fix: persist model on conversation send, fallback resolution, carry model on new conversation

Cargo.lock

@@ -5544,6 +5544,7 @@ dependencies = [
  "dirs 5.0.1",
  "futures",
  "reqwest 0.12.28",
+ "rusqlite",
  "serde",
  "serde_json",
  "tauri",

apps/desktop/Cargo.toml

@@ -29,6 +29,7 @@ reqwest.workspace = true
 futures.workspace = true
 uuid.workspace = true
 dirs.workspace = true
+rusqlite.workspace = true
 xianren-core = { path = "../../crates/core" }
 xianren-engine = { path = "../../crates/engine" }
 xianren-download = { path = "../../crates/download" }

apps/desktop/src/commands.rs

@@ -217,10 +217,12 @@ pub fn list_conversations(state: State<'_, App>) -> Result<Vec<xianren_core::Con
 pub fn create_conversation(
     state: State<'_, App>,
     title: String,
+    model_id: Option<String>,
 ) -> Result<xianren_core::Conversation, String> {
     let id = uuid::Uuid::new_v4().to_string();
     let db = state.core.db.lock().unwrap();
-    sessions_db::create_conversation(&db, &id, &title, None, None).map_err(|e| e.to_string())?;
+    sessions_db::create_conversation(&db, &id, &title, model_id.as_deref(), None)
+        .map_err(|e| e.to_string())?;
     sessions_db::get_conversation(&db, &id)
         .map_err(|e| e.to_string())?
         .ok_or_else(|| "conversation not found".to_string())
@@ -481,6 +483,9 @@ pub async fn chat_send(
             )
             .map_err(|e| e.to_string())?;
         }
+        // 始终把当前使用的模型写回会话，编辑/重新生成依赖它
+        sessions_db::update_conversation_model(&db, &payload.conversation_id, &payload.model_id)
+            .map_err(|e| e.to_string())?;
         let user_message_id = sessions_db::add_message(
             &db,
             &payload.conversation_id,
@@ -724,6 +729,21 @@ fn estimate_tokens(text: &str) -> usize {
     score / 4 + 1
 }
 
+/// 解析会话使用的模型：优先会话记录；未记录时若本地只有一个模型则自动使用，否则提示。
+fn resolve_conversation_model(
+    db: &rusqlite::Connection,
+    conversation: &xianren_core::Conversation,
+) -> Result<String, String> {
+    if let Some(id) = &conversation.model_id {
+        return Ok(id.clone());
+    }
+    let all = models_db::list(db).map_err(|e| e.to_string())?;
+    if all.len() == 1 {
+        return Ok(all[0].id.clone());
+    }
+    Err("会话未记录模型：请先在该会话发送一条消息，或重新选择模型后重试".into())
+}
+
 /// 重新生成某条助手回复：旧内容存入版本历史，截断后重新生成。
 #[tauri::command]
 pub async fn regenerate_message(
@@ -768,10 +788,7 @@ pub async fn regenerate_message(
                 images: m.images.clone(),
             })
             .collect::<Vec<_>>();
-        let model_id = conversation
+        let model_id = resolve_conversation_model(&db, &conversation)?;
-            .model_id
-            .clone()
-            .ok_or_else(|| "conversation has no model".to_string())?;
         let model = models_db::get(&db, &model_id)
             .map_err(|e| e.to_string())?
             .ok_or_else(|| "model not found".to_string())?;
@@ -835,10 +852,7 @@ pub async fn edit_message(
                 images: m.images,
             })
             .collect::<Vec<_>>();
-        let model_id = conversation
+        let model_id = resolve_conversation_model(&db, &conversation)?;
-            .model_id
-            .clone()
-            .ok_or_else(|| "conversation has no model".to_string())?;
         let model = models_db::get(&db, &model_id)
             .map_err(|e| e.to_string())?
             .ok_or_else(|| "model not found".to_string())?;

crates/core/src/sessions.rs

@@ -85,6 +85,14 @@ pub fn touch_conversation(db: &Connection, id: &str) -> Result<()> {
     Ok(())
 }
 
+pub fn update_conversation_model(db: &Connection, id: &str, model_id: &str) -> Result<()> {
+    db.execute(
+        "UPDATE conversations SET model_id = ?1 WHERE id = ?2",
+        params![model_id, id],
+    )?;
+    Ok(())
+}
+
 pub fn delete_conversation(db: &Connection, id: &str) -> Result<()> {
     db.execute("DELETE FROM conversations WHERE id = ?1", params![id])?;
     Ok(())

ui/src/api.ts

@@ -194,8 +194,8 @@ export const api = {
   settingsSet: (key: string, value: string) =>
     invoke<void>("settings_set", { key, value }),
   listConversations: () => invoke<Conversation[]>("list_conversations"),
-  createConversation: (title: string) =>
+  createConversation: (title: string, modelId?: string) =>
-    invoke<Conversation>("create_conversation", { title }),
+    invoke<Conversation>("create_conversation", { title, modelId: modelId ?? null }),
   deleteConversation: (id: string) =>
     invoke<void>("delete_conversation", { id }),
   getMessages: (conversationId: string) =>

ui/src/pages/ChatPage.tsx

@@ -331,7 +331,7 @@ export default function ChatPage() {
   }
 
   async function handleNewConversation() {
-    const conv = await api.createConversation("新会话");
+    const conv = await api.createConversation("新会话", selectedModelId || undefined);
     setActiveConvId(conv.id);
     setMessages([]);
     setError(null);