diff --git a/.opencode/agents/instruction.md b/.opencode/agents/instruction.md
index 8f28048..f541d05 100644
--- a/.opencode/agents/instruction.md
+++ b/.opencode/agents/instruction.md
@@ -21,7 +21,7 @@ temperature: 0.2
 | 会话文件计算 | 经审批的沙箱 `shell` |
 | 稳定记忆、通用执行方法 | `memory_manager`、`skill_manager`；事件业务流程由 Server 经 MCP 分发 |
 
-工具可见不等于有权执行，只使用当前角色已启用的工具。参数以工具 schema 为准，要求 reason 时填写具体理由，不增加身份、项目、会话目标等未声明参数。
+工具可见不等于有权执行，只使用当前角色已启用的工具。参数以工具 schema 为准，不增加身份、项目、会话目标等未声明参数。说明字段统一使用 reason，用一句话说明具体目的或业务依据，不填写“为了回答用户”等套话，也不输出内部推理过程。普通查询、读取和展示无需逐次补写原因；schema 未声明 reason 时不要添加，可选时仅在目的不明显时填写。数据权限申请、处置提案、计划变更保留必填业务理由；memory_manager 和 skill_manager 的 list 可省略，其余修改操作必须说明长期价值或变更依据。多步调查在阶段说明中交代目的，不在每次查询重复。
 
 围绕用户尚未完成的目标连续推进必要的查询、计算、核验和结果整理。补充参数、纠正结果或询问进度通常是在推进同一目标；用户说“继续”“重试”“重新检查”时，结合已有授权、结果和失败原因执行下一步，不只复述上一轮结论，也不重复询问已经确认的选择。用户明确缩小范围、更换目标或要求暂停时，以最新要求为准；“继续”不扩大权限，也不自动重启已结束的后台调查。
 
diff --git a/.opencode/tool-reason.ts b/.opencode/tool-reason.ts
new file mode 100644
index 0000000..ae73186
--- /dev/null
+++ b/.opencode/tool-reason.ts
@@ -0,0 +1,10 @@
+import { tool } from "./tool.js";
+
+// One field and format for optional purpose and required business justification.
+export const toolReason = tool.schema.string().trim().min(1).max(2000);
+export const optionalToolReason = toolReason.optional().describe(
+  "Optional reason: one concise sentence explaining the specific purpose. Omit when the command already makes it clear.",
+);
+export const learningToolReason = toolReason.optional().describe(
+  "Reason: one concise sentence explaining the durable value or change basis. Required for every write, update or removal; optional for list.",
+);
diff --git a/.opencode/tools/clear_scada_analysis.ts b/.opencode/tools/clear_scada_analysis.ts
index a1495ea..4f700b8 100644
--- a/.opencode/tools/clear_scada_analysis.ts
+++ b/.opencode/tools/clear_scada_analysis.ts
@@ -1,3 +1,4 @@
+import { optionalToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 
 import { executeFrontendAction } from "./frontend_action.js";
@@ -5,11 +6,7 @@ import { executeFrontendAction } from "./frontend_action.js";
 export default tool({
   description: "清除当前浏览器地图上的 Agent SCADA 分析结果覆盖层。",
   args: {
-    reason: tool.schema
-      .string()
-      .trim()
-      .min(1)
-      .describe("Why the current SCADA analysis overlay should be cleared."),
+    reason: optionalToolReason,
   },
   async execute(args, context) {
     return executeFrontendAction("clear_scada_analysis", args, context);
diff --git a/.opencode/tools/locate_features.ts b/.opencode/tools/locate_features.ts
index b6d6f63..3fd147e 100644
--- a/.opencode/tools/locate_features.ts
+++ b/.opencode/tools/locate_features.ts
@@ -1,7 +1,8 @@
+import { optionalToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { executeFrontendAction } from "./frontend_action.js";
 export default tool({
   description: "在当前供水地图定位资产并等待浏览器执行回执。返回已定位和未找到的 ID，失败时不得宣称成功。",
-  args: { layer: tool.schema.enum(["junctions", "pipes", "valves", "pumps", "tanks", "reservoirs", "scada"]), feature_ids: tool.schema.array(tool.schema.string().min(1).max(128)).min(1).max(100), reason: tool.schema.string().max(2000) },
+  args: { layer: tool.schema.enum(["junctions", "pipes", "valves", "pumps", "tanks", "reservoirs", "scada"]), feature_ids: tool.schema.array(tool.schema.string().min(1).max(128)).min(1).max(100), reason: optionalToolReason },
   async execute(args, context) { return executeFrontendAction("locate_features", args, context); },
 });
diff --git a/.opencode/tools/memory_manager.ts b/.opencode/tools/memory_manager.ts
