diff --git a/src/components/PromptInput/useSwarmBanner.ts b/src/components/PromptInput/useSwarmBanner.ts
index 18feb0503..93512f9b1 100644
--- a/src/components/PromptInput/useSwarmBanner.ts
+++ b/src/components/PromptInput/useSwarmBanner.ts
@@ -81,11 +81,17 @@ export function useSwarmBanner(): SwarmBannerInfo {
     const viewedTeammate = getViewedTeammateTask(state)
     const viewedColor = toThemeColor(viewedTeammate?.identity.color)
     const inProcessMode = isInProcessEnabled()
-    const nativePanes = getCachedDetectionResult()?.isNative ?? false
+    const detection = getCachedDetectionResult()
+    const nativePanes = detection?.isNative ?? false
+    const backendType = detection?.backend.type
 
     if (insideTmux === false && !inProcessMode && !nativePanes) {
+      const hint =
+        backendType === 'windows-terminal'
+          ? 'View teammates in the Windows Terminal tabs spawned for each teammate'
+          : `View teammates: \`tmux -L ${getSwarmSocketName()} a\``
       return {
-        text: `View teammates: \`tmux -L ${getSwarmSocketName()} a\``,
+        text: hint,
         bgColor: viewedColor,
       }
     }
diff --git a/src/utils/agentSwarmsEnabled.ts b/src/utils/agentSwarmsEnabled.ts
index fac5404c7..f349a8c75 100644
--- a/src/utils/agentSwarmsEnabled.ts
+++ b/src/utils/agentSwarmsEnabled.ts
@@ -1,42 +1,15 @@
-import { getFeatureValue_CACHED_MAY_BE_STALE } from '../services/analytics/growthbook.js'
 import { isEnvTruthy } from './envUtils.js'
 
-/**
- * Check if --agent-teams flag is provided via CLI.
- * Checks process.argv directly to avoid import cycles with bootstrap/state.
- * Note: The flag is only shown in help for ant users, but if external users
- * pass it anyway, it will work (subject to the killswitch).
- */
-function isAgentTeamsFlagSet(): boolean {
-  return process.argv.includes('--agent-teams')
-}
-
 /**
  * Centralized runtime check for agent teams/teammate features.
  * This is the single gate that should be checked everywhere teammates
  * are referenced (prompts, code, tools isEnabled, UI, etc.).
  *
- * Ant builds: always enabled.
- * External builds require both:
- * 1. Opt-in via CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS env var OR --agent-teams flag
- * 2. GrowthBook gate 'tengu_amber_flint' enabled (killswitch)
+ * Fork build: enabled by default. Can be disabled via
+ * CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=0 if needed.
  */
 export function isAgentSwarmsEnabled(): boolean {
-  // Ant: always on
-  if (process.env.USER_TYPE === 'ant') {
-    return true
-  }
-
-  // External: require opt-in via env var or --agent-teams flag
-  if (
-    !isEnvTruthy(process.env.CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS) &&
-    !isAgentTeamsFlagSet()
-  ) {
-    return false
-  }
-
-  // Killswitch — always respected for external users
-  if (!getFeatureValue_CACHED_MAY_BE_STALE('tengu_amber_flint', true)) {
+  if (isEnvTruthy(process.env.CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS_DISABLED)) {
     return false
   }
 
