feat(sidebar): delete all sessions for a project (#74)

* feat(sidebar): delete all sessions for a project

Add a "Delete all sessions" option to the project context menu so a
project can be removed from the sidebar entirely (not just hidden).
Hide-from-sidebar is a UI-only soft toggle; this is a destructive
operation that wipes the on-disk artefacts.

Backend
- POST /api/projects/sessions/clear accepts { projectId } or
  { workDir } (the desktop client passes workDir; backend sanitizes).
- Deletes every .jsonl transcript and matching .summary.json sidecar
  under ~/.claude/projects/<sanitized-id>/. Sub-directories and other
  non-session files (memory/, user notes) are preserved.
- If the directory becomes empty, removes it so the project drops off
  the sidebar listing entirely.
- Defence in depth: rejects path-separator/null-byte/`.`/`..` ids and
  re-checks the resolved path stays under projectsDir.
- 11 backend tests covering traversal/null-byte/dot rejection, missing
  dir 200, full-clear+rmdir, non-jsonl preservation, summary sidecar
  deletion, workDir absolute-path acceptance, relative-path rejection,
  and 405 on GET.

Frontend
- Sidebar project context menu: red "Delete all sessions" entry
  (Trash2 icon, danger) below the hide entry.
- ConfirmDialog with project title + session count + irreversibility
  warning. Disconnects open sessions and closes their tabs before the
  call so the websocket layer doesn't keep stale handles.
- After success, fetchSessions() refreshes the list — the project
  disappears if its dir was removed, or shows up empty if memory/
  remained.
- 5 new i18n keys across en/zh/jp/kr/zh-TW.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* test(sidebar): cover projectsApi.clearSessions client behaviour

Wire-level guard for the desktop API helper introduced in this PR — the
sidebar's "Delete all sessions" flow depends on it sending the right
endpoint and body, and surfacing server errors back to the caller for
toast handling.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: 你的姓名 <you@example.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

desktop/src/api/projects.test.ts

@@ -0,0 +1,35 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import '@testing-library/jest-dom'
+
+const apiPostMock = vi.fn()
+
+vi.mock('./client', () => ({
+  api: {
+    post: (url: string, body?: unknown) => apiPostMock(url, body),
+    get: vi.fn(),
+  },
+}))
+
+import { projectsApi } from './projects'
+
+beforeEach(() => {
+  apiPostMock.mockReset()
+})
+
+describe('projectsApi.clearSessions', () => {
+  it('posts to /api/projects/sessions/clear with workDir in body', async () => {
+    apiPostMock.mockResolvedValue({ ok: true, deletedSessions: 3, projectDirRemoved: true })
+
+    const result = await projectsApi.clearSessions('/work/alpha')
+
+    expect(apiPostMock).toHaveBeenCalledTimes(1)
+    expect(apiPostMock).toHaveBeenCalledWith('/api/projects/sessions/clear', { workDir: '/work/alpha' })
+    expect(result.deletedSessions).toBe(3)
+    expect(result.projectDirRemoved).toBe(true)
+  })
+
+  it('propagates server errors so the caller can show a toast', async () => {
+    apiPostMock.mockRejectedValue(new Error('Forbidden'))
+    await expect(projectsApi.clearSessions('/work/beta')).rejects.toThrow('Forbidden')
+  })
+})

desktop/src/api/projects.ts

@@ -121,4 +121,18 @@ export const projectsApi = {
       return null
     }
   },
+
+  /**
+   * Permanently delete every .jsonl session file under the given project.
+   * Pass an absolute workDir (the desktop sidebar's project key) — the
+   * backend sanitizes it. If the project directory becomes empty, it is
+   * removed so the project drops off the sidebar entirely. Non-.jsonl files
+   * (memory/, user notes) are preserved.
+   */
+  clearSessions(workDir: string): Promise<{ ok: true; deletedSessions: number; projectDirRemoved: boolean }> {
+    return api.post<{ ok: true; deletedSessions: number; projectDirRemoved: boolean }>(
+      '/api/projects/sessions/clear',
+      { workDir },
+    )
+  },
 }

desktop/src/components/layout/Sidebar.tsx

@@ -1,5 +1,5 @@
 import { useEffect, useState, useCallback, useMemo, useRef } from 'react'
-import { Folder, FolderOpen, MoreHorizontal, Pin, PinOff, RefreshCw, RotateCcw, SquarePen, X } from 'lucide-react'
+import { Folder, FolderOpen, MoreHorizontal, Pin, PinOff, RefreshCw, RotateCcw, SquarePen, Trash2, X } from 'lucide-react'
 import { useSessionStore } from '../../stores/sessionStore'
 import { useUIStore } from '../../stores/uiStore'
 import { useTranslation } from '../../i18n'
@@ -39,6 +39,7 @@ import {
   positionProjectMenu,
   isDocumentVisible,
 } from './sidebarUtils'
+import { projectsApi } from '../../api/projects'
 import {
   GitHubIcon,
   PlusIcon,
@@ -98,6 +99,8 @@ export function Sidebar({ isMobile = false, onRequestClose }: SidebarProps) {
   const [pendingDeleteSessionId, setPendingDeleteSessionId] = useState<string | null>(null)
   const [pendingBatchDeleteSessionIds, setPendingBatchDeleteSessionIds] = useState<string[] | null>(null)
   const [isBatchDeleting, setIsBatchDeleting] = useState(false)
+  const [pendingClearProjectKey, setPendingClearProjectKey] = useState<string | null>(null)
+  const [isClearingProject, setIsClearingProject] = useState(false)
   const [renamingId, setRenamingId] = useState<string | null>(null)
   const [renameValue, setRenameValue] = useState('')
   const [lastSelectedSessionId, setLastSelectedSessionId] = useState<string | null>(null)
@@ -448,6 +451,61 @@ export function Sidebar({ isMobile = false, onRequestClose }: SidebarProps) {
     }
   }, [addToast, hiddenProjectKeys, persistSidebarProjectPreferences, pinnedProjectKeys, projectOrder, projectOrganization, projectSortBy, t])
 
+  const requestClearProjectSessions = useCallback((project: ProjectGroup) => {
+    setProjectContextMenu(null)
+    setPendingClearProjectKey(project.key)
+  }, [])
+
+  const confirmClearProjectSessions = useCallback(async () => {
+    if (!pendingClearProjectKey) return
+    const project = orderedProjectGroups.find((g) => g.key === pendingClearProjectKey)
+    if (!project) {
+      setPendingClearProjectKey(null)
+      return
+    }
+    const workDir = project.workDir
+    if (!workDir) {
+      addToast({
+        type: 'error',
+        message: t('sidebar.clearProjectSessionsNoWorkDir', { project: project.title }),
+      })
+      setPendingClearProjectKey(null)
+      return
+    }
+    setIsClearingProject(true)
+    try {
+      // Disconnect any open sessions for this project so the websocket
+      // server-side handles don't keep referencing files we're about to
+      // delete. closeTab handles missing tabs gracefully.
+      for (const session of project.sessions) {
+        try { closeTab(session.id) } catch { /* ignore */ }
+        try { disconnectSession(session.id) } catch { /* ignore */ }
+      }
+      const result = await projectsApi.clearSessions(workDir)
+      // Re-fetch sessions so the project either disappears (if dir removed)
+      // or shows up empty (preserved memory/ etc.).
+      await fetchSessions()
+      addToast({
+        type: 'success',
+        message: t('sidebar.clearProjectSessionsSuccess', {
+          project: project.title,
+          count: result.deletedSessions,
+        }),
+      })
+    } catch (error) {
+      addToast({
+        type: 'error',
+        message: t('sidebar.clearProjectSessionsFailure', {
+          project: project.title,
+          error: error instanceof Error ? error.message : String(error),
+        }),
+      })
+    } finally {
+      setIsClearingProject(false)
+      setPendingClearProjectKey(null)
+    }
+  }, [addToast, closeTab, disconnectSession, fetchSessions, orderedProjectGroups, pendingClearProjectKey, t])
+
   const openProjectInFinder = useCallback(async (project: ProjectGroup) => {
     setProjectContextMenu(null)
     try {
@@ -1149,6 +1207,13 @@ export function Sidebar({ isMobile = false, onRequestClose }: SidebarProps) {
             >
               {t(hidden ? 'sidebar.restoreProjectToSidebar' : 'sidebar.hideProjectFromSidebar')}
             </ProjectMenuItem>
+            <ProjectMenuItem
+              icon={<Trash2 size={18} aria-hidden="true" />}
+              onClick={() => requestClearProjectSessions(project)}
+              danger
+            >
+              {t('sidebar.clearProjectSessions')}
+            </ProjectMenuItem>
           </div>
         )
       })()}
@@ -1235,6 +1300,32 @@ export function Sidebar({ isMobile = false, onRequestClose }: SidebarProps) {
         confirmVariant="danger"
         loading={isBatchDeleting}
       />
+      <ConfirmDialog
+        open={pendingClearProjectKey !== null}
+        onClose={() => {
+          if (!isClearingProject) setPendingClearProjectKey(null)
+        }}
+        onConfirm={confirmClearProjectSessions}
+        title={t('sidebar.clearProjectSessions')}
+        body={(() => {
+          const project = pendingClearProjectKey
+            ? orderedProjectGroups.find((g) => g.key === pendingClearProjectKey)
+            : null
+          if (!project) return ''
+          return (
+            <p className="text-sm leading-6 text-[var(--color-text-secondary)]">
+              {t('sidebar.clearProjectSessionsConfirm', {
+                project: project.title,
+                count: project.sessions.length,
+              })}
+            </p>
+          )
+        })()}
+        confirmLabel={t('common.delete')}
+        cancelLabel={t('common.cancel')}
+        confirmVariant="danger"
+        loading={isClearingProject}
+      />
     </aside>
   )
 }

desktop/src/i18n/locales/en.ts

@@ -53,6 +53,11 @@ export const en = {
   'sidebar.restoreProjectToSidebar': 'Restore to Sidebar',
   'sidebar.restoreHiddenProjects': 'Restore hidden projects ({count})',
   'sidebar.projectHidden': '{project} was hidden from the sidebar. Existing sessions were not deleted.',
+  'sidebar.clearProjectSessions': 'Delete all sessions',
+  'sidebar.clearProjectSessionsConfirm': 'Permanently delete all {count} sessions in {project}? The project will be removed from the sidebar. This cannot be undone.',
+  'sidebar.clearProjectSessionsSuccess': 'Deleted {count} sessions from {project}.',
+  'sidebar.clearProjectSessionsFailure': 'Failed to delete sessions from {project}: {error}',
+  'sidebar.clearProjectSessionsNoWorkDir': 'Cannot delete sessions for {project}: working directory unknown.',
   'sidebar.newSessionInProject': 'New session in {project}',
   'sidebar.showMoreSessions': 'Expand display',
   'sidebar.showFewerSessions': 'Collapse display',

desktop/src/i18n/locales/jp.ts

@@ -55,6 +55,11 @@ export const jp: Record<TranslationKey, string> = {
   'sidebar.restoreProjectToSidebar': 'サイドバーに復元',
   'sidebar.restoreHiddenProjects': '非表示のプロジェクトを復元 ({count})',
   'sidebar.projectHidden': '{project} をサイドバーから非表示にしました。既存のセッションは削除されていません。',
+  'sidebar.clearProjectSessions': 'すべてのセッションを削除',
+  'sidebar.clearProjectSessionsConfirm': '{project} のすべての {count} 個のセッションを完全に削除しますか？プロジェクトはサイドバーから消えます。この操作は取り消せません。',
+  'sidebar.clearProjectSessionsSuccess': '{project} から {count} 個のセッションを削除しました。',
+  'sidebar.clearProjectSessionsFailure': '{project} のセッション削除に失敗しました：{error}',
+  'sidebar.clearProjectSessionsNoWorkDir': '{project} のセッションを削除できません：作業ディレクトリが不明です。',
   'sidebar.newSessionInProject': '{project} で新しいセッション',
   'sidebar.showMoreSessions': '表示を展開',
   'sidebar.showFewerSessions': '表示を折りたたむ',

desktop/src/i18n/locales/kr.ts

@@ -55,6 +55,11 @@ export const kr: Record<TranslationKey, string> = {
   'sidebar.restoreProjectToSidebar': '사이드바로 복원',
   'sidebar.restoreHiddenProjects': '숨긴 프로젝트 복원 ({count})',
   'sidebar.projectHidden': '{project}을(를) 사이드바에서 숨겼습니다. 기존 세션은 삭제되지 않았습니다.',
+  'sidebar.clearProjectSessions': '모든 세션 삭제',
+  'sidebar.clearProjectSessionsConfirm': '{project}의 모든 {count}개 세션을 영구적으로 삭제하시겠습니까? 프로젝트가 사이드바에서 제거됩니다. 이 작업은 되돌릴 수 없습니다.',
+  'sidebar.clearProjectSessionsSuccess': '{project}에서 {count}개 세션을 삭제했습니다.',
+  'sidebar.clearProjectSessionsFailure': '{project}의 세션 삭제 실패: {error}',
+  'sidebar.clearProjectSessionsNoWorkDir': '{project}의 세션을 삭제할 수 없습니다: 작업 디렉토리를 알 수 없습니다.',
   'sidebar.newSessionInProject': '{project}에서 새 세션',
   'sidebar.showMoreSessions': '펼쳐서 표시',
   'sidebar.showFewerSessions': '접어서 표시',

desktop/src/i18n/locales/zh-TW.ts

@@ -55,6 +55,11 @@ export const zh: Record<TranslationKey, string> = {
   'sidebar.restoreProjectToSidebar': '恢復到側邊欄',
   'sidebar.restoreHiddenProjects': '恢復隱藏專案（{count}）',
   'sidebar.projectHidden': '已從側邊欄隱藏 {project}，已有會話不會被刪除。',
+  'sidebar.clearProjectSessions': '刪除全部會話',
+  'sidebar.clearProjectSessionsConfirm': '確定永久刪除 {project} 中的全部 {count} 個會話？專案將從側邊欄消失。此操作無法撤銷。',
+  'sidebar.clearProjectSessionsSuccess': '已從 {project} 刪除 {count} 個會話。',
+  'sidebar.clearProjectSessionsFailure': '刪除 {project} 的會話失敗：{error}',
+  'sidebar.clearProjectSessionsNoWorkDir': '無法刪除 {project} 的會話：工作目錄未知。',
   'sidebar.newSessionInProject': '在 {project} 中新建會話',
   'sidebar.showMoreSessions': '展開顯示',
   'sidebar.showFewerSessions': '摺疊顯示',

desktop/src/i18n/locales/zh.ts

@@ -55,6 +55,11 @@ export const zh: Record<TranslationKey, string> = {
   'sidebar.restoreProjectToSidebar': '恢复到侧边栏',
   'sidebar.restoreHiddenProjects': '恢复隐藏项目（{count}）',
   'sidebar.projectHidden': '已从侧边栏隐藏 {project}，已有会话不会被删除。',
+  'sidebar.clearProjectSessions': '删除全部会话',
+  'sidebar.clearProjectSessionsConfirm': '确定永久删除 {project} 中的全部 {count} 个会话？项目将从侧边栏消失。此操作无法撤销。',
+  'sidebar.clearProjectSessionsSuccess': '已从 {project} 删除 {count} 个会话。',
+  'sidebar.clearProjectSessionsFailure': '删除 {project} 的会话失败：{error}',
+  'sidebar.clearProjectSessionsNoWorkDir': '无法删除 {project} 的会话：工作目录未知。',
   'sidebar.newSessionInProject': '在 {project} 中新建会话',
   'sidebar.showMoreSessions': '展开显示',
   'sidebar.showFewerSessions': '折叠显示',

