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Weekly notes on building with AI

What I tried this week, what worked, what didn't. One post a week, ~5-minute read each. Sent to the newsletter list every Sunday.

Why your AI's self-check misses its own mistakes, and the subagent recipe that catches them

A same-thread "double-check this" rarely surfaces the error, because the model reviewing it shares the blind spot with the model that produced it. The fix is a fresh, independent subagent whose only job is to try to disprove the output, and the Claude Code file that builds one.

Four AI labs spent $9 billion in eight weeks hiring the engineers you compete with

Anthropic, OpenAI, AWS, and Microsoft each launched a billion-dollar unit that embeds engineers inside enterprise customers to build production AI systems. Two are outside-funded joint ventures, two are internal cost centers, and that difference tells you exactly what each one is actually selling.

ChatGPT Sites just left limited preview: what it replaces, and what it still cannot do

OpenAI rolled ChatGPT Sites into public beta on July 9 as part of the broader ChatGPT Work launch — describe a web app in plain English, Codex builds and hosts it, you get a shareable URL. Before you drop a Lovable or v0 subscription, here are the specific gaps that matter.

GPT-5.6 is generally available: run the Terra migration test today

The government review that gated GPT-5.6 to roughly 20 organizations completed on July 9. Sol, Terra, and Luna are now reachable through the API for any developer. Here is the specific test to run before you move production traffic.

Your Claude Code Explore subagent might be running on Opus without you asking

Since Claude Code v2.1.198, the built-in Explore subagent no longer defaults to Haiku — it inherits your main session's model, capped at Opus. If you switch to Opus for a hard problem, every grep-style delegation after that rides along at Opus rates. Here is the exact override, the single env var that controls every subagent at once, and the pricing math behind why it matters.

Search your coding agent's own session history instead of re-explaining it

Every new Claude Code, Cursor, or Codex session starts blind to everything you already worked out together. ctx indexes the session logs already sitting on your machine into local SQLite, so the next session can search its own past instead of you retyping the context. Verified end to end on a real multi-tool session history.

Frontier AI is going metered: put a per-task price on your model spend

Fable 5 returned on July 1, but after July 7 it lives outside every Claude subscription as usage credits. The same week, Anthropic shipped spend alerts and model entitlements for Enterprise admins, and Tesla reportedly capped employee AI spend at $200 per week. The flat-rate era is ending; here is how to budget by task instead of by seat.

Automate a weekly competitor watch with a Claude Code skill and a routine

A recurring, rules-based check like "did a competitor change their pricing page" is exactly what should run itself. Here is how to wire a skill and a cloud routine together so it does — including the network-access gotcha that makes it silently do nothing while showing green.

Claude Sonnet 5 is cheap enough to be your default — check the token bill first

Anthropic shipped Sonnet 5 on June 30 at $2/$10 per million tokens through August, close to Opus 4.8 quality. The catch is a new tokenizer that counts up to 1.35x more tokens, so the rate card understates your real spend. Here is how to decide which work to move, how to set it up, and what to do before the price step on September 1.

How to get reliable JSON from Claude and GPT

Asking an LLM to 'return JSON' works in demos and breaks in production. Three concrete approaches — OpenAI's response_format, Anthropic's forced tool_choice, and the Instructor library — that actually hold, and the failure modes each one leaves open.

GPT-5.6 Sol, Terra, and Luna: confirmed pricing and what the staged rollout means for your Q3 stack

Sol at $5/$30, Terra at $2.50/$15, Luna at $1/$6 per million tokens. OpenAI launched GPT-5.6 in limited preview on June 26 with access staged by White House request. The pricing is real and plannable now. The access is not yet open.

OpenAI's first custom chip: what Jalapeño means for inference costs

OpenAI and Broadcom announced Jalapeño, a custom ASIC built for LLM inference. Nothing changes today. Here's the mental model for what custom silicon does to API pricing — using Google's TPUs as the documented precedent.

Build a 20-case eval set for your AI feature (with promptfoo)

Green CI is not evidence the feature works. A concrete walkthrough: the 20 cases to write, the promptfoo config to run them, the four patterns to look for in the results, and the moment you decide whether to ship.

Claude Fable 5 is suspended — what it means if you build on Claude

Nine days after a US government export control directive pulled Claude Fable 5 and Mythos 5 from every user worldwide, the models remain offline. Here's what happened, what still works, and what to do if you build on Claude.

Gemini CLI stops serving Pro, Ultra, and free users today

As of June 18, 2026, Gemini CLI and the Gemini Code Assist IDE extensions stop serving requests for Pro, Ultra, and free-tier users. Here's exactly who's affected, what keeps working, and what Antigravity CLI does and doesn't carry over.

SpaceX is acquiring Cursor for $60 billion

SpaceX agreed to buy Cursor (Anysphere) for $60 billion in SpaceX stock — four days after the company's IPO. Here's what happened, why, and what it means if you build with Cursor.

MCP in plain English — and what to install first

Your AI knows everything about the internet and nothing about your stack. MCP is the boring protocol that fixed that. Here's what it actually is, what it isn't, and the three servers worth installing this afternoon.

How to write AGENTS.md so AI doesn't break your repo

The first thing your AI reads is a file you may not have written yet. AGENTS.md, CLAUDE.md, .cursorrules — same idea, different name. What to put in it, what to leave out, and how to have Claude draft one without getting 400 lines of generic filler.

How to review an AI-generated PR

47 files changed, green CI, an AI-written description, and 30 seconds to approve. That's the failure mode. Here's a 12-point review checklist that catches what the AI got wrong — and how to scope the review so you'll use it.

Stop prompting. Start observing.

Before AI can replace any part of your week, you have to see your week clearly. The one-week audit, the four-bucket sort, and the trap of automating work that shouldn't exist at all.

The goldmine is the workflow

Most people look for AI startup ideas in the wrong place. The best products usually start by compressing a workflow people already repeat every week.

Your AI tests aren't actually testing anything

AI is great at generating green CI. It's worse at generating tests that catch real bugs. Five patterns I see in the wild — and a checklist to run before you trust an AI-written test suite.

Before you ship — a pre-deploy checklist for AI-built apps

AI builders make 90% of the right decisions and 10% of the catastrophically wrong ones. The wrong ones cluster in predictable places. Here's the 24-point checklist to run through before you deploy — copy-paste version included.

Most AI-built apps shouldn't be on the internet

AI builders can ship v1 in a weekend. They can also bankrupt you, leak user data, and put your API keys on display by Sunday afternoon. What actually breaks — and what to do about it.

Your AI is confidently wrong

It's not the security holes that drain your wallet. It's the loops, the hallucinations, and the rewrites that fix nothing. The failures nobody puts in the demo — and what they actually cost.

Welcome — what this blog is and isn't

One post a week, every Sunday. Patterns, pitfalls, and checklists for building with AI. No daily spam, no AI-generated thinkpieces, no 30-item link dumps.