diff --git a/src/main/claude-accounts/service.test.ts b/src/main/claude-accounts/service.test.ts
index 454067ad5..8a537140d 100644
--- a/src/main/claude-accounts/service.test.ts
+++ b/src/main/claude-accounts/service.test.ts
@@ -1099,4 +1099,195 @@ describe('ClaudeAccountService credential capture', () => {
       vi.doUnmock('node:child_process')
     }
   })
+
+  it('cancels an in-flight Claude account add', async () => {
+    vi.resetModules()
+    const child = new EventEmitter() as EventEmitter & {
+      stdout: PassThrough
+      stderr: PassThrough
+      kill: ReturnType<typeof vi.fn>
+    }
+    child.stdout = new PassThrough()
+    child.stderr = new PassThrough()
+    child.kill = vi.fn()
+    const spawnMock = vi.fn(() => child)
+    vi.doMock('node:child_process', () => ({ spawn: spawnMock }))
+
+    try {
+      const { ClaudeAccountService } = await import('./service')
+      let settings = {
+        claudeManagedAccounts: [],
+        activeClaudeManagedAccountId: null,
+        activeClaudeManagedAccountIdsByRuntime: { host: null, wsl: {} }
+      }
+      const store = {
+        getSettings: vi.fn(() => settings),
+        updateSettings: vi.fn((updates: Partial<typeof settings>) => {
+          settings = { ...settings, ...updates }
+          return settings
+        })
+      }
+      const runtimeAuth = {
+        clearLastWrittenCredentialsJson: vi.fn(),
+        forceMaterializeCurrentSelectionForRollback: vi.fn(async () => {})
+      }
+      const rateLimits = {
+        evictInactiveClaudeCache: vi.fn(),
+        refreshForClaudeAccountChange: vi.fn()
+      }
+      const service = new ClaudeAccountService(
+        store as never,
+        rateLimits as never,
+        runtimeAuth as never
+      )
+
+      const addPromise = service.addAccount()
+      await vi.waitFor(() => {
+        expect(spawnMock).toHaveBeenCalledTimes(1)
+      })
+
+      expect(service.cancelPendingLogin()).toBe(true)
+      await expect(addPromise).rejects.toThrow('Claude sign-in was cancelled.')
+      expect(child.kill).toHaveBeenCalledTimes(1)
+      expect(service.cancelPendingLogin()).toBe(false)
+      expect(settings.claudeManagedAccounts).toEqual([])
+      expect(child.stdout.listenerCount('data')).toBe(0)
+      expect(child.stderr.listenerCount('data')).toBe(0)
+      expect(child.listenerCount('error')).toBe(0)
+      expect(child.listenerCount('close')).toBe(0)
+    } finally {
+      vi.doUnmock('node:child_process')
+    }
+  })
+
+  it('honors cancel before Claude login command starts', async () => {
+    setPlatform('linux')
+    vi.resetModules()
+    let releaseKeychainRead: (value: string | null) => void = () => {}
+    vi.mocked(readActiveClaudeKeychainCredentials).mockReturnValue(
+      new Promise<string | null>((resolve) => {
+        releaseKeychainRead = resolve
+      })
+    )
+    const spawnMock = vi.fn()
+    vi.doMock('node:child_process', () => ({ spawn: spawnMock }))
+
+    try {
+      const { ClaudeAccountService } = await import('./service')
+      let settings = {
+        claudeManagedAccounts: [],
+        activeClaudeManagedAccountId: null,
+        activeClaudeManagedAccountIdsByRuntime: { host: null, wsl: {} }
+      }
+      const store = {
+        getSettings: vi.fn(() => settings),
+        updateSettings: vi.fn((updates: Partial<typeof settings>) => {
+          settings = { ...settings, ...updates }
+          return settings
+        })
+      }
+      const runtimeAuth = {
+        clearLastWrittenCredentialsJson: vi.fn(),
+        forceMaterializeCurrentSelectionForRollback: vi.fn(async () => {})
+      }
+      const rateLimits = {
+        evictInactiveClaudeCache: vi.fn(),
+        refreshForClaudeAccountChange: vi.fn()
+      }
+      const service = new ClaudeAccountService(
+        store as never,
+        rateLimits as never,
+        runtimeAuth as never
+      )
+
+      const addPromise = service.addAccount()
+      await vi.waitFor(() => {
+        expect(readActiveClaudeKeychainCredentials).toHaveBeenCalled()
+      })
+
+      expect(service.cancelPendingLogin()).toBe(true)
+      expect(service.cancelPendingLogin()).toBe(false)
+      expect(spawnMock).not.toHaveBeenCalled()
+      releaseKeychainRead(null)
+      await expect(addPromise).rejects.toThrow('Claude sign-in was cancelled.')