diff --git a/src/utils/swarm/__tests__/agentTeamsLifecycle.test.ts b/src/utils/swarm/__tests__/agentTeamsLifecycle.test.ts
new file mode 100644
index 000000000..2bc5dbb70
--- /dev/null
+++ b/src/utils/swarm/__tests__/agentTeamsLifecycle.test.ts
@@ -0,0 +1,279 @@
+import { afterEach, beforeEach, describe, expect, mock, test } from 'bun:test'
+import { mkdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+
+let terminateCalls: string[] = []
+
+mock.module('src/utils/swarm/backends/registry.js', () => {
+  const executor = {
+    type: 'in-process' as const,
+    setContext() {},
+    async isAvailable() {
+      return true
+    },
+    async spawn(config: { name: string; teamName: string; color?: string }) {
+      return {
+        success: true,
+        agentId: `${config.name}@${config.teamName}`,
+        taskId: `task-${config.name}`,
+        backendType: 'in-process',
+        color: config.color,
+        isSplitPane: false,
+      }
+    },
+    async sendMessage() {},
+    async terminate(agentId: string) {
+      terminateCalls.push(agentId)
+      return true
+    },
+    async kill() {
+      return true
+    },
+    async isActive() {
+      return true
+    },
+  }
+
+  return {
+    getTeammateExecutor: async () => executor,
+    getInProcessBackend: () => executor,
+    detectAndGetBackend: async () => ({
+      backend: { type: 'in-process' },
+      isNative: false,
+      needsIt2Setup: false,
+    }),
+    isInProcessEnabled: () => true,
+    markInProcessFallback: () => {},
+    resetBackendDetection: () => {},
+    getCachedBackend: () => null,
+    getCachedDetectionResult: () => null,
+    getResolvedTeammateMode: () => 'in-process',
+    ensureBackendsRegistered: async () => {},
+    getBackendByType: () => ({
+      type: 'tmux',
+      killPane: async () => true,
+    }),
+  }
+})
+
+let tempHome: string
+let previousConfigDir: string | undefined
+let previousAnthropicApiKey: string | undefined
+let state: any
+
+function setState(updater: (prev: any) => any): void {
+  state = updater(state)
+}
+
+function readTeamConfig(teamName: string): any {
+  return JSON.parse(
+    readFileSync(join(tempHome, 'teams', teamName, 'config.json'), 'utf-8'),
+  )
+}
+
+function writeTeamConfig(teamName: string, config: unknown): void {
+  const teamDir = join(tempHome, 'teams', teamName)
+  mkdirSync(teamDir, { recursive: true })
+  writeFileSync(join(teamDir, 'config.json'), JSON.stringify(config, null, 2))
+}
+
+beforeEach(() => {
+  terminateCalls = []
+  previousConfigDir = process.env.CLAUDE_CONFIG_DIR
+  previousAnthropicApiKey = process.env.ANTHROPIC_API_KEY
+  tempHome = join(
+    tmpdir(),
+    `agent-teams-lifecycle-${Date.now()}-${Math.random().toString(16).slice(2)}`,
+  )
+  process.env.CLAUDE_CONFIG_DIR = tempHome
+  process.env.ANTHROPIC_API_KEY = 'test-key'
+  state = {
+    teamContext: undefined,
+    tasks: {},
+    inbox: { messages: [] },
+    toolPermissionContext: {
+      mode: 'default',
+      alwaysAllowRules: {},
+      alwaysDenyRules: {},
+      additionalWorkingDirectories: new Map(),
+    },
+    mainLoopModel: null,
+    mainLoopModelForSession: null,
+    agentNameRegistry: new Map(),
+    mcp: { tools: [] },
+  }
+})
+
+afterEach(() => {
+  if (previousConfigDir === undefined) {
+    delete process.env.CLAUDE_CONFIG_DIR
+  } else {
+    process.env.CLAUDE_CONFIG_DIR = previousConfigDir
+  }
+  if (previousAnthropicApiKey === undefined) {
+    delete process.env.ANTHROPIC_API_KEY
+  } else {
+    process.env.ANTHROPIC_API_KEY = previousAnthropicApiKey
+  }
+  rmSync(tempHome, { recursive: true, force: true })
+})
+
+describe('Agent Teams lifecycle', () => {
+  test('runs TeamCreate -> spawn -> TaskUpdate -> SendMessage -> TeamDelete', async () => {
+    const { TeamCreateTool } = await import(
+      '@claude-code-best/builtin-tools/tools/TeamCreateTool/TeamCreateTool.js'
+    )
+    const { spawnTeammate } = await import(
+      '@claude-code-best/builtin-tools/tools/shared/spawnMultiAgent.js'
+    )
+    const { TaskCreateTool } = await import(
+      '@claude-code-best/builtin-tools/tools/TaskCreateTool/TaskCreateTool.js'
+    )
+    const { TaskUpdateTool } = await import(
+      '@claude-code-best/builtin-tools/tools/TaskUpdateTool/TaskUpdateTool.js'
+    )
+    const { SendMessageTool } = await import(
+      '@claude-code-best/builtin-tools/tools/SendMessageTool/SendMessageTool.js'
+    )
+    const { TeamDeleteTool } = await import(
+      '@claude-code-best/builtin-tools/tools/TeamDeleteTool/TeamDeleteTool.js'
+    )
+
+    const context = {
+      getAppState: () => state,
+      setAppState: setState,
+      options: {
+        agentDefinitions: { activeAgents: [] },
+      },
+      abortController: new AbortController(),
+    } as any
+
+    const created = await TeamCreateTool.call(
+      { team_name: 'alpha', description: 'test team' },
+      context,
+      undefined as any,
+      undefined as any,
+    )
+    expect(created.data.team_name).toBe('alpha')
+
+    const spawned = await spawnTeammate(
+      {
+        name: 'worker',
+        prompt: 'handle assigned tasks',
+        team_name: 'alpha',
+      },
+      context,
+    )
+    expect(spawned.data.agent_id).toBe('worker@alpha')
+
+    const task = await TaskCreateTool.call(
+      { subject: 'Check lifecycle', description: 'Verify team task flow' },
+      context,
+    )
+    await TaskUpdateTool.call(
+      { taskId: task.data.task.id, owner: 'worker' },
+      context,
+    )
+
+    const message = await SendMessageTool.call(
+      {
+        to: 'worker',
+        summary: 'Status request',
+        message: 'Please report status.',
+      },
+      context,
+      async () => ({ behavior: 'allow' as const }),
+      undefined as any,
+    )
+    expect(message.data.success).toBe(true)
+
+    const blockedDelete = await TeamDeleteTool.call(
+      {},
+      context,
+      undefined as any,
+      undefined as any,
+    )
+    expect(blockedDelete.data.success).toBe(false)
+    expect(terminateCalls).toEqual(['worker@alpha'])
+
+    const config = readTeamConfig('alpha')
+    config.members = config.members.map((member: any) =>
+      member.name === 'worker' ? { ...member, isActive: false } : member,
+    )
+    writeTeamConfig('alpha', config)
+
+    const deleted = await TeamDeleteTool.call(
+      {},
+      context,
+      undefined as any,
+      undefined as any,
+    )
+    expect(deleted.data.success).toBe(true)
+  })
+
+  test('TeamDelete waits for active teammates to become inactive before cleanup', async () => {
+    const { TeamDeleteTool } = await import(
+      '@claude-code-best/builtin-tools/tools/TeamDeleteTool/TeamDeleteTool.js'
+    )
+    const now = Date.now()
+    writeTeamConfig('alpha', {
+      name: 'alpha',
+      createdAt: now,
+      leadAgentId: 'team-lead@alpha',
+      members: [
+        {
+          agentId: 'team-lead@alpha',
+          name: 'team-lead',
+          joinedAt: now,
+          tmuxPaneId: '',
+          cwd: tempHome,
+          subscriptions: [],
+        },
+        {
+          agentId: 'worker@alpha',
+          name: 'worker',
+          joinedAt: now,
+          tmuxPaneId: 'in-process',
+          cwd: tempHome,
+          subscriptions: [],
+          backendType: 'in-process',
+        },
+      ],
+    })
+    state.teamContext = {
+      teamName: 'alpha',
+      teamFilePath: join(tempHome, 'teams', 'alpha', 'config.json'),
+      leadAgentId: 'team-lead@alpha',
+      teammates: {
+        'worker@alpha': {
+          name: 'worker',
+          tmuxSessionName: 'in-process',
+          tmuxPaneId: 'in-process',
+          cwd: tempHome,
+          spawnedAt: now,
+        },
+      },
+    }
+
+    setTimeout(() => {
+      const config = readTeamConfig('alpha')
+      config.members = config.members.map((member: any) =>
+        member.name === 'worker' ? { ...member, isActive: false } : member,
+      )
+      writeTeamConfig('alpha', config)
+    }, 25)
+
+    const result = await TeamDeleteTool.call(
+      { wait_ms: 1000 },
+      {
+        getAppState: () => state,
+        setAppState: setState,
+      } as any,
+      undefined as any,
+      undefined as any,
+    )
+
+    expect(result.data.success).toBe(true)
+  })
+})
diff --git a/src/utils/swarm/__tests__/spawnInProcess.test.ts b/src/utils/swarm/__tests__/spawnInProcess.test.ts
new file mode 100644
index 000000000..2e30f354a
--- /dev/null
+++ b/src/utils/swarm/__tests__/spawnInProcess.test.ts
@@ -0,0 +1,115 @@
+import { afterEach, beforeEach, describe, expect, test } from 'bun:test'
+import { rmSync } from 'fs'
+import { tmpdir } from 'os'
+import { join } from 'path'
+import { getDefaultAppState } from '../../../state/AppStateStore'
+import { readMailbox, writeToMailbox } from '../../teammateMailbox'
+import {
+  killInProcessTeammateByAgentId,
+  spawnInProcessTeammate,
+} from '../spawnInProcess'
+
+let tempHome: string
+let previousConfigDir: string | undefined
+
+beforeEach(() => {
+  previousConfigDir = process.env.CLAUDE_CONFIG_DIR
+  tempHome = join(
+    tmpdir(),
+    `spawn-in-process-${Date.now()}-${Math.random().toString(16).slice(2)}`,
+  )
+  process.env.CLAUDE_CONFIG_DIR = tempHome
+})
+
+afterEach(() => {
+  if (previousConfigDir === undefined) {
+    delete process.env.CLAUDE_CONFIG_DIR
+  } else {
+    process.env.CLAUDE_CONFIG_DIR = previousConfigDir
+  }
+  rmSync(tempHome, { recursive: true, force: true })
+})
+
+describe('killInProcessTeammateByAgentId', () => {
+  test('registers a real in-process teammate task and mailbox', async () => {
+    let state = getDefaultAppState() as any
+    const result = await spawnInProcessTeammate(
+      {
+        name: 'worker',
+        teamName: 'alpha',
+        prompt: 'smoke test task',
+        color: 'blue',
+        planModeRequired: false,
+      },
+      {
+        setAppState(updater) {
+          state = updater(state)
+        },
+        toolUseId: 'toolu_smoke',
+      },
+    )
+
+    expect(result.success).toBe(true)
+    expect(result.agentId).toBe('worker@alpha')
+    expect(result.taskId).toBeString()
+    expect(state.tasks[result.taskId!].type).toBe('in_process_teammate')
+    expect(state.tasks[result.taskId!].identity.agentId).toBe('worker@alpha')
+    expect(state.tasks[result.taskId!].messages).toEqual([])
+
+    await writeToMailbox(
+      'worker',
+      {
+        from: 'team-lead',
+        text: 'mailbox smoke',
+        timestamp: new Date(0).toISOString(),
+      },
+      'alpha',
+    )
+    const messages = await readMailbox('worker', 'alpha')
+
+    expect(messages).toHaveLength(1)
+    expect(messages[0]!.text).toBe('mailbox smoke')
+    expect(messages[0]!.read).toBe(false)
+  })
+
+  test('aborts the running teammate and removes it from team context by agent id', () => {
+    const abortController = new AbortController()
+    let state: any = {
+      teamContext: {
+        teamName: 'alpha',
+        teammates: {
+          'worker@alpha': {
+            name: 'worker',
+          },
+        },
+      },
+      tasks: {
+        teammate_task_1: {
+          id: 'teammate_task_1',
+          type: 'in_process_teammate',
+          status: 'running',
+          identity: {
+            agentId: 'worker@alpha',
+            agentName: 'worker',
+            teamName: 'alpha',
+            planModeRequired: false,
+            parentSessionId: 'session',
+          },
+          abortController,
+          pendingUserMessages: [],
+          onIdleCallbacks: [],
+          messages: [],
+        },
+      },
+    }
+
+    const killed = killInProcessTeammateByAgentId('worker@alpha', updater => {
+      state = updater(state)
+    })
+
+    expect(killed).toBe(true)
+    expect(abortController.signal.aborted).toBe(true)
+    expect(state.tasks.teammate_task_1.status).toBe('killed')
+    expect(state.teamContext.teammates['worker@alpha']).toBeUndefined()
+  })
+})
diff --git a/src/utils/swarm/__tests__/spawnUtils.test.ts b/src/utils/swarm/__tests__/spawnUtils.test.ts
new file mode 100644
index 000000000..2dde21f14
--- /dev/null
+++ b/src/utils/swarm/__tests__/spawnUtils.test.ts
@@ -0,0 +1,10 @@
+import { describe, expect, test } from 'bun:test'
+import { buildInheritedCliFlags } from '../spawnUtils'
+
+describe('buildInheritedCliFlags', () => {
+  test('propagates auto permission mode to process-based teammates', () => {
+    const flags = buildInheritedCliFlags({ permissionMode: 'auto' })
+
+    expect(flags).toContain('--permission-mode auto')
+  })
+})
diff --git a/src/utils/swarm/backends/InProcessBackend.ts b/src/utils/swarm/backends/InProcessBackend.ts
index 0f43f81fe..6bd96133b 100644
--- a/src/utils/swarm/backends/InProcessBackend.ts
+++ b/src/utils/swarm/backends/InProcessBackend.ts
@@ -91,6 +91,7 @@ export class InProcessBackend implements TeammateExecutor {
         prompt: config.prompt,
         color: config.color,
         planModeRequired: config.planModeRequired ?? false,
+        model: config.model,
       },
       this.context,
     )
@@ -115,6 +116,8 @@ export class InProcessBackend implements TeammateExecutor {
         },
         taskId: result.taskId,
         prompt: config.prompt,
+        description: config.description,
+        agentDefinition: config.agentDefinition,
         teammateContext: result.teammateContext,
         // Strip messages: the teammate never reads toolUseContext.messages
         // (runAgent overrides it via createSubagentContext). Passing the
@@ -126,6 +129,7 @@ export class InProcessBackend implements TeammateExecutor {
         systemPromptMode: config.systemPromptMode,
         allowedTools: config.permissions,
         allowPermissionPrompts: config.allowPermissionPrompts,
+        invokingRequestId: config.invokingRequestId,
       })
 
