fix(chat): avoid implicit stream reuse

src/routes/chat.ts

@@ -193,6 +193,21 @@ const pipeUiChunk = (
   }
 };
 
+export const resolveRequestedStreamSessionId = (input: {
+  sessionId?: string;
+  promptText: string;
+  createClientSessionId: () => string;
+}) => {
+  const sessionId = input.sessionId?.trim();
+  if (sessionId) {
+    return sessionId;
+  }
+  if (isPressureTrendDemoPrompt(input.promptText)) {
+    return input.createClientSessionId();
+  }
+  return undefined;
+};
+
 export const buildChatRouter = (
   sessionBridge: ChatSessionBridge,
   runtime: OpencodeRuntimeAdapter,
@@ -617,12 +632,11 @@ export const buildChatRouter = (
         });
         return;
       }
-      const requestedSessionId =
-        parsed.data.session_id?.trim() ||
-        parsed.data.id?.trim() ||
-        (isPressureTrendDemoPrompt(promptText)
-          ? sessionBridge.createClientSessionId()
-          : undefined);
+      const requestedSessionId = resolveRequestedStreamSessionId({
+        sessionId: parsed.data.session_id,
+        promptText,
+        createClientSessionId: () => sessionBridge.createClientSessionId(),
+      });
       const existingSessionRecord = requestedSessionId
         ? await sessionMetadataStore.get(
             { actorKey, projectId, projectKey, userId },

tests/routes/chatSession.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, it } from "bun:test";
 
 import {
   buildForkedSessionUiState,
+  resolveRequestedStreamSessionId,
 } from "../../src/routes/chat.js";
 import {
   buildPromptWithLearningContext,
@@ -14,6 +15,38 @@ import { type SessionTurnRecord } from "../../src/sessions/transcriptStore.js";
 import { type MemoryStore } from "../../src/memory/store.js";
 import { type OpencodeRuntimeAdapter } from "../../src/runtime/opencode.js";
 
+describe("resolveRequestedStreamSessionId", () => {
+  it("uses only explicit session_id for normal chat reuse", () => {
+    const createClientSessionId = () => {
+      throw new Error("should not create a demo session id");
+    };
+
+    expect(
+      resolveRequestedStreamSessionId({
+        sessionId: " existing-session ",
+        promptText: "检查压力异常",
+        createClientSessionId,
+      }),
+    ).toBe("existing-session");
+
+    expect(
+      resolveRequestedStreamSessionId({
+        promptText: "检查压力异常",
+        createClientSessionId,
+      }),
+    ).toBeUndefined();
+  });
+
+  it("keeps the pressure trend demo on its generated client session id", () => {
+    expect(
+      resolveRequestedStreamSessionId({
+        promptText: "展示最近压力趋势",
+        createClientSessionId: () => "demo-session",
+      }),
+    ).toBe("demo-session");
+  });
+});
+
 describe("shouldGenerateSessionTitle", () => {
   it("allows auto-title generation for the first turn when the title was not edited", () => {
     expect(