+      expect(spawnMock).not.toHaveBeenCalled()
+      expect(service.cancelPendingLogin()).toBe(false)
+      expect(settings.claudeManagedAccounts).toEqual([])
+    } finally {
+      vi.doUnmock('node:child_process')
+    }
+  })
+
+  it('uses taskkill to cancel the Windows Claude login process tree', async () => {
+    setPlatform('win32')
+    vi.resetModules()
+    vi.mocked(readActiveClaudeKeychainCredentials).mockResolvedValue(null)
+    const child = new EventEmitter() as EventEmitter & {
+      pid: number
+      stdout: PassThrough
+      stderr: PassThrough
+      kill: ReturnType<typeof vi.fn>
+    }
+    child.pid = 1234
+    child.stdout = new PassThrough()
+    child.stderr = new PassThrough()
+    child.kill = vi.fn()
+    const taskkill = new EventEmitter() as EventEmitter & {
+      unref: ReturnType<typeof vi.fn>
+    }
+    taskkill.unref = vi.fn()
+    const spawnMock = vi.fn((command: string) => (command === 'taskkill.exe' ? taskkill : child))
+    vi.doMock('node:child_process', () => ({ spawn: spawnMock }))
+
+    try {
+      const { ClaudeAccountService } = await import('./service')
+      let settings = {
+        claudeManagedAccounts: [],
+        activeClaudeManagedAccountId: null,
+        activeClaudeManagedAccountIdsByRuntime: { host: null, wsl: {} }
+      }
+      const store = {
+        getSettings: vi.fn(() => settings),
+        updateSettings: vi.fn((updates: Partial<typeof settings>) => {
+          settings = { ...settings, ...updates }
+          return settings
+        })
+      }
+      const runtimeAuth = {
+        clearLastWrittenCredentialsJson: vi.fn(),
+        forceMaterializeCurrentSelectionForRollback: vi.fn(async () => {})
+      }
+      const rateLimits = {
+        evictInactiveClaudeCache: vi.fn(),
+        refreshForClaudeAccountChange: vi.fn()
+      }
+      const service = new ClaudeAccountService(
+        store as never,
+        rateLimits as never,
+        runtimeAuth as never
+      )
+
+      const addPromise = service.addAccount()
+      await vi.waitFor(() => {
+        expect(spawnMock).toHaveBeenCalledWith(
+          'claude',
+          ['auth', 'login', '--claudeai'],
+          expect.objectContaining({ shell: true })
+        )
+      })
+
+      expect(service.cancelPendingLogin()).toBe(true)
+      await expect(addPromise).rejects.toThrow('Claude sign-in was cancelled.')
