Merge pull request #9055 from continuedev/nate/feat-session-id-persistence

feat(cli): add session ID support for serve command to persist chat history

Author: sestinj

extensions/cli/src/commands/serve.ts

@@ -23,7 +23,11 @@ import {
   ConfigServiceState,
   ModelServiceState,
 } from "../services/types.js";
-import { createSession, getCompleteStateSnapshot } from "../session.js";
+import {
+  createSession,
+  getCompleteStateSnapshot,
+  loadOrCreateSessionById,
+} from "../session.js";
 import { messageQueue } from "../stream/messageQueue.js";
 import { constructSystemMessage } from "../systemMessage.js";
 import { telemetryService } from "../telemetry/telemetryService.js";
@@ -142,7 +146,11 @@ export async function serve(prompt?: string, options: ServeOptions = {}) {
     });
   }
 
-  const session = createSession(initialHistory);
+  const trimmedId = options.id?.trim();
+  const session =
+    trimmedId && trimmedId.length > 0
+      ? loadOrCreateSessionById(trimmedId, initialHistory)
+      : createSession(initialHistory);
 
   // Align ChatHistoryService with server session and enable remote mode
   try {

extensions/cli/src/session.test.ts

@@ -10,6 +10,7 @@ import {
   createSession,
   getCurrentSession,
   hasSession,
+  loadOrCreateSessionById,
   loadSession,
   saveSession,
   startNewSession,
@@ -36,17 +37,24 @@ vi.mock("./util/logger.js", () => ({
     error: vi.fn(),
   },
 }));
-vi.mock("../../core/util/history.js", () => ({
-  default: {
-    save: vi.fn(),
-    load: vi.fn(() => ({
-      sessionId: "test-session-id",
-      title: "Test Session",
-      workspaceDirectory: "/test/workspace",
-      history: [],
-    })),
-    list: vi.fn(() => []),
-  },
+const mockHistoryManager: any = vi.hoisted(() => ({
+  save: vi.fn((session: any) => {
+    // Mimic writing the session payload to disk so expectations on fs still work
+    fs.writeFileSync(
+      `/home/test/.continue/sessions/${session.sessionId}.json`,
+      JSON.stringify(session),
+    );
+  }),
+  load: vi.fn(() => ({
+    sessionId: "test-session-id",
+    title: "Test Session",
+    workspaceDirectory: "/test/workspace",
+    history: [],
+  })),
+  list: vi.fn(() => []),
+}));
+vi.mock("core/util/history.js", () => ({
+  default: mockHistoryManager,
 }));
 
 const mockFs = vi.mocked(fs);
@@ -71,6 +79,9 @@ describe("SessionManager", () => {
     mockFs.readFileSync.mockReturnValue("[]");
     mockFs.readdirSync.mockReturnValue([]);
     mockFs.statSync.mockReturnValue({ mtime: new Date() } as any);
+
+    // Ensure each test starts with a fresh session
+    clearSession();
   });
 
   describe("getCurrentSession", () => {
@@ -145,6 +156,13 @@ describe("SessionManager", () => {
 
       expect(currentSession).toBe(session);
     });
+
+    it("should use provided sessionId when supplied", () => {
+      const session = createSession([], "custom-session-id");
+
+      expect(session.sessionId).toBe("custom-session-id");
+      expect(uuidv4).not.toHaveBeenCalled();
+    });
   });
 
   describe("updateSessionHistory", () => {
@@ -235,6 +253,42 @@ describe("SessionManager", () => {
     });
   });
 
+  describe("loadOrCreateSessionById", () => {
+    it("should load an existing session and set it as current", () => {
+      const existingSession: Session = {
+        sessionId: "existing-id",
+        title: "Existing",
+        workspaceDirectory: "/test/workspace",
+        history: [
+          {
+            message: { role: "user", content: "hi" },
+            contextItems: [],
+          },
+        ],
+      };
+
+      mockHistoryManager.load.mockReturnValue(existingSession);
+
+      const session = loadOrCreateSessionById("existing-id");
+
+      expect(session).toBe(existingSession);
+      expect(mockHistoryManager.load).toHaveBeenCalledWith("existing-id");
+      expect(getCurrentSession()).toBe(existingSession);
+    });
+
+    it("should create a new session when none exists for the id", () => {
+      mockHistoryManager.load.mockImplementation(() => {
+        throw new Error("not found");
+      });
+
+      const session = loadOrCreateSessionById("new-id");
+
+      expect(session.sessionId).toBe("new-id");
+      expect(session.history).toEqual([]);
+      expect(getCurrentSession()).toBe(session);
+    });
+  });
+
   describe("loadSession", () => {
     it("should return null if session directory doesn't exist", () => {
       mockFs.existsSync.mockReturnValue(false);

extensions/cli/src/session.ts

@@ -316,9 +316,12 @@ export function loadSession(): Session | null {
 /**
  * Create a new session
  */
-export function createSession(history: ChatHistoryItem[] = []): Session {
+export function createSession(
+  history: ChatHistoryItem[] = [],
+  sessionId?: string,
+): Session {
   const session: Session = {
-    sessionId: uuidv4(),
+    sessionId: sessionId ?? uuidv4(),
     title: DEFAULT_SESSION_TITLE,
     workspaceDirectory: process.cwd(),
     history,
@@ -526,6 +529,24 @@ export function loadSessionById(sessionId: string): Session | null {
   }
 }
 
+/**
+ * Load an existing session by ID or create a new one with that ID.
+ * Useful for long-lived processes (e.g., cn serve) that need to
+ * preserve chat history across restarts for the same storage/agent id.
+ */
+export function loadOrCreateSessionById(
+  sessionId: string,
+  history: ChatHistoryItem[] = [],
+): Session {
+  const existing = loadSessionById(sessionId);
+  if (existing) {
+    SessionManager.getInstance().setSession(existing);
+    return existing;
+  }
+
+  return createSession(history, sessionId);
+}
+
 /**
  * Update the current session's history
  */