How I Use AI as a Senior Engineer: Where the Day Actually Goes
Not a tools list. After a year of working with agents daily, what changed is where the hours go: specs in the morning, batch review in the afternoon, and the judgment work that never left. A field report from the senior seat.
Everyone wants the tools list. The tools list is the least interesting part.
I have been working with AI agents daily for over a year now, on infrastructure, on applications, on this site, on creative systems that have nothing to do with my day job. The tools changed three times in that year. What stayed constant is more useful to write down: where the hours go now, what I hand off, and what never left my desk.
The day, roughly
Mornings are for specs. Before agents, my morning was often the first implementation push of the day. Now it is writing: what needs to exist, what done looks like, what the constraints are, what the agent should not touch. A good spec takes twenty minutes and saves three hours. A lazy spec costs you the afternoon, because the agent will build the wrong thing with great competence and you will read all of it before you find out.
Then the delegation. Several pieces of work running at once, each one scoped so it can fail independently. This is the part that genuinely did not exist before. One stream is a migration, one is a bug, one is a draft of something I am not sure about yet. Multiples of output. The constraint stops being my typing speed and becomes my attention.
Afternoons are batch review. Everything the agents pushed to staging gets read in one sitting, with the three-pass review I described in my AI code review workflow. Batching matters more than it sounds. Context-switching between writing specs and reading diffs all day shreds both. Separating them keeps each one sharp.
What I hand off
The pattern under everything I delegate: work where the destination is known and the path is mechanical.
Migrations. Scaffolding. Test coverage for code that already works. Sweeps across a codebase, the kind where the same change needs to happen forty times with small variations. Config plumbing. First drafts of documentation. The bottom ninety percent of any task whose top ten percent I care about.
I also hand off investigation, which surprised me. "Find every place this assumption appears" is agent work now. The agent reads faster than I do and does not get bored on file thirty. What it brings back still needs my eyes, but the gathering is no longer my job.
What stays
Deciding what to build. That one never moves. The cost of writing code fell through the floor and the cost of knowing what to write did not budge, which is the whole story of how AI is changing software engineering compressed into one sentence.
Naming. Architecture. The judgment call on whether a change belongs at this layer or two layers down. Taste, which sounds soft until you watch its absence compound across a hundred agent-written diffs. And reading. Every line that ships, I read. The day I stop reading my own systems is the day my mental model starts rotting, and the mental model is the senior part of senior engineer.
The part nobody talks about
There is a physical cost to working at this multiple. The pressure behind the eyes after a long parallel session, the way the speed bends your sense of time. I wrote about it honestly in Working at the Frontier, and I bring it up here because no workflow advice is complete without it. Water. Breaks. The heat is information. Work near the forge without standing in the fire.
What seniority means now
Here is the thing I would tell a younger engineer. The agents did not compress the seniority ladder. They moved it.
A junior with agents produces volume. A senior with agents produces volume that holds up, because fifteen years of watching systems fail in production gives you a verification instinct no model has. You know where the bodies are buried because you buried some of them. That instinct, applied to ten times the throughput, is what the senior seat is now: less performing, more conducting, and the conductor is responsible for every note.
The cognitive load is real and it is different from the old load. I wrote about that trade in The Cognitive Cost of Modern Software Engineering. The short version: you trade the strain of producing for the strain of judging, and judging all day is its own discipline.
If you want the operating manual version of all this, it is in The AI-Assisted Engineering HOWTO, the working method for directing an agent through your repo is in Agentic AI Development, and the full hub of this work lives at AI development. The honest place to start, though, is smaller: pick one mechanical task tomorrow, write a real spec for it, hand it off, and read every line that comes back. The workflow grows from there.