ctxkit

ctxkit is a command-line tool for creating AI prompts to modify code. It works as follows:

• construct an AI prompt containing files, directories, and URL content

• calls an API to generate the prompt response

• extract modified or newly-created files in-place

In the following example, the project's Python source code is included (-d src -x py), then a change request message (-m), then call the xAI API (--api grok), and finally extract the modified project files (--extract):

ctxkit -d src -x py -m 'Please add -q argument' --api grok grok-4-fast-reasoning --extract

Installation

To install ctxkit, enter the following commands in a terminal window:

macOS and Linux

python3 -m venv $HOME/venv --upgrade-deps
. $HOME/venv/bin/activate
pip install ctxkit

Windows

python3 -m venv %USERPROFILE%\venv --upgrade-deps
%USERPROFILE%\venv\Scripts\activate
pip install ctxkit

Calling APIs

ctxkit supports the following APIs:

claude - Claude (Anthropic) API

export ANTHROPIC_API_KEY=<key>
ctxkit -m 'Hello!' --api claude claude-3-5-haiku-latest

gemini - Gemini (Google) API

export GOOGLE_API_KEY=<key>
ctxkit -m 'Hello!' --api gemini gemini-2.0-flash-exp

gpt - ChatGPT (OpenAI) API

export OPENAI_API_KEY=<key>
ctxkit -m 'Hello!' --api gpt model-name

grok - Grok (xAI) API

export XAI_API_KEY=<key>
ctxkit -m 'Hello!' --api grok grok-3

ollama - Ollama API

ctxkit -m 'Hello!' --api ollama gpt-oss:20b

List Models

Use the --list argument to list an API's models. For example:

ctxkit --list claude

Prompt from stdin

You can call an API with a prompt from stdin by passing no prompt items:

echo 'Hello!' | ctxkit --api ollama gpt-oss:20b

Extract Response Files

When a prompt includes one or more files, the AI may respond with modified versions of the files. You can extract the modified files using the -e (or --extract) argument:

ctxkit -d src -x py -m "Add a -q argument to silence output" --api grok grok-4-fast-reasoning --extract

In this example, ctxkit passes a prompt with all of the project source and a change request, to which we expect the AI to respond with modified versions of some project files that satisfy the requested change. Magic!

Use the --diff argument in conjunction with -e to return modified files as unified diffs. This can significantly speed-up file modifications.

Inline Instructions

The AI processes inline instructions within the included files. These are lines or comments that begin with ctxkit: followed by instructions. For example:

def calculate_total(items):
    # ctxkit: add a docstring
    return sum(total)

Files containing the inline instructions are modified per the instructions and the inline instructions removed. Note that only instructions prefixed with ctxkit: are processed - instructions intended for others (e.g. user:) are ignored.

Variables

You can specify one or more variable references in a message's text, a file path, a directory path, or a URL using the syntax, {{var}}. A variable's value is specified using the -v argument. For example:

ctxkit -v package ctxkit -m 'Write brief overview of the Python package, "{{package}}"'

Configuration Files

ctxkit JSON configuration files allow you to construct complex prompts in one or more JSON files.

Example: Write Unit Tests

To generate a prompt to write unit tests for a function or method in a module, create a configuration file similar to the following:

{
    "items": [
        {"message": "Write the unit test methods to cover the code in the {{scope}}."},
        {"file": "src/my_package/{{base}}.py"},
        {"file": "src/tests/test_{{base}}.py"}
    ]
}

In this example, the "scope" variable allows you to specify what you want to write unit tests for. The "base" variable specifies the base sub-module name. To generate the prompt, run ctxkit:

ctxkit -v base main -v scope "main function" -c unittest.json

This outputs:

<system>
...
</system>

Write the unit test methods to cover the code in the main function.

