koi.

A professional text editor for Mac.

Download for Mac Pricing

v0.1.0-b217 (alpha) · Apple Silicon · macOS 13.2+ · Changelog

Fast

Responsive editing, from small files to millions of lines.

See the benchmarks →

Local

Your files, configuration, and tools stay under your control.

Scriptable

Automate repetitive work with Python and editor commands.

koi.py

 22960   # EditorContainer : _on_tab_label_clicked
 22961   @func_trace
 22962  def _on_tab_label_clicked(self):
 22963       editor = ensure_not_deleted(self.main_editor.editor)
 22964      if editor is not None:
 22965           safe_focus(editor)
 22966  
 22967   # EditorContainer : _on_tab_label_toggle
 22968   @func_trace
 22969  def _on_tab_label_toggle(self):
 22970       window = ensure_not_deleted(self.window)
 22971      if window is None:
 22972           return
 22973  
 22974       buffer = self.buffer
 22975      if buffer is None:
 22976           return
 22977  
 22978       window.buffer_manager.toggle_active(buffer)
 22979  
 22980   # EditorContainer : _on_tab_label_exclusive
 22981   @func_trace
 22982  def _on_tab_label_exclusive(self):
 22983       window = ensure_not_deleted(self.window)
 22984      if window is None:
 22985           return
 22986  
 22987       buffer = self.buffer
 22988      if buffer is None:
 22989           return
 22990  
 22991       window.buffer_manager.set_as_active_tab(buffer)
 22992  
 22993   # EditorContainer : _file_changed
 22994   @func_trace
 22995  def _file_changed(self, *_): [97 lines folded]
 23093  
 23094   # EditorContainer : _do_after_file_changed
 23095   @func_trace
 23096  def _do_after_file_changed(self): [5 lines folded]

 10373       directory = os.path.dirname(path) or "."
 10374       tmp_path = None
 10375  
 10376       os.makedirs(directory, exist_ok=True)
 10377  
 10378       fd, tmp_path = tempfile.mkstemp(dir=directory, prefix=".tmp_")
 10379  
 10380      try:
 10381          with os.fdopen(fd, "w", encoding="utf-8") as f:
 10382               f.write(text)
 10383               f.flush()
 10384               os.fsync(f.fileno())
 10385  
 10386           os.replace(tmp_path, path)
 10387           tmp_path = None
 10388  
 10389      finally:
 10390          if tmp_path is not None:
 10391              try:
 10392                   os.remove(tmp_path)
 10393              except OSError:
 10394                   pass
 10395  
 10396   # CodeEditor : _save_file
 10397   # @func_trace
 10398  def _save_file(self): [113 lines folded]
 10512  
 10513   # CodeEditor : _save_shadow_file
 10514   @func_trace
 10515  def _save_shadow_file(self): [18 lines folded]
 10534  
 10535   # CodeEditor : save_file_as
 10536   @plugin_api
 10537   @command("Save file as...")
 10538  def save_file_as(self): [20 lines folded]
 10559  
 10560   # CodeEditor : save_file_copy_as
 10561   @plugin_api
 10562   @command("Save copy of file as...")
 10563  def save_file_copy_as(self): [20 lines folded]

~/Desktop/koi-editor koi.py indexer.py todo.org Line 22,974, Column 29 Python

Get started

Everything included out of the box.

Flexible workspaces

Split, detach, and open the same document in multiple views.

Multiple views, single document Tab multi-select

Local-first AI

Connect directly to Ollama. Run code completion and chat locally on your Mac.

Code completion Local AI development

Context-aware autocomplete

Complete words from the current file, with suggestions ranked by nearby context and usage.

Context-aware autocomplete

Python scripting

Add editor commands without a plugin framework. Show all commands with ⌘⇧P, also your own.

API docs

Inline commands

Run shell commands directly from the document with ⌘⇧⏎. Use % for shell, > for chat, or evaluate Python directly.

Inline chat In-code shell and Python eval

Settings are plain text

Configuration and key bindings stay readable and editable.

See default config file →

Built-in language support

Support for 30+ programming languages out of the box, with more planned.

Roadmap →

Find anything

Go to any file with ⌘P, search everywhere with ⌘⇧F.

