git-ecosystem/git-credential-manager · error · Trace2Exception

Missing 'code' in response

Error message

Missing 'code' in response

What it means

GetTwoFactorCodeViaHelperAsync asks the UI helper for a two-factor authentication code and expects a 'code' key in the response dictionary. If the helper returns without it — the 2FA dialog was abandoned or the helper malfunctioned — this Trace2Exception is thrown because no 2FA code can be returned to the caller.

Solutions

  1. Retry authentication and complete the 2FA dialog by entering the code
  2. Verify GCM/helper versions match and reinstall if the helper is outdated or corrupted
  3. Enable GCM_TRACE and run the helper manually to inspect its raw response for errors
  4. Switch to an auth mode that avoids 2FA prompts (PAT with appropriate scopes, or OAuth browser flow)

Example fix

// before
var code = await auth.GetTwoFactorCodeAsync(uri, isSms: true);
UseCode(code);
// after
try
{
    var code = await auth.GetTwoFactorCodeAsync(uri, isSms: true);
    UseCode(code);
}
catch (Trace2Exception ex) when (ex.Message == "Missing 'code' in response")
{
    trace.WriteLine("2FA helper returned no code; aborting or retrying.");
    throw new TwoFactorCancelledException(ex);
}
Defensive patterns

Strategy: try-catch

Validate before calling

// Prefer PAT/OAuth flows that bypass 2FA prompts entirely
// git config --global credential.github.com.gitHubAuthModes browser,pat
code null;

Try / catch

try
{
    string code = await auth.GetTwoFactorCodeAsync(uri, isSms);
}
catch (Trace2Exception ex) when (ex.Message == "Missing 'code' in response")
{
    // 2FA dialog abandoned or helper failed; surface as cancellation and allow retry
    throw new TwoFactorCancelledException(ex);
}

Prevention

When it happens

Trigger: Invoking GetTwoFactorCodeAsync (e.g. during basic-auth 2FA challenge) and the helper's result dictionary lacks 'code': user closed the 2FA prompt, helper crashed, or an incompatible helper version omitted the key.

Common situations: Users skipping the 2FA code entry dialog; helper process failures on machines with broken UI dependencies; SMS 2FA flow interrupted before the code arrives and is entered; legacy helper versions with different output keys.

Related errors

AI-assisted analysis of git-ecosystem/git-credential-manager@e8ce762cd0 (2026-09-11). Data as JSON: /api/errors/3301171dbe932888. Report an issue: GitHub.

Appendix: source

Thrown at src/GitHub/GitHubAuthentication.cs:403

            Context.Console.WriteLine(isSms
                ? "An SMS containing the authentication code has been sent to your registered device."
                : "Use your registered authentication app to generate an authentication code.");

            return await TerminalPrompts.CreateText("Authentication code").ShowAsync(Context.Console);
        }

        private async Task<string> GetTwoFactorCodeViaHelperAsync(bool isSms, string args, string command)
        {
            var promptArgs = new StringBuilder(args);
            promptArgs.Append("2fa");
            if (isSms) promptArgs.Append(" --sms");

            IDictionary<string, string> resultDict = await InvokeHelperAsync(command, promptArgs.ToString(), null);

            if (!resultDict.TryGetValue("code", out string authCode))
            {
                throw new Trace2Exception(Context.Trace2, "Missing 'code' in response");
            }

            return authCode;
        }

        public async Task<OAuth2TokenResult> GetOAuthTokenViaBrowserAsync(Uri targetUri, IEnumerable<string> scopes, string loginHint)
        {
            ThrowIfUserInteractionDisabled();

            var oauthClient = new GitHubOAuth2Client(HttpClient, Context.Settings, targetUri, Context.Trace2);

            // Can we launch the user's default web browser?
            if (!Context.SessionManager.IsWebBrowserAvailable)
            {
                throw new Trace2InvalidOperationException(Context.Trace2,
                    "Browser authentication requires a desktop session");
            }

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