False "Update available!" notice repeats on idle, even when apt-managed install is already latest

Description

Claude Code repeatedly shows an "Update available! Run: [your package manager update command]" notice after a few seconds of idling at the prompt, even though the installed version is already the latest one published to the apt repo.

Environment

• Claude Code version: 2.1.224 (commit 8a2a469b68f9)
• Install method: apt (deb), from https://downloads.claude.ai/claude-code/apt/stable
• OS: Ubuntu 26.04 LTS (resolute), linux-x64
• claude doctor output:

``
Running: package-manager (2.1.224)
Commit: 8a2a469b68f9
Platform: linux-x64
Package manager: deb
Path: /usr/bin/claude
Config install method: unknown
Auto-updates: Managed by package manager
Auto-update channel: latest
Last update attempt: none recorded
No installation issues found.
``

Steps to reproduce

1. Install Claude Code via the apt repo on Ubuntu.
2. Leave the CLI idle at the prompt for a few seconds.
3. Observe the "Update available!" notice fire.

What I've ruled out

• Not an Ubuntu Pro/ESM nag — machine is not attached to Ubuntu Pro (pro status confirms), and the message text ("Update available! Run: ...") is compiled directly into the claude binary itself (strings /usr/bin/claude | grep "Update available" finds it, tied to a PackageManagerAutoUpdater string).
• Not a stale local apt cache — ran sudo apt update fresh, then apt-cache policy claude-code: installed and candidate are both 2.1.224-1, no newer version available in the repo.
• claude update confirms: "Claude is managed by a package manager. Please use your package manager to update," with current version 2.1.224 and nothing pending.

Expected behavior

No update notice when the installed apt package is already the latest available in the configured repo, and/or the background checker should not repeatedly re-fire once a session has already dismissed/checked it.

Actual behavior

Notice fires repeatedly on idle regardless of already being current.