index 143e795..156d2e1 100644
--- a/.opencode/tools/memory_manager.ts
+++ b/.opencode/tools/memory_manager.ts
@@ -1,3 +1,4 @@
+import { learningToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { getInternalBridgeConfig } from "../internalBridge.js";
 
@@ -8,9 +9,7 @@ export default tool({
     action: tool.schema
       .enum(["add", "list", "replace", "remove"])
       .describe("Memory operation to perform."),
-    reason: tool.schema
-      .string()
-      .describe("Why this memory should be persisted for future requests."),
+    reason: learningToolReason,
     scope: tool.schema
       .string()
       .describe(
diff --git a/.opencode/tools/propose_task_action.ts b/.opencode/tools/propose_task_action.ts
index d1d41c5..ba23084 100644
--- a/.opencode/tools/propose_task_action.ts
+++ b/.opencode/tools/propose_task_action.ts
@@ -1,3 +1,4 @@
+import { toolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { getInternalBridgeConfig } from "../internalBridge.js";
 import { proposedTaskActionSchema } from "../../src/product/operational-task-contract.js";
@@ -7,7 +8,7 @@ export default tool({
   args: {
     request_id: tool.schema.string().describe("Stable UUID idempotency key for this proposal"),
     kind: tool.schema.enum(["create_work_order", "issue_command"]),
-    reason: tool.schema.string(),
+    reason: toolReason.describe("One concise sentence explaining the business basis for this proposed action."),
     payload: tool.schema.union([
       tool.schema.object({
         title: tool.schema.string(),
diff --git a/.opencode/tools/publish_execution_plan.ts b/.opencode/tools/publish_execution_plan.ts
index aeb8cea..0af80bf 100644
--- a/.opencode/tools/publish_execution_plan.ts
+++ b/.opencode/tools/publish_execution_plan.ts
@@ -1,3 +1,4 @@
+import { toolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { getInternalBridgeConfig } from "../internalBridge.js";
 import { newExecutionPlanSchema } from "../../src/routes/executionPlan.js";
@@ -8,7 +9,7 @@ export default tool({
     request_id: tool.schema.string().describe("Stable UUID idempotency key for this plan revision"),
     schema: tool.schema.enum(["execution-plan@2"]),
     title: tool.schema.string(),
-    reason: tool.schema.string().describe("Why the plan or node status changed"),
+    reason: toolReason.max(1000).describe("One concise sentence explaining why the plan or node status changed."),
     nodes: tool.schema.array(tool.schema.object({
       id: tool.schema.string(), title: tool.schema.string(),
       status: tool.schema.enum(["pending", "running", "waiting", "completed", "failed", "skipped", "cancelled"]),
diff --git a/.opencode/tools/render_scada_analysis.ts b/.opencode/tools/render_scada_analysis.ts
index 1d5cd47..55a0c01 100644
--- a/.opencode/tools/render_scada_analysis.ts
+++ b/.opencode/tools/render_scada_analysis.ts
@@ -1,3 +1,4 @@
+import { optionalToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 
 import { executeFrontendAction } from "./frontend_action.js";
@@ -8,11 +9,7 @@ export default tool({
   description:
     "将已经完成分析并确定等级的 SCADA 点位结果高亮、编号并定位到前端地图。等级只能来自已完成的分析结论。",
   args: {
-    reason: tool.schema
-      .string()
-      .trim()
-      .min(1)
-      .describe("Why the completed SCADA analysis should be rendered on the map."),
+    reason: optionalToolReason,
     items: tool.schema
       .array(
         tool.schema.object({
diff --git a/.opencode/tools/request_task_data_access.ts b/.opencode/tools/request_task_data_access.ts
index 4a54e3c..5241353 100644
--- a/.opencode/tools/request_task_data_access.ts
