Tanstack Devtools

Sub-skill of tanstack. Owns the dev-only, opt-in debugging panel that ships with TanStack: a floating host (@tanstack/react-devtools) that other devtools (router today, more later) plug into, plus the Vite plugin (@tanstack/devtools-vite) that injects the runtime which makes "click an element in the browser → jump to its source file" work. The point: tighten the iPad-over-LAN debug loop when explicitly requested — see what's broken, click straight to the source line.

When to invoke

• Adding a new TanStack devtool surface (a Query devtool, a Form devtool, etc.) — they all plug into <TanStackDevtools> as a plugins[] entry.
• Diagnosing why the floating devtool button isn't showing in bun run dev.
• Confirming the production bundle has zero devtool residue (the Pillar 4 / iPad-LAN bundle hygiene check).
• Understanding the lazy + DEV-gate pattern dean-stack uses to keep devtools out of dist/.
• Anyone proposing click-to-react-component, @locator/runtime, or another browser-→-source tool — @tanstack/devtools-vite already does this. Don't add a competitor.

Owns

The dev-only mount of <TanStackDevtools> in apps/web/app/lib/root-shell.tsx, the opt-in tanstackDevtools() Vite plugin in apps/web/vite.config.ts, the import.meta.env.DEV + VITE_ENABLE_TANSTACK_DEVTOOLS + lazy() tree-shaking pattern, and the policy that all three devtool packages stay in devDependencies.

Defers to

• tanstack (parent) — version pin and dispatch.
• tanstack-router-routing — the <TanStackRouterDevtoolsPanel /> reads its data from the router instance authored there.
• react-19-primitives — lazy() + <Suspense fallback={null}> is the React-19 idiom that makes the dev gate render-safe.
• react-compiler-rules — the side-channel rule applies: the devtool host mounts once at the root boundary, never inside a render function.

Dean-stack rules

• Devtools are opt-in in dev, and absent in production. The default bun run dev page must stay close to production behavior: no root devtools host, no @tanstack/devtools-vite DOM source annotations, and no sidecar event-bus unless VITE_ENABLE_TANSTACK_DEVTOOLS=true is set. The pattern in apps/web/app/lib/root-shell.tsx is:

  const TanStackDevtools =
    import.meta.env.DEV && import.meta.env.VITE_ENABLE_TANSTACK_DEVTOOLS === "true"
      ? lazy(async () => { ... })
      : null;
  

  Vite's static-replacement of import.meta.env.DEV lets dead-code elimination drop the entire lazy() branch (and its dynamic imports) from the production bundle. The env flag prevents default dev-load freezes from source-link instrumentation. Verify with grep -r '@tanstack/react-devtools' apps/web/dist/client/assets/ — must return zero hits.
• @tanstack/devtools-vite is a Vite plugin, not a runtime, and it is opt-in. It belongs in vite.config.ts behind the same VITE_ENABLE_TANSTACK_DEVTOOLS === "true" guard. The plugin annotates DOM nodes with source metadata and starts source-linking machinery during vite dev; do not enable it by default.
• Devtool components are NOT dean-stack components and do NOT need a Storybook story (Pillar 1 exemption). They're third-party panels; the "no component without a story" rule applies to components authored under apps/<name>/app/components/, not to dev-time host panels mounted at the root.
• Devtools introduce zero app-level state (Pillar 3). Their internal panel-state (open/closed, active tab) lives in the devtool's own scope; never persist any of it through atomWithIDB.
• Pillar 4 (CLI-gate-first): all three packages are devDependencies, never dependencies. The gate enforces this by ensuring the production bundle stays free of devtool symbols.
• VITE_ENABLE_TANSTACK_DEVTOOLS=true bun run dev is when devtools live. Plain bun run dev keeps devtools off. bun run preview (which Playwright app tests usually drive) runs the production build, so devtools are absent there. That's correct — app tests assert app behavior, not devtool UI.
• The headliner is browser→source linking. @tanstack/devtools-vite's devtools() plugin is the reason this skill exists: clicking a rendered element in the running browser opens the source file at the exact line in your editor. That's the iPad-LAN debug payoff.

