Babashka is a fast-starting native Clojure scripting runtime. It uses SCI to interpret Clojure and compiles to a native binary via GraalVM, giving you Clojure's power with near-instant startup. It's commonly used for shell scripting, build tooling, and small CLI applications. If you don't yet have bb installed, you can with brew:

brew install borkdude/brew/babashka

or bash:

bash <(curl -s https://raw.githubusercontent.com/babashka/babashka/master/install)

This release is, in my opinion, a game changer. With JLine3 bundled, you can now build full terminal user interfaces in babashka. The bb repl has been completely overhauled with multi-line editing, completions, and eldoc. deftype now supports map interfaces, making bb more compatible with existing libraries like core.cache. SCI has had many small improvements, making riddley compatible too. Riddley is used in Cloverage, a code coverage library for Clojure, which now also works with babashka (Cloverage PR pending).

Babashka conf 2026

But first, let me mention an exciting upcoming event! Babashka conf is happening again for the second time! The first time was 2023 in Berlin. This time it's in Amsterdam. The Call for Proposals is open until the end of February, so there is still time to submit your talk or workshop. We are also looking for one last gold sponsor (500 euros) to cover all costs.

Highlights

JLine3 and TUI support

Babashka now bundles JLine3, a Java library for building interactive terminal applications. You get terminals, line readers with history and tab completion, styled output, keyboard bindings, and the ability to reify custom completers, parsers, and widgets — all from bb scripts.

JLine3 works on all platforms, including Windows PowerShell and cmd.exe.

Here's a simple interactive prompt that reads lines from the user until EOF (Ctrl+D):

(import '[org.jline.terminal TerminalBuilder]
        '[org.jline.reader LineReaderBuilder])

(let [terminal (-> (TerminalBuilder/builder) (.build))
      reader   (-> (LineReaderBuilder/builder)
                   (.terminal terminal)
                   (.build))]
  (try
    (loop []
      (when-let [line (.readLine reader "prompt> ")]
        (println "You typed:" line)
        (recur)))
    (catch org.jline.reader.EndOfFileException _
      (println "Goodbye!"))
    (finally
      (.close terminal))))

babashka.terminal namespace

A new babashka.terminal namespace exposes a tty? function to detect whether stdin, stdout, or stderr is connected to a terminal:

(require '[babashka.terminal :refer [tty?]])

(when (tty? :stdout)
  (println "Interactive terminal detected, enabling colors"))

This accepts :stdin, :stdout, or :stderr as argument. It uses JLine3's terminal provider under the hood.

This is useful for scripts that want to behave differently when piped vs. run interactively, for example enabling colored output or progress bars only in a terminal.

charm.clj compatibility

charm.clj is a new Clojure library for building terminal user interfaces using the Elm architecture (Model-Update-View). It provides components like spinners, text inputs, lists, paginators, and progress bars, with support for ANSI/256/true color styling and keyboard/mouse input handling.

charm.clj is now compatible with babashka (or rather, babashka is now compatible with charm.clj), enabled by the combination of JLine3 support and other interpreter improvements in this release. This means you can build rich TUI applications that start instantly as native binaries.

Here's a complete counter example you can save as a single file and run with bb:

#!/usr/bin/env bb

(babashka.deps/add-deps
 '{:deps {io.github.TimoKramer/charm.clj {:git/sha "cf7a6c2fcfcccc44fcf04996e264183aa49a70d6"}}})

(require '[charm.core :as charm])

(def title-style
  (charm/style :fg charm/magenta :bold true))

(def count-style
  (charm/style :fg charm/cyan
               :padding [0 1]
               :border charm/rounded-border))

(defn update-fn [state msg]
  (cond
    (or (charm/key-match? msg "q")
        (charm/key-match? msg "ctrl+c"))
    [state charm/quit-cmd]

    (or (charm/key-match? msg "k")
        (charm/key-match? msg :up))
    [(update state :count inc) nil]

    (or (charm/key-match? msg "j")
        (charm/key-match? msg :down))
    [(update state :count dec) nil]

    :else
    [state nil]))

(defn view [state]
  (str (charm/render title-style "Counter App") "\n\n"
       (charm/render count-style (str (:count state))) "\n\n"
       "j/k or arrows to change\n"
       "q to quit"))

(charm/run {:init {:count 0}
            :update update-fn
            :view view
            :alt-screen true})

More examples can be found here.

