Denis ZeniosDenis Zenios

Notes

Notes on engineering, physics, and software.

Hosting Coding Agents On Your Own Hardware

A local LLM keeps a team's code and data on hardware it owns. The post compares Claude Opus 5.5 with the best open models, DeepSeek V4.1-Flash and Qwen3.8-27B, and works through the hardware each needs, from one RTX PRO 6000 to eight H200s or Mac Studios, how many developers one machine serves, the cost per token, and what running it takes. The key takeaway is that if the number of developers multiplied by $150 to $250 per month exceeds the machine's monthly cost, it might make sense to go local.

Read post 14 min

Teach and Repeat on a Construction Site: Cameras or Lidar?

A construction-site robot learns a route once from a human guide and then drives it alone, through ramps, stairs, changing light and bare concrete rooms. The post compares two ways to build this teach and repeat system, a 360° camera stack and a lidar stack, against the published research, and lands on where each one stands today.

Read post 5 min

Removing Copies By Making Code Unsafe

Why a camera node overflowed the stack on its first frame, what unsafe Rust actually is, and how an unsafe block removed every copy by letting the camera write its frame directly into shared memory.

Read post 4 min

How Internet Censorship Is Bypassed

How censorship works at the protocol level: what an ISP can read in your traffic, why a VPN defeats it, why a VPN can itself be fingerprinted and blocked, and how the proxy protocols used in China, Russia and Iran hide inside ordinary HTTPS.

Read post 4 min

Where Shear Locking Comes From

In pure bending, the displacement of a rod contains squared terms in the coordinates. A linear 8-node brick element cannot build a squared term, and a quadratic 27-node brick can. This is the mathematical source of shear locking in bending problems.

Read post 5 min

Window Scaling flag in TCP

Throughput on a TCP connection is a function of how much data you can have in flight and how long an acknowledgement takes to come back. With window scaling hard coded to 0, the window caps at 65,535 bytes, which is the whole explanation for a 2.62 Mbps ceiling at a 200ms round trip.

Read post 1 min

Cross Platform Networking Application

A team had an encryption algorithm they wanted to test in the field, which meant shim code to run it on every platform they cared about. The hard part turned out to be the shim across operating systems that each do networking their own way, and the fix was starting from the most constrained ecosystem.

Read post 2 min

What AI Can't Replace Yet

On one engagement I wrote not a single line of C++, which raised an obvious question about my own value. The answer came down to the framework: where the shape of the system is already decided, AI writes good code, and where nothing is settled yet, its judgment calls are often wrong.

Read post 2 min

Building an AI Agent You Can Trust to Act on Your Behalf

Getting an AI to generate things is easy. Trusting one to act on someone's behalf, unsupervised, is the hard part. The answer is clear guardrails: the AI does only what it is good at, and code that cannot hallucinate checks its work before anything reaches a stranger's inbox.

Read post 6 min