p(air) prog(rammer)

pprog is an LLM based pair programmer for generating and editing code in individual projects

prereqs

• Rust (cargo)
• Browser
• git

To install Rust, go to their website.

install

cargo install pprog

usage

To use pprog, cd into the directory of an existing or template project. pprog depends on git and also uses .gitignore to communicate the available files to LLM, so the project must have git initialized. For this example, we'll create a basic NodeJS project.

mkdir example-project
cd example-project
npm init -y && git init
pprog init

This will generate a config file pprog.toml with sensible defaults depending on the type of project. For this example the pprog.toml will contain

model = "claude-3-5-sonnet-latest"
check_cmd = "node index.js"
base_url = "https://api.anthropic.com/v1"
api_key = "..." // if ANTHROPIC_API_KEY env var is set then it will automatically add it

The program that generates and edits code in the backend uses the check_cmd to check compilation or successful operation. In this case node index.js will be run to check for any errors in code changes and then loop to fix these changes if they exist. For compiled projects using a langauge like Rust, check_cmd would be "cargo check". An Anthropic account is assumed on init, but OpenAI-compatible APIs can be used as well. For example, to use DeepSeek you can change config to

model = "deepseek-chat"
check_cmd = "node index.js"
base_url = "https://api.deepseek.com/v1"
api_key = "<DEEPSEEK API KEY>"

With config set, to start the server run

pprog serve

and then enter http://localhost:8080 in your browser. A chat interface will load and you can begin making changes to your code. For example, in this example project you can type in a message like Create an index.js file with basic express server and it will create file and check that it runs properly by using check_cmd command. Then another message like Add GET /ping endpoint and it will make changes to the code and check again. You may also questions about the code or anything in general.

You can run pprog serve for multiple projects at the same time by assigning different ports

pprog serve --port 3002

tools

pprog uses a very small set of tools to make changes. currently it has four.

read_file - read entire file contents
write_file - replace entire file with contents
execute - run general bash, sometimes used by agent to install packages when check fails
compile_check - check for compilation errors, or for interpreted programs checks runtime errors on startup

tips and warnings

• This is experimental and unstable code, it may change at any time.
• The system prompt includes instructions to not change any files outside of the root of the project but this is not strictly guaranteed. Proceed with caution!
• If using Anthropic/OpenAI models it can get expensive, but is usually very effective. When using Sonnet 3.5 a single code change request routinely cost 0.20 USD or more. This is because the program is constantly reading/writing entire files to satisfy each request. I shudder to use Opus and haven't even tried. Haiku 3.5 seems to be a good trade-off, usually costing a few cents per change of a medium sized project. I normally use Haiku. DeepSeek is dirt cheap but doesn't seem as effective. OpenAI models can be effective, but usually get throttled by rate limits almost immediately.
• Make sure to commit and push changes frequently. It's ok to sometimes make multiple changes before committing but if it's going to be a large change then best to commit before making them.
• The system prompt notes that the user may ask questions and the model is usually good at figuring out when a question without needed code changes is asked, but I usually prepend question messages with 'Question: ' to make sure
• Sometimes the model does not correctly identify that compilation failed, just ask it to rerun.
• You'll still have to do some coding

happy hacking!