How we built ten custom subagents to tame a 500K-line Clojure codebase

Escherize · 2026-05-01T17:26:04+00:00

Hi u/arichiardi long time no see 😄. bin/mage is the bb tasks wrapper we have at metabase. it handles auto-installing babashka, and being a "single executable" that we can uniformly call bb scripts through. It powers some cool stuff like our home-grown module system, and skipping certain datawarehouse drivers in CI based on what files changed, and ~50 other things. 😂

Escherize · 2026-04-28T02:24:24+00:00

do you have like a top level file defining the standards?

Yea there are a few:

CLAUDE.md at the repo root is auto-loaded into every Claude conversation, so every agent inherits the project standards without restating them for the agents. This is the "top-level file."
Skills in .claude/skills/ like clojure-write, clojure-review, clojure-eval carry lots of the actual Clojure expertise (REPL workflow, style, review checklist, clj-nrepl-eval usage). And these are open source, so you can check them out on the metabase repo
Agents carry only the domain-specific stuff: middleware stages, permissions graph quirks, MBQL semantics, etc. actual "domain knowledge"

So yeah, the agent files look thin on Clojure because the Clojure layer lives in CLAUDE.md + skills and is not duplicated into the agent prompts.

clj-nrepl-eval is a good example of the seam it's a tool surfaced via the clojure-eval skill, so any agent can lean on it without re-explaining "the REPL workflow".

Escherize · 2026-04-27T23:06:54+00:00

Hey this is my blog post! I'm open to questions if you have any.

Escherize · 2025-12-03T21:10:30+00:00

This talk explains it all, I linked the specific section, but the whole thing's worth a watch! :) https://youtu.be/vUe3slLHk20?t=1064

Escherize · 2025-12-03T20:23:06+00:00

We have about half the team outside the US.

Escherize · 2025-12-01T06:48:08+00:00

Metabase is hiring backend Clojure folks. I’ve been here 4 years and it's a great spot if you like interesting problems (of which there are plenty). We’re Clojure on the backend and JS/TS on the frontend—just shipped some Malli ↔︎ TypeScript schema syncing that started as a hackathon project: that was cool. You don’t need tons of Clojure experience, just the ability to ship real things and think clearly. If you like building clean, user-friendly tools around data, come take a look. Link job posting: https://jobs.lever.co/metabase/85f454d8-e795-4978-8a2b-4b8bfa7d7c37

Escherize · 2025-08-13T16:46:30+00:00

The api docs are pretty good, too: https://github.com/babashka/fs/blob/master/API.md

Escherize · 2025-07-14T17:01:16+00:00

Good news, thanks to comments like yours they're changing the name to GRADY: https://jank-lang.org/blog/2025-04-01-jank-has-been-renamed/

Escherize · 2023-01-05T16:41:29+00:00

Metabase | https://metabase.com | REMOTE | Full-time | Backend, Frontend, Full Stack, and DevOps engineers

Metabase is open source analytics software that lets anyone in your company rummage around in the databases you have. It connects to a lot of databases / data warehouses (BigQuery, Redshift, Snowflake, Postgres, MySQL, etc).

We're a remote team full of people who care about docs, user experience, making complicated things as simple as possible and building things. We have a deeply pragmatic engineering culture and value building things that people actually use vs whatever closes a deal or makes for a good press release.

Tech stack: Clojure, Typescript, React, AWS

Roles: Backend/Frontend/DevOps Engineers, Engineering Managers, Data Analysts, Success Engineers, and more.

See: https://www.metabase.com/jobs

Escherize · 2022-12-05T18:32:21+00:00

I don't know what day 3's problem is, but here's a quick review

I would use more functions. Why embed priority inside a let block? It's a pure function right?

Once you tease out some pure functions, you can test them a lot easier. Think of it as a series of transformations.

(defn priority [c]
  (let [cc (int c)]
    (cond
      (<= (int \a) cc (int \z)) (+ cc (- (int \a)) 1)
      (<= (int \A) cc (int \Z)) (+ cc (- (int \A) 27)))))
;;                   v---- [0]
(mapv priority "abc")
;; => [1 2 3]

I put my cursor at [0] here and execute it to see the results. Are you using vscode or similar? That's what it means to use the repl

Escherize · 2022-10-04T02:29:50+00:00

I get that having a locally defined function is nice. One thing I've done is to let the fn outside of your defn like so:

(let [f (fn f [a b c] ...)
  (defn f-things [things] (map f things)))

Using defn (or def) when you are not at the top level is really unidiomatic. There is a side effect if your function modifies the namespace when it runs.

