FAQ and troubleshooting

The panel says “Waiting for the deffector agent”

The panel is open but the page has not answered. Check, in order:

1. The import. import '@deffector/agent' must be in the code that runs in the page — ideally the first line of the entry file. Reload the page after adding it.
2. A production build. Every entry of the agent is a no-op in production on purpose (“Production build? The agent is a no-op there on purpose.”). Use the dev server.
3. The extension was reloaded (after npm run build). Content scripts of the old version are orphaned: reload the page and reopen DevTools.
4. An address other than localhost. There the extension needs your permission once: the panel shows “deffector has no access to host” — press Allow on this site.
5. An iframe. The content script runs only in the top frame; an app inside an iframe is not connected.

The toolbar icon of the extension tells the same thing at a glance: grey and “No deffector agent on this page” in its popup, or coloured with “effector version detected” and the sid coverage.

There is no deffector tab in DevTools

The extension is not loaded, or DevTools was opened before it was. Check chrome://extensions (or about:debugging in Firefox), then close and reopen DevTools. Firefox removes temporary add-ons on restart — load it again.

The first actions are missing from the log

The agent records for 10 seconds after load and then pauses until a panel connects (Health: “History before the panel opened was not recorded”). Open DevTools first and reload the page, or set attachDeffector({ whileClosed: 'record' }). See Performance.

New transactions stopped appearing

• Is recording paused? The status in the toolbar then reads “recording paused”; press the record button.
• Is a saved filter with Do not record matching them?
• Did another tool take over effector's inspector? effector has a single inspector slot; effector-logger and @effector/redux-devtools-adapter use it too. Health reports Another tool took over the effector inspector — press Reclaim, or import the other tool before @deffector/agent.

Some units are missing, or the panel shows two different effectors

The agent hooks the copy of effector it imports. If the bundle has two copies (a linked package, a monorepo with two versions), units of the other copy are invisible. Dedupe effector in the bundler — with Vite, resolve: { dedupe: ['effector', 'effector-react'] }. In Next.js keep effector in serverExternalPackages for the server.

Units are called $store@index.js:97, or Health says “stores have no sid”

The code is compiled without effector/babel-plugin or @effector/swc-plugin. deffector works, with less detail; see Without the babel/swc plugin.

Time travel fires my watchers and effects

The app is in global mode (no fork()) or renders without a deffector adapter, so jumps write values in place. Use fork() and DeffectorProvider — see Time travel.

Skip, “Silently, via fork” or “Replay in a new scope” behave differently in my app

They need a scope that deffector can switch: fork() plus an adapter. Without it Skip and Silently, via fork are disabled, and replay writes the initial state in place.

The page is covered and I cannot click

The app shows the past and the page is locked so a click cannot change it. Press Esc in the page or Back to present, or Allow clicks to work in a branch. lockPast: false turns the cover off.

A trace replays with skipped steps

The receiving build does not have some units (the compatibility check lists them in red), or their sids moved and they were matched by name (yellow). Record and replay on the same commit when you can, and set attachDeffector({ build }) so the check warns about different builds.

“Own handler” in Override effects throws an error

The handler code is compiled in the page with new Function; a Content Security Policy without unsafe-eval blocks it. Use the other override modes, or relax the CSP in development.

The standalone app sees no agent

• The process must call attachDeffectorNode() before it creates units, and must not run with NODE_ENV=production (or pass skipInProduction: false).
• [deffector] no WebSocket implementation — Node older than 22: pass WebSocket from the ws package.
• Another machine or a phone: start the app with --host 0.0.0.0 and use your computer's address in url.
• Several agents: pick one in the Agent selector above the panel.

Does deffector send my data anywhere?

No. The agent talks to the panel in the same browser (through the extension) or to the standalone app you run yourself, which listens on 127.0.0.1 by default. deffector has no server of its own. A trace leaves your machine only when you send the file, and values under secret-looking keys are masked in it.

Can I leave the import in production code?

Yes. In production builds every entry point resolves to a no-op with the same API, and @deffector/agent/node does nothing when NODE_ENV=production.

Which versions are supported?

effector 22.6 or newer (developed against 23.4.4, also checked on 22.8.6); React 16.8+, Vue 3.0+, Solid 1.3+; Chrome and Edge 116+, Firefox 140+. The full table, with Node, TypeScript and bundlers, is in Installation → Requirements.