Deftype with map interfaces

Until now, deftype in babashka couldn't implement JVM interfaces like IPersistentMap, ILookup, or Associative. This meant libraries that define custom map-like types, a very common Clojure pattern, couldn't work in babashka.

Starting with this release, deftype supports map interfaces. Your deftype must declare IPersistentMap to signal that you want a full map type. Other map-related interfaces like ILookup, Associative, Counted, Seqable, and Iterable are accepted freely since the underlying class already implements them.

This unlocks several libraries that were previously incompatible:

• core.cache: all cache types (BasicCache, FIFOCache, LRUCache, TTLCache, LUCache) work unmodified
• linked: insertion-ordered maps and sets

Riddley and Cloverage compatibility

Riddley is a Clojure library for code walking that many other libraries depend on. Previously, SCI's deftype and case did not macroexpand to the same special forms as JVM Clojure, which broke riddley's walker. Several changes now align SCI's behavior with Clojure: deftype macroexpands to deftype*, case to case*, and macroexpand-1 now accepts an optional env map as second argument (inspired by how the CLJS analyzer API works). Together these changes enable riddley and tools built on it, like cloverage and Specter, to work with bb.

Riddley has moved to clj-commons, thanks to Zach Tellman for transferring it. I'd like to thank Zach for all his contributions to the Clojure community over the years. Version 0.2.2 includes bb compatibility, which was one of the first PRs merged after the transfer. Cloverage compatibility has been submitted upstream, all 75 cloverage tests pass on both JVM and babashka.

Console REPL improvements

The bb repl experience has been significantly improved with JLine3 integration. You no longer need rlwrap to get a comfortable console REPL:

• Multi-line editing: the REPL detects incomplete forms and continues reading on the next line with a #_=> continuation prompt
• Tab completion: Clojure-aware completions powered by SCI, including keywords (:foo, ::foo, ::alias/foo)

• Ghost text: as you type, the common completion prefix appears as faint inline text after the cursor. Press TAB to accept.

• Eldoc: automatic argument help — when your cursor is inside a function call like (map |), the arglists are displayed below the prompt
• Doc-at-point: press Ctrl+X Ctrl+D to show full documentation for the symbol at the cursor
• Persistent history: command history saved across sessions in ~/.bb_repl_history
• Ctrl+C handling: first press on an empty prompt warns, second press exits

Many of these features were inspired by rebel-readline, Leiningen's REPL, and Node.js's REPL.

SCI improvements

Under the hood, SCI (the interpreter powering babashka) received many improvements in this cycle:

• Functional interface adaptation for instance targets: you can now write (let [^Predicate p even?] (.test p 42)) and SCI will adapt the Clojure function to the functional interface automatically.
• Type tag inference: SCI now infers type tags from let binding values to binding names, reducing the need for explicit type hints in interop-heavy code.
• Several bug fixes: read with nil/false as eof-value, letfn with duplicate function names, ns-map not reflecting shadowed vars, NPE in resolve, and .method on class objects routing incorrectly.

Other improvements

• Support multiple catch clauses in combination with ^:sci/error
• Fix satisfies? on protocols with proxy
• Support reify with java.time.temporal.TemporalQuery
• Fix reify with methods returning int/short/byte/float primitives
• nREPL server now uses non-daemon threads so the process stays alive without @(promise)
• Add clojure.test.junit as built-in source namespace
• Add cp437 (IBM437) charset support in native binary via selective GraalVM charset Feature, avoiding the ~5MB binary size increase from AddAllCharsets. More charsets can be added on request.

For the full list of changes including new Java classes and library bumps, see the changelog.

Thanks

Thank you to all the contributors who helped make this release possible. Special thanks to everyone who reported issues, tested pre-release builds from babashka-dev-builds, and provided feedback.

Thanks to Clojurists Together and all babashka sponsors and contributors for their ongoing support. Your sponsorship makes it possible to keep developing babashka.

And thanks to all babashka users: you make this project what it is. Happy scripting!

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.

Clojurists Together: long term funding

I'm happy to announce that I'm among the 5 developers that were granted Long term support for 2026. Thanks to all who voted! Read the announcement 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: