diff --git a/src/features/team-mode/team-runtime/activate-team-layout.test.ts b/src/features/team-mode/team-runtime/activate-team-layout.test.ts
new file mode 100644
index 000000000..437f31981
--- /dev/null
+++ b/src/features/team-mode/team-runtime/activate-team-layout.test.ts
@@ -0,0 +1,166 @@
+/// <reference types="bun-types" />
+
+import { afterEach, beforeEach, describe, expect, mock, spyOn, test } from "bun:test"
+
+import { TeamModeConfigSchema } from "../../../config/schema/team-mode"
+import * as layoutModule from "../team-layout-tmux/layout"
+import * as storeModule from "../team-state-store/store"
+import { RuntimeStateSchema, type RuntimeState } from "../types"
+import { activateTeamLayout } from "./activate-team-layout"
+
+let createTeamLayoutSpy: ReturnType<typeof spyOn<typeof layoutModule, "createTeamLayout">>
+let transitionRuntimeStateSpy: ReturnType<typeof spyOn<typeof storeModule, "transitionRuntimeState">>
+
+function createRuntimeState() {
+  return RuntimeStateSchema.parse({
+    version: 1,
+    teamRunId: crypto.randomUUID(),
+    teamName: "alpha-team",
+    specSource: "project",
+    createdAt: Date.now(),
+    status: "creating",
+    leadSessionId: "ses-lead",
+    shutdownRequests: [],
+    bounds: {
+      maxMembers: 8,
+      maxParallelMembers: 4,
+      maxMessagesPerRun: 10000,
+      maxWallClockMinutes: 120,
+      maxMemberTurns: 500,
+    },
+    members: [
+      {
+        name: "lead",
+        sessionId: "ses-lead",
+        tmuxPaneId: undefined,
+        agentType: "leader",
+        status: "running",
+        pendingInjectedMessageIds: [],
+      },
+      {
+        name: "member-a",
+        sessionId: "ses-member-a",
+        tmuxPaneId: undefined,
+        agentType: "general-purpose",
+        status: "running",
+        pendingInjectedMessageIds: [],
+      },
+    ],
+  })
+}
+
+function createConfig(tmuxVisualization: boolean) {
+  return TeamModeConfigSchema.parse({ enabled: true, tmux_visualization: tmuxVisualization })
+}
+
+describe("activateTeamLayout", () => {
+  afterEach(() => {
+    mock.restore()
+  })
+
+  beforeEach(() => {
+    createTeamLayoutSpy = spyOn(layoutModule, "createTeamLayout")
+    createTeamLayoutSpy.mockResolvedValue(null)
+    transitionRuntimeStateSpy = spyOn(storeModule, "transitionRuntimeState")
+    transitionRuntimeStateSpy.mockImplementation(async (
+      _teamRunId,
+      transition,
+      _config,
+    ): Promise<RuntimeState> => transition(createRuntimeState()))
+  })
+
+  test("#given a leader and one member #when activateTeamLayout runs #then it excludes the leader from layout members and only persists panes for non-leaders", async () => {
+    // given
+    const runtimeState = createRuntimeState()
+    createTeamLayoutSpy.mockResolvedValue({
+      focusWindowId: "@10",
+      gridWindowId: "@11",
+      focusPanesByMember: { "member-a": "%11" },
+      gridPanesByMember: { "member-a": "%21" },
+      targetSessionId: "$caller",
+      ownedSession: false,
+    })
+
+    // when
+    const result = await activateTeamLayout(
+      runtimeState,
+      createConfig(true),
+      "/project",
+      { getServerUrl: () => "http://127.0.0.1:12345" } as never,
+    )
+
+    // then
+    expect(result).toBe(true)
+    expect(createTeamLayoutSpy).toHaveBeenCalledTimes(1)
+    const createLayoutCall = createTeamLayoutSpy.mock.calls[0]
+    expect(createLayoutCall?.[1]).toEqual([
+      {
+        name: "member-a",
+        sessionId: "ses-member-a",
+        color: undefined,
+        worktreePath: "/project",
+      },
+    ])
+    expect(transitionRuntimeStateSpy).toHaveBeenCalledTimes(1)
+    const transitionCall = transitionRuntimeStateSpy.mock.calls[0]
+    if (!transitionCall) {
+      throw new Error("expected transitionRuntimeState to be called")
+    }
+    const [teamRunId, transition] = transitionCall
+    expect(teamRunId).toBe(runtimeState.teamRunId)
