type me = "davidblass"type reverse<s extends string> = s extends `${infer head}${infer tail}` ? `${reverse<tail>}${head}` : "" type me = reverse<"ssalbdivad">computed by the compiler at buildTS 6.0.3// TypeScript engineer · Boston, MA

David Blass

I write the TypeScript types other libraries depend on- and lately, the agents that write the rest.

author: ArkType (TypeScript's 1:1 validator) · ArkRegex · Attest
co-creator: Standard Schema · one interface for every TS validator
co-founder: Pullfrog · AI agents in GitHub Actions
consultant: TypeScript performance · 2023–25 · for tRPC, Prisma, Drizzle & more

Email medavid@arktype.io GitHub LinkedIndavid@arktype.io

const arktypeDownloads: 9_055_997npm downloads of arktype, Sep 13, 2026 – Oct 12, 20267.4× since May 2025: 1.07M downloads that month, 8.01M in Sep 2026.@see api.npmjs.org/downloads/point/2026-09-13:2026-10-12/arktypesnapshot · 2026-10-14 12:52 UTCnpm

ArkType downloads a month

npm · 30 days to Oct 12

const specDownloads: 551_490_697npm downloads of @standard-schema/spec, Sep 13, 2026 – Oct 12, 202671× since May 2025: 6.64M downloads that month, 472M in Sep 2026.Downloads of the spec package itself. Mostly transitive, as a runtime dependency of packages like Vercel's AI SDK (@ai-sdk/provider-utils) and Redux Toolkit.@see api.npmjs.org/downloads/point/2026-09-13:2026-10-12/@standard-schema/specsnapshot · 2026-10-14 12:52 UTCnpm

Standard Schema spec downloads a month

@standard-schema/spec · via AI SDK, Redux Toolkit

const answerOverflow: { before: "6.66s"; after: "3.29s"; runs: 5 }I found, minimized and benchmarked this slowdown and drove the fix; Mateusz Burzyński (@Andarist) wrote the compiler patch. AnswerOverflow's dashboard, type-checked on TS 5.8 vs. the #61505 build. Mean of 5 runs each; the ranges don't overlap.Jake Bailey (TS team) measured the same repo independently: 7.67s → 3.79s.@see microsoft/TypeScript#61535 (comment)@see typescript-go#1358 (Jake Bailey's run)public recordsourced

faster type-checks on real tRPC apps in TS 5.9

6.7s → 3.3s · 5 runs · found & drove it

const arkregexLaunch: { views: 733_569; likes: 3_119; reposts: 392 }The ArkRegex launch post on X, Oct 28, 2025.Read from the public fxtwitter mirror. The launch post alone; quotes and reposts not counted.@see x.com/arktypeio/status/1983210635266498649as of · 2026-10-13sourced

views on the ArkRegex launch post

@arktypeio on X · Oct 28, 2025

arkregex · regex with typeshover any nametap any name

import { type regex<pattern extends string = string, ctx extends RegexContext = RegexContext> = Regex<pattern, ctx>

const regex: RegexParserregex } from "arkregex"

const const version: Regex<`${number}.${number}`, {
    captures: [`${number}`, `${number}`];
    names: {
        major: `${number}`;
        minor: `${number}`;
    };
}>version = regex<"^(?<major>\\d+)\\.(?<minor>\\d+)$", "">(src: "^(?<major>\\d+)\\.(?<minor>\\d+)$", flags?: "" | undefined): Regex<`${number}.${number}`, {
    captures: [`${number}`, `${number}`];
    names: {
        major: `${number}`;
        minor: `${number}`;
    };
}>regex(
	"^(?<major>\\d+)\\.(?<minor>\\d+)$"
)

const { 
const groups: {
    major: `${number}`;
    minor: `${number}`;
}groups } = const version: Regex<`${number}.${number}`, {
    captures: [`${number}`, `${number}`];
    names: {
        major: `${number}`;
        minor: `${number}`;
    };
}>version.Regex<`${number}.${number}`, { captures: [`${number}`, `${number}`]; names: { major: `${number}`; minor: `${number}`; }; }>.exec(s: string): RegexExecArray<[`${number}.${number}`, `${number}`, `${number}`], {
    major: `${number}`;
    minor: `${number}`;
}, ""> | null (+1 overload)exec("2.2")!

