In this post I'll give updates about open source I worked on during September and October 2025.

To see previous OSS updates, go here.

Sponsors

I'd like to thank all the sponsors and contributors that make this work possible. Without you, the below projects would not be as mature or wouldn't exist or be maintained at all! So a sincere thank you to everyone who contributes to the sustainability of these projects.

Current top tier sponsors:

• Clojurists Together
• Roam Research
• Nextjournal
• Nubank

Open the details section for more info about sponsoring.

Updates

The summer heat has faded, and autumn is upon us. One big focus for me is preparing my talk for Clojure Conj 2025, titled "Making tools developers actually use". I did a test run of the talk at the Dutch Clojure Meetup. It went a bit too long at 45 minutes, so I have to shrink it almost by half for the Conj. The more I work on the talk the more ideas come up, so it's challenging!

Of course I spent a ton of time on OSS the past two months as well. Some special mentions:

• I'm pretty excited by Eucalypt, a remake of Reagent for Squint without React by Chris McCormick. It lets you build UIs with the Reagent API in less than 10kb of gzip'ed JS. The code was initially generated by an LLM, but now work is going into making the code base thoroughly tested and simplified where possible.
• After studying Eucalypt's code I figured that making an even more minimal Reagent-like by hand would be fun. This is where I came up with Reagami. The API looks like a hybrid between Reagent and Replicant. You can build apps with Reagami starting around 5kb gzip'ed.
• Edamame got Clojure CLR support thanks to Ambrose Bonnaire-Sergeant.
• SCI Clojure CLR support is underway. The sci.impl.Reflector code, based on clojure.lang.Reflector was ported to Clojure with the purpose that it would then be easier to translate to Clojure CLR.
• Cljdoc chose squint for its small bundle sizes and easy migration off of TypeScript towards CLJS
• Via work on Squint, I found a way to optimize str in ClojureScript (worst case 4x, best case 200x)

Here are updates about the projects/libraries I've worked on in the last two months in detail.

• babashka: native, fast starting Clojure interpreter for scripting.

  • Bump to clojure 1.12.3
  • #1870: add .addMethod to clojure.lang.MultiFn
  • #1869: add clojure.lang.ITransientCollection for instance? checks
  • #1865: support reify + equals + hashCode on Object
  • Add java.nio.charset.CharsetDecoder, java.nio.charset.CodingErrorAction, java.nio.charset.CharacterCodingException in support of the sfv library
  • Fix nrepl-server completions and lookup op to be compatible with rebel-readline
  • Add clojure.lang.Ref for instance? checks
  • Bump SCI: align unresolved symbol error message with Clojure
  • Use GraalVM 25
  • Bump deps.clj to 1.12.3.1557
  • Change unknown or REPL file path to NO_SOURCE_PATH instead of <expr> since this can cause issues on Windows when checking for absolute file paths
  • #1001: fix encoding issues on Windows in Powershell. Also see this GraalVM issue
  • Fixes around java.security and allowing setting deprecated Cipher suites at runtime. See this commit.
  • Support Windows Git Bash in bash install script

• SCI: Configurable Clojure/Script interpreter suitable for scripting

  • ClojureCLR support in progress (with Ambrose Bonnaire Sergeant)

• edamame: configurable EDN and Clojure parser with location metadata and more

  • 1.5.33 (2025-10-28)
  • Add ClojureCLR support (@frenchy64)

• clj-kondo: static analyzer and linter for Clojure code that sparks joy.
  

