
 	)