inferred from the pattern: real compiler outputTS 6.0.3 · arkregex 0.0.13

01 // work

Things people install

ArkType⛵

author · 2022–

arktype.io

TypeScript's 1:1 validator, optimized from editor to runtime. You write types as TypeScript syntax, in strings. A parser written in the type system reads them as you type; at runtime they compile to JIT-friendly validation code. Agents can learn it too: npx skills add arktypeio/arktype

const arktypeStars: 7_874GitHub stars on arktypeio/arktype@see github.com/arktypeio/arktypesnapshot · 2026-10-14 12:52 UTCGitHubGitHub stars

arktype · the real parser, running livetype anything

✓ an email address

'david@arktype.io' extends string.email → true · union reduced

// "It's true- our static parser is the most flagrant abuse of the type system in a mainstream library." — @arktypeio

ArkRegex

2025

launch post InfoQ

A drop-in replacement for new RegExp() with types. The first library to validate and infer regex from TypeScript's type system: capture groups come back typed, and a malformed pattern is a type error. (That's it up top.)

3,119likes

Attest

2023

docs Theo's video

Type-level benchmarks and assertions for TypeScript. Instantiation counts are deterministic: the same number on every machine, every run, so CI can fail the PR that makes your types 20% slower. It's the tool behind every case study below- and other people's: i18next used it to take one type const i18nextType: { before: 218_121; after: 278 }Instantiations for one i18next type, in a contributor's initial attest benchmark of the refactor that shipped as i18next's selector API.@see i18next/i18next#2317 (comment)@see i18next/i18next#2322public recordsourced.

const attestDownloads: 427_538npm downloads of @ark/attest, Sep 13, 2026 – Oct 12, 2026@see api.npmjs.org/downloads/point/2026-09-13:2026-10-12/@ark/attestsnapshot · 2026-10-14 12:52 UTCnpmdownloads / mo

ArkSchema

The set-theoretic type system underneath. Intersections, subtyping and union discrimination at runtime- it can compare arbitrary pairs of types for assignability. The 13-minute version is my Effect Days talk

Standard Schema

co-creator · 2024–

standardschema.dev

One interface, so any TypeScript validator plugs into any framework. Colin McDonnell (Zod) came up with the idea; Fabian Hiller (Valibot) and I designed it with him. Then we co-authored Standard JSON Schema, so any validator can define tool inputs for AI agents and MCP.

const standardSchemaStars: 3_650GitHub stars on standard-schema/standard-schema@see github.com/standard-schema/standard-schemasnapshot · 2026-10-14 12:52 UTCGitHubGitHub stars

validatorsframeworks & toolsZod Valibot ArkType⛵Effect Schema tRPC TanStack Form TanStack Router Hono React Hook Form Elysia Nuxt UI AI SDK + more + more

StandardSchemaV1 · one interface

const email = type("string.email")

email["~standard"].StandardSchemaV1<Input = unknown, Output = Input>.Props<string, string>.validate: (value: unknown, options?: StandardSchemaV1<Input = unknown, Output = Input>.Options | undefined) => StandardSchemaV1.Result<string> | Promise<StandardSchemaV1.Result<string>>validate(
	"david@arktype.io"
)

