fix(teacher): 区分词元预算与传输字节避免短问题被拦截

electron/coding-teacher/model-runner.ts

@@ -11,7 +11,7 @@ import {
   TeacherError,
   type TeacherAccount,
 } from './config-client';
-import { estimateTeacherTokens, type TeacherModelMessage, type TeacherToolCall } from './context';
+import { estimateTeacherTextTokens, estimateTeacherTokens, TEACHER_ESTIMATED_BYTES_PER_TOKEN, type TeacherModelMessage, type TeacherToolCall } from './context';
 import { createTeacherReadTools, type TeacherReadAccess, type TeacherReadTools } from './read-tools';
 
 interface TeacherModelConfig {
@@ -74,8 +74,9 @@ export async function prepareTeacherModel(
     capability.limits?.contextWindow ? capability.limits.contextWindow - outputLimit : Infinity
   );
   const tools = access ? createTeacherReadTools(access) : undefined;
-  const toolBudget = tools ? Buffer.byteLength(JSON.stringify(tools.definitions), 'utf8') + 64 : 0;
+  const toolBudget = tools ? estimateTeacherTextTokens(JSON.stringify(tools.definitions)) + 64 : 0;
   return {
+    measureInput: estimateTeacherTokens,
     // Leave room for a read result and its native tool-call envelope.
     inputLimit: inputLimit - toolBudget - (tools ? Math.min(2400, Math.floor(inputLimit / 4)) : 0),
     run: (messages: TeacherModelMessage[], signal: AbortSignal, onText: (text: string) => void) => {
@@ -97,7 +98,7 @@ export async function streamTeacherReply(
   options?: { tools?: TeacherReadTools; inputLimit: number; finalOnly?: boolean; assertCurrent(): void }
 ): Promise<PublicUsage | undefined> {
   const tools = options?.tools;
-  const toolBudget = tools ? Buffer.byteLength(JSON.stringify(tools.definitions), 'utf8') + 64 : 0;
+  const toolBudget = tools ? estimateTeacherTextTokens(JSON.stringify(tools.definitions)) + 64 : 0;
   const reads: TeacherModelMessage[][] = [];
   let usage: PublicUsage | undefined;
   // Six read rounds, then one final text response. No recursive agent or Pi session.
@@ -129,8 +130,11 @@ export async function streamTeacherReply(
     }
     const batch: TeacherModelMessage[] = [{ role: 'assistant', content: result.text, tool_calls: result.calls,
       ...(result.reasoning ? { reasoning_content: result.reasoning } : {}) }];
+    // Tools bound their UTF-8 result bytes; convert the remaining token estimate
+    // back to bytes while keeping the existing per-result byte cap.
     const resultBudget = Math.min(2400, Math.floor(((options?.inputLimit ?? Infinity)
-      - toolBudget - estimateTeacherTokens([...messages, ...batch]) - 64 * result.calls.length) / result.calls.length));
+      - toolBudget - estimateTeacherTokens([...messages, ...batch]) - 64 * result.calls.length)
+      * TEACHER_ESTIMATED_BYTES_PER_TOKEN / result.calls.length));
     if (resultBudget < 128) {
       throw new TeacherError(422, 'teacher_context_too_long', '老师读取的内容超过上下文预算，请缩小问题范围或联系运营增加预算。');
     }