A text editor, built deliberately.

Fast

Koi is built around a native C++ editing core, with responsiveness treated as a constraint rather than an optimization added later.

Editing stays responsive as files grow, with multiple views of the same document sharing a single underlying buffer.

Performance is measured on real source files and published with reproducible benchmarks.

CLexer.cpp

  172   bool isFunctionLike = false;
  173  
  174   // keywords
  175  if (keywords.InList(s)) {
  176       sc.ChangeState(SCE_HACK_KEYWORD);
  177   }
  178   // types
  179  else if (types.InList(s)) {
  180       sc.ChangeState(SCE_HACK_TYPE);
  181   }
  182   // constants
  183  else if (constants.InList(s)) {
  184       sc.ChangeState(SCE_HACK_CONSTANT);
  185   }
  186   // builtins
  187  else if (builtins.InList(s)) {
  188       sc.ChangeState(SCE_HACK_BUILTIN);
  189   }
  190  else {
  191       const Sci_Position line = styler.GetLine(sc.currentPos);
  192       const Sci_PositionU lineEnd = styler.LineEnd(line);
  193       Sci_PositionU pos = sc.currentPos>;
  194  
  195      while (pos < lineEnd) {
  196           const unsigned char c = styler.SafeGetCharAt(pos);
  197          if (c == ' ' || c == '\t') {
  198               ++pos;
  199               continue;
  200           }
  201           isFunctionLike = (c == '(');
  202           break;
  203       }

  267   // enter new state
  268  
  269  if (sc.state == SCE_HACK_DEFAULT) {
  270       // numbers
  271      if (IsADigit(sc.ch) || (sc.ch == '.' && IsADigit(sc.chNext))) {
  272           sc.SetState(SCE_HACK_NUMBER);
  273       }
  274       // identifiers
  275      else if (!sc.atLineEnd && (setWordStart.Contains(sc.ch) || (sc.ch == '@'))) {
  276           sc.SetState(State_Identifier);
  277       }
  278       // block comment
  279      else if (sc.Match('/', '*')) {
  280           sc.SetState(State_BlockComment);
  281           sc.Forward();
  282       }
  283       // line comments
  284      else if (sc.Match('/', '/')) {
  285           sc.SetState(State_LineComment);
  286       }
  287       // strings
  288      else if (sc.ch == '\"') {
  289           sc.SetState(SCE_HACK_STRING);
  290           isIncludePreprocessor = false;
  291       }
  292       // includes
  293      else if (isIncludePreprocessor && sc.ch == '<') {
  294           sc.SetState(SCE_HACK_STRING);
  295       }
  296       // characters
  297      else if (sc.ch == '\'') {
  298           sc.SetState(State_Character);

~/hackerman/lexers CLexer.cpp clexer.sip Line 199, Column 22 C

Ultra low-latency typing

16.6 ms P95 typing latency on a 753,821-line source file. Fastest of all compared editors.

Benchmarks →

Multiple views, one document

Work in multiple views of the same document without sacrificing editing responsiveness.

Multiple views →

Handles very large files

Edit syntax-highlighted files with millions of lines smoothly and responsively.

Large file performance →

Measured, not claimed

16.6 ms

P95 typing latency on a 753,821-line source file.

20M lines

Largest syntax-highlighted file tested.

698 MB

Memory usage at 5 million lines source file.

Benchmarks →

Local

Useful features without sending your code somewhere else. Koi works directly with local files, local indexes, and local models.

Context-aware autocomplete is built from the current file, without requiring a language server. AI features run locally through Ollama and are disabled by default.