12 integrations instead of 32 adapters · const standardSchemaEcosystem: { validators: "30+"; tools: "60+" }Libraries listed on standardschema.dev as implementing or accepting the spec.Rounded down from a count of 33 and 64 on the live list.@see standardschema.dev/schemaas of · 2026-10-13sourced

the diagram as a table

Integrations with and without Standard Schema
	without a standard	with Standard Schema
validators	Zod, Valibot, ArkType, Effect Schema
tools	tRPC, TanStack Form, TanStack Router, Hono, React Hook Form, Elysia, Nuxt UI, AI SDK
integrations	4 × 8 = 32	4 + 8 = 12

rivalsonce you go type("string") you never go z.back()— @arktypeio
co-authorswritten collaboratively by the creators of Zod (👋), Valibot, and ArkType— Colin, announcing Standard Schema 1.0
co-founderssounds fake but I'm starting a company with my nemesis Colin P. Zod— me
BETRAYAL— @arktype.io

Pullfrog🐸

co-founder · 2025–

pullfrog.com

AI coding agents that run in your GitHub Actions. Pullfrog wraps vanilla Claude Code, Codex and OpenCode to review PRs, triage issues, fix CI, resolve merge conflicts and test UIs in a headless browser. Your infrastructure, your keys, your costs. I co-founded it with Colin McDonnell (Zod) and built the model-agnostic agent runtime: BYOK, MCP tools, GitHub App/OIDC auth, sandboxed CI.Used by Sanity, Trigger.dev, Zed, Unkey, Remotion and Inkeep.

const pullfrogStars: 1_310GitHub stars on pullfrog/pullfrog@see github.com/pullfrog/pullfrogsnapshot · 2026-10-14 12:52 UTCGitHubGitHub stars

const pullfrogDownloads: 211_712npm downloads of pullfrog, Sep 13, 2026 – Oct 12, 2026@see api.npmjs.org/downloads/point/2026-09-13:2026-10-12/pullfrogsnapshot · 2026-10-14 12:52 UTCnpmnpm downloads / mo

02 // perf

Why your types are slow

"our two-step process for fast typescript types: 1️⃣ build a type‑level benchmarking library 2️⃣ spend the prime of your life on cache optimizations" @arktype.io

Clients have included tRPC, Drizzle, Prisma, Convex, AWS Amplify, Speakeasy, Stately, wevm, Vanta and Cloudinary. Most of that work is private; these three cases are public.

case 01TypeScript compiler2025

Two innocent-looking useMutation calls took about 2 seconds each to type-check.

Chained Zod- and tRPC-style types made the compiler redo every earlier link- O(3^N) instantiations, ending in error TS2589: Type instantiation is excessively deep and possibly infinite.What TypeScript 5.8.2 says about 13 chained .merge() calls: the bench below, reproduced Oct 13, 2026. 5.9 checks the same chain without a word.tsc 5.8.2 · reproducedTS 5.9.3: 0 errors errors.

I traced it into TypeScript itself, minimized the repro, benchmarked it with Attest and argued it through review- including my reply to Anders Hejlsberg: "…if there are O(3^N) of them, they will eventually dominate the check time of the entire type." Mateusz Burzyński (@Andarist) wrote the compiler patch; it shipped in TypeScript 5.9 and was ported to the Go compiler.

"in case anyone was curious what O(3^N) looks like"