       logForDebugging(
@@ -138,6 +142,8 @@ export class InProcessBackend implements TeammateExecutor {
       agentId: result.agentId,
       taskId: result.taskId,
       abortController: result.abortController,
+      backendType: this.type,
+      color: config.color,
       error: result.error,
     }
   }
diff --git a/src/utils/swarm/backends/PaneBackendExecutor.ts b/src/utils/swarm/backends/PaneBackendExecutor.ts
index a978e032c..e1436a71d 100644
--- a/src/utils/swarm/backends/PaneBackendExecutor.ts
+++ b/src/utils/swarm/backends/PaneBackendExecutor.ts
@@ -2,13 +2,15 @@ import { getSessionId } from '../../../bootstrap/state.js'
 import type { ToolUseContext } from '../../../Tool.js'
 import { formatAgentId, parseAgentId } from '../../../utils/agentId.js'
 import { quote } from '../../../utils/bash/shellQuote.js'
+import { isInBundledMode } from '../../../utils/bundledMode.js'
 import { registerCleanup } from '../../../utils/cleanupRegistry.js'
 import { logForDebugging } from '../../../utils/debug.js'
 import { jsonStringify } from '../../../utils/slowOperations.js'
 import { writeToMailbox } from '../../../utils/teammateMailbox.js'
 import {
-  buildInheritedCliFlags,
+  buildInheritedCliArgParts,
   buildInheritedEnvVars,
+  getInheritedEnvVarAssignments,
   getTeammateCommand,
 } from '../spawnUtils.js'
 import { assignTeammateColor } from '../teammateLayoutManager.js'
@@ -22,6 +24,43 @@ import type {
   TeammateSpawnResult,
 } from './types.js'
 
+function quotePowerShellString(value: string): string {
+  return `'${value.replace(/'/g, "''")}'`
+}
+
+function withoutModelArg(args: string[]): string[] {
+  const filtered: string[] = []
+  for (let i = 0; i < args.length; i += 1) {
+    if (args[i] === '--model') {
+      i += 1
+      continue
+    }
+    filtered.push(args[i]!)
+  }
+  return filtered
+}
+
+function buildPowerShellSpawnCommand(
+  binaryPath: string,
+  args: string[],
+  cwd: string,
+): string {
+  const envAssignments = getInheritedEnvVarAssignments().map(
+    ([key, value]) => `$env:${key} = ${quotePowerShellString(value)}`,
+  )
+  // In dev mode (non-bundled), binaryPath is a .ts/.tsx file that PowerShell
+  // cannot execute directly. Prepend `bun run` so the teammate process starts
+  // through Bun's runtime, matching how `bun run dev` works.
+  const invocation = isInBundledMode()
+    ? `& ${quotePowerShellString(binaryPath)}`
+    : `& ${quotePowerShellString(process.execPath)} ${quotePowerShellString(binaryPath)}`
+  return [
+    `Set-Location -LiteralPath ${quotePowerShellString(cwd)}`,
+    ...envAssignments,
+    `${invocation} ${args.map(quotePowerShellString).join(' ')}`,
+  ].join('; ')
+}
+
 /**
  * PaneBackendExecutor adapts a PaneBackend to the TeammateExecutor interface.
  *
@@ -95,12 +134,18 @@ export class PaneBackendExecutor implements TeammateExecutor {
       // Assign a unique color to this teammate
       const teammateColor = config.color ?? assignTeammateColor(agentId)
 
-      // Create a pane in the swarm view
-      const { paneId, isFirstTeammate } =
-        await this.backend.createTeammatePaneInSwarmView(
-          config.name,
-          teammateColor,
-        )
+      const paneResult =
+        config.useSplitPane === false &&
+        this.backend.createTeammateWindowInSwarmView
+          ? await this.backend.createTeammateWindowInSwarmView(
+              config.name,
+              teammateColor,
+            )
+          : await this.backend.createTeammatePaneInSwarmView(
+              config.name,
+              teammateColor,
+            )
+      const { paneId, isFirstTeammate } = paneResult
 
       // Check if we're inside tmux to determine how to send commands
       const insideTmux = await isInsideTmux()
@@ -115,43 +160,43 @@ export class PaneBackendExecutor implements TeammateExecutor {
 
       // Build teammate identity CLI args
       const teammateArgs = [
-        `--agent-id ${quote([agentId])}`,
-        `--agent-name ${quote([config.name])}`,
-        `--team-name ${quote([config.teamName])}`,
-        `--agent-color ${quote([teammateColor])}`,
-        `--parent-session-id ${quote([config.parentSessionId || getSessionId()])}`,
-        config.planModeRequired ? '--plan-mode-required' : '',
+        '--agent-id',
+        agentId,
+        '--agent-name',
+        config.name,
+        '--team-name',
+        config.teamName,
+        '--agent-color',
+        teammateColor,
+        '--parent-session-id',
+        config.parentSessionId || getSessionId(),
+        ...(config.planModeRequired ? ['--plan-mode-required'] : []),
+        ...(config.agentType ? ['--agent-type', config.agentType] : []),
       ]
-        .filter(Boolean)
-        .join(' ')
 
       // Build CLI flags to propagate to teammate
       const appState = this.context.getAppState()
-      let inheritedFlags = buildInheritedCliFlags({
+      let inheritedArgParts = buildInheritedCliArgParts({
         planModeRequired: config.planModeRequired,
         permissionMode: appState.toolPermissionContext.mode,
       })
 
       // If teammate has a custom model, add --model flag (or replace inherited one)
       if (config.model) {
-        inheritedFlags = inheritedFlags
-          .split(' ')
-          .filter(
-            (flag, i, arr) => flag !== '--model' && arr[i - 1] !== '--model',
-          )
-          .join(' ')
-        inheritedFlags = inheritedFlags
-          ? `${inheritedFlags} --model ${quote([config.model])}`
-          : `--model ${quote([config.model])}`
+        inheritedArgParts = withoutModelArg(inheritedArgParts)
+        inheritedArgParts.push('--model', config.model)
       }
 
-      const flagsStr = inheritedFlags ? ` ${inheritedFlags}` : ''
       const workingDir = config.cwd
 
       // Build environment variables to forward to teammate
       const envStr = buildInheritedEnvVars()
 
-      const spawnCommand = `cd ${quote([workingDir])} && env ${envStr} ${quote([binaryPath])} ${teammateArgs}${flagsStr}`
+      const allArgs = [...teammateArgs, ...inheritedArgParts]
+      const spawnCommand =
+        this.type === 'windows-terminal'
+          ? buildPowerShellSpawnCommand(binaryPath, allArgs, workingDir)
+          : `cd ${quote([workingDir])} && env ${envStr} ${quote([binaryPath])} ${quote(allArgs)}`
 
       // Send the command to the new pane
       // Use swarm socket when running outside tmux (external swarm session)
@@ -193,6 +238,14 @@ export class PaneBackendExecutor implements TeammateExecutor {
         success: true,
         agentId,
         paneId,
+        backendType: this.type,
+        color: teammateColor,
+        insideTmux,
+        windowName:
+          'windowName' in paneResult
+            ? (paneResult as { windowName: string }).windowName
+            : undefined,
+        isSplitPane: config.useSplitPane !== false,
       }
     } catch (error) {
       const errorMessage =
diff --git a/src/utils/swarm/backends/TmuxBackend.ts b/src/utils/swarm/backends/TmuxBackend.ts
index 321958c7b..98c151fcd 100644
--- a/src/utils/swarm/backends/TmuxBackend.ts
+++ b/src/utils/swarm/backends/TmuxBackend.ts
@@ -145,6 +145,42 @@ export class TmuxBackend implements PaneBackend {
     }
   }
 
