February 2023

I wrote a blog post.

April 2025

Claude Code lands.

I give it shell access.

It worked.

What happened?

In 20 years, I've never seen anything like this.

I stopped sleeping. I was completely obsessed.

An Avalanche

I rethought everything — software, economics, who gets to be a programmer, the future of software.

I was hooked.

The Unlock: The Feedback Loop

The agent does.

And validates.

Rince and repeat.

What Changed For Me Last 9 Months

1. Models improved
2. Harnesses improved
3. I learned — how to work with them

Same Poll, Different Worlds

𝕏: 46% write <10% of their code · Mastodon: 61% write 90-100%

Mind the adoption gap. We're living in parallel realities.

Moving Towards Agents

My goal here is to share how coding agents can work.

Hello Pi

An agent stripped to the core. No bells and whistles.

You need to understand the fundamentals before you add complexity.

Pi

A tiny system prompt and 4 tools:

read, write, edit, bash

That's it.

YOLO only. But you and it can extend itself.

Optimizing Context

Tokens are precious.

What goes in, what stays out — this is your job now.

Branch and Rewind

Agent goes astray? Rewind to earlier.

Pi's /tree rewinds with summary.

Use the newfound information to steer.

Let the Agent Build Its Own Tooling

Don't prescribe. Ask.

"What would help you validate this?"

# Test jump pad cooldown and cancellation
map assets/maps/fjord_jump.map
god on
frames 5

# Teleport near the jump pad (start is around tile 8,4 = world ~15,7)
teleport 13.0 7.0
frames 5
screenshot debug-temp/jp_01_near_pad.png

# Walk onto the jump pad
input +right
frames 20
input stop
frames 5
screenshot debug-temp/jp_02_on_pad.png

# Walk off during countdown (should cancel jump)
input +left
frames 15
input stop
frames 5
screenshot debug-temp/jp_03_cancelled.png

# Walk back onto pad and let it jump
input +right
frames 15
input stop
# Wait for countdown + jump
frames 80
screenshot debug-temp/jp_04_landed.png

# Now walk off the landing pad (should NOT jump back)
input +right
frames 30
input stop
frames 5
screenshot debug-temp/jp_05_walked_off.png

# Walk back onto landing pad (should now jump back since cooldown cleared)
input +left
frames 15
input stop
# Wait for countdown + jump if it triggers
frames 80
screenshot debug-temp/jp_06_returned.png

quit

Talk and Refine

Talk to the agent

Go back and forth

Write plan to file

Implement plan

How We Work

Emphasize human inputs.

Automate validation of outputs.

Agents in the loop.

Automate the guardrails.

Rethinking Pull Requests

Code is 100% AI generated. The human inputs matter.

We share the prompts and how we prompt.

Agent can read the Session

The Simplest Thing

We enforce unique function names (better grep) through linter

We lint away all the things we don't like

Refactorings are cheap now

Share when the agent fails

What You Just Saw

The system extended itself.

Not magic. Just tight feedback loops taken to their conclusion.

Where to use this?

Have the agent read through your sessions and analyze itself.

Have the agent do side-quests for better dev tooling.

Talk to the agent to see what it likes.

2023

"Be more careful what hammers we give that thing."

2025

It has sharp hammers.

But the constraints make it work.

The Machine Didn't Replace Me

We are the agents.

Questions?

Reach out on X: @mitsuhiko