  • Unreleased
  • #2651: resume linting after paren mismatches
  • 2025.10.23
  • #2590: NEW linter: duplicate-key-in-assoc, defaults to :warning
  • #2639: NEW :equals-nil linter to detect (= nil x) or (= x nil) patterns and suggest (nil? x) instead (@conao3)
  • #2633: support new defparkingop macro in core.async alpha
  • #2635: Add :interface flag to :flags set in :java-class-definitions analysis output to distinguish Java interfaces from classes (@hugoduncan)
  • #2636: set global SCI context so hooks can use requiring-resolve etc.
  • #2641: fix linting of def body, no results due to laziness bug
  • #1743: change :not-empty? to only warn on objects that are already seqs
  • Performance optimization for :ns-groups (thanks @severeoverfl0w)
  • Flip :self-requiring-namespace level from :off to :warning
  • 2025.09.22
  • Remove dbg from data_readers.clj since this breaks when using together with CIDER
  • 2025.09.19
  • #1894: support destruct syntax
  • #2624: lint argument types passed to get and get-in (especially to catch swapped arguments to get in threading macros) (@borkdude, @Uthar)
  • #2564: detect calling set with wrong number of arguments
  • #2603: warn on :inline-def with nested deftest

• squint: CLJS syntax to JS compiler

  • Support passing keyword to mapv
  • Inline identical? calls
  • Clean up emission of paren wrapping
  • Add nat-int?, neg-int?, pos-int? (@eNotchy)
  • Add rand
  • Fix rendering of null and undefined in #html
  • #747: #html escape fix
  • Optimize nested assoc calls, e.g. produced with ->
  • Avoid object spread when object isn't shared (auto-transient)
  • Optimize =, and, and not= even more
  • not= on undefined and false should return true
  • Optimize code produced for assoc, assoc! and get when object argument can be inferred or is type hinted with ^object
  • Optimize str using macro that compiles into template strings + ?? '' for null/undefined
  • Fix #732: take-last should return nil or empty seq for negative numbers
  • #725: keys and vals should work on js/Map
  • Make map-indexed and keep-indexed lazy
  • Compile time optimization for = when using it on numbers, strings or keyword literals
  • Switch = to a deep-equals implementation that works on primitives, objects, Arrays, Maps and Sets
  • Fix #710: add parse-double
  • Fix #714: assoc-in on nil or undefined
  • Fix #714: dissoc on nil or undefined
  • Basic :import-maps support in squint.edn (just literal replacements, prefixes not supported yet)

• reagami: A minimal zero-deps Reagent-like for Squint and CLJS

  • First releases

• clerk: Moldable Live Programming for Clojure

  • Support evaluation of quoted regex
  • Support macros defined in notebooks
  • Bump cherry

• cljs-str

  • More efficient drop-in replacement for CLJS str. This work was already upstreamed into CLJS, so coming near you in the next CLJS release.

• unused-deps: Find unused deps in a clojure project

  • Support finding unused git deps

• scittle: Execute Clojure(Script) directly from browser script tags via SCI

  • Fix SCI regression where interop on keywords like (.catch ...) was accidentally munched

• Nextjournal Markdown

  • Add :start attribute to ordered lists not starting with 1 (@spicyfalafel)

• cherry: Experimental ClojureScript to ES6 module compiler

  • Bump squint compiler common component and standard library
  • Bump other deps
  • Optimize =, str, not=
  • Support :macros option + :refer so you can use unqualified macros using compiler state (see macro-state-test)

• deps.clj: A faithful port of the clojure CLI bash script to Clojure

  • Released several versions catching up with the clojure CLI

• pod-babashka-go-sqlite3: A babashka pod for interacting with sqlite3

  • Add close-connection
  • Fix #38: add get-connection to cache connection
  • Fix potential memory leak
  • Better handling of parent process death by handling EOF of stdin
  • #25: use musl to compile linux binaries to avoid dependency on glibc

• quickdoc: Quick and minimal API doc generation for Clojure

  • Fix extra newline in codeblock

Contributions to third party projects:

• ClojureScript

  • Optimize str (4x worst case, 200x best case)
  • Make munge-str public

• Selmer

  • Handle error for template without closing delimiter

• clojure-lsp

  • Optimize :ns-groups handling by caching regex creation and usage

Other projects

These are (some of the) other projects I'm involved with but little to no activity happened in the past month.