ACP runtime environment key ${JSON.stringify(key)} cannot be

Error message

ACP runtime environment key ${JSON.stringify(key)} cannot be configured in both credentialEnv and env.

What it means

A key may not appear in both credentialEnv (vars handled as credentials) and env (static subprocess values). Putting a credential-shaped variable into env would persist its secret value in plain config, so the overlap is rejected eagerly.

Source

Thrown at packages/harness-acp/src/v1/implementation.ts:98

  validateForwardEnvironment({ forwardEnv: implementation.credentialEnv });
  validateEnvironment({ env: implementation.env });
  const forwardedKeys = new Set(implementation.forwardEnv ?? []);
  const credentialKeys = new Set(implementation.credentialEnv ?? []);
  for (const key of credentialKeys) {
    if (forwardedKeys.has(key)) {
      throw new Error(
        `ACP runtime environment key ${JSON.stringify(key)} cannot be configured in both forwardEnv and credentialEnv.`,
      );
    }
  }
  for (const key of Object.keys(implementation.env ?? {})) {
    if (forwardedKeys.has(key)) {
      throw new Error(
        `ACP runtime environment key ${JSON.stringify(key)} cannot be configured in both forwardEnv and env.`,
      );
    }
    if (credentialKeys.has(key)) {
      throw new Error(
        `ACP runtime environment key ${JSON.stringify(key)} cannot be configured in both credentialEnv and env.`,
      );
    }
  }
}

export function createImplementationManifest({
  implementation,
}: {
  implementation: ACPImplementation;
}): string | undefined {
  const { source } = implementation;
  if (source.type === 'install-command') return undefined;
  if (source.type === 'npm-locked') {
    return source.packageJson;
  }
  return (
    JSON.stringify(

View on GitHub (pinned to 69428b1f8b)

Solutions

Remove the key from env and let credentialEnv forward it from the host environment.
Store the secret in the host environment or a secret manager rather than embedding it in settings.
Scan config for the duplicated key before constructing the implementation.

Example fix

// before
createACPV1({ env: { GITHUB_TOKEN: 'ghp_x' }, credentialEnv: ['GITHUB_TOKEN'] });
// after
createACPV1({ credentialEnv: ['GITHUB_TOKEN'] }); // value supplied from host env

Defensive patterns

Strategy: validation

Validate before calling

const creds = new Set(implementation.credentialEnv ?? []);
const dup = Object.keys(implementation.env ?? {}).filter(k => creds.has(k));
if (dup.length > 0) throw new Error(`Secrets must not be inlined in env: ${dup.join(', ')}`);

Type guard

function envAndCredentialAreDisjoint(env, credentialEnv) {
  const cr = new Set(credentialEnv ?? []);
  return Object.keys(env ?? {}).every(k => !cr.has(k));
}

Try / catch

try {
  const impl = createACPV1(settings);
} catch (err) {
  if (err instanceof Error && err.message.includes('both credentialEnv and env')) {
    console.error('Remove the secret from env; supply it via the host environment');
  }
  throw err;
}

Prevention

Never inline secret values in env; always use credentialEnv with host-supplied values
Scan configs for secret-shaped keys (TOKEN, KEY, SECRET) before inlining values
Store credentials in a secret manager instead of settings files

When it happens

Trigger: createACPV1 where a key in implementation.env also exists in implementation.credentialEnv, e.g. env: {GITHUB_TOKEN: 'ghp_...'} plus credentialEnv:['GITHUB_TOKEN'].

Common situations: Hardcoding a token into env for local testing while credentialEnv is also configured, or generated configs that add secrets to env instead of referencing the host value.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/05146e29b9ac61a7. Report an issue: GitHub.