[BUG] Cowork "Live Artifacts" sidebar entry point appears once, then disappears on relaunch — server-side rollout flicker

Summary

The "Create Live Artifact" entry point in the Cowork sidebar appeared briefly on my account, then disappeared after I quit and reopened the Claude desktop app. It has not returned. The underlying feature (CoworkArtifacts) is fully functional via the mcp__cowork__* MCP tools — I currently have one live artifact running and auto-refreshing — but there is no UI affordance to view, create, or manage artifacts from the sidebar.

Environment

• App version: 1.3561.0 (installed today)
• OS: macOS
• Account ID: 6e0d19c8-8b39-4184-bf65-31c4f9d5dbd6

Reproduction

1. Saw the "Create Live Artifact" entry in the Cowork sidebar (~2 seconds visible).
2. Quit the Claude desktop app.
3. Relaunched. The entry was gone.
4. Subsequent restarts, force restarts, and Dispatch sidebar toggles have not brought it back.

Diagnostic findings

After digging through ~/Library/Application Support/Claude/ and /Applications/Claude.app/:

The feature is intact at the data layer.

• Artifact registry exists at ~/Library/Application Support/Claude/local-agent-mode-sessions/<accountId>/<orgId>/artifacts.json and contains my one artifact (daily-dashboard).
• The artifact is in pinnedOrder in Local Storage as cowork-artifact:daily-dashboard.
• The cowork MCP server registers 6 tools on every startup (main.log:99601), including create_artifact. The cowork-artifact:// Electron protocol handler is registered on every launch.
• main.log shows the artifact was created via mcp__cowork__create_artifact (not via menu click), and it has been calling get_my_tasks / list_events to auto-refresh ever since.

The sidebar item is not gated locally.

• cowork-gb-cache.json (GrowthBook flag cache) contains only tengu_* flags — none reference artifacts, live, dashboard, or sidebar items.
• supported-features-info.json lists internal codenames (plushRaccoon, operon, floatingAtoll, etc.); none map to live artifacts.
• The token cowork-artifacts does appear in Local Storage under LSS-dframe-sidebar-seen-badges, confirming the sidebar item was rendered on this machine at some point.

The sidebar is rendered server-side.

• The local renderer bundle (main-DDf5rR9t.js, 292 KB) contains no sidebar-item references at all — no "Dispatch", "Scheduled", "Projects", or "Customize" strings.
• index.js in the app bundle calls loadURL("https://claude.ai") — the desktop app is an Electron shell wrapping a claude.ai webview.
• Toggling the Dispatch sidebar item produces zero main.log entries, only renderer-side LevelDB writes.

Conclusion: the Cowork sidebar item registry comes from claude.ai's server response on each page load. Whether "Create Live Artifact" renders is decided server-side per request. Nothing local — config file, cache clear, or reinstall — can change this.

Expected behavior

Once a Live Artifact has been created on an account, the sidebar entry point to view/manage artifacts should remain consistently visible across app launches, regardless of which side of an A/B test the next page load lands on.

Actual behavior

The entry point flickers in and out based on what claude.ai returns per page load. Users with already-created artifacts can be left without any UI to manage them.

Related

Likely the same root cause as #49428, #48407, and #49748 (Cowork tabs disappearing after updates), but the specific symptom here — Live Artifacts entry point being intermittently served — is narrower and may be debuggable independently via the rollout flag controlling that sidebar item.