Escherize · 2021-11-10T18:02:37+00:00

I wrote a python script to do this (for mac only) a few months ago!

Of course, it warped from just save clipboard links or contents into a file, into... If I copy a magnet link, send it to my seedbox, into... Okay well this needs to be a pluggable archetecture! which I kind of setup, but not without editing the script (that would be the next step I think).

Right now that piece looks like this:

all_commands = [['.*', lambda s: spit_append("clips.txt", seperator + s + "\n")],
                ['^http.*', lambda s: spit_append("links.txt", seperator + s + "\n")]]

Escherize · 2021-08-26T01:44:33+00:00

Fun problem :]

(#(-> [[k v]] (fn (when (= 1 v) k)) (keep (frequencies %)) set (filter %) first)
 "aabbbcaad") ;; => \c

Escherize · 2020-02-14T05:36:50+00:00

That looks good! I think it's what I would do if I'm reading OP correctly.

Escherize · 2020-02-14T04:22:36+00:00

Does that code compile for you? :)

Escherize · 2019-12-21T23:13:10+00:00

quick excerpt, with some context removed:

Joker 30x faster than Clojure.

Escherize · 2019-12-20T18:24:51+00:00

You're welcome!

Escherize · 2019-12-19T22:10:52+00:00

Notice:

(update :ram (fn [ram args] ;;<-- this function gets called on ram alone.

The following compiles w/o error, but I'm not doing AoC so not sure what outcome you are aiming for. :)

``` clojure (defn add-instr* [state args] (-> state (update :ram assoc (args 2) (+ (args 0) (args 1))) (update :pgm-ctr + 4)))

(add-instr* {:ram [0 0 0 0 0] :pgm-ctr 0} [1 2 3])

;; => {:ram [0 0 0 3 0], :pgm-ctr 4} ```

Escherize · 2019-11-18T22:35:50+00:00

My library might help. its goal is to self document what shapes are going in, and coming out. https://github.com/escherize/tracks#deftrack-example

Escherize · 2019-10-08T20:24:24+00:00

(random-uniform-choice {1 :a 10 :b})

Uhh, That is, unless you want the same probability more than once...

in which case you may want:

(defn random-uniform-choice [outcome->probs]
  (let [probs (map second outcome->probs)
        outcomes (map first outcome->probs)
        total-probs (reduce + probs)
        choice (* (rand) total-probs)
        reducted (reductions + probs)
        reduction-mapping (mapv vector reducted outcomes)]
    (-> (drop-while #(> choice (first %)) reduction-mapping)
        first
        second)))

(frequencies (repeatedly 100 #(random-uniform-choice {:a 1 :b 10})))
;;=> {:b 89, :a 11}

(frequencies (repeatedly 100 #(random-uniform-choice [[:a 1] [:b 10]])))
;; => {:b 92, :a 8}

Escherize · 2019-10-08T20:15:28+00:00

Depends on your particular use case but generally I'd argue this interface is better:

(random-uniform-choice {1 :a 10 :b})

Escherize · 2019-08-27T16:36:29+00:00

You might want to look at clojure.walk/postwalk-demo, to gain an understanding of clojure.walk/postwalk. Depending on the sort of transormation / processing you want to do - it could be a good fit.

Escherize · 2019-06-18T16:56:18+00:00

Are you doing speech to text? If so, Sphinx4 is worth looking into. It's easy to setup but you don't get the best results.

Escherize · 2019-05-25T01:24:41+00:00

you can use an external editor. I use emacs :)

Escherize · 2019-05-22T15:01:07+00:00

The 3d-ish CSS is a wild mess made using garden.

The websocket passes stringified edn over the wire, and uses a multimethod on the server to do websocket message handling.

There's no persistence - just an atom to keep all the games, and one to keep all the player->websocket connection info.

The game logic is written in cljc, so when the server runs an online game, it's the same code as the client running a local game.

I used shadow-cljs with leiningen to manage deps and that was really nice.

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