In this post I'll give updates about open source I worked on during November and December 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

Clojure Conj 2025

Last November I had the honor and pleasure to visit the Clojure Conj 2025. I met a host of wonderful and interesting long-time and new Clojurians, many that I've known online for a long time and now met for the first time. It was especially exciting to finally meet Rich Hickey and talk to him during a meeting about Clojure dialects and Clojure tooling. The talk that I gave there: "Making tools developers actually use" will come online soon.

Babashka conf and Dutch Clojure Days 2026

In 2026 I'm organizing Babashka Conf 2026. It will be an afternoon event (13:00-17:00) hosted in the Forum hall of the beautiful public library of Amsterdam. More information here. Get your ticket via Meetup.com (currently there's a waiting list, but more places will come available once speakers are confirmed). CfP will open mid January. The day after babashka conf, Dutch Clojure Days 2026 will be happening. It's not too late to get your talk proposal in. More info here.

Projects

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 process to 0.6.25
  • Bump deps.clj
  • Fix #1901: add java.security.DigestOutputStream
  • Redefining namespace with ns should override metadata
  • Bump nextjournal.markdown to 0.7.222
  • Bump edamame to 1.5.37
  • Fix #1899: with-meta followed by dissoc on records no longer works
  • Bump fs to 0.5.30
  • Bump nextjournal.markdown to 0.7.213
  • Fix #1882: support for reifying java.time.temporal.TemporalField (@EvenMoreIrrelevance)
  • Bump Selmer to 1.12.65
  • SCI: sci.impl.Reflector was rewritten into Clojure
  • dissoc on record with non-record field should return map instead of record
  • Bump edamame to 1.5.35
  • Bump core.rrb-vector to 0.2.0
  • Migrate detecting of executable name for self-executing uberjar executable from ProcessHandle to to native image ProcessInfo to avoid sandbox errors
  • Bump cli to 0.8.67
  • Bump fs to 0.5.29
  • Bump nextjournal.markdown to 0.7.201

• SCI: Configurable Clojure/Script interpreter suitable for scripting

  • Add support for :refer-global and :require-global
  • Add println-str
  • Fix #997: Var is mistaken for local when used under the same name in a let body
  • Fix #1001: JS interop with reserved js keyword fails (regression of #987)
  • sci.impl.Reflector was rewritten into Clojure
  • Fix babashka/babashka#1886: Return a map when dissociating a record basis field.
  • Fix #1011: reset ns metadata when evaluating ns form multiple times
  • Fix for https://github.com/babashka/babashka/issues/1899
  • Fix #1010: add js-in in CLJS
  • Add array-seq

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

  • #2600: NEW linter: unused-excluded-var to warn on unused vars in :refer-clojure :exclude (@jramosg)
  • #2459: NEW linter: :destructured-or-always-evaluates to warn on s-expressions in :or defaults in map destructuring (@jramosg)
  • Add type checking support for sorted-map-by, sorted-set, and sorted-set-by functions (@jramosg)
  • Add new type array and type checking support for the next functions: to-array, alength, aget, aset and aclone (@jramosg)
  • Fix #2695: false positive :unquote-not-syntax-quoted in leiningen's defproject
  • Leiningen's defproject behavior can now be configured using leiningen.core.project/defproject
  • Fix #2699: fix false positive unresolved string var with extend-type on CLJS
  • Rename :refer-clojure-exclude-unresolved-var linter to unresolved-excluded-var for consistency
  • v2025.12.23
  • #2654: NEW linter: redundant-let-binding, defaults to :off (@tomdl89)
  • #2653: NEW linter: :unquote-not-syntax-quoted to warn on ~ and ~@ usage outside syntax-quote (`) (@jramosg)
  • #2613: NEW linter: :refer-clojure-exclude-unresolved-var to warn on non-existing vars in :refer-clojure :exclude (@jramosg)
  • #2668: Lint & syntax errors in let bindings and lint for trailing & (@tomdl89)
  • #2590: duplicate-key-in-assoc changed to duplicate-key-args, and now lints dissoc, assoc! and dissoc! too (@tomdl89)
  • #2651: resume linting after paren mismatches
  • clojure-lsp#2651: Fix inner class name for java-class-definitions.
  • clojure-lsp#2651: Include inner class java-class-definition analysis.
  • Bump babashka/fs
  • #2532: Disable :duplicate-require in require + :reload / :reload-all
  • #2432: Don't warn for :redundant-fn-wrapper in case of inlined function
  • #2599: detect invalid arity for invoking collection as higher order function
  • #2661: Fix false positive :unexpected-recur when recur is used inside clojure.core.match/match (@jramosg)
  • #2617: Add types for repeatedly (@jramosg)
  • Add :ratio type support for numerator and denominator functions (@jramosg)
  • #2676: Report unresolved namespace for namespaced maps with unknown aliases (@jramosg)
  • #2683: data argument of ex-info may be nil since clojure 1.12
  • Bump built-in ClojureScript analysis info
  • Fix #2687: support new :refer-global and :require-global ns options in CLJS
  • Fix #2554: support inline configs in .cljc files

