Claude Code's built-in task tools are disappearing mid-session due to a server-side feature flag glitch. At least one user burned an entire week's Fable subscription trying to fix something that was never broken on their end. The issue affects versions 2.1.217 and 2.1.218, and the most dangerous part is that Anthropic provides no visible error message when the tools vanish. Your task list simply stops updating and you have no way to know why.
The core problem is a remote GrowthBook feature flag called tengu_vellum_ash. This flag acts as a per-model kill list for four task tools: TaskCreate, TaskGet, TaskList, and TaskUpdate. When the flag flaps on the server side, the tools disappear. TaskStop and TaskOutput remain available because they use a different gate. Users can confirm this by running ToolSearch for the missing tools and seeing zero results while 189 other deferred tools remain present.
This is not a rare edge case. Six separate developers confirmed the issue within 12 hours of the first report, spanning macOS, Linux, and WSL2 environments. The failure affects both interactive and headless sessions. One developer on Linux found that switching claude.ai accounts with /login toggles the tools in and out reliably, proving the gate is tied to account-level flag state rather than client version or local configuration.
Three Failure Modes Affecting Developers
- Tools never register on session start
TaskCreate and related tools are absent from the moment Claude Code launches. The user discovers this only when they try to create their first task. No error message appears. ToolSearch returns empty results for these four tools while everything else works.
- Tools vanish mid-session without warning
A working session suddenly loses task access. The live task display freezes. The model can no longer create or update tasks. One developer confirmed task tools were present and working at 09:56, then silently disappeared at 10:15 while TaskStop and TaskOutput remained. This is the most dangerous failure because work continues without task tracking.
- Account switching triggers the bug on demand
Running /login to switch claude.ai accounts toggles the four task tools in and out reliably. This means the bug is entirely server-side. No local config change, no npm reinstall, no cache clear will fix it.
The Comparison: How Other AI Coding Tools Handle Feature Flags
Claude Code is not the only AI coding tool with server-side feature flags, but it is the only one that silently kills features without telling the user. Here is how the major tools handle remote configuration changes:
| Tool | Remote Flag System | Shows Error When Flagged | User Can Override |
|---|---|---|---|
| Claude Code | GrowthBook (tengu_vellum_ash) | No - tools silently vanish | No |
| Cursor | LaunchDarkly per-user flags | Yes - shows banner in sidebar | Partial (can opt out via settings) |
| GitHub Copilot | Server-side rollout with telemetry | Yes - shows status bar notification | Yes (can fallback to previous model) |
| Windsurf (Codeium) | Canary release per region | Yes - shows feature unavailable toast | No, but provides ETA for restoration |
Claude Code is the outlier here. Every other major AI coding tool provides some user-facing signal when a remote flag disables a feature. Cursor shows a sidebar banner. Copilot shows a status bar notification. Windsurf shows a toast with an ETA. Claude Code silently removes the tools and leaves developers guessing whether they broke something locally.
What This Means for Founders
If you use Claude Code for production workflows, you are running blind when this bug hits. Your CI pipeline may continue executing code, but you lose the live task checklist that tracks what the agent has completed and what is pending. For multi-hour coding sessions, this is a serious risk. One user reported they spent a full day debugging local config changes before discovering the issue was server-side.
Here is what you can do right now:
- Check if you are affected
Run ToolSearch in Claude Code for TaskCreate, TaskGet, TaskList, and TaskUpdate. If it returns zero matches while TaskStop and TaskOutput are present, you are hitting this bug. The issue is not your setup.
- Restart sessions when the flag changes
Close and reopen Claude Code when tools vanish. The flag state may have refreshed by the time you reconnect. This is not a reliable fix, but it worked for some users.
- Do not waste time debugging local config
The root cause is the server-side tengu_vellum_ash flag. Check .claude.json for cached flag values. If the array is empty, your flag state was clear at last refresh but may have changed server-side since.
- Use an external task tracker for critical work
Until Anthropic adds a visible status indicator, treat Claude Code sessions as potentially blind. Use a terminal-based task tracker or a simple markdown checklist alongside Claude Code for anything that matters.
The bottom line: Anthropic shipped a remote kill switch with zero user visibility, and it is costing developers time and money. One user burned an entire week's Fable subscription on this issue. Founders relying on Claude Code for production work should push Anthropic for a visible status indicator when task tools are disabled server-side. In the meantime, do not trust the task display blindly. Verify outside the tool.