+  /**
+   * Creates a separate tmux window for a teammate in the swarm session.
+   * Used by the legacy `use_splitpane: false` path.
+   */
+  async createTeammateWindowInSwarmView(
+    name: string,
+    color: AgentColorName,
+  ): Promise<CreatePaneResult & { windowName: string }> {
+    const windowName = `teammate-${name.replace(/[^a-zA-Z0-9]/g, '-').toLowerCase()}`
+    const { windowTarget } = await this.createExternalSwarmSession()
+    void windowTarget
+
+    const result = await runTmuxInSwarm([
+      'new-window',
+      '-t',
+      SWARM_SESSION_NAME,
+      '-n',
+      windowName,
+      '-P',
+      '-F',
+      '#{pane_id}',
+    ])
+
+    if (result.code !== 0) {
+      throw new Error(
+        `Failed to create tmux window: ${result.stderr || 'Unknown error'}`,
+      )
+    }
+
+    const paneId = result.stdout.trim()
+    await this.setPaneTitle(paneId, name, color, true)
+    await this.setPaneBorderColor(paneId, color, true)
+
+    return { paneId, isFirstTeammate: false, windowName }
+  }
+
   /**
    * Sends a command to a specific pane.
    */
diff --git a/src/utils/swarm/backends/WindowsTerminalBackend.ts b/src/utils/swarm/backends/WindowsTerminalBackend.ts
new file mode 100644
index 000000000..b0e45e312
--- /dev/null
+++ b/src/utils/swarm/backends/WindowsTerminalBackend.ts
@@ -0,0 +1,237 @@
+import { randomUUID } from 'crypto'
+import { readFile } from 'fs/promises'
+import { join } from 'path'
+import { tmpdir } from 'os'
+import type { AgentColorName } from '@claude-code-best/builtin-tools/tools/AgentTool/agentColorManager.js'
+import { logForDebugging } from '../../../utils/debug.js'
+import { execFileNoThrow } from '../../../utils/execFileNoThrow.js'
+import { getPlatform, type Platform } from '../../../utils/platform.js'
+import { isInWindowsTerminal } from './detection.js'
+import { registerWindowsTerminalBackend } from './registry.js'
+import type { CreatePaneResult, PaneBackend, PaneId } from './types.js'
+
+type CommandResult = { stdout: string; stderr: string; code: number }
+type CommandRunner = (command: string, args: string[]) => Promise<CommandResult>
+
+type WindowsTerminalPane = {
+  title: string
+  mode: 'pane' | 'window'
+  pidFile: string
+}
+
+function quotePowerShellString(value: string): string {
+  return `'${value.replace(/'/g, "''")}'`
+}
+
+function wrapPowerShellCommand(command: string, pidFile: string): string {
+  const quotedPidFile = quotePowerShellString(pidFile)
+  // PowerShell requires try/catch/finally to be a single compound statement —
+  // semicolons between the blocks cause "Try 语句缺少自己的 Catch 或 Finally 块".
+  // Use newlines (\n) so the parser treats it as one statement.
+  return [
+    "$ErrorActionPreference = 'Stop'",
+    `Set-Content -LiteralPath ${quotedPidFile} -Value $PID`,
+    [
+      `try { ${command}; if ($LASTEXITCODE -is [int]) { exit $LASTEXITCODE } }`,
+      `catch { Write-Error $_; exit 1 }`,
+      `finally { Remove-Item -LiteralPath ${quotedPidFile} -Force -ErrorAction SilentlyContinue }`,
+    ].join('\n'),
+  ].join('; ')
+}
+
+function makePidFile(paneId: string): string {
+  return join(tmpdir(), `${paneId.replace(/[^a-zA-Z0-9_-]/g, '-')}.pid`)
+}
+
+/**
+ * WindowsTerminalBackend uses wt.exe to create visible teammate panes/tabs.
+ *
+ * Windows Terminal's CLI starts commands directly in a new pane; it does not
+ * expose a stable pane id that can later receive arbitrary input. To fit the
+ * PaneBackend contract, createTeammatePaneInSwarmView allocates an internal id,
+ * and sendCommandToPane performs the actual `wt split-pane` launch.
+ */
+export class WindowsTerminalBackend implements PaneBackend {
+  readonly type = 'windows-terminal' as const
+  readonly displayName = 'Windows Terminal'
+  readonly supportsHideShow = false
+
+  private panes = new Map<PaneId, WindowsTerminalPane>()
+
+  constructor(
+    private readonly runCommand: CommandRunner = execFileNoThrow,
+    private readonly getPlatformValue: () => Platform = getPlatform,
+  ) {}
+
+  async isAvailable(): Promise<boolean> {
+    if (this.getPlatformValue() !== 'windows') {
+      return false
+    }
+    // Do NOT run `wt.exe --version` — wt.exe is a UWP app bridge that opens
+    // the Windows Terminal app to render version info, producing a phantom
+    // "Windows 终端 1.24.x" window every time availability is checked.
+    // Instead, check the WT_SESSION env var (set inside WT) or verify the
+    // binary exists on PATH without executing it.
+    if (process.env.WT_SESSION) {
+      return true
+    }
+    const result = await this.runCommand('where.exe', ['wt.exe'])
+    return result.code === 0
+  }
+
+  async isRunningInside(): Promise<boolean> {
+    return this.getPlatformValue() === 'windows' && isInWindowsTerminal()
+  }
+
+  async createTeammatePaneInSwarmView(
+    name: string,
+    _color: AgentColorName,
+  ): Promise<CreatePaneResult> {
+    const paneId = `wt-${randomUUID()}`
+    const isFirstTeammate = this.panes.size === 0
+    this.panes.set(paneId, {
+      title: name,
+      mode: 'pane',
+      pidFile: makePidFile(paneId),
+    })
+    return { paneId, isFirstTeammate }
+  }
+
+  async createTeammateWindowInSwarmView(
+    name: string,
+    _color: AgentColorName,
+  ): Promise<CreatePaneResult & { windowName: string }> {
+    const paneId = `wt-${randomUUID()}`
+    const windowName = `teammate-${name.replace(/[^a-zA-Z0-9]/g, '-').toLowerCase()}`
+    this.panes.set(paneId, {
+      title: name,
+      mode: 'window',
+      pidFile: makePidFile(paneId),
+    })
+    return { paneId, isFirstTeammate: false, windowName }
+  }
+
+  async sendCommandToPane(
+    paneId: PaneId,
+    command: string,
+    _useExternalSession?: boolean,
+  ): Promise<void> {
+    const pane = this.panes.get(paneId)
+    if (!pane) {
+      throw new Error(`Unknown Windows Terminal pane id: ${paneId}`)
+    }
+
+    const launcher = wrapPowerShellCommand(command, pane.pidFile)
+    // wt.exe treats ';' as its own command separator, which breaks
+    // multi-statement PowerShell commands passed via -Command. Encode the
+    // entire script as Base64 UTF-16LE and use -EncodedCommand instead.
+    const encoded = Buffer.from(launcher, 'utf16le').toString('base64')
+    const args =
+      pane.mode === 'window'
+        ? ['-w', '-1', 'new-tab', '--title', pane.title]
+        : ['-w', '0', 'split-pane', '--vertical', '--title', pane.title]
+
+    const result = await this.runCommand('wt.exe', [
+      ...args,
+      'powershell.exe',
+      '-NoLogo',
+      '-NoProfile',
+      '-ExecutionPolicy',
+      'Bypass',
+      '-EncodedCommand',
+      encoded,
+    ])
+
+    if (result.code !== 0) {
+      throw new Error(
+        `Failed to launch Windows Terminal teammate ${paneId}: ${result.stderr}`,
+      )
+    }
+  }
+
+  async setPaneBorderColor(
+    _paneId: PaneId,
+    _color: AgentColorName,
+    _useExternalSession?: boolean,
+  ): Promise<void> {
+    // Windows Terminal does not expose per-pane border colors through wt.exe.
+  }
+
+  async setPaneTitle(
+    _paneId: PaneId,
+    _name: string,
+    _color: AgentColorName,
+    _useExternalSession?: boolean,
+  ): Promise<void> {
+    // Title is passed at launch in sendCommandToPane.
+  }
+
+  async enablePaneBorderStatus(
+    _windowTarget?: string,
+    _useExternalSession?: boolean,
+  ): Promise<void> {
+    // Not supported by Windows Terminal's wt.exe surface.
+  }
+
+  async rebalancePanes(
+    _windowTarget: string,
+    _hasLeader: boolean,
+  ): Promise<void> {
+    // Windows Terminal handles split layout itself.
+  }
+
+  async killPane(
+    paneId: PaneId,
+    _useExternalSession?: boolean,
+  ): Promise<boolean> {
+    const pane = this.panes.get(paneId)
+    if (!pane) {
+      return false
+    }
+
+    let pid: number
+    try {
+      pid = Number.parseInt((await readFile(pane.pidFile, 'utf-8')).trim(), 10)
+    } catch {
+      this.panes.delete(paneId)
+      return false
+    }
+
+    if (!Number.isFinite(pid)) {
+      this.panes.delete(paneId)
+      return false
+    }
+
+    const result = await this.runCommand('powershell.exe', [
+      '-NoLogo',
+      '-NoProfile',
+      '-Command',
+      `Stop-Process -Id ${pid} -Force -ErrorAction Stop`,
+    ])
+    this.panes.delete(paneId)
+    logForDebugging(
+      `[WindowsTerminalBackend] killPane ${paneId} pid=${pid} code=${result.code}`,
+    )
+    return result.code === 0
+  }
+
+  async hidePane(
+    _paneId: PaneId,
+    _useExternalSession?: boolean,
+  ): Promise<boolean> {
+    return false
+  }
+
+  async showPane(
+    _paneId: PaneId,
+    _targetWindowOrPane: string,
+    _useExternalSession?: boolean,
+  ): Promise<boolean> {
+    return false
+  }
+}
+
+// Register the backend with the registry when this module is imported.
+// This side effect is intentional - the registry needs backends to self-register.
