Better with Kent · draft

Better with Kent

Durable skills for people who ship software

Today: the system behind a 50,000-line production rewrite — not a magic prompt.

Cold open

The artifact

kentcdodds.com — real users, real data, real production.

Six migrations in one

• Fly → Cloudflare Workers
• SQLite/LiteFS → D1 + read replication
• Prisma → @remix-run/data-table
• Cloudinary → R2 + Images

• Mailgun → Cloudflare email
• OG images → Satori
• Constraint: total feature parity

The hard part

MDX without server eval

227/227 posts render-parity verified · content updates without redeploy

Architecture

Parent vs dynamic worker

flowchart LR
  req["Request"] --> parent["Parent worker"]
  parent -->|"cache HIT"| kv["KV HTML"]
  parent -->|"MISS / BYPASS"| dyn["Dynamic worker SSR"]
  dyn --> kvfill["fills page cache"]

Wrong: "every HTML render hits the dynamic worker." Right: parent often serves cached HTML.

Kickoff

Prompt the system

~4,200 characters · one message to start · orchestrator owns the rest

• Goals + constraints + feature parity
• Quality bar and exit criteria in the prompt

Five parts of the prompt

Composer 2.5 subagents for cost + speed

The closer

One prompt — then hands off

"This is the only prompt you're going to receive from me. This job is yours now."

Orchestration in action

• 12 Composer 2.5 agents — parity, perf, errors
• 5 audit + 3 cleanup subagents — cruft sweep
• Agent shipped site tour + hydration screenshots unprompted

Honest story

Steering ≠ abdication

• 50 messages over 5 days
• Hard cutover — no parallel-run cruft
• "Cloudinary completely out" — said four times

Three-layer review

Each layer catches a different class of bug

Hard to reverse

What review caught

• /blog page-cache privacy leak
• Unauthenticated OG signing → SSRF
• Image masters one cancellation from gone

Kody closes the loop

• Scoped CF token · DNS inspection · deploys
• 300MB image archive to R2 from inside a worker
• Review agents → working agent — no human relay

The twist setup

Perf scare

"I should definitely not switch."

Verify the verifier

• Meta-agent: hot Fly vs cold staging — unfair benchmark
• Warm cache HITs: 18–29ms — beat Fly
• Real regression: cache-miss dynamic only

2026-07-08

Shipped

• PR #813 merged · DNS flipped · live on Workers
• Fly SQLite → D1 · sessions intact
• Steady state: anonymous traffic → warm KV cache

Post-cutover cleanup

Cloud agent bc-c349545a · spawned via Kody

• Archive migration tooling · rate-limit rules
• Destroy Fly / cancel Cloudinary — asks first

Migration ends at DNS flip; teardown is a separate guarded job.

Homework

Before your next merge, spawn one agent: "Flag anything hard to reverse and any gaping security or perf holes."

~20 minutes · works on any open PR diff

Better with Kent

Prompt the system — verify the verifier

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