show the bench

bench · chained11 calls

type merge<base, props> =
	Omit<base, keyof props & keyof base>
	& props

type Type<t> = {
	merge: <r>(r: r) => Type<merge<t, r>>
}

declare const const a: Type<{
    a: 1;
}>a: Type<{ a: 1a: 1 }>

const const c1: Type<merge<{
    a: 1;
}, {
    b: number;
}>>c1 = const a: Type<{
    a: 1;
}>a.merge({ b: 2 })
const const c2: Type<merge<merge<{
    a: 1;
}, {
    b: number;
}>, {
    c: number;
}>>c2 = const c1: Type<merge<{
    a: 1;
}, {
    b: number;
}>>c1.merge({ c: 3 })
const const c3: Type<merge<merge<merge<{
    a: 1;
}, {
    b: number;
}>, {
    c: number;
}>, {
    d: number;
}>>c3 = const c2: Type<merge<merge<{
    a: 1;
}, {
    b: number;
}>, {
    c: number;
}>>c2.merge({ d: 4 })
const const c4: Type<merge<merge<merge<merge<{
    a: 1;
}, {
    b: number;
}>, {
    c: number;
}>, {
    d: number;
}>, {
    e: number;
}>>c4 = const c3: Type<merge<merge<merge<{
    a: 1;
}, {
    b: number;
}>, {
    c: number;
}>, {
    d: number;
}>>c3.merge({ e: 5 })
const c5 = const c4: Type<merge<merge<merge<merge<{
    a: 1;
}, {
    b: number;
}>, {
    c: number;
}>, {
    d: number;
}>, {
    e: number;
}>>c4.merge({ f: 6 })
const c6 = c5.merge({ g: 7 })
const c7 = c6.merge({ h: 8 })
const c8 = c7.merge({ i: 9 })
const c9 = c8.merge({ j: 10 })
const c10 = c9.merge({ k: 11 })
const c11 = c10.merge({ l: 12 })
const c12 = c11.merge({ m: 13 })
const c13 = c12.merge({ n: 14 })
const c14 = c13.merge({ o: 15 })
const c15 = c14.merge({ p: 16 })

TS 5.8.2⛳ Result: 1,596,004 instantiations

TS 5.9.3⛳ Result: 976 instantiations

type instantiations

Instantiation counts from @ark/attest 0.57.0: deterministic, the same on every machine. Bench from microsoft/TypeScript#61505; re-run on 5.8.2 and 5.9.3, Oct 13, 2026.

Data

Type instantiations by number of .merge() calls (attest 0.57.0). "TS2589" means the checker bailed; the count it reported is in parentheses and isn't real work.
calls	chained 5.8.2	chained 5.9.3	functional 5.8.2	functional 5.9.3
1	98	36	30	14
2	250	85	77	33
3	524	144	163	55
4	1,136	213	360	80
5	2,734	292	884	108
6	7,262	381	2,383	139
7	20,552	480	6,801	173
8	60,100	589	19,970	210
9	178,394	708	59,386	250
10	532,898	837	177,537	293
11	1,596,004	976	531,887	339
12	4,784,888	1,125	1,594,828	388
13	TS2589 (9,785,026)	1,284	4,783,536	440
14	TS2589 (14,785,170)	1,453	14,349,539	495
15	TS2589 (14,785,298)	1,632	TS2589 (24,349,567)	553

What it did to real appscheck time on TS 5.9, as a share of TS 5.8 · shorter is faster

A tRPC monorepo I testedconst trpcMonorepo: { before: "13.04s"; after: "6.00s"; runs: 1 }A tRPC monorepo I tested, TS 5.8 vs. the #61505 build.A single run.@see microsoft/TypeScript#61505 (comment)public recordsourced2.1×single run

AnswerOverflow dashboard (public repo)const answerOverflow: { before: "6.66s"; after: "3.29s"; runs: 5 }I found, minimized and benchmarked this slowdown and drove the fix; Mateusz Burzyński (@Andarist) wrote the compiler patch. AnswerOverflow's dashboard, type-checked on TS 5.8 vs. the #61505 build. Mean of 5 runs each; the ranges don't overlap.Jake Bailey (TS team) measured the same repo independently: 7.67s → 3.79s.@see microsoft/TypeScript#61535 (comment)@see typescript-go#1358 (Jake Bailey's run)public recordsourced2.0×5 runs each, no overlap

Klarna appconst klarna: { before: "395.48s"; after: "132.09s" }Klarna's app, reported by one of their engineers: "This was a game-changer PR for us."Third-party and self-reported, in one comment.@see microsoft/TypeScript#61505 (comment)@see microsoft/TypeScript#61505 (Klarna, follow-up)public recordsourced2.9×self-reported, in one comment

Data

app	TS 5.8	TS 5.9	share	runs
A tRPC monorepo I tested	13.04s	6.00s	46.0%	single run
AnswerOverflow dashboard (public repo)	6.44s / 6.58s / 6.99s / 6.33s / 7.00s	3.25s / 3.34s / 3.21s / 3.24s / 3.43s	49.4%	5 runs each, no overlap
Klarna app	395.48s	132.09s	33.4%	self-reported, in one comment

Compiler patch by Mateusz Burzyński (@Andarist) · microsoft/TypeScript#61505 · TS 5.9 notes · typescript-go#1358

The ~2× is 5 runs per side with no overlap. My 13.04s → 6.00s is one run. Klarna's ~3× is self-reported, in one comment.