src/server/__tests__/projects.test.ts

@@ -0,0 +1,184 @@
+import { describe, it, expect, mock, beforeEach } from 'bun:test'
+import * as path from 'path'
+
+const MOCK_CLAUDE_HOME = path.join('/mock', 'home', '.claude')
+const MOCK_PROJECTS_DIR = path.join(MOCK_CLAUDE_HOME, 'projects')
+
+mock.module('../../utils/envUtils.js', () => ({
+  getClaudeConfigHomeDir: () => MOCK_CLAUDE_HOME,
+}))
+
+mock.module('../../utils/path.js', () => ({
+  // Match the real sanitizePath behaviour for our test inputs: replace
+  // path separators and colons with '-'.
+  sanitizePath: (p: string) => p.replace(/[\\/:]/g, '-').replace(/^-+/, ''),
+}))
+
+// projectActivityService is unrelated to clear-sessions; stub it so the import
+// chain doesn't pull in real fs work.
+mock.module('../services/projectActivityService.js', () => ({
+  getRecentActivity: async () => ({ items: [] }),
+}))
+
+type FakeEntry = { name: string; isFile: () => boolean; isDirectory: () => boolean }
+const dirs = new Map<string, FakeEntry[]>()
+const unlinked: string[] = []
+const rmdired: string[] = []
+let nextRmdirError: NodeJS.ErrnoException | null = null
+
+mock.module('fs/promises', () => ({
+  readdir: async (dirPath: string, _opts?: unknown) => {
+    const entries = dirs.get(path.resolve(dirPath))
+    if (!entries) {
+      throw Object.assign(new Error('ENOENT'), { code: 'ENOENT' })
+    }
+    return entries
+  },
+  unlink: async (filePath: string) => {
+    unlinked.push(filePath)
+    // Remove the entry from its directory so a follow-up rmdir sees it as
+    // empty when only .jsonl files were present.
+    const dir = path.dirname(filePath)
+    const base = path.basename(filePath)
+    const list = dirs.get(path.resolve(dir))
+    if (list) dirs.set(path.resolve(dir), list.filter(e => e.name !== base))
+  },
+  rmdir: async (dirPath: string) => {
+    if (nextRmdirError) {
+      const err = nextRmdirError
+      nextRmdirError = null
+      throw err
+    }
+    rmdired.push(path.resolve(dirPath))
+    dirs.delete(path.resolve(dirPath))
+  },
+}))
+
+import { handleProjectsApi } from '../api/projects'
+
+function projectDir(id: string) {
+  return path.join(MOCK_PROJECTS_DIR, id)
+}
+
+function file(name: string): FakeEntry {
+  return { name, isFile: () => true, isDirectory: () => false }
+}
+
+function dir(name: string): FakeEntry {
+  return { name, isFile: () => false, isDirectory: () => true }
+}
+
+beforeEach(() => {
+  dirs.clear()
+  unlinked.length = 0
+  rmdired.length = 0
+  nextRmdirError = null
+})
+
+describe('POST /api/projects/sessions/clear', () => {
+  async function call(body: unknown): Promise<Response> {
+    const url = new URL('http://localhost/api/projects/sessions/clear')
+    const req = new Request(url, { method: 'POST', body: JSON.stringify(body) })
+    return handleProjectsApi(req, url, ['api', 'projects', 'sessions', 'clear'])
+  }
+
+  it('rejects invalid projectId (path separators)', async () => {
+    const res = await call({ projectId: '../escaped' })
+    expect(res.status).toBe(400)
+  })
+
+  it('rejects missing projectId', async () => {
+    const res = await call({})
+    expect(res.status).toBe(400)
+  })
+
+  it('rejects projectId with null byte', async () => {
+    const res = await call({ projectId: 'foo\0bar' })
+    expect(res.status).toBe(400)
+  })
+
+  it('rejects . and ..', async () => {
+    expect((await call({ projectId: '.' })).status).toBe(400)