+++ b/.opencode/tools/request_task_data_access.ts
@@ -1,3 +1,4 @@
+import { toolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { getInternalBridgeConfig } from "../internalBridge.js";
 
@@ -10,7 +11,7 @@ export default tool({
       "workbench_runtime", "scada_devices", "scada_readings", "peripheral_points",
       "peripheral_work_orders", "peripheral_observations", "peripheral_test_data",
     ])).min(1),
-    reason: tool.schema.string().min(1),
+    reason: toolReason.describe("One concise sentence explaining which evidence gap requires the requested data access."),
   },
   async execute(args, context) {
     const { baseUrl, internalToken } = getInternalBridgeConfig();
diff --git a/.opencode/tools/show_chart.ts b/.opencode/tools/show_chart.ts
index ccb007c..271c7e0 100644
--- a/.opencode/tools/show_chart.ts
+++ b/.opencode/tools/show_chart.ts
@@ -1,7 +1,8 @@
+import { optionalToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { executeFrontendAction } from "./frontend_action.js";
 export default tool({
   description: "显示受控折线或柱状图并等待浏览器回执。不接收 ECharts 脚本或任意 option；数据须来自可信查询或用户输入。",
-  args: { title: tool.schema.string().max(200), chart_type: tool.schema.enum(["line", "bar"]), x_data: tool.schema.array(tool.schema.string().max(128)).min(1).max(100), series: tool.schema.array(tool.schema.object({ name: tool.schema.string().max(128), data: tool.schema.array(tool.schema.number().finite()).min(1).max(100) })).min(1).max(8), reason: tool.schema.string().max(2000) },
+  args: { title: tool.schema.string().max(200), chart_type: tool.schema.enum(["line", "bar"]), x_data: tool.schema.array(tool.schema.string().max(128)).min(1).max(100), series: tool.schema.array(tool.schema.object({ name: tool.schema.string().max(128), data: tool.schema.array(tool.schema.number().finite()).min(1).max(100) })).min(1).max(8), reason: optionalToolReason },
   async execute(args, context) { return executeFrontendAction("show_chart", args, context); },
 });
diff --git a/.opencode/tools/skill_manager.ts b/.opencode/tools/skill_manager.ts
index 01495be..1ad14e9 100644
--- a/.opencode/tools/skill_manager.ts
+++ b/.opencode/tools/skill_manager.ts
@@ -1,3 +1,4 @@
+import { learningToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { getInternalBridgeConfig } from "../internalBridge.js";
 
@@ -18,11 +19,7 @@ export default tool({
       "remove_script",
     ])
     .describe("Skill maintenance operation."),
-    reason: tool.schema
-    .string()
-    .describe(
-      "Why this skill maintenance action is justified for future reuse.",
-    ),
+    reason: learningToolReason,
     skill_path: tool.schema
     .string()
     .describe(
diff --git a/.opencode/tools/view_history.ts b/.opencode/tools/view_history.ts
index 5d8881a..f82cb6b 100644
--- a/.opencode/tools/view_history.ts
+++ b/.opencode/tools/view_history.ts
@@ -1,7 +1,8 @@
+import { optionalToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { executeFrontendAction } from "./frontend_action.js";
 export default tool({
   description: "查询当前项目资产最多24小时的监测历史并显示曲线面板，等待浏览器回执。使用服务返回的单位和数据，缺数时明确说明。仅普通会话可用。",
-  args: { element_type: tool.schema.enum(["junction", "pipe"]), element_id: tool.schema.string().min(1).max(128), start: tool.schema.string(), end: tool.schema.string(), reason: tool.schema.string().max(2000) },
+  args: { element_type: tool.schema.enum(["junction", "pipe"]), element_id: tool.schema.string().min(1).max(128), start: tool.schema.string(), end: tool.schema.string(), reason: optionalToolReason },
   async execute(args, context) { return executeFrontendAction("view_history", args, context); },
