fix(tui): retain current model and agent across session switches

packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx

@@ -241,26 +241,32 @@ export function Prompt(props: PromptProps) {
     ),
   )
 
-  // Initialize agent/model/variant from last user message when session changes
+  // Initialize agent/model/variant from the session's last user message on the
+  // first session that loads. On subsequent session switches, preserve the
+  // user's current agent/model selection rather than reverting to the session's
+  // historical configuration.
   let syncedSessionID: string | undefined
+  let initialized = false
   createEffect(() => {
     const sessionID = props.sessionID
     const msg = lastUserMessage()
 
-    if (sessionID !== syncedSessionID) {
-      if (!sessionID || !msg) return
+    if (sessionID === syncedSessionID) return
+    if (!sessionID || !msg) return
 
-      syncedSessionID = sessionID
+    syncedSessionID = sessionID
 
-      // Only set agent if it's a primary agent (not a subagent)
-      const isPrimaryAgent = local.agent.list().some((x) => x.name === msg.agent)
-      if (msg.agent && isPrimaryAgent) {
-        // Keep command line --agent if specified.
-        if (!args.agent) local.agent.set(msg.agent)
-        if (msg.model) {
-          local.model.set(msg.model)
-          local.model.variant.set(msg.model.variant)
-        }
+    if (initialized) return
+    initialized = true
+
+    // Only set agent if it's a primary agent (not a subagent)
+    const isPrimaryAgent = local.agent.list().some((x) => x.name === msg.agent)
+    if (msg.agent && isPrimaryAgent) {
+      // Keep command line --agent if specified.
+      if (!args.agent) local.agent.set(msg.agent)
+      if (msg.model) {
+        local.model.set(msg.model)
+        local.model.variant.set(msg.model.variant)
       }
     }
   })