Computational Complexity and other fun stuff in math and com­puter sci­ence from Lance Fortnow and Bill Gasarch

New U. S laws de­signed to pro­tect mi­nors are pulling mil­lions of adult Americans into manda­tory age-ver­i­fi­ca­tion gates to ac­cess on­line con­tent, lead­ing to back­lash from users and crit­i­cism from pri­vacy ad­vo­cates that a free and open in­ter­net is at stake. Roughly half of U.S. states have en­acted or are ad­vanc­ing laws re­quir­ing plat­forms — in­clud­ing adult con­tent sites, on­line gam­ing ser­vices, and so­cial me­dia apps — to block un­der­age users, forc­ing com­pa­nies to screen every­one who ap­proaches these dig­i­tal gates.

“There’s a big spec­trum,” said Joe Kaufmann, global head of pri­vacy at Ju­mio, one of the largest dig­i­tal iden­tity-ver­i­fi­ca­tion and au­then­ti­ca­tion plat­forms. He ex­plained that the patch­work of state laws vary in tech­ni­cal de­mands and com­pli­ance ex­pec­ta­tions. “The reg­u­la­tions are mov­ing in many dif­fer­ent di­rec­tions at once,” he said.

Social me­dia com­pany Discord an­nounced plans in February to roll out manda­tory age ver­i­fi­ca­tion glob­ally, which the com­pany said would rely on ver­i­fi­ca­tion meth­ods de­signed so fa­cial analy­sis oc­curs on a user’s de­vice and sub­mit­ted data would be deleted im­me­di­ately. The pro­posal quickly drew back­lash from users con­cerned about hav­ing to sub­mit self­ies or gov­ern­ment IDs to ac­cess cer­tain fea­tures, which led Discord to de­lay the launch un­til the sec­ond half of this year.

“Let me be up­front: we knew this roll­out was go­ing to be con­tro­ver­sial. Any time you in­tro­duce some­thing that touches iden­tity and ver­i­fi­ca­tion, peo­ple are go­ing to have strong feel­ings,” Discord chief tech­nol­ogy of­fi­cer and co-founder Stanislav Vishnevskiy wrote in a Feb. 24 blog post.

Websites offering adult con­tent, gam­bling, or fi­nan­cial ser­vices of­ten rely on full iden­tity ver­i­fi­ca­tion that re­quires scan­ning a gov­ern­ment ID and match­ing it to a live im­age. But most of the ver­i­fi­ca­tion sys­tems pow­er­ing these check­points — of­ten run by spe­cial­ized iden­tity-ver­i­fi­ca­tion ven­dors on be­half of web­sites — rely on ar­ti­fi­cial in­tel­li­gence such as fa­cial recog­ni­tion and age-es­ti­ma­tion mod­els that an­a­lyze self­ies or video to de­ter­mine in sec­onds whether some­one is old enough to ac­cess con­tent. Social me­dia and lower-risk ser­vices may use lighter es­ti­ma­tion tools de­signed to con­firm age with­out per­ma­nently stor­ing de­tailed iden­tity records.

Vendors say a chal­lenge is bal­anc­ing safety with how much fric­tion users will tol­er­ate. “We’re in the busi­ness of en­sur­ing that you are ab­solutely keep­ing mi­nors safe and out and able to let adults in with as lit­tle fric­tion as pos­si­ble,” said Rivka Gewirtz Little, chief growth of­fi­cer at iden­tity-ver­i­fi­ca­tion plat­form So­cure. Excessive data col­lec­tion, she added, cre­ates fric­tion that users re­sist.

Still, many users per­ceive manda­tory iden­tity checks as in­va­sive. “Having an­other way to be forced to pro­vide that in­for­ma­tion is in­tru­sive to peo­ple,” said Heidi Howard Tandy, a part­ner at Berger Singerman who spe­cial­izes in in­tel­lec­tual prop­erty and in­ter­net law. Some users may at­tempt workarounds — in­clud­ing pre­paid cards or al­ter­na­tive cre­den­tials — or turn to unau­tho­rized dis­tri­b­u­tion chan­nels. “It’s go­ing to cause a piracy sit­u­a­tion,” she added.

In many im­ple­men­ta­tions, ver­i­fi­ca­tion ven­dors — not the web­sites them­selves — process and re­tain the iden­tity in­for­ma­tion, re­turn­ing only a pass-fail sig­nal to the plat­form.

Gewirtz Little said So­cure does not sell ver­i­fi­ca­tion data and that in light­weight age-es­ti­ma­tion sce­nar­ios, where plat­forms use quick fa­cial analy­sis or other sig­nals rather than gov­ern­ment doc­u­men­ta­tion, the com­pany may store lit­tle or no in­for­ma­tion. But in fuller iden­tity-ver­i­fi­ca­tion con­texts, such as gam­ing and fraud pre­ven­tion that re­quire ID scans, cer­tain adult ver­i­fi­ca­tion records may be re­tained to doc­u­ment com­pli­ance. She said So­cure can keep some adult ver­i­fi­ca­tion data for up to three years while fol­low­ing ap­plic­a­ble pri­vacy and purg­ing rules.

Civil lib­er­ties’ ad­vo­cates warn that con­cen­trat­ing large vol­umes of iden­tity data among a small num­ber of ver­i­fi­ca­tion ven­dors can cre­ate at­trac­tive tar­gets for hack­ers and gov­ern­ment de­mands. Ear­lier this year, Discord dis­closed a data breach that ex­posed ID im­ages be­long­ing to ap­prox­i­mately 70,000 users through a com­pro­mised third-party ser­vice, high­light­ing the se­cu­rity risks as­so­ci­ated with stor­ing sen­si­tive iden­tity in­for­ma­tion.

