Using redux-form I’m losing focus after typing the first character

This happens because you’re re-defining renderField as a new component every time you render which means it looks like a new component to React so it’ll unmount the original one and re-mounts the new one.

You’ll need to hoist it up:

const renderField = ({ input, label, type, meta: { touched, invalid, error } }) => (
      <div class={`form-group ${touched && invalid ? 'has-error' : ''}`}>
        <label for={label} className="sr-only">{label}</label>
        <input {...input} placeholder={label} type={type} className="form-control" />
        <div class="text-danger">
          {touched ? error: ''}
        </div>
      </div>
    );

class SignIn extends Component {

  ...

  render() {
    const { message, handleSubmit, prestine, reset, submitting } = this.props;


    return (
      <div className="row">
        <div className="col-md-4 col-md-offset-4">
          <form onSubmit={handleSubmit(this.handleFormSubmit.bind(this))} className="form-signin">
            <h2 className="form-signin-heading">
              Please sign in
            </h2>
            {this.renderAlert()}
            <Field name="email" type="text" component={renderField} label="Email Address" />
            <Field name="password" type="password" component={renderField} label="Password" />
            <button action="submit" className="btn btn-lg btn-primary btn-block">Sign In</button>
          </form>
        </div>
        </div>
    );
  }
}

...