+    expect((await call({ projectId: '..' })).status).toBe(400)
+  })
+
+  it('returns ok with 0 deletes when project dir does not exist', async () => {
+    const res = await call({ projectId: 'C--Users-70641-vanished' })
+    expect(res.status).toBe(200)
+    const data = await res.json() as { ok: boolean; deletedSessions: number; projectDirRemoved: boolean }
+    expect(data.ok).toBe(true)
+    expect(data.deletedSessions).toBe(0)
+    expect(data.projectDirRemoved).toBe(false)
+  })
+
+  it('deletes all .jsonl files and removes the now-empty project dir', async () => {
+    const id = 'C--Users-70641-myproj'
+    dirs.set(path.resolve(projectDir(id)), [
+      file('a.jsonl'),
+      file('b.jsonl'),
+      file('c.jsonl'),
+    ])
+    const res = await call({ projectId: id })
+    expect(res.status).toBe(200)
+    const data = await res.json() as { deletedSessions: number; projectDirRemoved: boolean }
+    expect(data.deletedSessions).toBe(3)
+    expect(data.projectDirRemoved).toBe(true)
+    expect(unlinked).toHaveLength(3)
+    expect(rmdired).toContain(path.resolve(projectDir(id)))
+  })
+
+  it('keeps non-.jsonl files and does not remove the directory', async () => {
+    const id = 'C--Users-70641-keep-state'
+    dirs.set(path.resolve(projectDir(id)), [
+      file('session.jsonl'),
+      file('user-notes.txt'),
+      dir('memory'),
+    ])
+    const res = await call({ projectId: id })
+    const data = await res.json() as { deletedSessions: number; projectDirRemoved: boolean }
+    expect(data.deletedSessions).toBe(1)
+    expect(data.projectDirRemoved).toBe(false)
+    expect(unlinked).toHaveLength(1)
+    expect(rmdired).toHaveLength(0)
+  })
+
+  it('GET on /sessions/clear returns 405', async () => {
+    const url = new URL('http://localhost/api/projects/sessions/clear')
+    const req = new Request(url, { method: 'GET' })
+    const res = await handleProjectsApi(req, url, ['api', 'projects', 'sessions', 'clear'])
+    expect(res.status).toBe(405)
+  })
+
+  it('accepts an absolute workDir and sanitizes it server-side', async () => {
+    // Stub sanitizes "/Users/me/proj" -> "Users-me-proj".
+    const sanitizedId = 'Users-me-proj'
+    dirs.set(path.resolve(projectDir(sanitizedId)), [file('a.jsonl')])
+
+    const res = await call({ workDir: '/Users/me/proj' })
+    expect(res.status).toBe(200)
+    const data = await res.json() as { deletedSessions: number; projectDirRemoved: boolean }
+    expect(data.deletedSessions).toBe(1)
+    expect(data.projectDirRemoved).toBe(true)
+  })
+
+  it('rejects a relative workDir', async () => {
+    const res = await call({ workDir: 'relative/path' })
+    expect(res.status).toBe(400)
+  })
+
+  it('also deletes per-session summary sidecars (.summary.json) and removes the empty dir', async () => {
+    const id = 'C--Users-70641-with-summaries'
+    dirs.set(path.resolve(projectDir(id)), [
+      file('a.jsonl'),
+      file('a.summary.json'),
+      file('b.jsonl'),
+      file('b.summary.json'),
+    ])
+    const res = await call({ projectId: id })
+    expect(res.status).toBe(200)
+    const data = await res.json() as { deletedSessions: number; projectDirRemoved: boolean }
+    expect(data.deletedSessions).toBe(2) // counts .jsonl files
+    expect(data.projectDirRemoved).toBe(true) // both .jsonl + .summary.json gone
+    expect(unlinked).toHaveLength(4)
+  })
+})