"Please contact @ssalbdivad. He is probably the best TypeScript performance consultant in the world…"

a stranger in Prisma's issue tracker · prisma/orm#29011

case 02viem + MUD2024

One type. Nine type parameters.
const getVariancesWorker: { ms: 1_866; typeParams: 9 }Time TypeScript spent computing the variance of viem's SimulateContractReturnType, in a trace of MUD's build: 1.86s, truncated.@see latticexyz/mud#2956@see wevm/viem#2557public recordsourced

In MUD's build, TypeScript spent 1.86s just computing the variance of one viem type, and instantiation counts never showed it. Only a trace did. With variance annotated by hand, the entire file checked in 1.28s. Explicit in/out annotations now ship in viem itself, so every consumer skips that work.

"avoiding the variance checks reduced the check time for a simple repo by over a second locally."

— me, in wevm/viem#2557

before

checkSourceFile · setupNetwork.tstotal not published

getVariancesWorker · SimulateContractReturnType1,866 ms

after

checkSourceFile · setupNetwork.ts (annotated)1,288 ms

played back in real time

Data

track	slice	duration
before	checkSourceFile · setupNetwork.ts	not published
before	getVariancesWorker · SimulateContractReturnType (9 type parameters)	1,866 ms
after	checkSourceFile · setupNetwork.ts (annotated)	1,288 ms

Slices aligned at 0; offsets within the original Perfetto trace omitted. Source: latticexyz/mud#2956.

case 03Prisma ORM + Mongoose2025

Prisma: 45% less check time on the generated file we restructured.

const commonInputTypes: { checkSourceFile: "4064µs → 2218µs"; lines: "339 → 82" }One file of Prisma's generated client, before and after the restructuring.One file, not the whole client.@see prisma.io/blog (type-check performance)@see prisma/orm#27046@see Prisma 6.16.0 release notespublic recordsourced

"We've worked with TypeScript expert David Blass to find ways for improving the type checking performance in Prisma ORM…"

— Prisma 6.16.0 release notes

Prisma · commonInputTypes, % of before

The 45% is one file (commonInputTypes), not the whole client. Measured in prisma/orm#27046; Prisma reports the same result on its blog.

Data

µs or lines
	before	after
checkSourceFile	4,064 µs	2,218 µs
createSourceFile	796 µs	246 µs
bindSourceFile	607 µs	164 µs
lines of code	339 LOC	82 LOC

Also shipped: Mongoose 8.19, InferRawDocType, const inferRawDocType: { simple: "501 → 320"; mixed: "1626 → 535"; nested: "4214 → 2097" }Instantiations on Mongoose's attest benches for InferRawDocType.The maintainer's whole-repo count was flat (+0.9%).@see Automattic/mongoose#15588public recordsourced.

On its benchmarks. The maintainer's whole-repo count was flat (+0.9%). Automattic/mongoose#15588.

Data

instantiations
	before	after
simple schema	501	320
mixed schema	1,626	535
nested schema	4,214	2,097

03 // agents

How I work with agents

I build Pullfrog by running many coding agents in parallel, every day, through Ntwine- a local tool I maintain that puts every agent thread on one board and queues the ones that need me. It continues Colin McDonnell's Frizz; the queue, the board and the principles behind them are his design. These are the rules I've added on top, for the agents and for me.