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

  • Minor: leave out :edamame/read-cond-splicing when not splicing
  • Allow :read-cond function to override :edamame/read-cond-splicing value
  • The result from :read-cond with a function should be spliced. This behavior differs from :read-cond + :preserve which always returns a reader conditional object which cannot be spliced.
  • Support function for :features option to just select the first feature that occurs

• squint: CLJS syntax to JS compiler

  • Allow macro namespaces to load "node:fs", etc. to read config files for conditional compilation
  • Don't emit IIFE for top-level let so you can write let over defn to capture values.
  • Fix js-yield and js-yield* in expression position
  • Implement some? as macro
  • Fix #758: volatile!, vswap!, vreset!
  • pr-str, prn etc now print EDN (with the idea that you can paste it back into your program)
  • new #js/Map reader that reads a JavaScript Map from a Clojure map (maps are printed like this with pr-str too)
  • Support passing keyword to mapv
  • #759: doseq can't be used in expression context
  • Fix #753: optimize output of dotimes
  • alength as macro

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

  • Performance enhancements
  • treat innerHTML as a property rather than an attribute
  • Drop support for camelCased properties / (css) attributes
  • Fix :default-value in input range
  • Support data param in :on-render
  • Support default values for uncontrolled components
  • Fix child count mismatch
  • Fix re-rendering/patching of subroots
  • Add :on-render hook for mounting/updating/unmounting third part JS components

• NEW: parmezan: fixes unbalanced or unexpected parens or other delimiters in Clojure files

• CLI: Turn Clojure functions into CLIs!

  • #126: - value accidentally parsed as option, e.g. --file -
  • #124: Specifying exec fn that starts with hyphen is treated as option
  • Drop Clojure 1.9 support. Minimum Clojure version is now 1.10.3.

• clerk: Moldable Live Programming for Clojure

  • always analyze doc (but not deps) when no-cache is set (#786)
  • add option to disable inline formulas in markdown (#780)

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

  • #114: Enable source maps (@jeroenvandijk)
  • #140: Enable customizing the nrepl websocket port (@PEZ)
  • Bump shadow-cljs and SCI

• Nextjournal Markdown

  • Add config option to avoid TeX formulas
  • API improvements for passing options

• cherry: Experimental ClojureScript to ES6 module compiler

  • Fix cherry compile CLI command not receiving file arguments
  • Bump shadow-cljs to 3.3.4
  • Fix #163: Add assert to macros (@willcohen)
  • Fix #165: Fix ClojureScript protocol dispatch functions (@willcohen)
  • Fix #167: Protocol dispatch functions inside IIFEs; bump squint accordingly
  • Fix #169: fix extend-type on Object
  • Fix #171: Add satisfies? macro (@willcohen)

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

  • Released several versions catching up with the clojure CLI

• quickdoc: Quick and minimal API doc generation for Clojure

  • Fix extra newline in codeblock

• quickblog: light-weight static blog engine for Clojure and babashka

  • Add support for a blog contained within another website; see Serving an alternate content root in README. (@jmglov)
  • Upgrade babashka/http-server to 0.1.14
  • Fix :blog-image-alt option being ignored when using CLI (bb quickblog render)

• nbb: Scripting in Clojure on Node.js using SCI

  • #395: fix vim-fireplace infinite loop on nREPL session close.
  • Add ILookup and Cons
  • Add abs
  • nREPL: support "completions" op

• neil: A CLI to add common aliases and features to deps.edn-based projects.
  