In ad­di­tion, they warn that ex­pand­ing age-ver­i­fi­ca­tion sys­tems rep­re­sent not only a us­abil­ity chal­lenge but a struc­tural shift in how iden­tity be­comes tied to on­line be­hav­ior. Age ver­i­fi­ca­tion risks ty­ing users’ “most sen­si­tive and im­mutable data” — names, faces, birth­days, home ad­dresses — to their on­line ac­tiv­ity, ac­cord­ing to Molly Buckley, a leg­isla­tive an­a­lyst at the Electronic Frontier Foundation.  “Age ver­i­fi­ca­tion strikes at the foun­da­tion of the free and open in­ter­net,” she said.

Even when ven­dors promise to safe­guard per­sonal in­for­ma­tion, users ul­ti­mately rely on con­trac­tual terms they rarely read or fully un­der­stand. “There’s lan­guage in their terms-of-use poli­cies that says if the in­for­ma­tion is re­quested by law en­force­ment, they’ll hand it over. They can’t confirm that they will al­ways for­ever be the only en­tity who has all of this in­for­ma­tion. Every­one needs to un­der­stand that their base­line in­for­ma­tion is not some­thing un­der their con­trol,” Tandy said.

As more plat­forms route age checks through third-party ven­dors, that con­cen­tra­tion of iden­tity data is also cre­at­ing new le­gal ex­po­sure for the com­pa­nies that rely on them. “A com­pany is go­ing to have some of that in­for­ma­tion pass­ing through their own servers,” Tandy said. “And you can’t of­fload that kind of li­a­bil­ity to a third party.”

Companies can dis­trib­ute risk through con­tracts and in­sur­ance, she said, but they re­main re­spon­si­ble for how iden­tity sys­tems in­ter­act with their in­fra­struc­ture. “What you can do is have re­ally good in­sur­ance and re­quire re­ally good in­sur­ance from the en­ti­ties that you’re con­tract­ing with,” she said.

Tandy also cau­tioned that re­ten­tion promises can be more com­plex than they ap­pear. “If they say they’re hold­ing it for three years, that’s the min­i­mum amount of time they’re hold­ing it for,” she said. “I wouldn’t feel com­fort­able trust­ing a com­pany that says, ‘We delete every­thing one day af­ter three years.’ That is not go­ing to hap­pen,” she added.

Federal and state reg­u­la­tors ar­gue that age-ver­i­fi­ca­tion laws are pri­mar­ily a re­sponse to doc­u­mented harms to mi­nors and in­sist the rules must op­er­ate un­der strict pri­vacy and se­cu­rity safe­guards.

An FTC spokesper­son told CNBC that com­pa­nies must limit how col­lected in­for­ma­tion is used. While age-ver­i­fi­ca­tion tech­nolo­gies can help par­ents pro­tect chil­dren on­line, the agency said firms are still bound by ex­ist­ing con­sumer pro­tec­tion rules gov­ern­ing data min­i­miza­tion, re­ten­tion, and se­cu­rity. The agency pointed to ex­ist­ing rules re­quir­ing firms to re­tain per­sonal in­for­ma­tion only as long as rea­son­ably nec­es­sary and to safe­guard its con­fi­den­tial­ity and in­tegrity.

My LinkedIn and Twitter feeds are full of screen­shots from the re­cent Forbes ar­ti­cle on Cursor claim­ing that Anthropic’s $200/month Claude Code Max plan can con­sume $5,000 in com­pute. The rel­e­vant quote:

Today, that sub­si­diza­tion ap­pears to be even more ag­gres­sive, with that $200 plan able to con­sume about $5,000 in com­pute, ac­cord­ing to a dif­fer­ent per­son who has seen analy­ses on the com­pa­ny’s com­pute spend pat­terns.

This is be­ing shared as proof that Anthropic is haem­or­rhag­ing money on in­fer­ence. It does­n’t sur­vive ba­sic scrutiny.

I’m fairly con­fi­dent the Forbes sources are con­fus­ing re­tail API prices with ac­tual com­pute costs. These are very dif­fer­ent things.

Anthropic’s cur­rent API pric­ing for Opus 4.6 is $5 per mil­lion in­put to­kens and $25 per mil­lion out­put to­kens. At those prices, yes - a heavy Claude Code Max 20 user could rack up $5,000/month in API-equivalent us­age. That maths checks out.

But API pric­ing is not what it costs Anthropic to serve those to­kens.

The best way to es­ti­mate what in­fer­ence ac­tu­ally costs is to look at what open-weight mod­els of sim­i­lar size are priced at on OpenRouter - where mul­ti­ple providers com­pete on price.

Qwen 3.5 397B-A17B is a good com­par­i­son point. It’s a large MoE model, broadly com­pa­ra­ble in ar­chi­tec­ture size to what Opus 4.6 is likely to be. Equally, so is Kimi K2.5 1T params with 32B ac­tive, which is prob­a­bly ap­proach­ing the up­per limit of what you can ef­fi­ciently serve.

Here’s what the pric­ing looks like:

The Qwen 3.5 397B model on OpenRouter (via Alibaba Cloud) costs _$0.39_ per mil­lion in­put to­kens and _$2.34_ per mil­lion out­put to­kens. Compare that to Opus 4.6′s API pric­ing of $5/$25. Kimi K2.5 is even cheaper at $0.45 per mil­lion in­put to­kens and $2.25 out­put.