01Size work by scope, never in days.
Agents do the building, so hours are the wrong unit. Scope is the code paths a change touches, its risk, and what needs a human decision.
02Report honest effect sizes.
Say how strong a claim is right next to it, and treat pushback as a bug report on the measurement before defending the result. (The case studies above say which numbers are single runs.)
03Lead with what changed.
An agent's report leads with what changed or what is true. The why goes in the commit message and code comments, where the next reader will find it- not in the chat.
04Preserve evidence.
Never delete or rewrite a stored measurement. Experiments are temporary: record the conclusion and its numbers, then delete the harness.

This page was built that way.

research 6
design 5
build 36
review 50
tool call

08:49:46verifier → findings · 31 tool calls97 sub-agents · 7,900 tool calls · 11h 00m wall clock

UTC · Oct 13–14, 2026

Researched, designed, built and reviewed by one agent thread that fanned out to 97 sub-agents: 7,900 tool calls, 34h 05m of agent time in 11h 00m of wall clock. I set the bar in one brief and a follow-up; they did the legwork. Every strand, tick and timestamp above is from the session.

// scripts/replay.ts reads the session's transcript metadata (labels, timestamps, tool-call counts) into a snapshot taken 2026-10-14 08:49 UTC. It reads message text only to tell mine from automated check-ins, and stores none of it.