 });
diff --git a/.opencode/tools/zoom_to_map.ts b/.opencode/tools/zoom_to_map.ts
index 43bc366..ab086d9 100644
--- a/.opencode/tools/zoom_to_map.ts
+++ b/.opencode/tools/zoom_to_map.ts
@@ -1,7 +1,8 @@
+import { optionalToolReason } from "../tool-reason.js";
 import { tool } from "../tool.js";
 import { executeFrontendAction } from "./frontend_action.js";
 export default tool({
   description: "将当前地图缩放到 WGS84 经纬度并等待浏览器回执。",
-  args: { center: tool.schema.tuple([tool.schema.number().min(-180).max(180), tool.schema.number().min(-90).max(90)]), zoom: tool.schema.number().min(0).max(24), reason: tool.schema.string().max(2000) },
+  args: { center: tool.schema.tuple([tool.schema.number().min(-180).max(180), tool.schema.number().min(-90).max(90)]), zoom: tool.schema.number().min(0).max(24), reason: optionalToolReason },
   async execute(args, context) { return executeFrontendAction("zoom_to_map", args, context); },
 });
diff --git a/README.md b/README.md
index 6ef53d1..6971c34 100644
--- a/README.md
+++ b/README.md
@@ -403,6 +403,8 @@ Agent 服务的 API 前缀是 `/api/v1`，路径不再包含 `/agent/chat`。生
 
 这里是现有 HTTP/SSE 服务的 `tjwater` 扩展，映射 OpenCode 原生用户收件箱；不等同于 OpenAI WebSocket 的 `response.steer` 事件，官方协议边界见 [Mid-turn steering](https://developers.openai.com/api/docs/guides/steering)。验证命令 `bun tests/integration/response-input-smoke.ts` 使用隔离 OpenCode 和本机确定性模型，验证模式切换及队列后续输出，不调用付费推理。
 
+工具说明统一使用 `reason`，填写时用一句话说明具体目的或业务依据。普通查询不额外注入该参数，地图、图表和 SCADA 展示工具的说明可选；缺少可选说明不会触发警告。数据权限申请、处置提案和计划变更保留必填理由；`memory_manager` / `skill_manager` 的 `list` 可省略，其余修改操作在内部桥接接口强制校验非空理由。说明随调用进入审计（`reasonProvided` 仅表示是否提供），进度中有值才显示“说明”，不替代授权、审批或执行回执。新工具只使用 `reason`，旧事件别名仅兼容读取。
+
 流使用 `response.created`、`response.in_progress`、`response.output_item.added/done`、`response.content_part.added/done`、`response.output_text.delta/done` 和终态 `response.completed/failed/incomplete`，带单调递增的 `sequence_number`。中止返回 incomplete；未知原因不伪造标准 incomplete reason。进度、审批、问题、凭据续期、地图和富文本展示通过 `tjwater.<事件名>` 扩展携带 `response_id`。前端使用 Responses transport 接入现有 useChat 和 UIMessage 渲染；UIMessage 不再是生成接口的网络协议。标准流语义见 [OpenAI Responses streaming](https://developers.openai.com/api/docs/guides/streaming-responses)。
 
 当前支持文本、受权会话续接和流式/非流式生成；`previous_response_id`、客户端指定 tools、图片/文件输入及其余未实现参数均返回400，不能将此接口宣称为完整 OpenAI API 代理。模型推理仍由 OpenCode 执行，上游 provider 协议沿用 `agent-models.json` 的配置。`GET /session/:session_id/stream` 保留独立的会话状态订阅，事件包含 state、token、progress、done 等，用于历史恢复和已运行任务跟随；Server 的 `/api/v1/workbench/events` 继续承载业务事件。
diff --git a/src/routes/chatStream.ts b/src/routes/chatStream.ts
index dc763ae..d5d3912 100644
--- a/src/routes/chatStream.ts
+++ b/src/routes/chatStream.ts
@@ -877,16 +877,6 @@ export const streamPromptResponse = async ({
           ) {
             emittedToolParts.add(part.id);
             toolCallCount += 1;
-            if (!reason) {
-              logger.warn(
-                {
-                  tool: part.tool,
-                  sessionId: sessionId,
-                  clientSessionId,
-                },
-                "llm tool request missing reason",
-              );
-            }
             void writeLlmRequestAuditLog({
               kind: "tool",
               sessionId: sessionId,
diff --git a/src/routes/chatStreamEvents.ts b/src/routes/chatStreamEvents.ts
index a3311f5..20d3703 100644
--- a/src/routes/chatStreamEvents.ts
+++ b/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") {
diff --git a/src/routes/learningToolBridge.ts b/src/routes/learningToolBridge.ts
index a60d659..3b66842 100644
--- a/src/routes/learningToolBridge.ts