And this ra­tio holds for cached to­kens too - DeepInfra charges $0.07/MTok for cache reads on Kimi K2.5 vs Anthropic’s $0.50/MTok.

These OpenRouter providers are run­ning a busi­ness. They have to cover their com­pute costs, pay for GPUs, and make a mar­gin. They’re not char­i­ties. If so many can serve a model of com­pa­ra­ble size at ~10% of Anthropic’s API price and re­main in busi­ness, it is hard for me to be­lieve that they are all tak­ing enor­mous losses (at ~the ex­act same rate range).

If a heavy Claude Code Max user con­sumes $5,000 worth of to­kens at Anthropic’s re­tail API prices, and the ac­tual com­pute cost is roughly 10% of that, Anthropic is look­ing at ap­prox­i­mately $500 in real com­pute cost for the heav­i­est users.

That’s a loss of $300/month on the most ex­treme power users - not $4,800.

However, most users don’t come any­where near the limit. Anthropic them­selves said when they in­tro­duced weekly caps that fewer than 5% of sub­scribers would be af­fected. I per­son­ally use the Max 20x plan and prob­a­bly con­sume around 50% of my weekly to­ken bud­get and it’s hard to use that many to­kens with­out get­ting se­ri­ous RSI. At that level of us­age, the maths works out to roughly break-even or prof­itable for Anthropic.

The real story is ac­tu­ally in the ar­ti­cle. The $5,000 fig­ure comes from Cursor’s in­ter­nal analy­sis. And for Cursor, the num­ber prob­a­bly is roughly cor­rect - be­cause Cursor has to pay Anthropic’s re­tail API prices (or close to it) for ac­cess to Opus 4.6.

So to pro­vide a Claude Code-equivalent ex­pe­ri­ence us­ing Opus 4.6, it would cost Cursor ~$5,000 per power user per month. But it would cost Anthropic per­haps $500 max.

And the real is­sue for Cursor is that de­vel­op­ers want to use the Anthropic mod­els, even in Cursor it­self. They have real “brand aware­ness”, and they are gen­uinely bet­ter than the cheaper open weights mod­els - for now at least. It’s a real co­nun­drum for them.

Obviously Anthropic is­n’t print­ing free cash­flow. The costs of train­ing fron­tier mod­els, the enor­mous salaries re­quired to hire top AI re­searchers, the multi-bil­lion dol­lar com­pute com­mit­ments - these are gen­uinely mas­sive ex­penses that dwarf in­fer­ence costs.

But on a per-user, per-to­ken ba­sis for in­fer­ence? I be­lieve Anthropic is very likely prof­itable - po­ten­tially very prof­itable - on the av­er­age Claude Code sub­scriber.

The “AI in­fer­ence is a money pit” nar­ra­tive is mis­in­for­ma­tion that ac­tu­ally plays into the hands of the fron­tier labs. If every­one be­lieves that serv­ing to­kens is wildly ex­pen­sive, no­body ques­tions the 10x+ markups on API pric­ing. It dis­cour­ages com­pe­ti­tion and makes the moat look deeper than it is.

If you want to un­der­stand the real eco­nom­ics of AI in­fer­ence, don’t take API prices at face value. Look at what com­pet­i­tive open-weight model providers charge on OpenRouter. That’s a much closer proxy for what it ac­tu­ally costs to run these mod­els - and it’s a frac­tion of what the fron­tier labs charge.

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Background: Why I put my whole life into a sin­gle data­base

Back in 2019, I started col­lect­ing all kinds of met­rics about my life. Every sin­gle day for the last 3 years I tracked over 100 dif­fer­ent data types - rang­ing from fit­ness & nu­tri­tion to so­cial life, com­puter us­age and weather.

Ideas or sug­ges­tions?

I’d love to hear from you!

The goal of this pro­ject was to an­swer ques­tions about my life, like

How does liv­ing in dif­fer­ent cities af­fect other fac­tors like fit­ness, pro­duc­tiv­ity and hap­pi­ness?

How does sleep af­fect my day, my fit­ness level, and hap­pi­ness?

How does the weather, and the dif­fer­ent sea­sons af­fect my life?

Are there any trends over the last few years?

How does com­puter time, work and hours in meet­ings af­fect my per­sonal life?

Since the start of this pro­ject, I col­lected ~380,000 data points, with the biggest data sources be­ing:

Naturally af­ter I started col­lect­ing this data, I wanted to vi­su­al­ize what I was learn­ing, so I cre­ated this page. Initially, the do­main where­is­Fe­lix.to­day (now re­named to how­is­Fe­lix.to­day) started as a joke to re­spond to friends ask­ing when I’d be back in NYC or San Francisco. Rather than send them my sched­ule, I’d point them to this do­main. However, now it’s more than my lo­ca­tion: it’s all of me.

Use a sin­gle data­base, owned and hosted by me, with all the data I’ve col­lected over the years

Be able to eas­ily add and re­move ques­tions on the fly, as I learn what’s ben­e­fi­cial to track

Full con­trol of how the data is vi­su­al­ized

Works well for fre­quent fly­ers with mixed time zones

I se­lected 48 graphs to show pub­licly on this page. For pri­vacy rea­sons, and to pre­vent any ac­ci­den­tal data leaks, the graphs be­low are snap­shots taken on a given day.

Visualization of the num­ber of data en­tries in FxLifeSheet over the last 10 years, and where the data came from.

