Dtyjlui

Update your resume, you are being replaced.

You're being fed corporate newspeak designed to keep you cowed until they can replace you. You also tipped your hand by mentioning you had an offer on the table. You'd better take it.

The new CEO is planning on taking the company in a new direction, and you're not part of his plan.

All the signs are there:

After signing the contract the CEO congratulated me, stating that I was to be their (sole) Lead developer.

and

The old CEO denied that he once called me a Lead developer, and confirmed that the new developer and I will have equal areas of responsibility, at the same time confirming that I have the responsibilities of a Lead / Architect until the new developer has been hired!

In other words, he said you're the lead, then said he never said that, then said that you're still the lead until you're not.

Like I said, corporate newspeak.

I told my current CEO that I have a job offer from a huge company with lots of potential

Take this new job. Telling your boss (or your boss's boss) you have another offer will generally get you laid-off or fired. If they valued your work, they would have brought you on full-time.

I want to use this to negotiate a new contract with my current company

So essentially you are threatening to quit unless they give you what you want. See this from their perspective. You've just gotten a better job so you can strong-arm them into a deal that's in your favor.

What are you going to do when you're not happy again in 6 months? Probably get another job offer and re-re-negotiate the contract.

Realistically, forcing a company to re-negotiate because of offers never works, and generally leads to animosity between the company and the employee.

I'm not entirely convinced that we know you are being replaced.

It's easy to call someone a "lead developer" when they're the only developer and there's nobody else to lead. Inevitably, a successful company will look to grow its engineering team, and it's possible that your company simply doesn't want to use a hierarchy in that team — flat structures aren't unheard of, particularly between just two people who are working on completely different things — or perhaps they would prefer to have a hierarchy in principle, but don't feel that you are ready to be a manager (and also don't want to put you in the position of suddenly reporting to someone else).

None of this is inherently "bad" and I wouldn't necessarily jump to the conclusion that this is a negative thing. Having a new colleague at work could be exciting and you don't inherently lose anything as a result, particularly as you never signed anything that indicates you had something to lose by this and as you will not be working on the same tasks.

Unfortunately, your reaction to this news has been less than endearing. Not only have you balked to the company's CEO about being joined by a new engineering partner, but you've strong-armed him/her with threats about leaving to what you've described as a better deal. If anything, it is this reaction that may have soured your relationship with this company, weakened your position, and may be cause for you to follow up on that threat.

If you ever get the chance to go back in time, I'd stick with it and see how the new teammate works out. It could be a wonderful opportunity to develop software with someone and to learn from each other, and to perhaps transition to a true leadership role as the team continues to grow and sub-ordinates are assigned varyingly to both you and your new partner. You can always leave later if it doesn't work out for you.

If you have an offer that pays twice as much, take it. You may not care about money, but once you have wife, children etc. You will kick yourself for not having taking the job and having lots of money in the bank to buy a house, educate the kids etc.

And if someone else is willing to pay twice as much then clearly your current place is ripping you off.

I've been in this situation before and part of the personality it takes to create a startup is "bigger, shinier, and newer". If it wasn't they could just work an existing job for much less effort and risk.

This new developer will be seen as superior to you despite the promise of a flat structure. It is likely your accomplishments will be credited to him from his first day of employment.

Unless you have a sufficient equity stake in writing, I would move on to the big company. Note that the promise of an equity stake will very likely not be fulfilled, so anything like that is worthless.

It sucks, is not logical, but it is the way it is. Adding to this is that the old CEO denied calling you the lead developer.

Move on, and make some real money. Be willing to consult with this company if needed, but make your rates very high. For example, if the new company is offering you 50/hour (or the salary equivalent), I would consult with the old company for no less than 200/hr and probably more like 500/hr.

but at the same time I really like my colleagues and the tasks at my current job.

This is never a good reason to reject a better opportunity ( which you admittedly did ). You need to remember that over time people will come and go and tasks will change. The next time you receive a great offer you should accept it. Your current situation does not look like it will end well despite your currently great colleagues and tasks.

Whenever management presents a change that appears to affect your responsibilities (either formally or informally), it is important for you to ask them to clarify exactly why they are making this change, and what your responsibilities will be after this change. This should include a formal description of what you are responsible for, who you report to, your title, etc.

This is also a great time for you to make a case for yourself - to remind them of your value, to argue to you keep the work you like and try to move some of the work you don't onto others. Think of it is another negotiation: they want something from you (to accept this change) so you should try to extract something from them in return.

Sometimes, the change might be because they have decided to replace you, but want a period of overlap. By asking them to clarify you role, and seeing how amenable they are to some of your requests, you can try to suss that out.

Companies make changes all the time: because they are growing and need new people, because they need people with more and different experiences, etc. Most people which make great "first" developers at a start up do not have the skills or experience to lead a team of a 1000 technologists, and so as the firm grows, especially if it grows rapidly, they need to find a nice niche for themselves.

The old CEO denied that he once called me a Lead developer

That is all you need to know. But wait... there's more:

[CEO said] I have the responsibilities of a Lead / Architect until the new developer has been hired

Right.

CEO is willing to call you the Lead/Architect, but only while you're the only one.

This is the important bit: when the new developer arrives you no longer have a title.

Note that they are saying this before they hire the new person - they don't even know who they are hiring, but they do know that you will not have a title when that person starts work.

I don’t see how that could work

Correct, it won't.

More accurately stated: it won't work out well for you.

I told my current CEO that I have a job offer from a huge company with lots of potential, the company is offering me twice what I’m currently making.

Yeah... maybe that will work out well for you.

18 months from now if you think this was the right move, please update the question with that information.

This next quote sounds really good, and maybe it is true - I have no reason to doubt you.

Money doesn’t motivate me much

Okay, but it should - if you want to advance.

Here's why: when you're applying for a new position and the new company finds out that you're making half market rate for the position... it smells wrong to them. Unless you're coming from a non-profit or academia into industry or you are coming from a place where the standard of living is really inexpensive, that new company may (will) get the impression that you didn't deserve the title. They will question your worth because if you were worth more, that other company would have bumped your pay to at least 75% of current market rate (which is 150% of what you're making now).

I'm not saying money should be your primary motivation... that path can (does) lead to misery.

But it should be a motivation.

It feels unfair and I’m a bit unsure about what to do. I have no problem finding a new job

I agree. It is unfair to you.

You need a new job, the sooner the better.