+// eslint-disable-next-line custom-rules/no-top-level-side-effects
+registerWindowsTerminalBackend(WindowsTerminalBackend)
diff --git a/src/utils/swarm/backends/__tests__/PaneBackendExecutor.test.ts b/src/utils/swarm/backends/__tests__/PaneBackendExecutor.test.ts
new file mode 100644
index 000000000..2e95922a9
--- /dev/null
+++ b/src/utils/swarm/backends/__tests__/PaneBackendExecutor.test.ts
@@ -0,0 +1,155 @@
+import { afterEach, beforeEach, describe, expect, test } from 'bun:test'
+import { rmSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { createPaneBackendExecutor } from '../PaneBackendExecutor'
+import type { PaneBackend } from '../types'
+
+let tempHome: string
+let previousConfigDir: string | undefined
+
+beforeEach(() => {
+  previousConfigDir = process.env.CLAUDE_CONFIG_DIR
+  tempHome = join(
+    tmpdir(),
+    `pane-backend-executor-${Date.now()}-${Math.random().toString(16).slice(2)}`,
+  )
+  process.env.CLAUDE_CONFIG_DIR = tempHome
+})
+
+afterEach(() => {
+  if (previousConfigDir === undefined) {
+    delete process.env.CLAUDE_CONFIG_DIR
+  } else {
+    process.env.CLAUDE_CONFIG_DIR = previousConfigDir
+  }
+  rmSync(tempHome, { recursive: true, force: true })
+})
+
+describe('PaneBackendExecutor', () => {
+  test('spawns process teammates with agent type and inherited auto permission mode', async () => {
+    let sentCommand = ''
+    const backend: PaneBackend = {
+      type: 'tmux',
+      displayName: 'tmux',
+      supportsHideShow: true,
+      async isAvailable() {
+        return true
+      },
+      async isRunningInside() {
+        return false
+      },
+      async createTeammatePaneInSwarmView() {
+        return { paneId: '%1', isFirstTeammate: false }
+      },
+      async sendCommandToPane(_paneId, command) {
+        sentCommand = command
+      },
+      async setPaneBorderColor() {},
+      async setPaneTitle() {},
+      async enablePaneBorderStatus() {},
+      async rebalancePanes() {},
+      async killPane() {
+        return true
+      },
+      async hidePane() {
+        return true
+      },
+      async showPane() {
+        return true
+      },
+    }
+
+    const executor = createPaneBackendExecutor(backend)
+    executor.setContext({
+      getAppState: () => ({
+        toolPermissionContext: {
+          mode: 'auto',
+        },
+      }),
+    } as any)
+
+    const result = await executor.spawn({
+      name: 'reviewer',
+      teamName: 'alpha',
+      prompt: 'review the change',
+      cwd: tempHome,
+      parentSessionId: 'parent-session',
+      agentType: 'code-reviewer',
+      planModeRequired: false,
+    })
+
+    expect(result.success).toBe(true)
+    expect(result.backendType).toBe('tmux')
+    expect(result.paneId).toBe('%1')
+    expect(sentCommand).toContain('--agent-type code-reviewer')
+    expect(sentCommand).toContain('--permission-mode auto')
+  })
+
+  test('preserves legacy separate-window spawning when useSplitPane is false', async () => {
+    let paneSpawned = false
+    let windowSpawned = false
+    const backend: PaneBackend = {
+      type: 'tmux',
+      displayName: 'tmux',
+      supportsHideShow: true,
+      async isAvailable() {
+        return true
+      },
+      async isRunningInside() {
+        return false
+      },
+      async createTeammatePaneInSwarmView() {
+        paneSpawned = true
+        return { paneId: '%pane', isFirstTeammate: false }
+      },
+      async createTeammateWindowInSwarmView() {
+        windowSpawned = true
+        return {
+          paneId: '%window',
+          windowName: 'teammate-worker',
+          isFirstTeammate: false,
+        }
+      },
+      async sendCommandToPane() {},
+      async setPaneBorderColor() {},
+      async setPaneTitle() {},
+      async enablePaneBorderStatus() {},
+      async rebalancePanes() {},
+      async killPane() {
+        return true
+      },
+      async hidePane() {
+        return true
+      },
+      async showPane() {
+        return true
+      },
+    }
+
+    const executor = createPaneBackendExecutor(backend)
+    executor.setContext({
+      getAppState: () => ({
+        toolPermissionContext: {
+          mode: 'default',
+        },
+      }),
+    } as any)
+
+    const result = await executor.spawn({
+      name: 'worker',
+      teamName: 'alpha',
+      prompt: 'do work',
+      cwd: tempHome,
+      parentSessionId: 'parent-session',
+      useSplitPane: false,
+    })
+
+    expect(result.success).toBe(true)
+    expect(paneSpawned).toBe(false)
+    expect(windowSpawned).toBe(true)
+    expect(result.paneId).toBe('%window')
+    expect(result.windowName).toBe('teammate-worker')
+    expect(result.isSplitPane).toBe(false)
+  })
+})
diff --git a/src/utils/swarm/backends/__tests__/WindowsTerminalBackend.test.ts b/src/utils/swarm/backends/__tests__/WindowsTerminalBackend.test.ts
new file mode 100644
index 000000000..bd06effd4
--- /dev/null
+++ b/src/utils/swarm/backends/__tests__/WindowsTerminalBackend.test.ts
@@ -0,0 +1,102 @@
+import { mkdir, rm, writeFile } from 'fs/promises'
+import { tmpdir } from 'os'
+import { join } from 'path'
+import { beforeEach, afterEach, describe, expect, test } from 'bun:test'
+import { WindowsTerminalBackend } from '../WindowsTerminalBackend'
+
+type Call = { command: string; args: string[] }
+
+let tempDir: string
+
+beforeEach(async () => {
+  tempDir = join(
+    tmpdir(),
+    `windows-terminal-backend-${Date.now()}-${Math.random().toString(16).slice(2)}`,
+  )
+  await mkdir(tempDir, { recursive: true })
+})
+
+afterEach(async () => {
+  await rm(tempDir, { recursive: true, force: true })
+})
+
+function createBackend(calls: Call[]): WindowsTerminalBackend {
+  return new WindowsTerminalBackend(
+    async (command, args) => {
+      calls.push({ command, args })
+      return { stdout: 'ok', stderr: '', code: 0 }
+    },
+    () => 'windows',
+  )
+}
+
+function decodeEncodedCommand(call: Call): {
+  args: string[]
+  decodedLauncher: string
+} {
+  expect(call.command).toBe('wt.exe')
+  const encIdx = call.args.indexOf('-EncodedCommand')
+  expect(encIdx).toBeGreaterThanOrEqual(0)
+  const encoded = call.args[encIdx + 1]!
+  const decodedLauncher = Buffer.from(encoded, 'base64').toString('utf16le')
+  return { args: call.args, decodedLauncher }
+}
+
+describe('WindowsTerminalBackend', () => {
+  test('launches split panes through wt.exe with a wrapped PowerShell command', async () => {
+    const calls: Call[] = []
+    const backend = createBackend(calls)
+    const pane = await backend.createTeammatePaneInSwarmView('worker', 'blue')
+
+    await backend.sendCommandToPane(
+      pane.paneId,
+      "Set-Location -LiteralPath 'C:\\repo'; & 'claude.exe' '--agent-id' 'worker@alpha'",
+    )
+
+    expect(calls).toHaveLength(1)
+    const { args, decodedLauncher } = decodeEncodedCommand(calls[0]!)
+    expect(args).toContain('split-pane')
+    expect(args).toContain('--vertical')
+    expect(args).toContain('--title')
+    expect(args).toContain('worker')
+    expect(decodedLauncher).toContain('Set-Content -LiteralPath')
+    expect(decodedLauncher).toContain('claude.exe')
+  })
+
+  test('preserves use_splitpane false as a separate Windows Terminal window', async () => {
+    const calls: Call[] = []
+    const backend = createBackend(calls)
+    const pane = await backend.createTeammateWindowInSwarmView(
+      'reviewer',
+      'cyan',
+    )
+
+    await backend.sendCommandToPane(pane.paneId, "Write-Output 'hello'")
+
+    expect(pane.windowName).toBe('teammate-reviewer')
+    const { args } = decodeEncodedCommand(calls[0]!)
+    expect(args.join(' ')).toContain('-w -1 new-tab --title')
+  })
+
+  test('force kills the recorded teammate shell pid when available', async () => {
+    const calls: Call[] = []
+    const backend = createBackend(calls)
+    const pane = await backend.createTeammatePaneInSwarmView('killer', 'red')
+
+    await backend.sendCommandToPane(pane.paneId, "Write-Output 'running'")
+    const { decodedLauncher } = decodeEncodedCommand(calls[0]!)
+    const pidFile = decodedLauncher.match(
+      /Set-Content -LiteralPath '([^']+)'/,
+    )?.[1]
+    expect(pidFile).toBeString()
+    await writeFile(pidFile!, '12345', 'utf-8')
+
+    const killed = await backend.killPane(pane.paneId)
+
+    expect(killed).toBe(true)
+    expect(calls[calls.length - 1]!.command).toBe('powershell.exe')
+    expect(calls[calls.length - 1]!.args.join(' ')).toContain(
+      'Stop-Process -Id 12345',
+    )
+  })
+})
diff --git a/src/utils/swarm/backends/detection.ts b/src/utils/swarm/backends/detection.ts
index 4812fcd58..be45b2aa7 100644
--- a/src/utils/swarm/backends/detection.ts
+++ b/src/utils/swarm/backends/detection.ts
@@ -24,6 +24,9 @@ let isInsideTmuxCached: boolean | null = null
 /** Cached result for isInITerm2 */
 let isInITerm2Cached: boolean | null = null
 