Initially (2014) the only data used was RescueTime and Foursquare Swarm lo­ca­tion data

Once I started the FxLifeSheet pro­ject in April 2019, I man­u­ally tracked , rang­ing from mood, sleep, so­cial life, to fit­ness data

I was able to ret­ro­spec­tively fetch the his­toric weather data based on my lo­ca­tion on a given day

I also im­ple­mented other im­port sources, like fetch­ing my his­toric weight and the num­ber of steps from Apple Health

Days tracked my Mood to be Happy & Excited

On days where I tracked my mood to be “happy” & “excited”, the fol­low­ing other fac­tors of my life were af­fected

50% more likely to have pushed my com­fort zone

44% more likely to have med­i­tated that day

33% more ex­cited about what’s ahead in the fu­ture

31% more likely to drink al­co­hol that day (parties, good friends and such)

28% more time spent read­ing or lis­ten­ing to au­dio books

26% more likely to have worked on in­ter­est­ing tech­ni­cal chal­lenges

20% more likely to have learned some­thing new that day

45% less time spent in video & au­dio calls that day

All flights taken within the last 7 years, tracked us­ing Foursquare Swarm, an­a­lyzed by JetLovers.

The stats clearly show the im­pact of COVID start­ing 2020

Sunday has been my “commute” day, fly­ing be­tween San Francisco, New York City and Vienna

All flights taken within the last 7 years, tracked us­ing Foursquare Swarm, an­a­lyzed by JetLovers.

Frankfurt - Vienna was the flight con­nect­ing me with most US air­ports

Germany is high up on the list due to lay­overs, even though I did­n’t spend ac­tu­ally much time there

Inspired by Your Life in Weeks by WaitButWhy, I use Google Sheets to vi­su­al­ize every week of my life, with lit­tle notes on what city/​coun­try I was in, and other life events that have hap­pened.

The first 14 years I did­n’t re­ally get much done

I can highly rec­om­mend tak­ing a few weeks (or even months) off be­tween jobs (if you have the pos­si­bil­ity)

Shades of blue in­di­cate my full-time em­ploy­ments

You can cre­ate your own ver­sion us­ing my tem­plate

Average daily steps mea­sured through the iPhone’s Apple Health app. I de­cided against us­ing SmartWatch data for steps, as SmartWatches have changed over the last 8 years.

I walked a to­tal of steps over last 8 years

I walk more than twice as much when I’m in New York, com­pared to any other city

In NYC I had the gen­eral rule of thumb to walk in­stead of tak­ing pub­lic tran­sit when­ever it’s less than 40 min­utes. I used that time to call friends & fam­ily, or lis­ten to au­dio books

Although Vienna is very walk­a­ble, the ex­cel­lent pub­lic tran­sit sys­tem with sub­way trains com­ing every 3-5 min­utes, has caused me to walk less

San Francisco was al­ways scary to walk

This graph clearly shows the cor­re­la­tion be­tween my body weight and my sleep­ing/​rest­ing heart rate. The rest­ing heart rate is mea­sured by the Withings ScanWatch while sleep­ing, and in­di­cates how hard your heart has to work while not be­ing ac­tive. Generally the lower the rest­ing heart rate, the bet­ter.

I started my lean bulk (controlled weight gain com­bined with 5 work­outs a week) in August 2020

My rest­ing heart rate went from 58bpm to 67bpm () from August 2020 to March 2021 with a weight gain of (+19lbs) as part of a con­trolled lean-bulk com­bined with a 5-day/week work­out rou­tine

The spike in rest­ing heart rate in July & August 2021 was due to bars and night­clubs open­ing up again in Austria

After a night of drink­ing, my rest­ing/​sleep­ing heart rate was about 50% higher than af­ter a night with­out any al­co­hol

The spike in rest­ing heart rate in Oct/Nov/Dec 2021 was due to hav­ing bron­chi­tis and a cold/​flu, not get­ting cor­rect treat­ment early enough

How healthy have I been over the Years?

Every day I an­swered the ques­tion on how healthy I felt. In the graph, the yel­low color in­di­cates that I felt a lit­tle un­der the weather, not sick per se. Red means I was sick and had to stay home. Green means I felt en­er­gized and healthy.

During the COVID lock­downs I tended to stay health­ier. This may be due to not go­ing out, no heavy drink­ing, less close con­tact with oth­ers, etc. which re­sulted in me hav­ing bet­ter sleep.

Usually dur­ing ex­ces­sive trav­el­ing I get sick (cold/flu)

Q4 2021 I had bron­chi­tis, how­ever, I did­n’t know about it at the time and did­n’t get proper treat­ment

Overall I’m quite prone to get­ting sick (cold/flu)

Days with more than 4 Alcoholic Drinks

On days where I had more than 4 al­co­holic bev­er­ages (meaning I was par­ty­ing), the fol­low­ing other fac­tors were af­fected

21x more likely to dance

80% more likely to take a nap the day of, or the day af­ter

40% warmer tem­per­a­tures, and 40% less pre­cip­i­ta­tion. There weren’t many op­por­tu­ni­ties for par­ties in Winter due to lock­downs in the last 2 years. Also, peo­ple are more mo­ti­vated to go out when it’s nice out­side.

My FxLifeSheet bot asks me 4 times a day how I’m feel­ing at the mo­ment.

This graph groups the en­tries by month, and shows the % of en­tries for each value (0 - 5) with 5 be­ing very ex­cited, and 0 be­ing wor­ried.

I de­signed the ranges so that 0 or 5 are not en­tered as much. 0 is ren­dered as dark green at the top, whereas 5 is ren­dered as light green at the bot­tom.

For pri­vacy rea­sons I won’t get into some of the de­tails on why cer­tain months were worse than oth­ers.