Every strand, as a table

strand	phase	UTC	length	tool calls	handed back
@personal-page	root	21:49:19–08:49:46	11h 00m	438	this page
perf-case-studies	research	21:52:06–22:03:03	11m	77	research-perf.md
talks-media	research	21:52:06–22:02:48	11m	79	research-media.md
voice-buzz	research	21:52:06–22:11:37	20m	85	research-voice.md
brand-local	research	21:52:06–22:02:09	10m	71	research-brand.md
stats-apis	research	21:52:06–21:57:00	4m 54s	33	research-stats.md
tech-stack	research	21:52:06–22:06:03	14m	75	research-stack.md
story	design	22:14:37–22:22:27	7m 50s	16	design-story.md
delight	design	22:14:37–22:24:23	9m 46s	28	design-delight.md
visual	design	22:14:37–22:30:34	16m	71	design-visual.md
dataviz	design	22:14:37–22:28:55	14m	31	design-dataviz.md
synthesis	design	22:30:35–22:40:56	10m	22	concept.md
work	build	22:54:50–23:32:04	37m	137	Work.tsx
perf	build	22:55:08–23:22:47	28m	104	Perf.tsx
agents-talks	build	22:55:26–23:22:02	27m	122	Agents.tsx
eggs	build	22:55:47–23:19:26	24m	129	Eggs.tsx
design review	review	23:38:14–00:18:34	40m	219	findings
recruiter review	review	23:38:15–23:56:16	18m	95	findings
honesty review	review	23:38:15–23:56:31	18m	97	findings
a11y review	review	23:38:15–00:13:43	35m	180	findings
interactions review	review	23:38:15–00:30:29	52m	133	stopped, no result
perfcode review	review	23:38:15–00:30:53	53m	72	stopped, no result
verifier	review	23:56:16–00:16:41	20m	75	findings
verifier	review	23:56:31–00:08:02	12m	78	findings
verifier	review	00:13:44–00:30:21	17m	74	stopped, no result
verifier	review	00:18:34–00:30:18	12m	69	stopped, no result
interactions review	review	00:57:28–02:10:46	1h 13m	138	findings
verifier	review	00:57:28–01:26:06	29m	134	findings
perfcode review	review	00:57:29–01:42:11	45m	136	findings
verifier	review	00:57:29–01:08:28	11m	80	findings
verifier	review	00:57:29–01:13:51	16m	84	findings
verifier	review	00:57:29–01:15:00	18m	99	findings
work · fixes	build	00:59:21–01:03:39	4m 19s	21	Work.tsx
perf · fixes	build	00:59:25–01:05:49	6m 24s	43	Perf.tsx
agents-talks · fixes	build	00:59:30–01:07:46	8m 16s	47	Agents.tsx
eggs · fixes	build	00:59:35–01:01:31	1m 57s	16	Eggs.tsx
shell · fixes	build	01:00:01–01:32:59	33m	127	styles.css
eggs · fixes	build	01:38:16–01:44:17	6m 01s	33	Eggs.tsx
verifier	review	01:42:11–02:02:04	20m	72	findings
work · fixes	build	02:09:40–02:33:45	24m	52	Work.tsx
perf · fixes	build	02:09:45–02:51:33	42m	166	Perf.tsx
agents-talks · fixes	build	02:09:48–02:16:19	6m 31s	12	Agents.tsx
eggs · fixes	build	02:09:51–02:10:23	0m 32s	6	Eggs.tsx
shell · fixes	build	02:09:56–02:33:32	24m	73	styles.css
verifier	review	02:10:46–02:25:41	15m	78	findings
eggs · fixes	build	02:26:15–02:27:18	1m 02s	7	Eggs.tsx
design review · round 2	review	02:53:28–03:53:06	1h 00m	270	findings
recruiter review · round 2	review	02:53:29–03:17:08	24m	108	findings
honesty review · round 2	review	02:53:29–03:11:52	18m	105	findings
a11y review · round 2	review	02:53:29–03:42:41	49m	172	findings
interactions review · round 2	review	02:53:29–04:35:19	1h 42m	137	findings
perfcode review · round 2	review	02:53:29–03:41:57	48m	143	findings
verifier · round 2	review	03:11:52–03:20:18	8m 26s	47	findings
verifier · round 2	review	03:17:08–03:28:51	12m	45	findings
verifier · round 2	review	03:41:57–04:01:07	19m	56	findings
verifier · round 2	review	03:42:41–04:10:13	28m	91	findings
verifier · round 2	review	03:53:06–04:13:51	21m	91	findings
agents-talks · fixes	build	03:54:38–03:56:14	1m 36s	8	Agents.tsx
eggs · fixes	build	03:54:43–03:56:32	1m 49s	9	Eggs.tsx
shell · fixes	build	03:54:51–04:07:51	13m	29	styles.css
verifier · round 2	review	04:35:19–04:51:11	16m	56	findings
shell · fixes	build	04:52:07–05:28:34	36m	139	styles.css
perf · fixes	build	04:52:10–05:08:46	17m	69	Perf.tsx
work · fixes	build	04:52:13–05:10:25	18m	56	Work.tsx
agents-talks · fixes	build	04:52:17–04:59:30	7m 13s	27	Agents.tsx
eggs · fixes	build	04:52:19–04:57:59	5m 40s	23	Eggs.tsx
design review · round 3	review	05:30:44–06:03:39	33m	208	findings
recruiter review · round 3	review	05:30:46–05:56:03	25m	129	findings
honesty review · round 3	review	05:30:46–05:48:41	18m	126	findings
a11y review · round 3	review	05:30:46–06:44:40	1h 14m	222	findings
interactions review · round 3	review	05:30:46–07:04:30	1h 34m	150	findings
perfcode review · round 3	review	05:30:46–06:40:08	1h 09m	164	findings
verifier · round 3	review	05:48:41–05:55:13	6m 32s	48	findings
verifier · round 3	review	05:56:03–06:04:08	8m 05s	43	findings
agents-talks · fixes	build	06:01:58–06:26:58	25m	81	Agents.tsx
eggs · fixes	build	06:02:06–06:08:25	6m 20s	31	Eggs.tsx
verifier · round 3	review	06:03:39–06:15:24	12m	79	findings
shell · fixes	build	06:27:27–06:35:19	7m 53s	28	styles.css
perf · fixes	build	06:27:29–06:29:42	2m 13s	15	Perf.tsx
verifier · round 3	review	06:40:08–06:58:00	18m	53	findings
verifier · round 3	review	06:44:40–07:00:25	16m	86	findings
shell · fixes	build	07:02:16–07:10:24	8m 08s	33	styles.css
perf · fixes	build	07:02:22–07:12:04	9m 42s	15	Perf.tsx
work · fixes	build	07:02:27–07:06:23	3m 56s	18	Work.tsx
agents-talks · fixes	build	07:02:31–07:04:16	1m 44s	11	Agents.tsx
verifier · round 3	review	07:04:30–07:22:58	18m	69	findings
shell · fixes	build	07:23:15–07:30:12	6m 57s	27	styles.css
work · fixes	build	07:23:20–07:30:44	7m 25s	21	Work.tsx
perf · fixes	build	07:23:22–07:25:52	2m 30s	12	Perf.tsx
content check	review	07:32:47–07:49:29	17m	71	findings
visual check	review	07:32:48–07:50:13	17m	94	findings
interact check	review	07:32:48–08:26:17	53m	110	findings
sweep check	review	07:32:48–08:06:36	34m	116	findings
verifier	review	07:49:29–07:55:34	6m 04s	24	findings
verifier	review	07:50:13–07:52:28	2m 15s	23	findings
verifier	review	08:06:36–08:14:47	8m 11s	40	findings
verifier	review	08:26:17–08:47:50	22m	31	findings
agents-talks · fixes	build	08:34:46–08:37:06	2m 20s	7	Agents.tsx

