Failed to update config file ${file} with ${stringify(obj)}:

Error message

Failed to update config file ${file} with ${stringify(obj)}: ${e.message}

What it means

Thrown by insertValuesInConfigFile (config-file-updater.ts:22-24) when fs.writeFile of the AST-transformed cypress.config file rejects. The catch wraps the underlying error message with the target file path and the stringified values object (via stringify-object) for debuggability. This is purely a WRITE failure; structural/parse problems with the config throw a separate COULD_NOT_UPDATE_CONFIG_FILE error earlier (via errors.get in insertValueInJSString). So hitting this message specifically means the file was parsed and transformed successfully but could not be saved.

Source

Thrown at packages/data-context/src/util/config-file-updater.ts:23

import type { namedTypes } from 'ast-types'
import Debug from 'debug'
import fs from 'fs-extra'
import stringify from 'stringify-object'

const debug = Debug('cypress:data-context:config-file-updater')

interface ErrorObj {
  get(type: string, ...args: any[]): Error
}

export async function insertValuesInConfigFile (file: string, obj: {}, errors: ErrorObj) {
  const fileContents = await fs.readFile(file, { encoding: 'utf8' })

  const transformedFileContents = await insertValueInJSString(fileContents, obj, errors)

  debug('transformedFileContents %s', transformedFileContents)
  await fs.writeFile(file, transformedFileContents).catch((e) => {
    throw new Error(`Failed to update config file ${file} with ${stringify(obj)}: ${e.message}`)
  })
}

export async function insertValueInJSString (fileContents: string, obj: Record<string, any>, errors: ErrorObj): Promise<string> {
  const ast = parse(fileContents, { plugins: ['typescript'], sourceType: 'module' })

  let objectLiteralNode: namedTypes.ObjectExpression | undefined

  function handleExport (nodePath: NodePath<namedTypes.CallExpression, any> | NodePath<namedTypes.ObjectExpression, any>): void {
    if (nodePath.node.type === 'CallExpression'
        && nodePath.node.callee.type === 'Identifier') {
      const functionName = nodePath.node.callee.name

      if (isDefineConfigFunction(ast as File, functionName)) {
        return handleExport(nodePath.get('arguments', 0))
      }
    }

View on GitHub (pinned to 0d85fdc912)

Solutions

Check write permissions on the config file and its directory (chmod/chown) and remove any read-only flag.
Close editors or tools that may be locking the file (especially on Windows) and retry.
Free disk space if ENOSPC, and confirm the project directory still exists and is writable.
Read the underlying e.message in the thrown error — it carries the exact errno (EACCES/EBUSY/ENOSPC) that points to the fix.

Example fix

// before
await insertValuesInConfigFile(file, obj, errors) // opaque write failure

// after
import fs from 'fs-extra'
try {
  await fs.access(file, fs.constants.W_OK)
} catch {
  throw new Error(`Config file ${file} is not writable; check permissions/locks`)
}
await insertValuesInConfigFile(file, obj, errors)

Defensive patterns

Strategy: try-catch

Validate before calling

// Verify the config file is writable before attempting the update
import fs from 'fs-extra'

async function isConfigWritable(file: string): Promise<boolean> {
  try {
    await fs.access(file, fs.constants.W_OK)
    return true
  } catch {
    return false
  }
}

if (!(await isConfigWritable(file))) {
  throw new Error(`Cannot write config file ${file}; check permissions/locks`)
}
await insertValuesInConfigFile(file, obj, errors)

Try / catch

try {
  await insertValuesInConfigFile(file, obj, errors)
} catch (e) {
  // e.message already includes file path, stringified obj, and underlying errno.
  // Parse the tail (EACCES/EBUSY/ENOSPC) to pick the right remediation.
  const errno = /EACCES|EBUSY|ENOSPC|EISDIR|EPERM/.exec(e.message)?.[0]
  reportToUser(`Could not save cypress.config: ${errno ?? 'write error'}`, e.message)
}

Prevention

Keep cypress.config.{js,ts} writable by the user running Cypress; avoid checking it in read-only or with restrictive perms.
On Windows, ensure no editor or file watcher holds an exclusive lock before Cypress tries to update the config.
Free disk space and confirm the project directory is on a writable mount.
Read the underlying errno embedded in the message — it pinpoints permissions vs lock vs space vs path problems.

When it happens

Trigger: fs.writeFile(file, transformedFileContents) rejects — EACCES (no write permission), EISDIR (path is a directory), ENOSPC (disk full), EBUSY/EPERM (file locked on Windows by an editor or watcher), or the directory was removed between read and write.

Common situations: cypress.config.js is read-only or owned by another user; an editor or file watcher holds an exclusive lock on the file (Windows); disk/full partition; the project root is on a read-only mount; a security/antivirus tool blocks writes; the file path became invalid after a rename.

Related errors

AI-assisted analysis of cypress-io/cypress@0d85fdc912 (2026-08-12). Data as JSON: /api/errors/c6377292edacc871. Report an issue: GitHub.