Every Swarm check-in over the last 7 years vi­su­al­ized on a map, in­clud­ing the ac­tual trip (flight, drive, etc.)

Every Swarm check-in over the last 7 years vi­su­al­ized, zoomed in

Each time I did a check-in at a place (e.g. Coffee, Restaurant, Airport, Gym) on Foursquare Swarm at a given city, this is tracked as a sin­gle en­try.

Each check-in at a given city is counted as a sin­gle en­try, grouped by years

2018 and 2019 I lived in New York City

The longer it’s been since I moved away from Austria, the more time I ac­tu­ally spent back home in Austria for vis­its and va­ca­tions

2020 clearly shows the im­pact of COVID

Each check-in at a given cat­e­gory is tracked, and summed up over the last years

In 2020 and 2021, check-ins at Offices went down to zero due to COVID, and a dis­trib­uted work setup

Airports be­ing the #4 most vis­ited cat­e­gory was a sur­prise, but is ac­cu­rate. A to­tal of 403 air­port check-ins, whereas a flight with a lay­over would count as 3 air­port check-ins

Earlier in my life, I did­n’t al­ways check into ‘commute’ places like pub­lic tran­sit and su­per mar­kets

Number of Foursquare Swarm check-ins on each quar­ter over the last 10 years. I did­n’t use Foursquare Swarm as se­ri­ously be­fore 2015. Once I moved to San Francisco in Q3 2015 I started my habit of check­ing into every point of in­ter­est (POI) I visit.

Q3 2015 I moved to San Francisco, how­ever I could­n’t use Swarm yet, since my move was a se­cret un­til the of­fi­cial an­nounced at the Twitter Flight con­fer­ence

Q2 2020 clearly shows the im­pact of COVID with Q3 al­ready be­ing open in Austria

Q3 2021 the vac­cine was al­ready widely avail­able and I was able to travel/​visit more again

My time in New York was the most ac­tive when it comes to check-ins. When I’m in NYC, I tend to eat/​drink out more, and grab to-go food, which I do way less in Vienna

Every Swarm check-in vi­su­al­ized on a map. Only ar­eas where I’ve had mul­ti­ple check-ins are ren­dered.

Number of days per year that I’ve spent in full lock­down, mean­ing restau­rants, bars and non-es­sen­tial stores were closed.

I es­caped parts of the Austrian lock­down by spend­ing time in the US when I was al­ready vac­ci­nated

Surprisingly 2021 I spent more days in a full lock­down than in 2020, even with vac­cines avail­able

How was my life af­fected by the re­cent COVID lock­downs? As lock­down day I clas­sify every day where places like restau­rants, gyms and non-es­sen­tial stores were closed.

200% more time spent in au­dio & video calls with friends (non-work re­lated)

60% more likely to fol­low my meal plan (macros & calo­ries)

50% colder tem­per­a­tures: Lockdowns tended to hap­pen in Autumn and Winter

100% less likely to dance

Alcoholic drinks per day. Days with no data are ren­dered as white

Friday and Saturday nights are clearly vis­i­ble on those graphs

2021 and sum­mer/​win­ter of 2019 also show the Wednesday night party in Vienna

Q2 and Q4 2020 clearly show the COVID lock­downs, as well as Q2 2021

Summer of 2021 all bars and dance clubs were open in Vienna

After you’ve re­viewed these con­tri­bu­tion guide­lines, you’ll be all set to

con­tribute to this pro­ject.

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I’ve been main­tain­ing Emacs Solo

for a while now, and I think it’s time to talk about what hap­pened in this lat­est cy­cle as the pro­ject reaches its two-year mark.

For those who haven’t seen it be­fore, Emacs Solo is my daily-dri­ver Emacs con­fig­u­ra­tion with one strict rule: no ex­ter­nal pack­ages. Everything is ei­ther built into Emacs or writ­ten from scratch by me in the lisp/ di­rec­tory. No pack­age-in­stall, no straight.el, no

use-pack­age :ensure t point­ing at ELPA or MELPA. Just Emacs and Elisp. I’m keep­ing this post text only, but if you’d like to check how

Emacs Solo looks and feels, the repos­i­tory has screen­shots and more de­tails.

Why? Partly be­cause I wanted to un­der­stand what Emacs ac­tu­ally gives you out of the box. Partly be­cause I wanted my con­fig to sur­vive with­out break­age across Emacs re­leases. Partly be­cause I was tired of deal­ing with pack­age repos­i­to­ries, mir­rors go­ing down in the mid­dle of the work­day, na­tive com­pi­la­tion hic­cups, and the in­evitable down­time when some­thing changed some­where up­stream and my job sud­denly be­came de­bug­ging my very long (at the time) con­fig in­stead of do­ing ac­tual work. And partly, hon­estly, be­cause it’s a lot of fun!

This post cov­ers the re­cent refac­tor, walks through every sec­tion of the core con­fig, in­tro­duces all 35 self-con­tained ex­tra mod­ules I’ve writ­ten, and shares some thoughts on what I’ve learned.

Now, I’ll be the first to ad­mit: this con­fig is long. But there’s a prin­ci­ple be­hind it. I only add fea­tures when they are not al­ready in Emacs core, and when I do, I try to build them my­self. That means the code is sketchy some­times, sure, but it’s in my con­trol. I wrote it, I un­der­stand it, and when it breaks, I know ex­actly where to look. The refac­tor I’m about to de­scribe makes this dis­tinc­tion crys­tal clear: what is “Emacs core be­ing tweaked” ver­sus what is “a re­ally hacky out­sider I built in be­cause I did­n’t want to live with­out it”.