Your files stay on your machine, and the editor remains fully functional offline.

dsl.py

  15   types
  16       int
  17       float
  18   arguments
  19       out     : stdin to use previous output as input
  20               : stdout to print
  21   """
  22  
  23   program = """
  24   Module add 1 2 3 type=float out=stdin
  25   Module sub stdin 1 2 type=int out=stdout
  26   """
  27  
  28   # Module definition
  29  class Module:
  30  
  31       # Add function
  32      def add(*args, **kwargs):
  33           type_ = globals()["__builtins__"].getattr(globals()["__builtins__"], kwargs["type"])
  34           return sum(map(type_, args))
  35  
  36       # Sub function
  37      def sub(*args, **kwargs):
  38           type_ = globals()["__builtins__"].getattr(globals()["__builtins__"], kwargs["type"])
  39           return float(args[0]) if type_ == 'float' else int(args[0]) - sum(map(type_, args[1:]))
  40  
  41  def get_args(tokens, STDIN): [18 lines folded]
  60  
  61  def interpret(program): [25 lines folded]
  87  
  88   interpret(program) # 3
  89

~/Desktop qwen2.5-coder:1.5b Line 34, Column 9 C

Context-aware autocomplete

Complete words from the current file, ranked by nearby context and usage.

Context-aware autocomplete →

Local-first AI

Run inline chat and code completion locally with your own models through Ollama.

Local AI →

No telemetry

No accounts, usage tracking, or analytics. Koi works fully offline with your files.

Privacy by design

No telemetry or tracking. No background downloads. Not even an auto-updater.

Offline mode not required.

Scriptable

Koi exposes editor commands to Python, so repetitive work can become part of the editor instead of another plugin or external tool.

Write ordinary Python functions, expose them as commands, assign keybindings, and use them just like the editor's built-in commands.

Inline commands bring the same idea into the document: run shell commands, evaluate Python, or use AI without leaving the editor.

Untitled

   1   % git log --oneline -5
   2   7e43c91 Fix stale index results after file changes
   3   20b9ad4 Add PHP symbols to file outline
   4   e3816fc Preserve cursor position when reopening files
   5   9ad0c72 Reduce allocations while indexing large files
   6   615bc84 Fix split view restoring the wrong document
   7  
   8   > Summarize these changes for the changelog.
   9  
  10   ## Editor
  11  
  12   - Added PHP symbols to the file outline.
  13   - Cursor position is now preserved when reopening files.
  14   - Fixed split views occasionally restoring the wrong document.
  15  
  16   ## Performance and reliability
  17  
  18   - Reduced memory allocations while indexing large files.
  19   - Fixed stale autocomplete results after files changed on disk.
  20  
  21   % screenfetch -N
  22  
  23                    -/+:.          michael@Michaels-Mac-mini
  24                   :++++.          OS: 64bit macOS  
  25                  /+++/.           Kernel: arm64 Darwin 24.6.0
  26          .:-::- .+/:-``.::-       Uptime: 2d 3h 24m
  27       .:/++++++/::::/++++++/:`    Packages: 76
  28     .:///////////////////////:`   Shell: zsh 5.9
  29     ////////////////////////`     Resolution: 3440x1440 
  30    -+++++++++++++++++++++++`      DE: Aqua
  31    /++++++++++++++++++++++/       WM: Quartz Compositor
  32    /sssssssssssssssssssssss.      WM Theme: Graphite (Dark)

   1  
   2   # This is the default scripts-file for Koi Editor
   3  
   4   @command("Word count")
   5  def word_count():
   6       import re
   7  
   8       text = selected_text()
   9       count = len(re.findall(r"\b[\w'-]+\b", text))
  10  
  11       message (f"Word count: {count:,} words")
  12  
  13   @command("Insert UUID")
  14  def insert_uuid(): [2 lines folded]
  17  
  18   @command("Markdown: Selection to link")
  19  def insert_link(): [2 lines folded]
  22   
  23   @command("Markdown: Insert unchecked box")
  24  def insert_unchecked_box(): [1 lines folded]
  26   
  27   @command("Markdown: Wrap selection in fenced block")
  28  def fenced_block(): [2 lines folded]
  31  
  32   @command("Markdown: Bold")
  33  def make_bold():
  34       text = selected_text()
  35       insert_text(text=f"**{text}**")
  36  
  37   
  38   
  39

~/koi-editor _ .hackerman-scripts glm-5.3-flash:cloud Generic-Default

Python scripting

Write editor commands as ordinary Python functions and bind them to keys or run them from the command palette.

Explore the API →

Inline commands

Run shell commands with %, inline chat with >, or evaluate Python directly from the document.

Shell and Python eval →

Plain-text configuration

Configure settings, keybindings, models, and editor behavior in files you can inspect, edit, and version.

