diff --git a/src/hooks/auto-update-checker/hook.test.ts b/src/hooks/auto-update-checker/hook.test.ts
new file mode 100644
index 000000000..b7d8e5232
--- /dev/null
+++ b/src/hooks/auto-update-checker/hook.test.ts
@@ -0,0 +1,100 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+import { describe, expect, mock, test } from "bun:test"
+
+let latestVersionCallCount = 0
+let scheduleDeferredIdleCheckCallCount = 0
+const flushMicrotasks = async (count: number): Promise<void> => {
+  for (let index = 0; index < count; index += 1) {
+    await Promise.resolve()
+  }
+}
+
+const latestVersionMock = async () => {
+  latestVersionCallCount += 1
+  return "3.0.1"
+}
+
+const scheduleDeferredIdleCheckMock = (runCheck: () => void) => {
+  scheduleDeferredIdleCheckCallCount += 1
+  scheduledCheck = runCheck
+}
+
+let scheduledCheck: (() => void) | null = null
+
+mock.module("./checker/latest-version", () => ({
+  getLatestVersion: latestVersionMock,
+}))
+
+mock.module("./hook/deferred-idle-check", () => ({
+  scheduleDeferredIdleCheck: scheduleDeferredIdleCheckMock,
+}))
+
+const createHook = async () => {
+  const module = await import("./hook")
+  return module.createAutoUpdateCheckerHook(
+    {
+      directory: "/tmp/project",
+      client: {
+        tui: {
+          showToast: async () => undefined,
+        },
+      },
+    } satisfies PluginInput,
+    {
+      showStartupToast: false,
+      autoUpdate: false,
+    },
+    {
+      getCachedVersion: () => "3.0.0",
+      getLocalDevVersion: () => null,
+      showConfigErrorsIfAny: async () => undefined,
+      updateAndShowConnectedProvidersCacheStatus: async () => undefined,
+      refreshModelCapabilitiesOnStartup: async () => undefined,
+      showModelCacheWarningIfNeeded: async () => undefined,
+      showLocalDevToast: async () => undefined,
+      showVersionToast: async () => undefined,
+      runBackgroundUpdateCheck: async () => {
+        await latestVersionMock()
+      },
+      log: () => undefined,
+    },
+  )
+}
+
+describe("auto-update-checker hook", () => {
+  test("defers update check until first session idle", async () => {
+    // given
+    latestVersionCallCount = 0
+    scheduleDeferredIdleCheckCallCount = 0
+    scheduledCheck = null
+    const hook = await createHook()
+
+    // when
+    hook.event({ event: { type: "session.created" } })
+
+    // then
+    expect(scheduleDeferredIdleCheckCallCount).toBe(0)
+    expect(latestVersionCallCount).toBe(0)
+
+    // when
+    hook.event({ event: { type: "session.idle" } })
+
+    // then
+    expect(scheduleDeferredIdleCheckCallCount).toBe(1)
+    expect(latestVersionCallCount).toBe(0)
+
+    // when
+    await scheduledCheck?.()
+    await flushMicrotasks(8)
+
+    // then
+    expect(latestVersionCallCount).toBe(1)
+
+    // when
+    hook.event({ event: { type: "session.idle" } })
+
+    // then
+    expect(scheduleDeferredIdleCheckCallCount).toBe(1)
+    expect(latestVersionCallCount).toBe(1)
+  })
+})
diff --git a/src/hooks/auto-update-checker/hook.ts b/src/hooks/auto-update-checker/hook.ts
index fbe3998da..73f5eed4b 100644
--- a/src/hooks/auto-update-checker/hook.ts
+++ b/src/hooks/auto-update-checker/hook.ts
@@ -3,6 +3,7 @@ import { log } from "../../shared/logger"
 import type { AutoUpdateCheckerOptions } from "./types"
 import { getCachedVersion, getLocalDevVersion } from "./checker"
 import { runBackgroundUpdateCheck } from "./hook/background-update-check"
+import { scheduleDeferredIdleCheck } from "./hook/deferred-idle-check"
 import { showConfigErrorsIfAny } from "./hook/config-errors-toast"
 import { updateAndShowConnectedProvidersCacheStatus } from "./hook/connected-providers-status"
 import { refreshModelCapabilitiesOnStartup } from "./hook/model-capabilities-status"
@@ -60,44 +61,45 @@ export function createAutoUpdateCheckerHook(
   }
 
