feat(tools): add switch agent background workflow

src/features/claude-code-session-state/index.ts

@@ -1 +1,2 @@
 export * from "./state"
+export * from "./switch-agent-state"

src/features/claude-code-session-state/state.ts

@@ -1,3 +1,5 @@
+import { resetPendingSessionAgentSwitchesForTesting } from "./switch-agent-state"
+
 export const subagentSessions = new Set<string>()
 export const syncSubagentSessions = new Set<string>()
 
@@ -17,6 +19,7 @@ export function _resetForTesting(): void {
   subagentSessions.clear()
   syncSubagentSessions.clear()
   sessionAgentMap.clear()
+  resetPendingSessionAgentSwitchesForTesting()
 }
 
 const sessionAgentMap = new Map<string, string>()

src/features/claude-code-session-state/switch-agent-state.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, test, beforeEach } from "bun:test"
+import {
+  clearPendingSessionAgentSwitch,
+  consumePendingSessionAgentSwitch,
+  getPendingSessionAgentSwitch,
+  resetPendingSessionAgentSwitchesForTesting,
+  setPendingSessionAgentSwitch,
+} from "./switch-agent-state"
+
+describe("switch-agent-state", () => {
+  beforeEach(() => {
+    resetPendingSessionAgentSwitchesForTesting()
+  })
+
+  test("#given pending switch #when consuming #then consumes once and clears", () => {
+    // given
+    setPendingSessionAgentSwitch("ses-1", "explore")
+
+    // when
+    const first = consumePendingSessionAgentSwitch("ses-1")
+    const second = consumePendingSessionAgentSwitch("ses-1")
+
+    // then
+    expect(first?.agent).toBe("explore")
+    expect(second).toBeUndefined()
+  })
+
+  test("#given pending switch #when clearing #then state is removed", () => {
+    // given
+    setPendingSessionAgentSwitch("ses-1", "librarian")
+
+    // when
+    clearPendingSessionAgentSwitch("ses-1")
+
+    // then
+    expect(getPendingSessionAgentSwitch("ses-1")).toBeUndefined()
+  })
+})

src/features/claude-code-session-state/switch-agent-state.ts

@@ -0,0 +1,37 @@
+type PendingAgentSwitch = {
+  agent: string
+  requestedAt: Date
+}
+
+const pendingAgentSwitchBySession = new Map<string, PendingAgentSwitch>()
+
+export function setPendingSessionAgentSwitch(sessionID: string, agent: string): PendingAgentSwitch {
+  const pendingSwitch: PendingAgentSwitch = {
+    agent,
+    requestedAt: new Date(),
+  }
+  pendingAgentSwitchBySession.set(sessionID, pendingSwitch)
+  return pendingSwitch
+}
+
+export function getPendingSessionAgentSwitch(sessionID: string): PendingAgentSwitch | undefined {
+  return pendingAgentSwitchBySession.get(sessionID)
+}
+
+export function consumePendingSessionAgentSwitch(sessionID: string): PendingAgentSwitch | undefined {
+  const pendingSwitch = pendingAgentSwitchBySession.get(sessionID)
+  if (!pendingSwitch) {
+    return undefined
+  }
+
+  pendingAgentSwitchBySession.delete(sessionID)
+  return pendingSwitch
+}
+
+export function clearPendingSessionAgentSwitch(sessionID: string): void {
+  pendingAgentSwitchBySession.delete(sessionID)
+}
+
+export function resetPendingSessionAgentSwitchesForTesting(): void {
+  pendingAgentSwitchBySession.clear()
+}