+++ b/src/routes/learningToolBridge.ts
@@ -9,19 +9,23 @@ import { type SkillStore } from "../skills/store.js";
 const memoryInput = z.object({
   action: z.enum(["add", "list", "replace", "remove"]),
   scope: z.string().max(32),
-  reason: z.string().max(2000).optional(),
+  reason: z.string().trim().min(1).max(2000).optional(),
   content: z.string().max(20000).optional(),
   target_id: z.string().max(128).optional(),
-}).strict();
+}).strict().refine((input) => input.action === "list" || Boolean(input.reason), {
+  path: ["reason"], message: "reason is required for writes, updates and removals",
+});
 const skillInput = z.object({
   action: z.enum(["list", "write_skill", "remove_skill", "append_pattern", "remove_pattern", "write_reference", "remove_reference", "write_script", "remove_script"]),
   skill_path: z.string().max(512),
-  reason: z.string().max(2000).optional(),
+  reason: z.string().trim().min(1).max(2000).optional(),
   content: z.string().max(200000).optional(),
   file_path: z.string().max(512).optional(),
   pattern: z.string().max(20000).optional(),
   target_id: z.string().max(128).optional(),
-}).strict();
+}).strict().refine((input) => input.action === "list" || Boolean(input.reason), {
+  path: ["reason"], message: "reason is required for writes, updates and removals",
+});
 
 export const registerLearningToolBridge = (app: Express, options: {
   internalToken: string;
diff --git a/tests/opencode/learningToolBridge.test.ts b/tests/opencode/learningToolBridge.test.ts
index b151bd4..2e4ba05 100644
--- a/tests/opencode/learningToolBridge.test.ts
+++ b/tests/opencode/learningToolBridge.test.ts
@@ -32,10 +32,10 @@ describe("learning tools across process boundaries", () => {
       'import memory from "./.opencode/tools/memory_manager.ts";',
       'import skill from "./.opencode/tools/skill_manager.ts";',
       'const ctx = { sessionID: "learning-bridge-session" };',
-      'const call = (action, content) => memory.execute({ action, scope: "user", reason: "test", content }, ctx).then(JSON.parse);',
+      'const call = (action, content) => memory.execute({ action, scope: "user", ...(action === "list" ? {} : { reason: "test" }), content }, ctx).then(JSON.parse);',
       'const before = await call("add", "用户偏好简洁答复");',
       'await call("list"); const added = await call("add", "用户偏好简洁答复");',
-      'const skills = JSON.parse(await skill.execute({ action: "list", skill_path: "__root__", reason: "test" }, ctx));',
+      'const skills = JSON.parse(await skill.execute({ action: "list", skill_path: "__root__" }, ctx));',
       'process.stdout.write(JSON.stringify({ before, added, skills }));',
     ].join("\n")], { cwd: process.cwd(), env: { ...process.env, AGENT_INTERNAL_TOKEN: "TEST_ONLY", TJWATER_AGENT_INTERNAL_BASE_URL: baseUrl }, stdout: "pipe", stderr: "pipe" });
     const [exitCode, stdout, stderr] = await Promise.all([child.exited, new Response(child.stdout).text(), new Response(child.stderr).text()]);
@@ -48,6 +48,21 @@ describe("learning tools across process boundaries", () => {
     expect(await memoryStore.list("user", "owner")).toHaveLength(1);
     expect(await memoryStore.list("user", "other-owner")).toHaveLength(0);
     const post = (sessionId: string, input: unknown, token = "TEST_ONLY") => fetch(`${baseUrl}/internal/tools/memory-manager`, { method: "POST", headers: { "Content-Type": "application/json", "x-agent-internal-token": token }, body: JSON.stringify({ session_id: sessionId, input }) });
+    // Invalid mutation reasons must fail before either store is changed.