   let hasChecked = false
+  let hasScheduled = false
 
   return {
     event: ({ event }: { event: { type: string; properties?: unknown } }) => {
-      if (event.type !== "session.created") return
+      if (event.type !== "session.idle") return
       if (isCliRunMode) return
-      if (hasChecked) return
+      if (hasChecked || hasScheduled) return
 
-      const props = event.properties as { info?: { parentID?: string } } | undefined
-      if (props?.info?.parentID) return
+      hasScheduled = true
 
+      scheduleDeferredIdleCheck(() => {
         hasChecked = true
+        void (async () => {
+          const cachedVersion = deps.getCachedVersion()
+          const localDevVersion = deps.getLocalDevVersion(ctx.directory)
+          const displayVersion = localDevVersion ?? cachedVersion
 
-      setTimeout(async () => {
-        const cachedVersion = deps.getCachedVersion()
-        const localDevVersion = deps.getLocalDevVersion(ctx.directory)
-        const displayVersion = localDevVersion ?? cachedVersion
+          await deps.showConfigErrorsIfAny(ctx)
+          await deps.updateAndShowConnectedProvidersCacheStatus(ctx)
+          await deps.refreshModelCapabilitiesOnStartup(modelCapabilities)
+          await deps.showModelCacheWarningIfNeeded(ctx)
 
-        await deps.showConfigErrorsIfAny(ctx)
-        await deps.updateAndShowConnectedProvidersCacheStatus(ctx)
-        await deps.refreshModelCapabilitiesOnStartup(modelCapabilities)
-        await deps.showModelCacheWarningIfNeeded(ctx)
-
-        if (localDevVersion) {
-          if (showStartupToast) {
-            deps.showLocalDevToast(ctx, displayVersion, isSisyphusEnabled).catch(() => {})
+          if (localDevVersion) {
+            if (showStartupToast) {
+              deps.showLocalDevToast(ctx, displayVersion, isSisyphusEnabled).catch(() => {})
+            }
+            deps.log("[auto-update-checker] Local development mode")
+            return
           }
-          deps.log("[auto-update-checker] Local development mode")
-          return
-        }
 
-        if (showStartupToast) {
-          deps.showVersionToast(ctx, displayVersion, getToastMessage(false)).catch(() => {})
-        }
+          if (showStartupToast) {
+            deps.showVersionToast(ctx, displayVersion, getToastMessage(false)).catch(() => {})
+          }
 
-        deps.runBackgroundUpdateCheck(ctx, autoUpdate, getToastMessage).catch((err) => {
-          deps.log("[auto-update-checker] Background update check failed:", err)
-        })
-      }, 0)
+          deps.runBackgroundUpdateCheck(ctx, autoUpdate, getToastMessage).catch((err) => {
+            deps.log("[auto-update-checker] Background update check failed:", err)
+          })
+        })()
+      })
     },
   }
 }
diff --git a/src/hooks/auto-update-checker/hook/deferred-idle-check.ts b/src/hooks/auto-update-checker/hook/deferred-idle-check.ts
new file mode 100644
index 000000000..a929cf4ee
--- /dev/null
+++ b/src/hooks/auto-update-checker/hook/deferred-idle-check.ts
@@ -0,0 +1,4 @@
+export function scheduleDeferredIdleCheck(runCheck: () => void): void {
+  const timeout = setTimeout(runCheck, 5000)
+  timeout.unref?.()
+}