diff --git a/src/server/routes/session.ts b/src/server/routes/session.ts
index 463aca009..d76e328a4 100644
--- a/src/server/routes/session.ts
+++ b/src/server/routes/session.ts
@@ -11,6 +11,16 @@ import {
 } from '../errors.js'
 import { listSessionsImpl } from '../../utils/listSessionsImpl.js'
 
+/** 从磁盘历史记录查找 session 的原始 cwd，用于 resume 时恢复正确的工作目录 */
+async function getHistoryCwd(sessionId: string): Promise<string | undefined> {
+  try {
+    const list = await listSessionsImpl({ limit: 1000 })
+    return list.find(s => s.sessionId === sessionId)?.cwd
+  } catch {
+    return undefined
+  }
+}
+
 function ssePrompt(
   handle: import('../sessionHandle.js').SessionHandle,
   id: string,
@@ -354,8 +364,22 @@ export function createSessionRoutes(
     })
     .post('/session/:sessionID/prompt', async c => {
       const id = c.req.param('sessionID')
-      const handle = sessionManager.getSession(id)
-      if (!handle) throw notFound('session not found')
+      let handle = sessionManager.getSession(id)
+      if (!handle) {
+        const cwd = await getHistoryCwd(id)
+        try {
+          handle = await sessionManager.createSession({
+            cwd,
+            sessionId: id,
+            resumeSessionId: id,
+            execPath: process.execPath,
+            scriptArgs: getScriptArgsForChild(),
+          })
+          await handle.waitReady(30000)
+        } catch (err) {
+          throw sessionError(err instanceof Error ? err.message : 'Failed to resume session')
+        }
+      }
 
       const body = await c.req.json<{
         content?: string
@@ -381,9 +405,23 @@ export function createSessionRoutes(
     .post('/session/:sessionID/prompt_async', async c => {
       const id = c.req.param('sessionID')
 
-      const handle = sessionManager.getSession(id)
+      let handle = sessionManager.getSession(id)
+
+      // 历史 session 不在内存中，自动恢复
       if (!handle) {
-        throw notFound('session not found')
+        const cwd = await getHistoryCwd(id)
+        try {
+          handle = await sessionManager.createSession({
+            cwd,
+            sessionId: id,
+            resumeSessionId: id,
+            execPath: process.execPath,
+            scriptArgs: getScriptArgsForChild(),
+          })
+          await handle.waitReady(30000)
+        } catch (err) {
+          throw sessionError(err instanceof Error ? err.message : 'Failed to resume session')
+        }
       }
 
       const body = await c.req.json<{
diff --git a/src/server/sessionHandle.ts b/src/server/sessionHandle.ts
index 315b36d2a..96c24d1cf 100644
--- a/src/server/sessionHandle.ts
+++ b/src/server/sessionHandle.ts
@@ -245,8 +245,8 @@ export class SessionHandle {
       'stream-json',
       '--output-format',
       'stream-json',
-      '--session-id',
-      this.sessionId,
+      // resume 时不传 --session-id，csc 会继承历史 session 的 id
+      ...(this.opts.resumeSessionId ? [] : ['--session-id', this.sessionId]),
       ...(this.opts.model ? ['--model', this.opts.model] : []),
       '--permission-mode',
       this._permissionMode,
@@ -299,6 +299,7 @@ export class SessionHandle {
         const reject = this.initReject
         this.initResolve = null
         this.initReject = null
+        process.stderr.write(`[serve:${this.sessionId}] exit_code=${code} cwd=${this.cwd} stderr:\n${this.lastStderr.slice(-5).join('\n')}\n`)
         reject(new Error(`Process exited with code ${code}`))
       }
       if (this.promptReject) {
diff --git a/src/server/sessionManager.ts b/src/server/sessionManager.ts
index bc2d227cb..76618f464 100644
--- a/src/server/sessionManager.ts
+++ b/src/server/sessionManager.ts
@@ -155,6 +155,7 @@ export class SessionManager {
     execPath: string
     scriptArgs: string[]
     silent?: boolean
+    sessionId?: string
   }): Promise<SessionHandle> {
     if (this.maxSessions > 0 && this.sessions.size >= this.maxSessions) {
       throw new Error(
@@ -162,7 +163,7 @@ export class SessionManager {
       )
     }
 
-    const sessionId = crypto.randomUUID()
+    const sessionId = opts.sessionId ?? crypto.randomUUID()
     let cwd = opts.cwd || this.defaultWorkspace || process.cwd()
     if (!isAbsolute(cwd)) {
       cwd = resolve(process.cwd(), cwd)