  • neil.el - a hook that runs after finding a package (@agzam)
  • neil.el - adds a function for injecting a found package into current CIDER session (@agzam)
  • #245: neil.el - neil-executable-path now can be set to clj -M:neil
  • #251: Upgrade library deps-new to 0.10.3
  • #255: update maven search URL

• fs - File system utility library for Clojure

  • #154 reflect in directory check and docs that move never follows symbolic links (@lread)
  • #181 delete-tree now deletes broken symbolic link root (@lread)
  • #193 create-dirs now recognizes sym-linked dirs on JDK 11 (@lread)
  • #184: new check in copy-tree for copying to self too rigid
  • #165: zip now excludes zip-file from zip-file (@lread)
  • #167: add root fn which exposes Path getRoot (@lread)
  • #166: copy-tree now fails fast on attempt to copy parent to child (@lread)
  • #152: an empty-string path "" is now (typically) understood to be the current working directory (as per underlying JDK file APIs) (@lread)
  • #155: fs/with-temp-dir clj-kondo linting refinements (@lread)
  • #162: unixify no longer expands into absolute path on Windows (potentially BREAKING)
  • Add return type hint to read-all-bytes

• process: Clojure library for shelling out / spawning sub-processes

  • #181: support :discard or ProcessBuilder$Redirect as :out and :err options

Contributions to third party projects:

• ClojureScript
  • CLJS-3466: support qualified method in return position
  • CLJS-3468: :refer-global should not make unrenamed object available

Other projects

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

Dear sponsors,

As we approach Thanksgiving once again, I’m reminded that sustained open source software development, supported by long term sponsors, is not something to take for granted.

I’m genuinely grateful for your ongoing support through GitHub Sponsors. Your contributions make a real difference: my Clojure projects wouldn’t be nearly as polished, maintained, or ambitious without your help.

If you’d like to look back on what happened in open source this past year, you can find an overview here: https://blog.michielborkent.nl/tags/oss-updates.html. The core projects remain clj-kondo, babashka, SCI, scittle, and squint/cherry. Each of them continues to grow in capability and adoption.

I’ve also applied for Clojurists Together again for 2026. If you’re a CT sponsor, a vote in the next long-term funding round would be appreciated.

Here are the main ideas I want to explore in 2026:

• Clj-kondo: run macros directly from source code
• Clj-kondo: run exported configs/hooks directly from classpath (instead of having to copy files to a local dir)
• Squint/Cherry: browser nREPL support
• Squint/Cherry: source maps
• Squint: protocolize coll functions so you can extend them to e.g. ImmutableJS or other custom collections
• Scittle2 (working name): better/faster/smaller version of Scittle using Cherry (in-browser CLJS compiler)
• Babashka: support CIDER middleware from source directly in bb
• Babashka: distinguished parallel task output (e.g. colors or prefix)
• Clj-kondo: add first-class support for Clojure dialects like ClojureDart and Jank
• Clojure CLI: help improve UX via a new tools working group
• Clj-kondo: performance improvements for bigger projects

I can't make any promises on hard deadlines, but I definitely intend to work toward realizing the above goals.

Aside from software development, I'm also organizing Babashka Conf 2026 the day before Dutch Clojure Days.

As always, feel free to reach out anytime, whether here, on Clojurians Slack, or by email at michielborkent@gmail.com. I love hearing about what you are doing with my projects. Also if you are struggling with something, let me know. Your feedback and use cases continue to shape the direction of my work.

Here’s to another strong year of Clojure OSS!

Thank you for making this journey possible.

With appreciation,

Michiel Borkent / @borkdude

PS: if you aren't sponsoring, but are interested, here are the main ways to do so:

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.