+    for (const reason of [undefined, "", "   ", "x".repeat(2001)]) {
+      expect((await post("learning-bridge-session", {
+        action: "remove", scope: "user", target_id: "anything", reason,
+      })).status).toBe(400);
+      const skillResponse = await fetch(`${baseUrl}/internal/tools/skill-manager`, {
+        method: "POST",
+        headers: { "Content-Type": "application/json", "x-agent-internal-token": "TEST_ONLY" },
+        body: JSON.stringify({ session_id: "learning-bridge-session", input: {
+          action: "write_skill", skill_path: "test", content: "must not be written", reason,
+        } }),
+      });
+      expect(skillResponse.status).toBe(400);
+    }
+    expect(await memoryStore.list("user", "owner")).toHaveLength(1);
     expect((await post("missing", { action: "list", scope: "user" })).status).toBe(404);
     expect((await post("learning-bridge-session", { action: "list", scope: "user", actorKey: "other-owner" })).status).toBe(400);
     expect((await post("learning-bridge-session", { action: "list", scope: "user" }, "wrong")).status).toBe(403);
diff --git a/tests/opencode/toolReason.test.ts b/tests/opencode/toolReason.test.ts
new file mode 100644
index 0000000..87be4b3
--- /dev/null
+++ b/tests/opencode/toolReason.test.ts
@@ -0,0 +1,14 @@
+import { describe, expect, it } from "bun:test";
+import { optionalToolReason, toolReason } from "../../.opencode/tool-reason.js";
+
+describe("tool reason contract", () => {
+  it("allows omitted purpose but requires a nonblank business reason", () => {
+    expect(optionalToolReason.parse(undefined)).toBeUndefined();
+    expect(toolReason.safeParse(undefined).success).toBeFalse();
+    for (const schema of [optionalToolReason, toolReason]) {
+      expect(schema.parse("  核验压力异常  ")).toBe("核验压力异常");
+      expect(schema.safeParse("   ").success).toBeFalse();
+      expect(schema.safeParse("x".repeat(2001)).success).toBeFalse();
+    }
+  });
+});
diff --git a/tests/routes/toolReason.test.ts b/tests/routes/toolReason.test.ts
new file mode 100644
index 0000000..7773f88
--- /dev/null
+++ b/tests/routes/toolReason.test.ts
@@ -0,0 +1,17 @@
+import { describe, expect, it } from "bun:test";
+import { buildToolProgressDetail, extractRequestReason } from "../../src/routes/chatStreamEvents.js";
+
+describe("tool reason display", () => {
+  it("omits absent explanations and displays canonical or legacy reasons once", () => {
+    const plain = buildToolProgressDetail("query", "running", { id: "n1" }, "");
+    expect(plain).not.toContain("说明：");
+    expect(plain).not.toContain("原因：");
+    expect(plain).toContain("id=n1");
+    for (const input of [{ reason: "  核验压力异常  " }, { request_reason: "核验压力异常" }]) {
+      const detail = buildToolProgressDetail("query", "running", input, extractRequestReason(input));
+      expect(detail).toContain("；说明：核验压力异常");
+      expect(detail.match(/核验压力异常/g)).toHaveLength(1);
+    }
+    expect(extractRequestReason({ reason: "当前说明", purpose: "旧说明" })).toBe("当前说明");
+  });
+});