04 // talks

Talks

13:13

Discriminated Unions in TypeScript, Effect, and ArkType

Effect Days 2024 · Vienna

"You probably have some idea of how assignability works in TypeScript… But can you explain it cohesively? This is your chance to learn how in 10 minutes⚡"

21:10

ArkType: Bringing TypeScript to Runtime

TypeScript Congress 2023

How the type-level parser works, from top-down to shift-reduce, and what it buys you at runtime.

on mic

about it

05 // said

Said in public

…knowing WHO implemented it, I have 100% trust that this just works as expected…
— AndrewGreenh, r/typescript, on ArkRegex (quoted by InfoQ) · Reddit
@ssalbdivad.dev you're amazing 🤩. Obviously WTF!? but in a good way 🤪
— Dominik (TkDodo), TanStack Query · Bluesky
wtf this is insane
— Aiden Bai, React Scan, on ArkRegex · X
ArkType's been up to some cool stuff for awhile, but attest takes it to a whole new level.
— Theo, “(Actually) Benchmarking TypeScript” · YouTube
these guys never shut up... ...they have too many good ideas 🫶
— Colin McDonnell (Zod), on Fabian Hiller and me · X
unbiased typescript perf expert here👋
this claim from @arktypeio is 100% accurate.
— David Blass (unbiased)

06 // before

Before all this

2019–21Redo
Founded it. We built a desktop app that turned recorded user interactions into UI tests. ArkType's git history still starts in Redo's repo, June 2019.
2017–19Amazon
SDET II, Alexa Devices. Built PyEcho, Amazon's standard test-automation framework for Alexa devices.
2011–15Tufts
Computer Science, Entrepreneurial Leadership, Philosophy.

07 // contact

Say hi

Building something hard in TypeScript or AI? I'd love to hear about it.

david@arktype.io

Things people install

ArkType⛵

ArkRegex

Attest

ArkSchema

Standard Schema

Pullfrog🐸

Why your types are slow

Two innocent-looking useMutation calls took about 2 seconds each to type-check.

One type. Nine type parameters.1.86 seconds.const getVariancesWorker: { ms: 1_866; typeParams: 9 }Time TypeScript spent computing the variance of viem's SimulateContractReturnType, in a trace of MUD's build: 1.86s, truncated.@see latticexyz/mud#2956@see wevm/viem#2557public recordsourced

Prisma: 45% less check time on the generated file we restructured.

How I work with agents

This page was built that way.

Talks

Discriminated Unions in TypeScript, Effect, and ArkType

ArkType: Bringing TypeScript to Runtime

// on mic

// about it

Said in public

Before all this

Say hi

One type. Nine type parameters.
const getVariancesWorker: { ms: 1_866; typeParams: 9 }Time TypeScript spent computing the variance of viem's SimulateContractReturnType, in a trace of MUD's build: 1.86s, truncated.@see latticexyz/mud#2956@see wevm/viem#2557public recordsourced

on mic

about it