There's no goal mentioned in this article as why 98% of the code needs rewriting.

Rewrite it in service of… what exactly?

As much as I dislike AI, having worked on Cisco gear for years, I can't imagine AI can put out a worse product. If the re-write is full of bugs and security holes and static SSH keys, then it has not changed at all.

So there's a real risk that Cisco might become history in just a few years. Taking that kind of risk with a rather unproven technology has to be psychosis. Or is that kind of belief a form of Religion?

Does this one engineer have the domain knowledge to know WHY the old code was written the way it was, and what the graybeards would have done differently if they could start again now?

Otherwise he's just going to replicate all the legacy bugs and questionable design decisions.

Is this like a PR piece for the guy? It's odd to see him singled out in a piece that would be normally be about the company, the CEO or the decision itself.

Misleading title, someone should fix it. 98% of legacy code. Check out the full title of the article.

We have an embedded system in one of product offerings that was largely developed using a bunch of “antiquated” technologies (over the past twenty years) and over the past year the two software devs that maintained it have retired. This normally would have big problem, but the entire codebase was re-written, documented, and modernized in a matter of about 3 months (for about $20k in tokens, and a mid level developer spending 50% of their time on it over that period). So it doesn’t surprise me to think a company like Cisco has piles of situations like this.

I guess Cisco decided it has not alienated its customers enough till now & its finally time to get people running for the woods - at least if those peoples would like their network to continue working.

There also seems to be some weird hero-worship from the CEO, directed at this 27-YO engineer? Like, "he is the one who can save us."

Unless they also have 750K tests like sqlite do, I can't imagine this will go well, even if/especially if the legacy code warrants a refactor.

rewriting code is the easy part

it's the testing in real world usage to shake out all the edge cases and bugs that's hard and that you can't just write unit tests for

Well they say the last 20% of the work takes 80% of the time so if he gets the prototype in 4 weeks, which I have no doubt he will be able to do, and assuming that prototype is the first 80% of work, then he should be able to do this in 20 weeks. He even has some margin! Looking forward to seeing the results

I mean, this is going to be easy. I've worked on Cisco gear before and this will be a simple job for AI. The big question is what the goal is... so you've rewritten new C++ code or ported to a newer version of Linux? Or you've unified the codebase of the Catalyst + Meraki switches?

Not clear to me what he's doing. Re-implement switching? Simplify features? Reduce LoC? Add test coverage? Either way, AI in that world will be helpful. I'm sure it'll spot all kinds of problems in opaque drivers that are hard to follow from MF specs.

'98% of the company's legacy code' is very vague. How many code bases? How each code base is connected to any supported Cisco product? How many KLOC the company's legacy code?

I think Cisco is an interesting use case for AI, because it's code, probably:

-Works according to a defined specification

-Within the bounds of that specification, has a lot of code written to optimize speed, cost, latency, etc - all measureable goals

-Written in c, with all it's weakness

-Given limitless engineering work, some could be ported to better hardware

-the new system could be automatically compared to the old system for functional correctness

All those factors fit well with agent based development.

Btw, many of them are true in general to embedded systems.

I suspect we are approaching a world where this makes sense to do annually. Opus 5.5 is good enough to improve on most codebases, and Opus 7 will no doubt be good enough to improve on that.

"According to a report by Fortune" - here's that report: https://fortune.com/2026/10/30/cisco-president-jeetu-patel-g...

Fortune's source was the CEO himself:

> “I’ve given him unlimited tokens because he’s going to refactor code,” Patel told Fortune at a small roundtable dinner. “So I’m like, you can go, you can go nuts.”

I think that Fortune story is better than the Tom's Hardware one. It ties the Cisco anecdote into a larger trend of some people deliberately hiring younger, less experienced developers for their AI projects - because they are more likely to be "AI native".

Cisco that powers more than half of the backbone of all things online? Are we trying to lose control of AGI as soon as it emerges??

He'll pull it off, get feature complete, and spend a year or two with better models as they are released ironing it out. We just did an experiment, in four weeks generated 3500 commits, 200k sloc with a 1:1.15 ratio of production to test code and it all works very well. We are well on our way from 10x to 100x.