fix: complete session persistence overhaul (Codex 5.2)

1. Implemented auto-selection of tasks in MultiXV2 to prevent empty initial state.
2. Added force-loading logic for task session messages with debouncing.
3. Updated session-actions to return full assistant text and immediately persist native messages.
4. Fixed caching logic in instance-shell2 to retain active task sessions in memory.

packages/server/src/server/routes/native-sessions.ts

@@ -209,6 +209,51 @@ export function registerNativeSessionsRoutes(app: FastifyInstance, deps: NativeS
         }
     })
 
+    // Append messages to a session (client-side persistence)
+    app.post<{
+        Params: { workspaceId: string; sessionId: string }
+        Body: {
+            messages: Array<{
+                id?: string
+                role: "user" | "assistant" | "system" | "tool"
+                content?: string
+                createdAt?: number
+                updatedAt?: number
+                status?: "pending" | "streaming" | "completed" | "error"
+            }>
+        }
+    }>("/api/native/workspaces/:workspaceId/sessions/:sessionId/messages", async (request, reply) => {
+        const { workspaceId, sessionId } = request.params
+        const payload = request.body?.messages
+        if (!Array.isArray(payload)) {
+            reply.code(400)
+            return { error: "messages array is required" }
+        }
+
+        try {
+            const results: SessionMessage[] = []
+            for (const entry of payload) {
+                if (!entry || typeof entry.role !== "string") {
+                    continue
+                }
+                const saved = await sessionManager.addMessage(workspaceId, sessionId, {
+                    id: entry.id,
+                    role: entry.role,
+                    content: entry.content,
+                    createdAt: entry.createdAt,
+                    updatedAt: entry.updatedAt,
+                    status: entry.status,
+                })
+                results.push(saved)
+            }
+            return { messages: results }
+        } catch (error) {
+            logger.error({ error }, "Failed to append messages")
+            reply.code(500)
+            return { error: "Failed to append messages" }
+        }
+    })
+
     // Add a message (user prompt) and get streaming response
     app.post<{
         Params: { workspaceId: string; sessionId: string }

packages/server/src/storage/session-store.ts

@@ -27,6 +27,12 @@ export interface SessionMessage {
     status?: "pending" | "streaming" | "completed" | "error"
 }
 
+type IncomingSessionMessage = Omit<SessionMessage, "id" | "sessionId" | "createdAt" | "updatedAt"> & {
+    id?: string
+    createdAt?: number
+    updatedAt?: number
+}
+
 export interface MessagePart {
     type: "text" | "tool_call" | "tool_result" | "thinking" | "code"
     content?: string
@@ -260,23 +266,29 @@ export class NativeSessionManager {
             .filter((msg): msg is SessionMessage => msg !== undefined)
     }
 
-    async addMessage(workspaceId: string, sessionId: string, message: Omit<SessionMessage, "id" | "sessionId" | "createdAt" | "updatedAt">): Promise<SessionMessage> {
+    async addMessage(workspaceId: string, sessionId: string, message: IncomingSessionMessage): Promise<SessionMessage> {
         const store = await this.loadStore(workspaceId)
         const session = store.sessions[sessionId]
         if (!session) throw new Error(`Session not found: ${sessionId}`)
 
         const now = Date.now()
+        const messageId = message.id ?? ulid()
+        const createdAt = typeof message.createdAt === "number" ? message.createdAt : now
+        const updatedAt = typeof message.updatedAt === "number" ? message.updatedAt : createdAt
+
         const newMessage: SessionMessage = {
             ...message,
-            id: ulid(),
+            id: messageId,
             sessionId,
-            createdAt: now,
-            updatedAt: now,
+            createdAt,
+            updatedAt,
         }
 
         store.messages[newMessage.id] = newMessage
-        session.messageIds.push(newMessage.id)
-        session.updatedAt = now
+        if (!session.messageIds.includes(newMessage.id)) {
+            session.messageIds.push(newMessage.id)
+        }
+        session.updatedAt = updatedAt
 
         await this.saveStore(workspaceId)
         return newMessage