src/server/api/projects.ts

@@ -1,16 +1,135 @@
 /**
- * /api/projects/* — read-only endpoints derived from the on-disk projects
+ * /api/projects/* — endpoints derived from the on-disk projects directory
- * directory (`~/.claude/projects/<sanitized-workDir>/...`) plus git state.
+ * (`~/.claude/projects/<sanitized-workDir>/...`) plus git state.
  *
  * Currently exposes:
  *   GET  /api/projects/recent-activity?workDir=<absolute-path>
+ *   POST /api/projects/sessions/clear  body: { projectId }
  *
- * which returns a "what was the user just doing in this project" snapshot
+ * The first returns a "what was the user just doing in this project" snapshot
- * for the desktop welcome screen. Pure derivation — never invokes a model.
+ * for the desktop welcome screen. The second permanently deletes every .jsonl
+ * session file under the named project id (and removes the now-empty project
+ * directory) so the project disappears from the sidebar/listings.
  */
 
+import * as fs from 'fs/promises'
+import * as path from 'path'
 import { ApiError, errorResponse } from '../middleware/errorHandler.js'
 import { getRecentActivity } from '../services/projectActivityService.js'
+import { getClaudeConfigHomeDir } from '../../utils/envUtils.js'
+import { sanitizePath } from '../../utils/path.js'
+
+function getProjectsDir(): string {
+  return path.join(getClaudeConfigHomeDir(), 'projects')
+}
+
+function isValidProjectId(projectId: string): boolean {
+  return (
+    typeof projectId === 'string' &&
+    projectId.length > 0 &&
+    !projectId.includes('\0') &&
+    !projectId.includes('/') &&
+    !projectId.includes('\\') &&
+    projectId !== '.' &&
+    projectId !== '..'
+  )
+}
+
+async function clearProjectSessions(req: Request): Promise<Response> {
+  let body: unknown
+  try {
+    body = await req.json()
+  } catch {
+    throw ApiError.badRequest('Invalid JSON body')
+  }
+
+  const { projectId, workDir } = body as { projectId?: unknown; workDir?: unknown }
+
+  // Accept either projectId (already sanitized) or workDir (an absolute path
+  // that we sanitize ourselves). The desktop client passes workDir; backend
+  // tooling can pass projectId directly.
+  let resolvedId: string
+  if (typeof projectId === 'string' && projectId.length > 0) {
+    if (!isValidProjectId(projectId)) {
+      throw ApiError.badRequest('Invalid projectId')
+    }
+    resolvedId = projectId
+  } else if (typeof workDir === 'string' && workDir.length > 0 && path.isAbsolute(workDir)) {
+    resolvedId = sanitizePath(workDir)
+    if (!isValidProjectId(resolvedId)) {
+      throw ApiError.badRequest('workDir sanitized to an invalid id')
+    }
+  } else {
+    throw ApiError.badRequest('Provide projectId or absolute workDir')
+  }
+
+  const projectsDir = path.resolve(getProjectsDir())
+  const projectDir = path.join(projectsDir, resolvedId)
+
+  // Defence in depth: even though isValidProjectId rejects path separators,
+  // verify the resolved directory still sits under the projects dir.
+  const resolvedProjectDir = path.resolve(projectDir)
+  if (
+    resolvedProjectDir !== path.join(projectsDir, resolvedId) ||
+    !resolvedProjectDir.startsWith(projectsDir + path.sep)
+  ) {
+    throw ApiError.badRequest('projectId resolves outside projects directory')
+  }
+
+  let entries: import('node:fs').Dirent[]
+  try {
+    entries = await fs.readdir(resolvedProjectDir, { withFileTypes: true })
+  } catch (error) {
+    if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
+      return Response.json({ ok: true, deletedSessions: 0, projectDirRemoved: false })
+    }
+    throw error
+  }
+
+  let deletedSessions = 0
+  let nonSessionEntries = 0
+  for (const entry of entries) {
+    if (!entry.isFile()) {
+      // Sub-directories (e.g. workspace snapshots tied to a session) are
+      // intentionally preserved — they may hold user state we shouldn't drop.
+      nonSessionEntries += 1
+      continue
+    }
+    // Per-session artefacts: the JSONL transcript, plus its sidecar summary.
+    if (entry.name.endsWith('.jsonl')) {
+      try {
+        await fs.unlink(path.join(resolvedProjectDir, entry.name))
+        deletedSessions += 1
+      } catch (error) {
+        if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error
+      }
+      continue
+    }
+    if (entry.name.endsWith('.summary.json')) {
+      try {
+        await fs.unlink(path.join(resolvedProjectDir, entry.name))
+      } catch (error) {
+        if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error
+      }
+      continue
+    }
+    nonSessionEntries += 1
+  }
+
+  // If the directory is now empty (no leftover memory/, etc.), remove it so
+  // the project drops off the sidebar entirely.
+  let projectDirRemoved = false
+  if (nonSessionEntries === 0) {
+    try {
+      await fs.rmdir(resolvedProjectDir)
+      projectDirRemoved = true
+    } catch {
+      // Race with another writer or non-empty after all — leave directory.
+    }
+  }
+
+  return Response.json({ ok: true, deletedSessions, projectDirRemoved })
+}
 
 export async function handleProjectsApi(
   req: Request,
@@ -38,6 +157,17 @@ export async function handleProjectsApi(
       return Response.json(result)
     }
 
+    if (sub === 'sessions' && segments[3] === 'clear') {
+      if (req.method !== 'POST') {
+        throw new ApiError(
+          405,
+          `Method ${req.method} not allowed on /api/projects/sessions/clear`,
+          'METHOD_NOT_ALLOWED',
+        )
+      }
+      return await clearProjectSessions(req)
+    }
+
     throw ApiError.notFound(`Unknown projects endpoint: ${sub ?? '(root)'}`)
   } catch (error) {
     return errorResponse(error)