+/** Cached result for isInWindowsTerminal */
+let isInWindowsTerminalCached: boolean | null = null
+
 /**
  * Checks if we're currently running inside a tmux session (synchronous version).
  * Uses the original TMUX value captured at module load, not process.env.TMUX,
@@ -75,6 +78,20 @@ export async function isTmuxAvailable(): Promise<boolean> {
   return result.code === 0
 }
 
+/**
+ * Checks if wt.exe is available without executing it.
+ * Do NOT run `wt.exe --version` — wt.exe is a UWP app bridge that opens
+ * the Windows Terminal GUI to render version info, producing a phantom
+ * "Windows 终端 1.24.x" window every time availability is checked.
+ */
+export async function isWindowsTerminalAvailable(): Promise<boolean> {
+  if (process.env.WT_SESSION) {
+    return true
+  }
+  const result = await execFileNoThrow('where.exe', ['wt.exe'])
+  return result.code === 0
+}
+
 /**
  * Checks if we're currently running inside iTerm2.
  * Uses multiple detection methods:
@@ -103,6 +120,18 @@ export function isInITerm2(): boolean {
   return isInITerm2Cached
 }
 
+/**
+ * Checks if we're currently running inside Windows Terminal.
+ * Windows Terminal sets WT_SESSION for child processes.
+ */
+export function isInWindowsTerminal(): boolean {
+  if (isInWindowsTerminalCached !== null) {
+    return isInWindowsTerminalCached
+  }
+  isInWindowsTerminalCached = !!process.env.WT_SESSION
+  return isInWindowsTerminalCached
+}
+
 /**
  * The it2 CLI command name.
  */
@@ -125,4 +154,5 @@ export async function isIt2CliAvailable(): Promise<boolean> {
 export function resetDetectionCache(): void {
   isInsideTmuxCached = null
   isInITerm2Cached = null
+  isInWindowsTerminalCached = null
 }
diff --git a/src/utils/swarm/backends/registry.ts b/src/utils/swarm/backends/registry.ts
index 4035a821d..b1e0b7d4b 100644
--- a/src/utils/swarm/backends/registry.ts
+++ b/src/utils/swarm/backends/registry.ts
@@ -1,12 +1,15 @@
 import { getIsNonInteractiveSession } from '../../../bootstrap/state.js'
 import { logForDebugging } from '../../../utils/debug.js'
+import { errorMessage } from '../../../utils/errors.js'
 import { getPlatform } from '../../../utils/platform.js'
 import {
   isInITerm2,
+  isInWindowsTerminal,
   isInsideTmux,
   isInsideTmuxSync,
   isIt2CliAvailable,
   isTmuxAvailable,
+  isWindowsTerminalAvailable,
 } from './detection.js'
 import { createInProcessBackend } from './InProcessBackend.js'
 import { getPreferTmuxOverIterm2 } from './it2Setup.js'
@@ -65,6 +68,11 @@ let TmuxBackendClass: (new () => PaneBackend) | null = null
  */
 let ITermBackendClass: (new () => PaneBackend) | null = null
 
+/**
+ * Placeholder for WindowsTerminalBackend.
+ */
+let WindowsTerminalBackendClass: (new () => PaneBackend) | null = null
+
 /**
  * Ensures backend classes are dynamically imported so getBackendByType() can
  * construct them. Unlike detectAndGetBackend(), this never spawns subprocesses
@@ -75,6 +83,7 @@ export async function ensureBackendsRegistered(): Promise<void> {
   if (backendsRegistered) return
   await import('./TmuxBackend.js')
   await import('./ITermBackend.js')
+  await import('./WindowsTerminalBackend.js')
   backendsRegistered = true
 }
 
@@ -99,6 +108,12 @@ export function registerITermBackend(
   ITermBackendClass = backendClass
 }
 
+export function registerWindowsTerminalBackend(
+  backendClass: new () => PaneBackend,
+): void {
+  WindowsTerminalBackendClass = backendClass
+}
+
 /**
  * Creates a TmuxBackend instance.
  * Throws if TmuxBackend hasn't been registered.
@@ -125,6 +140,15 @@ function createITermBackend(): PaneBackend {
   return new ITermBackendClass()
 }
 
+function createWindowsTerminalBackend(): PaneBackend {
+  if (!WindowsTerminalBackendClass) {
+    throw new Error(
+      'WindowsTerminalBackend not registered. Import WindowsTerminalBackend.ts before using the registry.',
+    )
+  }
+  return new WindowsTerminalBackendClass()
+}
+
 /**
  * Detection priority flow:
  * 1. If inside tmux, always use tmux (even in iTerm2)
@@ -150,11 +174,32 @@ export async function detectAndGetBackend(): Promise<BackendDetectionResult> {
   // Check all environment conditions upfront for logging
   const insideTmux = await isInsideTmux()
   const inITerm2 = isInITerm2()
+  const inWindowsTerminal = isInWindowsTerminal()
 
   logForDebugging(
-    `[BackendRegistry] Environment: insideTmux=${insideTmux}, inITerm2=${inITerm2}`,
+    `[BackendRegistry] Environment: insideTmux=${insideTmux}, inITerm2=${inITerm2}, inWindowsTerminal=${inWindowsTerminal}`,
   )
 
+  if (getTeammateMode() === 'windows-terminal') {
+    if (getPlatform() !== 'windows') {
+      throw new Error(
+        'Windows Terminal teammate mode is only available on Windows',
+      )
+    }
+    const wtAvailable = await isWindowsTerminalAvailable()
+    if (!wtAvailable) {
+      throw new Error('Windows Terminal teammate mode requires wt.exe in PATH')
+    }
+    const backend = createWindowsTerminalBackend()
+    cachedBackend = backend
+    cachedDetectionResult = {
+      backend,
+      isNative: inWindowsTerminal,
+      needsIt2Setup: false,
+    }
+    return cachedDetectionResult
+  }
+
   // Priority 1: If inside tmux, always use tmux
   if (insideTmux) {
     logForDebugging(
@@ -230,7 +275,30 @@ export async function detectAndGetBackend(): Promise<BackendDetectionResult> {
     )
   }
 