+    const nextState = transition(runtimeState)
+    expect(nextState.members).toEqual([
+      {
+        ...runtimeState.members[0],
+        tmuxPaneId: undefined,
+        tmuxGridPaneId: undefined,
+      },
+      {
+        ...runtimeState.members[1],
+        tmuxPaneId: "%11",
+        tmuxGridPaneId: "%21",
+      },
+    ])
+    expect(nextState.tmuxLayout).toEqual({
+      ownedSession: false,
+      targetSessionId: "$caller",
+      focusWindowId: "@10",
+      gridWindowId: "@11",
+    })
+  })
+
+  test("#given createTeamLayout returns null #when activateTeamLayout runs #then returns false and no state transition fires", async () => {
+    // given
+    const runtimeState = createRuntimeState()
+
+    // when
+    const result = await activateTeamLayout(
+      runtimeState,
+      createConfig(true),
+      "/project",
+      { getServerUrl: () => "http://127.0.0.1:12345" } as never,
+    )
+
+    // then
+    expect(result).toBe(false)
+    expect(transitionRuntimeStateSpy).not.toHaveBeenCalled()
+  })
+
+  test("#given config.tmux_visualization is false #when activateTeamLayout runs #then it short-circuits, no state change, returns false", async () => {
+    // given
+    const runtimeState = createRuntimeState()
+
+    // when
+    const result = await activateTeamLayout(
+      runtimeState,
+      createConfig(false),
+      "/project",
+      { getServerUrl: () => "http://127.0.0.1:12345" } as never,
+    )
+
+    // then
+    expect(result).toBe(false)
+    expect(createTeamLayoutSpy).not.toHaveBeenCalled()
+    expect(transitionRuntimeStateSpy).not.toHaveBeenCalled()
+  })
+})
diff --git a/src/features/team-mode/team-runtime/activate-team-layout.ts b/src/features/team-mode/team-runtime/activate-team-layout.ts
new file mode 100644
index 000000000..427792ec9
--- /dev/null
+++ b/src/features/team-mode/team-runtime/activate-team-layout.ts
@@ -0,0 +1,54 @@
+import type { TeamModeConfig } from "../../../config/schema/team-mode"
+import type { TmuxSessionManager } from "../../tmux-subagent/manager"
+import { createTeamLayout } from "../team-layout-tmux/layout"
+import type { TeamLayoutResult } from "../team-layout-tmux/layout"
+import type { RuntimeState } from "../types"
+import { transitionRuntimeState } from "../team-state-store/store"
+
+function normalizeTeamLayout(teamRunId: string, layout: TeamLayoutResult): TeamLayoutResult {
+  return {
+    ...layout,
+    targetSessionId: layout.targetSessionId ?? `omo-team-${teamRunId}`,
+    ownedSession: layout.ownedSession ?? true,
+  }
+}
+
+export async function activateTeamLayout(
+  runtimeState: RuntimeState,
+  config: TeamModeConfig,
+  projectRoot: string,
+  tmuxMgr?: TmuxSessionManager,
+): Promise<boolean> {
+  if (!config.tmux_visualization || !tmuxMgr) return false
+
+  const layout = await createTeamLayout(
+    runtimeState.teamRunId,
+    runtimeState.members.flatMap((member) => member.sessionId && member.agentType !== "leader"
+      ? [{
+          name: member.name,
+          sessionId: member.sessionId,
+          color: member.color,
+          worktreePath: member.worktreePath ?? projectRoot,
+        }]
+      : []),
+    tmuxMgr,
+  )
+  if (!layout) return false
+  const normalizedLayout = normalizeTeamLayout(runtimeState.teamRunId, layout)
+
+  await transitionRuntimeState(runtimeState.teamRunId, (currentState) => ({
+    ...currentState,
+    tmuxLayout: {
+      ownedSession: normalizedLayout.ownedSession,
+      targetSessionId: normalizedLayout.targetSessionId,
+      focusWindowId: normalizedLayout.focusWindowId,
+      gridWindowId: normalizedLayout.gridWindowId,
+    },
+    members: currentState.members.map((member) => ({
+      ...member,
+      tmuxPaneId: normalizedLayout.focusPanesByMember[member.name] ?? member.tmuxPaneId,
+      tmuxGridPaneId: normalizedLayout.gridPanesByMember[member.name] ?? member.tmuxGridPaneId,
+    })),
+  }), config)
+  return true
+}