refactor: unify tool reason requirements

src/routes/chatStreamEvents.ts

@@ -119,9 +119,11 @@ export const normalizeToolParams = (value: unknown): Record<string, unknown> =>
   return {};
 };
 
+// New tools use reason; aliases are read-only compatibility for existing events.
+const reasonKeys = ["reason", "request_reason", "why", "purpose", "rationale"];
+
 export const extractRequestReason = (params: Record<string, unknown>) => {
-  const candidates = ["reason", "request_reason", "why", "purpose", "rationale"];
-  for (const key of candidates) {
+  for (const key of reasonKeys) {
     const value = params[key];
     if (typeof value === "string") {
       const normalized = value.trim();
@@ -381,7 +383,7 @@ const truncateProgressText = (text: string, maxLength: number) =>
   text.length > maxLength ? `${text.slice(0, maxLength - 3)}...` : text;
 
 const summarizeToolParams = (params: Record<string, unknown>) => {
-  const ignoredKeys = new Set(["reason", "request_reason", "why", "purpose", "rationale"]);
+  const ignoredKeys = new Set(reasonKeys);
   const summary = Object.entries(params)
     .filter(([key]) => !ignoredKeys.has(key))
     .slice(0, 4)
@@ -433,7 +435,7 @@ export const buildToolProgressDetail = (
   error?: string,
 ) => {
   const toolName = toolLabels[tool] ?? tool;
-  const reasonText = reason ? `；调用原因：${reason}` : "";
+  const reasonText = reason ? `；说明：${reason}` : "";
   const paramsText = `；关键参数：${summarizeToolParams(params)}`;
 
   if (status === "error") {