Patterns

vite.config.ts — opt into the plugin first

// apps/web/vite.config.ts
import { devtools as tanstackDevtools } from "@tanstack/devtools-vite";
import { tanstackStart } from "@tanstack/react-start/plugin/vite";

function enableTanStackDevtools(): boolean {
  return process.env.VITE_ENABLE_TANSTACK_DEVTOOLS === "true";
}

export default defineConfig({
  plugins: [
    ...(enableTanStackDevtools() ? tanstackDevtools() : []),
    ...sharedPlugins(),
    tanstackStart({ /* ... */ }),
  ],
});

Keep the conditional plugin first when enabled. The plugin is a no-op for vite build, but it still changes the dev browser runtime, so it must remain opt-in.

root-shell.tsx — lazy + DEV/env-gate the host

import { type ReactNode, Suspense, lazy } from "react";

const TanStackDevtools =
  import.meta.env.DEV && import.meta.env.VITE_ENABLE_TANSTACK_DEVTOOLS === "true"
    ? lazy(async () => {
        const [{ TanStackDevtools: Host }, { TanStackRouterDevtoolsPanel }] = await Promise.all([
          import("@tanstack/react-devtools"),
          import("@tanstack/react-router-devtools"),
        ]);
        return {
          default: () => (
            <Host
              config={{ position: "bottom-right" }}
              plugins={[{ name: "TanStack Router", render: <TanStackRouterDevtoolsPanel /> }]}
            />
          ),
        };
      })
    : null;

function RootComponent(): ReactNode {
  return (
    <html lang="en">
      <head>{/* ... */}</head>
      <body>
        {/* ... app content ... */}
        {TanStackDevtools ? (
          <Suspense fallback={null}>
            <TanStackDevtools />
          </Suspense>
        ) : null}
        <Scripts />
      </body>
    </html>
  );
}

Why this shape: production sees null → the {TanStackDevtools ? ... : null} JSX becomes null → the dynamic imports never get bundled. Default dev also sees null unless the opt-in flag is set, keeping source-link instrumentation away from normal game iteration.

Adding a new TanStack devtool plugin

When a new package ships (e.g. a Query devtool, a Form devtool), it joins the existing plugins[] array on the host:

plugins={[
  { name: "TanStack Router", render: <TanStackRouterDevtoolsPanel /> },
  { name: "TanStack Query", render: <TanStackQueryDevtoolsPanel /> }, // future, hypothetical
]}

Not relevant for dean-stack today (no Query — no server, IDB-first).

Verifying zero production residue

bun run build
grep -r '@tanstack/react-devtools' apps/web/dist/client/assets/   # zero hits
grep -r 'TanStackRouterDevtoolsPanel' apps/web/dist/client/assets/ # zero hits
grep -r 'devtools-vite' apps/web/dist/client/assets/              # zero hits

If any return hits, the DEV gate isn't tree-shaking — investigate before merging.

Anti-patterns

• Don't enable TanStack Devtools by default. Both the Vite plugin and the React host require VITE_ENABLE_TANSTACK_DEVTOOLS=true. Always-on devtools can inject source metadata into the live DOM and stall default dev loads.
• Don't import the devtool packages at the top of __root.tsx or root-shell.tsx without the DEV/env gate. Static imports always end up in the bundle; the lazy + ternary is the only safe shape.
• Don't put the devtool packages in dependencies. They're dev tools — devDependencies only. The gate doesn't catch this on its own; reviewers must.
• Don't add click-to-react-component, @locator/runtime, or another browser-→-source tool. @tanstack/devtools-vite already provides this. A second one is duplicate weight in node_modules and a new place for source-link logic to drift.
• Don't mount <TanStackDevtools> inside a route component or anywhere besides the root. Mounting it deeper means it gets unmounted on navigation and loses its panel state.
• Don't write a Storybook story for the devtool host (Pillar 1 exemption). Devtools aren't a dean-stack component; they're a third-party panel whose UI is already tested upstream.
• Don't reach for useEffect to mount the host. The lazy() + render shape is the right one — useEffect introduces a one-frame mount delay and risks the side-channel rule (devtool mutates DOM).
• Don't add <TanStackRouterDevtoolsPanel /> outside of the host's plugins[] array. It's a panel, not a standalone overlay; mounting it bare loses the docked-panel UX.

Triggers on

TanStackDevtools, TanStackRouterDevtoolsPanel, devtools-vite, tanstack devtools, click to source, browser to editor, router devtools, dev panel