[BUG] /design-sync bundled skill silently disabled by server-side flag while DesignSync tool stays enabled — broke a scheduled cloud routine mid-flight

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet (closest: #71738 — same symptom, different root cause, see below)
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The /design-sync bundled skill disappeared from my account sometime between 2026-07-16 and 2026-08-03 — simultaneously in local Claude Code (2.1.218–2.1.220) and in cloud scheduled routines (CCR sandboxes). The DesignSync tool is still available and authorizes fine, so the account is in a half-enabled state: the API channel works, but the skill that drives it is gone.

This broke unattended automation. A scheduled cloud routine (Mon+Thu re-sync of our design system to claude.ai/design, running successfully since 2026-07-13) failed on its 2026-08-03 firing because the skill vanished between runs — no deprecation notice, no changelog entry, no warning.

What I've ruled out and verified:

• Not #71738's cause: CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC is not set in my env or any settings.json.
• The skill still ships in the binary: 2.1.220 contains the full skill content and its registration.
• The registration's isEnabled gate is byte-for-byte identical logic in 2.1.201 (working era) and 2.1.220: an allow_design_sync check, two local predicates, then a remote flag lookup (tengu_slate_quill, default false). Since the code didn't change, the remote flag value flipping off is the only explanation consistent with the skill disappearing across local and cloud environments at once.

What Should Happen?

Either the skill is available (matching the still-enabled DesignSync tool), or its unavailability is signaled: a changelog/deprecation note, a CLI warning, or the slash command resolving to a stub that says "disabled by rollout" instead of silently vanishing. Bundled skills are things users build automation on — a scheduled routine can't distinguish "feature deprecated, stop scheduling me" from "transient outage, retry Thursday."

Concretely, I'd love answers to: is this a rollout pause, a repackaging (plugin?), or a deprecation? That determines whether workarounds are a bridge or a fork.

Related in principle: #69528 (silent degradation of feature availability hurts power users).

Error Messages/Logs

Status: STOPPED — routine could not run.
Reason: The /design-sync skill is unavailable in this environment. The DesignSync
tool loaded fine, but the skill that drives the re-sync flow is absent from every
source (user-invocable skills, claude.ai skills, plugins, marketplace,
/root/.claude/skills/, and the local repo).

Steps to Reproduce

1. Account with a previously working /design-sync (ours synced 67 components across ~15 runs, June 18 – July 16).
2. Open Claude Code 2.1.220 → /design-sync absent from the skill list; DesignSync tool still loads via ToolSearch.
3. Same result in a fresh cloud routine sandbox — so it's not local config.

Claude Model

Opus (routine runs claude-opus-4-8) — model-independent

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.201 (local); cloud routine last succeeded 2026-07-16

Claude Code Version

2.1.220

Platform

Claude subscription (Max/Team)

Operating System

macOS (Darwin 25.5.0); cloud sandbox Linux

Terminal/Shell

zsh