+      expect(child.kill).not.toHaveBeenCalled()
+      expect(spawnMock).toHaveBeenCalledWith(
+        'taskkill.exe',
+        ['/pid', '1234', '/t', '/f'],
+        expect.objectContaining({ stdio: 'ignore', windowsHide: true })
+      )
+      expect(taskkill.unref).toHaveBeenCalled()
+      expect(service.cancelPendingLogin()).toBe(false)
+    } finally {
+      vi.doUnmock('node:child_process')
+    }
+  })
 })
diff --git a/src/main/claude-accounts/service.ts b/src/main/claude-accounts/service.ts
index e225f9326..0333dc200 100644
--- a/src/main/claude-accounts/service.ts
+++ b/src/main/claude-accounts/service.ts
@@ -83,6 +83,7 @@ function shellQuote(value: string): string {
 
 export class ClaudeAccountService {
   private mutationQueue: Promise<unknown> = Promise.resolve()
+  private cancelPendingClaudeLogin: (() => boolean) | null = null
 
   constructor(
     private readonly store: Store,
@@ -118,6 +119,10 @@ export class ClaudeAccountService {
     return this.serializeMutation(() => this.doSelectAccount(accountId, target))
   }
 
+  cancelPendingLogin(): boolean {
+    return this.cancelPendingClaudeLogin?.() ?? false
+  }
+
   private serializeMutation<T>(fn: () => Promise<T>): Promise<T> {
     const next = this.mutationQueue.then(fn, fn)
     this.mutationQueue = next.catch(() => {})
@@ -424,12 +429,26 @@ export class ClaudeAccountService {
     }
   ): Promise<CapturedClaudeAuth> {
     const tempConfig = this.createTemporaryClaudeConfigDir(location)
+    const loginAbortController = new AbortController()
+    this.cancelPendingClaudeLogin = () => {
+      if (loginAbortController.signal.aborted) {
+        return false
+      }
+      loginAbortController.abort()
+      return true
+    }
     const previousLegacyKeychain = await readActiveClaudeKeychainCredentials()
     let captured: CapturedClaudeAuth | null = null
     let captureError: unknown = null
     let cleanupError: unknown = null
     try {
-      await this.runClaudeCommand(['auth', 'login', '--claudeai'], tempConfig, LOGIN_TIMEOUT_MS)
+      if (loginAbortController.signal.aborted) {
+        throw new Error('Claude sign-in was cancelled.')
+      }
+      await this.runClaudeCommand(['auth', 'login', '--claudeai'], tempConfig, LOGIN_TIMEOUT_MS, {
+        signal: loginAbortController.signal
+      })
+      this.cancelPendingClaudeLogin = null
       const status = await this.runClaudeCommand(
         ['auth', 'status', '--json'],
         tempConfig,
@@ -463,6 +482,7 @@ export class ClaudeAccountService {
         }
       }
       this.removeTemporaryClaudeConfigDir(tempConfig)
+      this.cancelPendingClaudeLogin = null
     }
     if (captureError) {
       throw captureError
@@ -862,7 +882,7 @@ export class ClaudeAccountService {
     args: string[],
     configDir: { windowsPath: string; linuxPath: string | null; wslDistro: string | null },
     timeoutMs: number,
-    options?: { allowFailure?: boolean }
+    options?: { allowFailure?: boolean; signal?: AbortSignal }
   ): Promise<string> {
     return new Promise((resolvePromise, rejectPromise) => {
       const spawnConfig =
@@ -892,7 +912,10 @@ export class ClaudeAccountService {
       const child = spawn(spawnConfig.command, spawnConfig.args, {
         stdio: ['ignore', 'pipe', 'pipe'],
         shell: spawnConfig.shell,
-        env: spawnConfig.env
+        env: spawnConfig.env,
+        // Why: Claude auth can leave browser/login descendants alive after denial.
+        // A process group lets cancellation terminate the whole POSIX login tree.
+        detached: process.platform !== 'win32'
       })
 
       let settled = false
@@ -913,6 +936,7 @@ export class ClaudeAccountService {
         child.stderr.off('data', appendOutput)
         child.off('error', onError)
         child.off('close', onClose)
+        options?.signal?.removeEventListener('abort', onAbort)
       }
       const settle = (callback: () => void): void => {
         if (settled) {
@@ -923,11 +947,36 @@ export class ClaudeAccountService {
         callback()
       }
       const timeoutError = new Error('Claude sign-in took too long to finish.')
-      timeout = setTimeout(() => {
+      const cancelError = new Error('Claude sign-in was cancelled.')