The sin­gle biggest change in this cy­cle was ar­chi­tec­tural. Emacs Solo used to be one big init.el with every­thing crammed to­gether. That worked, but it had prob­lems:

— It was hard to nav­i­gate (even with out­line-mode)

— If some­one wanted just one piece, say my Eshell con­fig or my VC ex­ten­sions, they had to dig through thou­sands of lines

— It was dif­fi­cult to tell where “configuring built-in Emacs” ended and “my own hacky reim­ple­men­ta­tions” be­gan

The so­lu­tion was clean and sim­ple: split the con­fig into two lay­ers.

This file con­fig­ures only built-in Emacs pack­ages and fea­tures. Every

use-pack­age block in here has :ensure nil, be­cause it’s point­ing at some­thing that ships with Emacs. This is pure, stan­dard Emacs cus­tomiza­tion.

The idea is that any­one can read init.el, find a sec­tion they like, and

copy-paste it di­rectly into their own con­fig. No de­pen­den­cies. No setup. It just works, be­cause it’s con­fig­ur­ing things Emacs al­ready has.

These are my own im­ple­men­ta­tions: re­place­ments for pop­u­lar ex­ter­nal pack­ages, reimag­ined as small, fo­cused Elisp files. Each one is a proper pro­vide/​re­quire mod­ule. They live un­der lisp/ and are loaded at the bot­tom of init.el via a sim­ple block:

If you don’t want one of them, just com­ment out the re­quire line. If you want to use one in your own con­fig, just copy the .el file into your own lisp/ di­rec­tory and re­quire it. That’s it.

This sep­a­ra­tion made the whole pro­ject dra­mat­i­cally eas­ier to main­tain, un­der­stand, and share.

The init.el file is or­ga­nized into clearly la­beled sec­tions (using out­line-mode-friendly head­ers, so you can fold and nav­i­gate them in­side Emacs). Here’s every built-in pack­age and fea­ture it touches, and why.

The emacs use-pack­age block is the largest sin­gle sec­tion. It sets up sen­si­ble de­faults that most peo­ple would want:

— Window lay­out com­mands bound un­der C-x w (these are up­com­ing

Emacs 31 fea­tures: win­dow-lay­out-trans­pose,

win­dow-lay­out-ro­tate-clock­wise, win­dow-lay­out-flip-left­right,

win­dow-lay­out-flip-top­down)

— Disabling C-z (suspend) be­cause ac­ci­den­tally sus­pend­ing Emacs in a ter­mi­nal is never fun

— Sensible file han­dling: back­ups and auto-saves in a cache/

di­rec­tory, re­centf for re­cent files, clean buffer nam­ing with

uniquify

— Tree-sitter auto-in­stall and auto-mode (treesit-auto-install-grammar t and treesit-en­abled-modes t, both Emacs 31)

— delete-pair-push-mark, kill-re­gion-dwim, ibuffer-hu­man-read­able-size, all the small qual­ity-of-life set­tings com­ing in Emacs 31

A full ab­brev-mode setup with a cus­tom place­holder sys­tem. You de­fine ab­bre­vi­a­tions with ###1###, ###2### mark­ers, and when the ab­bre­vi­a­tion ex­pands, it prompts you to fill in each place­holder in­ter­ac­tively. The ###@### marker tells it where to leave point af­ter ex­pan­sion. I wrote a whole ar­ti­cle about it.

Configures auth-source to use ~/.authinfo.gpg for cre­den­tial stor­age. Simple but es­sen­tial if you use Gnus, ERC, or any net­work-fac­ing Emacs fea­ture.

Makes buffers au­to­mat­i­cally re­fresh when files change on disk. Essential for any Git work­flow.

Configuration file mode set­tings and a com­pi­la­tion-mode setup with ANSI color sup­port, so com­piler out­put ac­tu­ally looks read­able.

Custom win­dow man­age­ment be­yond the de­faults, be­cause Emacs win­dow man­age­ment out of the box is pow­er­ful but needs a lit­tle nudg­ing.

Tab-bar con­fig­u­ra­tion for work­space man­age­ment. Emacs has had tabs since ver­sion 27, and they’re gen­uinely use­ful once you con­fig­ure them prop­erly.

Two IRC clients, both built into Emacs, both con­fig­ured. ERC gets the big­ger treat­ment: log­ging, scroll­to­bot­tom, fill, match high­light­ing, and even in­line im­age sup­port (via one of the ex­tra mod­ules). The Emacs 31 cy­cle brought nice im­prove­ments here too, in­clud­ing a fix for the scroll­to­bot­tom/​fill-wrap de­pen­dency is­sue.

This is where Emacs Solo’s com­ple­tion story lives. Instead of reach­ing for Vertico, Consult, or Helm, I use icom­plete-ver­ti­cal-mode, which is built into Emacs. With the right set­tings it’s sur­pris­ingly ca­pa­ble:

I’ve also been con­tribut­ing patches up­stream to im­prove icom­plete’s ver­ti­cal ren­der­ing with pre­fix in­di­ca­tors. Some of those fea­tures are al­ready land­ing in Emacs 31, which means the poly­fill code I carry to­day will even­tu­ally be­come un­nec­es­sary.

A heav­ily cus­tomized Dired setup. Custom list­ing switches, hu­man read­able sizes, in­te­gra­tion with sys­tem open­ers (open on ma­cOS,

xdg-open on Linux), and the dired-hide-de­tails-hide-ab­solute-lo­ca­tion

op­tion from Emacs 31.

