app/priv/blog/engineering/2026/04-19-coding-agent-generates-its-own-extensions.md

@@ -1,83 +0,0 @@
-%{
-  title: "Coding agent generates its' own extensions",
-  author: "Willem van den Ende",
-  tags: ~w(ai loops),
-  description: "Handwritten note about generating extensions for the coding agent you are in a session with on something else. Engineer solutions in the moment.",
-  published: true
-}
----
-
-_This post was written longhand. Conversion to text was done with MyScript Notes, I did some minor manual edits to correct words and explain a few things (in parentheses).
-
-
-I see a few people writing about sharing struggles with Large language models, saying we are all still figuring this out.
-
-For me it is easier to do at the moment of a small success.
-
-The other day I tried to develop an extension for [Pi](https://shittycodingagent.ai) model when it goes off the rails.
-
-I now have a local model that is fast, can call tools (search, run test,  edit code etc.). It does, however, perform some model assisted coding quirks frequently:
-
-- Replace production code that Works With throwing an exception
-- Write if statements in tests
-- Add fallbacks for things that can't fail
-- Find "problems" in code that works (passes tests + other checks, works for the user etc)
-
-Long term the solution probably is to work in small steps. But these steps come from experience.
-
-Catching the problem when it happens by simply matching some words is a starting point for that: scan for key words in any edits and prompt the user for permission. Just abort when the session is not interactive.
-
-Looks simple, so I let a more powerful but slower local model figure out how to build an extensions. Every Pi session opens with an invitation:
-
-> Pi can explain its own features and look up its docs. Ask it how to use or extend Pi.
-
-After some iteration we had a plan and Pi generated d plausible looking extension.
-
-I tested it manually, in Pi. Nothing happened. Back to the drawing board.
-
-I had quite a few iterations, compared with sample code, looked into the Pi API.
-No luck.
-
-Eventually I installed the sample extension. That worked. Then I deleted most of my
-extension, added some logging - I could see something.
-
-I learned quite a bit about Pi and its extension mechanism.
-
-It looks like only the last "UI notification" gets shown for any exension point (e.g. a tool call or system startup). I am not yet sure if this is by design or not.
-
-I did take away that, here too, I want to work test-first for parts that do not interface
-with the agent directly. The feedback loop is just too slow otherwise.
-
-This also required experimentation. I did not want to set up a separate project for an extension that is little more than an idea. But I do want tests. So I asked a model again. The suggestion was to use Deno, because that has testing built in. Some more fiddling followed:
-
-- Get [deno](https://deno.com/) to work in the [nono](https://nono.sh/cli) sandbox
-- Learn that Pi auto loads any thing in the extensions folder. If you put a test there, Pi crashes. (the test does not have the method that defines an extension. All files in `.pi/agent/extensions` must have it.)
-- Learn that "domain" files also don't work there. (I wanted to have the extension files thin and the testable functions separate. So that the tests don't depend on `pi` and its' types).
-
-![handwritten draft of the paragraph below](/images/blog/2026/local-llm-handwriting.png)
-
-
-So eventually I ended up with
-
-```
-- .pi / test
-	  / core
-	  / extensions
-```
-
-`Core` contains the functional cores, `test` tests the core. `Extensions` is a thin integration with Pi that uses the core. (the Deno project lives in )
-
-This was clear enough that the slow, dense model could build a second extension and performance metrics in chat, with relatively little guidance after iterations on a plan.
-
-I haven't looked at the code yet (in detail). not out of principle, but because it is late,
-and I want to write down my trial and error before I forget.
-
-Afterword
----
-
-I hope you enjoyed this slowly written note. I have added the
-[handwritten draft](/images/blog/2026/coding-agent-generates-extensions-handwritten.pdf) as pdf. 
-
-I found writing in long hand helped me slow down and step away from the slot machine that wishcraft can be sometimes.
-
-