+      const killChild = (): void => {
+        if (process.platform === 'win32' && child.pid) {
+          const taskkill = spawn('taskkill.exe', ['/pid', String(child.pid), '/t', '/f'], {
+            stdio: 'ignore',
+            windowsHide: true
+          })
+          taskkill.on('error', () => {})
+          taskkill.unref()
+          return
+        }
+        if (process.platform !== 'win32' && child.pid) {
+          try {
+            process.kill(-child.pid)
+            return
+          } catch {
+            // Fall back to the direct child if the process group is unavailable.
+          }
+        }
         child.kill()
+      }
+      timeout = setTimeout(() => {
+        killChild()
         settle(() => rejectPromise(timeoutError))
       }, timeoutMs)
 
+      const onAbort = (): void => {
+        killChild()
+        settle(() => rejectPromise(cancelError))
+      }
       const onError = (error: Error): void => {
         settle(() => rejectPromise(error))
       }
@@ -952,6 +1001,11 @@ export class ClaudeAccountService {
       child.stderr.on('data', appendOutput)
       child.on('error', onError)
       child.on('close', onClose)
+      if (options?.signal?.aborted) {
+        onAbort()
+      } else {
+        options?.signal?.addEventListener('abort', onAbort, { once: true })
+      }
     })
   }
 
diff --git a/src/main/ipc/claude-accounts.ts b/src/main/ipc/claude-accounts.ts
index 2fbaff81e..f88f094e4 100644
--- a/src/main/ipc/claude-accounts.ts
+++ b/src/main/ipc/claude-accounts.ts
@@ -7,6 +7,7 @@ export function registerClaudeAccountHandlers(claudeAccounts: ClaudeAccountServi
   ipcMain.handle('claudeAccounts:add', (_event, args?: ClaudeAccountAddTarget) =>
     claudeAccounts.addAccount(args)
   )
+  ipcMain.handle('claudeAccounts:cancelPendingLogin', () => claudeAccounts.cancelPendingLogin())
   ipcMain.handle('claudeAccounts:reauthenticate', (_event, args: { accountId: string }) =>
     claudeAccounts.reauthenticateAccount(args.accountId)
   )
diff --git a/src/preload/api-types.ts b/src/preload/api-types.ts
index 75b2d1cd0..a2cd5b511 100644
--- a/src/preload/api-types.ts
+++ b/src/preload/api-types.ts
@@ -1901,6 +1901,7 @@ export type PreloadApi = {
       runtime?: 'host' | 'wsl'
       wslDistro?: string | null
     }) => Promise<ClaudeRateLimitAccountsState>
+    cancelPendingLogin: () => Promise<boolean>
     reauthenticate: (args: { accountId: string }) => Promise<ClaudeRateLimitAccountsState>
     remove: (args: { accountId: string }) => Promise<ClaudeRateLimitAccountsState>
     select: (args: {
diff --git a/src/preload/index.ts b/src/preload/index.ts
index e6c7a3079..6e4bb9884 100644
--- a/src/preload/index.ts
+++ b/src/preload/index.ts
@@ -1705,6 +1705,8 @@ const api = {
     list: (): Promise<unknown> => ipcRenderer.invoke('claudeAccounts:list'),
     add: (args?: { runtime?: 'host' | 'wsl'; wslDistro?: string | null }): Promise<unknown> =>
       ipcRenderer.invoke('claudeAccounts:add', args),
+    cancelPendingLogin: (): Promise<boolean> =>
+      ipcRenderer.invoke('claudeAccounts:cancelPendingLogin'),
     reauthenticate: (args: { accountId: string }): Promise<unknown> =>
       ipcRenderer.invoke('claudeAccounts:reauthenticate', args),
     remove: (args: { accountId: string }): Promise<unknown> =>
diff --git a/src/renderer/src/components/settings/AccountsPane.tsx b/src/renderer/src/components/settings/AccountsPane.tsx
index 35540a2b8..947ec64c2 100644
--- a/src/renderer/src/components/settings/AccountsPane.tsx
+++ b/src/renderer/src/components/settings/AccountsPane.tsx
@@ -15,7 +15,7 @@ import { Input } from '../ui/input'
 import { Label } from '../ui/label'
 import { Separator } from '../ui/separator'
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '../ui/select'
-import { AlertTriangle, Loader2, Plus, RefreshCw, Trash2 } from 'lucide-react'
+import { AlertTriangle, Loader2, Plus, RefreshCw, Trash2, X } from 'lucide-react'
 import { useAppStore } from '../../store'
 import { ClaudeIcon, GeminiIcon, OpenAIIcon, OpenCodeGoIcon } from '../status-bar/icons'
 import { toast } from 'sonner'
@@ -183,6 +183,10 @@ function getClaudeAccountErrorDescription(error: unknown): string {
   )
 }
 
+function isClaudeAccountCancellation(error: unknown): boolean {
+  return getClaudeAccountErrorDescription(error).toLowerCase() === 'claude sign-in was cancelled.'