<src/my_package/main.py>
# main.py
</src/my_package/main.py>

<src/tests/test_main.py>
# test_main.py
</src/tests/test_main.py>

Copy Output

To copy the output of ctxkit and paste it into your favorite AI chat application, pipe ctxkit's output into the clipboard tool for your platform.

macOS

ctxkit -m 'Hello!' | pbcopy

Windows

ctxkit -m 'Hello!' | clip

Linux

ctxkit -m 'Hello!' | xsel -ib

Usage

Using the ctxkit command line application, you can add any number of ordered context items of the following types: configuration files (-c), messages (-m), file path or URL content (-i and -f), and directories (-d).

The CTXKIT_FLAGS environment variable is used to define default arguments, such as --api grok grok-4-fast-reasoning to set a default model. CTXKIT_FLAGS is prepended to the command-line arguments.

usage: ctxkit [-h] [-g] [-e] [--diff] [-o PATH] [-b] [-c PATH] [-m TEXT]
              [-i PATH] [-t PATH] [-f PATH] [-d PATH] [-v VAR EXPR] [-s PATH]
              [-x EXT] [-l INT] [--api API MODEL] [--list API] [--temp NUM]
              [--topp NUM] [--maxtok NUM] [--noapi]

options:
  -h, --help           show this help message and exit
  -g, --config-help    display the JSON configuration file format

Output Options:
  -e, --extract        extract response files
  --diff               use unified diff format for file changes
  -o, --output PATH    output to the file path
  -b, --backup         backup output files with ".bak" extension

Prompt Items:
  -c, --config PATH    process the JSON configuration file path or URL
  -m, --message TEXT   add a prompt message
  -i, --include PATH   add the file path or URL text
  -t, --template PATH  add the file path or URL template text
  -f, --file PATH      add the file path or URL as a text file
  -d, --dir PATH       add a directory's text files
  -v, --var VAR EXPR   define a variable (reference with "{{var}}")
  -s, --system PATH    the system prompt file path or URL, "" for none

Directory Options:
  -x, --ext EXT        add a directory text file extension
  -l, --depth INT      the maximum directory depth, default is 0 (infinite)

API Calling:
  --api API MODEL      pass to an API provider (see "API Providers")
  --list API           list API provider models (see "API Providers")
  --temp NUM           set the model response temperature
  --topp NUM           set the model response top_p
  --maxtok NUM         set the model response max tokens
  --noapi              do not pass to an API provider

API Providers:
  claude - Claude (Anthropic) API
  gemini - Gemini (Google) API
  gpt    - ChatGPT (OpenAI) API
  grok   - Grok (xAI) API
  ollama - Ollama API

Examples:
  ctxkit --api ollama qwen3.6:35b -m "How do I count code lines?"
  ctxkit --api grok grok-4.3 -f README.md -f main.py -f test_main.py -m "Add a -q argument" -e
  ctxkit --api claude claude-opus-4-7 -f README.md -d src -x py -i spec.txt -e
  ctxkit --list grok

Configuration File Format

The ctxkit -g argument outputs the JSON configuration file format defined using the Schema Markdown Language.

# The ctxkit configuration file format
struct CtxKitConfig

    # The list of prompt items
    CtxKitItem[len > 0] items


# A prompt item
union CtxKitItem

    # Config file path or URL
    string config

    # A prompt message
    string message

    # A long prompt message
    string[len > 0] long

    # File path or URL text
    string include

    # File path or URL template text
    string template

    # File path or URL as a text file
    string file

    # Add a directory's text files
    CtxKitDir dir

    # Set a variable (reference with "{{var}}")
    CtxKitVariable var


# A directory item
struct CtxKitDir

    # The directory file path or URL
    string path

    # The file extensions to include (e.g. ".py")
    string[] exts

    # The directory traversal depth (default is 0, infinite)
    optional int(>= 0) depth


# A variable definition item
struct CtxKitVariable

    # The variable's name
    string name

    # The variable's value
    string value

Development

This package is developed using python-build. It was started using python-template as follows:

template-specialize python-template/template/ ctxkit/ -k package ctxkit -k name 'Craig A. Hobbs' -k email 'craigahobbs@gmail.com' -k github 'craigahobbs' -k noapi 1