Documentation →

Reasons to use Koi

Zero-latency typing

Koi maintains a measured P95 typing latency of 17.86 ms while editing a 1 million-line Odin source file with syntax highlighting enabled.

Local AI, on your Mac

Koi works directly with local Ollama models, with no account, telemetry, or cloud intermediary. Use local code completion and inline AI while keeping your code and inference on your Mac.

Native macOS code editors

A look at code editors built specifically for macOS, from long-running editors like BBEdit and TextMate to newer alternatives like Nova, CodeEdit, and Koi.

Note taking and organization

Keep notes as ordinary Markdown, plain text, Org Mode, or other files. Open directly into your notes folder, search with ripgrep, and organize everything without a proprietary database.

Roadmap

What we're currently working on and have planned.

Changelog

Submit feature request →

Writer mode with focused interface

Variable fonts and wikilinks

File preview in file explorer

Faster search in very large files

One command palette for all dialogs

Hand-tuned native lexers for fast, precise syntax highlighting.

Code folding is syntax-aware, allowing for language-specific behavior.

Some languages have file outline support, enabling navigation through the code via symbols.

Asm

Bash

CSS

Clojure

C++

Diff

Elixir

Fortran

Gleam

Haskell

HTML

Jai

Java

JavaScript

Julia

JSON

LaTeX

Lua

Makefile

Markdown

MATLAB

Mojo

Nim

OCaml

Odin

Org

Pascal

Perl

PHP

Python

Ruby

Rust

SQL

Swift

TOML

TypeScript

Typst

WAT

YAML

Zig

Built-in language support

Hand-tuned native lexers for fast, precise syntax highlighting.

Minimal syntax highlighting for better performance. The lexers are written in C++ and optimized for speed.

Code folding is syntax-aware, allowing for language-specific behavior.

Some languages have file outline support, enabling navigation through the code via symbols.

Asm

Bash

CSS

Clojure

C++

Diff

Elixir

Fortran

Gleam

Haskell

HTML

Jai

Java

JavaScript

Julia

JSON

LaTeX

Lua

Makefile

Markdown

MATLAB

Mojo

Nim

OCaml

Odin

Org

Pascal

Perl

PHP

Python

Ruby

Rust

SQL

Swift

TOML

TypeScript

Typst

WAT

YAML

Zig

Pricing

Non-Commercial

Free

Personal projects, learning, and other non-commercial use.

Download

Personal Early bird offer

$195 ~~$325~~

One-time payment, lifetime license

Single user (You)

Unlimited machines

Commercial use

Buy once, own forever

Buy personal

Business

$19,995 /year

No per-seat management

Unlimited users

Unlimited machines per user

Limited custom builds

Pay by invoice

Buy for business

Licensing FAQ.

Free for non-commercial use. Commercial use requires a license.

End User License Agreement

License recovery →

Why should I buy a license?

Koi Editor is free for non-commercial use. If you use it for work, a commercial license is required. That is how development is funded.

What is non-commercial use?

Non-commercial use includes learning, personal projects, hobby use, and evaluation. If you use Koi Editor for paid work, company work, client work, or any other commercial activity, a commercial use license is required.

Which license is right for me?

The Personal license is for one individual user. Business license is for organizations and multi-user use.

Working alone and using it professionally → Personal

Covering a larger organization with one license → Business

Can I use my Personal license at work?

Yes. A Personal license can be used for commercial work if you are the only person using the software. For multi-user use, choose Business.

I lost my license file, where can I get a new one?

You can recover your license file on License recovery →, using your Session ID displayed to you after purchase.

We can also help you recover your license, send an email to koi@hackerman.ai and include any information relevant to your purchase, such as email, name, business name, approximate date and time.

Latest from Koi

Debugging race condition that was actually a lifetime bug

A random QThread crash looked like a race condition, but turned out to be an orphaned editor buffer and delayed garbage collection.

Next steps for navigation

Rethinking editor navigation around lightweight histories, on-demand search, and local structure.

Redesigning the title bar

Moving from a custom title bar to native AppKit, and figuring out what to do with tabs along the way.

Try Koi on your own code.

Free for non-commercial use. Requires macOS on Apple Silicon.

Download Koi for Mac Pricing