The Pillow Book of Niels-Erik Nandal, written in San Francisco.
Lists, kept and dated. A claim links to its evidence or goes as plain observation.
Niels-Erik Nandal is a senior software engineer at Solid in San Francisco.
Things that quicken the heart
7 ·
- The bar's first millimeter off the floor, which tells you everything the next three seconds will confirm.
- Watching a meet total pass 1,000 on a third attempt you almost didn't take.
- A keeper off his line while the ball is still rolling toward your foot.
- Levin mowing, at the moment the scythe begins to swing itself.
- The tokenizer round-tripping a page of Joyce with zero unknowns. Byte fallback, keeping its promise.
niels-gpt tokenizer, byte fallback
- Two generation paths, one fast, one naive, printing identical tokens. The speedup is now legal.
niels-gpt: kv-cache prefill/decode against naive generation
- A stranger's heart rate slowing on schedule, inside a game you built to slow it.
Things I have built
9 ·
The résumé. Every line links to the thing itself.
- A small language model, by hand, in two days — tokenizer, cache, pretraining, chat. It hedges where I hedge.
niels-gpt, working notes
- A reading system where a highlight is a codepoint range into canonical text. When client and server disagree, it refuses to highlight.
Nexus, source
- LLM agents wrapped around a deterministic scheduler. They may explain the plan; they may not touch it.
Factory Simulator, working notes
- A reader that ingests messy PDFs and answers from the text it was given, not the text it wished for.
Fractal Chat, working notes
- A real-time multiplayer Go board, built for a friend, who thanked me by winning on it.
Fractal Go, working notes
- A map of a music model's range: clips clustered by sound, regeneration steered toward the region you point at.
Suno Session Lab, working notes
- Two plain-English walkthroughs of backpropagation, written for the person I was in October.
Neural networks from zero
- A budget app: tax brackets and payroll as typed Effect code, the cash flow drawn as a Sankey diagram. It has no tests.
budget-app, domain layer
- This site: typed data for a CMS, evidence links checked at build, two client components. The colophon confesses.
niels-lab, source
Hateful things (found in codebases)
8 ·
- A mock of the unit under test. The suite is green because it agrees with itself.
- A catch block holding a comment where the plan should be. 'This shouldn't happen.' It is happening now.
- A token cache with no record of which tokenizer wrote it. Every downstream loss curve is a rumor.
niels-gpt caches hard-fail on tokenizer SHA mismatch
- Sentinel tokens spelled as plain strings. 'Hope no one types <|system|>' is not a strategy.
niels-gpt sentinel-token collision checks
- Annotations pinned to line numbers. One re-ingestion later, every highlight decorates the wrong sentence.
Nexus anchors highlights to codepoint ranges in canonical text
Nexus anchors highlights to codepoint ranges in canonical text
- A spotter's hands on a bar that was still moving. Nobody will ever know what the rep was worth.
- An epigraph from The Art of War at the head of a CRUD service.
- A schema change applied by hand in psql, remembered by no one, discovered by the next deploy.
Elegant things
8 ·
- Squat bar path: one vertical line, drawn twice.
- A saucer pass, airborne over one stick and flat on arrival.
- The first sentence of Pride and Prejudice: a thesis, a joke, and the entire plot.
- Dickinson's slant rhyme: the bell you expected, struck slightly off, on purpose.
- Braudel: the sea gets the biography, and kings are demoted to weather.
- RMSNorm: LayerNorm minus the mean, and nothing misses it.
niels-gpt model code
- Weight tying: the matrix that reads is the matrix that speaks.
niels-gpt model code, weight tying
- A citation that still resolves after the document was edited underneath it.
Things that should be small
8 ·
- The blast radius of a deploy. If you cannot draw it, it is not small.
- A pull request. Past the second scroll, the review becomes a skim and the approval becomes a signature.
- The distance between a claim and its proof. Ideally one link, to a trace.
Factory Simulator returns the agent's plan and LLM-call trace with each run
Factory Simulator returns the agent's plan and LLM-call trace with each run
- The gap between two touches of the ball. Possession is overhead.
- The walkout before a heavy squat. Two steps. Every extra step is paid for at the bottom.
- An agent's opportunity to improvise. Pydantic contract in, Pydantic contract out, every invention measured.
Factory Simulator contracts
- A migration. One concern per revision, so the rollback is a sentence instead of a meeting.
- A Dickinson stanza. Four lines, and you are not the person who started reading them.
Rare things
7 ·
- A powerlifting meet that runs on schedule.
- A benched player who agrees with the decision.
- Someone who finishes Durant: eleven volumes, in order, no skimming the Reformation.
- An analysis that matches its preregistration.
- A rewrite that is smaller than the thing it replaced.
- A model card that admits what the model cannot do.
- A secondhand bookshop that has shelved Spengler under Self-Help.
Things that are distant though near
7 ·
- The last two inches of a deadlift that has stopped moving.
- The thousand-pound club, from nine ninety-five.
- War and Peace, third shelf, eye level. I have meant to reread it for ten years and can touch it from this chair.
- The net, in a shootout. Four feet by six, receding as you skate in.
- The end of Ulysses, from anywhere in Ulysses.
- Statistical significance, at p = 0.051.
- Sleep, with the diff still open.
Things now in decline
7 ·
- The two-hour practice nobody films. A proper bag skate produces no content.
- Defending, in pickup soccer. Eleven wingers a side now.
- Commit messages that explain why.
- The personal website. This one included; it knows what it is.
the colophon
- The incentivized choice experiment. Cheaper now to ask a model what humans would want.
- Carrying poems in memory. I keep two Keats odes there against the general trend.
- Hotel gyms with an actual barbell.