Just to get that straight: Legacy code is practically always large code with countless hidden requirements, and with insufficient or no tests and without documentation. But which works somehow. Any change needs to meet numerous unwritten requirements, and it can often only be tested in the real world. If you have N features, you have N*(N-1)/2 interactions between two features, so it is quadratic growth with N. This is why it is very hard and time-consuming to change.

It shouldn't be that way, but writing large software - especially in commercial environments - is often like climbing a high roof on a ladder, and then throwing away that ladder. Modifications are only incremental, and usually not documented. Incremental modifications are one of the only two working engineering approaches for software we know - and the only one used for commercial software.

The other way - which is used in aviation for example - is to specify, document, and test everything, right from the start.

Now the problem is you can rewrite legacy stuff as much as you like, but it is near impossible to make sure that large changes work. Because in order to do that, you would need to run the tests that do not exist, or create tests from specifications and requirements which do not exist either.

And GenAI tools are not going to change that. The agentic tools kinda work by filling in missing requirements with assumptions and average observed stuff. It can generate reams of code, fast. But while this kinda works for a small phone app, it doesn't for large complex stuff. If the code does not fit in the head of one person working for months on it, it will never fit in the context window of an LLM.

Don't worry, guys. I am sure he adds "make no mistakes" to every prompt. No review necessary, push straight to prod.

What's he gonna do for the rest of the 23 months?

So they're replacing battle-tested unmaintainable old code written by humans with bad unreleased unmaintainable new code written by ai.

Both are unmaintainable. What's the punch line?? Is this not the onion?

... and suddenly, overnight, claude or whatever will have very detailed, intricate knowledge around Cisco's hardware, almost like it's regurgitating internal documentation. Hm.

Ignore, for a second, the use of AI here.

How huge a screw up is it just to send a guy off to work on a project alone for 2 years. Can you imagine the amount of time that should be spent in code reviews looking at something someone has spent a full 2 years on? You're now going to be asking senior devs to spend months of their lives doing nothing but code reviews. And, if you skip the code reviews that's suicide.

We all know that in 2 years Cisco is still going to be using their legacy codebase. There's not a chance in hell this will work. Just announcing this like it is a sane thing to do advertises their dysfunction.

It's possible that he will find some low-hanging fruit and be able to rewrite some library code. But, really, when rewriting something old and bloated, the main thing you can do to add value is to remove code. And, AI agents are famous for their ability to generate vast amounts of code, not to get rid of it.

The absolute best case here is that this guy wastes 2 years of his life, and Cisco has some kind of deal where these "unlimited AI tokens" come at some fixed price so that this project costs Cisco only $1m or so. Then, the project's a failure, they only lose a bit of money, and they can maybe learn from the experience. But, do you really make an announcement about a project that's only going to run you $1m in costs? I doubt it. This is probably Cisco setting fire to $50m or more. And, given that they announced the project like it was a good idea, can they afford to just admit it failed? With that kind of sunk cost, they're probably going to feel a lot of pressure to achieve something positive with the stunt... so something here is going to be integrated into their codebase.

"Claude, rewrite all of these repos but better"

Done, and done!

This should be entertaining

Hey I'm rooting for the guy. If in two years they release this mostly generated code it should be entirely public domain. Public domain slop is better for me then hostage making spyware.

Holy shit, this really seems like something that you shouldn’t announce publicly

Legacy code is still around for a reason. It’s not usually just a matter of refactoring it, but the business logic tied around it all.

Good luck lmao. Cisco will be underwater in years if they actually commit to this.

Cisco just handed a 27 year old unlimited AI tokens and the keys to 98% of its codebase. Somewhere, a senior engineer is quietly updating their resume. Rewriting code is easy. Discovering why that horrifying 1998 workaround exists is the actual final boss.

Future breaking news: Cisco hardware used in massive botnet attack.

Is unlimited tokens a big deal? I don’t really get what this means…

Well this is concerning. Our entire network runs Cisco.

had founded a translation startup

Doesn't Cisco know any networking and firmware experts, with extensive legacy code knowledge, who could vibe code through a well thought out plan?

I don't know... Have you provisioned Cisco equipment before? It feels like the quality can only go up.

(But no, obviously this will end terribly unless they're incredibly careful. It's possible, but unlikely.)

What happens if the price of those tokens suddenly skyrockets because the provider now knows your entire operation is relying on this one guy vibing?

"Welcome back to another episode of the premier game-show of the 21st century: 'What Could Possibly Go Wrong?' Man, do we have a great one for you guys tonight..."

So, don’t buy Cisco. Got it.

lol

When I was 27 I’d been coding for 15 years, so age alone shouldn’t be the red flag.

What is going to be a pop problem is the insane number of Chesterton fences stomped down that fuck everything over, or things that look like they can be optimized out or use cases you don’t think actually happen.

See rust core utils for an example of extremely well trodden and well reviewed software that ran into these issues for years. Not that it’s a bad effort, it’s an inherently hard task.

That is peak level CEO magic thinking