Third-party marketplace with autoUpdate:true not refreshed at session start; new release not picked up across restarts (v2.1.175)

Environment

• Claude Code v2.1.175, macOS (Darwin 25.5.0), native installer
• Third-party marketplace: private self-hosted GitLab, added via SSH URL (git@<internal-host>:<group>/<repo>.git), one plugin installed at user scope
• autoUpdate: true confirmed in ~/.claude/plugins/known_marketplaces.json; the /plugin UI shows: "Auto-update enabled. Claude Code will automatically update this marketplace and its installed plugins."

Timeline (one machine, same day, UTC)

| Time | Event |
|---|---|
| 10:29:18 | Third-party marketplace added + auto-update enabled (lastUpdated: 10:29:18) |
| 10:31:06 | Official claude-plugins-official pulled (lastUpdated: 10:31:06) |
| 10:47 | New plugin version (1.0.0 → 1.0.1) merged to the marketplace repo's default branch |
| ~10:40–10:55 | At least two full CLI exit/relaunch cycles |
| 10:52 | Third-party lastUpdated still 10:29:18; installed plugin still 1.0.0 |
| 11:01 | Manual /plugin → Marketplaces → Update marketplace → pull succeeds instantly, 1.0.1 installs fine |

Ruled out

• Auth: GIT_TERMINAL_PROMPT=0 git ls-remote <ssh-url> succeeds non-interactively from the same machine (returned the new default-branch tip) — the silent background fetch has working credentials.
• DISABLE_AUTOUPDATER: not set in the login shell environment.
• Manual path: both the /plugin UI action and claude plugin marketplace update work immediately — only the automatic startup path does nothing.

Observation that may matter

During the same restarts the official marketplace's lastUpdated (10:31:06) didn't move either. So this could be an undocumented startup throttle affecting all marketplaces rather than third-party-specific discrimination. But the docs only say updates are checked "on startup" with no cadence specified — from a user's perspective, a window where autoUpdate: true silently does nothing while the UI promises automatic updates is indistinguishable from broken.

#26744 reported the same symptom (third-party marketplace git reflog shows auto-pulls only on installation day, then never again) and was closed by stale-bot without a maintainer response — please treat this as a fresh reproduction with auth and configuration ruled out.

Expected

Either:

• (a) third-party marketplaces with autoUpdate: true refresh at session start the same way the official marketplace does, or
• (b) the actual cadence/throttle is documented (docs + ideally surfaced in the /plugin UI), so team plugin-distribution setups can rely on a defined behavior.

Workaround we ship to our team

A plugin skill that wraps the non-interactive CLI: claude plugin marketplace update <name> + claude plugin update <plugin>@<name> — works reliably; only the automatic trigger is missing.