facebook/react · error · Error

414

414

Error message

Did not expect this call in production. This is a bug in React. Please file an issue.

What it means

remountFiber() rebuilds a subtree by swapping in a new work-in-progress fiber, marking the old one for deletion, and restarting work - behavior used by DevTools force-remount and DEV-only recovery paths. Its body runs only under if (__DEV__); the else branch guarantees a production bundle never calls it. This throw in production means __DEV__ was evaluated inconsistently across the bundle: a call site compiled in DEV mode reached a helper compiled in prod mode.

Source

Thrown at packages/react-reconciler/src/ReactFiberBeginWork.js:3932

      prevSibling.sibling = newWorkInProgress;
    }

    // Delete the old fiber and place the new one.
    // Since the old fiber is disconnected, we have to schedule it manually.
    const deletions = returnFiber.deletions;
    if (deletions === null) {
      returnFiber.deletions = [current];
      returnFiber.flags |= ChildDeletion;
    } else {
      deletions.push(current);
    }

    newWorkInProgress.flags |= Placement | PlacementDEV;

    // Restart work from the new fiber.
    return newWorkInProgress;
  } else {
    throw new Error(
      'Did not expect this call in production. ' +
        'This is a bug in React. Please file an issue.',
    );
  }
}

function checkScheduledUpdateOrContext(
  current: Fiber,
  renderLanes: Lanes,
): boolean {
  // Before performing an early bailout, we must check if there are pending
  // updates or context.
  const updateLanes = current.lanes;
  if (includesSomeLane(updateLanes, renderLanes)) {
    return true;
  }
  // No pending update, but because context is propagated lazily, we need
  // to check for a context change before we bail out.

View on GitHub (pinned to eafeac097b)

Solutions

1. Set NODE_ENV once, globally, for the whole build and rebuild from a clean cache
2. Run npm ls react react-dom and remove duplicate or mismatched copies
3. Check bundler aliases - every react/react-dom import must resolve to the same production artifact
4. If you maintain a custom React build, verify __DEV__ is replaced with false everywhere in the prod output

Example fix

// before - per-entry define (can disagree across chunks)
define: { 'process.env.NODE_ENV': JSON.stringify(mode) }

// after - one global define for the entire production build
define: { 'process.env.NODE_ENV': JSON.stringify('production') }

# Build-time validation: no development React artifacts may ship
! grep -rl "Remount failed" dist/ 2>/dev/null | grep -q . \
  || { echo 'dev React branch in bundle - rebuild with NODE_ENV=production'; exit 1; }

When it happens

Trigger: A production bundle where the bundler defines NODE_ENV/__DEV__ per-chunk instead of globally; importing a development React entry point in one chunk and the production artifact in another; custom bundler aliases resolving some react imports to react.development.js.

Common situations: Monorepos where one package builds React in dev mode and another consumes the prod artifact; staging builds shipped with mixed mode; SSR bundles mixing node-development and browser-production React; hand-rolled React builds with broken defines.

Related errors

• 349
• 156
• Your app (or one of its dependencies) is using an outdated J
• Unknown Fiber. Needs to be a function component to inspect h
• The should not be any remaining suspense node children if th

AI-assisted analysis of facebook/react@eafeac097b (2026-08-21). Data as JSON: /api/errors/d293a4b8a5bb139e. Report an issue: GitHub.