facebook/react · error · Error

Should have a root instance for a committed root. This is a

Error message

Should have a root instance for a committed root. This is a bug in React DevTools.

What it means

Post-commit flush invariant in the DevTools backend: component console logs queued during passive effects (needsToFlushComponentLogs) arrive for a root that rootToFiberInstanceMap no longer contains. The message itself states this is a bug in React DevTools - the root's mirror was dropped (unmounted or reset) while queued logs still referenced it.

Source

Thrown at packages/react-devtools-shared/src/backend/fiber/renderer.js:5031

  }

  function handlePostCommitFiberRoot(root: FiberRoot) {
    if (isProfiling && rootSupportsProfiling(root)) {
      if (currentCommitProfilingMetadata !== null) {
        const {effectDuration, passiveEffectDuration} =
          getEffectDurations(root);
        // $FlowFixMe[incompatible-use] found when upgrading Flow
        currentCommitProfilingMetadata.effectDuration = effectDuration;
        // $FlowFixMe[incompatible-use] found when upgrading Flow
        currentCommitProfilingMetadata.passiveEffectDuration =
          passiveEffectDuration;
      }
    }

    if (needsToFlushComponentLogs) {
      const rootInstance = rootToFiberInstanceMap.get(root);
      if (rootInstance === undefined) {
        throw new Error(
          'Should have a root instance for a committed root. This is a bug in React DevTools.',
        );
      }
      // We received new logs after commit. I.e. in a passive effect. We need to
      // traverse the tree to find the affected ones. If we just moved the whole
      // tree traversal from handleCommitFiberRoot to handlePostCommitFiberRoot
      // this wouldn't be needed. For now we just brute force check all instances.
      // This is not that common of a case.
      bruteForceFlushErrorsAndWarnings(rootInstance);
    }
  }

  function handleCommitFiberRoot(
    root: FiberRoot,
    priorityLevel: void | number,
  ) {
    const nextFiber = root.current;

View on GitHub (pinned to eafeac097b)

Solutions

1. Update React DevTools to the latest release (this class of bug gets patched by release)
2. Reload the page with DevTools attached to re-establish root tracking
3. Report with a repro of root unmount plus passive-effect logging
4. If embedding the backend, skip the flush when the root is missing instead of crashing

try {
  backend.handlePostCommitFiberRoot(renderer, root);
} catch (e) {
  if (/Should have a root instance for a committed root/.test(e.message)) {
    unregisterRoot(root); // root was torn down; drop queued logs
  } else throw e;
}

When it happens

Trigger: Passive effects logging after the root was unmounted in the same commit window; roots removed between handleCommitFiberRoot and handlePostCommitFiberRoot; multiple roots where one is torn down while logs are pending.

Common situations: Apps that unmount roots (micro-frontends, test harnesses, hot reload) while components log in cleanup/passive effects; DevTools attached across root teardown.

Related errors

• The should not be any remaining suspense node children if th
• There should always be an Offscreen Fiber child in a hydrate
• Did not expect a host hoistable to be the root
• A dehydrated Suspense node should not have a content Fiber.
• Encountered a dehydrated Suspense boundary that was previous

AI-assisted analysis of facebook/react@eafeac097b (2026-08-21). Data as JSON: /api/errors/9cab33e8785d5476. Report an issue: GitHub.