#161

React Native is out at Shopify, SWE-2 is built on Kimi K3, and OpenAI deleted its own hedge

Shopify rebuilt the Shop app natively in 12 weeks and says coding agents are why, not speed. Cognition's SWE-2 is post-trained on Moonshot's Kimi K3.

In January 2025 a Shopify engineering director wrote that React Native’s future was bright. His post reversing that opens by quoting himself. Speed isn’t what changed his mind: “React Native apps can be fast. Ours are.”

Three open-source libraries go with the decision. FlashList is looking for a new owner, Restyle gets archived, and Skia’s maintainer will fork it under a new name.

In today’s indie hacker news:

  • 📱 The React Native bet Shopify just un-made
  • 🪆 A new coding model that wins one benchmark and loses another
  • 🔘 The ChatGPT training toggle, and what it really covers
  • 🛠️ Stack: syq, and the tagline its author regrets

TOP STORIES

AGENTS ATE THE WRITE-ONCE ARGUMENT

📱 Shopify is going back to Swift and Kotlin

A many-armed robot bolting together two identical phones side by side on a workbench while a builder watches and a cracked single phone lies discarded on the ground

The story: The entire case for one shared codebase was the cost of building each feature twice. Mustafa Ali’s post says agents cut that cost. A core team of six shipped the Shop app native in 12 weeks. The flagship app, 300+ screens, is still mid-migration.

The details:

  • Android cold start halved, 4,433ms to 2,233ms. iOS gained 23%, unexplained.
  • The migration writeup skips engineer-hours, agent spend and defect rates.
  • hermitwriter, the sharpest critic in the 940-point thread: “You’re making a claim about a cost that compounds over time based on what it costs at t=0.”
  • Another commenter pointed an agent at his Electron app overnight, woke to a near-complete Swift port, and called it “a complete devaluation of my craft.”

Why builders care: If your cross-platform stack exists to avoid a second codebase, agents just turned that into a price you can check yourself. Hand one duplicated screen to your agent this week and see what the native version really costs.

THE MODEL UNDER THE MODEL

🪆 Cognition’s SWE-2 is post-trained on Moonshot’s Kimi K3

A builder on a ladder hauling the lid off a giant matryoshka doll to reveal a different, sterner doll nested inside

The story: Cognition says SWE-2 scores 50.0% on FrontierCode, within a point of Fable 5.1, at 64% less cost. That benchmark is its own, and self-graded. The 3,000-word launch post never names Moonshot.

The details:

  • Terminal-Bench 4, built to resist gaming, has SWE-2 at 27.3 against Fable’s 55.8. On the older 2.1 version SWE-2 leads at 92.8.
  • postalcoder called that collapse benchmaxxing; mediaman answered “TB2.1 is saturated. TB4 is not.”
  • The Kimi K3 licence wants “Kimi K3” shown in the UI of any commercial product above $20M monthly revenue. Cognition’s reported ARR: $900M+.
  • SWE-2 has no per-token price and isn’t on OpenRouter, so the discount can’t be checked.

Why builders care: Open weights plus your own RL is the copyable part, and it scales a long way below Cognition’s budget. Read the licence on whatever base you pick: the clauses that cost you anything switch on once you’re earning.

ALLOW TRAINING, ALLEGEDLY BACK ON

🔘 443 points for the post, about three to one against it in the replies

A giant hand in a suit cuff shoving a large wall-mounted lever back into the on position while a small builder on a crate throws up both arms

The story: jacquesm says he switched off “allow training”, noted the date, and later found it back on. cbg0 speaks for most of the replies: “I’ve disabled the checkbox many months ago and it’s still disabled today.”

The details:

  • simonw asked whether that checkbox even covers Codex CLI and desktop. He got zero replies.
  • The Codex help page answers it: “Your ChatGPT training data controls apply to content processed through Codex.”
  • Advanced Account Security makes the opt-out automatic, and czk confirms it: “now that i have advanced account security enabled, the setting is disabled entirely.”
  • tedsanders, who says he works at OpenAI, answered where to opt out, not whether anything flips back.

Why builders care: On a personal ChatGPT login, that checkbox is the whole fence and you can’t verify it yourself. Sign Codex in with an API key instead: the API doesn’t train by default and has no toggle to re-check.

🤖 The boring half of an agent is now for rent - OpenAI’s Agents API hit public beta with durable sessions, context compaction, crash recovery and your own MCP servers. No separate fee: you pay model rates plus container time, from $0.03 per 20-minute session at 1 GB. 204 points on HN, and one complaint keeps repeating: every code sample in the docs passes gpt-6-astra, with no documented way to point it elsewhere.

🦀 Rust is a tier-1 language at Microsoft - It’s a guest post on the Rust Foundation’s blog by Victor Ciura, a principal engineer on Microsoft’s Rust tooling team. The substance is narrower than the headline: a new rustc backend that hands code generation to MSVC, now building 100+ internal repos. 640 points, and the top comment is “So when will we get tier 1 debugging support in Visual Studio?”

📐 Apple’s foldable ships before its SDK does - iPhone Duo pre-orders open October 16 and it ships a week later. Xcode 27.1 beta and the “Preparing your app” guide are both still “coming later this month”. The only live guidance is a HIG page that tells you to use size classes and publishes no pixel table. Two third-party spec writeups already disagree about the unfolded size.

DRAMA

🧮 THE HEDGE VANISHED

OpenAI’s Navier-Stokes post used to say it “cannot rule out” that de-identified user data improved its models. That line is now a categorical denial, no edit notice. Its own engineer says the new claim covers two months. We quoted the deleted sentence in #159.

Why builders care: Everything you typed before you opted out is still in scope. Only the vendor can check.

FIRST DOLLAR

📉 THE TROUGH WAS ZERO

u/dang64’s Stripe chart peaks at CA$105.24 on 31 July, then falls to CA$0 around 1 September. It reads CA$68.88 on 10 September, against a headline that says $65. He stopped posting for two and a half months to improve the product. “I wish I kept marketing.” He drives deliveries now to pay for ads. Correction: the $170 we printed for him in #72 is nowhere in the chart he just published.

🎂 APPLE SAID YES, THEN SOMEONE PAID

An r/SideProject builder started in May, got App Store approval this week, and says his first payment landed on his birthday. “While it’s only 6 bucks I couldn’t be happier.” The app is free with a paid tier at 50 a year. He never names it, and nobody asks where the customer came from.

STACK OF THE DAY

syq - A Rust file copier that rides an SSH session your laptop opens, so it needs no SSH server and no incoming port. Push files from a server down to your machine, and approve each write before it lands. MIT, 29 stars, sixteen days old. brew install greaber/tap/syq. The author posted it himself, then walked back his own tagline: “I kind of regret writing ‘better than rsync’.”

Not sponsored. We just feature tools builders would actually use.

BOOKMARKED TODAY

  • 🧪 Training a 3.8B LLM to 0.384 CORE for $998 - Evenings and weekends, debugged on a 5090 and finished on rented B200s. There’s no public repo, and the commenter who asked for one got no answer.
  • 💡 Genuine creativity is your new moat - A designer who built Flash microsites in 2006 on what stays hard to copy once copying is instant. It’s a consultancy’s blog with a book-a-call button. Top HN reply: “wasn’t it the old moat as well?”
  • ⏳ DeepSeek’s V4.1 Flash page is up - #160 said no announcement page and no benchmarks existed. Both do now. V4 Pro requests route to Flash from 04:00 UTC on 14 September.

Curated by AI, built by a human.