-  // Priority 3: Fall back to tmux external session
+  // Priority 3: Native Windows Terminal panes/tabs — only when actually
+  // running INSIDE Windows Terminal. If running in VS Code's integrated
+  // terminal or another non-WT environment, fall through to in-process
+  // mode instead of opening an external Windows Terminal window.
+  if (getPlatform() === 'windows' && inWindowsTerminal) {
+    const wtAvailable = await isWindowsTerminalAvailable()
+    logForDebugging(
+      `[BackendRegistry] Inside Windows Terminal, wt.exe available: ${wtAvailable}`,
+    )
+
+    if (wtAvailable) {
+      logForDebugging('[BackendRegistry] Selected: Windows Terminal (wt.exe)')
+      const backend = createWindowsTerminalBackend()
+      cachedBackend = backend
+      cachedDetectionResult = {
+        backend,
+        isNative: true,
+        needsIt2Setup: false,
+      }
+      return cachedDetectionResult
+    }
+  }
+
+  // Priority 4: Fall back to tmux external session
   const tmuxAvailable = await isTmuxAvailable()
   logForDebugging(
     `[BackendRegistry] Not in tmux or iTerm2, tmux available: ${tmuxAvailable}`,
@@ -298,6 +366,8 @@ export function getBackendByType(type: PaneBackendType): PaneBackend {
       return createTmuxBackend()
     case 'iterm2':
       return createITermBackend()
+    case 'windows-terminal':
+      return createWindowsTerminalBackend()
   }
 }
 
@@ -332,7 +402,11 @@ export function markInProcessFallback(): void {
  * Gets the teammate mode for this session.
  * Returns the session snapshot captured at startup, ignoring runtime config changes.
  */
-function getTeammateMode(): 'auto' | 'tmux' | 'in-process' {
+function getTeammateMode():
+  | 'auto'
+  | 'tmux'
+  | 'windows-terminal'
+  | 'in-process' {
   return getTeammateModeFromSnapshot()
 }
 
@@ -346,6 +420,7 @@ function getTeammateMode(): 'auto' | 'tmux' | 'in-process' {
  *   - If inside tmux, use pane backend (return false)
  *   - If inside iTerm2, use pane backend (return false) - detectAndGetBackend()
  *     will pick ITermBackend if it2 is available, or fall back to tmux
+ *   - If inside Windows Terminal, use pane backend (return false)
  *   - Otherwise, use in-process (return true)
  */
 export function isInProcessEnabled(): boolean {
@@ -363,7 +438,7 @@ export function isInProcessEnabled(): boolean {
   let enabled: boolean
   if (mode === 'in-process') {
     enabled = true
-  } else if (mode === 'tmux') {
+  } else if (mode === 'tmux' || mode === 'windows-terminal') {
     enabled = false
   } else {
     // 'auto' mode - if a prior spawn fell back to in-process because no pane
@@ -376,14 +451,26 @@ export function isInProcessEnabled(): boolean {
       return true
     }
     // Check if a pane backend environment is available
-    // If inside tmux or iTerm2, use pane backend; otherwise use in-process
+    // If inside tmux, iTerm2, or Windows Terminal, use pane backend; otherwise use in-process
     const insideTmux = isInsideTmuxSync()
     const inITerm2 = isInITerm2()
-    enabled = !insideTmux && !inITerm2
+    const inWindowsTerminal = isInWindowsTerminal()
+    if (
+      !insideTmux &&
+      !inITerm2 &&
+      !inWindowsTerminal &&
+      getPlatform() === 'windows'
+    ) {
+      // On Windows, even outside Windows Terminal (e.g. VS Code terminal, cmd.exe),
+      // wt.exe may still be available. Let detectAndGetBackend() do the full async check.
+      enabled = false
+    } else {
+      enabled = !insideTmux && !inITerm2 && !inWindowsTerminal
+    }
   }
 
   logForDebugging(
-    `[BackendRegistry] isInProcessEnabled: ${enabled} (mode=${mode}, insideTmux=${isInsideTmuxSync()}, inITerm2=${isInITerm2()})`,
+    `[BackendRegistry] isInProcessEnabled: ${enabled} (mode=${mode})`,
   )
   return enabled
 }
@@ -393,8 +480,15 @@ export function isInProcessEnabled(): boolean {
  * Unlike getTeammateModeFromSnapshot which may return 'auto', this returns
  * what 'auto' actually resolves to given the current environment.
  */
-export function getResolvedTeammateMode(): 'in-process' | 'tmux' {
-  return isInProcessEnabled() ? 'in-process' : 'tmux'
+export function getResolvedTeammateMode():
+  | 'in-process'
+  | 'tmux'
+  | 'windows-terminal' {
+  if (isInProcessEnabled()) return 'in-process'
+  const mode = getTeammateMode()
+  if (mode === 'windows-terminal') return 'windows-terminal'
+  if (mode === 'auto' && getPlatform() === 'windows') return 'windows-terminal'
+  return 'tmux'
 }
 
 /**
@@ -424,24 +518,51 @@ export function getInProcessBackend(): TeammateExecutor {
  */
 export async function getTeammateExecutor(
   preferInProcess: boolean = false,
+  options?: {
+    onNeedsIt2Setup?: (
+      tmuxAvailable: boolean,
+    ) => Promise<'installed' | 'use-tmux' | 'cancelled'>
+  },
 ): Promise<TeammateExecutor> {
   if (preferInProcess && isInProcessEnabled()) {
     logForDebugging('[BackendRegistry] Using in-process executor')
     return getInProcessBackend()
   }
 
-  // Return pane backend executor
-  logForDebugging('[BackendRegistry] Using pane backend executor')
-  return getPaneBackendExecutor()
+  try {
+    logForDebugging('[BackendRegistry] Using pane backend executor')
+    return await getPaneBackendExecutor(options)
+  } catch (error) {
+    if (getTeammateModeFromSnapshot() !== 'auto') {
+      throw error
+    }
+    logForDebugging(
+      `[BackendRegistry] No pane backend available, falling back to in-process: ${errorMessage(error)}`,
+    )
+    markInProcessFallback()
+    return getInProcessBackend()
+  }
 }
 
 /**
  * Gets the PaneBackendExecutor instance.
  * Creates and caches the instance on first call, detecting the appropriate pane backend.
  */
-async function getPaneBackendExecutor(): Promise<TeammateExecutor> {
+async function getPaneBackendExecutor(options?: {
+  onNeedsIt2Setup?: (
+    tmuxAvailable: boolean,
+  ) => Promise<'installed' | 'use-tmux' | 'cancelled'>
+}): Promise<TeammateExecutor> {
   if (!cachedPaneBackendExecutor) {
     const detection = await detectAndGetBackend()
+    if (detection.needsIt2Setup && options?.onNeedsIt2Setup) {
+      const setupResult = await options.onNeedsIt2Setup(await isTmuxAvailable())
+      if (setupResult === 'cancelled') {
+        throw new Error('Teammate spawn cancelled - iTerm2 setup required')
+      }
+      resetBackendDetection()
+      return getPaneBackendExecutor(options)
+    }
     cachedPaneBackendExecutor = createPaneBackendExecutor(detection.backend)
     logForDebugging(
       `[BackendRegistry] Created PaneBackendExecutor wrapping ${detection.backend.type}`,
diff --git a/src/utils/swarm/backends/teammateModeSnapshot.ts b/src/utils/swarm/backends/teammateModeSnapshot.ts
index e73f9d61d..535458605 100644
--- a/src/utils/swarm/backends/teammateModeSnapshot.ts
+++ b/src/utils/swarm/backends/teammateModeSnapshot.ts
@@ -10,7 +10,7 @@ import { getGlobalConfig } from '../../../utils/config.js'
 import { logForDebugging } from '../../../utils/debug.js'
 import { logError } from '../../../utils/log.js'
 
-export type TeammateMode = 'auto' | 'tmux' | 'in-process'
+export type TeammateMode = 'auto' | 'tmux' | 'windows-terminal' | 'in-process'
 
 // Module-level variable to hold the captured mode at startup
 let initialTeammateMode: TeammateMode | null = null
diff --git a/src/utils/swarm/backends/types.ts b/src/utils/swarm/backends/types.ts
index 185253ad5..0bc97b7e8 100644
--- a/src/utils/swarm/backends/types.ts
+++ b/src/utils/swarm/backends/types.ts
@@ -1,23 +1,27 @@
 import type { AgentColorName } from '@claude-code-best/builtin-tools/tools/AgentTool/agentColorManager.js'
+import type { CustomAgentDefinition } from '@claude-code-best/builtin-tools/tools/AgentTool/loadAgentsDir.js'
+import type { ToolUseContext } from '../../../Tool.js'
 
