fix(coding): recover provider context failures

electron/coding-runtime/conversation-service.ts

@@ -443,13 +443,13 @@ export class CodingConversationService {
     try {
       selected = await this.runtime.validateModel(model);
     } catch (error) { runtimeError(error); }
-    await this.ensurePrepared(conversationId);
-    let snapshot: ConversationSnapshot;
-    try {
-      snapshot = await this.runtime.getSnapshot(conversationId);
-    } catch (error) { runtimeError(error); }
-    this.assertSnapshotAllowsMutation(snapshot);
     if (conversation.modelResolution === 'resolved' && conversation.model) {
+      await this.ensurePrepared(conversationId);
+      let snapshot: ConversationSnapshot;
+      try {
+        snapshot = await this.runtime.getSnapshot(conversationId);
+      } catch (error) { runtimeError(error); }
+      this.assertSnapshotAllowsMutation(snapshot);
       let state: ConversationModelState;
       try {
         state = await this.runtime.setModel({

electron/coding-runtime/pi/event-projector.ts

@@ -6,6 +6,7 @@ import type {
   ConversationToolNode,
   PublicUsage,
 } from '../contracts';
+import { isAIGatewayUserContextMissing } from '../../../shared/ai-gateway-error-details';
 import type { PiRpcEvent } from './rpc-client';
 import { subagentDetailsOfResult } from '../subagent-protocol';
 import {
@@ -44,6 +45,17 @@ function retryFailure(message: string) {
   };
 }
 
+function providerFailure(message: unknown) {
+  if (typeof message === 'string' && isAIGatewayUserContextMissing(message)) {
+    return {
+      code: 'CODING_PROVIDER_AUTH_REQUIRED' as const,
+      message: '模型服务身份上下文无效，请重试；若仍失败请重新登录。',
+      recoverable: true,
+    };
+  }
+  return retryFailure('模型服务请求失败，请稍后重试。');
+}
+
 function asRecord(value: unknown): Record<string, unknown> | null {
   return value !== null && typeof value === 'object' && !Array.isArray(value)
     ? value as Record<string, unknown>
@@ -282,7 +294,7 @@ export class PiEventProjector {
           ...run,
           status: 'error',
           terminalReason: 'failed',
-          error: retryFailure('The local Agent retry failed'),
+          error: providerFailure(event.finalError),
         },
       }];
     }
@@ -459,6 +471,25 @@ export class PiEventProjector {
       ];
     }
 
+    if (event.type === 'agent_end' && event.willRetry === false && Array.isArray(event.messages)) {
+      const assistant = [...event.messages]
+        .reverse()
+        .map(asRecord)
+        .find((message) => message?.role === 'assistant');
+      if (assistant?.stopReason === 'error') {
+        return [{
+          op: 'run.state',
+          run: {
+            ...snapshot.run,
+            status: 'error',
+            terminalReason: 'failed',
+            error: providerFailure(assistant.errorMessage),
+          },
+        }];
+      }
+      return [];
+    }
+
     if (event.type === 'extension_ui_request'
       && typeof event.id === 'string'
       && typeof event.method === 'string'