+}
+
 type LocalAccountRuntime = {
   runtime: 'host' | 'wsl'
   wslDistro?: string | null
@@ -550,6 +554,9 @@ export function AccountsPane({
         )
       }
     } catch (error) {
+      if (isClaudeAccountCancellation(error)) {
+        return
+      }
       toast.error(
         translate(
           'auto.components.settings.AccountsPane.2743cdc0af',
@@ -608,29 +615,42 @@ export function AccountsPane({
                 )}
               </p>
             </div>
-            <Button
-              variant="outline"
-              size="xs"
-              onClick={() =>
-                void runClaudeAccountAction('adding', () =>
-                  window.api.claudeAccounts.add({
-                    runtime: accountRuntime.runtime,
-                    wslDistro: accountRuntime.wslDistro
-                  })
-                )
-              }
-              disabled={
-                claudeAction !== 'idle' || wslCapabilitiesLoading || accountRuntimeUnavailable
-              }
-              className="gap-1.5"
-            >
+            <div className="flex shrink-0 items-center gap-1.5">
+              <Button
+                variant="outline"
+                size="xs"
+                onClick={() =>
+                  void runClaudeAccountAction('adding', () =>
+                    window.api.claudeAccounts.add({
+                      runtime: accountRuntime.runtime,
+                      wslDistro: accountRuntime.wslDistro
+                    })
+                  )
+                }
+                disabled={
+                  claudeAction !== 'idle' || wslCapabilitiesLoading || accountRuntimeUnavailable
+                }
+                className="gap-1.5"
+              >
+                {claudeAction === 'adding' ? (
+                  <Loader2 className="size-3 animate-spin" />
+                ) : (
+                  <Plus className="size-3" />
+                )}
+                {translate('auto.components.settings.AccountsPane.b0e948a4f9', 'Add Account')}
+              </Button>
               {claudeAction === 'adding' ? (
-                <Loader2 className="size-3 animate-spin" />
-              ) : (
-                <Plus className="size-3" />
-              )}
-              {translate('auto.components.settings.AccountsPane.b0e948a4f9', 'Add Account')}
-            </Button>
+                <Button
+                  variant="ghost"
+                  size="xs"
+                  onClick={() => void window.api.claudeAccounts.cancelPendingLogin()}
+                  className="gap-1.5 text-muted-foreground hover:text-foreground"
+                >
+                  <X className="size-3" />
+                  {translate('auto.components.settings.AccountsPane.dbb9626ed1', 'Cancel')}
+                </Button>
+              ) : null}
+            </div>
           </div>
 
           <div className="space-y-2">
diff --git a/src/renderer/src/web/web-preload-api.ts b/src/renderer/src/web/web-preload-api.ts
index 8334318cf..22ddb9a81 100644
--- a/src/renderer/src/web/web-preload-api.ts
+++ b/src/renderer/src/web/web-preload-api.ts
@@ -2470,6 +2470,7 @@ function createAccountsApi(): never {
   return {
     list: () => Promise.resolve(empty),
     add: () => Promise.resolve(empty),
+    cancelPendingLogin: () => Promise.resolve(false),
     reauthenticate: () => Promise.resolve(empty),
     remove: () => Promise.resolve(empty),
     select: () => Promise.resolve(empty)