Writable Dired, so you can re­name files by edit­ing the buffer di­rectly.

This one I’m par­tic­u­larly proud of. Emacs Solo’s Eshell con­fig­u­ra­tion in­cludes:

— Shared his­tory across all Eshell buffers: Every Eshell in­stance reads from and writes to a merged his­tory, so you never lose a com­mand just be­cause you ran it in a dif­fer­ent buffer

— Custom prompts: Multiple prompt styles you can tog­gle be­tween with C-c t (full vs. min­i­mal) and C-c T (lighter vs. heav­ier full prompt)

This is one of the largest sec­tions and one I’m most in­vested in. Emacs’s built-in vc is an in­cred­i­ble piece of soft­ware that most peo­ple over­look in fa­vor of Magit. I’m not say­ing it re­places Magit en­tirely, but with the right con­fig­u­ra­tion it cov­ers 95% of daily Git op­er­a­tions:

— Git add/​re­set from vc-dir: S to stage, U to un­stage, di­rectly in the vc-dir buffer. Admittedly, I al­most never use this be­cause I’m now used to the Emacs-style VC work­flow: C-x v D or C-x v =, then killing what I don’t want, split­ting what is­n’t ready yet, and fin­ish­ing with C-c C-c. Amending with C-c C-e is awe­some. Still use­ful once or twice a se­mes­ter.

— Browse re­mote: C-x v B opens your repos­i­tory on GitHub/GitLab in a browser; with a pre­fix ar­gu­ment it jumps to the cur­rent file and line

— Jump to cur­rent hunk: C-x v = opens the diff buffer scrolled to the hunk con­tain­ing your cur­rent line

— Switch be­tween mod­i­fied files: C-x C-g lets you

com­plet­ing-read through all mod­i­fied/​un­tracked files in the cur­rent repo

Merge con­flict res­o­lu­tion and diff view­ing. Ediff con­fig­ured to split win­dows sanely (side by side, not in a new frame).

Documentation at point, with el­doc-help-at-pt (Emacs 31) for show­ing docs au­to­mat­i­cally.

The LSP client that ships with Emacs. Configured with:

— Custom server pro­grams, in­clud­ing ras­sum­fras­sum for mul­ti­plex­ing TypeScript + ESLint + Tailwind (I wrote a whole post

about that)

— Keybindings un­der C-c l for code ac­tions, re­name, for­mat, and in­lay hints

— Automatic en­abling for all prog-mode buffers ex­cept

emacs-lisp-mode and lisp-mode

Diagnostics, spell check­ing, and white­space vi­su­al­iza­tion. All built-in, all con­fig­ured.

The Emacs news­reader and email client. Configured for IMAP/SMTP us­age.

RSS/Atom feed reader built into Emacs. Customized with some ex­tras I build my self for deal­ing with youtube feeds: thumb­nail, tran­scripts, send­ing to AI for a quick sum­mary, and so on.

Org-mode con­fig­u­ra­tion, be­cause of course.

File tree nav­i­ga­tion in a side win­dow. With Emacs 31, speed­bar gained speed­bar-win­dow sup­port, so it can live in­side your ex­ist­ing frame in­stead of spawn­ing a new one.

Buffer name dis­am­bigua­tion when you have mul­ti­ple files with the same name open.

Quick web searches from the minibuffer. Configured with use­ful search en­gines.

Specific con­fig­u­ra­tions for every lan­guage I work with, or­ga­nized into three ar­eas:

Common Lisp: in­fe­rior-lisp and lisp-mode with cus­tom REPL in­ter­ac­tion, eval­u­a­tion com­mands, and a poor man’s SLIME/SLY setup that ac­tu­ally works quite well for ba­sic Common Lisp de­vel­op­ment.

Non-Tree-sitter: sass-mode for when tree-sit­ter gram­mars aren’t avail­able.

Tree-sitter modes: ruby-ts-mode, js-ts-mode,

json-ts-mode, type­script-ts-mode, bash-ts-mode,

rust-ts-mode, toml-ts-mode, mark­down-ts-mode (Emacs 31),

yaml-ts-mode, dock­er­file-ts-mode, go-ts-mode. Each one con­fig­ured with tree-sit­ter gram­mar sources (which Emacs 31 is start­ing to de­fine in­ter­nally, so those de­f­i­n­i­tions will even­tu­ally be­come un­nec­es­sary).

This is where the fun re­ally is. Each of these is a com­plete, stand­alone Elisp file that reim­ple­ments func­tion­al­ity you’d nor­mally get from an ex­ter­nal pack­age. They’re all in lisp/ and can be used in­de­pen­dently.

I call them “hacky reim­ple­men­ta­tions” in the spirit of Emacs Solo: they’re not try­ing to be fea­ture-com­plete re­place­ments for their MELPA coun­ter­parts. They’re try­ing to be small, un­der­stand­able,

and good enough for daily use while keep­ing the con­fig self-con­tained.

Custom color themes based on Modus. Provides sev­eral theme vari­ants: Catppuccin Mocha, Crafters (the de­fault), Matrix, and GITS. All built on top of Emacs’s built-in Modus themes by over­rid­ing faces, so you get the ac­ces­si­bil­ity and com­plete­ness of Modus with dif­fer­ent aes­thet­ics.

Custom mode-line for­mat and con­fig­u­ra­tion. A hand-crafted mode-line that shows ex­actly what I want: buffer state in­di­ca­tors, file name, ma­jor mode, Git branch, line/​col­umn, and noth­ing else. No doom-mod­e­line, no tele­phone-line, just for­mat strings and faces.