 /**
  * Types of backends available for teammate execution.
  * - 'tmux': Uses tmux for pane management (works in tmux or standalone)
  * - 'iterm2': Uses iTerm2 native split panes via the it2 CLI
+ * - 'windows-terminal': Uses Windows Terminal panes/tabs via wt.exe
  * - 'in-process': Runs teammate in the same Node.js process with isolated context
  */
-export type BackendType = 'tmux' | 'iterm2' | 'in-process'
+export type BackendType = 'tmux' | 'iterm2' | 'windows-terminal' | 'in-process'
 
 /**
  * Subset of BackendType for pane-based backends only.
  * Used in messages and types that specifically deal with terminal panes.
  */
-export type PaneBackendType = 'tmux' | 'iterm2'
+export type PaneBackendType = 'tmux' | 'iterm2' | 'windows-terminal'
 
 /**
  * Opaque identifier for a pane managed by a backend.
  * For tmux, this is the tmux pane ID (e.g., "%1").
  * For iTerm2, this is the session ID returned by it2.
+ * For Windows Terminal, this is an internal id mapped to the spawned shell PID.
  */
 export type PaneId = string
 
@@ -73,6 +77,15 @@ export type PaneBackend = {
     color: AgentColorName,
   ): Promise<CreatePaneResult>
 
+  /**
+   * Creates a separate terminal window/tab for a teammate when supported.
+   * This preserves the legacy `use_splitpane: false` behavior.
+   */
+  createTeammateWindowInSwarmView?(
+    name: string,
+    color: AgentColorName,
+  ): Promise<CreatePaneResult & { windowName: string }>
+
   /**
    * Sends a command to execute in a specific pane.
    *
@@ -209,14 +222,24 @@ export type TeammateSpawnConfig = TeammateIdentity & {
   cwd: string
   /** Model to use for this teammate */
   model?: string
+  /** Optional custom agent type for process-based teammates. */
+  agentType?: string
+  /** Optional resolved custom agent definition for in-process teammates. */
+  agentDefinition?: CustomAgentDefinition
+  /** Short description of the task, used for prompt display. */
+  description?: string
   /** System prompt for this teammate (resolved from workflow config) */
   systemPrompt?: string
   /** How to apply the system prompt: 'replace' or 'append' to default */
   systemPromptMode?: 'default' | 'replace' | 'append'
   /** Optional git worktree path */
   worktreePath?: string
+  /** false preserves legacy separate-window spawning for pane-capable backends. */
+  useSplitPane?: boolean
   /** Parent session ID (for context linking) */
   parentSessionId: string
+  /** request_id of the API call that spawned this teammate. */
+  invokingRequestId?: string
   /** Tool permissions to grant this teammate */
   permissions?: string[]
   /** Whether this teammate can show permission prompts for unlisted tools.
@@ -251,6 +274,16 @@ export type TeammateSpawnResult = {
 
   /** Pane ID (pane-based only) */
   paneId?: PaneId
+  /** Backend used for the spawned teammate. */
+  backendType?: BackendType
+  /** Assigned color for display. */
+  color?: AgentColorName
+  /** Whether the pane was spawned inside the user's current tmux session. */
+  insideTmux?: boolean
+  /** Window/tab name when the backend created a separate window. */
+  windowName?: string
+  /** Whether the backend used split panes. */
+  isSplitPane?: boolean
 }
 
 /**
@@ -280,6 +313,9 @@ export type TeammateExecutor = {
   /** Backend type identifier */
   readonly type: BackendType
 
+  /** Provide AppState/tool context before lifecycle operations that need it. */
+  setContext?(context: ToolUseContext): void
+
   /** Check if this executor is available on the system */
   isAvailable(): Promise<boolean>
 
@@ -306,6 +342,8 @@ export type TeammateExecutor = {
 /**
  * Type guard to check if a backend type uses terminal panes.
  */
-export function isPaneBackend(type: BackendType): type is 'tmux' | 'iterm2' {
-  return type === 'tmux' || type === 'iterm2'
+export function isPaneBackend(
+  type: BackendType,
+): type is 'tmux' | 'iterm2' | 'windows-terminal' {
+  return type === 'tmux' || type === 'iterm2' || type === 'windows-terminal'
 }
diff --git a/src/utils/swarm/spawnInProcess.ts b/src/utils/swarm/spawnInProcess.ts
index 1a4f6c857..5cfa0ab5a 100644
--- a/src/utils/swarm/spawnInProcess.ts
+++ b/src/utils/swarm/spawnInProcess.ts
@@ -339,3 +339,35 @@ export function killInProcessTeammate(
 
   return killed
 }
+
+/**
+ * Kills an in-process teammate by logical agent ID.
+ * Used by team-level UI/actions where the stable identifier is
+ * "name@team", not the AppState task id.
+ */
+export function killInProcessTeammateByAgentId(
+  agentIdToKill: string,
+  setAppState: SetAppStateFn,
+): boolean {
+  let taskIdToKill: string | undefined
+
+  setAppState((prev: AppState) => {
+    for (const [taskId, task] of Object.entries(prev.tasks)) {
+      if (
+        task.type === 'in_process_teammate' &&
+        task.identity.agentId === agentIdToKill &&
+        task.status === 'running'
+      ) {
+        taskIdToKill = taskId
+        break
+      }
+    }
+    return prev
+  })
+
+  if (!taskIdToKill) {
+    return false
+  }
+
+  return killInProcessTeammate(taskIdToKill, setAppState)
+}
diff --git a/src/utils/swarm/spawnUtils.ts b/src/utils/swarm/spawnUtils.ts
index cfccdf5a2..5aaa9386b 100644
--- a/src/utils/swarm/spawnUtils.ts
+++ b/src/utils/swarm/spawnUtils.ts
@@ -39,6 +39,13 @@ export function buildInheritedCliFlags(options?: {
   planModeRequired?: boolean
   permissionMode?: PermissionMode
 }): string {
+  return quote(buildInheritedCliArgParts(options))
+}
+
+export function buildInheritedCliArgParts(options?: {
+  planModeRequired?: boolean
+  permissionMode?: PermissionMode
+}): string[] {
   const flags: string[] = []
   const { planModeRequired, permissionMode } = options || {}
 
@@ -52,30 +59,33 @@ export function buildInheritedCliFlags(options?: {
   ) {
     flags.push('--dangerously-skip-permissions')
   } else if (permissionMode === 'acceptEdits') {
-    flags.push('--permission-mode acceptEdits')
+    flags.push('--permission-mode', 'acceptEdits')
+  } else if (permissionMode === 'auto') {
+    // Teammates inherit auto mode so the classifier evaluates their tool calls too.
+    flags.push('--permission-mode', 'auto')
   }
 
   // Propagate --model if explicitly set via CLI
   const modelOverride = getMainLoopModelOverride()
   if (modelOverride) {
-    flags.push(`--model ${quote([modelOverride])}`)
+    flags.push('--model', modelOverride)
   }
 
   // Propagate --settings if set via CLI
   const settingsPath = getFlagSettingsPath()
   if (settingsPath) {
-    flags.push(`--settings ${quote([settingsPath])}`)
+    flags.push('--settings', settingsPath)
   }
 
   // Propagate --plugin-dir for each inline plugin
   const inlinePlugins = getInlinePlugins()
   for (const pluginDir of inlinePlugins) {
-    flags.push(`--plugin-dir ${quote([pluginDir])}`)
+    flags.push('--plugin-dir', pluginDir)
   }
 
   // Propagate --teammate-mode so tmux teammates use the same mode as leader
   const sessionMode = getTeammateModeFromSnapshot()
-  flags.push(`--teammate-mode ${sessionMode}`)
+  flags.push('--teammate-mode', sessionMode)
 
   // Propagate --chrome / --no-chrome if explicitly set on the CLI
   const chromeFlagOverride = getChromeFlagOverride()
@@ -85,7 +95,7 @@ export function buildInheritedCliFlags(options?: {
     flags.push('--no-chrome')
   }
 
-  return flags.join(' ')
+  return flags
 }
 
 /**
@@ -133,14 +143,23 @@ const TEAMMATE_ENV_VARS = [
  * plus any provider/config env vars that are set in the current process.
  */
 export function buildInheritedEnvVars(): string {
-  const envVars = ['CLAUDECODE=1', 'CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1']
+  return getInheritedEnvVarAssignments()
+    .map(([key, value]) => `${key}=${quote([value])}`)
+    .join(' ')
+}
+
+export function getInheritedEnvVarAssignments(): Array<[string, string]> {
+  const envVars: Array<[string, string]> = [
+    ['CLAUDECODE', '1'],
+    ['CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS', '1'],
+  ]
 
   for (const key of TEAMMATE_ENV_VARS) {
     const value = process.env[key]
     if (value !== undefined && value !== '') {
-      envVars.push(`${key}=${quote([value])}`)
+      envVars.push([key, value])
     }
   }
 
-  return envVars.join(' ')
+  return envVars
 }