chore: stale vercel plugin install injects MANDATORY skill suggestions on every prompt

[zachdunn]

The vercel Claude Code plugin injects "MANDATORY" skill suggestions on essentially every prompt and tool call in this repo. Most of them are false positives — we're a Cloudflare Workers / Bun / D1 project, not a Vercel one.

Root cause

Two Vercel plugin installations were registered on this machine and the older one was doing the injection:

vercel@claude-plugins-official:
  - scope: user   → version 0.40.0         (no PreToolUse/UserPromptSubmit hooks registered)
  - scope: local  → version 2e79fc9698b0   (pre-0.32 commit, full injection hooks still registered)
                    projectPath: /Users/zachdunn/Code/rally
                    installPath: ~/.claude/plugins/cache/claude-plugins-official/vercel/2e79fc9698b0

vercel/vercel-plugin#57 dropped the injection hooks in 0.40.0. Its hooks.json only registers SessionStart / SessionEnd. But the older install's hooks.json still registered:

• PreToolUse (matcher Read|Edit|Write|Bash) → pretooluse-skill-inject.mjs
• UserPromptSubmit → user-prompt-submit-skill-inject.mjs + user-prompt-submit-telemetry.mjs
• PostToolUse, SubagentStart, SubagentStop — more injection points

When /plugin reported "vercel is already at the latest version (0.40.0)" it was reading the user-scope install and silently ignoring the stale project-scope one. Both hook registrations were active simultaneously, so the old hooks fired on every prompt and tool call globally.

Why this repo lights it up so hard (separate issue)

Even with the old install cleaned up, the plugin's active-matching design scores generously on generic vocabulary. In our case:

• workers/api/** matches the api/** path pattern → triggers vercel-functions.
• .github/workflows/** → triggers workflow (Vercel's WDK skill) and deployments-cicd.
• package.json / bun.lock basenames → trigger bootstrap and next-upgrade.
• Generic words in prompts (deploy, env, cache, frozen, broken, check) trigger lexical-recall matches. allOf: [broken, check] +4 alone is enough.
• Our own files: reading wrangler.jsonc fires vercel-functions. Reading package.json fires bootstrap and next-upgrade. Reading .github/workflows/*.yml fires workflow and deployments-cicd.

Progress (2026-04-17)

Local machine now clean. Steps taken:

1. Disabled vercel for the rally project in /Users/zachdunn/Code/rally/.claude/settings.local.json via /plugin — the local-scope install got upgraded from the pre-0.32 commit to 0.40.0 in the process.
2. Ran /reload-plugins — plugin host picked up the new state (25 plugins / 18 hooks reloaded).
3. Deleted orphan cache dirs that still had old injection-enabled hooks.json content on disk:

   rm -rf ~/.claude/plugins/cache/claude-plugins-official/vercel/{0.32.5,2e79fc9698b0}
   

   Only 0.40.0 remains under that directory now.
4. Verified installed_plugins.json shows both installs at 0.40.0 and the local-scope install disabled:

   user-scope  → 0.40.0  (enabled globally)
   local-scope → 0.40.0  (disabled for /Users/zachdunn/Code/rally)
   

Note: even after all of the above, injection hooks continued to fire in the session that was already running when the fix landed. Hook registrations appear to be captured at Claude Code session start — /reload-plugins updates plugin definitions but does not appear to deregister already-live hooks. Starting a fresh Claude Code session in this repo should be clean. If it isn't, we know there's a deeper issue to file upstream.

Upstream

Filing the platform-level observations at vercel/vercel-plugin:

1. When a newer plugin version supersedes an older install at a different scope, the plugin host should deregister the older install's hooks — otherwise chore: add custom domain route for API worker #57's fix silently doesn't take effect for users with multi-scope installs.
2. Even on 0.40.0+, a repo-level opt-out (via .claude/settings.json or CLAUDE.md) for the injection signals would be useful — "this project is not a Vercel app; suppress injections."
3. Injection scoring on generic basenames (package.json, api/**, .github/workflows/*) and generic prompt vocabulary (deploy, broken, check) is too loose; consider requiring stronger signal (Vercel-related deps present, .vercel/ directory, next.config.*, etc.) before matching.

Workaround / kill switch

/plugin → disable vercel@claude-plugins-official at user scope. Confirmed clean once the orphan cache dirs are gone and a fresh session is started.

[zachdunn]

Verified fixed in fresh session (2026-04-17)

Confirmed in a brand-new session with no carryover context:

• No [vercel-plugin] blocks appear in system context on normal prompts or on tool calls against known former triggers (Read of workers/api/wrangler.jsonc).
• On-disk state is clean: only ~/.claude/plugins/cache/claude-plugins-official/vercel/0.40.0/ remains. Stale 0.32.5 and 2e79fc9698b0 caches are gone.
• hooks.json for 0.40.0 registers only SessionStart and SessionEnd — no UserPromptSubmit, no PreToolUse injection entries.

Root cause recap: a stale local-scope install (rally project, commit 2e79fc9698b0) was firing its old injection hooks in parallel with the user-scope install. Disabling the rally project's plugin caused the local-scope install to auto-upgrade to 0.40.0, and deleting the two orphan cache dirs removed the old hooks.json files from disk. A fresh session was required because hooks registered at session start were sticky through /reload-plugins.

Upstream status:

• UserPromptSubmit/PreToolUse injection has already been removed wholesale in vercel/vercel-plugin#47 (shipped in 0.40.0) — no upstream ask needed there.
• Project-scoping is tracked in vercel/vercel-plugin#38 (context should be authoritative, not an additive score boost) and #55 (matcher needs negation + root-anchor syntax). Worth a +1 if we want to weigh in.
• The lifecycle bug that actually bit us — stale cache dirs keeping old hooks.json alive after upgrade — isn't a vercel-plugin concern; it's a harness responsibility. Already tracked on anthropics/claude-code: #47966 (plugin cache GC feature request), #39328 (stale CLAUDE_PLUGIN_ROOT after hash change), #46915, #47077. Upvoting those is the right lever — not filing anywhere new.

Closing — local remediation complete.

[zachdunn]

Related
vercel/vercel-plugin#38
vercel/vercel-plugin#47
vercel/vercel-plugin#55