Enhanced nav­i­ga­tion and win­dow move­ment com­mands. Extra com­mands for mov­ing be­tween win­dows, re­siz­ing splits, and nav­i­gat­ing buffers more ef­fi­ciently.

Configurable for­mat-on-save with a for­mat­ter reg­istry. You reg­is­ter for­mat­ters by file ex­ten­sion (e.g., pret­tier for .tsx,

black for .py), and the mod­ule au­to­mat­i­cally hooks into

af­ter-save-hook to for­mat the buffer. All con­trol­lable via a

de­f­cus­tom, so you can tog­gle it on and off glob­ally.

Frame trans­parency for GUI and ter­mi­nal. Toggle trans­parency on your Emacs frame. Works on both graph­i­cal and ter­mi­nal Emacs, us­ing the ap­pro­pri­ate mech­a­nism for each.

Sync shell PATH into Emacs. The clas­sic ma­cOS prob­lem: GUI Emacs does­n’t in­herit your shel­l’s PATH. This mod­ule solves it the same way exec-path-from-shell does, but in about 20 lines in­stead of a full pack­age.

Rainbow col­or­ing for match­ing de­lim­iters. Colorizes nested paren­the­ses, brack­ets, and braces in dif­fer­ent col­ors so you can vi­su­ally match nest­ing lev­els. Essential for any Lisp, and help­ful every­where else.

Interactive pro­ject finder and switcher. A com­plet­ing-read

in­ter­face for find­ing and switch­ing be­tween pro­jects, build­ing on Emacs’s built-in pro­ject.el.

Vim-like key­bind­ings and text ob­jects for Viper. If you use Emacs’s built-in viper-mode (the Vim em­u­la­tion layer), this ex­tends it with text ob­jects and ad­di­tional Vim-like com­mands. No Evil needed.

Highlight TODO and sim­i­lar key­words in com­ments. Makes TODO,

FIXME, HACK, NOTE, and sim­i­lar key­words stand out in source code com­ments with dis­tinc­tive faces. A small thing that makes a big dif­fer­ence.

Git diff gut­ter in­di­ca­tors in buffers. Shows added, mod­i­fied, and deleted line in­di­ca­tors in the mar­gin, like diff-hl or

git-gut­ter. Pure Elisp, us­ing vc-git un­der the hood.

Quick win­dow switch­ing with la­bels. When you have three or more win­dows, this over­lays sin­gle-char­ac­ter la­bels on each win­dow so you can jump to any one with a sin­gle key­stroke. A min­i­mal reim­ple­men­ta­tion of the pop­u­lar ace-win­dow pack­age.

Centered doc­u­ment lay­out mode. Centers your text in the win­dow with wide mar­gins, like olivetti-mode. Great for prose writ­ing, Org doc­u­ments, or any time you want a dis­trac­tion-free cen­tered lay­out.

Upload text and files to 0x0.st. Select a re­gion or a file and up­load it to the 0x0.st paste ser­vice. The URL is copied to your kill ring. Quick and use­ful for shar­ing snip­pets.

Edit files as root via TRAMP. Reopen the cur­rent file with root priv­i­leges us­ing TRAMP’s /sudo:: pre­fix. A reim­ple­men­ta­tion of the

I’m some­times late to no­tice new and ter­ri­ble things about ma­cOS 26 Tahoe, be­cause I use it only for test­ing, on a sec­ondary Mac. My main Mac re­mains on Sequoia, as en­forced by Little Snitch. I was of course aware that app win­dows on Tahoe have ex­ag­ger­ated cor­ner ra­diuses, but I was un­aware un­til now that the win­dow cor­ner ra­dius on Tahoe is not uni­form: dif­fer­ent win­dows can have dif­fer­ent cor­ner ra­diuses!

Below is a TextEdit win­dow on Tahoe.

And be­low is a Calculator win­dow in front of the TextEdit win­dow. Notice the cor­ners of the TextEdit win­dow stick­ing out!

What ac­counts for the dif­fer­ence? A tool­bar in the win­dow.

In a new Mac app Xcode pro­ject, the main win­dow has a less ex­ag­ger­ated cor­ner ra­dius by de­fault, like TextEdit.

When I add a tool­bar to the win­dow, the cor­ner ra­dius au­to­mat­i­cally be­comes more ex­ag­ger­ated, like Calculator.

Apparently the cor­ner ra­dius also changes on Tahoe for some other win­dow el­e­ments, such as a side­bar.

If this is­n’t the stu­pid­est user in­ter­face “feature” ever in­vented, I don’t know what is. The Mac used to be fa­mous for con­sis­tency; now it’s be­com­ing in­fa­mous for in­con­sis­tency.

By the way, Tahoe’s UI changes are per­plex­ing not only for Apple users but also for Apple en­gi­neers. Here’s a bug fix from the open source WebKit browser en­gine pow­er­ing Safari: [macOS] Scroll bars of root scroller may be cut­off due to cor­ner radii of win­dow.

See my fol­low-up post The evo­lu­tion of Mac app win­dow cor­ners.

Ce blog traite d’é­d­u­ca­tion, d’en­seigne­ment supérieur, du Limousin et du Périgord, de Nantes et alen­tours, de so­ciété, de ce que nous lisons, il pose des ques­tions, at­tend des réponses, in­forme. Espérons que per­sonne ne dira “quoras auras-tu’ch­a­bat de pla­tus­sar ?” quand auras-tu fini de faire du blablaware ? “When will you stop quack­ing?” (blog joint :http://​quo­ras-tu-cha­bat.hautet­fort.com/)